Abstract: In a direction conversion receiver, a quadrature demodulator produces differential signals in a baseband on the basis of a local signal of a frequency synthesizer, with the differential signals being inputted through a first low pass filter, a gain control amplifier and an amplifier to a control unit and a direct current component between the differential signals being extracted in a second low pass filter. In addition, an offset compensating section reduces an offset voltage while the control unit outputs a control signal for the control of the gain control amplifier. The second low pass filter includes a time constant circuit for determining a time constant through the use of resistors and a capacitor, and a time constant changing section. A time constant control unit controls the time constant changing section for a predetermined period of time after the control unit outputs data for the change of a frequency of the local signal so that the time constant of the time constant circuit decreases.

Abstract: A wireless remote unit is operable to demodulate signals received over a plurality of different bands, such as the FM broadcast band, and one or more higher frequency bands. The various bands have different channels and the selection of the band and the channel is accomplished by control signals received by the receiver. The control signal can carry menu information in one direction to the user and can carry user data, including the identity of the user, in the other direction. There can be multiple transmitters, wherein each transmitter sends information on a different channel within a band, and tunes remote units to a particular transmitter based upon proximity to that transmitter. The transmitter is capable of displaying visual data. The visual data includes a predetermined number of advertisements to be displayed during a user session, prompted either by a user logging onto the system, or by the system's detection of a user's presence.

Abstract: A switching amplifier generates noise at its switching frequency and harmonics thereof. The noise at these harmonics, for an audio amplifier, will be generated with significant amplitude in the AM band. Thus, an AM tuner will experience interference problems if the tuner frequency is sufficiently close to one of these harmonics. To avoid this problem the switching frequency of the switching amplifier is chosen based on the tuner frequency. Thus, the switching frequency is chosen to avoid having harmonics at or too near the chosen tuner frequency. The switching amplifier is disabled when the tuner is in seek or scan mode. Instead of using the tuner frequency to determine what switching frequency should be used to avoid interference, the interference can be detected directly to cause a change in the switching frequency and thus remove the interference.

Abstract: The present invention relates to a process and a system for reducing leakage of LO to the RF-port (LLO) in a real system that converts the frequency of a first signal, i.e. the LO signal, by mixing the first signal with a second supplied signal SI to a third signal SO of a frequency that is different from the frequency of the first and second signal. More specifically the invention relates to a process and a system that are applied to suppress LLO in real image reject balanced passive mode transistor mixers. Further, the invention also relates to a balanced passive mode transistor mixer and an image reject balanced mixer to be used in said process and system.

Abstract: The noise in a frequency demodulated audio signal is detected on the basis of the characteristics of the stereo-multiplex signal to obtain a very reliable information that can be used for the sliding stereo-mono transition, noise blanking and a de-noising of the stereo difference signal. A noise (vd,q(t)) is calculated by performing a coherent amplitude demodulation of the frequency demodulated stereo-multiplex signal with the second harmonic of the pilot carrier that is quadrature to the pilot carrier and as a direct measure for the quality of the signal generating the variance (&sgr;2vd,q) of the noise signal by squaring and thereafter averaging the noise signal.

Abstract: A system for reducing internal interference in a radio-frequency (RF) receiver includes providing a plurality of time slots within a frame where the receiver is configured to receive external RF signals during a receive time slot within the frame. Data is collected during a receive time slot of a frame, and a receive data value is calculated corresponding to the collected data. A predetermined portion of the data collected is inspected, and a bias data value is calculated. The bias value is attributable to interference signals caused by the internal interference. The bias data value is added to an accumulator, and over time, a running average of the bias data values is determined. A portion of the running average is subtracted from the sample stream of data to provide output data corresponding to the external RF signals absent the internal interference.

Abstract: A processing unit with balanced outputs transfers a received digital signal to an amplification unit with balanced inputs and outputs. A control unit enables or disables the processing and amplification units in response to a power up/power down signal. To prevent disturbances due to power up/power down transients from appearing in a speaker connected between the outputs of the amplification unit, switches are provided between the outputs of the processing unit and the inputs of the amplification unit. A delay circuit generates according to a predetermined timing program enabling/disabling control signals for the processing and amplification units, and generates control signals for the switches.

