In this letter, a novel rectangular waveguide T-junction is proposed for power combining application. In order to achieve good isolation and port matching performances, a metallic strip probe is inserted into the junction through a window at the center of the waveguide side wall to couple even mode energy and a matched load is used to absorb the coupled energy. As it is independent of the junction, match load of high power-handling capability can be used meeting specific application requirements. A Ka-band T-junction prototype is designed and fabricated to validate the design concept. Measured results show that the insertion loss is less than 0.2 dB, the reflection is better than 17 dB and the isolation above 20 dB over the frequency range of 27 to 33 GHz.
A broadband transition from microstrip line to spoof surface plasmon (SP) waveguide is proposed. The transition transforms the guided wave into a spoof SP polariton in a broad microwave frequency band. A back-to-back transition sample is fabricated using the proposed method. Good agreement between the measurement and simulation is obtained. The measured results show an insertion loss <2 dB and a return loss below −11 dB from 2.2 to 10 GHz. The proposed broadband transition may pave a way for advanced conventional plasmonic integrated microwave devices and circuits.
A high Q-factor substrate integrated waveguide (SIW) cavity resonator and its application of X-band low phase noise oscillator is proposed. Complementary split-ring resonators are used to improve the Q-factor of the proposed resonator. The size of the resonator is reduced by using quarter-mode circular SIW cavity. The oscillator based on the proposed SIW cavity resonator can be easily designed and tested. Measured results demonstrate an output frequency of 10.11 GHz and a phase noise of −108.7 dBc/Hz at 100 kHz offset. The oscillator is also able to deliver an output power of 4.6 dBm and harmonic rejection of better than 30 dBc. The proposed oscillator is suitable for low-cost high-frequency systems.
A Q band sub-harmonic mixer with wideband radio frequency (RF) and high intermediate frequency (IF) is proposed. The mixer employs a short-circuited band-pass filter (BPF) and a RF-IF diplexer, which provide proper terminations for the IF, RF, and local-oscillator (LO) signals simultaneously, and reject the major unwanted mixing products. A Q-band subharmonic mixer is designed and fabricated. The measured results show that the proposed sub-harmonic mixer can operate from 40 to 50 GHz for RF and support up to 10 GHz for IF bandwidth. As a down-conversion mixer, the measured conversion-loss is less than than 10.5 dB over the available RF band, while the minimum conversion-loss is about 6.8 dB at an RF of 45 GHz and IF of 5 GHz. As an up-conversion mixer, the measured conversion-loss is less than 11 dB over the available IF band, while the minimum conversion-loss is about 7.5 dB at an RF of 45.5 GHz and IF of 5.5 GHz.
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