DC-12-GHz 10-dB gain shunt-series shunt-shunt wideband amplifiers by commercially available 0.35 mu M SiGe HBT technology

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characteristic is practically without variation. Gain of 8 dBi and VSWR of less than 2 at 220-MHz frequency have been obtained. The concept of the presented antenna array may be used for frequencies from some hundreds of MHz to about 30 GHz. ACKNOWLEDGMENTS

The authors are grateful to Ivana Radnovic, Milka Marjanovic, Momcilo Tasic, Zoran Micic, and Milica Rakic for their help with realization and measurement. This work was supported by the Serbian Ministry for Science, Technologies, and Development. REFERENCES

1. K.-L. Wong, J.-W. Lai, and F.-R. Hsiao, Omnidirectional planar dipole-array antenna for 2.4/5.2-GHz WLAN access points, Microwave Opt Technol Lett 39 (2003), 33–36.

2. K.L. Wong, Planar antennas for wireless communication, Wiley, New York, 2003, p. 219.

3. M. Mikavica and A. Nesic, A, CAD for linear and planar antenna array of various radiating elements, Artech House, Norwood, MA, 1992. 4. H. Miyashita, H. Ohmine, K. Nishizawa, S. Makino, and S. Urasaki,

Electromagnetically coupled coaxial dipole array antenna, IEEE Trans Antenna Propagat 47 (1999), 1716 –1725.

5. A.D. Djordjevic, M.B. Bazdar, R.F. Harrington, and T.K. Sarkar, LIN-PAR, for Windows: Matrix parameters for multiconductor transmission lines, Software and user’s manual, Version 1.0, Artech House, Nor-wood, MA, 1999.

DC–12-GHz 10-dB GAIN SHUNT-SERIES

SHUNT-SHUNT WIDEBAND AMPLIFIERS

BY COMMERCIALLY AVAILABLE 0.35

␮M SiGe HBT TECHNOLOGY

C. C. Meng,1_{T. H. Wu,}1_{and G. W. Huang}2 1_{Department of Communication Engineering}

National Chiao Tung University Hsinchu, Taiwan, R.O.C.

2_{National Nano Device Laboratories}

Hsinchu, Taiwan, R.O.C.

Received 28 August 2003

ABSTRACT: The realization of wideband ampliﬁers with shunt-series

shunt-shunt dual-feedback conﬁguration with commercially available 0.35-␮m SiGe BiCMOS technology is reported. The SiGe HBT used here has ftof 67 GHz and BVceo of 2.5 V. The experimental results

show that power gain is 10 dB from DC to 12 GHz for a shunt-series shunt-shunt wideband ampliﬁer, with the help of the emitter capacitive peaking technique. Input- and output-return losses are better than 10 dB for the same frequency range. Noise ﬁgure increases from 8 to 12 dB for frequencies from 1 to 18 GHz. OP1dBand OIP3are 0 dBm and 12

Technol Lett 40: 518 –520, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20021

Key words: SiGe; HBT; ampliﬁers INTRODUCTION

Wideband amplifiers [1– 4] are used in a variety of modern com-munication systems. The Kukielka wideband amplifier is one of the most popular circuit topologies among all kinds of wideband amplifiers. The matched-impedance Kukielka wideband amplifier

is achieved by using a shunt-series shunt-shunt dual-feedback conﬁguration. In this work, SiGe HBT Kukielka wideband ampli-ﬁers are demonstrated by a commercially available foundry ser-vice. The 0.35-␮m SiGe BiCMOS process is very economical because it is fabricated using the inexpensive I-line photolithog-raphy technique instead of the expensive deep-UV technique, and even the phase-shift mask photolithography technique is used for feature length of 0.25␮m and below.

The circuit schematic of the designed shunt-series shunt-shunt SiGe HBT wideband ampliﬁer is shown in Figure 1. A Darlington pair is used in the second stage to improve the frequency response. The resistors Rf 1and Rf 2in Figure 1 are the global feedback and

local feedback resistors, respectively. The resistor R_{f 1}is shunting at input and Rf 2is shunting at output, in order to lower the terminal

impedance to 50⍀ for the terminal impedance matching. The emitter peaking capacitors Ce1and Ce2are shown in Figure 1. The

emitter capacitive peaking technique is used to overcome the Figure 1 Circuit schematic of the shunt-series shunt-shunt SiGe HBT wideband ampliﬁer

Figure 2 Die photo of the shunt-series shunt-shunt dual feedback SiGe HBT wideband ampliﬁer

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intrinsic over-damped frequency response of the shunt-series shunt-shunt wideband ampliﬁer and thus enhance the bandwidth [2, 5, 6]. The design principles of gain, bandwidth, and input/ output return loss have been well established [5] for the shunt-series shunt-shunt wideband ampliﬁer. Thus, 10-dB gain and in-put/output return loss of better than 10 dB are designed and demonstrated from DC to 12 GHz in this work.

