Research On The Key Technologies Of RF Integrated Front-end

RF integrated front-ends have broad application in wireless communications, military radar, energy, biological medicine, safety protection, space remote sensing, astronomical observation, and other related fields. As spectrum resources in low microwave frequency band become increasingly tense, the demand of RF front-end systems turns to higher millimeter-wave and submillimeter-wave bands. The millimeter-wave and submillimeter-wave RF systems have wider bandwidth, higher resolution and smaller volume, researchers from all over the world are involved into related technical researches to explore the wide bandwidth resources.Submillimeter-wave has a huge potential in the application of high speed wireless communication, radar, and other fields because it’s own properties and broadband spectrum resources. Submillimeter-wave RF front-end, as the basic hardware platform for realizing submillimeter-wave signal transceiver, is a comprehensive integrated technology which involves frequency conversion and energy transformation among microwave, millimeter-wave and submillimeter-wave frequency bands, playing a vital role in promoting the application of submillimeter-wave technology. According to the application requirements, several key technologies of RF front-end systems including submillimeter-wave HEMT device model, millimeter-wave power combing/dividing and millimeter-wave frequency multiple source are investigated and presented in this dissertation, providing theoretical and technical basis for the circuit integration of whole submillimeter-wave front-end transceiver system. The detailed research work of this dissertation is summarized as follows:1. Based on the working principle of the HEMT device, reasonable small signal equivalent circuit model is proposed to predict the performance of HEMT and the extraction method for model parameters is analyzed. Building HEMT model directly at high submillimeter-band become extremely hard due to the high errors and poor repeatability in S-parameters measurement, the extrapolation method is presented to address this problem. By employing the transistor cut-off frequency and maximum oscillation frequency as new constraint parameters, the accuracy of extrapolation model can be achieved. Two groups of measured S-parameters of HEMT devices are used to verify the validation of the presented extrapolation method.2. Studying on the transitions between rectangular waveguide(WG) and planar transmission lines, the broadband and multi-way millimeter-wave waveguide power combiners are presented. The novel kinds of broadband WG-to-stripline(SL), WG-to-suspended stripline(SSL), WG-to-ground coplanar waveguide(GPCW), WG-to-substrate integrated waveguide(SIW) are proposed, and the WG-to-GPCW transition is employed to obtain broadband two-way waveguide combiner. In addition, a broadband four-way millimeter-wave power combiner using compact WG-to-SIW transition is proposed and can be applied in the design of high output power amplifier module.3. Several types of waveguide power dividers with excellent performance are implemented. The high isolation, broadband feature of planar dividers combining with broadband transition circuits are explored together with ways to achieve high isolation, wide-band millimeter-wave waveguide power dividers in this dissertation. The proposed E-plane dividers have been designed to implement the in-phase and out-of-phase responses, while the traditional E-plane waveguide divider can show out-of-phase characteristic only. Due to this novel design, the dividers can provide more flexibilities for the practical applications. In addition, the proposed in/out phase dividers show the characteristics of broad bandwidth, high isolation, and good ports matching performances.4. A low-phase noise millimeter-wave frequency source is presented. As for oscillator, a low-phase noise oscillator employing a substrate integrated waveguide(SIW) dual-mode bandpass filter as the frequency stabilization element within its feedback loop is proposed. By adjusting the resonant frequencies of the two degenerate modes(TE102 and TE201) together to obtain a larger group delay in the passband edge of dual-mode filter, the phase noise of the oscillator is significantly improved due to the novel design of large group delay peak. In addition, two diplexers are cascaded back-to-back to realize two loop sub-oscillators so that a concurrent dual-band oscillator is implemented. The channels of the two sub-oscillators are isolated from each other, which help to suppress the interactions between the two output frequencies. The power combining technique presented is used to improve the output power level of millimeter-wave frequency tripler. To implement the millimeter-wave frequency source, the low phase noise oscillator and millimeter-wave frequency tripler are integrated to output high quality millimeter-wave signal. The measruemnts are carried out to verify the good phase noise performance of the presented millimeter-wave frequency source.