Abstract: The invention relates to a demodulator to demodulate frequency-modulated signals FM including a phase locked loop PLL including at least a phase detector, a loop filter and a voltage controlled oscillator function VCO?, characterized in that said voltage controlled oscillator function VCO? has modifiable gain. The invention allows to eliminate drawbacks presented by the conventional use of a complex gain modifiable amplifier at the input of demodulated signal processing means. Application: demodulation of modulated signals: wireless phone, home network.

Abstract: Demodulation apparatus includes a transversal filter characterized by coefficients adjusted by a coefficient determiner responsive to a constant modulus error signal and variable mode error signal related to the output of a spectral mean frequency detector having its input coupled to the output of the transversal filter.

Abstract: A circuit and method for differential slope demodulator circuit are shown that utilize amplitude stabilizing of a frequency modulated signal to obtain an amplitude stabilized signal. Also shown is bandpass filtering of the amplitude stabilized signal for a first frequency that is offset by a shift frequency below an intermediate frequency, to obtain a first filtered signal and bandpass filtering the amplitude stabilized signal for a second frequency that is offset by the shift frequency above the intermediate frequency, to obtain a second filtered signal. The circuit and method further operate by detecting an envelope of the first filtered signal to obtain a first envelope signal, detecting an envelope of the second filtered signal to obtain a second envelope signal, and differencing the first and second envelope signals to obtain a demodulated output signal.

Abstract: Demodulation apparatus includes a transversal filter characterized by coefficients adjusted by a coefficient determiner responsive to a constant modulus error signal and variable mode error signal related to the output of a spectral mean frequency detector having its input coupled to the output of the transversal filter.

Abstract: A digital baseband (DBB) radio frequency (RF) receiver used for receiving and processing a wireless communication signal. The DBB receiver includes a demodulator, first and second analog low pass filters (LPFs), first and second digital gain control circuits, and a digital time domain compensation module which removes group delay variation distortion, introduced by the first and second analog LPFs, from real and imaginary signal components of the communication signal.

Abstract: A method and a circuit for the digital correction of a frequency of a signal, especially for use in a transmitter/receiver circuit include rotating a signal “pointer” (i0, q0) using a CORDIC algorithm, through a predetermined angle in a complex I/Q plane corresponding to a correction frequency. The CORDIC algorithm includes micro-rotation blocks corresponding to N stages, and a character table and a register.

Abstract: A method and a demodulator for processing a Fast Fourier Transform using data blocks include a Fast Fourier Transform (FFT) coprocessor and a digital signal processor (DSP). The FFT coprocessor includes a start function and a computation function (F_FFT). The start function is adapted to generate a start signal each time a first data of a new block is received. The DSP includes a time error function which indicates to the start function for how much data it has to wait before a new start signal is generated.

Abstract: A demodulating semiconductor integrated circuit device used in a wireless communication system of an FM-modulation scheme, wherein a circuit for canceling a frequency offset is made of a digital circuit, so as to make a high-accuracy decision as to received data and prevent error frequency offset cancel due to a pseudo pattern contained in the received data. Consequently, a high-accuracy received data decision is carried out.

Abstract: A non-coherent frequency shift key demodulator comprising an oversampling device, a chain of registers, and a threshold device is disclosed. The oversampling device receives an input digital non-coherent frequency shift signal, and examines for transitions therein, and thereby generating data bit signals in the form of logic high level ‘1’ or logic low level ‘0’ accordingly. The chain of registers receives, counts and stores the number of 1's data bit signals. Following, the threshold device compares the stored number of 1's in the chain of registers with a predetermined threshold value to extract the digital signal of the input digital non-coherent frequency shift signal. The non-coherent frequency shift key demodulator, by the use of a simple circuit and implementation, combats miscellaneous system impairments, such as frequency offset, and further support multi-rate transmission.

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 demodulator has a resistor and a capacitor that may be subject to tolerances. For tolerance correction, the FM demodulator is preferably supplied with a reference frequency, which corresponds to the nominal mid-frequency of the demodulator, which is a function of the resistor and the capacitor. Any discrepancy between the actual mid-frequency of the demodulator and its nominal mid-frequency leads to the production of a voltage that differs from a nominal voltage at the output. A detector detects this error and adjusts the values of the resistor or capacitor until the error between the nominal voltage and the voltage is zero or is a minimum. The described principle can be used, for example, in integrated mobile radio receivers.

