Showing papers on "Demodulation published in 1984"

System for carrying out spread spectrum communication through an electric power line

Abstract: A communication system for carrying out communication between a plurality of stations through an electric power line operating in a commercial power frequency band. Spread spectrum modulation of an information signal, employing a pseudorandom code sequence is used at a transmitting station. Spread spectrum demodulation is carried out in a receiving station to reproduce the information signal. The modulated signal is spread over a wide frequency band different from the commercial frequency band. Each station may comprise both of a transmitter and a receiver, and may be specified by a an assigned destination address that also is transmitted. The destination station address may be indicated either by an address signal or by an additional pseudorandom code sequence peculiar to a destination station. Alternatively, polling operation is carried out through the electric power line by a polling station to select one of the stations. Preferably, another pseudorandom code sequence is superposed on the modulated signal so as to specify a synchronization signal and different from the pseudorandom code sequences conveying the information signal and/or the destination address.

Receiver apparatus for three-phase power line carrier communications

Abstract: A transceiver is provided with both voltage and current coupling to a three phase transmission line system. Each phase conductor is coupled to a common point which is connected in signal communication with an input to a receiver. Another input of the receiver is coupled to the neutral conductor of the power line system by an H-field coupler. A signal coupling unit is associated with the voltage couplers between the common connection point and the first receiver input. The receiver is provided with the capability of comparing the voltage signal with the current signal and selecting the stronger of the two. Therefore, the transceiver of the present invention is less adversely affected by standing wave problems since the voltage and current signals are out of phase and voltage nodes are associated with current antinodes and vice versa. Therefore, regardless of the location along the standing wave that the transceiver is located, the best signal available will be used for demodulation purposes.

Digital demodulator arrangement for quadrature signals

Abstract: A direct conversion receiver in which the quadrature I and Q signals are converted into pulse density modulated digital data streams by delta-sigma modulators 14, 15. The resultant digital data streams are then processed in a logic block 18 according to predetermined logic truth tables. The digital output of the processor 18 is then converted back to an analogue signal.

Spread spectrum coding method and apparatus

Abstract: In a process for coding of radio transmissions by spectrum spreading, a signal is phase modulated by means of a 0-pi modulator controlled by a psuedo random sequence formed by combining in accordance with a logical majority function an odd number of elementary codes constituted by pseudo random binary sequences of different lengths. On reception, the synchronization of the code which controls the demodulator is realized by correlating each of the elementary codes with the received signal.

Carrier current transceiver

Abstract: A carrier current telephone system is provided for buildings. Transceivers are located where desired. The transmitter portion includes means for establishing a carrier signal and applying the same to the AC circuits in the building. Further means are provided for generating a subcarrier signal which is encoded on the carrier signal by frequency modulation of the carrier. Further means are provided for encoding the audio or data signal upon the subcarrier signal by frequency modulation of the subcarrier. Exclusive-OR gates are used in a voltage controlled oscillator for the subcarrier signal generator. Unique phase lock loop FM demodulators are used. Each comprises one CMOS 4070B exclusive-OR gate package, five resistors, one potentiometer, and three capacitors, with one of the exclusive-OR gates performing the phase detector function.

Carrier-phase adjustment using absolute phase detector.

Abstract: Modulation-demodulation system and method for transmitting a plurality of sequentially received information bit sequences, the system including a transmitter (10) having a state machine (16) for expanding by a coding process each information bit sequence into an expanded bit sequence with a coded bit group portion and, in some cases, an uncoded bit group portion. The transmitter (2) further includes a modulator (18) for modulating a carrier signal by one of a plurality of multilevel symbols in a two-dimensional complex plane in response to each sequentially applied expanded bit sequence, with the coded bit group portion being used to specify a subset of the multilevel symbols which when rotated in the complex plane maps upon another subset for each adverse angular rotation and the uncoded bit group portion being used to specify for a selected multiple symbol subset the transmitted multilevel symbol of the carrier signal. The system further includes a receiver (50) having a demodulator (58) and slicer (60) for demodulating and detecting the modulated carrier signal to obtain the expanded bit sequences. The object of the invention is to provide in the system a phase rotation detector (68), coupled to the slicer (60), for uniquely identifying each adverse angular rotation by analyzing a plurality of sequentially applied coded bit group portions; and a phase corrector (95), coupled to the phase rotation detector (68), for compensating for the adverse angular rotation.

