Abstract:A novel quarter mode substrate integrated waveguide (QMSIW) resonator is proposed, based on which a plane cascade QMSIW tunable filter is designed. Miniaturization of the filter is achieved, whose area is. The filter works at 1.2 GHz with the tunable range of 31.6% and the fabricated insertion loss less than 1.9dB and return loss greater than 15dB, respectively.
A double-Orbital-Angular-Momentum (OAM)-mode microstrip antenna is designed, simulated, fabricated and measured, which generates OAM with mode number l = 2 and 3 on 5 GHz by two resistor loaded microstrip rings respectively. For existing OAM antennas, structures like circular array, parabolic reflector and electromagnetic meta-surface are widely adopted, which are electrically large and hard to be integrated. However, the proposed antenna has a compact size and a low profile, which can be integrated in RF circuit as a component. To solve the problem of low gain in microstrip OAM antenna, parameters are optimised and a top dielectric layer is adopted, and its measured peak gain reaches 1.5 dB for l = 2 and 1.8 dB for l = 3. The measured frequency band, on which a near field vortex phase is observed and orbital angular momentum is generated, is 4.65-5.25 GHz for l = 2, and 4.5-5.2 GHz for l = 3. Besides, this antenna can multiplex more OAM modes by adopting more microstrip rings.
In order to improve the utilization of spectrum resources, dynamic frequency allocation technology has become a method of spectrum saving. The research of electric tunable filter has received much attention in recent years. Substrate integrated waveguide (SIW) is a new technology of microwave integration in the field. The innovation of this article is to combine the SIW miniaturization technology with tunable technology. In this article, a miniaturized symmetrically folded substrate integrated waveguide (SFSIW) filter is designed. Based on the miniaturization of SIW filter, the center frequency can be adjusted electrically and the measured data show that the tunable filter can achieve eight states under the condition that the bandwidth below −3 dB remains approximately constant 300 MHz. The center frequency varies from 3.23 GHz to 3.9 GHz. The range of the filter's insertion loss is 1.2 dB to 2.04 dB, and the return loss is higher than 20.9 dB. This filter has practical value in the electronic countermeasures of military communication.
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