Tuning device for digital transmitter selection in broadcast receivers, in particular in VHF receivers

摘要

A tuning device is indicated for digital transmitter selection in broadcast receivers, in particular in VHF receivers which enables a very fast and therefore inaudible changeover between two transmitters. The tuning device has a digital counter which measures the oscillator frequency (actual frequency), an ideal value generator for digital input of the receive frequency (ideal frequency) of a required transmitter, a comparator for the actual-ideal comparison and a device for generating an oscillator tuning voltage depending on the output signal of the comparator. According to the invention, the latter has a successive approximation register whose data input is connected to the output of the comparator and whose parallel outputs are connected to a digital-analog converter. Successive outputs of the register are seized in succession with an output signal, the output signal of the previous output being retained or cancelled before the respective next output is seized depending on the output signal of the comparator. The output signal of the comparator represents sign information for the existing frequency deviation. The analog output voltage of the digital-analog converter forms the control voltage for the oscillator of the broadcast receiver.