This paper presents a compact microstrip triple-mode filter with enhanced skirt characteristics. The presented triple-mode filter configuration supports three transmission poles and three transmission zeros within the nearby passband. Two of transmission zeros are generated by a triple-mode resonator itself, and the third one is generated by small cross-couplings between the I/O ports. Each resonance condition and the transmission zero generation conditions are analyzed using an equivalent circuit. The bandpass filter is designed for a 2.4 GHz WLAN. The filter was fabricated with a relative dielectic constant of 3.5 and a thickness of 0.76 mm. The fabricated filter has a small size (7.9 mm×7.2 mm, i.e., 0.107 λg×0.098 λg, where λg is guided wavelength at a center frequency) and shows high performing skirt characteristics.

In the frequency range 13-17 GHz, the measured mutual coupling parameters between adjacent elements are less than À27 dB which is 12 dB lower than its counterpart of the conventional LTSA. Those results indicate that the chock slots suppress the mutual coupling between LTSA elements. This advancement is very vivid when observing the simulated current distribution of the proposed LTSA. As shown in Figure 6, in the outside region of the radiation arm, the currents along x direction are significantly degraded comparing with Figure 3. In the region between the bases of the adjacent elements, the currents directly flowing into other ports are also attenuated by the slot. MEASURED RESULTS AND DISCUSSIONA real three-port antenna is fabricated and measured. As the measuring instrumentations are in 50-X coaxial system, the antenna is fed by SMA connector and four via holes [8,9] is introduced to improve the impedance matching performance. However, such a structure cannot match the antenna to the coaxial system in the entire 13-17 GHz band and that is why we use the parameter C i2 instead of S-parameter.The photograph of the antenna is shown in Figure 7. The simulated and measured S 22 and C i2 of the modified LTSA are plotted in Figure 8. The measured C i2 are in general agree with that of Figure 5, which is fed by a wave guide port. These results validate that the mutual coupling of the antenna is significantly decreased.The measured realized gain patterns within its operating band of the proposed antenna are plotted in Figure 9. The patterns are measured when Port 2 is fed and the other ports are connected to matched loads. It shows that the realized gain levels are larger than 7.1 dBi. CONCLUSIONSA modified SIW-feeding LTSA is developed. By cutting slots on the radiation arms and in the middle of two adjacent radiation elements, the mutual coupling levels of the LTSA are reduced below À27dB.ABSTRACT: A compact microstrip dual-band bandpass filter (DBBPF) with controllable bandwidth for each passband is proposed. Each passband is independently designed using two different dual-mode resonators. The proposed DBBPF has three transmission zeros. Two transmission zeros are generated by each dual-mode resonator. An additional transmission zero is generated by input/output port coupling. The DBBPF application is designed for 2.4/5.7 GHz WLAN. Experimental measurements are presented to validate the theory.ABSTRACT: Rotation of left-handed materials (LHM) is presented as tuning technique in this article. For verification of proposed idea, Sshaped resonator and its two modified cases are chosen as LHM. The frequency bands of these resonators are determined experimentally with and without rotation. The comparison of results justifies the tuning technique.

A novel and simple design of a film type inverted F‐antenna for global system for mobile (GSM), digital cellular system (DCS), personal communication system (PCS), US personal communication system (USPCS), and wideband code division multiple access (WCDMA) bands is proposed. The obtained impedance bandwidths reached 87 (880–967) MHz and 451 (1710–2162) MHz in the GSM, DCS, PCS, USPCS, and WCDMA bands. For multiband operation, a modified meander line structure with L‐shaped short pin was used. The measured peak antenna gains for the operating frequencies were 3.18–4.24 dBi. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2757–2762, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27195

A novel structure of a compact microstrip dual‐mode resonator is proposed for a dual‐mode filter application.The proposed dual‐mode resonator is miniaturized using an interdigital capacitor and stepped impedance structure. In addition, the proposed dual‐mode resonator provides two transmission zeros in the stopband. The dual‐mode filter application is designed for 2.4 GHz wireless local area network (WLAN) with three transmission zeros. An additional transmission zero is generated in the filter application using a cross coupling capacitor between input/output ports. Experimental measurements are also presented to validate the theory. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2368–2371, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26279

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