RADIO TRANSMITTERS

摘要

A signal synthesiser arrangement includes a signal generator in the form of a voltage controlled oscillator (VCO) (10) which generates a high frequency source signal under the control of a control unit (16). The synthesiser control unit (16) controls the oscillator (10) to produce an output signal of a given frequency. The output signal of frequency F1 from the oscillator (10) is provided to a signal mixer (12). It is also input to a frequency divider (15), which divides it by a value N1 to produce an "offset frequency" signal F2 which is also provided to the mixer (12). The mixer (12) combines these signals and provides the combined signal to a bandpass filter (11) which filters the combined signal to select and provide one of the "sideband" signals produced by the mixer, i.e. F1 + F2, or F1 - F2, as its output signal F3, while suppressing the unwanted, other sideband signal. The output signal F3 from the filter (11) is further frequency divided by a second value N2 in a further frequency divider (17) to produce a signal of frequency Fout that can be used as a carrier frequency signal for a radio transmitter.