GB1062943A - Interference suppression system - Google Patents

Abstract

1,062,943. Radio receiving systems. SENN CUSTOM Inc. Sept. 12, 1963, No. 35964/63. Heading H4L. An interference suppression system in a radio receiver comprises a pair of spaced aerials and means for varying the relative amplitude and phase of the signals from the respective aerials so that the wanted signals are combined additively and the interfering signals are balanced out. As shown in Fig. 2, the signals from the two aerials are supplied via resistors 14, 16, which are adjusted to equalize the amplitudes of the interfering signals, to the respective ends of a delay line 62 comprising a winding 54 on a conductive non-magnetic core 56 which is earthed at each end, and an adjustable coupling coil 60 for effecting the required phase balance. The output of the coil 60 is supplied via a cathode follower 48 to the radio receiver 50. In a modification, Fig. 1, not shown, the delay line is of linear form and the coupling coil is movable within the hollow core of the delay line. In a further arrangement, Fig. 3, the interfering signals from aerials 10, 12, are balanced as regards amplitude by a potentiometer 124. The resulting signals from potentiometer 68, 70 are supplied via a changeover switch 76 to a balun in the form of twisted conductors 78, 88 wound on a ferrite core, which converts the unbalanced input into a balanced output for application to an R.C. phase-shifting network 86,84,92,94. The output from the potentiometer 100, 102 is fed direct via a similar balun 106 to phase-shifting network 86, 116, 118, 120, the required phase balance being achieved by adjustment of potentiometer 86. The changeover switch 76 doubles the amount of phase shift available. A tuned circuit 126 combines the outputs of the two phase-shifters for amplification at 138. With balanced aerials the baluns are omitted and the output signals may be combined by application to the respective control grids of a pair of valves with a common cathode output impedance. In a further arrangement the two signals are combined by means of a pair of ferrite cores with separate input windings but linked by a common output winding. The amplitudes may be balanced by means of adjustable transformers in the respective aerial circuits. An arrangement using two pairs of aerials to eliminate two interference signals is described, Fig. 8 (not shown), the signals from each pair being first combined as previously described and the resulting pair of signals being combined in like manner.