微型化微波元件之研製---使用左手傳輸線及低溫共燒陶瓷技術

行政院國家科學委員會專題研究計畫 成果報告

微型化微波元件之研製—使用左手傳輸線及低溫共燒陶瓷 技術(重點研究計畫)

研究成果報告(精簡版)

計 畫 類 別 ： 個別型

計 畫 編 號 ： NSC 95-2218-E-011-022-

執 行 期 間 ： 95 年 11 月 01 日至 96 年 10 月 31 日 執 行 單 位 ： 國立臺灣科技大學電子工程系

計 畫 主 持 人 ： 曾昭雄

計畫參與人員： 碩士班研究生-兼任助理：張智林、陳明宏、陳相如

報 告 附 件 ： 出席國際會議研究心得報告及發表論文

處 理 方 式 ： 本計畫涉及專利或其他智慧財產權，2 年後可公開查詢

中 華 民 國 97 年 01 月 29 日

計畫編號 NSC 95-2218-E-011-022 執行期限：95 年 11 月 1 日至 96 年 10 月 31 日

計畫主持人：曾昭雄 助理教授 國立台灣科技大學 電子工程系 計畫參與人員：張智林、陳明宏、陳相如

中文摘要

本研究計畫之主要目的係利用左手傳輸線及低溫共燒陶 瓷製程技術，研製適用於系統封裝之微型化微波元件。使用 左手傳輸線，主要係因該傳輸線之相位響應可任意合成，並 可用來設計微型化元件。使用低溫共燒陶瓷技術，主要係可 將平面微波電路或元件，使用層積結構實現，以縮小電路面 積，並可提供系統封裝之整合設計方案。本計畫則整合兩種 新式技術，研製適合射頻前級模組及系統封裝設計用之三維 微型化元件，並已完成二型微型化環形耦合器(ring coupler)之 研製。此外，利用左手傳輸線之可任意合成相位響應之特 性，已完成研製具 90度相位差之寬頻功率分配器、寬頻平 衡-非平衡轉換器及平衡式放大器。相較於傳統電路架構，其 電路效能明顯地獲得改善。

關鍵字：微波元件、微波電路、低溫共燒陶瓷、左手 傳輸線

Abstract

The aim of this research program is to use left-handed transmission lines (LH TL) and low-temperature co-fired ceramic (LTCC) technique to develop miniaturized microwave devices, which are suitable for the system-on- package (SOP) design. For LH TLs, they can be synthesized with the arbitrary phase response, and then employed to design miniaturized components. For LTCC technique, it can not only realize multilayered components with the smaller circuit size than planar circuits, but provide an integrated solution for the SOP design. In this research program, two novel techniques will be combined to develop three-dimensional miniaturized components for the radio- frequency (RF) front-end and SOP applications. Two types of miniaturized LTCC ring couplers have been developed. In addition, the novel property of arbitrarily synthesizing phase response is exploited to implement quadrature power splitter, balun, and balanced amplifier. Compared with the conventional circuit configuration, using LH TL is an effective approach to improve the circuit performance.

Keywords: Microwave components, microwave circuits, low temperature co-fired ceramic (LTCC), left-handed transmission lines (LH TLs)

一、簡介

本 研 究 計 畫 擬 結 合 左 手 傳 輸 線 (left-handed transmission line, LH TL)及低溫共燒陶瓷(low-temperature co-fired ceramic, LTCC)技術進行研製適用於單一系統封 裝(system-on-package, SOP)之微型化微波元件。該研究 主題具學術研究之新穎性及前瞻性，並可將該技術延展 應 用 於 單 一 系 統 構 裝 之 射 頻 前 級 模 組 (RF front-end module) 研 製 ， 以 提 供 無 線 通 訊 產 業 一 體 積 小 、 重 量 輕、低成本及具高整合度性之射頻模組解決方案。

欲實現微型化射頻電路模組，以現階段技術而言，

「系統封裝技術」為理想之解決方案。在眾多系統封裝 技術中，使用低溫共燒陶瓷(LTCC)之層積結構製程，

進行單一系統封裝之射頻模組研製，為一有效之電路微 型化解決方案，產業界及學術界更是如火如荼的開展該 領域之研發工作。另一方面，近年來微波領域熱門的研 究領域「左/右手合成傳輸線」，亦為另一設計微型化 微波元件之有效方案。此外，左手傳輸線亦被 2003 年 之科學雜誌(Science magzine)選為該年之科學十大突破 之一。本研究計畫擬結合上述兩有效之微型化技術—

LTCC 層積製程及左手傳輸線—研製適用於系統封裝 (SOP)之微型化微波元件。

主要的實現概念為使用 LTCC 製程技術設計嵌入式 電感及電容，並連結成左手傳輸線單元網路，且串接數 單元網路，成為三維微型化左手傳輸線。利用此傳輸線

「可合成正值相位響應」之特性，設計微型化環狀耦合 器(hybrid ring coupler)及平衡-非平衡轉換器(balun)等被 動微波元件。本計畫除了使用 LTCC 技術實現微型化電 路，在計畫執行初期，亦完成研發具 90度相位差之寬 頻功率分配器、寬頻平衡-非平衡轉換器及平衡式放大 器。

二、研究內容及成果

本計畫主要目的為使用低溫共燒陶瓷及左手傳輸線 技術研製微型化微波元件。截至目前為止，已完成二種 新型微型化低溫共燒陶瓷環形耦合器(如圖一所示)。該 電路係委託達「泰科技公司」製作，在製作過程中，不 斷的修正多層電路佈局，以符合製程公司可順利製作之 規格，致使製作時程有所延誤。因此，尚未完成電路量 測工作，本計畫研究成員將繼續完成電路量測，並預計 將 研 究 成 果 撰 寫 成 期 刊 論 文 投 稿 至 IEEE Trans.

Microwave Theory and Techniques。

微型化微波元件之研製使用左手傳輸線及低溫共燒陶瓷技術

此外，在發展多層結構之微型化電路的過程中，亦 研製相關平面電路，以初步驗證使用左手傳輸線設計微 波元件具有改善電路效能之優點。截至目前為止，本計 畫已完成具 90度相位差之寬頻功率分配器(如圖二所 示)、寬頻平衡-非平衡轉換器(如圖三所示)、平衡式放 大 器 (如 圖 四 所 示 )，其研究成果並已獲刊登於 IEEE Microwave Wireless and Components Letters 二篇[1],[2]、

IET Electronic Letters 一 篇 [3] 、 2007 Asia Pacific Microwave Conference 研討會論文一篇[4]及 2007 全國電 信研討會論文一篇[5]，詳細論文全文如附件所示。

圖一、二型微型化低溫共燒陶瓷環形耦合器。

圖二、具 90度相位差之寬頻功率分配器。

圖三、寬頻平衡-非平衡轉換器。

圖四、平衡式放大器。

三、總結

本計畫於執行期間內，完成二型微型化低溫共燒陶 瓷環形耦合器、具 90度相位差之寬頻功率分配器、寬 頻平衡-非平衡轉換器及平衡式放大器。研究成果獲得 刊登之 SCI 期刊論文共計三篇、研討會論文共計二篇，

成果豐碩。此外，透過本計畫之執行，本研究團隊累積 使用左手傳輸線研製微波電路及模組之研發能量。

本計畫為本人獲聘任教於台灣科技大學電子系後，

第一個新進人員計畫。由於本計畫之研究經費支援，得 以順利建立「微波電子研究團隊」。目前本團隊共計有 六名 k 碩士班研究生，專注於前瞻微波電路及模組研 究工作。未來，期待透過本研究團隊之積極及紮實研究 訓練為台灣無線通訊產業培養更多優質碩、博士級研發 人才。

參考文獻

[1] C.-H. Tseng and C.-L. Chang, “A broadband quadrature power splitter using metamaterial transmission line,” IEEE Microw.

Wireless Compon. Lett., vol. 18, no. 1, pp. 25-27, Jan. 2008. (NSC 95-2218-E-011-022)

[2] C.-H. Tseng and C.-L. Chang, “Improvement of return loss bandwidth of balanced amplifier using metamaterial-based quadrature power splitters,”IEEE Microw. Wireless Compon. Lett., to be published in Apr. 2008. (NSC 95-2218-E-011-022, NSC 96- 2221-E-011-009)

[3] C.-H. Tseng and C.-L. Chang, “Wide-band balun using composite right-/left-handed transmission line,”Electronics Lett., vol. 43, no.