Abstract: Apparatus 20,30,40,50 for receiving and processing a wanted Radio Frequency signal comprises a radio frequency to intermediate frequency down-conversion stage 20 for receiving the wanted radio frequency signal and out-putting a complex intermediate frequency signal; an analogue to digital converter 30 for converting the complex intermediate frequency signal to a digital complex intermediate signal; an intermediate frequency to base-band down-conversion stage 40 for receiving the digital complex intermediate frequency signal and out-putting a digital complex base-band signal; and a complex notch filter 50 for receiving the digital complex base-band signal and out-putting a notch filtered digital complex base-band signal wherein the complex notch filter 50 substantially filters out a small portion of the base-band signal centred about a first, non-zero, frequency while substantially passing a corresponding portion of the base-band signal centred about a second frequency having the same magnitude but opposite si

Abstract: A frequency converter includes: a first terminal through which a local oscillator signal is input; a second terminal through which an input signal with a frequency to be converted is input; a third terminal through which an output signal with a different frequency resulting from the conversion is output; and a field effect transistor with gate, source and drain terminals for converting the frequency of the input signal and outputting the signal with the different frequency as the output signal. The gate terminal is connected to the first terminal, while the drain terminal is connected to the second and third terminals. The frequency converter further includes a trap circuit, which resonates at a frequency of a harmonic of the local oscillator signal to substantially eliminate the harmonic.

Abstract: Whenever the oscillator frequency is a fraction or a multiple of the received frequency, another received frequency could in turn be there, which would then work as a kind of received disturbance frequency, and thus oscillator pulling occurs, which then severely impairs evaluation of the received signal. The method according to the invention for driving a receiver stage having a selection means, having a control unit and an oscillator is distinguished by the fact that the selection means is driven such that whenever the oscillator frequency is a fraction or a multiple of a received disturbance frequency, this received disturbance frequency is attenuated by the selection means.

Abstract: The DC offset compensator compensates DC offsets resulting from interferor self mixing and interferor interaction with even-order nonlinearities. In one embodiment, the DC offset compensator resides in a mobile communication device. A radio frequency (RF) communication signal is mixed with a local oscillator signal (LO) in a direct conversion mixer. The communication signal, at certain times, will have both a communication signal of interest and interferor signals. The interferor signals induce signals in other portions of the mixer circuit, called interferor leakage signals, and the interaction between the two signals causes undesirable DC offsets in the mixer output. The DC offset compensator detects the presence of the interferor signals and provides a compensating signal to the output of the mixer such that the undesirable DC offset signals caused by the interferer self mixing and interferor interaction with even order-nonlinearities in the mixer are compensated out of the mixer output signal.

Abstract: The present invention discloses a method and apparatus for correcting the DC offset caused by self-conversion of the oscillator signal in an RF-to-baseband converter. The circuit comprises: a subtractor for subtracting an amplified DC offset signal from a filtered mixer signal to generate a corrected signal; a baseband amplifier coupled to the subtractor to receive the corrected signal to generate a baseband output signal; a low-pass filter coupled to the baseband amplifier to generate a DC offset signal representative of the DC offset; and a DC offset amplifier coupled to the low-pass filter and the subtractor to generate the amplified DC offset signal.

Abstract: Whenever the oscillator frequency is a fraction or a multiple of the received frequency, another received frequency could in turn be there, which would then work as a kind of received disturbance frequency, and thus oscillator pulling occurs, which then severely impairs evaluation of the received signal. The method according to the invention for driving a receiver stage having a selection means, having a control unit and an oscillator is distinguished by the fact that the selection means is driven such that whenever the oscillator frequency is a fraction or a multiple of a received disturbance frequency, this received disturbance frequency is attenuated by the selection means.

Abstract: A direct conversion receiver comprising a preprocessor coupled to a frequency translator which, in one implementation, is a modified Gilbert mixer. In one embodiment, the preprocessor imparts desired characteristics to split-phase signals received from a local oscillator, including transition points which are determined by crossings through a DC offset, substantial symmetry about a DC offset, and steep transitions about the transition points. In one embodiment, the period of the signals from the local oscillator is divided into portions, and only one of the output signals from the preprocessor is asserted in a predefined state at a time, the predefined state determined effective to reverse polarity of the mixer, signals and a related frequency translator which is responsive to the signals. The frequency translator has a first input at a first input frequency, and at least one second input at a second frequency.

