Abstract: In a cable network for delivering a personal communications service (PCS) and cable television (CATV) service, return service applications, e.g., a pay per view service, are also provided on a return cable band provided by the cable network. In accordance with the invention, the return service applications utilize subbands unused by the PCS in the return cable band, thereby unaffecting the PCS. The broadband noise in the subbands normally accompanied by the PCS is filtered out using a tunable filter whose passband is adjustable to coincide with one of many PCS signal bands being used in the return cable band.

Abstract: A transceiver for a code division multiple access communication system comprises a receiver to receive coded information signals and a transmitter to transmit coded information signals. A local oscillator provides a time and frequency reference for the receiver and the transmitter. A timing controller provides timing signals for the receiver and the transmitter. A signal processor decodes received signals to determine a common error associated with the timing controller. A timing correction circuit smoothly adjusts the timing of the coded information signals transmitted by the transmitter responsive to the timing error to reduce the timing error over a desired time interval.

Abstract: A method and apparatus for providing time-critical band selection in a communication device with dual band or multi-band switching, or, alternatively, for providing dual mode or multi-mode time critical operating ability. The mobile station typically has a transmitter section and a receiver section each capable of dual modes of operation, a frequency synthesizer and a controller. The band to band operating method utilizes a frequency command data signal where data derived from the signal is used in a determinable bit stream of data including a frequency data word. The frequency data word is used for defining an operational state of the synthesizer frequency thereby implementing the transceiver's operating channel. At least one bit (or functional bits) from within the bit stream or received signal is used for defining, at least momentarily, the transceiver's “new” operating band (or state).

Abstract: An approach is provided for transmitting messages using low density parity check (LDPC) codes. Input messages are encoded according to a structured parity check matrix that imposes restrictions on a sub-matrix of the parity check matrix to generate LDPC codes. The LDPC codes are transmitted over a radio communication system (e.g., satellite network), wherein a receiver communicating over the radio communication system is configured to iteratively decode the received LDPC codes according to a signal constellation associated with the LDPC codes. The receiver is configured to iteratively regenerating signal constellation bit metrics after one or more decoding iterations.

Abstract: An automobile remote control circuitry. There are wireless transmission circuitry and wireless receiving circuitry each on the remote control itself and the circuitry inside the automobile. The special feature: the wireless transmission circuitry and wireless receiving circuitry apply the same specification of LO base band frequency circuitry. Based on above structure, it can reduce the number of components used in the bi-direction remote control, lower the total component cost and easier in manufacture processes.

Abstract: A radio signal transmitted from a transmitter to a receiver of a mobile communications system, such as the GSM system, often suffers from a phenomenon known as frequency offset by which the frequency of the radio signal is changed from a first frequency to a second frequency. A method is therefore provided for automatically correcting the frequency at the receiver to restore the received radio signal to approximately the first frequency using a multistage frequency correction algorithm. The radio signal comprises a training sequence that is known to the receiver and data symbols that are not known to the receiver. In the first stage of the frequency correction, the frequency offset is coarsely estimated based on the training sequence only, and the data symbols are frequency corrected by back-rotating the received data symbols and the training sequence by the frequency offset estimate.

Abstract: Circuits and methods for modulators that receive symbols, and provide I (incident, or in-phase) and Q (quadrature) component values from a look-up table for subsequent filtering and digital-to-analog conversion. The I and Q component values depend on frequency correction and time index signals such that operating frequency differences between a handset and base station are compensated for, and the transmitted symbols are continuously phase shifted by 3&pgr;/8 radians.

Abstract: A radio frequency transmission control apparatus for preventing an oscillation in a wideband wireless local loop terminal has a radio frequency transmitting unit for modulating a baseband transmitting signal to a WLL radio frequency band signal and transmitting the modulated signal via an antenna, and the radio frequency transmitting unit is divided into a radio frequency converting unit and a power amplifier unit in accordance with characteristics of each active element constituting the radio frequency transmitting unit. When a power is supplied to the radio frequency transmitting unit, the power is first supplied to the radio frequency converting unit so as to maintain the same at an operating state. After a predetermined time period has elapsed, the power is supplied to the power amplifier unit.