21, pp. 1154-1155, Oct. 2007. (NSC 95-2218-E-011-022)

[4] C.-L. Chang and C.-H. Tseng, “Bandwidth-Enhanced Quadrature Power Splitter and Balun Using Metamaterial Transmission Lines,”

in Proc. 19^thAsia-Pacific Microwave Conf., Bangkok, Thailand, Dec.

2007, pp. 2777-2780. (NSC 95-2218-E-011-022)

[5] 張智林, 曾昭雄,“使用左手傳輸線研製具90及180相位差之寬

頻 微 波 功 率 分 配 器 ,” in Proc. National Symp. on Telecommunications, Taipei, Taiwan, Nov. 2007, pp. 762-765. (NSC 95-2218-E-011-022)

IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 18, NO. 1, JANUARY 2008 25

A Broadband Quadrature Power Splitter Using Metamaterial Transmission Line

Chao-Hsiung Tseng, Member, IEEE, and Chih-Lin Chang

Abstract—A broadband quadrature power splitter (QPS) is de-

veloped using the metamaterial transmission line (MM TL). It con- sists of a Wilkinson power divider and two phase-adjusting TLs, namely a MM TL and a microtrip (MS). The slope of the phase-re- sponse curve of the MM TL is synthesized to be the same as that of the MS along with the 90 phase increment at two design frequen- cies. Hence, the broadband quadrature phase difference over the desired frequency range can be obtained. In this letter, the QPS is developed at the center frequency of 2 GHz. Over the frequency range of 1.1–3.5 GHz, an amplitude imbalance of less than 0.9 dB and a phase error of less than 5 have been experimentally demonstrated.

Index Terms—Broadband, metamaterials (MMs), microwave

devices, power dividers, quadrature power splitters (QPSs).

I. I

Q ^{UADRATURE are key components power to splitters realize balanced (QPSs) [1]–[4] ampli-}

fiers, image-rejection mixers, and linear vector modulators. They can be implemented by a power divider together with a phase-adjusting circuit to provide a balanced magnitude with 90 phase difference and good isolation between two output ports. The 90 hybrid coupler also has the same output characteristics as the QPS, however, it needs to terminate the isolation port for some applications [5], and has more challenges to achieve the broadband performance.

The phase-adjusting circuit adapted in the QPS can be im- plemented by high-pass and low-pass filters [1], all-pass active filters [3], or phase compensated transmission lines [2]. In addi- tion, since the metamaterial transmission line (MM TL) has the ability to synthesize an arbitrary phase response, it provides an- other approach to realize the phase-adjusting circuit [4]. Based on the phase synthesis capability of the MM TL, it finds applica- tions in the realizations of couplers [6], filters [7], phase shifters [8], baluns [9], and transitions [10].

In this letter, a broadband QPS shown in Fig. 1(a) is developed using the MM TLs. It consists of a Wilkinson power divider, a conventional microstrip, and a MM TL. The Wilkinson power divider equally separates the input power into two output ports, and also provides good isolation between them. The conven- tional microstrip and MM TL are connected to two output ports of the divider as a phase adjusting circuit to achieve broadband quadrature phase difference.

Manuscript received June 14, 2007; revised August 9, 2007. This work was supported by the National Science Council of Taiwan, R.O.C., under Grant NSC 95-2218-E-011-022.

The authors are with the Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106, R.O.C.

(e-mail: [email protected]).

Digital Object Identifier 10.1109/LMWC.2007.911981

Fig. 1. (a) Configuration of the broadband quadrature power splitter and (b) the phase responses of the MM TL and microstrip.

Fig. 1(b) shows the phase responses of the MM TL and mi- crostrip. Referring to the microstrip, the phase response of the MM TL is synthesized to have the 90 phase increment at and , and achieve the same slope of the phase-response curve as that of the MS. Although a similar design concept has been employed to implement the QPS [4] and the microstrip-to-CPS transition [10], the lack of well-developed design procedures leads to the limitation of the relative operating bandwidth. The design procedures developed in this letter improve the relative bandwidth of the QPS, while the effectiveness is demonstrated by the experimental results.

II. C

D

To implement the broadband QPS shown in Fig. 1(a) over the frequency range from to , the Wilkinson power divider is first designed at the center frequency [11]. Followed by properly choosing the length of the conventional microstrip line, the simulated phase responses and can be

1531-1309/$25.00 © 2007 IEEE

26 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 18, NO. 1, JANUARY 2008

determined. Hence, the phase responses of the MM TL at and can be expressed as

(1) (2) Since the MM TL shown in Fig. 1(a) consists of the left-handed (LH) section and the right-handed (RH) microstrip, the phase responses of the MM TL can be represented as [6], [7]

(3)

(4) where and . The component values

and in the LH section relate to the value by

(5) where is the number of the cascaded LH sections.

After solving the simultaneous equations (3) and (4), and are given as

(6) (7) The design procedures of the broadband QPS are summarized as follows.

1) Design the Wilkinson power divider at .

2) Designate the frequency range, namely giving and , and then determined and by (1) and (2).

3) Calculate and by substituting , and into (6) and (7).

4) Utilize to obtain , namely the length of the RH mi- crostrip.

5) Use (5) and to solve the values of and in the LH section.

III. I

R

The broadband QPS is realized using the circuit configuration shown in Fig. 1(a). The frequencies , and are, respec- tively, chosen as 2 GHz, 1.2 GHz, and 2.8 GHz to achieve a 80% design bandwidth. The FR 4 substrate with 1.5-mm thick- ness and the dielectric constant of 4.3 is employed to fabricate the developed QPS. In addition, the LH section in the MM TL is realized by Murata 0603 (1.6 mm 0.8 mm) chip inductors and capacitors.

Based on the design procedures in Section II, the circuit is im- plemented as shown in Fig. 2, and its dimension parameters are indicated as well. As depicted in the inset of Fig. 2, the LH sec- tion is cascaded by two T-networks with 12.1 nH (cascaded by 3.9 nH and 8.2 nH inductors) and 5 pF. Two 50 -bends are connected with two outputs of the QPS for the convenience

Fig. 2. Photograph of the developed broadband QPS.

Fig. 3. Measured results of reflection coefficients and isolation performance.

to measure the isolation parameter . The measured results in this letter are carried out by the Anritsu 37347C vector network analyzer.

Fig. 3 shows the measured results of the reflection coeffi- cients at each port and the isolation between two output ports.

All the , and are better than 10 dB from 0.85 to 3.46 GHz, while the isolation is larger than 10 dB from 0.9 to 3.3 GHz. The measured transmission coefficients and am- plitude imbalance between two output ports are illustrated in Fig. 4. The maximum output imbalance, namely , is about 0.9 dB from 0.5 to 3.5 GHz. It demonstrates that the LH section realized by chip components does not lead to the signif- icant degradation of the transmission performance.

The measured phase difference between two outputs is shown

in Fig. 5. The phase difference at and are close to the de-

sign specifications, while considering 90 5 phase difference,

the frequency range is from 1.1 to 3.5 GHz with a 104% rela-

tive bandwidth. As the bandwidth is calculated by taking the

ratio of the frequency range within 5 phase error to the center

frequency [9], a 120% relative bandwidth is achieved. For

comparison, the 90 hybrid coupler and the QPS composed of

two different-length conventional microstrips are fabricated at

TSENG AND CHANG: BROADBAND QUADRATURE POWER SPLITTER 27

Fig. 4. Measured transmission coefficients and amplitude imbalance.

Fig. 5. Measured phase difference between two output ports of the QPS with MM TLs, QPS with conventional TLs, and 90 hybrid coupler.

2 GHz. The measured phase differences of two compared cir- cuits also shown in Fig. 5.

The performance of the previously published QPSs and this work is summarized in Table I. Although the printed circuit broad (PCB) fabrication process is employed in this work, a competitive performance is achieved. As the MMIC fabrication process can be applied to implement the QPS proposed in this letter, the relative bandwidth has the potential to be effectively broadened.

