| 摘要 |
<p>A self-oscillating burst mode transmitter transmits an integral number of cycles of a carrier signal in each transmission burst. Each burst commences at a peak value of the carrier signal and terminates at a peak value. The transmitter includes an L-C tank circuit comprising a transmitting coil (L1) connected to a capacitor (C4). The L-C tank circuit is selectively energized through a switching network (Q1, Q2, U1, U2) connected to a power source, causing the tank circuit to resonate at a prescribed frequency (f0). Selective energization of the tank circuit is achieved by the switching network as controlled by a peak voltage detection circuit (32, 34). The peak detection circuit senses when a peak voltage is present in the oscillatory waveform appearing across the coil of the resonating tank circuit. Power is switched off to the tank circuit at the conclusion of each transmission burst only when the oscillatory voltage waveform, as sensed by the peak detection circuit, is at a peak. This peak voltage is stored by the capacitor of the tank circuit during the time the power source is not connected to the tank circuit. At the beginning of the next transmission burst, when power is again coupled to the tank circuit through the switching network, the voltage initially appearing across the coil, and hence the voltage at the commencement of the next oscillatory waveform of the transmission burst, begins at the peak voltage value stored on the capacitor.</p> |
