GB433843A - Improvements in radio receiving systems - Google Patents

Abstract

433,843. Directive wireless signalling. STANDARD TELEPHONES & CABLES, Ltd., 63, Aldwych, London.-(Assignees of Soc. MatÚriel Telephonique, Soc. Anon. ; 46,Quai de Boulogne, Boulogne-sur-Seine, France) Jan. 4, 1935, No. 336. Convention date, May 5, 1934. [Class 40 (v)] The field characteristic of a fixed aerial system is automatically modified or conditioned so as to maintain the principal lobe always directed upon a given station in spite of permanent or periodic changes in the direction of the signal wave-front. The arrangement minimizes ordinary or selective fading, and also allows the use of an extended aerial-array without any loss of efficiency due to phasevariation along its front. Also the same aerial can be used to feed simultaneously several receivers operating on different wavelengths, and to possess a particular directivity on each wavelength. The desired result is secured by electrically or mechanically maintaining a predetermined relation between the phases of the aerial voltages before they are fed to the receiver. Frequency-changers are associated with each aerial element, together with electrical phasechanging devices for adjusting the phase of the locally-generated oscillations as the incoming wave-front alters. As shown in Fig. 1, signals say from the aerial A2 are combined in DE2 with local oscillations from B02 to produce an I.F. frequency in IFA2. Simultaneously say twelve harmonic frequencies are produced in HGA2 and are combined with similar harmonic frequencies from HGA1 in a common detector DEC, the output from which is fed to a direct-current amplifier AC1. The latter is coupled through a coil L to the local oscillator B02 in order to synchronize it with the similar oscillator BO1, in graduated steps corresponding to the harmonic frequencies produced by HGA1, HGA2. A part of the output from IFA2 is combined with part of the output from IFA1 (comprising a phase-changer PH) in a balanced detector BED. This is coupled to a direct - coupled amplifier AC2 which serves through a coil L1 to initiate the step-by-step changes effected in the oscillator B02 by the amplifier AC1. The oscillators BO1, B02 normally operate at the same frequency and phase until a change in the direction of the incoming wave calls for compensation. DEF is the receiver. Fig. 2 shows the invention applied to an extended array of aerials A1 ... A8 each coupled to frequency-changers DA1 ... DA8 linked to harmonic-generators HGA1 ... HGA8. The aerials are connected in two groups to intermediate - frequency amplifiers IFA1, IFA2, the frequencies of which are further changed by a local oscillator BO feeding out-of-phase components to the detectors DE1, DE2. The combined frequencies are fed to a balanced detector BDE, the output from which is applied to control the gain of one of two amplifiers A1, A2 and so produce a positive or negative phase difference between the voltages of an oscillator OSC applied to the points P1, P8 of an impedance chain Z1 ... Z7 simulating the spacing of the aerials A1 ... A8 and the phase-relation of the pick-up voltages. The balanced detector BDE is affected by any change in wave-front, and automatically readjusts the phase-relation between the harmonic-generators HGA1... HGA8, so that the receiver RR follows the new front. The Specification as open to inspection under Sect. 91 comprises an arrangement in which the pointer of a radiogomometer on a mobile craft automatically modifies the response of a receiving aerial so that it " follows" an incoming signal in spite of relative movement between the transmitter and receiver. This subject-matter does not appear in the Specification as accepted.