IV. C

In this letter, a broadband QPS has been designed, imple- mented, and experimentally verified. In addition, the circuit de- sign procedures are developed in Section II. They can be used

TABLE I

PERFORMANCESUMMARY OFTHEPUBLISHEDQPSS ANDTHISWORK

to determine the component values, namely and , in the LH section and the length of the microstirp. The measured results presented in Section III not only validate the effectiveness of the design procedures in Section II, but also demonstrate that using the MM TL is an effective approach to realize a broadband QPS.

R

[1] F. L. M. Ven Den Bogaat, R. Pyndian, L. E. P. , and F. E. L.-T. N. O.

, “A 10-14 GHz linear MMIC vector modulator with less than 0.1 dB and 0.8 amplitude and phase error,” in IEEE MTT-S Int. Dig., 1990, pp. 465–468.

[2] H. Kamitsuna and H. Ogawa, “Ultra-wideband MMIC active power splitters with arbitrary phase relationships,” IEEE Trans. Microw.

Theory Tech., vol. 41, no. 9, pp. 1519–1523, Sep. 1993.

[3] H. Simon and R. A. Périchon, “A MMIC broad-band 90 power divider using a new all-pass active filter,” in Proc. 30th Eur. Microw. Conf., 2000, pp. 344–347.

[4] D. Kuylenstierna, S. E. Gunnarsson, and H. Zirath, “Lumped-element quadrature power splitters using mixed right/left-handed transmis- sion lines,” IEEE Trans. Microw. Theory Tech., vol. 53, no. 8, pp.

2616–2621, Aug. 2005.

[5] G. D. Vendelin, A. M. Pavio, and U. L. Rohde, Microwave Circuit Design Using Linear and Nonlinear Techniques. New York: Wiley, 1990.

[6] I. H. Lin, M. DeVincentis, C. Caloz, and T. Itoh, “Arbitrary dual-band components using composite right/left-handed transmission lines,”

IEEE Trans. Microw. Theory Tech., vol. 52, no. 4, pp. 1142–1149, Apr. 2004.

[7] C. H. Tseng and T. Itoh, “Dual-band bandpass and bandstop filters using composite right/left-handed metamaterial transmission lines,” in IEEE MTT-S Int. Dig., 2006, pp. 931–934.

[8] M. A. Antoniades and G. V. Eleftheriades, “Compact linear lead/lag metamaterial phase shifters for broadband applications,” IEEE An- tennas Wireless Propag. Lett., vol. 2, pp. 103–106, 2003.

[9] M. A. Antoniades and G. V. Eleftheriades, “A broadband Wilkinson balun using microstrip metamaterial lines,” IEEE Antennas Wireless Propag. Lett., vol. 4, pp. 209–212, 2005.

[10] C. J. Lee, K. M. K. H. Leong, and T. Itoh, “A broadband mi- crostrip-to-CPS transition using composite right/left-handed trans- mission lines with an antenna application,” in IEEE MTT-S Int. Dig., 2005, pp. 1949–1952.

[11] D. M. Pozar, Microwave Engineering, 2nd ed. New York: Wiley, 1998.

> MWCL P01511 < 1

Abstract—A new balanced amplifier (BA) using metamaterial-

based quadrature power splitters (QPSs) is presented in this letter.

Instead of using conventional 90° couplers, the developed BA is implemented by two parallel amplifiers with broadband metamaterial-based QPSs at input and output ends. Since the QPSs can provide a broadband quadrature phase difference between two outputs, the input/output reflections from two amplifiers can be effectively cancelled over a wide bandwidth.

The developed BA demonstrates the input/output return loss of better than 10 dB from 1.2 GHz to 3.5 GHz with 97.9% relative bandwidth.

Index Terms—Balanced amplifiers, broadband amplifiers, quadrature power splitters, metamaterials.

I. I

ONVENTIONALLY

, a balanced amplifier (BA) is realized by integrating two identical amplifiers with input and output 90° hybrid couplers as shown in Fig. 1 (a). It has advantages of improving the input/output matching, optimizing the single amplifier performance regardless of input/output matching, and easily detecting circuit failure [1]. Since two 90° hybrid couplers are employed to cancel the input/output reflection from two amplifiers, the input/output matching performance of the BA is dependent on the characteristics of the 90° coupler.

Based on the circuit configuration shown in Fig. 1 (a), microwave BAs have been implemented with different types of couplers, such as branch-line couplers (BLCs) [2]-[4], Lange couplers [5]-[7], and broadside couplers [8], [9]. In consequence, the increment of the quadrature phase bandwidth between two output ports of the coupler leads to significantly enhance the input/output return loss bandwidth of the BA.

A new broadband quadrature power splitter (QPS) [10] has been developed to achieve a broadband quadrature phase difference using the metamaterial (MM) transmission line (TL) [11]. It is realized by a Wilkinson power divider with a +45°

well-synthesized MM TL and a −45° conventional microstrip (MS) line. An amplitude imbalance of less than 0.9 dB and a phase error of less than ±5° have been experimentally

Manuscript received Sep. ?, 2007. This work was supported by the National Science Council of Taiwan, R. O. C. under Grants NSC 95-2218-E-011-022 and NSC 96-2221-E-011-009.

The authors are with the Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106, R.O.C.

(e-mail: [email protected]).

demonstrated over frequency range from 1.1 GHz to 3.5 GHz with 104% relative bandwidth.

In order to improve the return loss bandwidth, in this letter, metamaterial-based QPSs are exploited to realize the BA as shown in Fig. 1 (b). Two broadband QPSs replace conventional 90° couplers to implement the BA together with two identical amplifiers. For comparison, a single amplifier and a conventional BA using BLCs are also fabricated and measured to clearly manifest the performance improvement of the BA using metamaterial-based QPSs.

II. B

Q

P

S

Based on the design procedures in [10], the broadband QPS is implemented using the circuit configuration shown in Fig. 2 (a). It is composed of a Wilkinson power divider, a conventional microstrip, and a MM TL. The conventional microstrip and MM TL are connected to two output ports of the divider as a phase adjusting circuit to achieve broadband quadrature phase difference. In this letter, the metamaterial-based QPS shown in Fig. 2 (a) is designed at the center frequency of 2 GHz and fabricated on the FR4 substrate with 1.5-mm thickness and the dielectric constant of 4.3. In addition, the left-handed (LH) section in the MM TL is realized

Improvement of Return Loss Bandwidth of Balanced Amplifier Using Metamaterial-Based

Quadrature Power Splitters

Chao-Hsiung Tseng, Member, IEEE and Chih-Lin Chang

C

Fig. 1. Circuit configuration of the balanced amplifier using (a) 90° hybrid coupler and (b) metamaterial-based QPS.

> MWCL P01511 < 2

by Murata 0603 (1.6 mm×0.8 mm) chip inductors and capacitors. It is cascaded by two T-networks with L=12.1 nH (a series of 3.9 nH and 8.2 nH inductors) and C=5 pF.

The measured results shown in Fig. 2 (b) are carried out by the Anritsu 37347C vector network analyzer. The maximum output imbalance ( | S

| | − S

| ) is about 0.9 dB from 0.5 GHz to 3.5 GHz. While considering 90 ° ± ° phase difference 5 ( ∠ S

− ∠ ), the frequency range is from 1.1 GHz to 3.5 GHz S

with a 104% relative bandwidth. For comparison, the measured results of the BLC are also given in Fig. 2 (b).

III. I

B

A

As shown in Fig. 3, the BA is implemented by two broadband QPSs and two identical amplifiers. A low noise FET (NEC NE32584C) biased at V

= 2 V and I

= 20 mA is employed to realize the amplifier. The DC bias network is formed by a Mini-Circuits RF-choke (ADCH-80) and 560 pF bypass and DC blocking chip capacitors. In order to evaluate the cancellation performance of the input/output reflection from two amplifiers, no matching networks are connected at the input and output of the FET to optimize the noise figure and power gain characteristics.

Figure 4 shows the measured input and output return losses of the developed BA using broadband QPSs. The input/output

return loss is better than 10 dB from 1.2 GHz to 3.5 GHz with 97.9% relative bandwidth. The return loss performance of the single FET and the BA using BLCs are also measured and shown in Fig. 4. The results reveal that using metamaterial-based QPSs to realize the BA can effectively improve the input and output return loss bandwidths. The return loss performance of the previously published BAs and this work is summarized in Table I.

