Abstract: A novel frequency synthesizer incorporating a band switching VCO having a low KVCO tuning factor enabling operation with low supply voltage and low susceptibility to noise and frequency pulling. The VCO has a low tuning factor that covers only a small portion of the operating frequency range, depending on the number of bands into which the frequency range is divided. The normal phase locked loop operation of the synthesizer is preceded by an open loop band selection procedure which results in faster lock time and a lower required tuning voltage range for the VCO. The frequency band selection is made using frequency measurements. Alternatively, a band select LUT and channel LUT are generated a priori during a calibration stage in order to speed frequency acquisition and band selection.

Abstract: A tuning arrangement in a radio receiver includes a front-end circuit having a tunable band-pass filter that is capable of tunably selecting channels within at least one frequency band of an RF signal. A noise source coupled to an input of the tunable band-pass filter introduces a wide-band noise signal into the front-end circuit. A signal detector coupled to an output of the front-end circuit measures at least one signal power associated with a filtered noise signal derived from the wide-band noise signal. A tuning controller, coupled to the tunable band-pass filter by a tuning control signal, adjusts the tuning control signal in response to the at least one measured signal power for tuning the tunable band-pass filter to a desired filter response.

Abstract: A communication device includes a noise flattening filter having a filter response that dynamically adjusts based on the current noise spectrum in a wireless channel. The noise spectrum of the wireless channel is estimated and used to determine a noise classification for the channel. A noise flattening filter response is then selected based upon the noise classification for use in filtering signals received from the channel. The filtered signals are then delivered to an equalizer for further processing.

Abstract: The invention relates to a method for the control of the bandpass width in the filtering of an intermediate frequency signal of an audio receiver of a radio reception apparatus. A signal parameter of a user signal of the audio receiver which is received at a reception frequency is determined and taken into account and a signal parameter of at least one neighboring signal which is received at a neighboring frequency which is adjacent to the reception frequency is determined. The bandpass width of the intermediate frequency filtering is selected in dependence at least on the signal parameter which is determined from the user signal, on the signal parameter which is determined from the neighboring signal and on the frequency distance between the reception frequency and the user frequency. Furthermore, the invention relates to a corresponding radio reception apparatus.

Abstract: A RF transceiver for AMPS communication includes: a baseband processor for generating a transmission intermediate frequency signal and processing a reception intermediate frequency signal; a local oscillator for generating a local oscillation signal in transmission and reception; an up-mixer for combining the transmission intermediate frequency signal with the local frequency signal; a duplexer for processing a radio frequency signal received through an antenna; and a specific frequency removing unit installed between the local oscillator and an up-mixer to remove a specific frequency signal generated from the local oscillator. A filter is installed between the local oscillator and the up-mixer to remove the 2-times frequency of the local oscillation signal of 957.66 MHz, thereby removing the self-quieting phenomenon generated in the channel 76 of AMPS.

Abstract: A receiver (600) uses a scanning technique (100) to minimize scan time. An initial bandwidth setting is selected that covers multiple channel frequencies (106). A signal detection step (108) is performed looking for channel activity. As channel activity is detected, the bandwidth of a baseband filter (628) is narrowed (140, 146). The radio remains programmed to the same channel while the bandwidth is varied. Once the last signal detection with the narrowest possible bandwidth setting has been determined (144, 150, 152) the radio is programmed to that channel. Thus, more than one channel frequency is capable of being scanned without reprogramming the radio to a new channel for each scan.

Abstract: The method, apparatus, and system for controlling audio anomalies by using a mute switch 51 to prevent output of an auxiliary audio signal 21 in a television signal 20 with an auxiliary audio signal 21, such as a NICAM audio signal or dual language audio signal, adjacent to a first audio signal 22. The mute switch 51 operation is a function of the type of receiver 19 receiving television signal 20 and a function of verifying the presence of an auxiliary audio signal 21 in television signal 20. The present invention controls audio anomalies such as audio whistle and audio pop.

