Radio receiver having phase locked loop and automatic frequency control loop for stably maintaining local oscillator frequency of voltage-controlled local oscillator
US4365349A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 22, 1981 |
| Grant date | Dec 21, 1982 |
| Priority date | — |
| Expiry date | Jan 22, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03J5/0281
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A radio receiver comprises a phase locked loop and an automatic frequency control loop which are selectively coupled with a voltage-controlled local oscillator to control a local oscillator frequency. The phase locked loop and the automatic frequency control loop have a common loop filter which supplies the voltage-controlled oscillator with a control voltage. The loop filter is arranged so that its time constant may be switched from a small value to a great value in response to switching of the operation mode of the voltage-controlled oscillator from a phase locked loop control mode for the selection of broadcasting station to an automatic frequency control loop control mode for the maintenance of the local oscillator frequency after tuning of the radio receiver. The radio receiver can be arranged so that the local oscillator frequency may be maintained by the phase locked loop after the tuning of the receiver to a weak broadcast signal when muting control is rendered ineffective by a muting switch.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.