FM Signal demodulator

Abstract: An FM demodulator wherein the input signal excursions advance a counter. At each of a sequence of equal sample times, the count is compared to a value which is the average of the highest and lowest counts during the sequence. The comparison may be numerically direct or by down-counting from a present number. The result of the comparison sets an output data value either "1" or "0".

Circuit for establishing accurate sample timing

Abstract: In order to establish accurate sample timing in a digital demodulator which forms part of an orthogonally multiplexed parallel data transmission system, two second-order PLLs are arranged after a demodulating section of the digital demodulator so as to receive baseband signals of corresponding pilot channels. The two second-order PLLs each includes an integrator. These integrators apply the outputs thereof to a subtracter which applies the subtraction result to a voltage-controlled oscillator in order to establish the accurate sample timing.

Cross-Coupled Phase-Locked Loop with Closed Loop Amplitude Control

Abstract: In this work a new version of the cross-coupled phaselocked loop (CCPLL) interference canceller is presented. This detector consists of two phase-locked loop (PLL) demodulators interconnected in such a manner as to permit one PLL to lock onto and track the instantaneous frequency of the stronger received signal, while the other loop tracks and demodulates the weaker of two received signals. In addition, the receiver includes control loops to estimate the instantaneous amplitude of both received signals. This demodulator, therefore, has the capability of detecting both the desired and interfering signals, even though the interferer may be stronger than the desired signal and may share the same frequency band. The defining nonlinear differential equations for the CCPLL structure are derived and transient acquisition responses are obtained using computer-aided analysis. The CCPLL has numerous technological applications in suppressing a wide variety of cochannel and adjacent channel interferers.

Multilevel decision method for band-limited digital FM with limiter-discriminator detection

Abstract: A new decision method for band-limited digital FM that employs discriminator detection is presented. This new method adopts a multilevel decision scheme to soften the intersymbol interference effects caused by severe band limitation. It is shown that applying this method significantly improves bit error rate (BER) performance of digital FM using discriminator detection. Theoretical BER evaluation proves the superiority of this method, and establishes the optimum values for fundamental transmitter parameters. Experimental results are provided to support the superiority of this method.

Digital Portable Transceiver Using GMSK Modem and ADM Codec

Abstract: Digital mobile radio transmission techniques and integrated circuit devices have been developed for application to a digital portable transceiver utilizing narrow-band GMSK modulation and ADM voice coding Design and performance of a quadrature type GMSK modulator and a single-chip coherent demodulator as the GMSK modem are described To overcome slow fading, encountered in portable applications, switching diversity using a jitter detection type sensor is Proposed and shown to be effective An experimental Portable transceiver, developed to demonstrate hardware feasibility, is also described

Open fault location system for photovoltaic module strings

Abstract: A radio frequency (rf) probing technique is disclosed for determining whether an rf signal injected into one termination of a series-connected string of photovoltaic (PV) modules has been conducted to successive positions in the string. A signal generator is provided for generating a carrier signal which is modulated by an audio frequency tone. The generator is capacitively coupled to one of the terminations of the module string to inject the modulated carrier signal into the string. A receiver is tuned to the carrier frequency and adapted to demodulate the audio tone. Rf signals are coupled to the receiver by a probe including a shielded plate electrode, which may be disposed adjacent the active surfaces of successive ones of the modules in order to detect the presence or absence of the rf signal at that point in the string. An alternate technique is disclosed, whereby a measurement of the capacitance-to-ground of the string is compared against a reference capacitance value of a fault-free system.

Demodulator logic for frequency shift keyed signals

Abstract: A demodulator logic for FSK signals on an RF carrier in a direct conversion radio receiver, wherein the received signals are mixed with a local oscillator to provide quadrature baseband signals, characterized in that the demodulator logic comprises two clocked D-type flip-flops, FF1,FF2 one baseband signal being applied direct to the clock input CK of one flip-flop and inverted to the clock input CK of the other flip-flop, the second baseband signal being applied to the D inputs of both flip-flops, one input Q from one flip-flop being algebraically combined with one output Q from the other flip-flop to provide a demodulator signal output of the receiver, the two flip-flop outputs being chosen so that for a given FSK value they always have the same logic value.

