GB225970A - Improvements in repeating circuits for radio transmission systems - Google Patents

Abstract

225,970. Western Electric Co., Ltd., (Western Electric Co., Inc.). Oct. 2, 1923. Relaying or repeating systems; diplec and duplex systems; directive signalling; thermionic modulation systems. - A directive antenna array comprising a plurality of antennae is used in a radio repeating system. The antenna array mav have either a unilateral or a symmetrical or non- symmetrical bilateral characteristic. Fig. 1 shows three vertical antennae X<1> - - X<3> of an array which are spaced apart by a definite fraction ## of a wavelength and to which are connected phase shifting devices PS1, PS2, band filters F1, F2 and amplifiers A1, A2, through triple winding transformers T1, N1 being balancing networks. In a modification, the vertical antennae are replaced by loop antennae. Fig. 4 shows one unit of an array in which ground antennae X<1>1 are used for receiving and vertical antennae X1 for transmitting, each having two degrees of freedom for the simultaneous transmission of two channels using frequencies f1, f2. Phase-shifting devices PS - - PS4 and band filters Fl - - F4 control the operation while amplification may be by common amplifiers A1, A2 or by separate amplifiers for each channel. The ground antennae in a modification are replaced by loop antennae. In a two-way system using only one frequency interference is eliminated by coupling the transmitting antennae to the receiving antennae by means of local circuits each of which is provided with a phase-shifting device PS1 and is individual to a pair of receiving and transmitting antennae as shown in Fig. 7. Fig. 9 shows a two-way system in which terminal stations A, B are connected to lines L1, L2, signals from L1 serving to modulate oscillations from the oscillator O1 by means of the modulator M1. The signals are relayed at C, being received by a loop array of which X<1> is a unit, amplified and transmitted by a vertical array of which X<1> is a unit to a loop antenna X<5>, at B. After amplification at A4 the carrier wave is demodulated at D2 and the signals impressed on line L2. Part of the .received carrier wave is diverted by transformer T3 and is modulated by signals from L2 and is, after amplification, transmitted over the return channel. To avoid singing, the repeater or repeaters RR may be geographically distributed with reference to the terminal stations T as indicated in Fig. 10. Fig. 13 shows a system in which the carrier frequency is varied at the relay station to give the distribution shown in Fig. 13<c> between termlnals A, B and repeaters 1 - - 4. Each antenna has two degrees of freedom f1, f2 and the received oscillations f1 are amplified and impressed on a modulator M1 together with local oscillations of a frequency f3 from the oscillator 01, one of the resultants f2 being selected and after amplification transmitted. Fig. 14 shows a repeating station in which the translating acts are performed in a circuit common to all the antennae of the array. PS1 - - PS6 are phase-shifting devices and L1 the common input having filters F1, F2 and power amplifier A1, the output L2 being common to all the antennae. Statics may be minimized by employing short waves and by spacing the repeaters at points depending on the energy drop between them. Specification 217,238 is referred to.