GB978221A - Improvements in or relating to radio communication systems - Google Patents

Abstract

978,221. Radio signalling. MARCONI CO. Ltd. May 8, 1961 [Aug. 8, 1960], No. 27388/60. Heading H4L. In a diversity radio communication system comprising at least two separable signal channels feeding the transmitter, intelligence signals are supplied to one of the channels and the same intelligence signals are supplied to one of the channels and the same intelligence signals are supplied to another channel after a predetermined time delay. At the receiver a similar delay is introduced in the previously undelayed channel whereby the signals on the two channels are brought into coincidence and means are provided for selecting the better signal or for combining both signals. With the switches SA, SB, SC and 11A, 11B in the position shown the signals from channel A, e.g. telephone signals, are fed via a filter 8 removing a narrow frequency band, e.g. 0-40 c/s., to a time delay device 7, e.g. a magnetic recording drum with spaced recording and pick-up heads, and the delayed signals modulate a sub-carrier at 5A and are then fed to the transmitter 1. The undelayed signals from A are also fed via switch SC to modulate a further sub-carrier at 5B, the signals from modulator 5B being fed to the transmitter 1. The output from the receiver 2 is fed to channel separators 9A, 9B, and detectors 10A, 10B, whose outputs are fed to respective contacts 12A, 12B of a selector device shown as a relay 12. The circuit to the contact 12B includes a delay device 13 providing the same delay as the device 7. The outputs of the detectors 10A, 10B are also supplied to respective 0-40 c/s. filters 14A, 14B, whose outputs are fed to a known comparator to switch the relay contacts to the channel providing the better signal at that time. With the switches SA, SB, SC and 11A, 11B in the alternative position the time delay devices are disconnected and the system provides two separate signalling channels A and B in conventional manner.