Measured gain characteristics of the BA using QPSs are shown in Fig. 5. Compared with the single FET, the BA has a

Fig. 3. Photograph of the developed balanced amplifier.

Fig. 4. Measured (a) input and (b) output return losses of the single FET and balanced amplifiers using QPS and BLC.

Fig. 2. (a) Circuit configuration of the metamaterial-based QPS and (b) measured results of amplitude imbalance and phase difference.

> MWCL P01511 < 3

gain reduction of less than 3 dB over frequency range of 0.8-3.7 GHz. It is because the transmission loss and amplitude imbalance of two QPSs degrade the amplifier gain. The BA using BLCs obtains reasonable gain performance only around the design frequency of 2 GHz. Its gain characteristics are mainly limited by the amplitude imbalance and quadrature phase bandwidth of the BLC shown in Fig. 2 (b). The noise figures of the BAs are measured by Agilent E4445A spectrum analyzer with the noise figure measurement option 219. The noise figure of the BA using QPSs is less than 3 dB from 0.7 GHz to 3GHz, whereas the BA using BLCs gives the noise figure of larger than 2.8 dB over the measured frequency band.

The results shown in Fig. 4, Fig. 5, and Fig. 6 demonstrate that the developed BA using QPSs not only improve the return loss and noise figure bandwidths, but also achieve a flatter gain response.

IV. C

In this letter, a broadband BA has been implemented and experimentally verified. Compared with the conventional circuit configuration using BLCs, it is demonstrated that the BA using QPSs can effectively improve the input/output return

loss bandwidth, the flatness of gain response, and the noise figure characteristics. In addition, compared with other types of couplers, the performance comparison shown in Table I demonstrates that using metamaterial-based QPSs is an effective approach to realize a BA with a broadband return loss bandwidth.

R

[1] D. M. Pozar, Microwave Engineering. , 2nd ed., New York: John Wiley &

Sons, 1998.

[2] M. Gillick, I. D. Robertson, and J. S. Joshi, “Coplanar waveguide two-stage balanced MMIC amplifier using impedance-transforming lumped-distributed branchline couplers,” IEE Proc.-Microw. Antennas Propag., vol. 141, pp. 241–245, Aug. 1994.

[3] S. Banba and H. Ogawa, “Small-sized MMIC amplifiers using thin dielectric layers,” IEEE Trans. Microw. Theory Tech., vol. 43, pp.

485–492, Mar. 1995.

[4] P. Akkaraekthalin, S. Jongjitaree, and V. Vivek, “Coplanar waveguide balanced amplifier using bipolar junction transistors and backed ground-plane hybrids,” in Proc. IEEE Region 10 Int. Conf. (TENCON), 2001, pp. 732-735.

[5] B. L. Nelson, D. K. Umemoto, C. B. Perry, R. Dixit, B. R. Allen, M. E.

Kim, and A. K. Oki, “High-linearity, low DC power monolithic GaAs HBT broadband amplifiers to 11 GHz,” in IEEE Microw. and Millimeter-Wave Monolithic Circuits Symp. Dig., 1990, pp. 15–18.

[6] K. W. Kobayashi, M. Nishimoto, L. T. Tran, H. Wang, J. Cowles, T. R.

Block, J. Elliott, B. Allen, A. K. Oki, and D. C. Streit, “A 44 GHz InP-based HBT double-balanced amplifier with novel current re-use biasing,” in IEEE Radio Frequency Integrated Circuits (RFIC) Symp.

Dig., 1998, pp. 267–270.

[7] S. Seo, D. Pavlidis, and J.-S. Moon, “A wideband balanced AlGaN/GaN HEMT MMIC low noise amplifier for transceiver front-ends,” in European Gallium Arsenide and other Compound Semiconductors Application (EGAAS) Symp. Dig., 2005, pp. 225-228.

[8] R. S. Engelbrecht, and K. Kurokawa, “A wide-band low noise L-band balanced transistor amplifier,” Proc. IEEE, vol.53, pp. 237–248, Mar.

1965.

[9] T. Imaoka, S. Banba, A. Minakawa, and N. Imai, “Millimeter-wave wide-band amplifiers using multilayer MMIC technology,” IEEE Trans.

Microw. Theory Tech., vol. 45, pp. 95–101, Jan. 1997.

[10] C.-H. Tseng and C.-L. Chang, “A broadband quadrature power splitter using metamaterial transmission line,” IEEE Microw. Wireless Compon.

Lett., vol.18, Jan. 2007.

[11] A. Lai, C. Caloz, and T. Itoh, “Composite right/left-handed transmission line metamaterials,” IEEE Microw. Mag., vol. 5, pp. 34-50, Sep. 2004.

TABLEI

PERFORMANCE SUMMARY OF THE PUBLISHED BAS AND THIS WORK

Fig. 5. Measured gain characteristics of the single FET and balanced amplifiers using QPS and BLC.

Fig. 6. Measured noise figure characteristics of the balanced amplifiers using QPS and BLC.

Wide-band balun using composite right=left-handed transmission line C.-H. Tseng and C.-L. Chang

A wide-band balun is developed using a composite right=left-handed (CRLH) transmission line (TL) at 2 GHz. It is composed of a Wilkinson power divider and two phase-adjusting transmission lines, namely the CRLH TL and the conventional TL. The input reflection coefficient is better than
10 dB from 1 to 4 GHz. Over the frequency range of 1.24–3.58 GHz, an amplitude imbalance of less than 0.7 dB and a phase error of less than 10^have been experi- mentally demonstrated.

Introduction: The balun is a critical component in the radio- frequency (RF) front-end circuit of a wireless communication system. It can equally divide the input RF signal into two output ports along with a 180^out-of-phase angle. One can find applications on push-pull amplifiers, balanced mixers, and antennas. Since the composite right=left-handed (CRLH) transmission line (TL), referred to as the metamaterial (MM) TL, has the capability of arbitrarily synthesising the transmission phase response[1], it can be realised as a phase-adjusting TL, and then applied to implement the wide-band baluns[2, 3]together with a power divider and a conventional TL.

However, owing to the lack of an effective synthesis method to achieve a broadband 180^ phase difference between two phase- adjusting TLs, the bandwidth of the balun cannot be significantly broadened. In this Letter, based on the method in[4, 5], an improved phase synthesis concept of the CRLH TL is proposed to obtain a wider 180^ out-of-phase bandwidth, with reference to the conven- tional TL. Therefore, a bandwidth-enhanced balun can be implemen- ted by connecting a well-synthesised CRLH TL and a conventional TL with two output ports of the power divider.

Fig. 1 Photograph of developed wide-band balun

Fig. 2 Phase responses of CRLH TL and microstrip line

Circuit design: The developed wide-band balun shown inFig. 1 is realised by a Wilkinson power divider with two phase-adjusting TLs, namely the CRLH TL and the microstrip line. With reference to the phase-lag response of the microstrip, the CRLH TL gives the phase- advanced response shown inFig. 2to achieve the 180^ out-of-phase angle. Unlike the phase-response formation in[2]and[3], in this work

two frequencies are designated to synthesise the phase response of the CRLH TL. Hence, the slope of the phase-response curve can be flexibly controlled to obtain a 180^ phase difference over a wide bandwidth. In addition, the CRHL TL is composed of the left-handed (LH) section implemented by two cascaded T-networks shown in the inset ofFig. 1and the right-handed (RH) TL with a specified length.

Fig. 2 illustrates the phase responses of the CRLH TL and the microstrip. As the frequencies f0, f1, and f2are given, the length of the microstrip can be properly chosen to simulate the phases fMS1 and fMS2of the microstrip at f1and f2, respectively. Then the phases fC1( f1) and fC2( f2) of the CRLH TL can be calculated by increasing the 180^ phase difference. Based on the phase synthesis method using two frequency-dependent phase responses in[4, 5], the values of L and C in the LH section and the length of the RH TL can be determined to synthesise the desired phase-responses curve with fC1and fC2at f1and f2, respectively. Hence, the phase-response curve of the CRLH TL has the same slope as that of the conventional microstrip line along with a broadband 180^phase difference over the frequency range from f1to f2.