Abstract: In a variable rate wireless communication system, an explicit reduced-bit rate indicator is used to communicate the data rate and configuration of the transmission to the receiver. Data throughput is increased by reducing the number if bits required to indicate data rate and channel configuration. Related allocation of total transmit power, and related receive processing are conserved. Reception is enhanced by increased probability of correct decoding. Receiver performance is enhanced by reducing the probability of false erasures and associated outerloop setpoint adjustment errors when the receiver is notified of channels with zero data rates. Power consumption is reduced by using fewer bits to communicate data rate and channel configuration information, and by more accurate setpoint adjustment.

Abstract: A radio receiver has a front-end circuit that generates a radio frequency (RF) signal. The front-end circuit includes a first tunable band-pass filter that is capable of tunably selecting channels within at least one frequency band. To tune the first tunable band-pass filter, the receiver further includes a local oscillator circuit for generating a local oscillating signal, and a second tunable filter coupled to receive a signal derived from the local oscillating signal and to generate therefrom a filtered local oscillating signal. A control unit in the receiver is coupled to receive a signal derived from the filtered local oscillating signal. The control unit generates a control signal based on the signal derived from the filtered local oscillating signal. The control signal is supplied to the first tunable band-pass filter and to the second tunable filter for tuning the first tunable band-pass filter and the second tunable filter.

Abstract: A multiple-hypothesis frequency detection or demodulation system and method in a mobile communication system such as a GSM mobile telephone system includes a GSM mobile unit for demodulating the received signal by applying three hypotheses. The first hypothesis is based on the assumption that transmitted signal was received without frequency offset or phase rotation. The second hypothesis assumes a phase rotation of +a degrees on the first half of a burst and a phase rotation of −a degrees on the following half burst. Finally, the third hypothesis assumes that the data burst has a phase rotation of −a degrees on the first half burst and a phase rotation of +a degrees on the next following half burst. Any frequency offset is estimated based on a comparison of the results of the three separate demodulation attempts. Based on the frequency offset estimate, the transmitted signal may be demodulated without adjustment of the local oscillator.

Abstract: A communication system with variable filter bandwidth includes a first mixer circuit configured to receive a communication signal and shift the frequency range of the communication signal to a first frequency range. A second mixer circuit is configured to receive the same communication signal and shift the frequency range of the communication signal to a second frequency range. An activation circuit is coupled to the first and second mixer circuits so as to provide an activation signal that activates at least one of the mixer circuits. A plurality of filter circuits are provided such that each filter circuit is configured to receive a signal from a corresponding mixer circuit, when said corresponding mixer circuit is activated.

Abstract: A switched bandwidth filter in a digital signal processor selectively provides a first bandwidth characteristic or a second bandwidth characteristic by loading separate first and second sets of filter coefficients into the digital filter. The level of transients during coefficient switching is reduced by specially designing the respective coefficient sets using modifications obtained according to the invention. The modifications substantially match net gains at at least one of the internal nodes between filter sections provided by the first and second coefficient sets, respectively.

Abstract: A communication system with variable filter bandwidth includes a first mixer circuit configured to receive a communication signal and shift the frequency range of the communication signal to a first frequency range. A second mixer circuit is configured to receive the same communication signal and shift the frequency range of the communication signal to a second frequency range. An activation circuit is coupled to the first and second mixer circuits so as to provide an activation signal that activates at least one of the mixer circuits. A plurality of filter circuits are provided such that each filter circuit is configured to receive a signal from a corresponding mixer circuit, when said corresponding mixer circuit is activated.

Abstract: A method and system enables optimal call routing in a satellite communications network when a satellite subscriber has, for example, call forwarding active. Many satellite networks re-register a satellite subscriber's (e.g., the A-subscriber's) subscription information to a satellite gateway that is most cost efficient when the satellite subscriber initiates an outgoing call. If the called party (e.g. the B-subscriber) is distant from the satellite subscriber's home country, the distant gateway to which the re-registration occurs is likely to be far from the gateway of his or her native country, which is often to where call forwarding is directed. When an incoming call from a C-subscriber is detected for the A-subscriber, the call is handled normally until call forwarding is detected in the distant gateway. Once call forwarding is detected, a satellite gateway through which the call will be completed (e.g.