MEASUREMENT RESULTS

Figure 2 illustrates the die photo of the fabricated SiGe HBT dual-feedback ampliﬁer. The SiGe HBT device used here has ftof 67 GHz

and BVceo of 2.5 V. The ampliﬁer has a coplanar ground-signal-ground pad to facilitate on-wafer probing. The size of all the SiGe HBT transistors in Figure 2 is 0.3⫻ 9.9␮m. The small emitter width reduces the intrinsic base resistance and intrinsic base-collector junc-tion capacitor for higher fmax. The die size is 0.7⫻ 0.7 mm. Most of

the die area is not fully utilized to facilitate the on-wafer measurement and the die size of the wideband feedback ampliﬁer can be easily compacted into 0.4⫻ 0.4 mm.

The ﬁrst stage consumes 3 mA and the second stage consumes 8 mA at 3.3-V supply voltage. Figure 3 shows the forward trans-mission gain, input-return loss, reverse transtrans-mission gain, and output-return loss for 3.3-V supply voltage. The shunt-series shunt-shunt dual feedback. SiGe wideband ampliﬁer has 12 GHz of 3-dB gain bandwidth, S₁₁ and S₂₂are below⫺10 dB for the measurement range from DC to 18 GHz, as illustrated in Figure 3 for 3.3-V supply voltage.

The rf performance of the same SiGe wideband ampliﬁer at 2.5-V supply voltage is also illustrated in Figure 4. The total bias current is 5 mA at 2.5-V supply voltage. The gain and bandwidth have been reduced to 8 dB and 8 GHz, respectively, as illustrated in Figure 4. Both bias conditions show that the terminal impedance matching is very good and the matching bandwidth is even higher than the 3-dB gain bandwidth.

Figures 5 and 6 illustrate the noise and power performances at both bias conditions. Noise performance is about one-half to one dB better at 3.3-V supply voltage. Noise ﬁgure increases from 8 to 12 dB for frequencies from 1 to 18 GHz at 3.3-V supply voltage. OP_1dBand OIP₃ of the wideband ampliﬁer, operating at 3.3-V supply voltage as a function of frequency, are illustrated in Figure 7. OP_1dBand OIP₃are 0 and 12 dBm at 1 GHz, respectively. Both OP1dBand OIP3 decrease when the frequency becomes higher.

OP_1dBand OIP₃become⫺9 and 3 dBm at 12 GHz, respectively. OIP3is about 12-dB higher than OP1dBfor the measured frequency

range. CONCLUSION

This work has demonstrated a 10-dB gain DC–12-GHz SiGe HBT shunt-series shunt-shunt feedback wideband amplifiers by using a commercially available 0.35-␮m SiGe BiCMOS foundry. The total current consumption is 11 mA at 3.3-V supply voltage. The experimental results show that power gain is 10 dB and input/ output return loss is below 10 dB from DC to 12 GHz for the wideband amplifier at 3.3-V supply voltage. Noise figure increases from 8 to 12 dB for frequencies from 1 to 18 GHz. Both OP_1dBand Figure 3 Measurement results of the SiGe HBT wideband amplifier with

Vcc ⫽ 3.3 V and Itotal⫽ 11 mA

Figure 4 Measurement results of the SiGe HBT wideband ampliﬁer with

Vcc ⫽ 2.5 V and Itotal⫽ 5 mA

Figure 5 Measured noise ﬁgures of the SiGe HBT wideband ampliﬁer

Figure 6 Measured power performance of the SiGe HBT wideband ampliﬁer at 3.3-V supply voltage

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OIP₃ are a function of frequency. OP_1dBand OIP₃are 0 and 12 dBm at 1 GHz, respectively. Both OP_1dBand OIP₃decrease when frequency becomes higher. OP_1dBand OIP₃ become⫺9 and 3 dBm at 12 GHz, respectively.

ACKNOWLEDGMENTS

This work was supported by the National Science Council of Republic of China under grant no. NSC 92-2219-E-009-023 and by the Ministry of Education under grant no. 89-E-FA06-2-4. The authors also would like to thank the Chip Implementation Center in Taiwan for providing chip fabrication.

REFERENCES

1. R.G. Meyer and R.A. Blauschild, A 4-terminal wide-band monolithic ampliﬁer, IEEE J Solid-State Circ SC-16 (1981), 634 – 638.