Results: To implement a wide-band balun as shown in Fig. 1, the frequencies f0, f1, and f2are chosen as 2, 1.4, and 2.6 GHz, respec- tively, to give a 60% design bandwidth. The developed balun is fabricated on the FR4 substrate with 1.5 mm thickness, dielectric constant of 4.3, and loss tangent of 0.02. The LH section in the CRLH TL is realised by Murata 0603 (1.6  0.8 mm²) chip inductors and capacitors. In addition, as depicted in the inset of Fig. 1, two T-networks with series capacitors C ¼ 2.2 pF and shunt inductors L ¼ 5.7 nH (realised by 1.8 and 3.9 nH) are cascaded to form the LH section. The circuit dimension parameters are also indicated in Fig. 1. For measurement consideration, two 50^ bends are linked to two output ports of the balun with the convenience to measure the isolation performance. The measured results presented in this Letter were made using an Anritsu 37347C vector network analyser over the frequency range from 1 to 4 GHz with 401 swept points.

The measured results of the reflection and transmission coefficients are shown inFig. 3. The input reflection coefficient jS11jis better than

10 dB from 1 to 4 GHz, while the amplitude imbalance between two output ports, namely jS31j–jS21j, is about 0.7 dB from 1.24 to 3.58 GHz.

It demonstrates that the LH section implemented by chip components does not cause significant degradation of the transmission performance.

Fig. 4illustrates the phase difference between two output ports of the balun. At design frequencies f1and f2, namely 1.4 and 2.6 GHz, the phase differences are 180.2^ and 177.7^, respectively. In addition, as considering 180^10^ phase difference, a 97% relative bandwidth, namely from 1.24 to 3.58 GHz, can be achieved. As the bandwidth is calculated by taking the ratio of the frequency range within  10^ phase error to the design centre frequency f0, one can obtain a 117%

relative bandwidth. For comparison, the measured phase differences of the hybrid ring coupler and the balun with two different-length micro- strips are also shown in Fig. 4. The phase bandwidth of the balun developed in this Letter is superior to those of the conventional 180^ out-of-phase components. The performance comparison of this work and the previously published wide-band balun using the metamaterial or CRLH TLs is shown inFig. 5.

Fig. 3 Measured reflection and transmission performance of developed balun

ELECTRONICS LETTERS 11th October 2007 Vol. 43 No. 21

Fig. 4 Measured phase difference between two output ports

Fig. 5 Performance comparison of wide-band baluns

Conclusion: A wide-band balun using the CRLH TL has been designed, implemented, and experimentally validated in this Letter.

It utilises the phase synthesis property of the CRLH TL to achieve the phase-adjusting TL with a broadband 180^ phase-advanced angle compared with the conventional TL. The measured results demon- strate that using the CRLH TL is an effective approach to design a wide-band balun. In addition, the multilayered low temperature co- fired ceramic (ML LTCC) or monolithic integrated circuit (MMIC) fabrication processes can be applied to implement the wide-band balun proposed in this Letter with further circuit size reduction.

Acknowledgment: This work was supported by the National Science Council of Taiwan, R.O.C. under grants NSC 95-2218-E-011-022.

#The Institution of Engineering and Technology 2007 13 June 2007

Electronics Letters online no: 20071759 doi: 10.1049/el:20071759

C.-H. Tseng and C.-L. Chang (Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106, Republic of China)

E-mail: [email protected] References

1 Lai, A., Caloz, C., and Itoh, T.: ‘Composite right=left-handed transmission line metamaterials’, IEEE Microw. Mag., 2004, (9), pp. 34–50 2 Antoniades, M.A., and Eleftheriades, G.V.: ‘A broadband Wilkinson

balun using microstrip metamaterial lines’, IEEE Antennas Wirel.

Propag. Lett., 2005, 4, pp. 209–212

3 Mao, S.-G., and Chueh, Y.-Z.: ‘Broadband composite right=left-handed coplanar waveguide power splitters with arbitrary phase responses and balun and antenna applications’, IEEE Trans. Antennas Propag., 2006, 54, (1), pp. 243–250

4 Lin, I.-H., Devincentis, M., Caloz, C., and Itoh, T.: ‘Arbitrary dual-band components using composite right=left-handed transmission lines’, IEEE Trans. Microw. Theory Tech., 2004, 52, (4), pp. 1142–1149

5 Tseng, C.-H., and Itoh, T.: ‘Dual-band bandpass and bandstop filters using composite right=left-handed metamaterial transmission lines’.

IEEE MTT-S Int. Microw. Symp. Dig., San Francisco, CA, USA, 2006, pp. 931–934

ELECTRONICS LETTERS 11th October 2007 Vol. 43 No. 21

Bandwidth-Enhanced Quadrature Power Splitter and Balun Using Metamaterial Transmission Lines

Chih-Lin Chang and Chao-Hsiung Tseng Department of Electronic Engineering

National Taiwan University of Science and Technology Taipei, Taiwan, R.O.C.

[email protected]

Abstract—In this paper, the bandwidth-enhanced quadrature

power splitter (QPS) and balun using metamaterial (MM) transmission lines (TLs) are presented. They consist of a Wilkinson power divider, a conventional TL, and a well- synthesized MM TL. Since the phase response of the MM TL can be arbitrarily synthesized, the slope of the phase-response curve of the MM TL can be achieved as the same as that of the conventional TL with a specified phase difference, such as 90

180

and implemented at 2 GHz and experimentally demonstrated.

The QPS has an output amplitude imbalance of less than 0.9 dB and a phase error of less than

relative bandwidth), while over the frequency range of 1.24–3.58 GHz (97% relative bandwidth), the balun has an output amplitude imbalance of less than 0.7 dB and a phase error of less than

Keywords-metamateial; left-handed (LH) transmission line;

quadrature power splitter; balun; microwave passive component

I. I

Quadrature power splitters (QPSs) [1]-[4] and baluns [5], [6]

are key components for implementation of balance and push- pull amplifiers, balance and image-rejection mixers, and linear vector modulators. They have major characteristics of balance output amplitude, 90 ° or 180° phase difference, and good isolation between two output ports. In addition, the impedance and phase relative bandwidths are the important parameters to evaluate a broadband QPS or a balun.

The QPS can be easily realized by a Wilkinson power divider together with the phase-adjusting circuit. The high-pass and low-pass filters [1], all-pass active filters [2], or phase compensated transmission lines (TLs) [3] can be employed as the phase-adjusting circuit to adjust two output phase responses of the power divider. In addition, based on the theory of the metamaterial (MM) TL [7], a well-synthesized MM TL can achieve the arbitrary phase response. Hence, it can be utilized to implement the miniaturized QPS [4]. As the phase-adjusting circuit is designed to have a 180 ° out-of-phase response difference, the similar design concept has been applied to realize the broadband baluns [5], [6].

In this paper, the developed bandwidth-enhanced QPSs and baluns consist of a Wilkinson power divider and two phase- adjusting TLs, namely a well-synthesized MM TL and a

conventional microstrip line. In order to obtain the broadband 90 ° and 180° phase differences between two phase-adjusting TLs, the phase synthesis procedures of the MM TL [8] are adapted to achieve the same slope of the phase-response curve of the MM TL as that of the conventional TL over wide frequency range. Based on this design concept, the broadband QPS [8] and balun [9] have been experimentally demonstrated.

II. D

C

Figure 1 (a) shows the configuration of the bandwidth- enhanced QPS and balun using the MM TL. It consists of a

This work was supported by the National Science Council of Taiwan, R. O. C.

under Grants NSC 95-2218-E-011-022.

Fig. 1. (a) Configuration of the bandwidth-enhanced QPS and balun, and (b) The phase responses of the MM TL and microstrip.

Wilkinson power divider, a conventional microstrip, and a MM TL. The Wilkinson power divider equally separates the input power into two output ports, and also provides good isolation between them. The conventional microstrip and MM TL are connected to two output ports of the divider as phase adjusting TLs to achieve broadband 90 ° or 180° phase difference.