Abstract: A receiver (600) uses a scanning technique (100) to minimize scan time. An initial bandwidth setting is selected that covers multiple channel frequencies (106). A signal detection step (108) is performed looking for channel activity. As channel activity is detected, the bandwidth of a baseband filter (628) is narrowed (140, 146). The radio remains programmed to the same channel while the bandwidth is varied. Once the last signal detection with the narrowest possible bandwidth setting has been determined (144, 150, 152) the radio is programmed to that channel. Thus, more than one channel frequency is capable of being scanned without reprogramming the radio to a new channel for each scan.

Abstract: An analog processor for use with digital satellites is disclosed. The analog processor is connected between the receiving circuitry of the satellite and a pool of digital on-board processors, and segments the bandwidth of uplink RF beams into sub-bands that can be processed more readily with standard, low-risk, low-power digital processors. Using the present invention, the risk of employing a particular digital processor technology can be managed and optimized. The present invention also provides for the dynamic allocation and reallocation of the available on-board digital processing bandwidth based on the anticipated traffic pattern and changes in the traffic pattern. In addition, the present invention facilitates the use of standard and non-standard redundancy schemes at minimal hardware expense.

Abstract: The invention relates to a method for filtering radio frequency signals in so called multiband radio communication devices that operate in several frequency ranges and to a communication device operating in several frequency ranges. In the method according to the invention, the desired frequency range is selected so that of the amplifiers (62a, 62b, 62c; 72a, 72b, 72c) placed between the filters (61, 63) on the reception branch (11) or correspondingly between the filters (71, 73) on the transmission branch (12) the amplifiers that control the desired signal paths are activated.

Abstract: A filter device includes a first section for receiving data of a desired cutoff frequency. A second section operates for deciding whether the desired cutoff frequency is in a predetermined low frequency band or a predetermined high frequency band. The predetermined low frequency band is lower in frequency than the predetermined high frequency band. A third section stores data of filter coefficients corresponding to different cutoff frequencies in the predetermined low frequency band. A fourth section stores data of precalculated basic coefficients corresponding to different cutoff frequencies in the predetermined high frequency band. The precalculated basic coefficients are equal to values resulting from a part of calculation to provide final filter coefficients. A fifth section operates for calculating final filter coefficients from precalculated basic coefficients through a coefficient expanding process.

Abstract: A single chip superheterodyne AM receiver is disclosed herein. The receiver has a control pin for application of control signals to adjust a frequency response of a baseband filter to tailor its frequency response to a particular type of signal received by the receiver. Various techniques are described for enabling a complete superheterodyne AM receiver to be implemented on a single chip which receives an antenna input signal and outputs a digital data signal.

Abstract: The circuit arrangement utilizes both outputs of a mixer attenuating the image frequency, whereby one of the desired frequency bands is obtained from a “signal port” and the other desired frequency band from the “port of the image signal”. Thus a desired intermediate frequency signal band (IF) corresponding to the radio frequency Input signal (RF) can be selected using a switch (24), the intermediate frequency signal band (IF) being filtered by an intermediate frequency filter (20, 22). The frequency (LO) of the local oscillator is selected to be in the middle of the radio bands (RF).

Abstract: To accommodate for a release of uncleared spectrum in a wideband communication system (10) while improving isolation in a receiver (FIG. 4) between wideband carriers, a common intermediate frequency converter down-converts differing but relatively high frequency carriers, incident to the receiver, to corresponding differing but relatively low frequency carriers. Receiver chains (174-176) response to the plurality of relatively low frequency carriers each have a filter (140-144) arranged to isolate selected ones of the relatively low frequency carriers. In a radio frequency communication system having three or more frequency sequential carriers, the receiver chains (174-176) may include branches that have filters that further isolate carriers within the receiver by applying non-sequential carriers to the branches in each receiver chain.

Abstract: The direction-of arrival estimation by means of a subspace-based algorithm such as MUSIC or ESPRIT is formed by using reduced-bandwidth signals as compared with communication signal waves. The narrower-bandwidth signals is obtained by each mobile telephone transmitting a modulated version of a lower-transmission rate test signal as well as a communication signal wave or by band-pass filtering the received communication signal waves in a base station. A direction-of-arrival estimation is formed by using a reduced number of signals for the direction-of arrival estimation. The number of direction-of-arrival estimating signals is reduced by discarding a part of the received signals, by multiplexing the received signals by the sub-array and forming a direction-of arrival estimation for each sub-array, or by using an additional array antenna having a reduced number of elements.