Abstract: An FM demodulator has a differential output demodulator for receiving an FM signal and for outputting a positive differential signal and a negative differential signal of a demodulated signal of the FM signal, a DC offset detector electrically connected to the differential output demodulator for generating a DC offset signal according to peak signals of the positive differential signal and the negative differential signal, and a correction circuit electrically connected to the differential output demodulator and the DC offset detector to compensate for the demodulated signal according to the DC offset signal.

Abstract: A demodulator includes a reference signal generator for generating a reference signal, an FM demodulation circuit for demodulating a modulated signal, and a control circuit for controlling demodulation sensitivity of the FM demodulation circuit. The control circuit controls the demodulation sensitivity of the FM demodulation circuit so that an output signal, obtained when the reference signal from the reference signal generator is inputted to the FM demodulation circuit, becomes a specified value. This structure can stabilize the demodulation sensitivity of the demodulation circuit while restraining increases in circuit scale and current consumption, and can adjust dispersions in the demodulation sensitivities of the respective ICs due to relative errors of a resistance value of a resistor and a capacity value of a condenser in an IC, the resistor and the condenser constituting the demodulator.

Abstract: There is a need for an inexpensive, high-performance, fully-integrable, multi-standard transceiver. The invention provides a topology that satisfies this need, consisting of: an active mixer, followed by a high pass filter, and a passive mixer. The input signal is modulated up, or demodulated down, using a pair of complementary, aperiodic mixing signals. The use of aperiodic mixing signals allows a fully-integrated transceiver to be built. Several embodiments of the active mixer are also presented, including those having electrically-adjustable performance and allowing multiple RF signal inputs. This allows the topology of the invention to be employed in multi-band, multi-frequency applications, while still providing high performance.

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 frequency discriminators (FD) and frequency modulation (FM) demodulators, utilizing single sideband (SSB) complex conversion directly to zero IF, suitable for direct demodulation at high frequencies of analog FM or digital FSK modulated signals, as well as for high speed frequency discrimination (or frequency comparison) in applications such as frequency acquisition in frequency synthesizers. The complex SSB down-converter consists of a quad of mixers and quadrature splitters in both the signal path and local oscillator (LO) path. Each mixer receives both the signal and the LO, each either in-phase or quadrature. The outputs of mixers are combined in pairs, to produce the SSB in-phase (I) baseband signal and the SSB quadrature (Q) baseband signal. Both I and Q signals are then delayed, each multiplied by un-delayed version of the other one. The multiplication products are summed together, to produce an FD error signal, or an FM demodulated signal at the output.

Abstract: An FM signal receiver for use in receiving a burst signals as in a Bluetooth system includes a BPF and a frequency-demodulation circuit, each having, for example, a phase shifter, which is constructed from similar or related circuitry so as to enable adjustment of the frequency characteristics of the BPF and frequency-demodulation circuit through an identical control signal. A short-circuit switch is disposed linking the input and output terminals of an amplifier. A control circuit opens the switch in a receiving operation and closes the switch in an adjusting operation. Thus, adjustment is carried out without using the amplifier. Therefore, an amplifier offset does not affect the frequency-to-voltage conversion by the frequency-demodulation circuit in the adjusting of the frequency-demodulation circuit and similar adjusting of the BPF. Thus, the BPF is prevented from being incorrectly adjusted due to the offset. The BPF characteristics are suitably adjusted.

Abstract: An FM demodulator compensates for DC offset by detecting the positive peak value of the frequency demodulated signal (D1, C2, R1) and the negative peak value of the frequency demodulated signal (D2, C3, R2). The mean of the positive and negative peak values is determined (C1, R3, R4) to produce an estimation of a DC offset value. This estimated DC offset value is then used to compensate for DC offset in the frequency demodulated signal. This circuit has the advantage of enabling the DC offset to be calculated without requiring complex digital signalling processing, and without requiring the input signal to have a zero mean. A signal strength signal RSSI may be used to disconnect the DC offset compensation circuitry during periods when the input signal strength is weak.

Abstract: A method and an apparatus for synchronous demodulation of the multiply modulated rotation rate signal of a rotation rate sensor which comprises a spring-mass system that oscillates at its natural resonant frequency, and at least one capacitor for ascertaining a Coriolis effect acting on the spring-mass system or a rotation rate, the rotation rate being ascertained by a time-variable capacitance change, brought about by the rotation rate, of the at least one capacitor by multiple demodulation of a multiply modulated electrical signal that comprises a time-variable first electrical signal and a second electrical signal, overlaid thereon, at the natural resonant frequency of the rotation rate sensor, the amplitude of the second electrical signal of the time-variable capacitance change of the at least one capacitor being correspondingly modulated.

