Abstract: An FM detector circuit includes a bridge circuit having four sections with a discriminator connected as one of the four sections. An FM intermediate frequency is applied across one pair of diagonally opposed nodes of the bridge circuit and an output is picked up across the other pair of diagonally opposed nodes of the bridge circuit. The discriminator includes a piezoelectric material that is selected to produce stable overall temperature characteristics.

Abstract: The invention relates to an anti-demodulator circuit which is fundamentally built up in the same way as a demodulator circuit but, instead of a bandpass filter as generally used in a demodulator, comprises a notch filter which receives an input signal comprising a useful signal and an interference signal, and generates a filtered signal. The notch filter has a center frequency which approximately corresponds to the frequency of the input signal so as to suppress at least a part of the useful signal. The anti-demodulator circuit further comprises a mixer circuit which receives the filtered signal and a phase-shifted input signal and supplies a demodulated output signal which substantially corresponds to the interference signal.

Abstract: A quadrant deciding section decides the quadrant to which a received signal belongs based on a baseband signal. A rotation projector rotates the received signal and projects the rotated signal to a straight line that intersects orthogonally at the origin with a straight line that bisects the decided quadrant. An integrator integrates the signal after the projection. A one-bit quantizer quantizes the integration result by deciding the sign of the integration result. A delay circuit delays the quantized signal by a predetermined time. An adder adds the decision result and the quantized signal modulo the phase 2?. A low-pass filter sequentially latches phase values after the addition with internal shift registers, converts the phase value to a prescribed specific value when the phase values that cross over 2? exist in the whole data within the registers, and averages the phase values.

Abstract: A demodulator for demodulating a modulated input signal transmitted at a carrier frequency includes a current mirror for receiving the modulated input signal and generating a first and a second current-mirror output signals of same amplitude and frequency as the modulated input signal. The demodulator further includes a first and a second switch-controlled sampling circuits connected to the current mirror for receiving the first and second current mirror output signals respectively. The demodulator further includes a switching signal generator provided for generating a first and a second switch control signals having a frequency substantially equals to the carrier frequency with a flexibly adjustable phase difference between the first and the second switch control signals.

Abstract: A voltage-to-current converter having improved third order distortion is disclosed herein for use in an FM radio system, particularly an FM radio system which employs a broadband input filter rather than a narrow band input filter. By cross-coupling a main amplifier with a second amplifier that produces more distortion and has a smaller gm, than the main amplifier, third order frequency peaks resulting from non-linear amplification of undesired signals can be prevented from interfering with a desired signal because the magnitude of the third order frequency peak is reduced.

Abstract: To ensure frequency stability of a radio frequency in a radio communication apparatus for generating the radio frequency synchronizing with a transmission path frequency of digital data transmitted from a wire digital transmission path and so on. Concerning influence of a difference of a transmission path frequency that obstructs stability of a radio carrier frequency, the difference of a transmission path frequency 12b is compared with a high-stability radio reference clock 22a, the difference frequency 17a is detected by a counter 71, and frequency offset of a radio-station-transmission signal of a local oscillator 61 is made on the basis of the differential frequency. By the operation, the influence of the difference of the transmission path frequency that obstructs the stability of the radio carrier frequency 63a can be compensated.

Abstract: An FM broadcast transmitter transmits a broadcast signal having a carrier at a broadcast frequency and sidebands, able to be transmitted at full power, within a transmission band-width around the carrier. It includes a source of a modulated FM stereo signal having a carrier at the broadcast frequency and having sidebands with a bandwidth less than the transmission bandwidth representing a stereo signal. It also includes a source of a modulated IBOC signal, having carrier pulses spaced relative to each other to represent the IBOC digital data signal encoded as a variable pulse width encoded signal, and a bandwidth within the transmission bandwidth not overlapping the FM stereo signal sidebands. A signal combiner combines the modulated FM stereo signal and the modulated IBOC signal to form the broadcast signal.

