Converting RF Signals for Satellite Communication

Building, Testing, and Tuning a High-Gain Down Converter

Second Order Effects designed, simulated, prototyped, and completed a production run of 24 microwave downconverter modules. Following a quick-turnaround prototype, the modules were deployed to multiple ground stations for a successful 5 year mission to gather scientific data.

This downconverter module was designed to process signals used to study atmospheric propagation in W-Band. W-Band mm-wave signals are transmitted from GEO satellites to ground station receivers in multiple geographic locations where SOE’s downconverter is installed. It serves as the 2nd stage of downconversion in the system. Its input frequency is 3.6 GHz and outputs an IF of 25 MHz. The downconverter includes a high rejection drop in cavity BPF to reduce spurs. The BPF roll off is especially important to reducing the noise floor in the IF band when downconverting so close to DC. Extra care was taken to reduce image noise in this case. The downconverter also features 75 dB of adjustable gain. Given the high gain of the signal path, attention is paid to separating filtering and gain stages physically by using a multiple cavity enclosure design. This allows reduction of spurious levels at the IF output to less than -60dBc.