Abstract: A closed loop automatic gain compensation method and circuit for a radio transmission and reception system formed of a radio frequency transmitter coupled through a high power amplifier to a radio frequency antenna to transmit a radio frequency transmission signal, the automatic gain compensation circuit utilizing the preexisting radio system cabling.

Abstract: Methods and apparatus for bandpass filtering a radio frequency (RF) signal in a cellular transmit path to provide a filtered RF signal to a power amplifier. The methods comprise bandpass filtering the RF signal by tracking, without translating, the carrier frequency of the RF signal with a phase-locked loop prior to power amplifying the signal for transmission. The tracking filter provides symmetrical filtering by centering the pass band of the tracking filter on the RF carrier, irrespective of where the RF carrier is within the pass band of the system.

Abstract: A transmitter with a pulse width modulation amplifier includes an inner positive feedback loop, which has a self oscillating modulator and a switching stage and is connected to an LP filter. Outer feedback loops from the LP filter respective from an output transformer are coupled to a compensation block connected to the inner loop. An input telecommunications signal, fed via the compensation block, is superimposed on a carrier from the modulator into a pulse width modulated signal, which is amplified, filtered and fed to the transformer. The input signal is compared with feedback signals. Phase shift caused by the LP filter is partly compensated by the inner loop. A switching frequency in the modulator therefore can be comparatively low. An output impedance is kept on a predetermined level, enabling connection of a receiver. Advantages are low power dissipation, high packing density, high frequency bands and use in bidirectional communication.

Abstract: A transceiver determines a modulation method to be used in a signal transmission based on an evaluated transmission channel condition and a difference between transmission powers of communicating transceivers. In this way, the transceiver can choose an optimal modulation method even in the communications between transceivers having different transmission powers. The transceiver comprises a transmission channel condition evaluator for evaluating a transmission channel condition based on a signal received from a counterpart transceiver; and a modulation method selector for determining a modulation method to be used in transmitting a signal to the counterpart transceiver based on the evaluated transmission channel condition and a difference between transmission power of the transceiver and that of the counterpart transceiver.

Abstract: A cellular telephone receives a first communication signal from a cell-site station and transmits a second communication signal to the cell-site station. The cellular telephone includes an antenna, a duplexer, a receiver, an encoder/decoder apparatus, an acoustic transducer, a transmitter and a controller. The receiver is connected to the antenna through the duplexer. The receiver converts the first communication signal into a voice signal code, and outputs a signal indicating an intensity of the first communication signal. The transmitter is connected to the encoder/decoder apparatus and to the antenna through the duplexer. The receiver converts the input voice code signal from the encoder/decoder apparatus into the second communication signal. The controller is connected to the receiver and the transmitter. The controller controls amplitude of the transmitter corresponding to said intensity of the first communication signal.

Abstract: A mobile communications device is arranged to receive a modulated signal having a predetermined frequency. A frequency demodulator of the device demodulates the modulated signal, and a frequency correction arrangement calibrates the demodulation frequency of the device to the predetermined frequency by providing a preliminary difference estimation between the predetermined frequency and the demodulation frequency using a broadband portion of the modulated signal, followed by a main difference estimation (between the predetermined frequency and the demodulation frequency) using a dedicated narrowband portion of the modulated signal.

Abstract: The invention discloses an apparatus and method for reducing frequency pulling. Further, the invention provides amplitude modulation techniques to eliminate spurious signals and injection locking of the VCO to the output transmitted carrier. The architecture includes at least one synthesizer, a plurality of frequency dividers, an output VCO, a low pass filter, a mixer, a pretransmission filter and an amplifier connected in a manner to generate an output frequency which is non-harmonically related to the synthesizer VCO and to maintain the magnitude of the output frequency at, preferably, exactly 1.5 times higher than the VCO frequency.