Abstract: In a portable radio terminal having a liquid crystal display, when a radio data receiving period overlaps the timing of outputting a liquid crystal alternating signal to the liquid crystal display, the outputting of the liquid crystal alternating signal is deferred until the radio data receiving period ends, whereby the angle of the liquid crystal is not inverted until the radio data receiving period ends. Therefore, during the radio data receiving period, there does not occur a noise caused because of the inversion of the angle of the liquid crystal, with the result that the receiving sensitivity is not deteriorated.

Abstract: A radio system has a transmitting circuit for tuning in a transmitting frequency at a desired frequency, a control circuit for performing control of the whole of the radio system, a clock oscillation circuit operative to generate a reference clock for the control circuit, a memory circuit operative to store conditions for switching the oscillation frequency of the reference clock to be generated by the clock oscillation circuit, a comparative arithmetic circuit for comparing a transmitting frequency tuned in by the transmitting circuit with the conditions stored in the memory circuit, and a frequency switching circuit for switching the oscillation frequency of the reference clock to be generated by the clock oscillation circuit, on the basis of a result of comparison by the comparative arithmetic circuit.

Abstract: There is described a system and a process for reducing leakage of LO (LLO) in a system which converts the frequency of a first signal by mixing the first signal with a second supplied signal to a third signal having a frequency which is different from the frequency for the first and second signal, where the first signal is divided via a number of couplers into four part-signals which are phase-shifted relative to each other, and that each such part-signal is led through its respective transistor there being added via each transistor a second signal which is mixed with the first signal, and that the signals which pass through the transistors are modulated by a number of regulating means for each transistor, preferably one or two per transistor, and that the frequency-shifted part-signals are added to a third signal via a number of couplings after having been phase-shifted, the voltage regulators being adjustable so that the signals are modulated and LLO is reduced.

Abstract: A wireless remote unit is operable to demodulate signals received over a plurality of different bands, such as the FM broadcast band, and one or more higher frequency bands. The various bands have different channels and the selection of the band and the channel is accomplished by control signals received by the receiver. The control signal can carry menu information in one direction to the user and can carry user data, including the identity of the user, in the other direction. There can be multiple transmitters, wherein each transmitter sends information on a different channel within a band, and tunes remote units to a particular transmitter based upon proximity to that transmitter. The transmitter is capable of displaying visual data. The visual data includes a predetermined number of advertisements to be displayed during a user session, prompted either by a user logging onto the system, or by the system's detection of a user's presence.

Abstract: A disturbance may be prevented from being caused in a satellite broadcasting signal of a reception target by a satellite broadcasting signal in which a frequency is higher by 1 octave.

Abstract: A direct conversion circuit for radio frequency signals is disclosed. The circuit includes a pair of quadrature related mixers, a phase shift unit, and a local oscillator. The pair of quadrature related mixers is coupled to a radio frequency signal input port for mixing down a radio frequency input signal. The phase shift unit is in communication with at least one of the pair of mixers for phase shifting a local oscillator signal. The local oscillator produces the local oscillator signal. The local oscillator includes a non-integer frequency multiplier for multiplying the frequency of a first voltage controlled oscillator signal by a non-integer value to produce the local oscillator signal.

Abstract: A method and apparatus for improving the sensitivity of a radio frequency (RF) receiver at certain frequencies suffering from co-channel interference. In the preferred embodiment, when a reference frequency, FREF, generates significant harmonics for a received RF signal in a selected channel, the reference frequency is varied or offset by a small amount, &Dgr;F. The harmonics of the offset reference frequency, F′REF=FREF±&Dgr;F, are thereby shifted away from the frequency of the received RF signal, thus reducing co-channel interference. The offset amount &Dgr;F is chosen such that the same injection frequency synthesized from FREF can still be synthesized from FREF±&Dgr;F by shifting N by an integer amount, preferably to N+1 or N−1. However, the invention encompasses shifting N by other integer amounts.

