Abstract: A transmitter comprises a device (20) for frequency up-conversion of a communication signal having at least two consecutive frequency conversion stages, a power amplifier (27) for amplifying the output signal therefrom for obtaining a transmission signal and means (29) for extracting the transmission signal. It also has a device for frequency down-conversion of said extracted transmission signal to the same frequency as the communication signal before said up-conversion for creating a feedback signal. Said two devices use the same local oscillators (25, 26). The transmitter also has means for signal parameter adaptation of the communication signal on basis of the feedback signal for obtaining a desired character of the transmission signal.

Abstract: The invention relates to a method for shaping beams in a radio communication system. The first weighting vectors used for the beam shaping are chosen orthogonal to each other.

Abstract: A harmonic boosting technique for achieving higher overall system performance is described here. The technique is applicable to devices such as converter, combiner, synthesizer, and voltage control oscillator. A converter has anti-parallel diode pair (hereafter called APDP) cell or a modified Gilbert cell circuit for mixing an input signal with local oscillator (hereinafter called LO). A combiner has a combining circuit to combine even harmonics from LO. A synthesizer has a digitally synthesized network or a multiplier circuit for producing the even harmonics. A voltage control oscillator (hereafter called VCO) has a voltage control circuit for generating very low base frequencies.

Abstract: A satellite broadcast receiving converter has a housing, a waveguide, and a short-circuit wall, which are stamped out of a single metal sheet and are then folded.

Abstract: A method of receiving an FM digital audio broadcasting signal including a first plurality of subcarriers in an upper sideband of a radio channel and a second plurality of subcarriers in a lower sideband of the radio channel comprises the steps of mixing the digital audio broadcasting signal with a local oscillator signal to produce an intermediate frequency signal, passing the intermediate frequency signal through a bandpass filter to produce a filtered signal, determining if one of the upper and lower sidebands of the digital audio broadcasting signal is corrupted, and adjusting the local frequency oscillator signal to change the frequency of the intermediate frequency signal such that the bandpass filter removes the subcarriers in the upper or lower sideband that has been corrupted. A receiver that processes a digital audio broadcasting signal in accordance with the method is also provided.

Abstract: A radio receiver having a circuit arrangement for checking the quality of reception at an alternative frequency to a received transmit frequency. The radio receiver has two tuners for converting the received signals to two different intermediate frequencies and a switch, which is preferably switched by a microprocessor, for optionally forwarding signals from signal processing branches that are each connected to one of the tuners. This reduces the cost of implementing the second receiver, at the same time reducing the barely noticeable impairment of the set program when checking the quality of reception at the alternate frequency. The latter is achieved by positioning the switch upstream from an analog-digital converter, operating at a sampling frequency, of an intermediate frequency stage. The different intermediate frequencies are selected so that they both meet the following condition: f0=(n+R)fa where n is a natural number, and 0≦R≦1 applies.

Abstract: A direct conversion receiver for receiving a first input signal and directly downconverting it to baseband frequencies. The receiver includes a frequency translator which is responsive to a phase-split input signal having 2n components, wherein n is an integer greater than 1. The phase-split signal has a period T which is about n times the period of the first input. The frequency translator alternates, at a rate of about 2n/T, between switching the first input signal to a first output, and switching the first signal to a second output. A preprocessor is available to improve the switching characteristics of the phase-split input signal.

Abstract: A distortion correction circuit for a direct conversion receiver, the direct conversion receiver comprising a local oscillator for generating a local oscillator signal, a mixer for multiplying a radio frequency signal, and a local oscillator signal together and supplying the resultant mixer output signal to a demodulated signal, the demodulated signal path including a first low-pass filter for selecting a baseband signal at a first filter output terminal, wherein the offset correction circuit includes a squaring circuit for squaring the mixer output signal and supplying the resultant distortion estimate signal to a distortion estimate signal path, signal subtraction means for subtracting the resultant output signal at a subtraction point in the distortion estimate signal path, and adaptive processing means for equalising the transfer function of the distortion signal estimate path and the transfer function of the demodulated signal path between the mixer output and the subtraction point.