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: A reference frequency generating section 10 capable of suitably changing frequency accuracy of an output signal in accordance with an input control voltage, and a high-accurate reference frequency generating section 13 having accuracy for a temperature change extremely higher than that of the reference frequency generating section 10 and in which output frequency accuracy thereof changes only within a range of prescribed values (frequency accuracy within a range where transmission and reception of a portable telephone can be conducted) are provided. A reference frequency after an AFC operation, which is output from the reference frequency generating section 10, is compared with an output signal from the high-accurate reference frequency generating section 13, and whether or not frequency accuracy of an output signal from the reference frequency generating section 10 meets a prescribed value is determined.

Abstract: By employing AFC range extension, a high frequency communication device (100) can use a low cost, low accuracy crystal (119) in its reference oscillator (118). AFC range extension involves varying receive bandwidth of the communication device (100) to facilitate AFC or automatic frequency control. In particular, the receive bandwidth is set to a first, wide setting for AFC acquisition purposes (208). Frequency error associated with a received AFC signal is determined (212) and receive reception is adjusted (218) to reduce frequency error in the communication device (100). Once the frequency error is below a predetermined threshold (214), the receive bandwidth is set to a second setting different from the first setting for normal reception (220).

Abstract: A dual band VCO selects between the oscillator output frequencies by switching the resonant circuit elements in the active circuit. For each output frequency selected, the oscillator produces a single frequency signal and additional energy in the form of phase noise. This phase noise may be from sideband noise produced by modulation of the single frequency or produced by the active device in the oscillator as flicker noise, or the noise figure of the active device under large signal conditions or the filtering effect or the resonant circuit. Phase noise is reduced by shifting the bias point for the active device to the level where phase noise is minimum for each output frequency. At the time the output frequency is selectively switched, the bias to the active device is selectively switched to an optimum bias level for minimum phase noise for each respective selected frequency.

Abstract: A system for frequency stabilization and control is provided. The circuit according to the invention consists of three major subsystems; namely, a display and control module, an integrator module, and a voltage controlled oscillator. The electronic system disclosed provides a highly flexible method of frequency stabilization and control. The system is programmable and may be used in a wide variety of applications, offering a variety of advantages over conventional systems such as PLLs.

Abstract: An integrated transceiver circuit (10) includes a single side-band mixer (12) and a phase locked loop (30). The phase locked loop (30) includes a phase detector (32) coupled to a voltage controlled oscillator (36) via a summing circuit (33) and a low pass filter (34). A feedback signal from the voltage controlled oscillator (36) is transferred to the phase detector (32) through a counter (38). Either a phase modulation signal or a frequency modulation signal are inputs of summing circuit (33) and modulate the transmitter carrier signal generated by the voltage controlled oscillator (36). The carrier signal generated at an output terminal (40) of the transmitter tracks the frequency of the local oscillator signal that is supplied at an input terminal of the single side-band mixer (12) in the receiver.

Abstract: A transmitter-receiver includes a transmitting circuit for providing an output by converting the frequency of a transmission signal input thereto, a receiving circuit for providing an output by converting the frequency of a received signal input thereto, and a local oscillator which generates an oscillation signal having a local oscillating frequency based on a reference signal. A local oscillator signal splitter is connected to the local oscillator and splits the oscillation signal into substantially similar transmit and receive oscillation signals each at the local oscillating frequency. The local oscillator signal splitter supplies the transmit oscillation signal to the transmitting circuit and supplies the receive oscillation signal to the receiving circuit. The transmitting circuit converts the frequency of the transmission signal in accordance with said transmit oscillation signal, and the receiving circuit converts the frequency of the received signal in accordance with the receive oscillation signal.

Abstract: A radio receiver, and a method therefore, for efficiently suppressing attenuation properties of a low frequency signal, in an analog frequency modulation type radio communication system. The radio receiver includes a first down-converter for mixing a modulated, high-frequency signal received by the radio receiver and a predetermined local oscillating signal to generate an intermediate frequency signal. A modulator modulates the predetermined local oscillating signal by an aural signal transmitted from the transmitter and generates a mixing signal for down-mixing the electrical signal representative of modulated, high-frequency signal. The mixed signal is then applied to the first down-converter. A second down-converter down-converts, in frequency, the intermediate frequency signal generated from the first down-converter into a baseband signal to generate the down-converted signal.

