One of the most important parts of the RF (radio frequency) transmitter is the upconverter section, that converts the baseband or immediate frequency (IF) signals to microwave. These circuits could be hard to design according to the frequency range, bandwidth and step size, spurious rejection, phase noise, physical size, output power, etc.
The upconversion can be realized several ways, my choice was the two step superheterodyne conversion to achieve the difficult specification I defined. The circuit contains two programmable frequency synthesizers as local oscillators. The first stage converts the 100MHz modulated IF signal to1500MHz, then the second stage converts it to 3700…4000MHz with 500kHz carrier step.
My thesis is a part of a C-band transmitter that contains the SDR (software defined radio), the upconverter, the power amplifier and the DC power supply. I present the upconverter from design, to realization and measurement.