Abstract: In accordance with the present invention, a communications system transmits a predetermined signal, from a first, sending, end of a communications system to a second, receiving, end of a communications system. The predetermined signal is distorted by the communication system and is received as a distorted signal that is compared to a known version of the originally transmitted signal. A comparison signal related to the difference between the originally transmitted signal (as represented by the known version of the originally transmitted signal) and the distorted predetermined signal as received at the receiving end is employed to adjust the transfer characteristic of a programmable converter to compensate for the distortion introduced by the communication system.

Abstract: An electronic device has reduced radio frequency interference (RFI) emissions. The electronic device includes a signal generator that is coupled to a reference clock signal and a first digital circuit. The signal generator generates a random signal derived from the reference clock signal. The first digital circuit is coupled to the signal generator. The random signal governs pulse characteristics of the first digital circuit.

Abstract: A CATV transceiver is provided within an RF shield enclosure. The transceiver circuit includes a diplexer, having fixed value inductors, that is coupleable to a CATV cable plant to receive an RF input signal and to transmit an RF output signal. The RF receiver is coupled to the diplexer and includes a frequency up-converter, a first frequency down-converter and a second frequency down-converter. The up and first down-converters include voltage controlled oscillators that are responsive to a control signal generated from a single oscillator crystal. The second frequency down-converter operates to provide an output signal representative of the RF input signal within a predetermined output frequency pass-band. The RF transmitter is also coupled to the diplexer and provides for the transmission of the RF output signal in response to an input signal.

Abstract: A problem in hearing aids or other audio/acoustic amplifier circuits is that external sources of EM energy may be coupled into the electronics of the hearing aid so as to contribute to the acoustic output. The invention provides a circuit for removing the effects of EM interference. A separate reference generator is used to detect the external EM energy. This is fed into an interference canceller which may be adaptive, which effectively removes the unwanted component in the hearing aid signal, leaving only a signal representative of the desired acoustic output.

Abstract: A method and device for controlling a display to suppress noise generated from displaying elements of the display in a radio communication system. In one aspect, a display control device for suppressing noise in a radio communication system comprises: a display having N displaying elements, the N displaying elements being paired, each of the pairs having a first displaying element and a second displaying element; and a controller, operatively connected to the display, for outputting a first control voltage having a first phase to control each of the first displaying elements of the pairs, and for outputting a second control voltage having a second phase to control each of the second displaying elements of the pairs, the first phase and the second phase having a phase relationship which provides for a reduction of resultant noise generated by the N displaying elements.

Abstract: An I/Q direct conversion receiver has an input (5,6) for receiving an RF signal comprising a wanted signal having in-phase and quadrature phase channels modulated onto in-phase and quadrature carrier signals. A signal splitter (7) divides the receiver RF signal into three in-phase signal components. Three substantially identical mixers (8) are provided and receive respective RF signal components for mixing with local oscillator signals. The first mixer (8a) receives the local oscillator signal shifted by 45.degree., the second mixer (8b) receives the local oscillator signal shifted by -45.degree., whilst the third mixer (8c) receives the local oscillator signal shifted by 180.degree.. A correction signal is generated by summing at a summing amplifier (11) the first and second baseband signals together with the third baseband signal after appropriate scaling.

Abstract: The invention provides a superheterodyne receiver by which undesired radiations are minimized. The superheterodyne receiver includes a voltage-controlled oscillator for forming an oscillation signal of a frequency equal to n times a carrier frequency of an object FM signal, and a frequency divider for dividing the frequency of the oscillation signal to the carrier frequency. The superheterodyne receiver further includes a pair of first mixers for frequency converting the object received signal into a pair of first intermediate-frequency signals using signals from the frequency divider as a first local oscillation signal, and a pair of second mixers for converting the first intermediate-frequency signals into a second intermediate-frequency signal with the second local oscillation signals. The superheterodyne receiver further includes a demodulator for demodulating the second intermediate-frequency signal into an original signal.

Abstract: A quadrature down converter comprises two channels, each of said channels comprising two parallel signal paths. Each of said signal path comprises a mixer mixing the signal for down conversion with an oscillator signal. In the in-phase channel the mixers receive the oscillator signal shifted 0.degree. and 180.degree. in phase, respectively. In the quadrature-phase channel the mixers receive the oscillator signal shifted 90.degree. and 270.degree. in phase, respectively. By filtering and combining (adding/subtracting) the signals from the signal paths in each of said channels, the disturbing second order terms from the mixers may be substantially eliminated.