Abstract: Disclosed is a novel and improved dynamically programmable linear receiver which provides the required level of system performance with reduced power consumption. In one embodiment, disclosed is a programmable receiver coupled to a jammer detector for detecting the presence of jamming in an RF signal, the jammer detector coupled to a state machine, and the state machine having means for controlling the receiver based on the results of the jammer detector detecting the presence of jamming in the RF signal. The disclosed receiver is capable of detecting the presence of jammers, with a means to adjust the bias current downward if no jammers are present, which improves the receiver's standby time and prolongs battery life.

Abstract: A method of receiving a signal and performing a carrier recovery, the method comprising the steps of: (a) receiving a signal Xk. (b) rotating Xk by a previous correction angle &thgr;k−1 to generate a rotated signal Qk, wherein the rotation is based upon a sine and cosine of the previous correction angle. (c) mapping the rotated signal Qk to a valid decision Ak out of a constellation. (d) generating a normalized error signal &Dgr;&thgr;k,k−1 that reflects an angular difference between a correction angle &thgr;k and the previous correction angle &thgr;k−1. (e) calculating and storing a sine and a cosine of the correction angle &thgr;k, wherein the calculation is based upon &Dgr;&thgr;k,k−1, the sine of the previous correction angle &thgr;k−1 and the cosine of the previous correction angle.

Abstract: The invention relates to a digital demodulator whose architecture is adapted to multicarrier modulations (radio wave transmissions), but which remains suitable for use for monocarrier modulations (cable and satellite transmissions). With multicarrier modulations, the demodulator must carry out certain functions at a frequency of the order of sampling frequency and other functions at a frequency of the order of the symbol frequency. The invention comprises a separation of the architecture into three modules: a first module which carries out programs which are repeated with a first frequency, a second module capable of using programs which are repeated with a second frequency, and an interface module between the first and the second module. An advantage is that the memory size necessary for storing instructions for the first module is reduced. An application is for DVB standard transmission of digital TV programs.

Abstract: A method of processing a pulse response with an adaptive threshold and corresponding receiver. According to the method, an adaptive threshold is calculated that is a function of a maximum reached by the pulse response, noise, and a coefficient adjustable between 0 and 1. The processing only comes into operation for signals that exceed this threshold. Such a method may find application notably to digital radio-communications with spread spectrum.

Abstract: There are provided quadrant deciding section (101) that decides the quadrant to which a received signal belongs based on a received baseband signal; a rotation projector (102) that rotates the received signal based on a predetermined rule, and projects the rotated signal to a straight line that intersects orthogonally at the origin with a straight line that bisects the decided quadrant; an integrator (103) that integrates the signal after the projection; a one-bit quantizer (104) that quantizes the integration result by deciding the sign of the integration result; a delay circuit (105) that delays the quantized signal by a predetermined time; an adder (1) that adds the decision result and the quantized signal modulo the phase 2&pgr;; and a low-pass filter (2) that sequentially latches phase values after the addition with internal shift registers, converts the phase value to a prescribed specific value when the phase values that cross over 2&pgr; exist in the whole data within the registers, averages the phase

Abstract: Embodiments of a frequency modulated (FM) demodulator and associated methods are generally described. According to but one example embodiment, an apparatus is disclosed comprising a receiver front-end, to receive a signal from one or more antenna(e) and generate quadrature components of the received signal, and a frequency-shifted, cross-multiplied differentiator demodulator, coupled with the receiver front-end, to generate a demodulated representation of the received signal centered at a select intermediate frequency.

Abstract: The present invention relates to a demodulation structure and method for downconverting and demodulating a digitally modulated signal So, with a local oscillator means (1; 5; 8) for providing a local oscillator signal Slo a mixer means (2) for mixing said local oscillator signal Slo and said digitally modulated signal S0 in order to obtain a mixed signal, a lowpass filter means (3) for lowpass filtering the mixed signal from the mixer means (2) and an analog-to-digital converting means (4) for converting the filtered signal from the lowpass filter means (3) into a downconverted and demodulated digital signal Sl, whereby the local oscillator signal is set in respect to the modulated digital signal so that the downconverted and demodulated digital signal output from the analog-to-digital converting means comprises to serially arranged information parts. The present demodulation structure provides a very simple structure with improved amplitude and phase imbalances.

