Abstract: An integrated circuit chip set is provided for use in a radio communication system in which a modulated digital input signal is processed for transmission and a modulated signal received from an antenna is processed to provide an output signal, wherein the modulation of the signals is either QPSK or FSK and the signal transmission and reception is by either TDD or FDD.

Abstract: A multiple-modulation communication system includes a transmitter that modulates and transmits communication signals modulated by a first modulation technique and communication signals modulated by a second modulation technique. The first modulation technique and the second modulation technique are different. The communication system also includes a receiver capable of receiving the communication signals modulated by the first modulation technique and the communication signals modulated by the second modulation technique and demodulating the communication signals.

Abstract: A circuit for discriminating the modulation type of a received signal capable of discriminating the modulation type at high speed.

Abstract: The present invention provides for an analog and/or digital radio broadcast transmission system and radio receiver therefor, which includes a control signal having an item of control information concerning another, different type of transmission/receive system. The receiver is a hybrid receiver able to receive both types of signals. When the same program material is available on both of the different systems, the control signal is used for switching the different systems so that the receiver receives the program on the system which provides the best reception.

Abstract: A demodulator receives a radio signal and causes a carrier signal reproducing circuit to reproduce the carrier signal of the received signal. One amplifier amplifies the amplitude of the reproduced carrier signal by K, and another amplifies the amplitude of the reproduced carrier signal by (K+2). An adder adds the reproduced carrier signal, amplified by K, and the received signal. A subtracter subtracts the received signal from the reproduced carrier signal amplified by (K+2). The output signal of the adder is demodulated by a first FM demodulator and the output signal of the subtracter is demodulated by a second FM demodulator. Another subtracter outputs the difference between the demodulated signals from the first and second FM demodulators as a demodulated signal of the received signal.

Abstract: A low-pass passive filter is inserted in the phase locked loop of a voltage-controlled oscillating circuit having a varactor diode. The filter has a first resistor, a capacitor and a second resistor connected in that order and the blocking characteristics of the filter are changed in accordance with a selected value of the second resistor. A push-pull output circuit in which the upstream transistor is connected directly to the supply voltage line receives the signal from a phase comparator circuit (which is indicative of the result of phase comparison) and outputs it to the low-pass passive filter. The low-pass passive filter controls the terminal voltage of the varactor diode in accordance with the terminal voltage of the capacitor and the value of the second resistor is selected depending on the desired blocking characteristics of the filter.

Abstract: An apparatus and method for automatically controlling a reference frequency (120) in a receiver (104) that receives either analog (116) or digital (136) information signals. The receiver (18) includes a frequency translator (109) for translating a carrier frequency (137) to an intermediate frequency (118) and maintaining the intermediate frequency (118) at a desired value responsive to the reference frequency (120). A first measure of frequency error (211, 212) is detected between the reference frequency (120) and the intermediate frequency (118). A second measure of frequency error (125, 126) is detected between the reference frequency (120) and the intermediate frequency (118). A current signal (213) is produced responsive to the first measure of frequency error (211, 212) when the receiver receives the analog information signal (116) and responsive to the second measure of frequency error (125, 126) when receiver receives the digital information signal (136).

Abstract: A channel selecting apparatus simultaneously selects both the modulation signals, which are simultaneously received at different channels where modulation signals having a continuous phase and digital modulation signals having a discontinuous phase are located. As both the modulation signals are propagated on the same transmission path or approximately the same inclination of transmission path, modulation signals existing on different channel frequencies suffer approximately similar frequency shift from the transmission path before being inputted to the channel selecting apparatus.

Abstract: A receiver for selectively receiving high frequency signals from analog modulated signals and digital modulated signals. The receiver has an intermediate frequency signal circuit for selecting a desired channel of the high frequency signals and for frequency-converting the high frequency signal of the selected channel into an intermediate frequency signal, a demodulator for demodulating the intermediate frequency signal, which is adapted to be capable of demodulating modulated signals in a variety of modulation systems, the demodulator including at least a digital section, and a controller for controlling the demodulator to be able to discriminate between the analog modulated signals and the digital modulated signals, based on a demodulated signal output from the digital section of the demodulator and to be switched into a demodulation mode suited for modulation system of the selected channel of the high frequency signals.