Figure 1 (b) shows the phase responses of the MM TL and microstrip. Referring to the microstrip, the phase response of the MM TL is synthesized to have the 90 ° or 180° phase increment at f and

f , and achieve the same slope of the

phase-response curve as that of the MS [8]. Therefore, as two phase-adjusting TLs are connected with two output ports of the power divider, a QPS or balun can be implemented with a broadband phase difference and a good isolation between two output ports.

III. B

-E

QPS

B

The bandwidth-enhanced QPS and balun are realized using the circuit configuration shown in Fig. 1 (a). The FR4 substrate with 1.5-mm thickness, dielectric constant of 4.3, and loss tangent of 0.02 is employed to fabricate the developed QPS and balun. In addition, the LH section in the MM TL is realized by Murata 0603 (1.6 mm ×0.8 mm) chip inductors and capacitors. The measured results in this paper are carried out by the Anritsu 37300C vector network analyzer.

For QPS development, the frequencies f ,

f , and

f are

respectively chosen as 1 GHz, 1.2 GHz, and 2.8 GHz to achieve a 80% design bandwidth. The circuit is implemented as shown in Fig. 2 (a), and its dimension parameters are indicated as well. As depicted in the inset of Fig. 2 (a), the LH section is cascaded by two T-networks with L=12.1 nH (realized by 3.9 nH and 8.2 nH inductors) and C=5 pF. Two 50 °-bends are connected with two outputs of the QPS for the convenience to measure the isolation performance.

For balun development, the frequencies f ,

f , and

f are

respectively chosen as 2 GHz, 1.4 GHz, and 2.6 GHz to give a 60% design bandwidth. As depicted in the inset of Fig.2 (b), two T-networks with L=5.7 nH (realized by 1.8 nH and 3.9 nH) and C=2.2 pF are cascaded to form the LH section. The circuit dimension parameters are also indicated in Fig. 2 (b).

For measurement consideration, two 50 ° bends are linked to two output ports of the balun with the convenience to measure the isolation performance.

IV. E

R

A. Measured Results of the Developed QPS

The measured reflection coefficients at the input port and isolation performance between two output ports of the developed QPS are shown in Fig. 3 (a). The | S

| is better than -10 dB from 0.85 GHz to 3.46 GHz, while the isolation

| S

| is larger than 10 dB from 0.9 GHz to 3.3 GHz. The measured transmission coefficients and amplitude imbalance

between two output ports are also illustrated in Fig. 3 (a). The maximum output imbalance, namely | S

| | − S

| , is about 0.9 dB from 0.5 GHz to 3.5 GHz.

The measured phase difference between two output ports of the QPS is shown in Fig. 3 (b). The phase difference at f and

f are close to the design specifications, while considering

90 ° ± ° 5 phase difference, the frequency range is from 1.1 GHz to 3.5 GHz with a 104% relative bandwidth. As the bandwidth is calculated by taking the ratio of the frequency range within

± ° 5 phase error to the center frequency f [6], a 120% relative

bandwidth is achieved. For comparison, the 90 ° hybrid coupler and the QPS composed of two different-length conventional microstrips are fabricated at 2 GHz. The measured phase differences of two compared circuits also shown in Fig. 3 (b).

B. Measured Results of the Developed Balun

The measured reflection and transmission coefficients of the developed balun are shown in Fig. 4 (a). The input reflection coefficient | S

| is better than -10 dB from 1 GHz to 4 GHz, while the amplitude imbalance between two output ports, namely | S

| | − S

| , is about 0.7 dB from 1.24 GHz to

Fig. 2. Photographs of the developed bandwidth-enhanced (a) QPS and (b) balun.

3.58 GHz. Figure 4 (b) illustrates the phase difference between two output ports of the balun. At design frequencies f , and

f , namely 1.4 GHz and 2.6 GHz, the phase differences are

180.2 ° and 177.7°, respectively. In addition, as considering 180 °±10° phase difference, a 97% relative bandwidth, namely from 1.24 GHz to 3.58 GHz, can be achieved. As the bandwidth is calculated by taking the ratio of the frequency range within ±10° phase error to the design centre frequency f , one can obtain a 117% relative bandwidth. For

comparison, the measured phase differences of the 180 ° hybrid ring coupler and the balun with two different-length microstrips are also shown in Fig. 4 (b). The phase bandwidth of the balun developed in this paper is superior to those of the conventional 180 ° out-of-phase components.

V. P

D

The performance of the previously published QPSs and this work is summarized in Table I. Although the printed circuit broad (PCB) fabrication process is employed in this work, a competitive performance is achieved. On the other hand, the performance comparisons of the baluns using the MM TLs are given as Table II. In this work, the phase bandwidth of the developed balun is significantly enhanced. It is because the

phase-synthesized concept of the MM TL using two frequency points can effectively control the slope of the phase-response curve of the MM TL.

VI. C

In this paper, bandwidth-enhanced QPS and balun using the MM TL have been designed, fabricated, and experimentally verified. The measured results presented in Sec. IV not only demonstrate the effectiveness of the design concept in Sec. II, but also validate that using the MM TL is an effective approach to realize the broadband QPS and balun.

As shown in Fig. 3 (a) and Fig. 4 (a), the output amplitude imbalances of the QPS and balun demonstrate that the LH section implemented by chip components does not cause the significant degradation of the transmission performance. As the advanced fabrication process, such as monolithic microwave integrated circuit (MMIC) or low-temperature co-fired ceramic (LTCC), can be applied to implement the QPS and balun proposed in this paper, the relative bandwidth has the potential to be broadened. In addition, the amplitude imbalance between two output ports may be successfully improved.

Fig. 4. (a) Measured reflection and transmission coefficients of the balun, and (b) measured phase difference between two output ports of the balun with MM TLs, the balun with conventional TLs, and 90° hybrid coupler.

Fig. 3. (a) Measured reflection and transmission coefficients of the QPS, and (b) measured phase difference between two output ports of the QPS with MM TLs, the QPS with conventional TLs, and 90° hybrid coupler.

R

[1] F. L. M. Ven Den Bogaat, R. Pyndian, L. E. P., and F. E. L.-T. N. O., “A 10-14 GHz linear MMIC vector modulator with less than 0.1 dB and 0.8° amplitude and phase error,” in IEEE MTT-S Int. Microw. Symp.

Dig., 1990, pp. 465–468.

[2] H. Kamitsuna, and H. Ogawa, “Ultra-wideband MMIC active power splitters with arbitrary phase relationships,” IEEE Trans. Microw.

Theory Tech., vol. 41, pp. 1519–1523, Sep. 1993.

[3] H. Simon and R. A. Périchon, “A MMIC broad-band 90° power divider using a new all-pass active filter,” in Proc. 30^th Eur. Microw. Conf., 2000, pp. 344–347.

[4] D. Kuylenstierna, S. E. Gunnarsson, and H. Zirath, “Lumped-element quadrature power splitters using mixed right/left-handed transmission lines,” IEEE Trans. Microw. Theory Tech., vol. 53, pp. 2616–2621, Aug.

2005.

[5] M. A. Antonlades and G. V.Eleftheriades, “A broadband Wilkinson balun using microstrip metamaterial lines,” IEEE Antennas Wireless Propag. Lett., vol. 4, pp. 209–212, 2005.

[6] S.-G. Mao and Y.-Z. Chueh, “Broadband composite right/left-handed coplanar waveguide power splitters with arbitrary phase responses and balun and antenna applications,” IEEE Trans. Antennas Propag., vol.

54, pp. 243–250, Jan. 2006.

[7] A. Lai,, C. Caloz, and T. Itoh, “Composite right/left-handed transmission line metamaterials,” IEEE Micow. Mag., vol. 5, Sep. 2004.

[8] C.-H. Tseng and C.-L. Chang, “A broadband quadrature power splitter using metamaterial transmission line,” IEEE Microw. Wireless Compon.

Lett., accepted for publication.

[9] C.-H. Tseng and C.-L. Chang, “Wide-band balun using composite right/left-handed transmission line,” Electronics Lett., submitted for pulication.

