GB1327121A - Electronic technique for an all-electronic cylindrical array beacon antenna - Google Patents

Abstract

1327121 Aerials; amplitude modulators INTERNATIONAL STANDARD ELECTRIC CORP 6 May 1971 [11 May 1970] 13468/71 Headings H3R and H4A In an electronically scanned cylindrical aerial array with radiating elements arranged in juxtaposed columns, each column is individually excited with R.F. energy which is modulated by a plurality of modulation signals and which is suitably phased so that a rotating field effect is obtained. Column excitation apparatus comprises first and second modulators which are fed with radio-frequency carrier signals and with respective first and second modulation frequency signals. The modulating signals synchronously generated, and the frequency of the second signal is greater than that of the first signal. Phase shift means are included in the path of the R.F. input to, or in the path of the output from, the second modulator. A composite column excitation signal is obtained by combining the output from the first modulator with the phase shifted output from the second modulator. An embodiment having a particular relationship to a TACAN aerial system such as that which is described in Specification 1,247,242, comprises a 6dB directional coupler 2, Fig. 10, which receives R.F. input power at a terminal 1, and which divides said power between lines 3 and 28. In the line 3 is a balanced modulator which includes two PIN diodes 10, 14, a 3dB directional coupler 7, inductors 6, 12, 13, 16, resistors 11, 15 and coupling capacitors 4, 18. 15 Hz modulation signals which are applied at terminals 9, 9a are conveniently of squarewave form. The output from the balanced modulator is further modulated at 45 Hz in a sine wave approximation by means of a single-ended modulator which includes a PIN diode 20, inductors 22, 46, a resistor 21, and a coupling capacitor 25. 45 Hz modulation signals (third harmonic of 15 Hz) are applied at a terminal 23. The output signals have a modulation envelope as shown at inset "B", and they are applied to one input of a 6dB directional coupler 26. In the line 28 is a balanced modulator which includes two PIN diodes 33, 34, a 3dB directional coupler 32, inductors 31, 36 and coupling capacitors 29, 37. 135 Hz squarewave modulation signals are applied at terminals 45, 45a. The output signals have a modulation envelope as shown at inset "C" and are applied through a phase-shift element 38, such as a length of transmission line, to the other input terminal of the directional coupler 26, the output of which, at a terminal 27, is a composite excitation signal for a column of radiators of the cylindrical aerial array. The arrangement is stated to improve the operating bandwidth and the coverage in elevation of the aerial array.