Patent GB-901428-A (GB)
Title: Improvements relating to pulse analysis circuits
Inventor: WHITE ERIC LAWRENCE CASLING
IPC: G01S3/50
Filed: 1957-08-10
Abstract: 901,428. Classifying pulses. ELECTRIC & MUSICAL INDUSTRIES Ltd. Aug. 7, 1958 [Aug. 10, 1957], No. 25294/57. Class 37. [Also in Group XL (c)] A pulse analysing system, particularly for classifying pulses received from a number of radar transmitters, derives signals representing certain characteristics of each pulse received. Characteristics specified are amplitude, duration, radio frequency and extrinsic characteristics such as bearing and time of arrival. The characteristics of each pulse are stored for comparison with those of the next pulse and an output signal produced if the characteristics of the subsequent pulses have a predetermined relationship. Registering first pulse.-As shown, a number of registers such as that shown in Fig. 3, have their inputs connected to bus-bars 1, 2, 3, the voltages of which represent the derived values of the selected characteristics of the received pulses. The registers are such that they cannot respond until at least one pulse is already registered in them unless they have been allotted manually or by an allotting circuit, Fig. 4. Assuming that the apparatus has just been switched on and that a pulse is received by the radio receiver (not shown), voltages representing pulse width and sine and cosine of bearing appear on the bus-bars 1, 2, 3 and a seizing pulse passes through an open inhibiting gate 14, Fig. 3, to the allotting circuit, Fig. 4. Since the first register is idle and not busy as shown, the pulse is passed by the upper AND gate 17 to a pulse generator 10 of the first register and changes over the upper bi-stable circuit 18 to indicate that the register is busy and enable the next pulse to open gate 16. On receiving the pulse, generator 10 opens gates 6a to 6c in the selected register and as a result the voltages on the bus-bars, after amplification, are transferred to capacitors 8a to 8c. A pulse is also fed to the counter 11. Registration of subsequent pulses.-Amplifiers 4a to 4c have differential inputs, the bush-bar signal being opposed by the voltage registered for the previous pulse. Discriminators 5a to 5c respond only to amplitudes of the output signals from 4a to 4c corresponding to permissible variations between pulses. Assuming this condition is complied with in respect of all the relevant characteristics, 3-gate 9 is opened and generator 10 opens gates 6a to 6c to allow the registered voltages to be adjusted if necessary in accordance with the new pulse values and to step on the pulse counter 11. At the same time a pulse is fed to gate 13 to close the inhibiting gate 14 and ensure that the pulse does not seize a further register. If the new pulse is not sufficiently similar to any pulse registered, gate 14 remains open and a new register is allotted as in the case of the first pulse after switching on. The cathode-ray tube displays.-The bearing data may be displayed as a radial line on a cathode-ray tube. The values of pulse width, amplitude or radio frequency may be indicated by causing the cathode-ray to describe numerals. Alternatively, one parameter may be represented by the length of the radial line. Pulse duration determination.-As shown in Fig. 5, distorted pulses are applied to a pulselengthening circuit 19 and to a circuit 20 giving a delay greater than that of the lengthened pulse. The two pulses modulate a radio frequency carrier 23 which is amplified, rectified and, with the aid of a delayed A.G.C. arrangement, converted to the form shown at 25a. The delayed pulse has its original duration but is of amplitude independent of the original amplitude. The latter pulse is extracted and opens a gate G (Fig. 1) to allow charging of capacitor C. The amplitude of the pulse from C is thus dependent on the duration of the incoming pulse. Radio frequency determination.-The received pulses are divided between channels provided with filters having inverse amplitude/frequency characteristics (Fig. 2, not shown). Rectified outputs from these channels are then combined to give a voltage which represents the frequency of the incoming pulses.