A low-cost wideband UHF downconverter with 5:1 tuning range

Future telescopes being considered for radioastronomy are likely to require large numbers of low-cost downconverters with wide bandwidth, wide tuning range, and the ability to operate close to strong sources of interference. This paper presents a simple UHF downconverter with 50-60 dB gain, 3 MHz instantaneous bandwidth and typical IIP₃ of about -26 dB over a tuning range of 400 to 2000 MHz. Image rejection is 30 to 40 dB from 400 to 1000 MHz, and increases to greater than 80 dB above 1000 MHz. Selectivity is greater than 60 dB for signals 15 MHz distant. This design can currently be built in small quantities for less than $500 (US) each.