| 摘要 |
PURPOSE:To increase the isolation between the input and output for 4-phase phase modulator, by giving a given bias current to each two phase modulators from a constant bias supply circuit, when an interruption signal of carrier is fed. CONSTITUTION:Between microwave hybrid circuits 18 and 20, a pair of two-phase PSK modulators 10, 12, interruption switches 22, 24, and drive circuits 14, 16 are provided to form 4-phase modulator. Between the drive circuits 14, 16 of this modulator and two phase PSK modulators 10, 12, switches 30, 32 are respectively provided, and constant voltage generating sources 26, 28 consisting of power supplies 26a, 28a and variable resistors 26b, 28b are respectively connected to the switches 30, 32. Further, in normal operation, the bias current corresponding to the input pulse signal is fed to two-phase PSK modulators 10, 12 from the drive circuits 14, 16, and when the carrier interruption signal is fed, a given bias current is fed from the sources 26, 28 by switching the switches 30, 32 at the same time when the circuits 22, 24 are OFF to increase the isolation between the input and output. |