Abstract: A method of detecting the degradation of a transceiver performance due to intermodulation products in radio base stations is disclosed. In an embodiment of the invention, the method includes measuring the received signal strength for each individual receiver frequency and recording the operational state of all transmitters. A plurality of data samples are used to determine a correlation between the received frequencies and associated disturbance. The degradation of signal reception caused by intermodulation (IM) products is derived from the correlated samples. If the performance is found to be below a predetermined value, a notification is initiated upon which corrective action can be taken. The method provides for prompt indication of poorly performing transceivers due to interference from IM products.

Abstract: A synthesizer (100) is used for generating a plurality of synthesized clock signals (128, 156). The synthesizer includes a clock source (102) for generating a common frequency reference signal (103), and a clock generator (104) coupled to the common frequency reference signal for generating a plurality of generated clock signals (106, 108), wherein each of the plurality of generated clock signals is offset from each other by a predetermined phase offset (189, 192). In addition, the synthesizer includes a plurality of PLLs (Phase Locked Loops) (166-168) for generating a selected one of the plurality of synthesized clock signals, wherein each of the plurality of PLLs is coupled to, and operates from, a corresponding one of the plurality of generated clock signals, and wherein the predetermined phase offset between each of the plurality of generated clock signals is known to suppress noise between the plurality of PLLs operating therefrom.

Abstract: Disclosed is a portable terminal device that, by changing the operation of a portable terminal unit based on a selective-calling reception operation, can acquire preferable pager reception sensitivity. A portable terminal device comprises: selective-calling reception means with a selective-calling reception function for determining whether an operation is a selective-calling reception operation; portable terminal mean with a portable radio telephone function to enable transmission and reception for determining whether a key has been input; and display means for, when the input of the key is detected during the operation of the portable radio telephone function, displaying the result of the detection.

Abstract: A DBS tuner for satellite broadcasting receivers, includes an attenuating filter (trap circuitry) composed of a microstrip line having an open-ended load terminal which projects from the RF signal line or the power supply line.

Abstract: In a card-type electronic tuner, a digital broadcasting is received without need of hardware reconstruction of a personal computer used for the digital broadcasting reception. The electronic tuner includes a signal input terminal, a local oscillator, a mixer, an output terminal, a PLL circuit and a data input terminal. All of these components are packaged in a card-type case. A digital signal processor includes a digital signal extractor and/or an A/D converter and is connected between the mixer and the output terminal. The digital broadcasting is received and the data is applied directly to the personal computer. The electronic tuner in the shape of a card can be used with an expansion slot for a memory card of the personal computer and there is no need of reconstructing a hardware of the personal computer.

Abstract: A signal processing circuit for use in a mobile radio equipment terminal including a receiver is provided with an oscillator for oscillating a clock signal serving as a reference; a harmonic-component reducing circuit for restricting a level of harmonic components of the clock signal; and a CPU core portion for effecting signal processing by using the clock signal as a reference.

Abstract: Known is a zero intermediate frequency receiver or zero-IF receiver in which DC-offset correction is done in the I- and Q-paths, after mixing down of the received RF-signal or of an IF-signal. Such a DC-offset correction is not sufficient for high gain I- and Q-paths, particularly not in pagers for receiving long messages. Furthermore, no optimal power saving is achieved if such a receiver alternately operates in receive mode and sleep mode. A zero intermediate frequency receiver is proposed in which DC-offset correction is distributed over the high gain I- and Q-path. Preferably, blocking means are provided between DC-offset correction circuits and low pass filters in the I- and Q-path to prevent that an output signal of an upstream DC-offset correction circuit in the path excites a downstream low pass filter in the path during DC-offset correction. Herewith, considerable power savings are achieved.