Abstract: A radio frequency generator in a radio communication system having a transmitter for up-converting the frequency of transmission data signals, and a receiver for down-converting the frequency of reception data signals includes: a first radio frequency generator for generating a low-band reception local oscillator frequency signal which is provided to a second mixer in the receiver; a second radio frequency generator for generating a low-band transmission local oscillator frequency signal which is provided to a first mixer in the transmitter; and a third radio frequency generator for generating a high-band local oscillator frequency signal for a first mixer of the receiver and a second mixer of the transmitter. A reference frequency generator is provided for receiving a radio frequency signal from a global position system receiver and generating a reference signal for generating local oscillator frequency signals in response thereto.

Abstract: A method and apparatus for continuously calibrating the modulation sensitivity of a voltage controlled oscillator (VCO) within a modulator of a transmitter. In accordance with the present invention, the transmitter is coupled to the receiver in order to loop back the transmit signal. The present invention includes a baseband signal generator which generates a reference baseband signal of known amplitude during periods when no other baseband information is being applied to the transmitter by the user. A Signal and Reference Comparison Circuit (SRCC) receives the output from the demodulator and determines whether the VCO within the transmitter has the proper modulation sensitivity. If the modulation sensitivity of the VCO is not within a desired range, then a signal generated by the SRCC is applied to a baseband level control circuit to adjust the level of the baseband signal that is applied to the VCO.

Abstract: A frequency stabilization circuit includes a local oscillator, a mixer, a level comparator, a frequency comparator, and a controller. The local oscillator outputs a local oscillation signal in accordance with a control voltage. The mixer converts a received radio frequency signal into an intermediate frequency signal using the local oscillation signal from the local oscillator. The level comparator compares a DC voltage corresponding to the intermediate frequency signal from the mixer with a reference voltage to determine whether the reception electric field level of the radio frequency signal is high or low. The frequency comparator compares the frequency of the intermediate frequency signal from the mixer with the frequency of the reference signal to output frequency difference information. The frequency comparator outputs previous frequency difference information when the comparison result of the level comparator indicates a decrease in reception electric field level.

Abstract: A digital radio communication system includes a first down converter for converting down a predetermined radio frequency (RF) signal into a first intermediate frequency (IF) signal according to a first local oscillation signal; a second down converter for converting down the first IF signal into a second IF signal according to a second local oscillation signal; a demodulator for demodulating the second IF signal according to a third local oscillation signal and outputting a predetermined base band of a signal; a modulator for modulating the predetermined base band of signal according to the second local oscillation signal and outputting a third IF signal; a up converter for converting the third IF signal to a RF signal according to the first local oscillation signal; a first phase-locked loop (PLL) for controlling the first local oscillation signal in a direction where the sum of the frequency deviation between the first local oscillation signal and a reference frequency signal and the frequency deviation bet

Abstract: In a method of calibration of a voltage controlled oscillator (VCO), the VCO (100) provides an output signal which is used to drive a dividing oscillator (10) such as a relaxation oscillator (RO). The RO has at least two states, one in which the RO provides an output signal which has a first frequency that is related to the VCO output signal by a first ratio (e.g. 1/N) and one in which the relaxation oscillator provides a RO output signal which has a second frequency that is related to the VCO output signal by a second ratio (e.g. 1/(N+1)). By measuring the first and second frequencies (and knowing the relationship between the first and second ratios), the VCO frequency is calculated and stored (110). Several VCO frequencies can be calculated and stored for several applied voltages. As a result the VCO can be driven to any selected frequency in the calibrated range and can be used to provide an injection frequency for a radio.