A muiti-mode modulation and demodulation system and method

Abstract: An improved system and method for modulation, demodulation and signal processing for single sideband communications systems which provides correction for the adverse effects of rapid fading characteristics in a mobile environment. The system provides modulation through a modified Weaver modulator in which the audio input is processed to produce an output in the form of an upper sideband having a pilot tone in a spectral gap at approximately midband. The receiver includes a modified Weaver demodulator and a correction signal generating circuit which processes the received faded audio input and pilot tone to produce a correcting signal. The correcting signal is mixed with the received signal to regenerate unfaded versions of both the signal and pilot by removing random amplitude and phase modulations imposed on them by the fading.

Electronic musical instrument using amplitude modulation with feedback loop

Abstract: In a musical tone synthesizer in which an amplitude-modulated carrier wave delivered from an amplitude modulator is used to form a musical tone signal, the amplitude-modulated carrier wave is fed back to the input side of the amplitude modulator as a modulation signal, a portion thereof, a portion of a carrier wave or a composite signal of the modulation signal and the carrier wave. The amount of feedback may be controlled by multiplying the amplitude-modulated carrier wave with a predetermined modulation index. Furthermore, the modulation index may be charged with time so that the control of spectrum construction of the musical tone signal is readily performed. According to a modified embodiment, a plurality of amplitude-modulators are provided which are connected in a ring form feedback loop in which the modulated outputs of preceding amplitude modulators are supplied respectively to succeeding amplitude modulators.

Control program signal demodulating device

Abstract: A control program signal demodulating device comprises a control program demodulator for obtaining a demodulated output of a control program signal from a signal which is reproduced from a rotary recording medium which is recorded with at least the control program signal together with a video signal, where the control program signal indicates a control program including input and output commands and internal processing commands of an external device such as a computer which has a discriminating function and is coupled to a player which plays the rotary recording medium, a memory circuit for at least temporarily storing the demodulated output of the control program demodulator and producing the stored demodulated output, a selecting circuit for selectively producing data received from the memory circuit in response to a transmission request, an interface circuit for transmitting the data which is produced from the selecting circuit to the external device, and for receiving one or a plurality of control commands from the external device, and a command analyser for decoding one or a plurality of control commands received from the interface circuit, and for generating a signal which controls the operation of the player or a signal which requests transmission with respect to the memory circuit and the selecting circuit.

Frequency Hopping with Multiple Frequency-Shift Keying and Hard Decisions

Abstract: The performance of frequency-hopping systems with multiple frequency-shift keying and hard decisions is determined for operation against optimal partial-band jamming. A receiver that eliminates the potential advantage of optimally placed jamming tones is proposed. The effects of Reed-Solomon, binary block, and convolutional codes are analyzed. Concatenated codes with hard and soft decisions available to the outer decoder are examined. Continuous-phase frequency-shift keying with limiter-discriminator demodulation is shown to offer potentially improved performance in frequency-hopping systems.

Electric wiring system having a plurality of sensors

Abstract: An electric wiring system has a plurality of terminal units, a plurality of sensors connected to the terminal units by signal input lines, and a central control unit connected to the terminal units by a pair of common power supply lines, which receive signals from the sensors. The central control unit has a reference signal generator circuit which repetitively generates a reference signal composed of a train of pulses, a predetermined number of which are assigned to each of the sensors, a modulator circuit for applying the reference signal to the power supply lines, a demodulator circuit for picking up a composite signal generated by the terminal unit from the power supply line, and a control circuit for detecting abnormal and normal signals of the sensors and breakage of the power supply lines and signal input lines based on the presence and absence of high-frequency pulses in the composite signal, thus indicating sensor and line conditions. Each of the terminal units has a demodulator circuit for picking up the reference signal from the power supply lines, a composite signal generator circuit for generating the composite signal by adding the high-frequency pulses at pulse positions corresponding to the pulses of the reference signal assigned to the sensors, dependent on the abnormal and normal signals of the sensors and breakage of the signal input lines, and a modulator circuit for applying the composite signal to the power supply lines.

