Wideband CPW-fed slot antenna for DCS,
PCS, 3G and Bluetooth bands
J.-Y. Jan and C.-Y. Hsiang
A novel CPW-fed wide planar slot antenna with an asymmetrical slot is proposed. The asymmetrical slot is square-like with the same widths but different lengths at the sides. By choosing suitable lengths of this asymmetrical slot, broadband operation can be obtained. From experi-mental results, the measured impedance bandwidth, defined by 10 dB return loss, can reach an operating bandwidth of 2136 MHz with the centre frequency operating at 2610 MHz for applications to various wireless bands. In addition, the measured radiation patterns within this wide impedance bandwidth have the same polarisation planes and similar radiation characteristics. Each antenna gain within the applica-tion bands can be less than 1 dB.
Introduction: To cover more wireless communication services, there is strong demand for antennas operating at a broadband range. Therefore, in antenna design, various configurations have been presented to enhance operating bandwidths. Among these designs, the slot antenna is a good candidate owing to its wide impedance bandwidth, simple structure, low cost and ease of construction. Many wideband slot antennas[1–6]have been studied. As reported in[1]and[2], the complicated feed network and L-shaped horizontal and vertical tuning stub are used. Moreover, other proposed slot antennas, such as in[3]and[4], with the fractal slot and the 3-D slot loop, respectively, have been demonstrated. Also, some slot antennas with hybrid slots[5, 6]have been presented for broadband operation. However, the proposed broadband slot antennas among these designs obviously have complicated antenna configurations that lead to a high complexity level regarding antenna design and fabrication.
In this Letter, a novel CPW-fed planar slot antenna is proposed. By employing the simple slot configuration and the CPW feed line, the wideband operation can be obtained. The performance of the antenna is confirmed experimentally.
Fig. 1 Geometry and dimensions of CPW-fed planar slot antenna with asymmetrical slot
Antenna design and experimental results: Fig. 1shows the geometry and dimensions of the proposed CPW-fed slot antenna. The proposed antenna consists of a simple slot with the same widths, W, and different lengths, L1and L2, that is printed on an inexpensive FR4 substrate of
thickness h ¼ 1.6 mm and relative permittivity er¼4.4. A 50 O CPW
feed line having strip width of 6.37 mm and distance gap of 0.5 mm is used. This CPW feed line has a simple tuning stub with a straight length of LSmm, which is printed on the same side of the microwave
substrate. For design simplicity, the width of the tuning stub is chosen to be the same as that of the CPW feed line. By choosing a proper asymmetrical slot with different lengths, the broadband operation can be obtained. Simulated results from the simulation software HFSS show that slot antennas with various asymmetrical slots should require their related tuning-stub lengths for impedance matching.
Fig. 2 Measured and simulated results of return loss against frequency of antenna with L1¼W ¼ 40 mm, L2¼32 mm, LS¼27 mm shown inFig. 1
Fig. 3 Measured return loss against frequency for antennas with L1¼
W ¼ 40 mm and various parameters of L2and LSshown inFig. 1
Fig. 4 Measured radiation patterns for proposed antenna studied inFig. 2
a 1800 MHz b 1900 MHz c 2000 MHz d 2450 MHz