Abstract: A semiconductor integrated circuit includes a first circuit and a second circuit. The first circuit is set into an operative state in a first mode and into a non-operative state in a second mode, and the transfer characteristic thereof depends on an externally attached impedance circuit. The second circuit is set into an operative state in the second mode and into a non-operative state in the first mode. A resistor is externally connected to the second circuit. A third circuit for keeping a voltage applied across the resistor constant and deriving a current flowing in the resistor in the first mode irrespective of the presence or absence and the magnitude of a voltage applied to one end of the resistor is provided in the first circuit. The resistor is commonly used by the first circuit and the second circuit.

Abstract: A broadcast and reception system provides a segmented broadcast signal for providing regional traffic information and a receiver adapted to receive selected segments of that broadcast. The segmented broadcast signal includes a number of segments which each include a tone sequence, a digital regional code, a digital duration code, and an audio segment. The receiver monitors selected regional traffic segments and converts the selected audio segment to a form compatible with a standard automotive radio. Thus, a user can selectively monitor regional traffic information without having to listen to reports from regions of no interest to him. Alternatively, the selected traffic information can automatically override normal radio listening.

Abstract: An improved AM-FM combined stereo receiver is provided having a single processor for removing, in the FM mode, arctangent distortion, and in the AM mode, to process the phase term from arctangent ##EQU1## to determine ##EQU2## Further, the radio includes a single discriminator circuit wherein, in the FM mode, the discriminator tank circuit is used to convert frequency deviation to baseband audio and, in the AM mode, the discriminator tank circuit is used as the frequency-determining element for the voltage controlled oscillator (VCO), the VCO being used to translate the intermediate frequency (IF) signal to baseband.

Abstract: A frequency control system for a dual-mode radiotelephone (152-238; 252-320) operative to receive either an FM signal or a DQPSK signal. In a first embodiment, when operative to receive the FM signal, the frequency of the reference oscillator (192) of the radiotelephone (152-222) is maintained in a fixed relation with the frequency of the FM signal. When operative to receive the DQPSK signal, the reference oscillator (192) is maintained in a fixed relation with the frequency of the DQPSK signal as determined by a digital signal processor (212). In a second embodiment, when operative to receive the FM signal, the frequency of an offset control oscillator (320) is maintained in a fixed relation with the frequency of the FM signal. When operative to receive the DQPSK signal, the reference oscillator (292) is maintained in a fixed relation with the frequency of the DQPSK signal as determined by a digital signal processor (312).

Abstract: A variable bandpass filter for filtering RF antenna signals to improve selectivity and reduce intermodulation distortion in an FM radio receiver includes a series resonant circuit which is modified to avoid blocking of AM signals. A bypass inductor is connected in parallel with the series resonant capacitor. The bypass inductor has a self-resonant frequency located between the AM and FM bands so that series resonant performance is maintained at FM frequencies and the bypassing function is exhibited at AM frequencies.

Abstract: A digital demodulator for demodulating baseband signals in a radio receiver. The demodulator includes a digital signal processing module for forming a mathematical series adapted for generating demodulation functions. The selection of coefficients for this series is controlled to provide specific demodulation functions as required for the demodulation of different kinds of signals such as amplitude modulated or angle modulated signals using one computational block or element. When demodulating amplitude modulated signals, the coefficients used in the mathematical series provide an approximation to the square root function. When demodulating phase or frequency modulated signals, the coefficients used provide an approximation to the arctangent function.

