| 摘要 |
PURPOSE:To make phase of a sum signal and a difference signal coincide automatically, by detecting a phase difference of the sum signal and the difference signal by an error signal detecting loop consisting of a phase shifter, a 90 deg. phase shifter, a phase detecting circuit and an erro signal amplifier. CONSTITUTION:A phase shifter 9 has a function which is capable of varying the phase of an output of an IF amplifier 6b by external control voltage. Also, a 90 deg. phase shifter 10 has a function which is capable of changing the phase of an output of the phase shifter 9 by 90 deg.. An error signal amplifier 11 generates control voltage which is capable of varying the phase of the phase shifter 9 by amplifying an output of a phase detecting circuit 7b. Also, a terminal TP5 is an output terminal of the phase detecting circuit 7b. Accordingly, when an output phase difference of IF amplifiers 6a, 6b is denoted as DELTAtheta, the phase difference DELTAtheta is corrected automatically to ''0'' even if frequency of a carrier wave is varied, therefore, no influence is exerted even in case of a variation of frequency of the carrier wave. |
