| 摘要 |
<p>A surround-field ultrasonic parking assistance system comprises a transmitting amplifier (3, fig.1) a transducer (2, fig.1) and a receiving amplifier 100. The signal from the transmitting amplifier may saturate the receiving amplifier 100. In the receiving amplifier circuit 100 of the invention, the amplifier 1 receives a signal Ue from the ultrasonic transducer, and receives an additional signal for the purpose of reducing the output Ua of the amplifier due to an unsuitably large input Ue. The additional signal may be a voltage signal Ug or a current signal Ig. The additional signal may be arranged substantially to reduce the output Ua due to the input Ue at times of overdrive (fig.9), e.g. by control of its phase or amplitude to correspond with the input signal Ue. A signal that has been received and stored from a preceding transmitting cycle may be read from memory to generate the additional signal. The circuit thus needs no switch to disconnect the receiving amplifier during transmission, allowing more of the circuit, indicated by numeral 10, to placed on an IC. It also allows a more cost effective ADC to be used.</p> |
