U.S. Philips Corporation

Hubertus H Vereijken

Wolfdietrich G Kasperkovitz

Kaveh Kianush

Johannes C Meeuwis

Engelbertus C Egelmeers

Manually tunable analog receivers with AFC have the drawback that the AFC exhibits hysteresis and that in the event of fading pulling to an adjacent station may occur, whereas receivers with PLL electronic tuning have the drawbacks that tuning is comparatively slow and also inaccurate because of the tuning in discrete steps by a microprocessor. The present receiver combines the advantages of both analog manual tuning and electronic tuning. It includes two cooperating frequency loops, one loop (L1) being an AFC loop and the other loop (L2) having a frequency counter (13) for measuring the frequency (f.sub.0) of a tuning oscillator (6) which is controlled by both loops. Cooperation between the loops is provided by a control circuit (16) responsive to control signals supplied by both loops: an in-lock signal (in-1) and an in-window signal (in-w). Preferably, when the desired tuning is achieved, the power to a tuning section (12) of the receiver, forming part of the frequency loop (L2), is interrupted.

Radio receiver with digital control loop for coarse frequency

A receiver having an RF section, a mixer stage and a signal processing stage, the mixer stage receiving a mixing frequency from a frequency synthesis circuit which includes a phase-locked loop provided with a phase detection device having a current output, a loop filter including a .pi.-shaped RC network having an input shunt path and an output shunt path which are connected to respective ends of a series resistor incorporated in a series path, and to ground, and include first and second capacitances, respectively, and with a voltage-controlled oscillator, a reference frequency being applied to the phase detection device. In order to prevent the use of active filter circuits in the phase-locked loop of such a receiver, the second capacitance is chosen to be at least twice as large as the first capacitance, the series resistance is chosen to be smaller than the output impedance of the phase detection device and the output shunt path of the loop filter is provided with an RC phase shift member for reducing the phase shift of the second capacitance in the output shunt path.

Growing community of inventors

Eindhoven, Netherlands

Hubertus H Vereijken