Patent GB-945008-A (GB)
Title: Transmitting and receiving circuits for wave transmission systems
Inventor: PRITCHARD WILBUR L
IPC: G01S1/02
Filed: 1960-07-05
Abstract: 945,008. Combined radio receiving and transmitting systems; aerial couplings; radar. RAYTHEON CO. July 5, 1960, No. 23513/60. Headings H4A, H4D and H4L. Relates to a transmitting and receiving circuit e.g. in a radar system, utilizing a common aerial arranged so that the receiving portion receives waves polarized in a plane at right angles to that of the tranemitted waves. As shown in Fig. 1, the transmitted power from a radar system 10 is fed via a common transmission line 9 to a hybrid junction 11, e.g. a magic- T, where it is divided into two equal parts in the arms C1, C2. The arm C1 is connected via a line 12 and gyrator 13, which produces no phase shift in this direction, to the arm C3 of hybrid junction 27, and the arm C2 is connected to the arm C4, the signal being re-combined in the arm H2 and supplied to the horizontal transmitting aerial 24, no power being supplied to the vertical receiving aerial 25. The aerial system comprises a horn 21, e.g. of square cross-section, having a section of waveguide 23 attached to its end 22, the far end of the waveguide being closed by a conducting plate 28 spaced from the members 24, 25 by a distance of the order of a quarter of a wavelength to prevent reflections of energy along each transmission line. The gyrator 13 may be of the type in which a small core of ferrite material is carried in a circular waveguide and a magnetic field is provided as by a coil 29. During reception both aerials receive signals but a horizontally polarized wave supplied to the arm H2 will appear at arms C1, C2 as equal but oppositely phased waves, due to the phase shift at 13, and will be absorbed by the load 20 in the arm E1. A vertically polarized wave supplied to the E plane arm E2 will produce at arms C3, C4 two equal but oppositely phased waves which will appear at arms C1, C2 with the same phase and will be supplied via the arm H1 to the common transmission line 9. In a modification, Fig. 2, a signal from the radar system 10 is supplied via a common transmission line 9 to the arm H3 of a hybrid junction and divided by arms C5, C6. The TR switch 45 is located a quarter-wave further from the hybrid junction 41 than is the TR switch 44 so that when the TR switches fire the reflected waves are in antiphase and are combined in the arm E3 and transmitted from the aerial 15 as a horizontally polarized wave. The operation of the TR switches will prevent a signal from appearing at the hybrid junction 42. Horizontally polarized waves received by the aerial 15 and supplied to the arm E3 appear in the arms C5, C6 as antiphase signals. Their amplitudes are insufficient to fire the TR switches and they are not accepted by the arm H3 but are absorbed in the load 43 of arm E4 of the hybrid junction 42. Vertically polarized waves are supplied to the arm H4 and appear as inphase signals in the arms C7, C8. Since the TR switches do not fire the signals are accepted by the arm H3 of the hybrid junction 41 and supplied to the common transmission line 9. Solenoid operated shorting pins may be provided to selectively short circuit the transmission lines at each TR switch so that signals may be transmitted and received through the horizontal polarization feed 14 only, vertically polarized received signals being absorbed in the arm E4.