TOPICS IN THE OPTIMIZATION OF MILLIMETER-WAVE MIXERS (MULTIPLIERS, TRANSFORMERS, SCHOTTKY DIODE)

This thesis is in three parts:;The accuracy of the program is demonstrated by comparing the computed and measured performance of a mixer {89} whose nominal operating frequency range is 140-220 GHz. Subsequent analysis of this particular mixer design indicates the sensitivity of its performance to various diode and mount characteristics.;II. In the second part of this thesis a computer program for the analysis of diode multipliers is presented. The program determines the conversion efficiency and the input and output impedances of a multiplier given the diode parameters and mount impedances at the pump harmonic frequencies. It is more general than previous analyses in that the diode may operate in either the reverse biased varactor mode or with substantial forward current flow where the conversion mechanism is predominantly resistive.;In addition, a design for a varactor diode doubler tunable over an output frequency range of 150-220 GHz is given. The electrical layout is based upon a device describe by Archer {1} but is simpler to fabricate. The doubler provides 10-20% and has an instantaneous bandwidth of > 3%.;I. In the first part a flexible user oriented computer program for the analysis of single-ended Schottky barrier diode mixers is presented. The program calculates the diode large signal current, voltage, capacitance and conductance waveforms and the small signal conversion loss, equivalent input noise temperature and intermediate frequency output impedance given the diode and mount characteristics.;III. The third part of this thesis contains a description and analysis of a new H-plane rectangular waveguide transformer. The transformer can be made quickly and easily in split-block waveguide using a standard slitting saw. It is particularly suited for use in the millimeter-wave band, replacing conventional stepped transformers which require the fabrication of a separate electroformed mandrel for each finished piece.;A theoretical analysis of the new transformer is given and good agreement is obtained with measurements made on transitions in X-band waveguide. Using the new transformer design it is shown that VSWR's of less than 1.2 can be obtained over a full waveguide band for impedance ratios as high as 4 to 1.