How do I design a frequency converter for a satellite ground station operating at Ka-band?

A frequency converter for a Ka-band satellite ground station translates the signal between the Ka-band RF frequency (17.7-21.2 GHz for receive, 27.5-31 GHz for transmit) and an intermediate frequency (IF, typically 950-2150 MHz or 70/140 MHz) for processing by the indoor modem equipment. The receive converter (LNB, Low-Noise Block) design includes: a waveguide input (WR-42 for Ka-band receive, accepting circular or linear polarization through an orthomode transducer or polarizer), a low-noise amplifier (LNA, using GaAs or InP pHEMT MMIC, noise figure 1.0-2.0 dB, gain 25-35 dB), a frequency conversion stage (mixing the RF with a local oscillator to produce the IF; the LO frequency is chosen so that the desired RF band maps to the IF band: for 19.7-20.2 GHz to 950-1450 MHz IF: LO = 18.75 GHz), image rejection filtering (a waveguide bandpass filter before the mixer rejects the image frequency), IF amplification and gain control (20-40 dB of IF gain with automatic gain control to maintain a constant output power level), and a stable local oscillator (a PLLO, phase-locked dielectric resonator oscillator, with stability of +/- 1-5 ppm for consumer LNBs or +/- 100 ppb for professional-grade LNBs). The transmit converter (BUC, Block Upconverter) performs the reverse: taking the IF from the modem and upconverting to Ka-band for transmission, with a power amplifier stage (1-40 W output power using GaN or GaAs MMIC).