A surveillance receiver with a first stage of fixed frequency harmonic mixing and a second stage of swept frequency mixing

摘要

A receiver for analysing input RF signals comprises a first stage which includes an input for receiving one or more RF signals for analysis and a first local oscillator 51 having an output comprising a first plurality of frequencies. The input is mixed with the local oscillator output in a first mixer 55a to generate a first intermediate frequency spectrum output. A second stage includes a second local oscillator 58 adapted to produce as output a sweep signal traversing a second plurality of frequencies and a second mixer 55b for combining said second local oscillator output with said first intermediate frequency output to generate a second intermediate frequency output.