GB1511363A - Ultrasonic transmitter with electrostatic ultrasonic transducer - Google Patents

Abstract

1511363 Remote control of radio and T.V. receivers; semiconductor pulse generators INTERNATIONAL STANDARD ELECTRIC CORP 9 July 1975 [16 July 1974] 28902/75 Addition to 1472451 Headings H3Q and H3T [Also in Division G4] In an ultrasonic transmitter having a source of DC voltage in series with an impedance to provide a polarizing DC voltage at the capacitance of an ultrasonic transducer W and a controlled electronic switch T1 connected in parallel with the transducer, a variable pulse repetition frequency square wave generator OSZ controls the electronic switch via a pulse modifying circuit IF so as to derive a short-circuiting control pulse of constant duration for the electronic switch at any of the selectable frequencies. As shown the transducer has a D.C. polarizing voltage supplied by L1 and D 1. The pulse modifying circuit can be a monostable circuit or in Fig. 2a a differentiating circuit producing a waveform (Fig. 2b, not shown) from the pulse output of the oscillator and a resistor R2 and a zener diode D3 which clamp the positive phase of the oscillator output pulse (A) to level (B, Fig. 2c, not shown) so as to supply a closing pulse (A') of constant duration to the electronic switch at all repetition frequencies of the oscillator. The oscillator can be switched to different frequencies as by a switchable divider. The unwanted negative components of the pulses from the oscillator are clamped to a level (C) by the zener diode D3 and a diode D2. The desired pulse shape can also be derived directly from a divider circuit and if required with additional AND or NOT AND circuits. The electronic switch T1 can be a transistor, thyristor or ovonic type. The transmitter arrangement is applicable to the arrangements described in Specification No. 1,472,451 in which an oscillator is switched to different frequencies by a touch responsive circuit and the arrangement described in Specification No. 1,485,839 in which there is provided an energy recuperation circuit.