2. C.D. Hull and R.G. Meyer, Principles of monolithic wideband feedback ampliﬁer design, Int J High-Speed Electron 3 (1992), 53–93. 3. K.W. Kobayashi and A.K. Oki, A DC-10 GHz high gain-low noise

GaAs HBT direct-coupled ampliﬁer, IEEE Microwave Guided Wave Lett 5 (1995), 308 –310.

4. K.W. Kobayashi and A.K. Oki, A Low-noise baseband 5-GHz direct-coupled HBT ampliﬁer with common-base active input match, IEEE Microwave Guided Wave Lett 4 (1994), 373–375.

5. M.C. Chiang, S.S. Lu, C.C. Meng, S.A. Yu, S.C. Yang, and Y.J. Chan, Analysis, design, and optimization of InGaP-GaAs HBT matched-impedance wide-band ampliﬁers with multiple feedback loops, IEEE J Solid-State Circ 37 (2002), 694 –701.

6. C.C. Meng, T.H. Wu, and S.S. Lu, 28-dB Gain DC-6GHz GaInP/GaAs HBT Wideband Ampliﬁers with and without Emitter Capacitive Peak-ing, Euro Gallium Arsenide and other Semiconductors Appl Symp (GAAS 2002), 2002, pp. 311–314.

AN ENHANCED CAVITY MODEL FOR

MICROSTRIP ANTENNAS

Yeow-Beng Gan,1_{Chee-Parng Chua,}2_{and Le-Wei Li}2,3 1_{Tamasek Laboratories}

Singapore 119260

2_{Dept. of Electrical Computer Engineering}

National University of Singapore 10 Kent Ridge Crescent Singapore 119260

3_{HPCES Program}

Singapore-MIT Alliance Singapore 119260

Received 21 August 2003

ABSTRACT: An enhanced cavity model for analyzing microstrip patch

antenna is presented. The predicted resonant frequency and resonant resistance of the antenna are in good agreement with measured data. Theoretical results of the enhanced model are also compared with some commonly used models to determine their range of validity. © 2004

Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 520 –523, 2004; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.20022

Key words: cavity model; microstrip antennas; antenna analysis 1. INTRODUCTION

A conventional microstrip antenna is usually comprised of a me-tallic patch deposited on one side of the substrate and a ground plane on the other side. Over the years, many models [1– 6] have

been used to analyze microstrip patch geometry. Among them, the cavity model with perfect magnetic conducting (PMC) walls has been useful in providing insight regarding the radiation mecha-nisms of microstrip patch, but has also provided inaccurate pre-diction of its resonant frequent and resonant resistance. In this model, the thickness t of the microstrip patch antenna’s substrate has been assumed to be electrically thin (usually on the order of 0.01␭0) and a low dielectric constant has been used. These two

assumptions made by the analytical models no longer hold because the microstrip patch antenna is increasingly used in the millimeter-wave region. To achieve miniaturization and larger bandwidth, thicker and higher dielectric substrate is also commonly used. Hence, a better analytical model or technique is needed to char-acterize the microstrip patch antenna.

2. ENHANCED MODEL

The enhanced cavity model is based on Carver and Coffey’s [2, 3] design equations formulated for microstrip patch resonator using the modal-expansion technique. In this approach, the patch is viewed as a thin TMz-mode cavity supporting quasi-discrete

TMmnmodes transverse to z, where m and n are the mode numbers

associated with the x and y directions, respectively. The ﬁeld between the patch and the ground plane is expanded in terms of a series of eigenfunctions with their corresponding eigenvalues. For a nonradiating cavity, these eigenvalues are positive and real and are deﬁned as kx ⫽ n␲/a and ky ⫽ m␲/b. For the cavity to

radiate, the interior fields must be related to the exterior fields. This is achieved by imposing impedance boundary conditions at the four walls by making use of fictitious complex wall admittances Yw to represent the external stored and radiated energy effects.

Consider a microstrip patch antenna (shown in Fig. 1) of resonant length b (⬇␭d/ 2) along the y direction and width a (⬇2b), the

following transcendental equation is obtained [3]:

tan共kyb兲 ⫽ 2ky␣y ky2⫺␣y2 , (1) where ␣y⫽ j 2␲␩0 ␭0 t aYwFy

冉

a b

冊

, Fy⫽ 0.7747 ⫹ 0.5977

冉

a b⫺ 1

冊

⫺ 0.1638

冉

a b⫺ 1

冊

2 .

The wall admittance Ywis multiplied by a factor Fyto take into

consideration the effect of the aspect ratio a/b on the accuracy of the mode vectors used to represent the actual ﬁeld distribution at the radiating edges. Better agreement between the predicted and measured results was found in comparison to Fy⫽ 1. The wall

Figure 1 Rectangular microstrip patch antenna used in the experiment