TRANSMITTER CONTROL SYSTEM FOR LOW DATA RATE FSK MODULATION

摘要

Packets of data are transmitted by an FSK modulated transmitter including a controlled oscillator and a phase locked loop for carrier frequency control, in which the loop compares the transmitted frequency with a reference source. A transmission starts with a burst of carrier signal free from data. Just prior to, or approximately at the start of, modulation with a data sequence the phase locked loop is opened. The control signal for the controlled oscillator is maintained approximately constant for the duration of the data sequence transmission, and the loop is closed again after completion of data transmission.