Abstract: A satellite receiving antenna (16) at a user location (14) receives satellite signals at a first frequency from a satellite (12). The satellite signals travel along a satellite signal route (42) within a look angle about the centerline (28) of the antenna (16). A terrestrial transmitter (20) transmits signals at the first frequency along a wireless transmission route (40) from the transmitter to the user location (14). The terrestrial transmitter (20) is located with respect to the user location (14) so that the wireless transmission route (40) is at a relatively large angle to the centerline (28) of the first antenna (16). The angle of the wireless transmission route (40) to the satellite antenna centerline (28) is large enough so that the terrestrial signals present at the location (14) result in terrestrial input signals from the antenna (16) which are less than an interference level with respect to satellite input signals produced by the antenna.

Abstract: A mixer circuit (21) includes first (31) and second (32) transconductance amplifiers, a switching circuit (34), and an oscillator processing stage (36). The transconductance amplifiers (31,32) generate differential current signals in response to modulated signals having different carrier frequencies. The oscillator processing stage (36) generates a local oscillator signal from a reference oscillator signal. The switching circuit (34) switches the differential current signals at the frequency of local oscillator signal to generate an intermediate frequency output signal.

Abstract: The invention relates to a tuner for converting a RF signal (110) into an IF output signal (202), said tuner comprising a mixer (111) for generating a first IF signal (201), processing means (114) for filtering said first IF signal (201) so as to generate said IF output signal (202).

Abstract: The present disclosure provides a receiver for receiving a narrow frequency deviation frequency modulated or phase modulated base band signal including a mixer for mixing the received narrow frequency deviation signal to generate an intermediate frequency signal, a band pass filter for filtering the intermediate frequency signal, and a narrow band discriminator circuit that performs a time domain expansion of the modulation deviation of the intermediate frequency signal and discriminates the base band signal.

Abstract: An enhancer that is added to a receiver to increase the dynamic range thereof. The enhancer comprises a downconverter for converting a received signal to an intermediate frequency of the receiver, and a coupler for sending the downconverted signal to the receiver. The dynamic range of the enhancer is greater than the dynamic range of the receiver such that the receiver can now receive strong signals via the enhancer. The downconverter may comprise a local oscillator that is operative to generate a local oscillator signal and a mixer operative to mix the received signal with the local oscillator signal in order to downconvert the received signal to the intermediate frequency of the receiver. In this respect, the enhancer may be an add-on device which is plugged directly into the antenna port of the receiver and immediately increases the dynamic range thereof.

Abstract: An in-flight entertainment system provides live video/audio programming to passengers and operators over an aircraft video/audio distribution system. The programming signals are derived from intermediate frequency (IF) signals that are produced by frequency downconverting satellite broadcast signals and supplied over a pair of IF signal output cables. The control signals and the DC power used in the frequency downconversion process are received over the same IF signal output cables, but in a reverse direction. A bias-T connector is provided in each of the IF signal output cables to extract out the control signals and the DC power.

Abstract: A digital communication system and method is provided for increasing bit-rates while maintaining the reliability of transmitted digital information and avoiding increased power demands. The communication system includes a transmitter that modulates one or more bits onto a carrier signal to generate and transmit a first transmission signal during the first part of a pulse time TB, receives an additional bit, and based on the value of the additional bit, either transmits the first transmission signal again during the second part of the pulse time TB or transmits a second transmission signal during the second part of the pulse time TB.

Abstract: This invention provides a wireless communication device having high receiving sensitivity and made compact at low cost and having a high general purpose property, and able to transmit and receive information by multiplying the frequencies of plural channels several times and arbitrarily selecting all wireless frequency bands in a predetermined range.

Abstract: The invention relates to a communication system with system components for ascertaining the authorship of a communication contribution (40, 41) put in into a communication end device through

Abstract: A first periodic voltage waveform (20) is downconverted into a second periodic voltage waveform (35, 36). A plurality of temporally distinct samples (SA1, SA2, . . . ) respectively indicative of areas under corresponding fractional-cycles of the first voltage waveform are obtained. The samples are combined to produce the second voltage waveform, and are also manipulated to implement a filtering operation such that the second voltage waveform represents a downconverted, filtered version of the first voltage waveform. The second waveform is driven by an amplifier stage (25), and the second waveform can be advantageously constructed so as to permit the amplifier stage to perform internal resets, offset corrections and other ancillary amplifier stage adjustments without losing information in the first waveform.

