U.S. Philips Corporation

Nxp B.v.

Koninklijke Philips Corporation N.V.

Thomas Hafemeister

Joachim C Brilka

Wolfgang Weltersbach

Disclosed is an intermediate frequency processing device for processing both analogue and digital television intermediate frequency signals including vision and sound intermediate frequency signal components, comprising an intermediate frequency signal input for receiving digital or analogue intermediate frequency signals, a processing section, coupled to said intermediate frequency signal input means, for processing intermediate frequency signals, and an output for outputting signals processed in said processing section. The processing section comprises a first band pass filter () connected to said intermediate frequency signal input, and at least two parallel processing portions (----) coupled in parallel to said band pass filter (), wherein each of said processing portions includes an inphase quadrature processing means ().

Intermediate frequency processing device for processing both analogue and digital television intermediate frequency signals

A down-converter for processing frequency signals, preferably received, particularly digital, television signals, comprising two, preferably identical mixer stages () for down-converting the signal, a local oscillator () controlling the mixer stages by a 90&#xb0; phase shift, a complex filter () which couples the output signals of the mixer stages () by means of a complex filtering method in such a way that the signal components outside a predetermined useful band are substantially suppressed, an adjusting device () for adjusting the frequency of the local oscillator () and a subsequent low-pass filter.

Down-converter

A circuit arrangement for demodulating an intermediate-frequency video signal, comprising a video demodulator ( ) and a phase-locked loop ( ) formed as a Costas loop, in which an output signal of a controllable oscillator ( ) arranged in the Costas loop and the intermediate frequency video signal are coupled to the video demodulator ( ), should always supply a demodulated video signal of a predetermined polarity, independent of overmodulation occurring in the intermediate-frequency video signal. To this end, this circuit arrangement is characterized in that a polarity inverter ( ) is provided, which is preceded by the video demodulator and by means of which the polarity of the demodulated video signal is invertable in dependence upon a control signal supplied by a polarity detector ( ), and in that the polarity detector ( ) determines the polarity of the output signal of the video demodulator ( ) or of the polarity inverter ( ) and, in dependence upon the determined polarity, controls the polarity inverter ( ) by means of the control signal in such a way that the demodulated video signal at the output of the polarity inverter ( ) has a predetermined polarity.

Circuit arrangement for demodulating an intermediate-frequency video signal

In a circuit arrangement for demodulating an intermediate-frequency video signal generated while using a Nyquist edge, having a phase-locked loop (,) including a phase detector (,), a loop filter (,) and a voltage-controlled oscillator (,), and a video demodulator (,), the intermediate-frequency video signal being applied to the phase detector (,) and the output signal of the phase-locked loop (,) being applied to the video demodulator (,), which converts the intermediate-frequency video signal into a baseband video signal, phase fluctuations contained in the carrier of the intermediate-frequency video signal due to its generation while using a Nyquist edge are compensated in that the phase comparator (,) operates, by approximation, independently of modulation in the control range of the intermediate-frequency video signal, in that the baseband video signal is present in an inverted form with respect to the intermediate-frequency video signal, and in that a correction signal is derived from the baseband video signal by at least a feedback capacitor (,), this correction signal having signal components of opposite amplitude and phase position to those contained in the intermediate-frequency video signal and caused by the Nyquist edge, and is applied to the loop filter (,).

Circuit arrangement for demodulating a video signal (IF signal) which is frequency-modulated on an intermediate-frequency carrier oscillation, including a first demodulation stage (a frequency or phase demodulator) for multiplicatively combining the IF signal with a carrier oscillation of a controllable oscillator and for supplying a first output signal, a second demodulation stage (a frequency or phase demodulator) for multiplicatively combining the IF signal with the carrier oscillation phase-shifted by a quarter period of the intermediate-frequency carrier oscillation, and for supplying a second output signal, a first filter stage for low-pass filtering the first output signal and for supplying a third output signal, a multiplier stage for multiplicatively combining the second output signal and the third output signal to form a fourth output signal, a superposition stage for forming a seventh output signal by additively combining a fifth output signal and a sixth output signal derived from the second output signal and the fourth output signal, and a second filter stage for deriving a control signal from the seventh output signal for controlling the frequency and/or phase of the controllable oscillator. To ensure a reliable operation, also upon overmodulation, this circuit includes a first coefficient member for deriving the fifth output signal from the second output signal, and a second coefficient member for deriving the sixth output signal from the fourth output signal, the signal applied to each coefficient member being multiplied by a predeterminable coefficient (k1, k2) for forming the signal derived therefrom, wherein the coefficient (k1) of the first coefficient member being chosen is larger than the coefficient (k2) of the second coefficient member.

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Hamburg, Germany

Thomas Hafemeister