GB1433590A - Arrangement for the signal-to-noise ratio of the signals picked up by aerials comprising a plurality of elements - Google Patents

Abstract

1433590 Diversity reception COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS CIT-ALCATEL 30 July 1967 [23 Feb 1967] 50439/69 Divided out of 1433588 Heading H4L In an arrangement for improving the signalto-noise ratio of signals picked up by an aerial comprising a number of elements 1 1 , 1 2 ... 1 N , the signal picked up by each element passes to a compensation member such as 3 1 , a band-pass filter such as 5 1 and a controlled gain amplifier such as 6 1 , and the outputs of all the amplifiers 6 1 , 6 2 ... 6 N are connected to an adding member 10. The useful signals received by the aerial occupy a narrow band width and the members 3 1 , 3 2 ... 3 N , which comprise delay networks or phase-shifters, ensure that the useful signals presented to the filters 5 1 , 5 2 ... 5 N are all equal to one another. The pass-bands of the filters are centred on the frequency of the useful signals and have corresponding narrow band widths. The gain of each amplifier such as 6 1 varies inversely with the control voltage such as U 1 . The control voltage circuit comprises a multiplying member 71 connected to opposite ends of the amplifier 6 1 an integrator-detector 8 1 and a comparator member 9 1 . The other input of the member 9, is supplied with a reference voltage K identical for all the members 9 1 , 9 2 , 9 N . The voltage U 1 represents exactly the average power of the noise received at the aerial element 1 1 . The output of adding member 10 is a signal having the same amplitude as the input signal to the aerial but accompanied by a noise of lower strength.