Abstract: A radio device requires a tunable transceiver such that the transceiver can be accurately set to a desired frequency. When a signal with known frequency accuracy is being received, an offset detector can determine the frequency offset generated by the transceiver due to improper tuning. An automatic frequency control (AFC) system (100) is comprised of a tunable transceiver, an offset detector (103) and an AFC control processor (105) for utilizing information from the offset detector to reduce the inaccuracy in frequency by tuning the transceiver towards the received signal frequency. The AFC control processor (105) utilizes one of more threshold levels for defining a maximum correction threshold (311) based upon the desired maximum offset correction. These thresholds are used by the AFC control processor (105) to efficiently control the predetermined frequency range of the tunable transceiver (101) for most efficient operation.

Abstract: Techniques employed to guarantee isochronous operation of a wireless system to within Federal Communication Commission, Unlicensed Personal Communication System (UPCS) requirements. Synchronization and frequency stability is tracked and maintained for more than one frequency references of stratum 3 or better in a wireless telecommunication system.

Abstract: A frequency correction of a local frequency is performed by first checking whether synchronization is acquired with respect to the received signal and, when the synchronization has been acquired, performing a frequency correction twice at different timing within a synchronization section, the frequency correction correcting the local frequency so as to reduce an error of the local frequency with respect to a received frequency of the received signal.

Abstract: A method for synchronizing transmissions of mobile stations in a mobile radio system including a first and second mobile station and a radio unit all communicating on a direct mode channel. According to the method, the radio unit transmits synchronization information messages on the direct mode channel, which messages indicate the frequency used by the radio unit, and which messages include accuracy information, indicating that the accuracy of the transmit frequency used by the radio unit exceeds the accuracy normally employed on a direct mode channel. The mobile stations receive the synchronization information messages and tune respective receivers and transmitters to the frequencies indicated by the synchronization information message.

Abstract: A system and method for implementing a cellular radio transmitter device comprises a first oscillator device for generating a first oscillator output signal, a second oscillator device for generating a second oscillator output signal, a power amplifier for amplifying the second oscillator output signal to obtain a transmit signal, a mixer device for combining the first oscillator output signal and the transmit signal to produce a mixer output signal, a phase comparator for comparing the mixer output signal and a transmitter input signal and responsively generating a control signal to control the transmit oscillator, and a feedback path for adding the mixer output signal to the transmitter input signal to compensate for distortion present in the transmit signal.

Abstract: A multiple address radio network in which there is a central station and remote radio sites. The central station transmits control and data acquisition signals to the radios at the remote radio sites and the radios at the remote radio sites transmit to the central station acquired data. Each remote radio has an automatic frequency calibration circuit for adjusting its associated remote radio to reduce frequency offset between the radio frequency carrier transmitted by the remote radio and the radio frequency carrier transmitted by the central station by adjusting the temperature compensated crystal oscillator of the automatic frequency calibration circuit. Toward this end, a microprocessor of the frequency calibration circuit detects and measures the offset frequency and controls a digital potentiometer for adjusting the temperature compensated crystal oscillator.

Abstract: When starting a radio transmitter, a transmission frequency is generated by a phase/frequency-locked loop which includes a phase/frequency comparator, a loop filter and a voltage-controlled oscillator. The start-up is performed by switching on an operating voltage to the voltage-controlled oscillator. To minimize the frequency error of the transmitter at start-up, measuring data about relationship between the control voltage of the oscillator and the output frequency of the oscillator at a specified calibration temperature are pre-stored in connection with the oscillator, and immediately before switching on the operating voltage, the control voltage needed for locking onto the selected output frequency at the prevailing temperature is estimated and the estimated control voltage is set as the control voltage of the oscillator.

Abstract: An apparatus for electrical line communications using FM video modulation, includes FM video modulation circuits and an impedance matching coupler at each of two or more locations along a pair of lines. The impedance matching couplers provide impedance matching, utilizing an air-core preselected frequency bands, sufficient to allow low-loss transmission of frequency modulated video signals. The coupler further eliminates noise and is matched resistively to the characteristic impedance of the line at the preselected frequency bands. A transmitter, receiver and associated circuits may also be provided at each location along the lines. The FM video modulation circuits, in combination with phase linear coupling techniques, provide for hi-fidelity video transmission over existing electrical lines, such as residential AC power wiring. In addition, a coupler with solid state impedance matching is provided.