Abstract: A frequency synthesizer includes a first oscillator that outputs a first oscillation signal. A first phase shifter outputs two first signals which are out of phase by 90°. A second oscillator outputs a second oscillation signal. A second phase shifter outputs two second signals which are out of phase by 90°. To a first mixer, one of the first signals and one of the second signals are input. To a second mixer, the other one of the first signals and the other one of the second signals are input. An adder adds combined outputs from the first and second mixers. A phase switching device changes the phase relationship between the two first signals or the two second signals input to the first mixer and the second signal. An input allowing/prohibiting switching device allows or prohibits the second signals from being input to the first and second mixers.

Abstract: A noise reducing AM receiver has a receiving stage for receiving an AM signal of carrier frequency separated from that in an adjacent channel by a predetermined spacing and that may have a noise component. A detecting stage is coupled to the receiving stage for detecting at least a first portion of the received AM signal. A filter is coupled to the detecting stage for extracting a spectral component from at least a first portion of the received AM signal. A noise detector is coupled to the filter for detecting the presence of a predetermined amount of noise in the spectral component and for providing a blanking control signal in the presence of at least the predetermined amount of noise. A first noise blanker is responsive to the blanking control signal to process at least one portion of the received signal in response to the control signal to reduce the audibility of the noise component.

Abstract: A multi-channel system is provided for both wide-band and narrow band low frequency transmission/reception of digital telemetry. The multi-channel system uses coherent detection having a high selectivity, and a quadrature detector having a high sensitivity. A filter is provided to average out noise. The multi-channel system oscillator is software controlled for scanning/multiplexing. The multi-channel system is used for data transmission over inductive, infrared, sonic and cable links.

Abstract: The invention provides a simple solution for a broadband transmitter/receiver for which the working bandwidth is split into at least two non-contiguous sub-bands. The invention uses a filtering means 50 which comprises at least two band-pass filters 51 and 52 provided with switching means 53 and 54. The use of two switched filters 51 and 52 makes it possible to use a single synthesizer 6 to scan two sub-bands of the working bandwidth. The frequency synthesizer 6 operates for one sub-band in supradyne mode and for the other sub-band in infradyne mode. In a variant, the invention uses a third filter and divides the bandwidth into three sub-bands.

Abstract: A circuit configuration for filtering a radio-frequency signal, in particular, in tuners for television sets, includes a control signal connection for feeding in a control signal, a controllable-frequency oscillator, at least one filter having an adjustable passband for a useful signal, and a device for providing a correction signal. The filters are, preferably, tracking filters whose filter band can be shifted by a control signal. At least one filter has a variable-frequency element with a first connection and a second connection. The first connection is coupled to the control signal connection, and the correction signal device is coupled to the second connection. For fine tuning production tolerances, the filters are supplied with a correction signal, which is applied to the other pole of the variable-frequency element of the filter as compared with the control signal. The value range of the correction signals is limited to the correction range and is much lower than the value range for the control signal.

Abstract: In a television receiver having a tuner 2 for converting a received signal from an antenna 1 to an intermediate frequency signal and supplying the intermediate frequency signal to a homodyne detector circuit through a filter device to extract a video signal, a variable frequency oscillator is provided for changing the frequency of the intermediate frequency signal such that the frequency of beat components between a local oscillating signal of the tuner and a harmonic signal of the intermediate frequency signal is coincident with a trap frequency of the filter device. The occurrence of interference due to the intermediate frequency signal introducing into the antenna can be prevented by a simple configuration.

Abstract: A communications receiver and a method for receiving and processing information transmitted on either a wide band carrier or a narrow band carrier having In-phase-Quadrature-phase (IQ) modulation, comprising, detecting a portion of the spectrum wide enough to encompass the wide band carrier (BW), converting the wide band carrier to baseband in I and Q components, each component having a bandwidth of BW/2, converting the I and Q components into further I and Q components to form components II, IQ, QI, and QQ of bandwidth equal to BW/4, where each of the sub-bands may contain a portion of the originally transmitted information. Operating in wideband mode, each of the components /is separately processed to extract portions of the originally transmitted information, and operating in a narrowband mode, each of the components containing information is separately processed within the narrow band transmitted carrier to extract portions of the originally transmitted information.

