GB735901A - Improvements in or relating to hybrid junction arrangements for use on micro radio waves - Google Patents

Abstract

735,901. Directive radio systems; frequency changers. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Jan. 22, 1954 [Feb. 6, 1953], No. 3477/53. Classes 40 (6) and 40 (7). A free space hybrid junction arrangement comprises two linearly polarized plane radio mirrors arranged in succession between the input and output ends of the hybrid junction with their directions of polarization and their planes inclined at predetermined angles to each other. Fig. 2 shows an arrangement wherein the planes of the mirrors M1 and M2 are parallel and their directions of polarization differ by 45 degrees. Incoming waves A and B travelling in directions making an angle of 90 degrees with each other and being linearly polarized at right angles in the directions shown respectively pass through and are reflected by M2 to reach M1. At M1 the horizontal components of the two waves are passed to give a difference signal at C and the vertical components reflected to give a sum signal at D. Such a system as that of Fig. 2 requires beams not too widely divergent or convergent and it may be convenient in some cases to introduce a lens (CL) between the mirrors as described with reference to Fig. 3 (not shown). This may be combined with the use of further lenses at the input and output ends of the junction, when beams are used having plane wave fronts. Such an arrangement (Fig. 4, not shown) functions in free space and accepts unguided waves. When the invention is used in the form of a radar transmitreceive arrangement (Fig. 5) waves from the transmitter primary element TM are polarized so as to be reflected completely by M1 and one component of the reflected wave is also reflected by M2. The component transmitted by M2 is reflected by a plane mirror M3 about #2#/<SP>3</SP> behind M2 and repasses through M2 to form a circularly polarized wave when combined with the other component. This circularly polarized wave is directively transmitted through metal lenses FL and WA. Returned echo signals, which will also be circularly polarized, passing through lenses WA and FL are -de-circularized by the M2, M3 combination and the linearly polarized wave so formed passes through M1 to receiving element RM. In a further embodiment of the invention (Figs. 6a and 6b, not shown) the inputs at one end of the junction are respectively the directionally received signal and the local oscillator signal and the outputs are sum and difference frequencies derived from the various elements of two two-dimensional matrices of primary elements. It is arranged that the signal from the local oscillator is received by all the elements of the matrices but that the directionally received signal is focused on only one element in each matrix; the particular element used being determined by the direction of the incoming signal. A similar embodiment with unidirectional (i.e. linear) matrices is described with reference to Fig. 7 (not shown).