| 摘要 |
928,331. Diversity systems. NIPPON ELECTRIC CO. Ltd. May 12, 1961 [May 16, 1960], No. 17486/61. Class 40 (5). Relates to a frequency or phase modulation diversity reception system of the type in which automatic phase control circuits enable the respective intermediate frequency channels to be combined before detection. As shown, the incoming signals after frequency-changing at 8 to 11, respectively, are supplied via respective I.F. amplifiers 16 to 19 and buffer amplifiers 29 to 32 to a common output circuit and demodulator 28. Each channel is provided with a phase detector 33 to 36 which receives as one input the common output signal and as the other input the output of its corresponding I.F. amplifier, the resulting control signal being utilized to control the phase of the local oscillator 12 to 15 appropriate to that channel. The common output signal is amplified at 41 to provide common A.G.C. for the I.F. amplifiers. Monitor units 37 to 40 connected to the respective phase detectors operate a relay when a strong beat frequency is produced indicating a faulty receiving unit and block the corresponding buffer amplifier. The system is compared with a known system in which the phase relation of pairs of diversity channels is corrected and after combination a further phase correction and combination is made of pairs of the combined channels and so on. |
