Investigations On Microwave And Millimeter Wave Passive Devices With High Performance

The modern broadband microwave and millimeter wave satellite and ground wireless communication systems are expanding rapidly, which require cost-effective technologies suitable for mass production and high density integration. The major limiting components of systems are passive devices which have been designed based on waveguide technologies. The dual-mode circle cavities (DMCCs) attract much attention for high performance filter/diplexer applications due to their better selectivity, smaller size and less mass than conventional single-mode cavities. However, these designs still suffer from disadvantages such as being bulky, costly, difficult to fabricate, and incompatible with planar integrated circuits. Meanwhile, the design passive circuits is on ever developing stage in the world, and still need to accumulate a lot of experience. Aiming at the advanced V-band WPAN and Q-LINKPAN systems as well as satellite communication, this dissertation investigates several outstanding techniques to design the high selectivity bandpass filters (BPFs) using a novel small perturbation. The millimeter wave filters/diplexers prototypes as well as microwave oscillators/VCOs have been designed and fabricated using both of the air-filled waveguide and SIW technologies. This dissertation is based on the author’s research under supporting of the Specialized Research Fund for the Doctoral Program of Higher Education. The main researches of this dissertation are following:1) The designed V-band multi-pole BPFs have been fabricated by using the miller machining technology. In the two-pole single-DMCC filter, a controllable transmission zero (TZ) is generated at below slope of passband. Meanwhile, the measured results of the four-pole dual-DMCC filter shows that two TZs which are individually controlled by the perturbation notches are located at both of passband slopes. The performance of this dual-DMCC filter including the expanded fraction bandwidth (FBW) of 2.5%,1.35 dB insertion loss at 64.8 GHz center frequency, return loss smaller than -20 dB and out-of-band rejection about 65 dB, is more improved than that in single-DMCC filter. The proposed techniques are promising to design improved selectivity quasi-planar filters. The relative research result was published by Journal of Infrared and Millimeter Waves.2) According to investigations on selectivity-improved BPFs above, the V-band high performance diplexer is designed. The measured lower-channel BPF have two controlled TZs located at 57.4 GHz and 63.3 GHz at both side of passband, while those of the upper-channel BPF located at 62.1 GHz and 68.8 GHz, respectively. Especially, such the diplexer has been achieved an extremely high channel-to-channel isolation about 70 dB. The proposed diplexer based on the waveguide technology has the advantages of quasi-planar structure, advanced isolation without any mechanical tuning element in post-fabrication. The relative research results were published by IEEE Microwave and Wireless Components Letters.3) The alternative perturbed-DMCC filters using SIW technology have been presented. A perturbing via-hole is placed inside SIW DMCC to improve the filter selectivity. A couple of Q-band SIW-based DMCC BPFs has been fabricated on the Rogers5880 with a thickness of 0.254 mm using the standard PCB process. The measured highlight values of the dual-DMCC filter are 1.74 dB real insertion losses and a 40 dB out-of-band rejection, which along with improved selectivity are better than those in single-DMCC filter centered at 39.5 GHz. The relative research results were published by IEEE 2015 Asia-Pacific Microwave Conference.4) Employing investigated SIW filter prototypes for implementing the X-band oscillators is presented. The phase noise (PN) of designed oscillators are minimized by taking advantage of the group delay peak generated at left-side of the filter passband, which improved by properly adjusting the perturbing via-hole position inside the DMCC. Two X-band oscillators have been fabricated on the Roger 5880 substrate with SiGe:C HBT transistors. As the results, at 1 MHz frequency offset the measured PN of the single-DMCC oscillator is -127.7 dBc/Hz. The double-DMCC oscillator operates with the minimized PN of -135.4 dBc/Hz and the calculated FOM of -204.4 dBc/Hz, which are better than those in single-DMCC oscillator. The proposed oscillators have many advantages of simple design process, high stability and the minimized PN. These oscillators will be very useful in cost-effective communication and Doppler radar systems. The relative research results have been submitted in IEEE Microwave and Wireless Components Letters.