Q-band (33~50 GHz) is located at the low frequency band of millimeter-wave. With the advantages of wide bandwidth, strong anti-interference ability and strong penetrating power, Q-band becomes an idea candidate for high data rata wireless communication, satellite remote sensing and radar detection systems. Q-band transceiver (mainly includes the oscillator, mixer, filter, and power amplifier) is one of the key components of the system, which directly determines the performance of the system. Q-band transceiver and devices have been researched for several years in the developed countries. However, they are mainly used for military purposes, and Q-band devices are strictly controlled. With the development of communication standard Q-LINKPAN, the research on Q-band devices has grown rapidly in recent years in China, but these devices are still not ready for commercial use. In this dissertation, the study on the key circuits of Q-band transceiver is carried out according to the processing level in China. This dissertation is focused on the study of circuits with characteristics of high performance, low cost, and easy for integration. The main research contents in this dissertation are listed as follows:
(1) The study on Q-band finline, microstrip, and SIW compact band-pass filters is presented. For further reduction of size, a periodically loaded wide band finline filter is designed. Measurements show that the proposed structure maintains the RF performance and achieves size reduction of about 20%. A microstrip filter composed of parallel coupled lines, multi-mode resonators and open stubs is presented. The filter has a high performance and low requirement of processing capacity. A compact electric coupling structure of substrate integrated waveguide (SIW) bandpass filter is studied.
(2) A new type stepped-impedance coupled microstrip resonator is proposed. High frequency selectivity is obtained because of the two transmission zeros produced by the coupling between high and low impedance lines. Dual-mode structure is introduced into the resonator for further size reduction. The low-pass filter using the proposed resonators obtains a sharp roll-off skirt and wideband stopband characteristics.
(3) A K-band wideband mixer using cascaded rate-race hybrid is studied. Measurement results show that the conversion loss is less than 11 dB in the IF frequency band of DC~6 GHz with the LO frequency at 17 GHz, and the conversion loss is less than 10 dB in the RF frequency band of 17~25 GHz while the IF frequency is fixed at 1 GHz. Moreover, the mixer possesses good port isolation.
(4) Two kinds of wideband millimeter-wave sub-harmonic mixers are presented. To improve the mixing efficiency, a novel short-circuited band-pass filter is proposed and used at the LO port to recycle the idle mixing products. The measurements show that the relative RF frequency bandwidth is more than 22% and the IF frequency can be up to 10 GHz. For further improving of the working bandwidth, a novel wideband short-circuited band-pass filter is used at the RF port. The measured results show that the relative bandwidth is more than 54% for RF frequency and the IF frequency bandwidth can support up to 6 GHz.
(5) To solve the problem that the traditional millimeter-wave odd-harmonic mixer is difficult to integrate with planar circuits for its three-dimension, a Q-band third-harmonic mixer using the SIW balun is proposed. The measured results of the mixer show that the conversion loss is less than 15.6 dB over the RF frequency band of 38~47 GHz with the IF frequency fixed at 2 GHz. Furthermore, the conversion loss is less than 16 dB over the IF frequency bandwidth up to 6.4 GHz with LO frequency fixed at 13 GHz.
(6) Series feedback low phase noise oscillators are proposed using the CSRRs loaded circular SIW cavity and quarter-mode circular SIW cavity. Moreover, a dual mode band-pass filter based on the CSRRs loaded SIW cavity is used to design an X band parallel feedback low phase noise oscillator. The measured results of the fabricated oscillator demonstrate an output frequency of 10.113 GHz and a phase noise of -122 dBc/Hz at 100 KHz offset. For further reduction of the phase noise, the high order mode cavity with high Q factor and dual feedback topology are studied based on the previously designed series feedback oscillator.
(7) None 2n units millimeter-wave power combining technologies as traveling-wave and radial waveguide power combining are studied and Q-band six-way power combiners are designed and measured to validate these techniques. A novel rectangular waveguide T-Junction with high port isolation is proposed and a three-way waveguide directional coupler employing 90° waveguide phase shifter is designed for power combining application. A Q-band six-way power combiner composed of the proposed T-junction and new three-way directional coupler is designed and measured. The Q-band power combiners in this paper show advantages of low insertion loss, easy processing, and convenient installation.
(8) Investigation of Spoof Surface Plasmon Polariton (SSPP) in microwave and millimeter-wave applications is presented. A wideband transition from SSPP waveguide to microstrip line is proposed. Measured results show that the transition has a relative bandwidth of more than 127%. Electromagnetic (EM) signals on planar SSPP transmission lines have better propagation performance than those on microstrip lines with the same size and separation to the shielding box are demonstrated theoretically and experimentally. A Q-band switch based on the low-pass characteristics of SSPP transmission line and phase shifter composed of varactor diodes and SSPP transmission line are designed. To the best knowledge of the authors, this is the first time that the SSPP transmission line has been applied to the design of functional circuits.