Local oscillator circuit

摘要

An improved secondary local oscillator circuit is described, including a secondary oscillator 12 for generating a secondary oscillation frequency and a mixer for mixing the secondary oscillation signal with a radio frequency RF to generate an intermediate frequency signal IF. A reference frequency generator 40 generates a reference frequency and a phase locked loop circuit 50 compares the phase of the reference frequency with the phase of the secondary oscillation frequency. A low pass filter 60 receives the output of the phase locked loop circuit 50 and generates an error voltage representative of the phase difference detected by the phase locked loop circuit 50. A resonator CA-CV is coupled to colpitts oscillator transistor TR to produce an oscillator frequency dependent upon the said error voltage.