Abstract: A radio FM receiver is provided with a receiver portion with quadrature channels for converting received radio frequency signals into center frequency quadrature signals, a center frequency filter circuit connected to the former for suppressing undesirable image frequencies, and a first quadrature PLL demodulator for demodulating the obtained center frequency quadrature signals, said PLL being tuned to the carrier frequency within the selected frequency band. An error detector is furthermore present for detecting amplitude and phase errors in the quadrature channels, which error detector in response to the quadrature components of the center frequency signals, the quadrature signals of a VCO in the quadrature PLL demodulator, and the filtered difference said quadrature components of the center frequency signal, supplies amplitude and phase correction signals to a quadrature channel correction network which is provided between the filter circuit and the quadrature PLL demodulator.

Abstract: A digital FM demodulator converts a digital FM input signal to a demodulated signal, detects the amplitude of the digital FM input signal, generates a corresponding amplitude signal, and adjusts the amplitude of the demodulated signal according to the amplitude signal, thereby compensating for variations in the amplitude of the digital FM input signal and removing amplitude distortion from the demodulated signal. This reduces the performance requirements of, for example, a low-pass analog filter preceding the digital FM demodulator in an FM radio broadcast receiver, permitting the analog filter to be implemented in a semiconductor integrated circuit.

Abstract: A digital FM demodulator employs a baseband phase lock loop (BBPLL), which is particularly effective for long range reception, for combining and demodulating a pair of signals represented by the mathematical expression A(t)ej&thgr;(t) to result in an approximation of d&thgr;/dt. This approximation is then subjected to an inverse of the linear approximation of the frequency response of the BBPLL that produces a very accurate &thgr;. This is conveniently achieved with a IIR filter whose transfer function happens to be the same as the inverse of the linear approximation of the frequency response of the BBPLL. The derivative is then taken of &thgr; to produce a very accurate d&thgr;/dt, the desired result for the output of an FM demodulator. To aid operation of the BBPLL, the incoming digital intermediate frequency is upsampled by a combination of sample and hold and FIR filtering prior to being processed by the BBPLL.

Abstract: An FSK receiving apparatus has, as means for performing offset correction upon a demodulated base band signal, a second low pass filter 9 for integrating the demodulated base band signal; a window comparator for detecting a DC offset component in an output voltage from the second low pass filter 9; an up/down counter 11 for incrementing or decrementing a count value on the basis of the output of the window comparator 10; a clock generating portion 13 for generating a timing signal for counting operation in the up/down counter 11; a reference voltage generating portion 12 for generating a reference voltage for a comparator 7 on the basis of the output of the up/down counter 11; and a charging circuit 22 for supplying a reference voltage in the last frame to the second low pass filter 9 so as to charge the second low pass filter 9 with the last-frame reference voltage and set an initial value of the second low pass filter 9.

Abstract: Certain embodiments of the present invention provides a system and method for SAP FM demodulation. The system includes a bandpass filter for isolating the SAP signal, a Hilbert filter to produce a copy of the SAP signal phase shifted by 90 degrees, an FM demodulator for demodulating the SAP signal using the phase shifted SAP signal and a delayed SAP signal, and a lowpass filter to eliminate noise from the FM demodulated SAP signal. The system may also include an automatic gain control for normalizing amplitude of FM demodulator input signals. The digital FM demodulator uses a simplified approximation using non-unity delay for simplified demodulation of frequency modulated signals.

Abstract: A mixer circuit with improving characteristic of image rejection by compensating mismatch in a spurious rejection mixer circuit (SRM) used in a transmitter is provided. The mixer circuit according to the present invention comprises an up conversion unit for modulating a base-band input signal to a RF signal, a down conversion unit for converting an output signal from the up conversion unit to a base-band output signal, mismatch estimating means for determining a mismatch compensation value by which spurious component in an output signal from the down conversion unit is minimized, wherein the spurious component results from mismatch in the up conversion unit, and mismatch compensating means for compensating the mismatch in the up conversion unit by using the mismatch compensation value determined by the mismatch estimating means.