Abstract: An improved AM-FM combined stereo receiver is provided having a single processor for removing, in the FM mode, arctangent distortion, and in the AM mode, to process the phase term from arctangent ##EQU1## to determine ##EQU2## Further, the radio includes a single discriminator circuit, wherein, in the FM mode, the discriminator tank circuit is used to convert frequency deviation to baseband audio, and in the AM mode, the discriminator tank circuit is used as the frequency-determining element for the voltage controlled oscillator (VCO), the VCO being used to translate the intermediate frequency (IF) signal to baseband.

Abstract: An autocorrelator for FSK signals. An FSK signal, incoming on a telephone line is filtered by a bandpass filter (13) and sampled by an A/D converter (14). A sample clock (15) provides a fixed sampling frequency, FS. A first interpolating filter (20B) provides selectable delays which are non-integer multiples of 1/FS, and an integer delay (25) provides selectable delays which are integer multiples of 1/FS. The delayed signals are multiplied by a multiplier (26) and then filtered by a low pass filter (27) to provide a filtered autocorrelated signal. A second interpolating filter (20A) provides for reduced jitter in the baud timing by increasing the number of samples provided to the decision logic (23). The decision logic (23) provides the decoded data output.

Abstract: A signal receiver which is capable of receiving and demodulating a satellite broadcasting signal which is an FM signal and a terrestrial broadcasting signal which is an AM signal is disclosed. FM and AM signals are frequency-converted into signals having frequencies in a same intermediate frequency band by making common use of a radio frequency amplifier, a mixer, a local oscillator and an intermediate frequency filter. At the time of reception of an FM signal, the FM signal is demodulated in a phase-locked loop circuit, and a local oscillator is subjected to frequency modulation by a part of the demodulated signal, thereby constituting an FM negative feedback loop, and thus narrowing the occupied bandwidth of the FM signal. At the time of reception of an AM signal, the phase-locked loop circuit is used to regenerate a carrier, and the output signal of the phase-locked loop circuit is input to a multiplier to effect synchronous detection of the input signal.

Abstract: Method for receiving carrier oscillations modulated with a useful signal. For a universal transmitting/receiving device, a method for the automatic adaptation of its modem to the type of modulation of the incoming signal is provided in which the incoming DPSK signal is first demodulated. The demodulator output signal is then converted into a polar co-ordinate representation and, after formation of the difference phase angle (.DELTA..phi.), its value frequency (H) is represented modulo 90.degree. in a histogram which can be evaluated for derivation of the control information.

Abstract: A paging receiver is disclosed which is compatible with transmissions from analog or digital paging transmitters. The paging receiver has a command structure which permits it to be dynamically programmable to change its functionality including programming of the channels which the paging receiver is to receive. The programmability of the channels permits the paging receiver to be used for making national, regional, remote area, local area, and sublocal area pages, and pages to a group in the local area and to switch from channels which are heavily used during peak paging times to lesser used channels. The paging receiver transmits the paging receiver identification code digits in an order of increasing significance which significantly lessens power consumption for all paging receivers tuned to a particular frequency for determining if a page is to be received which prolongs paging receiver battery life.

Abstract: Traditionally, the parameters evaluation and characterization of amplitude modulation(AM), frequency modulation(FM) and phase modulation(.phi.M) signals are achieved utilizing analog test and measurement instruments. The advancement of high speed analog to digital converters and digital signal processing techniques have made this digital AM/FM/.phi.M demodulator an accurate, repeatable and cost effective alternative for the test and measurement of various modulation waveforms. This invention illustrates the design of the digital AM/FM/.phi.M demodulator.

Abstract: A dual purpose receiver operable both on FM analog (voice) and MSK digital (data) signals has a demodulation section having a selectable time delay D.sub.1 for processing MSK digital signals and a time delay D.sub.2 for processing FM analog signals. A switch permits selection of the time delay for the demodulating mode desired. A second switch set according to how the first switch is set connects a digital processing circuit or an analog processing circuit to the output of the demodulation section. Small frequency errors due to frequency drift of the local oscillator or signal source and doppler effects can be eliminated by an automatic frequency control (AFC) circuit responsive to the output of the demodulator in the analog mode, and through a third switch responsive to a signal developed by mixing the input signal with the input signal delayed by a time delay D.sub.1, and mixing the output of that mixer with the binary output of the receiver in the MSK mode.