TABLE I. PERFORMANCE SUMMARY OF THE QPSS

TABLE II. PERFORMANCE SUMMARY OF THE BALUN

張智林*、曾昭雄

國立台灣科技大學 電子工程系

摘要—本論文係使用左手(left-handed)傳輸線研製 具 90及 180相位差之寬頻功率分配器。該型功率分配 器由威爾金森功率分配器、傳統微帶線(microstrip)及左 手傳輸線所構成。由於左手傳輸線具有可任意合成相位 響應的特性，因此，可在指定的頻率範圍內，設計左手 傳輸線與傳統傳輸線擁有相同的相位曲線斜率，並具備 90及 180的相位差。本論文中，設計於 2GHz 之兩型 功率分配器已完成實驗量測，其效能為：90相位差之 功率分配器在1.1~3.5GHz(相對頻寬為 104%)有少於 0.9 dB 的輸出振幅差和 90±5的相位差；180相位差之功率 分配器在1.24~3.58GHz(相對頻寬為 97%)有少於 0.7 dB 的輸出振幅差異和180±10的相位差異。

一、 簡介

90及 180相位差之寬頻功率分配器[1]-[6]，為設 計平衡式(balanced)和推挽式(push-pull)放大器、平衡式 和鏡像抑制混頻器(image rejection mixer)之關鍵被動元 件。該型功率分配器須具備等量大小的輸出振幅、90或 180的相位差及良好輸出埠隔離度等特性。此外，輸入 阻抗頻寬及相位差頻寬更為評估寬頻 90及 180相位差 功率分配器之效能良窳的重要參數。

寬頻 90相位差之功率分配器可使用威爾金森功率

分配器及相位調整電路實現。高通濾波器、低通濾波器 [1]、全通主動式濾波器[3]或相位補償傳輸線[2]皆可被 用作為相位調整電路，該相位調整電路主要功能為調整 功率分配器之兩輸出埠之相位響應。此外，基於左手傳 輸線的理論[7]，設計良好之左手傳輸線能實現具有任意

相位之輸出響應。因此，它可被用來設計微型化的 90

相位差的功率分配器[4]。當相位調整電路設計於具有 180相位差響應時，類似的設計概念則可應用於研製寬 頻的 180相位差功率分配器[5]，[6]。

在本論文中，主要係使用威爾金森功率分配器及兩 條相位調整傳輸線，設計具 90及 180相位差之寬頻功 率分配器。其中，兩條相位調整傳輸線分別採用設計良 好之左手傳輸線及傳統微帶線實現。為了獲得寬頻的 90及 180相位差，採用左手傳輸線進行寬頻相位合 成，且與傳統的微帶線在寬闊的頻率範圍內達到近乎相 同的相位曲線斜率。基於這個設計概念，本論文已完成 寬頻 90及 180相位差之功率分配器的實驗論證。

二、 設計概念

使用左手傳輸線設計頻寬 90及 180相位差之功率 分配器的電路結構如圖 1 (a)所示，該電路主要係由威爾

圖1 (a) 具 90及 180相位差之寬頻功率分配器及(b) 左手傳輸線和傳 統微帶線之相位響應。

金森功率分配器，傳統微帶線和設計良好的左手傳輸線 所構成。威爾金森功率分配器之主要功能為將輸入功率 平均地分配至兩個輸出埠，並於兩輸出埠之間，提供良 好的隔離度。接著，兩輸出埠分別連接傳統微帶線和左 手傳輸線，並藉由兩傳輸線的相位響應，調整兩輸出埠 具有寬頻的 90及 180相位差。

圖 1 (b) 為左手傳輸線和傳統微帶線之相位響應

圖，本論文主要係根據傳統微帶線相位響應，合成左手 傳輸線之相位響應，使其相位響應在頻率 f

及 f

時，能 較傳統微帶線增加 90及 180；並使其曲線斜率與傳統 微帶線之曲線斜率，在指定的頻率範圍是幾乎相同的 [8]。因此，當功率分配器的兩個輸出埠適當的與兩相位 調整傳輸線連接時，寬頻 90及 180相位差之功率分配 器將可容易的被設計及實現，並在兩輸出埠之間具有寬 頻的相位差及良好的隔離度。

使用左手傳輸線研製具 90及 180相位差之寬頻微波功率分配器

本研究由國家科學委員會贊助(計畫編號 NSC 95-2218-E-011-022)。

三、 具90及 180相位差之寬頻功率分配器

本論文中之頻寬 90及 180相位差之功率分配器將 採用圖 1 (a) 之電路架構來實現，並用以證明該電路結構 具有預期的寬頻相位響應。頻寬 90及 180相位差之功 率分配器使用玻璃纖維板(FR4)來實現製作，其厚度為 1.5 mm 、 介 電 係 數 為 4.3 、 損 失 正 切 (loss tangent) 為 0.02 。 此 外 ， 在 製 作 左 手 傳 輸 線 時 ， 使 用 了 Murata 0603(1.6 mm×0.8 mm)的晶片電感及電容。本文中之量測 結果係使用 Anritsu 3700C 的網路分析儀進行量測。

為了實現具有 80%設計頻寬之 90相位差功率分配 器，頻率 f

、f

和 f

分別選擇為 2 GHz，1.2 GHz 和 2.8 GHz。此電路架構及尺寸參數如圖 2(a)所示，其左手傳 輸線是由兩個 T 型網路串聯，其電感值為 12.1 nH(由 3.9 nH 和 8.2 nH 串聯獲得)、電容值為 5 pF。爲了方便量測

隔離度的性能，故將兩個輸出埠分別連接至具有 50轉

角的微帶線。

此外，為了實現具有 60%設計頻寬之 180相位差之 功率分配器，頻率 f

、f

和 f

分別選擇為 2GHz，1.4GHz 和 2.6GHz。如圖 2(b)所描述，左手傳輸線亦使用兩級 T 型網路串接而成，其中，電感值為 5.7 nH(由 1.8 nH 和 3.9 nH 串聯獲到)、電容值為 2.2 pF。如前文所述，爲了 方便量測隔離度的性能，故將兩個輸出埠分別連接至具

有 50轉角的微帶線。且其電路尺寸完整地顯示於圖

2(b)。

四、 測量結果 A、90相位差之功率分配器的測量結果

圖 3(a) 為 90相位差之功率分配器的輸入端反射係 數及兩輸出埠間的隔離度性能，其反射係數 |S

|，從 0.85 GHz 到 3.46 GHz 皆低於 -10 dB，隔離度 |S

|，頻率 從 0.9 GHz 到 3.3 GHz 皆大於 10 dB。在兩輸出埠所量測

到的穿透係數及振幅不平衡亦顯示於圖 3(a)。其最大輸

出不平衡 (即 |S

|-|S

|)，從 0.5 GHz 到 3.5 GHz 大約為 0.9 dB。

於 90相位差之功率分配器的兩輸出埠間量測到的

相位差顯示於圖 3(b)。於頻率點 f

和 f

，其相位差十分

接近本論文所定的設計規格。當考慮 90±5的相位差

時，其頻率範圍可從 1.1 GHz 到 3.5 GHz，亦即具有 104%的相對頻寬。若使用設計的中心頻率 f

[5]來計算

±5誤差之頻率範圍時，則可達到 120%的相對頻寬。為 了與其他具有相同特性之微波元件比較，中心頻率設計 於 2GHz 時之枝幹耦合器(branch-line coupler)及由兩個不

