Patent GB-1325955-A (GB)
Title: High frequency directional apparatus
IPC: G01S3/42
Filed: 1972-04-22
Abstract: 1325955 Aerials; semi-conductor oscillation circuits WESTERN ELECTRIC CO Inc 3 June 1971 [9 June 1970] 18781/71 Headings H3T and H4A In an aerial array of the self-steering type a position of a signal obtained by reception on a reference aerial element A 0 , Fig. 1, is shifted in phase by 90 degrees by a means 25, and is applied to one input of a mixer 24 which is associated with the next element A 1  of the array. A portion of the signal obtained by reception on the element At is also applied to the mixer 24, which provides an output signal representative of the phase difference between its inputs. In transmission, a source 23 feeds the aerial element A 0  directly, and provides a frequency locking signal for an oscillator 21, which feeds the element A 1 . The phase of the output from the oscillator 21 is controlled by the representative signal from the mixer 24, so that it is conjugate with the phase of the signal received by the element A 1 . Thus, the wavefront transmitted by the elements A 0 , A 1  is parallel to the received wavefront. A similar arrangement is provided for each other aerial element A 2  to A N . The representative signal from the mixer 24 is also utilized to control the phase of the output from an oscillator 20, which is frequency locked by another portion of the signal obtained by reception on the aerial element A 1 . In this case, the output of the oscillator 20 is brought into phase with the signal from the element A 0 , and is combined therewith for feeding to a utilization means 22. A circulator is associated with each aerial element for separating received and transmitted signals, and a limiter-amplifier is provided on the receive side. The mixers 24 each comprise two square law diodes d 1 , d 2 , Fig. 2, arranged in a balanced circuit. The diodes are fed in parallel by a transformer 42 to which is applied the signal from the phase-shifting means 25, which may be represented as Ecos #t. The diodes are also fed in push-pull by a transformer 41 to which is applied the signal from the respective one of the aerial elements A 1  to A N . This may be represented as Esin(#t + #) for the element A 1 . Load resistors 43, 44 and by-pass capacitors 45, 46 are provided, and an output voltage e, which is proportional to sin #, is developed and is applied to two operational amplifiers 47, 48. Two voltages e 0 , which are also proportional to sin #, are developed on leads 26, 26a. The oscillator 21 comprises an IMPATT diode 51, with which is associated an inductor 52 in a resonant circuit. The locking signal Esin #t is applied by means of a circulator 55. Biasing to obtain correct phasing of the oscillator output is provided by the voltage on the lead 26 and by a series source 50, the latter being adjustable so that the correct working point of the diode 51 may be selected. A choke 54 and a capacitor 53 ensure R.F. decoupling between the oscillator and the mixer. The oscillator 20 is similar in construction to the oscillator 21, the voltage on the lead 26a being used for biasing. In another embodiment (Fig. 3, not shown) a modulator is interposed in each transmit path to an aerial element, and a demodulator in each corresponding receive path. Each modulator has one input at an intermediate frequency # IF , from a common source, and another input at a frequency (# T  - # IF ), where # T  is the desired transmitting frequency. An oscillator operating at the frequency (# T  - # IF ) feeds the modulator associated with the reference aerial element directly, and locks in frequency individual oscillators feeding the other modulators. The phase relationships between the oscillators are determined from the received signals as described for the first embodiment. In the case of the demodulators, one input for each at a frequency # is from the associated aerial element. The other input is at a frequency (#- # IF ), directly from an oscillator of that frequency in the case of the demodulator associated with the reference aerial element, or from an individual injection-locked oscillator for each other demodulator. The outputs at the intermediate frequency # IF  from all demodulators are paralleled for utilization. Specifications 1,291,046 and 1,312,837 are mentioned.