Abstract: A signal having a substantially uniform spectral distribution, e.g., a flat noise signal such as a signal ground, is provided at the input of a bandpass filter such as an IF filter of a receiver circuit, to thereby produce an output signal at the output of the bandpass filter. The output signal is processed in a limiter to produce a limited signal. An average frequency of the limited signal is determined, and the bandpass filter is adjusted based on the determined average frequency. According to one embodiment of the present invention, the bandpass filter comprises a Gm-C filter having a transconductance, and the filter is adjusted by adjusting the transconductance of the Gm-C filter based on the determined average frequency. According to another aspect of the present invention, a desired center frequency for the bandpass filter is identified. A resolution and a desired confidence interval are also identified.

Abstract: A high frequency apparatus includes an input terminal 21, a high frequency filter 22 to which a signal input into the input terminal 21 is supplied, a mixer 24, one input of which an output signal of the high frequency filter 22 is supplied to and an other input of which an output signal of a local oscillator 23 is supplied to, an intermediate frequency filter 25 to which an output signal of the mixer 24 is supplied, an output terminal 27 to which an output signal of the intermediate frequency filter 25 is supplied, and an electronic switch 30. The electronic switch is provided in the vicinity of the intermediate frequency filter 25, for making a passband characteristic of the intermediate frequency filter 25 substantially flat by closing both contacts, wherein opening and closing of the electronic switch 30 is controlled externally. Accordingly, the adjusting error of the high frequency filter can be reduced.

Abstract: A filter device includes a first section for receiving data of a desired cutoff frequency. A second section operates for deciding whether the desired cutoff frequency is in a predetermined low frequency band or a predetermined high frequency band. The predetermined low frequency band is lower in frequency than the predetermined high frequency band. A third section stores data of filter coefficients corresponding to different cutoff frequencies in the predetermined low frequency band. A fourth section stores data of precalculated basic coefficients corresponding to different cutoff frequencies in the predetermined high frequency band. The precalculated basic coefficients are equal to values resulting from a part of calculation to provide final filter coefficients. A fifth section operates for calculating final filter coefficients from precalculated basic coefficients through a coefficient expanding process.

Abstract: A data system, such as a computer network or a telecommunications system, has a base station and a number of nodes called network interface units (NIUs). Each NIU is assigned to one of a number of groups of NIUs. The base station transmits special data to the NIUs indicating which groups of NIUs are currently authorized to transmit upstream messages to the base station, where only the authorized NIUs are allowed to transmit upstream messages. When message collisions in the upstream direction becomes a problem, the base station can reduce the number of NIU groups that are authorized at any given time to transmit upstream messages, in order to attempt to reduce the rate of message collisions. In one possible embodiment, each NIU is assigned horizontal and vertical group words that identify to which group it is assigned. The special data contain additional horizontal and vertical code words that are monitored by the NIUs.

Abstract: An adaptive bandwidth control system optimizes radio reception by controlling intermediate frequency bandwidth and baseband bandwidth to reduce both interference and noise while remaining compatible with AM broadcasts using the NRSC-1 standard. An adaptive IF filter detects the presence of interfering undesired sources. The IF bandwidth is narrowed if any interferers are detected. Simultaneously, the frequency content of the demodulated baseband signal is analyzed to control an optimal baseband bandwidth so that any frequencies containing substantially only noise are eliminated.

Abstract: A PLL frequency synthesizer has: a reference frequency generator which issues a first frequency signal; a PLL section which outputs a phase error signal based on the first frequency signal and a second frequency signal; a first filter which smoothes the phase error signal output from the PLL section according to a first reference, and which outputs a first smoothed phase error signal; a second filter which smoothes the phase error signal output from the PLL section according to a second reference, and which outputs a second smoothed phase error signal; a switch which issues, in a switching mode, the first or second smoothed phase error signal output from the first filter or the second filter; an output frequency generator which issues a second frequency signal based on the first or second smoothed phase error signal to the PLL section; and a switch controller which controls the changeover of the switch.

