Full-wave design and optimization of mm-wave diode-based circuits in finline technique

This paper presents a full-wave design and optimization of a quasi-planar f requency doubler and a balanced subharmonic mixer in finline technique by a pplying the extended finite-difference time-domain (FDTD) method. The struc tures are based on the junction of a coplanar waveguide and a finline using two Schottky diodes mounted across this junction. The diodes are represent ed by their large-signal device circuit model. The specific problem of embe dding the lumped elements In the FDTD mesh at millimeter-wave frequencies i s discussed. A new method for the inclusion of the device into the grid is developed, avoiding nonphysical reactances, The frequency doubler is design ed for optimal conversion loss at 0-dBm input power in a frequency band fro m 20 to 25 and 40 to 50 GHz, respectively, With the subharmonic mixer, matc hing structures at both the local-oscillator (LO) port and the radio-freque ncy (RF) port have been employed so that a conversion loss of 14.8 dB could be achieved with only 5-dBm LO power. The operation frequencies are 18 GHz for the LO and 56 GHz for the RF. The simulation results are validated by measurements.