Abstract: A direct conversion receiver (200) is capable of recovering a filtered baseband signal (295) from a radio signal (201) modulated with a baseband signal (202). The direct conversion receiver (200) comprises a radio frequency mixer (205) for converting the radio signal (201) to the baseband signal (202), a lowpass amplifier (210) DC coupled to the radio frequency mixer (205), that amplifies the baseband signal (202) and substantially attenuates components of the baseband signal above a high corner frequency, and a DC offset compensation section (225) DC coupled to the lowpass amplifier (210), that provides a DC offset compensation and a controlled highpass filtering of the baseband signal. A low corner frequency of the DC offset compensation section is smoothly varied from a predetermined maximum value to a predetermined minimum value during a low frequency, low energy portion of the signaling protocol.

Abstract: A radio receiver with isolation between an antenna and a regenerative oscillator/detector. The isolation is provided by periodically (at the receiver's quench frequency) uncoupling the antenna from the regenerative oscillator/detector. The receiver preferably includes an antenna, a super-regenerative oscillator/detector, a clock that indicates the quench frequency, a timing circuit coupled to the clock, and a switch coupled to the antenna, to the oscillator/detector, and to the timing circuit. The timing circuit specifies a first part and a second part of each clock period. During the first part of each clock period, the switch at least partially couples the antenna to the oscillator/detector on the nominal reception frequency. During the second part of each clock period, the switch at least partially uncouples these two elements on the nominal reception frequency.

Abstract: The invention relates to an oscillator OSC intended to provide an output signal having a frequency which is variable as a function of a tuning voltage Vtun. The oscillator OSC includes a passive part having two series-arranged variable capacitances Cs, biased by the tuning voltage Vtun, and connected to a power supply VCC via two inductances Lext, and an active part having a first transistor T1 and a second transistor T2 whose collectors are connected to the output terminals C1 and C2 of the passive part, the base of one transistor being connected to the collector of the other transistor via a coupling capacitor Cfb. According to the invention, the passive part includes two high-pass filters, each being inserted between one of the output terminals S1 or S2 and one of the variable capacitances Cs, which allows a reduction of the active part's sensitivity to low-frequency noise.

Abstract: In a portable telephone, a voice filter is connected to an antenna through a receiving circuit. A filter is connected to the voice filter through a switching circuit and filters the voice signal from the voice filter to produce a filtered voice signal. The filter has a first cut-off frequency when the filter is supplied with a first clock signal. The filter has a second cut-off frequency smaller than the first cut-off frequency when the filter is supplied with a second clock signal. A telephone receiver is connected to the filter through an amplifier. A clock generating circuit is connected to the filter and generates the first clock signal when is supplied with a first frequency control signal. The clock generating circuit generates the second clock signal when is supplied with a second frequency control signal.

Abstract: A method for removing the background noise during reception of weak electric field intensity signals. If the electric field intensity of television broadcast signals received by a main picture receiving section is weak, a PIP (picture in picture) function is released, and the release is displayed to notify it to the user. The electric field intensity of the received television broadcast signals is determined in accordance with the AGC signals of the television broadcast signals which are received by a main picture receiving section. If the electric field intensity is strong, the amplification gain of an LNA is adjusted to a low level, and a PIP function is executed or released, depending upon the user's selection of the PIP function. If the electric field intensity is weak, the amplification gain of an LNA is adjusted to a high level, and a determination is made as to whether the PIP function is being executed.

Abstract: A digital receiver includes a mixer stage receiving a carrier signal S(t) and delivering an intermediate frequency signal S.sub.FI (t) to a demodulation stage. The mixer stage is furnished with a PLL circuit for generating a signal at a given frequency. The digital receiver further includes a phase noise digital correction stage for tapping off a noise signal .phi..sub.n (t) generated by the PLL circuit in the mixer stage and for compensating the noise signal .phi..sub.n (t) in the demodulation stage.

Abstract: A quadrature downconversion stage in a radio frequency receiver compensates for leakage from the quadrature local oscillator to the input of the stage by deriving first and second feedback signals from the quadrature local oscillator. The first feedback signal is 180.degree. out of phase with the in-phase component of the signal supplied to the input of the stage and the second feedback signal is 180.degree. out of phase with the quadrature component of the signal supplied to the input of the stage. The invention reduces or cancels a d.c. offset that can appear at the output of the stage. Another advantage is the reduction of re-radiated signals resulting from the local oscillator leakage. The invention is particularly applicable to direct converters.