Abstract: A high frequency super regenerative direct detector includes a power supply and a signal detecting circuit arrangement electrically connected thereto. The signal detecting circuit arrangement, which is a transistor control system, includes a high frequency by-pass circuit, a LC tank circuit configured to be tuned at a pre-tuned frequency and to receive an incoming signal so as to generate an oscillator frequency, ranging from 800 MHz to 960 MHz, a quenching circuit coupling with the high frequency by-pass circuit to generate a quenching frequency, and a transistor circuit device configured to incorporate the oscillator frequency into the quenching frequency in such a manner that when the incoming signal matches the pre-tuned frequency a timing to achieve a saturated level of the quenching frequency is faster than no signal period, and a modulation frequency of the incoming signal is detected out from the signal detecting circuit arrangement.

Abstract: A demodulating circuit 1 contains an electric field level detector 2 for detecting an electric field strength from a received modulation signal, comparators 3a to 3n for outputting electric field strength information PS, a detector 5 for outputting a detection signal corresponding to a modulation signal, both a low-pass filter 6 and a digital filter 12 for removing a noise component from the detection signal, and a data comparator 7 for comparing the detection signal with a reference voltage to output a digital signal. This demodulating circuit 1 further includes a control circuit 4 for controlling a cutoff frequency used in a digital filter 12, an output voltage amplitude of the detector 5, and the reference voltage of the data comparator 7 in accordance with both the electric field strength information PS and control condition information PC saved in an EEPROM 11 and supplied from a CPU 10, and also a judging circuit 9 for judging the digital signal at preselected timing to produce a demodulation signal.

Abstract: An analog modulation technique where the message information is contained in the timing of phase reversal zero crossings in the transmitted signal. In the preferred implementation a bias signal is added to an information signal and the composite signal hard limited to produce a square wave. The square wave is used to switch the phase of a carrier signal so that phase reversals occur in correspondence with the change in polarities of the square wave. A demodulation technique is also disclosed.

Abstract: A circuit (100) for generating a ratio signal indicating a ratio of frequency error to signal magnitude of an input signal includes an FM ratio detector (110) and a sigma-delta analog-to-digital converter (130). The FM ratio detector (110) is responsive to the input signal and generates a magnitude signal and an error signal. The magnitude signal is representative of a magnitude of the input signal and the error signal is representative of a frequency error of the input signal relative to a preselected frequency. The sigma-delta analog-to-digital converter (130), which is responsive to the filtered magnitude signal and the filtered error signal, generates a stream of logic “1's” and logic “0's” that are indicative of a ratio of the filtered error signal to the filtered magnitude signal. Thus, the sigma-delta analog-to-digital converter generates the ratio signal (132).

Abstract: A cost effective digital stereo decoder (216) for Digitized Intermediate Frequency (DIF) FM radio receiver (100). After FM demodulation (212), a multiplex signal (MPX) at a high sampling rate is mixed with free-running local quadrature mixers (308, 320) to shift the (L−R) stereo signal to baseband. The MPX signal is also mixed with a free-running locally generated carrier signal to translate an embedded 19 KHz pilot tone signal to 1 KHz. The pilot tone signal is decimated to a low sampling rate to permit a phase-lock loop (PLL) to be applied to the lower rate signal to estimate the phase of the pilot signal. An FM blender controller is used to attenuate high frequency noise and improve audio quality. The receiver may be implemented in software and be customer configurable to have various operating characteristics.

Abstract: A differential FM detection of signals uses in-phase and quadrature phase signal components of a received signal in the detection process, wherein the in-phase and quadrature phase signal components are at a low intermediate frequency (IF). The in-phase and quadrature phase signal components are each amplitude limited, sampled at a prescribed sampling rate and filtered in a prescribed manner. Delayed versions of the filtered in-phase and quadrature phase signal components are generated and, then, signal products are generated of the delayed in-phase signal component and quadrature phase signal component, and the delayed quadrature phase signal component and in-phase signal component. The algebraic difference of the generated signal products is obtained to yield the desired data signal, e.g., symbols.

Abstract: A receiver architecture includes a selectivity filter (206) for selectively passing a wanted channel and rejecting unwanted channels. The selectivity filter has a filter BT of about one-half the BT of the transmitter filter. A discriminator (208) is coupled to the selectivity filter for converting received symbols from the frequency domain to the time domain symbols. A symbol recovery processor (210) is coupled to the discriminator for recovering the symbols through a two-state maximum likelihood sequence estimation (MLSE) technique in which templates are optimized with a BT substantially less than the BT of the transmitter filter.

