Patent GB-1068381-A (GB)
Title: Device for determining the directivity factors of acoustic and electro-magnetic receivers and radiators
Inventor: VLASOV VLADISLAV LEONIDOVICH
IPC: G01R29/10
Filed: 1964-04-11
Abstract: 1,068,381. Electric analogue calculating. VSESOUZNY NAUCHNO - ISSLEDOVATELSKY INSTITUTE FIZIKO - TEKHNICHESKIKH I RADIO - TEKHNICHESKIKH IZMERENY. April 11, 1964, No. 4140/64. Heading G4G. [Also in Division H4] The invention relates to means for computing the value of for an electromagnetic or acoustic radiator or receptor in order that the directivity characteristics may be determined, where D(0, #) is the field strength at a point on a reference sphere centred on the radiator or receptor whose angular distance from the vertical axis is # and whose azimuthal angle is #. The value of the said double integral is approximated by computing in each of a discrete number N of planes containing the vertical axis and spaced apart by an azimuthal angle and then computing As described, a generator 3, Fig. 1, supplies a radiator 2, being tested, the field from which is received by a receiver 1, whose output is applied to a detector 4. D.C. output voltage from the detector 4 is applied to one input of a converter unit 5, and an A.C. output, of fixed amplitude and frequency, from a local oscillator 6, is applied to a second input of the said converter, whose output is a proportional A.C. voltage having the frequency # 0 /2# of the local oscillator 6. A dual fixed frequency conversion unit comprises two mixers 7, 8, and a local oscillator 9, of frequency #1/2# where # 1 << # 0 . The outputs of the converter unit 5 and of the oscillator 9 are each taken to one of the two inputs of the mixer 7, whose output is taken to one of the two inputs of the mixer 8. The other input of the mixer 8 is supplied from the output of the converter unit 5, but with a phase-shifter, such as a selsyn-transmitter, 10 interposed. The radiator 2 is turned as indicated by the dotted lines 18 in a plane containing the vertical axis from #=0 to # = # by a rotation means 11, to which the phase-shifter 10 is mechanically coupled. In consequence, an angular phaseshift equivalent to (# - #/2) is introduced into the output of the converter unit 5 fed to the mixer 8, as compared with the output of the converter 5 fed directly to the mixer 7. The voltage at the output of the mixer 8 is then proportional to the square of the signal amplitude being measured, multiplied by sin #. This output is taken through relay systems 13, 16 to an integrator 12 and an indicating instrument or digital recorder 15. In use, a motor 14 provides for rotation in a vertical plane of the radiator 2 and the relay system 13 switches the integrator 12 on when # = 0 and off when # = #. A motor 17 under the control of a relay system 16 provides for stepping, for rotation in a horizontal plane, in increments of ##=2#/N   after the completion of each integration from # = 0 to # = #, the integrator being arranged for accumulation. The relay systems also provide for switching off after the radiator has completed a rotation of 2# in the horizontal plane, the whole sequence thus being made automatic. When a receptor is to be tested it is connected to the detector 4 in replacement of the receiver 1, and is mechanically coupled to the rotation means 11 as indicated by the dotted lines 19, the radiator 2 being maintained stationary.