Baseband-controlled passband equalizing arrangement

Abstract: PHF. 83.532 24 ABSTRACT: A baseband-controlled passband equalizing arrange-ment for correcting carrier-modulated data signals comprises a passband correction circuit having variable elements, demodulation and carrier recovery circuits for converting the corrected modulated signals into baseband data signals, and a control circuit responsive to an estimated error in the base-band signals for controlling the variable elements of the correction circuit. In known arrangements of this type, the modulated signals are sampled before they are applied to in-phase and quadrature equalizer circuits. An improvement avoiding any problems associated with sampling and providing in-phase and quadrature equalizer circuits is achieved by providing for a passband correction circuit, which comprises fixed delays and variable parameter elements of multipliers and phase shifters and which produces a time-continuous passband output signal in response to a time-continuous passband input signal. The values of the variable parameters are not affected by the state of the carrier recovery circuit.

Subcode signal reading circuit in an optical type disc player

Abstract: A subcode signal reading circuit in a compact disc player of the compact disc digital audio system comprises an EFM demodulation circuit which receives an EFM reproduction signal reproduced from a disc, EFM-demodulates the EFM reproduction signal and outputs a demodulated eight-bit signal, a first register in which a Q subcode included in the demodulated eight-bit signal provided by the EFM demodulation circuit is written in eight-bit fashion, a second register to which contents of the first register are transmitted and an error detection circuit for detecting whether or not the Q subcode produced by the EFM demodulation circuit contains error. Transmission of the contents of the first register to the second register is controlled by an output of the error detection circuit in such a manner that the transmission is made when no error has been detected by the error detection circuit. An output of the second register is used in the disc player as a correct Q subcode to be read.

A phase shift keying and phase modulation transmission system

Abstract: A PSK and phase modulation transmission system has a modulator and a demodulator. The modulator has a carrier frequency generator (21) coupled to a voltage controlled phase shifter (22). The modulation of the signal in the shifter (22) is controlled by modulation voltage generator (23). A transmitter (24) receives the output from the shifter (22) and transmits the modulated signal. The demodulator (30) includes a receiver section (31) for receiving the signal transmitted by the transmitter (24). The receiver (31) is coupled to a modified phase locked loop comprising a phase detector (32), a low pass filter (33), a sample and a hold circuit (34) and a voltage controlled oscillator (35). A lock control circuit (36) receives either the output from the receiver (31) or the output from the filter (33) to produce a lock in pulse from changes in the received signal or changes in the demodulated signal at the filter (33) for controlling the sample and hold circuit (34).

Multiplying circuit comprising switched-capacitor circuits

Abstract: Multiplying circuit for multiplying a first signal x(t) by a periodic second signal y(t) and being particularly suitable for use as an amplitude demodulator in a stereo decoder or in a phase-locked loop. It comprises N signal channels 26(.), each receiving the first signal x(t) and each producing a channel signal. Each signal channel is formed by, arranged in cascade, a switched-capacitor circuit 28(,;1. 28(.;2), 29(.), the circuit included in the signal channel having numberk being controlled by a train of control pulses g(k,i) which each have a finite duration and occur with a repetition period To and at instants to+k(To/N)+iTo wherei = ...-2,-1,0,1,2,3,...,means29(.),31, 30 for multiplying the amplitude of the signal x(t) by a constant weighting factor W(k) which is equal to y(tok[To/N]), pulsereshaping means 29(.), 30, 31 for converting a pulse applied thereto into a pulse having a predetermine duration. The channel signals thus obtained are added together in an adder device 30, 31 to form a sum signal. This sum signal is sampled in a sampling arrangement34(1), 34(2), 35 at instants comprised within the interval between the end of a control pulse g(k,i) and the beginning ofthe subsequent control pulse g(k+1,i).

Transmission system for TV signals on radio links

Abstract: A system for transmitting television signals on a radio link. The system includes a transmitter having a modulator for modulating a carrier signal to produce a vestigial sideband amplitude modulated signal for transmission. The modulator includes a first converter for converting the frequency of video signals to an intermediate frequency and a second converter for converting the intermediate frequency of the video signals to a radio frequency. The system further includes a receiver having a demodulator for demodulating a received vestigial sideband amplitude modulated signal. The modulator includes a Nyquist filter connected between the first and second converters, and the demodulator includes a filter having a rectangular characteristic for processing the signal to be demodulated.

