| 摘要 |
The system (50) includes an FAM modulator (58) that performs frequency modulation of a video data to produce a frequency modulated carrier signal having preselected frequency. The FM video signal includes audio and video data. A transmitter (54) with predetermined output impedance, is connected to the FM modulator for transmitting the modulated carrier signal. A coupler (52) is connected between an electrical line (12) and the transmitter for matching the predetermined output impedance of the transmitter to the characteristic impedance of the electrical line. The coupler includes a linear phase unit for communicating the modulated carrier signal to the electrical line without significant phase distortion. The linear phase unit has an air- core transformer. The diameter of the secondary coil of the air- core transformer is smaller than that of the primary coil. In the air-core transformer, the secondary coil extends coaxially within the primary coil such that an air-gap is created between the primary and the secondary coils. The modulator includes a frequency converter that converts the modulated carrier frequency from the preselected frequency to another frequency. A receiver receives the modulated carrier signal. An FM demodulator (66) is electrically connected to the receiver for demodulating the received modulated carrier signal and for producing demodulated carrier signal having preselected frequency. Another coupler (68) is connected between the electrical line and the receiver for matching the input impedance of the receiver to the characteristic impedance of the electrical line. |