同長度之傳統微帶線所構成的 90相位差之功率分配器

亦一併製作，其測量結果如圖 3(b)所示。

B、180相位差之功率分配器的測量結果

圖 4(a) 為 180相位差之功率分配器的反射及穿透係 數，輸入端的反射係數 |S

| 從 1 GHz 到 4 GHz 皆低於- 10 dB，兩輸出埠間之最大振幅不平衡 (即 |S

|-|S

|) 頻率 從 1.24 GHz 到 3.85 GHz 大約為 0.7 dB。如圖 4(b)所 示，180相位差之功率分配器的兩個輸出埠間相位差，

在設計頻率 f

和 f

(即 1.4 GHz 和 2.6 GHz)，其相位差分 別是 180.2和 177.7。此外，當考慮到 180±10的相位

圖2 (a) 及(b)分別為 90及 180相位差之寬頻功率分配器。

差時，可達 97%的相對頻寬，其頻率範圍為 1.24 GHz 到 3.58 GHz。若使用設計中心頻率 f

來計算±10誤差之相

對頻寬時，則可獲得 117%的相對頻寬。為了與其他具

有相同特性之微波元件比較，環形耦合器及由兩個不同

長度之傳統微帶線所組成的 180相位差之功率分配器，

亦設計及製作於 2GHz 之中心頻率，其量測結果一併顯

示於圖 4(b)。若考慮相位頻寬特性之良窳，本文所提出

之電路架構，明顯優於傳統具 180相位差輸出的微波元

件。

五、 特性討論

為比較其他研究團隊所提出的 90相位差功率分配

器與本文所研製的新型功率分配器，其元件性能整理於

表 I 中。相較於參考文獻中使用前瞻積體電路製程，本

研究雖然使用印刷電路板製作，但還是可獲得具有競爭

力的電路效能。另一方面，使用左手傳輸線實現 180相

位差功率分配器之電路特性比較，如表 II 所示。本文所

研製的 180相位差功率分配器，其相位頻寬顯著地提

高，主要係因使用左手傳輸線之相位響應可任意地合成

的概念，並使用兩個合成頻率點有效地控制左手傳輸線

的相位響應曲線。

圖3、(a)為 量測 90相位差功率分配器之反射及穿透係數，(b)為比 較三種不同電路型式之輸出埠相位差。

表I、已發表之 90相位差功率分配器的性能比較。

表

II

圖4、(a)為量 測 180相位差功率分配器之反射及穿透係數，(b)為比 較三種不同電路型式之輸出埠相位差。

六、 結論

在本論文中，已完成設計、製作和實驗驗證，使用 左手傳輸線設計 90及 180相位差之功率分配器，得以 強化兩輸出埠間之相位差頻寬。第三節中的測量結果可 用來驗證第二節所敘述之設計概念，並確認使用左手傳 輸線製作 90及 180相位差之功率分配器是一種有效提 高頻寬的方法。

如圖 3(a)和圖 4(a)所示，由 0603 晶片電感及電容所 構成的左手傳輸線，不會貢獻嚴重的衰減。若前瞻製程 (如微波積體電路或低溫共燒陶瓷)能被應用於設計本論 文所提出電路架構，則有使其相對頻寬變更寬的潛力。

此外，兩個輸出埠之間的振幅不平衡也將可有效的改 善。

參考文獻

[1] F. L. M. Ven Den Bogaat, R. Pyndian, L. E. P., and F. E. L.-T.N.O.,“A 10-14 GHz linear MMIC vector modulator with less than 0.1 dB and 0.8^o amplitude and phase error,” in IEEE MTT-S Int. Microw. Symp. Dig., 1990, pp. 465–468.

[2] H. Kamitsuna, and H. Ogawa, “Ultra-wideband MMIC active power splitters with arbitrary phase relationships,” IEEE Trans. Microw.

Theory Tech., vol. 41, pp. 1519–1523, Sep. 1993.

[3] H. Simon and R. A. Périchon, “AMMIC broad-band 90^opower divider using a new all-pass active filter,” in Proc. 30th Eur. Microw. Conf., 2000, pp. 344–347.

[4] D. Kuylenstierna, S. E. Gunnarsson, and H. Zirath, “Lumped-element quadrature power splitters using mixed right/left-handed transmission lines,” IEEE Trans. Microw. Theory Tech., vol. 53, pp. 2616–2621, Aug.2005.

[5] M. A. Antonlades and G. V.Eleftheriades,“A broadband Wilkinson balun using microstrip metamaterial lines,” IEEE Antennas Wireless Propag. Lett., vol. 4, pp. 209–212, 2005.

[6] S.-G. Mao and Y.-Z. Chueh, “Broadband composite right/left-handed coplanar waveguide power splitters with arbitrary phase responses and balun and antenna applications,”IEEE Trans. Antennas Propag., vol. 54, pp.

243–250, Jan. 2006.

[7] A. Lai,, C. Caloz, and T. Itoh, “Composite right/left-handed transmission line metamaterials,” IEEE Micow. Mag., vol. 5, Sep. 2004.

[8] C.-H. Tseng and C.-L. Chang, “A broadband quadrature power splitter using metamaterial transmission line,”IEEE Microw. Wireless Compon.

Lett., accepted for publication.

[9] C.-H. Tseng and C.-L. Chang, “Wide-band balun using composite right/left-handed transmission line,” Electronics Lett., submitted for pulication.

表 Y04

行政院國家科學委員會補助國內專家學者出席國際學術會議報告

2007 年 8 月 30 日

報告人姓名 曾昭雄 服務機構

及職稱

國立台灣科技大學電子系 助理教授

時間 會議

地點

2007 年 8 月 20-24 日 日本，新潟市 (Niigata, Japan)

本會核定 補助文號 會議

名稱

(中文) 2007 年國際天線暨傳播研討會

(英文) 2007 International Symposium on Antennas and Propagation

發表 論文 題目

(中文) N/A (英文) N/A

報告內容應包括下列各項：

一、 參加會議經過

8/21 下午抵達日本新潟 TOKI MESSE 會議中心，完成報到手續，並領取會議相關資料。下午參與 1A4: Broadband Antennas 及 1A5: Circularly Polarized Planar Antennas。

8/22 上午參與 2C1: Patch and Printed Antennas 及 2A2: Broadband and Multi-band Antennas and Applications II。下午參與 2C3: On-body Wireless Communications 及 2C4: Medical Applications and Biological Effects。

8/23 上午參與 3E1: Periodic Structures I 及 3E2: Periodic Structures II。下午參與 Poster Session。

8/24 上午參與 4E1: EBG and Metamaterials I 及 4E2: EBG and Metamaterials II。

二、 與會心得

今年之國際天線暨傳播研討會(ISAP 2007)在日本新潟舉辦，亦為本人第一次參與 ISAP 研討會。

在參與本次研討會之前，本人正在研製使用左/右手傳輸線饋入之圓極化天線。雖已大致完成模擬與 量測工作，亦初步驗證該圓極化天線具有較傳統圓極化天線具有大幅改善之圓極化頻寬，但苦無機 會確認該型天線是否擁有至目前為止已發表文章之最佳圓極化頻寬。正逢 ISAP2007 於鄰近的日本 舉辦，素聞 ISAP 所收錄之天線與傳播相關論文內容品質不亞於 IEEE AP-S 研討會，加上國科會計 畫補助出席國際研討會經費，遂決定參與該會，除了聹聽天線及傳播領域之最新發展概況，並趁此 機會向國際知名天線學者請益。

新潟為日本重要的米鄉，亦為重要的海港城市。為了體驗從旅遊手冊上獲得的資訊，第一天討 論會結束後，即與一起參與研討會的電機系馬自莊教授到日本簡餐連鎖店吉野家，品嚐米食料理。

果不其然，雖然是平價簡餐料理，其所附的白米飯粒粒晶瑩飽滿，送入口中更是香 Q 滑順。飽餐之 後，與馬教授開玩笑的說，也許我們吃的是從台灣進口的池上米或越光米！雖然沒有加以確認米飯 的產地，但享受熱騰騰的白米飯的確是一大享受！為了節省旅費，我與馬教授住宿於距離會議中心 步行約 20 分鐘的旅館，雖然每日需花將近一小時往返會議中心，但這不啻是體驗港市風情的機會。

由於會議中心位於海港出口附近，每日早晨沿著港邊小徑步行至會場，除了可享受北國秋天溫暖的 晨陽，海風輕拂臉龐，更有如置身於蓬萊仙境。每日會議結束，伴著斜長夕陽與海港美景，鎮日的 用功疲累亦消失殆盡。

技術研討會方面，除了參與本研討會注意的焦點圓極化天線之最近發展近況，在參與技術論 文討論時發現，日本於微波及毫米波領域在世界上具有舉足輕重的領先地位，主要係因為除了基礎 電磁研究及新型微波元件研製，日本微波研究學者正積極的將所研發的元件用於發展微波及毫米波 系統，且應用於與我們日常生活息息相關之領域如：醫療、農業遙測、測距雷達、毫米波區域網路 通訊等。在台灣微波元件研發成果嶄露頭角之際，應以日本為效法對象，逐步發展微波系統研究，

以確立台灣微波研究領域在國際上之優勢。

三、 建議

四、 攜回資料名稱及內容

2007 International Symposium on Antennas and Propagation CD ROM 五、 其他

附件三