Abstract: A Digital Post-Detection (Post-Discriminator) FM spatial diversity combination circuit improves performance for fading channels typical of cellular radio operating environments. A feature of this system is its flexibility. The system can be configured to use signal quality information in a manner which is appropriate for a given radio environment. Also, the weighting information can be derived from various sources and then processed to accommodate various situations. This spatial combiner has the ability to perform as a "hybrid" combiner. For example, this circuit can combine signals from various receivers based on soft weighting information, as in a maximal ratio combiner, or on hard weighting information, as in a switching combiner. The basic circuit includes a normalizing circuit (21, 22, 23) which receives the digitized received signal strength indicator samples from each of first and second receivers (11, 12) and generates first and second weighting signals.

Abstract: A receiver has a plurality of receiving systems connected to a plurality of antennas, respectively, and a selective switching circuit for carrying out selective switching between output signals from the plurality of receiving systems to output an output signal from a receiving system in the most satisfactory receiving state, wherein the selective switching circuit has a fuzzy inference operation unit for discriminating receiving states of respective receiving states by a fuzzy inference. Accordingly, it is possible to synthetically judge the receiving state of the receiver to easily and stably select the optimum receiving system in the receiver.

Abstract: A wireless infrared (IR) communications system (100) for communicating packetized information (302) between a control module (12) and a plurality of UMs (14) via infrared transceivers (300/320) is described as having a selectable communications path. In this system at least the user module (14) has a plurality of IR device arrays (A1-A6) for receiving IR signals (312/312') in relatively narrow IR field of view sectors, and selection circuit (20), coupled to said plurality of IR device arrays (A1-A6), for selecting a communication path between the control module (12) and one of said plurality of IR device arrays (A1-A6), based at least partly on received signal (302') qualtity, so as to overcome reception errors caused by multipath interference.

Abstract: In a transmitting section, a modulator modulates a first carrier with data o be transmitted, thereby producing a modulated output f.sub.m, a local oscillator generates a local oscillating signal to be used as a second carrier f.sub.LO, a mixer mixes the modulated output and the local oscillating signal, thereby generating waves of different frequencies. These waves include an upper side band wave f.sub.LO +f.sub.m and a lower side band wave f.sub.LO -f.sub.m. A transmitting antenna radiates electromagnetic waves into the air, which includes the waves of different frequencies generated by the mixer. In a receiving section, a receiving antenna receives the electromagnetic waves, a diversity section extracts at least one of the upper side band and lower side band waves f.sub.LO +f.sub.m, f.sub.LO -f.sub.

Abstract: Two or more signal paths are provided for receiving a radio frequency signal. One or more signal paths include conventional bandpass filters for eliminating interference and noise signals. One or more remaining signal paths include reduced filtering devices for increasing the sensitivity of a radio frequency receiver to the desired signal. Each of the receiving paths is coupled to a respective radio frequency amplifier. Provided that each radio frequency amplifier has equivalent current-source output impedances, the output signals from each amplifier are added constructively if they are in-phase. If the output signals are out-of-phase, a phase inverter inverts the phase of one signal so that the signals may be added constructively. The combined signals of the two or more radio frequency amplifiers pass through various signal processing components associated with conventional superheterodyne receivers. A control unit produces gain variation signals for controlling the gain of each radio frequency amplifier.

Abstract: A method of estimating the quality of a communication channel from a differential phase angle between a received signal and the corresponding transmitted phase angle employs determining a signal to impairment ratio (SIR) as an indicator of channel state information (CSI). A maximum likelihood estimation procedure is employed to calculate this CSI metric as a function of the differential phase angle between be received signal and transmitted signal An alternate embodiment employs an estimation that incorporates average SIR information for a Rayleigh fading channel. Since CSI is derived from the phase angle of the received signal, and does not require signal amplitude information, it is attractive for use with differential detectors, phase-locked loops (PLLs) and hard-limited signals. The CSI provided can be used for implementing post detection selection diversity, by selecting the signal from a plurality of antennae which has the best SIR.

Abstract: The antenna diversity system for mobile reception of VHF and UHF waves has a plurality of antennae; an antenna distributor connected to each of the antennae to receive antenna signals from the antennae and having a plurality of inputs and sets of outputs; a plurality of antenna switches, each of the antenna switches being connected to one of the sets of outputs of the antenna distributor; a plurality of tuners, each of the tuners connected to one of the antenna switches and producing one of an intermediate-frequency signal and demodulated signal; a plurality of diversity processors, each of the diversity processors being connected to a tuner to receive an intermediate-frequency or demodulated signal therefrom and also to the antenna switch of the tuner connected thereto via a control line and being structured to carry out a signal evaluation of the signal received in the diversity processor to control the antenna switch to switch through a more favorable input signal to the tuner connected to it.

Abstract: In a radio mobile system in which the radio signals are received by at least two antenna, the signals are filtered, weighted and then combined before being sent to an equalizer. The weighting coefficients are calculated as a function of signals corresponding to the power level received by each antenna and signals which is represent the quality of reception of each antenna. Furthermore, an equalizer control signal is generated from the combination of signals, weighted by the weighting coefficients, corresponding to the time response of the transmission channel to a single impulse.

Abstract: A two wire modem selects a carrier frequency in a baud rate from a predetermined plurality of carrier frequencies and baud rates to communicate with another modem over a communication media in a full duplex mode based on signal and echo characteristics of the communication media estimated by the modem. In addition, the processes of estimating channel characteristics and estimating range are combined in a common start up procedure comprising a plurality of successive time segments for a call modem to communicate with an answer modem over a communication media. Still further, a method is provided for switching from a primary communication media connection to a secondary connection of a data communications network for communication by first and second modems coupled to the network. More specifically, when a failure is detected in the primary connection, the secondary connection is qualified before switching thereto.