Abstract: This invention discloses a demodulation method. The method includes steps of: A) Receiving a modulated input signal having an input signal frequency. B) Generating a first switch control signal at a first switching frequency substantially equal to the input signal frequency. C) Generating a second switch control signal having the same frequency as the first switch control signal and having a phase that is approximately 90 degrees different from a phase of the first switch control signal. And D) Controlling at least two switching circuits with the first and second switch control signals for obtaining at least two sets of sampled amplitudes of the input signals for generating switching output signals for each of the switching circuits defined by subtracting the sampled amplitudes when the first switch control signal is high by the sampled amplitudes when the first switch control signal is low for each of the switching circuits to generate demodulated output signals for the modulated input signal.

Abstract: Receiver for enhanced performance for CDMA radio transmission comprising a Rake receiver (1) with a path searcher (3), a channel estimator (4) and a combiner (5) for selecting optimal channels paths where the path searcher (3) selects a set of path delays (7) where at least two path searchers (3a,3b) are connected in way that the output of the first path searcher (3a) is linked to one input of the second path searcher (3b).

Abstract: A circuit (100) for generating a ratio signal indicating a ratio of frequency error to signal magnitude of an input signal includes an FM ratio detector (110) and a sigma-delta analog-to-digital converter (130). The FM ratio detector (110) is responsive to the input signal and generates a magnitude signal and an error signal. The magnitude signal is representative of a magnitude of the input signal and the error signal is representative of a frequency error of the input signal relative to a preselected frequency. The sigma-delta analog-to-digital converter (130), which is responsive to the filtered magnitude signal and the filtered error signal, generates a stream of logic “1's” and logic “0's” that are indicative of a ratio of the filtered error signal to the filtered magnitude signal. Thus, the sigma-delta analog-to-digital converter generates the ratio signal (132).

Abstract: Squelch circuitry for narrow band audio receivers which uses a sub-audible tone or coded signal to modulate the intermediate frequency in accordance with the presence of a desired broadcast signal and then detects the sub-audible tone frequency or coded signal in the modulated IF frequency to control the audio output of the receiver to an off condition when there is excessive noise.

Abstract: Signal levels of received signals are detected within a plurality of different frequency bands by a first electric field strength detecting means 15 and a second electric field strength detecting means 16, then it is detected by an adjacent wave detecting means 17 based on this output signal whether or not adjacent waves are contained, then a filter controlling signal 19 is output to a first I low-pass filter 9a and a first Q low-pass filter 10a from a baseband filter controlling means 18 according to whether or not the adjacent waves are contained, whereby low-frequency cut-off frequencies of the first I low-pass filter 9a and a first Q low-pass filter 10a are switched and controlled. Accordingly, a receiving sensitivity can be improved by reducing an influence of an adjacent wave and a tolerance for frequency offset of an oscillation frequency of a local oscillator relative to a carrier frequency of a received signal can be enhanced.

Abstract: The direction-of arrival estimation by means of a subspace-based algorithm such as MUSIC or ESPRIT is formed by using reduced-bandwidth signals as compared with communication signal waves. The narrower-bandwidth signals is obtained by each mobile telephone transmitting a modulated version of a lower-transmission rate test signal as well as a communication signal wave or by band-pass filtering the received communication signal waves in a base station. A direction-of-arrival estimation is formed by using a reduced number of signals for the direction-of arrival estimation. The number of direction-of-arrival estimating signals is reduced by discarding a part of the received signals, by multiplexing the received signals by the sub-array and forming a direction-of arrival estimation for each sub-array, or by using an additional array antenna having a reduced number of elements.

Abstract: A television receiver includes a tuner for receiving either analog or digital signals. Separate analog and digital demodulators are selectively coupled to the tuner through an RF switch that is controlled by a sync detector in the output of the analog demodulator. The selected one of the demodulators develops an AGC signal that is coupled to the tuner through the RF switch. In one embodiment, a two pole RF switch is used with one pole switching the IF signal and the other pole switching the AGC signal In another embodiment, a single pole RF switch is used with the tuner signal and the AGC signal being multiplexed through the switch. This is accomplished by the provision of a high frequency path and a low frequency path between each of the RF switch and the tuner, the RF switch and the analog demodulator, and the RF switch and the digital demodulator.