Digital data transmission system by coherent light wave modulation

Abstract: A digital data transmission system by modulating a coherent light wave is provided using modulation of the MSFK type with N frequencies for modulating the light wave. The transmitter comprises a coherent light source, a modulator, an output optical means and an MSFK modulation signal generator. The receiver comprises an input optical means, local light wave source and a heterodyne mixer for creating an electric signal of intermediate frequency. A demodulation and detection circuit comprises filtering means for separately selecting the N frequencies before detection. A processing cirucit puts the data back into its initial form. A circuit for compensating for the drift of the light sources is used for preserving lock on to the intermediate frequency.

Block demodulation for short radio packet

Abstract: The demodulation of phase-modulated signals is performed primarily by synchronous detection which has excellent characteristics. Thus, to regenerate a reference carrier wave that is identical with the transmitted one, a pure carrier should be received for a fixed time as a preamble before the data. Therefore, in digital radio terminals which are expected to appear, if a single extremely short information data burst has to be transmitted, it would possibly require the addition of a long preamble. If the relative carrier frequency offset is large in a low-speed transmission system, then a longer preamble is necessary. This paper proposes a demodulation system for phase-modulated signals which allows a shorter preamble or eliminates the need for it completely. The proposed system is based on the recent rapid progress in the speed, capability, and price of the microprocessors which obviates immediate demodulation, but makes it practical to store a data sequence of a fixed length without any demodulation. In addition, it is possible to realize the demodulation with batch processing by a block demodulation system. In such a system the complete transmitted burst signal containing no preamble can be demodulated with the optimum carrier phase. If this system is used merely as a frequency offset detector, it can complete the detection more than 5 times faster than a phase-locked system under the same noise conditions.

Demodulator for constant envelope and continuous phase signals which are angle modulated by a train of binary symbols

Abstract: The demodulator is for use with an angle modulated signal conveying a sequence of binary symbols. The signal is modulated at constant envelope and with continuous phase and may be treated as a sequence of elementary pulses that have been amplitude modulated using a principal function Fp (t) derived from the frequency pulse characteristic of the modulation. The demodulator comprises two filters matched to the principle function and connected to receive quadrature components constituting the complex envelope of the received signal. The filters are followed by samplers. A calculating circuit operating at the bit rate calculates metric increments on the basis of P stored complex samples and transmits the increments to a decision circuit which performs a dynamic programming algorithm to determine the values of the bits in the sequence recursively.

Switched-capacitor FSK modulator and demodulator in CMOS technology

Abstract: A switched-capacitor FSK modulator/demodulator built in silicon-gate CMOS technology is described. The modulator is based on a programmable harmonic oscillator using two stray-insensitive integrators. The centerpiece of the FSK demodulator is a switched-capacitor voltage-controlled oscillator. A simple post-detection processor restores the digital data. Both circuits have been designed for the 600-baud modem channel with 1500 Hz center frequency and /spl plusmn/200 Hz frequency shifts, but the demodulator operates in the 1200-baud channel as well. Due to dynamic biasing the operational amplifiers feature high slew rate, high voltage gain, and low power for capacitive loads.

Synchronization detection system for data transmission

Abstract: A synchronization detecting system for data transmission in which a two-dimensionally modulated signal is received by way of a demodulator. In a training sequence for a two-dimensional modulation modem, a point of transition from an alternation to a pseudorandom symbol sequence is detected by producing a sum of the vectors of two signals which are remote from each other by a period of two samples, or a difference therebetween. Whether the detection of the transition point has been correct is decided utilizing the alternation.

Demodulator with AGC circuit for multi-level quadrature amplitude-modulated carrier wave

Abstract: A demodulator for a multi-level quadrature amplitude-modulated carrier wave includes an AGC amplifier receiving the multi-level quadrature amplitude-modulated wave, the amplifier output being coupled to a quadrature phase demodulator producing an inphase and quadrature-phase demodulated signal. An automatic gain control amplifier receives an output of the quadrature-phase demodulator to compensate for the gain difference between the inphase and quadrature-phase signals. The gain difference compensated inphase and quadrature-phase signals are applied to first and second multi-level discriminators.

Power line communication receiver with dual threshold signal interrogation capability

Abstract: A dual threshold is used in a coherent phase shift keyed demodulator to distinguish situations in which an incoming carrier signal is expected from those open ended conditions when a receiver is active, but when an incoming signal is not imminently expected. The use of a lower threshold permits more rapid detection and demodulation of a valid carrier signal by utilizing a standard which is less strict to determine the presence of a valid carrier signal when an incoming carrier signal is expected.