Abstract: In a circuit arrangement for demodulating signals, particularly frequency-modulated signals, in which a limiter, to whose input the signals to be modulated can be applied, is followed by a demodulator from whose output the demodulated signals can be derived, the outputs of the demodulator and the limiter are connected to a respective input of a mixer whose output is connected to the input of the limiter via a low-pass filter.

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: An FM demodulator for reproducing data by performing FM demodulation of a received RF signal in a Bluetooth transmission system is provided. The FM demodulator includes a frequency discrimination unit and a level determination unit. The FM demodulator frequency-discriminates the RF signal, performs digital conversion of the discriminated RF signal, and outputs converted data. The level determination unit performs level comparison of current input-data, supplied from the frequency discrimination unit in the latest clock period, with last input-data, supplied from the frequency discrimination unit in the immediately preceding clock period, determines a logic state of the current input-data based on the result of the level comparison, and reproduces data in accordance with the determined logic state.

Abstract: Demodulation apparatus includes a transversal filter characterized by coefficients adjusted by a coefficient determiner responsive to a constant modulus error signal and variable mode error signal related to the output of a spectral mean frequency detector having its input coupled to the output of the transversal filter.

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: An angle demodulator in which an FM modulated wave is converted into an IF signal (SI) in the form of digital so as the signal is supplied to a Hilbert transformer (81) and to an outer product calculation section (82). The Hilbert transformer (81) allows the phase of the IF signal (SI) to shift ninety degrees and supplied it to the outer product calculation section (82). An integrator (84) calculates a phase of a cosine wave of an angular frequency that a frequency control unit (83) designates. A phase converter (85) calculates the cosine wave and an instantaneous value of a signal in which the cosine wave shifts ninety degrees out of phase so as to supply the value to the outer product calculation section (82). The outer product calculation section (82) supplies to the frequency control unit (83) an outer product of a vector including a value of the IF signal and of a signal from the Hilbert transformer (81) and a vector including a value supplied from the phase converter (85).

Abstract: A FM demodulator using a single input signal has two I-Q splitters with constant group delay apparatuses. During operation, t two I-Q splitters with constant group delay apparatuses may receive the input modulated signal to generate not only one pair of modulated and respectively delay &tgr;1 and &tgr;2 in phase signals but also another pair of modulated and respective delay &tgr;1 and &tgr;2 quadrature signals. These signals are used to demodulate the final demodulated signal.

Abstract: A receiver of a frequency-modulated signal representing a digital signal includes a down conversion unit or frequency translation unit to lower the frequency of the frequency-modulated signal and a digital demodulator to regenerate the digital signal from the lowered-frequency signal. The receiver furthermore includes a counter circuit to determine the number of periods of a reference signal from the frequency translation unit during a period of the lowered-frequency signal. The digital demodulator includes a computer unit to compute the period of the lowered-frequency signal from the number of periods of the reference signal.

Abstract: The invention relates to a demodulator and a demodulation method for a TFM-modulated signal comprising symbols, the method comprising the steps of calculating an estimate for the symbols, determining an estimate for the phase shift, determining a modulation index estimate error using the phase shift and the symbol estimates and removing the estimated error from the modulation index estimate using the symbol estimates.

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 FM demodulator using a single input signal has two I-Q splitters with constant group delay apparatuses. During operation, t two I-Q splitters with constant group delay apparatuses may receive the input modulated signal to generate not only one pair of modulated and respectively delay &tgr;1 and &tgr;2 in phase signals but also another pair of modulated and respective delay &tgr;1 and &tgr;2 quadrature signals. These signals are used to demodulate the final demodulated signal.

Abstract: A simplified method for sampling timing adjustment and frequency offset estimation in a TDMA cellular PCS environment using &pgr;/4 - shifted DQPSK comprises the steps of oversampling a received signal resulting from transmission of sequences of complex-valued symbols at a rate N times the symbol rate thereof so as to produce N sets of samples, comparing for each set of samples the differential phase angle between successively received complex-valued symbols, and determining which set of the N sets of samples has differential phase angles closest to ideal values to thereby obtain an optimal sampling timing. The differential phase angles are measured by multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to produce a comparison vector having an angle equal to the differential phase angle between the received complex-valued symbol and the succeeding symbol. The differential phase angles are optionally rotated so that the angle thereof is between 0° and 90°.