Abstract: A demodulation circuit can demodulate a serial data and an infrared data and can discriminate between the serial data and the infrared data. An edge detection circuit detects an edge of an infrared input and the edge signal and the serial data are taken by an OR circuit. An OR output and a total tap number signal are input to a LPF. The LPF has a function for outputting a demodulation output signal and the operation execution signal. By the operation execution signal, demodulation of the infrared input and demodulation of the serial input are discriminated by a data discrimination circuit. By this, an UART for reproducing the infrared data and the serial data is not required separately and can be made common.

Abstract: The above object of the present invention can be achieved by an FM demodulator, into which an FM signal is inputted, for demodulating the inputted FM signal and outputting a digital FM demodulated signal.

Abstract: A demodulator circuit for demodulating a frequency modulated input, which includes a detector (14) that is operable to produce a demodulated signal from an incoming frequency modulated signal. A tuning circuit (19) is connected to the detector and operable to vary the frequency response characteristics of the detector. An auxiliary detector (25, 26) is connected to receive a reference frequency signal and to provide an auxiliary tuning signal to the detector on the basis of detection of the reference frequency signal.

Abstract: An apparatus and system for decoding colliding data transmissions utilizing an at will transmission protocol is disclosed. An apparatus for decoding an analog signal includes an input terminal, a data bus, a first decoder connected to the input terminal and data bus, configured to receive an analog signal, decode the signal into a first message and output the message to the data bus, a second decoder connected to the input terminal and data bus and configured to receive an analog signal, determine whether the analog signal includes a second message, decode the signal into a second message and out put the message to the data bus. A microprocessor operatively connected to the first and second decoders directs the second decoder to search for a colliding second transmission immediately after the first decoder has begun to decode a first transmission. If colliding second signal captures the receiver as the first transmission is decoded, the second decoder decodes and outputs the second message intact.

Abstract: A digital FM demodulation circuit which samples an input analog FM signal and digitally detects the sampled input signal has an arctangent circuit into which a second signal that is delayed from the sampled input signal by a constant time, and a third signal that is different in phase by 90 degrees from the second signal are input, and which outputs a corresponding arctangent value based on a result of a division of the two input signals. The arctangent circuit has: roundoff means for sequentially rounding the division result to one of plural typical values; and a ROM address unit for performing a control in which an arctangent value corresponding to the rounded typical value is selected from a ROM table containing arctangent values of the typical values, and the selected arctangent value is output.

Abstract: A demodulator circuit for demodulating a frequency modulated input signal includes a filter (12) for receiving an incoming input signal and for providing a filtered output signal, a detector (16) for receiving the filtered output signal, and for producing a demodulated output signal therefrom, a tuning circuit (18, 20) which is operable to introduce a test signal into the demodulator circuit in the absence of an incoming input signal, and to vary the frequency response characteristics of at least one of the filter and detector in response to the test signal.

Abstract: A technique for demodulating a message signal from an angle modulated carrier signal. A noncoherent, independent, periodic reference is generated to have a predetermined phase characteristic and which is noncoherent with and independent of the angle modulated carrier signal. The phase of the reference is then compared with the phase of the carrier to determine the message signal on the angle modulated carrier. The phase of the noncoherent, independent, periodic reference is associated with a measured value for the reference. The phase of the angle modulated carrier signal is associated with a voltage value for the angle modulated carrier signal. These values are measured and then compared to determine the message signal on the modulated carrier signal. Time variations of the comparison of values are directly related to the message signal in the case of a PM carrier. Changes in the time variations of the voltage comparison are related to the message signal for a FM carrier.

Abstract: A method of demodulating an FM carrier wave and an FM demodulation circuit are described which use a phase locked loop. The phase locked loop is tuned to a selected carrier wave frequency including the step of selecting a setting of the variable gain circuit in the phase locked loop to select desired loop gain.