Abstract: A first periodic voltage waveform (20) is downconverted into a second periodic voltage waveform (35, 36). A plurality of temporally distinct samples (SA1, SA2, . . . ) respectively indicative of areas under corresponding fractional-cycles of the first voltage waveform are obtained. The samples are combined to produce the second voltage waveform. The samples can be manipulated to provide gain adjustment to the second voltage waveform. The samples are obtained by charging a sampling capacitance in response to a current waveform that corresponds to the first voltage waveform. The use of different sampling capacitances during respective predetermined time intervals permits the signal strength of the first waveform to be determined from observation of the second waveform.

Abstract: In a conventional Time Division Multiple Access (TDMA) wireless system, the specified distance between a mobile unit and the base transceiver system (BTS) cannot exceed predetermined distances because of time slot synchronization constraints. Furthermore, the varying distances between mobile units and the BTS create timing differences in the random access control channel (RACCH) bursts in the initial uplink signal from the mobile stations. In this approach to extending TDMA system coverage, in-band translator components are located in the center of remote cells which would normally contain a base transceiver system. The in-band translators include a loop back circuit that permits a host BTS to measure the backhaul propagation time delay by sending test access signals between the host BTS and the distant in-band translators.

Abstract: The present invention provides an improved receiver capable of receiving either a satellite broadcast signal or a cable TV signal associated with a TV. The inventive receiver comprises a first BPF for filtering received broadcast signals, a first local oscillator for generating a first oscillation signal, a first mixer for generating a first IF signal, a SAW filter producing a waveformed band signal, a second local oscillator, for generating a second and a third oscillation signal, a second mixer for generating a second and a third IF signal, a switching block for switching the second and the third IF signal, a second BPF for producing a baseband channel signal selected from the cable TV signal, a first LPF for producing a baseband I signal of satellite broadcast channel, a shifter for shifting a phase of the third IF signal, a third mixer for generating a phase-shifted third oscillation signal, and a second LPF for producing a baseband Q signal of satellite broadcast channel.

Abstract: A dual-band receiver for a wireless communication device having multi-slot capability. A first oscillator generates a relatively high frequency traffic LO signal. A second oscillator generates a first relatively low frequency signal, and a third oscillator generates a fixed low frequency signal. A first mixer mixes the first and fixed low frequency signals to produce a relatively high frequency monitor LO signal. A switch selects the traffic LO signal when the receiver is in a traffic slot and the monitor LO signal when the receiver is in a monitor slot. The selected LO signal is provided to a second mixer along with the received signal to produce a first IF signal. A third mixer mixes the first IF signal and the fixed frequency signal to produce an output signal.

Abstract: Noise and multipath distortions in a broadcast receiver are reduced by an optimal antenna/frequency diversity concept in which the distortions in the audio signal are evaluated to choose a different antenna and/or a different frequency for at least signal parts.

Abstract: An input signal (IN) is filtered (605) to remove aliases and a switched capacitor network (610) undersamples this signal to provide a downconverted, near-baseband signal. An amplifier (615) adjusts the amplitude of this signal to match a digitizer (620). The digitized output is converted into first phase and second phase signals which are then filtered (640) and decimated (645) to further reduce the sampling rate. The downconverted first and second phase signals, rather than higher frequency signals, control the gain function (AGC) for the amplifier (615). The switched capacitor network (610) provides for both tuning and downconversion of the desired signal to a lower frequency for further processing, thus reducing the frequency and power requirements of an associated amplifier and analog-to-digital converter (digitizer).

Abstract: Frequency translation and applications of same are described herein. Such applications include, but are not limited to, frequency down-conversion, frequency up-conversion, enhanced signal reception, unified down-conversion and filtering, and combinations and applications of same.

Abstract: In a direct-conversion receiving apparatus it is possible to prevent unnecessary emission from an antenna as well as deterioration of the error rate characteristics caused by DC offsets, a power dividing unit 104 divides an RF signal amplified in an RF amplifier 103 into four signals of first through fourth RF signals, phase-shifters 105-107 shift the phases of the second through fourth RF signals by 180°, 90° and 270°, respectively and mixers 108-111 generate first through fourth baseband signals by mixing the first RF signal and second through fourth RF signals after phase-shifting with local signals from a local oscillator 112, respectively.