Abstract: An FM demodulator compensates for DC offset by detecting the positive peak value of the frequency demodulated signal (D1, C2, R1) and the negative peak value of the frequency demodulated signal (D2, C3, R2). The mean of the positive and negative peak values is determined (C1, R3 , R4) to produce an estimation of a DC offset value. This estimated DC offset value is then used to compensate for DC offset in the frequency demodulated signal. This circuit has the advantage of enabling the DC offset to be calculated without requiring complex digital signalling processing, and without requiring the input signal to have a zero mean. A signal strength signal RSSI may be used to disconnect the DC offset compensation circuitry during periods when the input signal strength is weak.

Abstract: In a circuit arrangement for demodulating signals, particularly frequency-modulated signals, in which a limiter, to whose input the signals to be modulated can be applied, is followed by a demodulator from whose output the demodulated signals can be derived, the outputs of the demodulator and the limiter are connected to a respective input of a mixer whose output is connected to the input of the limiter via a low-pass filter.

Abstract: Embodiments of the present invention relate generally to receivers. One embodiment relates to a digital FM receiver having multiple sensors (e.g. antennas). In one embodiment, the digital receiver includes a baseband unit having a channel processing unit. In one embodiment, the channel processing unit is capable of calculating or estimating a phase difference between the incoming signals prior to combining them. One embodiment uses phase estimation method for diversity combining the signals while another embodiment utlizes a hybrid phase lock loop method. Also, some embodiments of the present invention provide for echo-cancelling after diversity combining. An alternate embodiment of the channel processing unit utilizes a space-time unit to diversity combine and provide echo cancelling for the incoming signals.

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: An FM demodulator for reproducing data by performing FM demodulation of a received RF signal in a Bluetooth transmission system is provided. The FM demodulator includes a frequency discrimination unit and a level determination unit. The FM demodulator frequency-discriminates the RF signal, performs digital conversion of the discriminated RF signal, and outputs converted data. The level determination unit performs level comparison of current input-data, supplied from the frequency discrimination unit in the latest clock period, with last input-data, supplied from the frequency discrimination unit in the immediately preceding clock period, determines a logic state of the current input-data based on the result of the level comparison, and reproduces data in accordance with the determined logic state.

Abstract: A demodulator characteristic curve is oriented centrosymmetrically with respect to the intermediate frequency using a polyphase filter. In this way, the signals can be demodulated with minimal cost and with an optimal result.

Abstract: A demodulator of the present invention is structured so as to include a reference signal generator for generating a reference signal, an FM demodulation circuit for demodulating a modulated signal, and a control circuit for controlling demodulation sensitivity of the FM demodulation circuit. The control circuit controls the demodulation sensitivity of the FM demodulation circuit so that an output signal obtained when the reference signal from the reference signal generator is inputted to the FM demodulation circuit becomes a specified value. This structure can stabilize the demodulation sensitivity of the demodulation circuit with restraining increases in circuit scale and current consumption, and adjust dispersions in the demodulation sensitivities of the respective ICs due to relative errors of a resistance value of a resistor and a capacity value of a condenser in an IC, the resistor and the condenser constituting the demodulator.

Abstract: A method and an apparatus for synchronous demodulation of the multiply modulated rotation rate signal of a rotation rate sensor which comprises a spring-mass system that oscillates at its natural resonant frequency, and at least one capacitor for ascertaining a Coriolis effect acting on the spring-mass system or a rotation rate, the rotation rate being ascertained by a time-variable capacitance change, brought about by the rotation rate, of the at least one capacitor by multiple demodulation of a multiply modulated electrical signal that comprises a time-variable first electrical signal and a second electrical signal, overlaid thereon, at the natural resonant frequency of the rotation rate sensor, the amplitude of the second electrical signal of the time-variable capacitance change of the at least one capacitor being correspondingly modulated.

Abstract: A frequency demodulation apparatus and a method therefor using an arcsin approximation includes: an analog-to-digital converter (ADC) for sampling a frequency-modulated analog signal to convert the frequency-modulated analog signal into a digital signal, and for outputting the sampled values (S0˜Sn) of the digital signal; a first multiplier for multiplying sinusoidal first and second oscillation signals having a phase difference of 90°, by the sampled value Si(O≦i≦n) respectively, and outputting the products as the signals Ii and Qi; a low pass filter for low-pass-filtering the signals Ii and Qi and outputting the low-pass-filtered signals Ii′ and Qi′; a first de-emphasizer for de-emphasizing the high-frequency components of the signals Ii′ and Qi′ and outputting the de-emphasized signals Ii″ and Qi″; a frequency differentiator for delaying the signals Ii″ and Qi″, multiplying and then subtracting the delayed signals, and outputting the subtracti

Abstract: Improved devices, systems, and methods use a Non-Liner Optic (NLO) to effect a conversion of an input laser energy to an output energy. The output energy will have a wavelength which is different than the input energy, and the conversion will vary in response to both an angle of the energy relative to the NLO and a temperature of the NLO. Passive control over the angle of the NLO based on thermal expansion of a member thermally coupled to the NLO can compensate for the temperature-induced change in the conversion so as to maintain a desired output frequency, conversion efficiency, phase matching, and/or the like.