Abstract: An improved satellite receiver front end architecture having a tuner chip and a demodulator/decoder chip. The tuner chip includes a lowpass filter having a configurable cutoff frequency, and the tuner chip uses a frequency signal to provide accurate adjustment of the cutoff frequency. A clock signal having a clock frequency is converted into a control voltage which determines the cutoff frequency of the lowpass filter. Consequently, the cutoff frequency may be increased by increasing the clock frequency, or decreased by decreasing the clock frequency. This configuration provides for improved cutoff frequency control in the presence of signal interference.

Abstract: A radiotelephone unit for conducting time division mutiplex receiving includes a two intermediate-frequency filters provided with the same performance, and switches for switching alternately the two intermediate-frequency filters every time when a receive slot is changed. First and third receive slots are associated with one IF filter and second and fourth receive slots are associated with the other IF filter.

Abstract: A radio communication apparatus is designed for a plurality of different radio communication formats, one of which can be selected. The radio communication apparatus includes a fixed-gain IF amplifier and a variable-gain IF amplifier. One is selected out of the fixed-gain IF amplifier and the variable-gain IF amplifier as an effectively used IF amplifier in response to which of the radio communication formats is selected. The fixed-gain IF amplifier is selected as an effectively used IF amplifier when a narrow-band radio communication format is selected. The variable-gain IF amplifier is selected as an effectively used IF amplifier when a wide-band radio communication format is selected.

Abstract: A circuit arrangement that reduces selected intermodulation. The circuit arrangement includes a signal amplifier coupled to a bandpass filter via an electrical path. Signal energy outside the passband is reflected back into the amplifier and causes intermodulation. The electrical path is constructed with a length that reduces intermodulation, where the length is an odd multiple of one-fourth the wavelength of a predetermined frequency in the passband. The length of the electrical path reduces intermodulation because certain signals reflected by the bandpass filter are approximately 180.degree., or an odd multiple thereof, out of phase. Energy of problematic signals that are near the edge of the passband or in the stopband is reduced, such as third order intermodulation product and pairs of signals that produce third order intermodulation products.

Abstract: A mobile radio wave receiver including an automatic gain control amplifier, an electric field intensity detection circuit, an error correction circuit, and an error correction error detection circuit is disclosed. The automatic gain controlling is selectively effected in accordance with the detected electric field intensity and a degree of the detected error correction errors. The mobile radio wave receiver further includes a bandpass filter with a first variable bandwidth and a waveform shaping circuit with a second variable bandwidth, wherein the first and second variable bandwidths are controlled in accordance with the detected electric field intensity and the degree of the error correction errors.

Abstract: To achieve a high passband attenuation, a switchable bandpass filter for a multiband tuner, includes at least a capacitance diode for frequency-tuning of at least a resonant circuit of the bandpass filter, and a switching diode arranged at the input and the output, this switching diode being switchable to either the blocked state or to the conducting state by DC voltages. The capacitance diode is additionally usable for blocking the bandpass filters and is integrated in the resonant circuit of the bandpass filter in such a way that, in dependence upon a switching potential, the capacitance diode couples the resonant.

Abstract: A receiver includes at least two intermediate frequency (IF) filters, with the first IF filter and a second filter having a narrower bandwidth than the first bandwidth. The receiver also includes a switch operable to select between the IF filters. In use, the receiver measures the signal strength of adjacent channels to the signal strength of a desired channel and switches to the second IF filter with a narrower bandwidth when a ratio of the signal strength of the channel and the signal strength of adjacent channels is less than a predetermined threshold. The predetermined threshold is determined based on considerations of range of detection and adjacent channel interference. The bandwidth of the filters in the receiver is also designed to optimize performance in consideration of both range of detection and adjacent channel interference.

Abstract: An amplifier (104) for a dual band device includes multiple amplifier stages coupled between an input (103) and output (105). The amplifier stages include a first amplifier stage (200) having a first amplifier (206), a second amplifier stage (202) having a second amplifier, and a third amplifier stage (204) having a third amplifier (210). A first bypass (218) in said first amplifier stage provides a bypass for signals in a first frequency band. A second bypass (250) is provided in the third amplifier stage, the second bypass to provide for signals in a second frequency band a signal path that bypasses the third amplifier. Signals in the first and second frequency bands are amplified by the second amplifier.

