Super Wide Deviation Phase Modulator

A phase modulator is described which can directly deviate a crystal-controlled carrier by 1000 rad or more. Frequency multiplication or auxiliwry automatic frequency control (AFC) circuits are therefore not required. The modulator uses an accurate frequency source, a wide-band voltage controlled oscillator, a delay line, and two mixers The achievable phase deviation is proportional to the time-bandwidth (TB) product of the delay line, while the modulation bandwidth is inversely proportional to the time delay. Suitable delay lines are available using either bulk wave or surface acoustic wave transnission. Signal-to-noise ratio (SNR) and distortion are compatible with requirements for broadcast service. Design examples are given for monophonic and stereophonic FM broadcast modulators.