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Two wideband bandstop filters (BSFs) for single and dual-band are proposed and then extended to reflectionless BSFs based on the analysis from input impedance/admittance perspective. Also, topologies of higher-number-stopband input-reflectionless BSF are provided to broaden the design scope. Open/shorted coupled lines are adopted to obtain multi transmission zeros and desired stopband bandwidth by adjusting the even-/odd-mode impedance of coupled lines. Resistor-loaded coupled lines are connected with Port 1 to absorb unwanted signals and obtain input-reflectionless behavior. For validation of the proposed theory analysis, BSFs with corresponding absorptive prototypes are constructed and measured. [ABSTRACT FROM AUTHOR]

In this paper, low-profile compact microstrip magnetic dipole antennas with large beamwidth and broad bandwidth are proposed for vehicular applications. At first, by introducing a strip on the bottom layer of microstrip magnetic dipole antenna, the electric current sources are introduced for the enhancement of beamwidth together with the magnetic current source. The operation principle of an equivalent complementary source model is then revealed to provide a physical insight. As seen, the half-power beamwidth (HPBW) can be controllable and effectively enlarged by the electric length of the planar magnetic dipole antenna. Next, by using a stub crossing on the strip, the impedance bandwidth is significantly improved comparing with the unloaded counterpart. After that, the antenna size is miniaturized by etching a pair of slots to extend the length of current path. Experimental results indicate that, under a very low profile of 0.016λ0 and 0.032λ0, the antenna prototypes can still achieve an impedance bandwidth of 14.5% and 20.8%, and a maximum HPBW of 99° (E-plane)/180° (H-plane) and 112° (E-plane)/159° (H-plane). It is also demonstrated that when the antenna size is reduced to 0.442λ0×0.284λ0, the impedance bandwidth up to 14.9% and the maximum HPBW of 93° (E-plane)/231° (H-plane) can be guaranteed with a low profile about 0.032λ0. Comparing with other design approaches, the proposed designs feature a very low profile structure, and superior beamwidth and bandwidth properties, as well as simple configuration and compact size. [ABSTRACT FROM AUTHOR]

In this letter, a millimeter-wave (mm-wave) dual-band bandpass filter is proposed with large bandwidth ratio by using gallium arsenide (GaAs)-based integrated passive device (IPD) technology. To realize small chip size, one dual-mode on-chip resonator is designed by using quasi-lumped capacitors and microstrip lines. In addition, multiple transmission zeroes are generated by further introducing both the electric and magnetic couplings between adjacent resonators. To realize large bandwidth ratio of two passbands, the external quality factors are investigated at both passband, and can be independently controlled. For demonstration, a 28-/50-GHz dual-band bandpass filter is designed, fabricated, and measured. The fractional bandwidth ratio is 7.8, which is much larger than the reported on-chip filters. Meanwhile, very low insertion loss of 0.58-dB is realized for the lower passband at 28 GHz, indicating the proposed dual-band bandpass filter a promising application in mm-wave wireless systems. [ABSTRACT FROM AUTHOR]

A novel filtering method based on the metasurface antenna (MSA) with radiation nulls is proposed without loading extra circuits. Due to the specific multiunit structure of MSA, the filtering method is first realized on each radiating metasurface (MS) unit by introducing a multifolded U-shaped slot and a defected ground structure to generate lower edge radiation nulls. Meanwhile, coplanar parasitic patches are loaded around the MS units to provide upper edge nulls and simultaneously introduce extra in-band resonances for wide passband. Thus, a low-profile, wideband, and high-gain filtering antenna is readily constructed. To verify the concept, a prototype with a low profile of only $0.04\lambda _{{0}}$ is designed and fabricated. The simulated and measured results agree well, demonstrating a good performance with large impedance bandwidth of about 20%, high average gain of 8 dBi, and high aperture efficiency of about 90%, together with high out-of-band suppression levels of about 20 dB. In addition, the radiation patterns are symmetric in both the E- and H-planes with cross-polarization suppressions of over 20 dB. Compared with the reported filtering antennas, the proposed filtering MSA can achieve the wideband filtering response in a low profile, as well as high gain with high aperture efficiency. [ABSTRACT FROM AUTHOR]

Half-mode substrate integrated waveguide (HMSIW) switchable unit, built by HMSIW section with loaded single or multi-microstrip shunt stub(s), was proposed in this work. Both shorted and opened stubs were studied, investigated and compared, bandwidth enhancement method for proposed switchable units was proposed and demonstrated. Based on these switchable units, narrowband and broadband HMSIW single-pole-single-through (SPST) switches, SIW SPST switch and SIW/HMSIW-based single-pole-double-through (SPDT) switch were designed, fabricated and measured. Good performances were observed experimentally for these proposed circuits, showing the advantages of proposed concept and an excellent candidate for switchable or reconfigurable SIW/HMSIW circuits or systems. [ABSTRACT FROM AUTHOR]