U.S. Philips Corporation

Koninklijke Philips Corporation N.v.

Hermann Jabs

Wilfried E Knop

Winfrid B Jansen

Juergen Marschner

Michael Bisping

Arrangement for measuring the temperature of an electronic circuit

In radio receivers, ceramic filters are used for filtering the received frequency band. The limitation of the frequency band in the higher frequency range leads to an asymmetrical crosstalk between the right and left audio channel after decoding in the stereo decoder. These transmission errors are compensated by an adjustable high-pass filter. This high-pass filter precedes the stereo decoder. High-pass filters using potentiometers cannot be integrated. Furthermore, ageing phenomena occur in potentiometers so that the transfer function changes. A high-pass filter with a variable capacitor can neither be integrated easily. Therefore, an arrangement is used in which, after a first amplification of the signal to be filtered, this signal is divided into two signal currents and the amplitude and phase of a sub-current are corrected. This corrected sub-current is added to the main current at a sum node. The sub-current is applied via a voltage divider unit to an amplifier stage having a plurality of inputs. A corresponding input, to which a partial voltage is assigned, is selected via a selection unit. The output of the amplifier stage supplies a changeable voltage which is present at the capacitor. By selecting the partial voltage, the transfer function of the high-pass filter can be adjusted. Transmission errors caused by the low-pass behavior of the ceramic filters are thereby reduced so that the stereo decoder receives a signal which can be accurately separated in the left and the right channel. This circuit arrangement can be integrated in that an adjustable capacitor is realized which consists of a voltage divider, an amplifier stage and the capacitor.

Circuit arrangement for an adjustable high-pass filter

A circuit for reducing the distortion in an FM quadrature demodulator. A non-linear circuit stage is connected after the quadrature demodulator, whose characteristic has an inverse curve form like the demodulator characteristic. If the FM quadrature demodulator uses a resonant circuit to generate a frequency-dependent phase shift and has two outputs in phase opposition, the non-linear circuit stage can be formed by two diode branches through which the output currents of the quadrature demodulator flow. The voltage difference at these two diode branches supplies the output signal with the non-linear distortions largely removed.

FM quadrature demodulator with distortion compensation

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Hamburg, Germany

Hermann Jabs