Short-millimeter wave solid-state frequency multipliers and mixers are crucial components in communication, radar, test instrument, electronic countermeasures (ECM) and many other broadband application systems. Their broadband frequency response characteristics play a decisive role in the whole system performance. Aiming at solving the problem of power nulls in broadband Schottky diode based frequency multipliers and conversion peak point in broadband Schottky mixers, with the purpose of realizing cost-effective and high performance broadband frequency multipliers and mixers based on the accurate and broadband Schottky diode model, main factors affecting the broadband frequency response characteristics of frequency multiplying and mixing circuit have been studied in depth in this dissertation. Effective methods of analysis have been proposed and applied to develop broadband frequency multipliers at W-band, D-band and G-band and sub-harmonic mixers at W-band. The main achievements of this dissertation are as follows:
1. High-cost device has become the main problem that restricts its development in the popularization of short-millimeter wave multichannel array systems such as high resolution imaging radars. In order to develop high performance frequency multipliers and mixers with cost-effective Schottky diodes, accurate and broadband diode models of MA4E1310 delivered by MACOM and DMK2308 from Alpha Industries, Inc. have been established. The package parasitic effect of diode material is considered based on the software HFSS combined with ADS. Simulated and measured output power of two prototype multipliers developed based on the established diode models are in good agreement in the band of 50~110GHz, which verifies the precise of these two diode models. This work provides an important foundation for the subsequent design and optimization of short-millimeter wave broadband frequency multiplier and mixer circuits.
2. An effective analysis method for output power nulls in millimeter wave broadband frequency multipliers based on full-wave electromagnetic simulation of transmission notch is proposed. Fundamental signal from the RF input port to Schottky lumpports and the harmonics from Schottky lumpports to RF output port are analyzed by utilizing full wave 3-D electromagnetic passive circuit model and accurate broadband diode model. Key circuit parts and their dimensions that result in power nulls are calculated and intuitively analyzed. The relationship between the simulated transmission notches and measured power nulls are verified by the experimental test. The proposed method can be used to quickly remove the power null in working frequency band and provide an effective design and optimization method for short-millimeter wave broadband frequency multiplier and mixer circuits.
3. In order to improve the characteristic of W-band frequency triplers at upper end of the full frequency band, extraction method of impedance parameters is improved based on traditional ‘de-embedding method’ by including mounding pads between the properly specified reference planes. Aiming at Schottky based circuit design, the package of the diodes, mounting pads (microstrip ends upon which the diodes are mounted) as well as their adjacent cavity region are treated as an independent sub-region and then analyzed by an improved method to extract the equivalent impedance parameters of the sub-region. The effects of the dimensions of the pads, the mounting height as well as the dimension of shielding cavity on the performance of the input and output impedance over a broad frequency band are investigated in depth. Utilizing the power null analysis method based on transmission notches, the fundamental and harmonic transmission notches are analyzed and a full band W band passive tripler is designed and optimized. A prototype of the tripler has been fabricated and tested. With an input driving power of about 20dBm at Ka-band, the tripler delivers about 5 dBm output power with a variation of less than ±1.25 dB across 75~110 GHz frequency range. Furthermore, corresponding simulation analysis and experimental study on the anti-parallel diode pair of MA4E1310 and DMK2308 also made. The above measured results verify the effectiveness of the proposed circuit optimization design method.
4. In order to improve power capacity of Schottky diode based solid-state frequency multipliers in short millimeter wave, full wave analysis method are proposed based on a divider/combiner unit of two parallel diodes combined with mounting pads. Integrated simulation analysis technology of full wave 3-D electromagnetic passive circuit model combine with distributed accurate Schottky multi-anode diode model is utilized. The pads’ dimension and distance between them can be calculated under optimizing goal of broadband high power division and harmonic synthesis efficiency, D band and G frequency broadband doubler are developed and tested. With an input driving power of about 20 dBm, the D-band douber delivers an output power of 2.0~7.0 dBm over the bands of 135~160GHz band, 6±1 dBm across the band of 140~152 GHz, the G-band doubler delivers an output power of 0.5±2.5dBm across the band of 166~188GHz with an input driving power of about 17dBm.
5. In order to solve the problem of complicated analysis and formula in the design of traditional waveguide multi-apertures coupler, a fast and effective approach to the design of waveguide directional couplers based on equally distributed identical circular apertures is proposed. Two prototypes of full-band 10 dB and 8.5dB W band couplers are designed and fabricated, the measured performance of the couplers, such as the flatness of the coupling coefficient, the additional loss and other parameters, verifies the effectiveness of the proposed design method. In order to realize a flat characteristic and full-band W-band waveguide-antipodal finline-mircostrip, metalized through-hole is used to suppress high electromagnetic modes, and the influence of key dimension parameters of metalized through-hole on the frequency response characteristic curve of transmission line is analyzed. The experimental samples of back-to-back waveguide-antipodal finline-mircostrip transmission line are developed with different lengths. The flat transmission performances in W-band of the waveguide-antipodal finline-mircostrip are evaluated by experiments in back-to-back configurations.
6. Based on comprehensive analysis of coupling efficiency of mixer’s local and RF signal from input port to mixer Schottky lumpports, analysis and solution method of conversion loss peak points in short millimeter wave broadband subharmonic mixer is proposed based on full wave analysis technology of transmission coefficient. According to the simulation analysis, the transmission notches of the local and RF frequency signal to Schottky lumpports result in peak points of frequency conversion loss. Based on the accurate DBES105a and MA4E1310 Schottky diode model combine with their anti-parallel configuration diode pair circuits, the optimization design and experimental study of the W-band harmonic mixer with two different circuit topology structures have been done by removing the working band transmission notches. The measured results show that the frequency conversion loss of the DBES105a Schottky based mixer is 12.5±2.5dB over 85~108GHz RF frequency band, and the conversion loss of the mixer based on MA4E1310 Schottky in the RF frequency range of 80~100GHz is 16.5±2.5dB. The results of the test are in good agreement with the simulation results, which shows the correctness and effectiveness of the proposed analysis and design method.