Abstract: A selective RF circuit for a double conversion tuner includes three double tuned bandpass circuits, each of which is tunable over approximately one-third of the tuning range. Switching diodes are used at the input and the output of each of the bandpass sections for selectively activating one of the bandpass sections and deactivating the remaining ones in response to a bandswitching signal. Operational amplifiers or other devices supply the input and output switching diodes by providing a current sink for the active bandpass and current sources for the inactive bandpasses.

Abstract: A radio communication apparatus is designed for at least first and second radio communication formats which prescribe first and second desired IF pass bandwidths respectively. The first desired IF pass bandwidth is greater than the second desired IF pass bandwidth. The radio communication apparatus includes an IF band-pass filter processing a first IF signal into a second IF signal and having a predetermined pass bandwidth corresponding to the first desired IF pass bandwidth. A demodulator recovers a first baseband signal from the second IF signal generated by the IF band-pass filter. A baseband filter processes the first baseband signal generated by the demodulator into a second baseband signal. The first baseband signal generated by the demodulator is selected as a final output signal when the first IF signal is of the first radio communication format.

Abstract: This separating device is provided with a transmitting filter and a receiving filter. Each of the transmitting and receiving filters comprises a variable capacity diode and a resonant element, and compose a band elimination filter. Each of the elimination bands of the transmitting and receiving filters can be adjusted by changing the capacity value of each variable capacity diode. The elimination band of the transmitting filter is adjusted so as to coincide with the receiving frequency of the communication channel currently used. The elimination band of the receiving filter is adjusted so as to coincide with the transmitting frequency of the communication channel currently used.

Abstract: A system for use with a CATV settop terminal measures the input RF carrier signal power level at several frequencies within the CATV RF input bandwidth upon system power-up. The system utilizes these measurements to selectively equalize and process the RF input signal depending upon the carrier frequency selected and the desired signal level to be input to the RF tuner. The system refines the signal level by specifically measuring the signal level of the selected carrier frequency. The system further improves RF tuner performance by dynamically limiting the bandwidth input to the RF tuner depending upon the selected carrier frequency.

Abstract: A method and apparatus for tuning an analog filter that is embodied in a larger circuit in which the analog input signal to the filter is, at some point prior to the filter, in digital form. The digital version of the input signal to the filter is stored in memory. The output signal from the filter corresponding to the stored input signal is digitized and compared to the stored digital input signal to the filter. Based on the known input signal and the known desired frequency characteristics of the filter, the desired output signal is a known quantity. If the actual output signal differs from the expected output signal, the filter is tuned accordingly. The process may be performed continually on all input data or on discrete sections of the input data.

Abstract: For eliminating the emphasis given an audio signal in the transmitter, an audio signal processor of an audio device (e.g., a car radio) contains a low-pass filter. In order to attenuate the spurious higher-frequency signal fractions in case of poor reception and accordingly low received field strength, the cutoff frequency of the low-pass filter is shifted in the direction of lower frequencies in accordance with a received field strength signal when the field strength becomes lower. In order to avoid external adjusting components and save pins on the IC chip, the field strength signal is supplied to an analog-to-digital converter and the latter supplies a digital signal to a low-pass filter whose cutoff frequency is variable. For this purpose the low-pass filter contains a number of integrated components one of which is connected or disconnected by a digit place of the digital signal in each case.

Abstract: A communication system is provided for increasing communication range between at least two radio communication devices without increasing the output power of transmitted radio signals from the devices, and without increasing the antenna gain of the received signals. Each radio device includes an oscillator for generating a carrier reference signal, and an SATPS receiver which receives at least one standard timing reference signal from at least one SATPS satellite. The received standard timing reference signal is used to continuously adjust the timing and synchronization of the oscillator to improve the accuracy of the carrier frequency signal. The improved accuracy in the carrier frequency signal may then be used to reduce the bandwidth of the modulated carrier frequency signals generated by the radio device to thereby increase the effective communication range and sensitivity of the device.