Abstract: The present invention provides for a system and method for improvement of radio transmitter and receiver frequency accuracy for a local radio communication unit that communicates digital data with a remote communication unit. In the local unit the received radio signal is down-converted, and converted to complex baseband digital samples by an analog-to-digital converter. A downlink digital phase rotator applies a fine frequency shift to the samples in accordance with a receiver frequency offset command. The resultant baseband signal is used by the data demodulator and by a receiver frequency error estimator to obtain receiver frequency errors. A data modulator generates baseband complex samples which are shifted in carrier frequency by an integrated uplink digital phase rotator in accordance with a transmitter frequency offset command. The modulated samples are then converted by a digital-to-analog converter and upconverted in frequency for radio transmission to the remote unit.

Abstract: A down converter, such as a low noise block (LNB) converter, of the outdoor unit of a terrestrial microwave or satellite receiving system includes apparatus for automatically controlling the conversion gain of the down converter. In one embodiment the automatic gain control apparatus, including a gain controllable RF stage and a gain control signal generator for generating a gain control signal in response to the output signal of the down converter, are both included within the outdoor unit. In another embodiment, the gain controllable RF stage is included in the outdoor unit, but the gain control signal generator is included in the indoor unit of the receiving system and the gain control signal is coupled to the outdoor unit in direct or in encoded form. In the latter case, the encoded gain control signal can be coupled to the down converter via the coaxial cable connected between the outdoor and indoor units.

Abstract: A receiver for receiving a digital radio broadcast in which additional information is multiplexed with audio information includes a memory for storing the additional information, an LCD, and a bookmark button. When the bookmark button is depressed during reception of a program, a control unit stores additional information of the program in the memory as bookmark data. The bookmark data stored in the memory is displayed on the LCD. When data, for example, “Modern Jazz”, is specified as search data, the control unit sequentially searches programs currently being broadcast or programs to be broadcast later, detecting and tuning in to a program which includes the search data in the additional information thereof. Alternatively, the additional information of the detected program is displayed on the LCD, tuning in to the program in accordance with an operation by the user.

Abstract: An object of the present invention is to integrate circuits for frequency conversion processing of an input signal of the GHz band. In a receiver, an input signal from an antenna is amplified after components thereof outside a frequency band for communication network being removed, and is supplied to an arithmetic processing unit. A plurality of sampling circuits within the arithmetic processing unit respond to a plurality of clock signals of which frequencies are equal and of which phases are different, respectively, and sample the input signal after amplification. The sum-of-products arithmetic unit within the arithmetic processing unit responds any one of the clock signals and performs sum-of-products operation periodically using a plurality of sample signals exhibiting the sampling results of all the sampling circuits, respectively.

Abstract: Station scan circuitry for a radio-frequency receiver and corresponding methods are disclosed that efficiently determine the presence of a station on available channels. The station scan circuitry includes circuitry that determines if the signal power on a given channel exceeds a threshold value. Additional circuitry compares the channel signal strength and the adjacent channel signal to determine if a ratio of the two exceeds a threshold level. If both the signal power and the signal strength ratio are sufficient, the station scan circuitry indicates that a station has been found. To make the signal strength comparison, the station scan circuitry includes circuitry for determining a post-filter signal strength and a pre-filter signal strength for the received signal.

Abstract: A radio apparatus includes a plurality of receiving systems connected to multiple antennas providing diversity, respectively, each receiving system including an antenna terminator and a preamplifier. After one receiving system is discriminated from another receiving system based on radio signals received by the receiving systems, respectively, a controller controls the one receiving system such that an antenna terminator is inactive and a preamplifier is active and, at the same time, further controls the other receiving system such that an antenna terminator is active and a preamplifier is inactive.

Abstract: An analog circuit for receiving satellite signals through an antenna. The circuit includes frequency transposition circuits and an analog/digital converter. Each frequency transposition circuit includes at least two frequency dividers of which due first is programmable so as to provide division ratios 140 and 143. The other divider provides one of the division ratios of 10 or 11. A third divider provides ratios of 3, 5, 7 or 8. These division ratios enable a single analog integrated circuit topography to allow a large number of possible applications including civil or military receivers operating on the GPS constellation or on the GLONASS constellation.

Abstract: Apparatus, and an associated method, for the IF stage of a receiver, such as the receive portion of a multi-mode mobile station. Direct conversion of an IF-stage receive signal is made into the digital domain through the use of a &Sgr;&Dgr; analog-to-digital converter. Increased portions of the receiver processes signals in the digital domain using digital-domain circuitry.

