Abstract: There is described an electronic circuit which operates an Amplitude Locked Loop. The circuit comprises a voltage controlled amplifier, a modulus detector and an integrator combined in a feedback loop. An FM signal decoder is also described as are a number of applications of Amplitude Locked Loop.

Abstract: FM quadrature demodulator having in-phase and quadrature terminals for applying a pair of FM-modulated signals in a mutual phase quadrature thereto, having a modulation signal which is frequency-modulated on a carrier, one of the two terminals being coupled to a first input of a first phase comparison circuit and the other terminal being coupled to a second input of the first phase comparison circuit via a first phase-shifting circuit which realizes a phase shift varying with said modulation signal, the first phase comparison circuit being connected to an output of the FM quadrature demodulator via a low-pass filter.

Abstract: A demodulator alignment method and apparatus (400) employs an alignment signal generator (401-405) to generate an alignment signal (417) in response to a modulation reference signal (413). The alignment signal (417) is demodulated by a demodulator circuit (402), having a voltage controlled delay element (404) to produce a demodulated alignment signal (419) having distortion components. The demodulated alignment signal (419) is then coupled to a filter (406) which isolates the distortion components. A detector (408) is then employed to detect the isolated distortion components. Next, an error amplifier (410) compares the detected distortion to a reference (430), generates an error signal (450) and applies the error signal (450) to a sampling circuit (412).

Abstract: A signal processing device for processing an information signal, comprises a frequency modulator arranged to receive the information signal, to frequency-modulate the received information signal and to output a frequency-modulated information signal, a feedback signal generator arranged to receive the frequency-modulated information signal output from the frequency modulator means and to generate a feedback signal therefrom at a phase which is variable to be either in-phase or out-of-phase relative to the received frequency-modulated information signal in accordance with a duty in a high-level period of the received frequency-modulated information signal and at an amplitude which is variable within a range from a zero level to the same level as the received frequency-modulated information signal, and addition circuitry arranged to add the feedback signal output from the feedback signal generator to the information signal received by the frequency modulator.

Abstract: Electronic receive arrangement for receiving a modulated carrier signal, which arrangement comprises a mixer/demodulator driven with the carrier frequency fc, at least one adder included in a closed signal loop, a low-pass filter, and a pulse shaper constituted by a sigma-delta (one-bit) signal converter and driven with the sampling frequency fs and also comprises a digital decimation filter. The signal loop includes the mixer/demodulator so that the modulated carrier signal is applied to the adder and the output signal of the adder is applied to the mixer/demodulator. The signal loop also comprises a second mixer driven with frequency fc, and the frequencies fs and fc present a common multiple.

Abstract: Phase noise and drift in a broadcast communication system caused by imperfections in transmitter and receiver local oscillators used for up and down conversion of a frequency or phase modulated information signal is eliminated from a downconverted component that is provided for demodulation by adding a pilot frequency component to the modulated signal for mixing by the local oscillator in the transmitter and by frequency locking the local oscillator in the receiver, so that a signal at a frequency equal to the sum of the intermediate frequency and the pilot frequency provided by a phase-locked loop that tracks the pilot frequency component of the downconverted signal is maintained at a desired value. The downconverted signal is mixed with the sum signal provided by the phase-locked loop to provide a component for demodulation at the difference between the pilot frequency and the modulation frequency that is free from the phase noise and drift caused by the local oscillators.

Abstract: The adaptive filter for frequency modulation of the present invention utilizes an audio tone multiplexed into the baseband modulation spectrum as a pilot tone to control and determine the amount of adaptation of the effective and variable bandwidth of the filter for optimum selectivity and rejection of wideband interference or narrowband offset interference. The multiplexed tone is detected and the filter is adjusted according to the signal-to-noise ratio of the detected tone. A continuous and adaptive decrease or increase in bandwidth is produced to accommodate the actual signal bandwidth to achieve rejection of interference with minimum distortion. Additionally, the filter compensates for transmitter drift of center frequency. This filter may be used at radio or intermediate frequencies.

Abstract: A circuit arrangement which includes an FM demodulator having a delay circuit which subjects the received FM signal to a preset time delay and a signal combining circuit which combines the delayed and undelayed FM signal to derive a combined signal the mean value of which is proportional to the frequency of the FM signal. A low pass filter derives the demodulated signal from such combined signal. The proportionality factor is determined by the preset time delay, which is controllable by a control signal supplied to the delay circuit by a datum level detector which detects a selected datum level of the demodulated signal; for example, the lowest level of such signal. By controlling the time delay in accordance with such datum level, the datum level detector thereby stabilizes the maximum amplitude of the demodulated signal relative to the datum level thereof despite variations in the maximum frequency swing of the received FM signal.

Abstract: An FM demodulating circuit using a tracking filter is disclosed, in which the operation of the tracking filter following the frequency of the signal inputted therein is made more precise by using the tracking filter and an oscillator driven by a same control signal.