Abstract: A method and apparatus for initializing a radio transmission apparatus comprising a voltage control oscillator, a phase lock loop, and a power amplifier is disclosed so as to avoid generating unwanted interference in neighboring radio channels. First, the voltage control oscillator is enabled and the phase locked loop is switched from a narrow band mode to a wide bandwidth mode to give faster settling time and reduced overshoot. The power amplifier is then smoothly ramped up to a final power level. Finally, the phase locked loop is switched from the wide bandwidth mode to the narrow bandwidth mode after the power amplifier has substantially reached the final power level.

Abstract: A temperature compensation circuit (10) for a crystal oscillator module (12) used in a communication device (200). An existing microcontroller (210) of the communication device (200) is used to provide temperature compensating digital data (30) for a crystal oscillator (18). The temperature compensating digital data (30) is converted to a temperature compensation signal (22) in a digital-to-analog converter (32) which controls the crystal oscillator frequency. The crystal oscillator module (12) includes an onboard voltage regulator (34) which supplies a characterized regulated voltage (36) to the digital-to-analog converter (32) such that the temperature compensation signal (22) from the digital-to-analog converter (32) is inherently corrected for voltage variations in the voltage regulator (34). Changes in the temperature compensation of the crystal oscillator (18) are allowed only when the communication device (200) is not transmitting or receiving.

Abstract: A robust automatic frequency control (AFC) loop for use in radio frequency systems performs a threshold test on the accumulated error adjustments for controlling a frequency oscillator. Based on this test, the loop adjusts the value contained in the error accumulator to allow the receiver to remain locked to a desired frequency carrier even in the presence of a strong adjacent channel interferer. The AFC loop is designed to be used in error systems where the predetermined fixed carrier spacing. Assuming that the initial frequency error is never exceeded by one-half the carrier spacing, the system can determine if the wrong channel has been locked to if the oscillator in the AFC loop is corrected by more than half the carrier spacing. Through use of a threshold test on the accumulative oscillator correction, the AFC loop can determine if the receiver has locked to an adjacent interfering channel.

Abstract: Described is a method, apparatus, and article of manufacture to minimize radio data modem receive errors when a base station keys up. It applies to an intermittently keyed, multiple base station, single frequency reuse, FM modulated, radio data network such as the ARDIS network. Compensation is provided for the fact that each base station in the network may have a different transmit FM deviation level. Since these networks typically use the same base station to transmit to any one radio data modem over periods of time, and since the modem receiver can measure and remember the FM deviation level of each base station, a modem can compensate by using the FM deviation value of its "present" base station as the starting value for its automatic deviation control algorithm. By seeding the algorithm with the actual value for the "present" base station, receive data errors are reduced during the critical time when the base station is keying up.

Abstract: A communication device (100) employs a local oscillator (104) having an improved charge pump circuit (122). The charge pump circuit (122) has current mirrors (204, 208) in which a first transistor (224, 270) is biased to provide a substantially constant current. A resistor (226, 272) selectively conducts a reference current to bias a mirror transistor (228, 274). The current mirror (204, 208) provides improved dynamic performance thereby reducing global phase error of the communication device (100).

Abstract: A zero-intermediate frequency receiver circuit (11) for receiving a radio frequency signal detected by an antenna (14). The receiver circuit (10) comprises a second local oscillator circuit (25) and an oscillator circuit (60) of a phase locked loop demodulator (36) which are identical and track each other so as to provide a more accurate reference for processing a demodulated signal. A current reference (39) providing a current reference signal utilized by the second local oscillator circuit (25) and the oscillator circuit (60) of the phase locked loop demodulator (36).

Abstract: The effects of long-term drift in a local reference oscillator are compensated by dividing the local reference oscillator frequency by one of three divider patterns (nominal ratio, add a cycle, delete a cycle) so that the symbol clock of the remote terminal is equal to the outroute symbol rate. The number of add a cycle and delete a cycle divider patterns are counted and stored. The average of the number of add a cycle and delete a cycle patterns is used to control the transmit frequency of the remote terminal to correspond to the outroute symbol rate. Thus, the clock recovery process generates a frequency calibration number used to track the frequency of the remote terminal local reference oscillator and to adjust the transmit frequency of the remote terminal accordingly.

