| 摘要 |
PURPOSE:To simplify the circuit of an antenna input part by extending and contracting antenna elements automatically according to the level of an electric field being received. CONSTITUTION:When a broadcasting wave is received by an antenna 11, the output of a high frequency amplifier 2 varies with the received level. This signal is converted 5 into a binary code, which is applied to a microcomputer 7 and decoded by a program memory. Then, the microcomputer 7 applies an antenna control circuit 9 with a signal for converting the polarity of a control signal with constant time width according to the decoded contents of the binary code. Then, a voltage and a current with the constant time width are switched between the positive and negative polarities to drive a motor 1, controlling the length of antenna elements of the antenna 11. |