Abstract: A symbol detector for frequency modulated (FM) symbols includes a section determiner, a direction of movement determiner and a data symbol determiner. The section determiner receives a sample of in-phase and quadrature signals associated with a baseband transmitted FM symbol and determines the section value of a unit circle in an in-phase—quadrature coordinate system in which the sample lies. The direction of movement determiner receives the section value of a current sample and the section value of a neighboring sample and generates a positive direction of movement value if the direction of movement along the unit circle from the neighboring sample to the current sample is counterclockwise, a negative direction of movement value if the direction of movement is clockwise and 0 otherwise. The data symbol determiner receives the direction of movement values and decodes the transmitted FM symbol by masking N direction of movement values.

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 digital signal processing architecture for an audio system combines multiple functions in programmable and reconfigurable blocks to achieve an efficient use of hardware and chip area. AM, FM, and audio functions can be performed using the same reconfigurable hardware while taking into account the different sample rates and processing functions required for each.

Abstract: An apparatus comprising an unnecessary frequency component removal unit for removing unnecessary frequency components from a signal supplied from a detector, a unit for obtaining a measured value of delay spread of the signal supplied from the unnecessary frequency component removal unit, an adaptive equalizer for performing adaptive equalization on the signal supplied from the unnecessary frequency component removal unit, and a decoding unit for decoding an input signal, wherein the signal from the unnecessary frequency component removal unit is supplied to the decoding unit through the adaptive equalizer when the measured value of delay spread is larger than a predetermined value, whereas the signal from the unnecessary frequency component removal unit is supplied to the decoding unit without being passed through the adaptive equalizer when the measured value of delay spread is not larger than the predetermined value.

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: Methods and apparatus for dynamically calibrating a modulator in a radio transmitter are provided. In a preferred embodiment an In-Phase and Quadrature (I/Q) modulator in a radio modem is calibrated by means of a modulator, a digital signal processor and a power sensor. The modulator being electrically adapted to receive a local oscillator input having a carrier frequency and a substantially direct current (DC) input having an amplitude in order to produce an output having a power magnitude at the carrier frequency in a frequency defined power spectrum. The power sensor being in electrically succession to the modulator to measure the power magnitude of the output to permit the digital signal processor (DSP), electrically between the modulator and the power sensor, to compare the measured power magnitude with a minimum threshold power magnitude to determine which is greater.

Abstract: A multi-frequency quadrature modulated signal is divided into a plurality of frequency bands. Each frequency band component is estimated as to variation in phase due to multi-path phasing, using its guard interval waveform so as to compensate the variation.

Abstract: Apparatus and method for estimating the angle-modulation imposed on a transmitted Radio Frequency (RF) or Intermediate Frequency (IF) carrier. The method estimates angle-modulation when communications channels add distortions such as noise to transmitted signals. The system provides reconstituted frequency modulation from a feedforward demodulator. The goal is to reduce the modulation index of a desired signal and to employ a narrower band-pass filter that passes this signal while rejecting the distortion that accompanies it. A plurality of stages, 1 through M, exist within the system. Stages 2 through M contain the same components, although filter coefficients and alignment delays may differ from stage to stage. Stage 1 of the demodulator differs slightly from the remaining stages, since the only input required by Stage 1 is a complex envelope signal that contains both the desired signal and the distortion added by the channel.

Abstract: A symbol detector for frequency modulated (FM) symbols includes a section determiner, a direction of movement determiner and a data symbol determiner. The section determiner receives a sample of in-phase and quadrature signals associated with a baseband transmitted FM symbol and determines the section value of a unit circle in an in-phase--quadrature coordinate system in which the sample lies. The direction of movement determiner receives the section value of a current sample and the section value of a neighboring sample and generates a positive direction of movement value if the direction of movement along the unit circle from the neighboring sample to the current sample is counterclockwise, a negative direction of movement value if the direction of movement is clockwise and 0 otherwise. The data symbol determiner receives the direction of movement values and decodes the transmitted FM symbol by masking N direction of movement values.