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. The simulated radiation patterns with predicted pattern from Huygens-Fresnel principle and measured pattern are shown in Figure 5. The Eqs. (2) and (3) can be employed to predict the shape of main lobe and 3-dB beam width of radiation pattern, respectively. The difference of beam and side lobes ratio is measured to be 23 dB and 3-dB beam width is about 23.6°while the solution in (3) is 23.2°where percentage error is about 1.7%. CONCLUSIONA multifeed technique has been introduced to the oversize rectangular patch antenna to enhance antenna gain and suppress higherorder mode surface currents. High antenna gain of 10.9 dBi is achieved at 5.8 GHz. The radiation area is 34% smaller than the conventional microstrip patch array. A cavity model is built to predict the frequencies of higher-order mode resonances and a formula based on Huygens-Fresnel principle is deduced for 3-dB beam-with of proposed design. Narrow beam radiation with 3 dB beam-width of 23.6°is preferred to many communication applications such as radar systems and long distance communications. INTRODUCTIONDifferent wireless standards have been emerged into the communication industry for producing new consumer systems such as GSM, Bluetooth, WLAN, and WiMax. The increasing demand for these applications in the communication market has enabled a single wireless system to support multistandard operations [1, 2]. But with the rapid evolution of multiband and multiservice communication systems, filters with a multimode response become largely required. For example, the mobile phones use GSM operated at 900 MHz for voice calls, Bluetooth operated at 2.4 GHz for wireless short-distance data transmission, or WLAN operated at 5.8 GHz for internet access. The previous microwave filters are designed mainly on the dual-band features [3,4]. Recently, there are papers focused on the implementation of the triple-band filters [5][6][7][8]. However, the sizes of the microwave filters employ such triband patterns are considered too large to be utilized in the modem wireless and mobile systems. Thus, size reduction becomes an important issue in the design of microwave filters. DESIGN OF TRILAYER TRIBAND BANDPASS FILTERIn this article, a trilayer triband (TLTB) bandpass filter (BPF) is presented to be operated at 1.8 GHz GSM channel, 3.5 GHz WiMAX channel, and 5.8 GHz WLAN band. The structure of the proposed TLTB-BPF is shown in Figure 1. The proposed TLTB-BPF consists of three layers. Two separated transmission lines are The open-loop rectangular ring configuration is introduced in SIR to minimize the dimension and to generate two passbands of 1.8 GHz and 5.8 GHz on the bottom layer. The coupling paths are chosen specifically for each resonant frequency as shown in Figures 3(a)-3(c). The signal coupling path for 3.5 GHz is depicted in Figure 3(a). Figure 3(b) is the coupling path for 1.8 GHz and 5.8 GHz through DGS. Figure 3(c) shows the signal coupling path of TLTB-BPF. SIMULATION AND MEASUREMENT RESULTSThe features of the TLTB-BPF are simulated by a full-wave electroma...

An experimental receiver prototype operating over the S-, C-, and X-bands, based on a MHMIC multiport, is designed, fabricated, and measured. Comparative simulation and measurement results for 8PSK modulated signals are presented and discussed. The RF input power sweep and the DC offset of the proposed multiport demodulator are particularly analyzed.

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