Abstract: An amplifier circuit has an amplifying transistor which is switched on and off by a switching transistor under control of a control signal selectively applied to the switching transistor. In this way a selection is made whether or not to amplify an input signal on an antenna. The switching transistor forms part of the biasing circuit for the amplifying transistor such that when the switching transistor is on the amplifying transistor is biased off. A PIN diode and series resistor are together connected in shunt across the switching transistor such that the bias voltage which causes the amplifying transistor to be off causes the PIN diode to be forward biased thereby causing the antenna to be terminated with the resistor the value of which may be chosen to be 50 ohms.

Abstract: A conductive frame for supporting a display section is higher in cost than a resin frame, and causes electric contact with other parts and a deterioration in sensitivity due to noise radiations to the antenna. When a radio selective calling receiver is in a normal standby state, since a display driving section (50) is in an inoperative state, a display detecting section (60) detects the non-execution of a display operation and sends a non-display operation signal to an intermediate-frequency section (20). In the intermediate-frequency section (20), a switch section (22) selects a filter (23) in accordance with this non-display operation signal and connects it between a radio section (10) and a demodulating section (21). When the user performs an operation of displaying time display information, calendar display information, or stereotyped expression display information on a display section (40) ion this normal standby state, the display driving section (50) is set in an operative state.

Abstract: A process for allowing two or more receivers to share the same nominal frequency or close nominal frequencies, preferably without these receivers blinding one another or disturbing one another is described. The process preferably includes subjecting a radiator to temporally spaced phases of operation or maximum radiation and temporally segregating the phase sensitivity of the oscillator/detector of the receivers with respect to the phase operation or the radiation of the receiver. The receiver during the phase of sensitivity of its oscillator/detector may not detect the electromagnetic radiation from the radiator.

Abstract: A radio frequency data link that establishes communications between a controller and a remote controllable system is disclosed. The controller includes an interface device that produces command signals indicative of desired system functions. A transmitting RF modem receives the command signals and responsively generates radio frequency signals that are representative of the command signals. A remote controllable system includes a receiving RF modem that receives the radio frequency signals and responsively converts the signals into control signals. A logic device receives the control signals, performs the desired function, and produces a reply signal that indicates the status of the function.

Abstract: The invention pertains to a homodyne receiver and a process for direct conversion of angle-modulated carrier signals, especially those that have a d.c.-voltage component in the converted signal (IF). With many types of-modulation the (short-time) d.c. component of the conversion signal contains information about the modulating signal. Additional d.c. offsets are usually separated out by using a bandpass for the IF signal. In the process, however, the information-containing d.c. components of the converted signal are lost; as a result the demodulated signal is disturbed and in particular the distortion factor is raised. To avoid this the invention provides that the local oscillator for generating inphase and quadrature signals has a frequency offset from the carrier frequency of the receiver signal so that the frequency differential between carrier and frequency and oscillator frequency is in the transmission band of the bandpass used to suppress undesirable mixes, carrier reminders and d.c. offsets.

Abstract: An automatic frequency control is implemented in a selective call receiver (100) having a controllable frequency synthesizer (203). The output frequency of the synthesizer an is derived from a frequency reference element (205). A temperature sensor (206) with substantial thermal coupling to the frequency reference element (205) produces a temperature signal representative of an operating temperature associated with the frequency reference element. The temperature signal is coupled to a controller (105) that operates to execute a microcode program implementing the automatic frequency control. Responsive to the temperature signal and at least one set of parameters representing a predetermined temperature versus frequency characteristic of the frequency reference element, a correction factor is generated and programmed in the frequency synthesizer (203).

Abstract: A radio transceiver having digitally-corrected temperature-compensated crystal oscillators (DTCXOs) including digital frequency temperature compensation circuits that are temporarily suspended from being updated, such that temperature compensation updates that can generate noise during periods of reception and transmission that could interfere with the audio channel and/or signal synchronization will be postponed. Temperature is converted to a digital signal that is then used to address a PROM. The PROM outputs a correction word appropriate for the temperature reading and inputs this to a latch. A timing control loads the latch after data has settled. The latched correction word is connected to a bank of switches and capacitors that trim the frequency of the crystal oscillator. During radio transmission and/or reception, the latch will be suspended from loading any new correction words. The last valid correction word, however, will remain.