U.S. Philips Corporation

Harry B Schoonheijm

Wolfdietrich G Kasperkovitz

Theodoor A Claasen

Johan M Schmidt

Gerardus C Gielis

Angle demodulator having a signal input (I) for applying an angle-modulated input carrier (A) thereto, which demodulator is coupled to a phase detection arrangement (2) to which also a quadrature detection carrier (D) frequency-coupled with the input carrier (A) is applied for demodulating the angle modulation signal, said quadrature detection carrier (D) being shifted at least substantially 90.degree. in phase relative to the input carrier (A) at the central frequency of the input carrier (A), said phase detection arrangement (2) being coupled via a low-pass filter (6) to a signal output (O). Angle demodulators of this type, which may be designed as FM quadrature or PPL angle demodulators, cause a second order interference product which is inherent in the multiplication of two carriers (A and D) in mutual phase quadrature. According to the invention, to reduce the interference, a further carrier (B), which is either in phase or in anti-phase with the input carrier (A) at the central frequency, is generated, which carrier (B) is used in the phase detection arrangement (2) for compensating said interference product.

Angle demodulator with second order interference prevention

An FM-receiver with transmitter characterization, having a tuning unit, an IF-amplifier, a demodulation circuit for demodulating a discrete transmitter characterization signal, a clock regeneration circuit, a decoding device for decoding the discrete transmitter characterization signal and a signal processing unit. The clock regeneration circuit regenerates a clock signal the period of which is obtained by dividing the frequency of the stereo pilot signal. Synchronization of the clock signal phase with the phase of the clock signal used in the transmitter is carried out by detecting, using of a periodic window signal, the average phase of the code edges in the discrete transmitter characterization signal and by choosing the phase of the regenerated clock signal to be equal thereto.

Growing community of inventors

Eindhoven, Netherlands

Harry B Schoonheijm