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Figure 6 demonstrate that the interinfluence among the resonators in the parallel structure is usually minor and negligible and the design process can be greatly simplified.The fabricated filter, the simulated results and measured results are shown in Figure 7. The filter is measured by Rohde and Schwarz's network analyzer. The center frequencies of the three passbands are 1.89, 2.58, and 3.51 GHz with insertion loss of 1.9, 1.7, and 1.8 dB. At 2.07, 3.15, and 4.77 GHz, three transmission zeros are generated by QWRs to improve the rejection outside the passbands.The proposed filter is fabricated on the substrate Rogers 5880 with relative dielectric constant e r 5 2.2, loss tan d 5 0.0009 and thickness h 5 0.508 mm. The geometry parameters are listed in Table 1. It has been proved that combining parallel structure with QWRs is a feasible method to design multipassband filters. The discrepancy between the simulated and measured results is mainly due to fabrication inaccuracy. CONCLUSIONIn this article, a new filter multipassband filter with multiple TZs is proposed based on the properties of QWRs and the parallel structure. The simulated results and measured results are in good agreement. The proposed filter has the advantages of low in-band insertion loss, great out-band rejection and compact size and the design process is relatively simple. This proposed filter can be applied in the GSM, 4G, WiMax, or multiprotocol wireless communication systems.

This article reports a high gain millimeter-wave substrate integrated waveguide (SIW) antenna using low cost printed circuit board technology. The half elliptic slots which can provide small shunt admittance, low cross polarization level and low mutual coupling are etched on the board surface of SIW as radiation slots for large array application. Design procedure for analyzing the characteristics of proposed radiation slot, the beamforming structure and the array antenna are presented. As examples, an 8 3 8 and a 32 3 32 SIW slot array antennas are designed and verified by experiments. Good agreements between simulation and measured results are achieved, which shows the 8 3 8 SIW slot array antenna has a gain of 20.8 dBi at 42.5 GHz, the maximum sidelobe level of 42.5 GHz E-plane and H-plane radiation patterns are 22.3 dB and 22.1 dB, respectively. The 32 3 32 SIW slot array antenna has a maximum measured gain of 30.05 dBi at 42.5 GHz. At 42.3 GHz, the measured antenna has a gain of 29.6 dBi and a maximum sidelobe level of 19.89 dB and 15.0 dB for the E-plane and H-plane radiation patterns.