Abstract: A demodulator including a Hilbert transformer (20), a carrier regenerating circuit (30), a first delay line (35), a second delay line (36), a first switching device (38), a second switching device (39), a first multiplier (40), a second multiplier (42), a second adder (44), a third switching device (46), a third multiplier (48), a fourth switching device (50), a fourth multiplier (52), a second adder (54) and a divider circuit (60). This demodulator is able to demodulate either a frequency modulated signal, or a signal with double amplitude modulation in quadrature and with suppressed carrier.

Abstract: A multi-mode radio transceiver comprising a sequence of bi-directional circuit modules including a radio frequency input/output amplifier module (1), a radio frequency/baseband I and Q quadrature channel conversion module (2), an analogue/digital conversion module (3), a digital signal processor (4,5), and a digital signal input/output interface (6), with a control means (7) whereby for transmission a radio frequency signal is formed from analogue quadrature I and Q channel components of a digitized signal at baseband and translated to the radio transmission frequency and for reception the radio frequency signals are transformed into I and Q quadrature analogue components at baseband and subsequently digitized.

Abstract: A synchronizing circuit used for both an AM intermediate frequency signal and an FM composite signal. A phase detector, voltage-controlled oscillator, frequency divider and phase shifter are connected in a phase-locked loop. The division factor of the frequency divider is controlled to different values for the AM and FM signals.

Abstract: A mixer is disclosed for use in a dual conversion AM-FM radio receiver in which AM and FM broadcast RF signals from a first IF amplifier are converted by the mixer from a first intermediate frequency to a second intermediate frequency for amplification in a second IF amplifier. A double balanced mixer circuit receives a signal at the first intermediate frequency and a local oscillator signal to generate signals at the second intermediate frequency on its two complementary outputs. One of the outputs is connected to the second IF stage through a narrow bandpass ceramic filter at the second intermediate frequency and a transistor switch. The other output is connected to the second IF stage through another transistor switch. The transistor switches are responsive to an external signal to alternatively connect the output through the ceramic filter for AM signals and the other output for FM signals.

Abstract: A converter is coupled between the antenna and the RF stage of an FM stereophonic receiver to convert received AM stereo signals into FM stereo signals. A received AM stereo signal is translated to an IF signal, and decoded into two stereo signals. These signals are then encoded into a broadcast-type FM stereophonic signal which is coupled into the front end of an FM stereo receiver.

Abstract: On receipt of an FM sound signal an intermediate frequency signal (at 1) is directly applied to an AM demodulator (80) via an electronic switch (50). The audio signal is then obtained by frequency demodulation (in 10) of an intercarrier signal obtained from the demodulator (80). On receipt of an AM sound signal the intermediate frequency signal is applied to the AM demodulator (80) via a filter (6) and the audio signal is obtained from the output of the AM demodulator (80).

Abstract: Feed-back paths of amplifiers, such as the alternately-operable AM and FM amplifiers of radio receivers, are interconnected by a first capacitor and earthed by a second capcitor, and each of the paths has a switching transistor for permitting current flow through only the feed-back path of the amplifier which is in operation. The AM amplifier has several stages including a final stage with transistors connected via respective feedback paths to two respective input connections. The FM amplifier is identical except that the component values differ.

Abstract: An apparatus and method of transmitting and receiving information underwa assure improved performance characteristics. Modulating a carrier and appropriately filtering it allows the transmission of only single sideband signals or a carrier along with single sideband signals to increase the range at reduced power consumption levels. Demodulating incoming signals can be done synchronously (when the carrier is present) or asynchronously (only single sideband signals) to extract the information. When a number of carriers are modulated and, simultaneously, are transmitted and received, the system's reliability is enhanced.