Abstract: A hardware-efficient transceiver. The transceiver includes a digital circuit for converting baseband signals to intermediate frequency signals. A signal source provides a first periodic signal of a first frequency. A direct digital synthesizer provides a second periodic signal of a second frequency from the first periodic reference signal. An upconverter circuit digitally upconverts the baseband signals to digital intermediate frequency signals using the second periodic signal A digital-to-analog converter converts the digital intermediate frequency signals to analog intermediate frequency signals using the first periodic signal. In the transceiver implementation, the digital circuit upconverts a first transmit signal from a first frequency to a second frequency in response to the second periodic signal and provides a digital transmit signal in response thereto. A second circuit is provided for converting the digital transmit signal to an analog transmit signal.

Abstract: A receiver invention includes an antenna circuit unit having a high-frequency amplifier circuit connected to a reception antenna, a receiving circuit having a channel selection key, and a coaxial cable for connecting the antenna circuit unit and the receiving circuit. The receiving circuit includes a voltage adding circuit for adding, upon channel selection based on an operation of the channel selection key, a DC voltage corresponding to a frequency band to an AGC signal to supply it to the high-frequency amplifier circuit through the coaxial cable. A high-frequency gain of the high-frequency amplifier circuit is changed by using a voltage corresponding a frequency band of a received broadcasting frequency and an electric field intensity thereof.

Abstract: A monolithic active frequency selection circuit includes an input presenting a frequency-dependent impedance and a first gain block configured to provide less than unity voltage gain, a high input impedance and a low output impedance. An output of the first amplifier is coupled to the frequency selection circuit input. The frequency selection circuit includes a first phase shifter that, in one aspect, is formed by a first capacitor coupled between the first port and a reference voltage. The frequency selection circuit also includes a second amplifier configured to provide greater than unity voltage gain. The second amplifier has an input coupled to the output of the first amplifier and an output coupled to the input of the first amplifier. The frequency selection circuit further includes a second phase shifter, which may be formed from a capacitor coupled between the output of the second amplifier and a reference voltage.

Abstract: A global communications network comprises a plurality of aerial platforms or vehicles deployed at an altitude in or near the stratosphere and permitted to drift in a controlled manner such that each platform adjusts its position relative to other aerial platforms. Each aerial platform has a propulsion system and control surfaces and preferably includes a lighter-than-air component to maintain lift in an economical manner. Each aerial platform also includes a payload, means for communicating with other aerial platforms and a control system including location-finding equipment and a processor adapted for directing the platform's propulsion system and control surfaces to effectuate changes in the aerial platform's position relative to other aerial platforms based on position information, and optionally on other factors such as terrestrial demand for services provided by the payload of the aerial platforms.

Abstract: A communications system includes at least one low earth orbit first satellite (10), at least one second satellite (11) in other than a low earth orbit, and a ground segment (12) that includes a plurality of user transceivers (78, 80, 82, 84) and at least one gateway (76) coupled to a publicly-accessible terrestrial communications system, such as a PSTN and/or a fiber optic network. The first satellite includes a first transceiver for communication with the at least one gateway, a second transceiver for communication with at least one user transceiver, and a third transceiver for communication with the at least one second satellite. The first, second and third transceivers are switchably coupled together on-board the first satellite by on-board processors, and a switching matrix for relaying a user communication between the at least one gateway and the at least one user transceiver via the at least one second satellite.

Abstract: A wideband receiver capable of handling the new extended A and B cellular spectrum is provided. Portions of the band are converted using analog conversion into a frequent between Fs/4 and Fs/2 where Fs is a sampling frequency of an analog-to-digital converter. Other portions of the band are converted such that when they are sampled by the analog-to-digital converter aliasing causes them to lie in the baseband frequencies between zero and Fs/2, and more particularly in baseband frequencies which do not interfere with the other converted bands.

Abstract: A satellite communications system provides an information channel between remotely located transmitters and receivers. A virtual satellite system provides the same service, but divides the signal either in power or in data content into subchannels such that any particular signal is conducted to the intended receiver via a plurality of traditional satellite channels. The receiving terminal accepts the plurality of signals simultaneously from a possible plurality of satellites, combining the subchannels comprising the virtual channel into the original signal content as if conducted via a single channel. The receiving antenna system receives satellite subchannel signals from a plurality of directions using multiple antennas or a single antenna with multi-direction capability. Prior to signal combining, the receiver necessarily time-synchronizes the plurality of subchannels by introducing time delay in some channels before combining the subsignals into the original composite.