Abstract: The invention provides an automatic frequency control (AFC) method and circuit for use with a receiver by which deterioration of the reception characteristic of the receiver due to frequency error of the reference oscillator (e.g. a VCO) of a quasi-synchronous detection circuit arising from initial deviation, aging, or temperature characteristics is suppressed. During operation of the receiver, only when frame synchronization is established, the set value that the frequency control circuit determines for the VCO is periodically stored into a non-volatile memory together with current ambient temperature information of the VCO.

Abstract: A FSK demodulator which uses the combination of a digital phase comparator and a digital controlled oscillator (DCO) in the form of a state machine to demodulate an FSK signal. The phase comparator compares the phase of the FSK signal with the output of the DCO to provide a signal to the DCO having a level dependent on the phase relationship between the two signals at the input to the comparator. The demodulator also includes a filter to obtain the data from the signal at the output of the comparator.

Abstract: An approach for demodulating a frequency-modulated signal involves processing a frequency-modulated signal with a phase shifter network to provide a demodulated signal that has a relatively constant amplitude around the center frequency of the frequency-modulated signal and that exhibits a relatively linear phase change over an operational frequency range. Embodiments of the invention include a phase shifter network, using N number of cascaded all-pass filters, that receives as an input a limited amplitude signal and outputs a phase-shifted limited amplitude signal that is mixed with the limited amplitude signal. The phase shifter network may also comprise a low-pass bessel filter.

Abstract: A frequency demodulator of the present invention includes: an amplification section for receiving a frequency-modulated signal and amplifying the frequency-modulated signal based on a gain so as to produce a digital signal having a predetermined level and an inverted signal of the digital signal; a digital demodulation section for receiving the digital signal and frequency-demodulating the digital signal; an amplitude detection section for receiving the digital signal and the inverted signal of the digital signal, and detecting maximum amplitude values of the digital signal and the inverted signal for a predetermined period of time so as to produce an amplitude signal in proportion to the maximum values; and a gain controlling section for varying the gain based on the amplitude signal.

Abstract: An FM demodulator circuit includes a filter (10) and a detector (14) for receiving a frequency modulated input signal and for providing a demodulated output signal. A tuning circuit (19) is provided for tuning the frequency characteristics of the filter and of the detector. A DC offset estimator (18) is connected to the output of the detector to produce an offset signal representing the estimated DC offset of the demodulated output signal, and to provide the offset signal to the tuning circuit. The tuning circuit is operable to tune the frequency characteristics of the filter and detector in dependence upon the offset signal.

Abstract: In a frequency discriminator for a direct conversion receiver having a simple construction, in which operations for FM demodulation by direct conversion are simplified, two-signal components I and Q, which are inphase and quadrature, respectively, in a base band, obtained by direct conversion of an FM signal by means of a local oscillator, a 90.degree. phase shifter, multipliers, LPF and AMP are amplified to a predetermined amplitude and thereafter converted into digital signals by means of A/D converters. These digital signals are given to differentiators to obtain differentials (finite differences) thereof. These values are squared by means of squarers and squares thus obtained are added by means of an adder. An output of the adder is applied to a device for extracting square root to obtain a demodulation output of the FM signal. An ROM may be used in lieu of the squares and the device for extracting square root.

Abstract: A pulse counting FM demodulator includes a differentiating circuit that differentiates an FM intermediate-frequency signal to produce a differentiated pulse signal. A trigger signal is generated based on the differentiated pulse signal and is used to control the charging and discharging of a capacitor that is included in a monostable multivibrator. The charging and discharging of the capacitor provides an output level inverting operation. A variable current source supplies the capacitor with a charging current that is varied in response to an externally supplied control voltage, and an output circuit provides a demodulated output signal having a level corresponding to the output level inverting operation in the monostable multivibrator.

Abstract: A method for multi-mode autonomous selection demodulation is disclosed. The method includes the step of providing a receiver with demodulation circuitry (110-112) capable of demodulating a plurality of waveform modulation techniques. The method also includes the step of receiving a modulated information waveform and a preamble associated with the modulated information waveform. The method also includes the steps of matching the preamble against a predefined set of patterns corresponding to a plurality of modulation techniques at the receiver and identifying a corresponding demodulation technique. Additionally, the method configures the demodulation circuitry (110-112) to apply the corresponding demodulation technique to the modulated information waveform.