U.S. Philips Corporation

Motorola Corporation

Wilfried E Knop

Knud Holtvoeth

Edgar Herbert Callaway, Jr

James G Mittel

Burkhard Dick

Andreas H Wichern

Vance H Peterson

Hermann Jabs

Winfrid B Jansen

A receiver has a crystal oscillator (10) whose frequency can be adjusted in response to temperature compensation (TC) and automatic frequency control (afc) signals. The TC and afc signals are summed and applied to an op-amp (70) having a fixed gain functioning as a current to voltage converter. An output of the op-amp (70) is applied to the crystal oscillator (10). If the receiver is switched--on and--off in accordance with say a time division protocol, the output of the op-amp (70) is applied by way of a switch (72) to a storage circuit (30,C) which when the switch is open applies a bias voltage on the crystal oscillator (10) to maintain its output frequency.

Radio receivers

A receiver (100) for receiving an input signal and generating an output signal therefrom has a switchable gain circuit (104) with a stepwise variable gain control (118), a local oscillator (106) and an automatic gain control (AGC) detector (114) with a response for detecting a level of the output signal and generating an AGC signal indicative of the level of the output signal and a state machine (116) being responsive to the AGC signal generating a control signal at the stepwise variable gain control to increase or decrease a gain of the switchable gain circuit in discrete stepwise steps.

Selective call receivers with stepwise variable gain control

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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Appen, Germany

Wilfried E Knop