Abstract: A frequency-controlled circuit for automatically detecting a center frequency of a received signal whose frequency is shifted includes a frequency control unit for receiving the input signal and changing the frequency of the received signal into another frequency, a demodulating unit for demodulating a signal outputted from the frequency control unit, an incoming detecting unit for detecting whether a demodulated signal outputted from the demodulating unit is proper or improper and a level detecting unit for dividing a frequency band of the signal, obtained in the frequency control unit by adding a receive frequency band of the received signal to the center frequency of the received signal or subtracting the center frequency thereof from the receive frequency band thereof, into a plurality of narrower frequency bands and detecting respective power values of the divided frequency bands.

Abstract: A transceiver (10) includes a dual port phase and magnitude balanced synthesizer modulator (60). The modulator (60) couples a modulation input to a voltage controlled oscillator (40) and to a reference oscillator (42) that are coupled together in a phase locked loop (44). The modulator 60 includes a magnitude balancing circuit (64) that divides a modulation input representing data or the like into a first modulation input signal applied to the reference oscillator (42) and a second modulation input signal for the voltage controlled oscillator (40). A phase balancing circuit (68) induces a negative phase shift in the second modulation input signal that is coupled to the voltage controlled oscillator (40) in order to compensate for the phase lag of the reference oscillator loop (44).

Abstract: A method and apparatus in a radio communication transmitter (600) stabilizes a carrier frequency locked to a reference oscillator (102). The reference oscillator (102) is controlled by a control signal and generates a first signal at a reference frequency. The first signal is coupled to a frequency multiplier (212) for multiplying the reference frequency by a predetermined factor to generate a second signal at the carrier frequency. Cycles of the carrier frequency are counted (508, 514) during a predetermined interval to determine (516, 518) a measured cycle count. The measured cycle count is compared (520) with an expected cycle count corresponding to a predetermined carrier frequency to determine a drift error. From the drift error a control signal adjustment required to correct the drift error is computed (522). The control signal of the reference oscillator (102) is adjusted (524) by the control signal adjustment to correct the drift error.

Abstract: A receiver has a channel scan mode of operation and a communication mode of operation. In the channel mode of operation, the passband of a filter is narrowed relative to the passband of the filter in the communication mode. According to another aspect of the circuit, a local oscillator is selectively phase locked to an internal clock during channel scanning and locked to the incoming signal during a communication mode operation.

Abstract: The present invention relates to an automatic frequency control device and an automatic gain control device which have the advantage of improving the efficiency of a system with very low signal-to-noise ratio by compensating for frequency error generated at the local oscillator of a satellite or on the receive paths by demodulating the modulated signal continuously sent out from a transmit earth station for transmitting information without using the separate pilot frequency at a receive terminal of a receive earth station and locking at local oscillator of a frequency downconverter to a voltage controlled oscillator tracking an error after detecting a phase error of a carrier by using demodulated data, by compensating the frequency error due to Doppler frequency deviation by locking a local oscillator of a frequency upconverter to a voltage controlled oscillator tracking a phase change according to Doppler frequency deviation included in the clock after recovering the clock from the demodulated data, and by c

Abstract: The preferred embodiment of the present invention encompasses an automatic frequency control system implemented in a radiotelephone (101). The radiotelephone (101) includes a frequency synthesizer. The frequency synthesizer uses a division ratio varied with time by a multi accumulator fractional N synthesizer (140) such that the effective division ratio may be varied by non-integer steps. The division ratio is programmed to realize the desired channel frequency, the desired modulation waveform, and any automatic frequency correction offset. An accurate clock is provided to the control logic (104) and the user interface (105) sections of the radiotelephone (101) using a second multiple accumulator fractional N division system (139). This second fractional N division system (139) is programmed based on the automatic frequency control programming of the first fractional N synthesizer (140).

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).