| 摘要 |
1,083,860. Phase detection circuits. HUGHES AIRCRAFT CO. Oct. 11, 1965 [Feb. 8, 1965], No. 42968/65. Heading H3A. In a system for receiving data signals having one of a plurality of distinct phases, the local oscillator is maintained phase locked despite the phase changes in the received signal. A system for receiving a signal having four possible equally spaced phases, Fig. 4, comprises phase detectors 50 . . . 55 fed from the local oscillator 58 with phase shifted reference signals. The two detectors 50, 51 produce four possible output combinations #A.#B, #A.#B, #A.#B, A.#B depending in which quadrant the data signal lies. For example with an input signal having a phase # 1 an output A.B is produced and is selected by the logic circuits 74 . . . 77 to produce an output at 78 which sets the switch 87 to connect detector 52 to the oscillator control circuit. The phasing of the reference signal to this detector is such that any deviation of the oscillator phase results in an appropriately phased oscillator control signal. Similarly with an input # 2 , the detector 53 produces the correct control and is accordingly selected by the switch 87. Arrangements for two phase and three phase signals are also described, Figs. 1, 6 (not shown). |