Abstract: A method of interleaving data for transmission is provided wherein first and second interleaving patterns for arranging data symbols in a source data stream into first and second transmitted data streams are selected. Each of said data symbols has at least one bit. The first and second transmitted data streams are transmitted substantially simultaneously on separate transmission channels to at least one receiver. The first and second patterns are used to transmit the data symbols in the source data stream in a different order on the respective transmission channels to maximize recovery of the source data stream when the transmission channels are blocked. The selected interleaving patterns can involve reordering the data symbols throughout the first and second transmitted data streams using different reordering criteria. The reordering criteria can vary on a frame-by-frame basis if the source data stream is time division multiplexed. Complementary data can be sent on respective transmission channels.

Abstract: A system for transmitting instructions from a master control facility (50) to a number of remotely located player units (11-14). The remotely located player units communicate through a mobile cell site (10). Cellular communication links (16) are provided to link the remote units (11-14) to cell site (10). Cell site (10) is linked to a satellite arrangement (20) via a communication link (21). The master control facility is linked to the satellite arrangement via communication link (23).

Abstract: A method for providing location based intercept in a satellite communications system (10) includes the steps of determining a location area of a party (220), determining whether the location area is one to be monitored (240), and conditionally routing the call to an intercept gateway (250). An intercept gateway (32) is a gateway that intercepts all or part of the calls received, and can also function as a home gateway (30) or a visiting gateway (40).

Abstract: A miniature RF receiver in the UHF frequency band. This receiver design is specific to the implementation of a digital module, as it contains no downconversion elements, and provides the capability of defining the operational frequency with cascaded tunable filter stages. The tunable filters are combline filters with tuning varactor diodes terminating each printed resonator. The 1 dB bandwidth of the filter is 7 Mhz, and for resonator length of 31 degrees (at the center frequency), the filter bandwidth remains nearly constant across the tunable frequency range. The capacitance of a varactor diode is a function of applied voltage. By controlling the voltage to each varactor, the filter response can be tuned across the operational frequency range of 50 Mhz.

Abstract: In a mobile communications system (10), system (10) through base station (40) or one or more satellites (20) monitors bandwidth availability and determines acquisition channel resource information. The system (10) broadcasts the acquisition channel resource information to the mobile units (30) via satellite (20). According the acquisition channel resource information, the mobile units (30) are enabled at select time instances to access the acquisition channel, obtain a traffic channel and transmit their messages to base station (40). Thus, mobile units (30) are enabled to access system (10) when resources are available.

Abstract: A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

Abstract: In a satellite communication system, a user terminal (11) seeks response from a selected earth station (7A-E) for a request for service based analysing the signal quality of broadcasts from earth stations (7A-E). Whichever earth station (7A-E) responds calculates which earth station (7A-E) can best meet the request for service. If it is another earth station (7A-E), the user terminal (11) is intructed to redirect the request for service thereto and, once in contact, the user terminal (11) addresses all new requests directly thereto, until the best earth station (7A-E) calculates that there is a better earth station (7A-E), and instructs the user terminal (11) to address all future requests for service thereto.

Abstract: A satellite communications system comprises satellites 9A-C, earth stations 7A-E, user terminals 11 and controlling gateways 3 in the form of mobile satellite switching centers 5A-E. Access with a user terminal 11 may be gained to a terrestrial telephone system 1 by earth stations 7A-E contacting the satellites 9A-C and by the satellites contacting the user terminals 11. The satellites 9A-C periodically broadcast messages indicative of the earth station 7A-E with which they are instantly in contact. The user terminal 11 listens to and logs these broadcasts to keep a list of the relative number of times each earth station 7A-E can be heard. When calling into the system, the user terminal pages earth stations in descending order of number of entries in the log. When in contact, the user terminal 11 sends the log to the system. When subsequently trying to contact the user terminal 11, the system uses earth stations in descending order of number of entries on the log, last received from the user terminal.

Abstract: A satellite position/arrival-time calculating section calculates the arrival date and time at which a communication satellite is to arrive in a communicable area where the communication satellite can communicate with a satellite communication terminal apparatus, and creates communicable date and time information. A timer controls a power supply control circuit in accordance with the arrival date and time information created by the satellite position/arrival-time calculating section. The timer automatically controls the power supply control circuit so as to supply communication power to a satellite communication circuit section while the communication satellite is in the communicable area and so as to stop the supply of the communication power at the time when the communication satellite leaves the communicable area.