Abstract: A radio receiver system for receiving double sideband signals from a plurality of antennas (N1,N2) having different reception characteristics detects a reduction in power in one of the sidebands of a received signal, due to multiple path reception or other disturbances. The system then selects for use by the receiver a signal from an antenna less affected by the disturbances.

Abstract: Diversity receiver having many diversity branches comprises adaptive equalization sections for equalizing the training signal sampled on the basis of adjustable tap coefficients, and adjusting the tap coefficient every code element in the training signal so as to minimize the intensity of an error signal defined by the difference between the equalized training signal and the already-known training signal, error signal intensity detecting sections for detecting the intensity of the error signal every code element, a switching section for switching to a diversity branch having the minimum signal intensity of error signals in the respective diversity branches.

Abstract: A diversity circuit is disclosed which includes CIR estimation circuits, error computers for computting the ratios of the estimated CIR power to the error power between the estimated and actual received signal for respective received signals, a comparator for comparing respective ratios, and a selector for outputting the received signal and the CIR corresponding to the maximum power ratio. A frame phase (or sampling timing) estimation circuit using the diversity circuit further includes a delay circuit for providing a received signal with different delays, whereby the selector outputs the delayed received signal and the CIR corresponding to the maximum power ratio.

Abstract: An apparatus comprising a Viterbi decoder which decodes received convolutional code data in accordance with the Viterbi algorithm and provides path metrics. Among the path metrics, a path metric comparator detects the maximum and minimum path metrics for each data symbol. The path metric comparator selects the minimum difference among differences between the maximum and minimum path metrics. An apparatus also comprises a field strength detector which detects the electromagnetic field strength of a radio signal containing the convolutional code data. Upon the minimum path metric difference and the field strength, an interference detector checks if interference exists in the radio signal. The minimum path metric difference may be used for an antenna diversity system.

Abstract: An antenna selection technique is used in an RF communincation system in which user modules (UM) communicate with at least one node. The UM's and nodes each have multiple antennae. The combination of each UM and node antenna is evaluated at the UM. Based on at least signal quality, the UM selects its antenna and the best node antenna for use. An alternate antenna is selected if a person is determined to be present in a predetermined area adjacent a UM corresponding to a predetermined RF power level.

Abstract: In a space diversity receiver, multiple signal paths are connected respectively to antennas for multipath reception. Each signal path includes a digital demodulator coupled to the antenna and an impulse response detector, or autocorrelator connected to the demodulator for deriving a channel impulse response of each one of the multiple paths. A maximum response detector is connected to each impulse response detector for detecting equalizable delay components which give a maximum response value and a unequalizable delay components. A power ratio of the unequalizable delay components to the equalizable delay components is derived for each signal path and a minimum value of the power ratios is determined and one of the signal paths in which the mininmum value is detected is selected.

Abstract: In an antenna-selection diversity transmission and reception equipment which is in digital communication with a transmission and reception equipment having a single antenna, and performs transmission and reception with time division by using the same radio frequencies, the antenna-selection diversity transmission and reception equipment comprises a plurality of antennae, a receiving part having a receiving unit, comparing unit and selecting unit which are adapted for a receiving-antenna selection diversity, and a transmitting part having a memory unit for storing antenna information that was selected by the receiving part. An antenna for transmission is selected from the plurality of antennae at the time of transmission in accordance with the information of the memory unit.

Abstract: A modem for receiving data sent from a remote device over a communication channel by using a single carrier modulated signal, the modem including a receiver for receiving the modulated signal and for receiving a line probing signal sent by the remote device over the channel, the receiver being capable of receiving the modulated signal over any one of a plurality of frequency bands; a line probing processor for measuring characteristics of the channel based upon the received line probing signal; and a selector for selecting one of the plurality of frequency bands, said selection being based upon the measured characteristics of the channel, said selected frequency band to be used for receiving the modulated signal from the remote device.

Abstract: A process for transferring data packets in a network having a master station, plural subscriber stations, and a common gated channel, wherein each subscriber station records the data package received by it and a transmission quality level of the data package received by the respective subscriber station; each subscriber station reports the recorded transmission quality levels to the master station; the master station determines at least one data routing for each subscriber station on the basis of the transmission quality levels reported to the master station; and a data packet directed to a certain subscriber station is transferred according to the determined data routing. The process is particularly suitable fo the transferral of data packets via the supply lines of a medium- and low-voltage network.

Abstract: A repeater for a wide area coverage multiple repeater system (100) includes a receiver (220) and a transceiver (230). The receiver (220) receives a received signal from a portable or mobile communication unit (130) on an inbound channel. The received signal is routed to a receive signal strength indicator (RSSI), a bit error rate (BER) detector, or a similar devices for differentiating a received signal quality characteristic. The transceiver (230) includes a transmitter (232) for repeating the received signal on an outboard channel and a receiver (234) for monitoring presence of an outboard channel activity. A controller (260) enables the transmitter (232) to retransmit the received signal, based on the received signal quality characteristic, and in absence of the outboard channel activity.

Abstract: A switching system for a television receiver allows a user to specify which of several input connectors is assigned to which of several signal sources. Thereafter, upon selection of a particular signal source, the system automatically selects the input connector associated with the selected signal source.

Abstract: A receiver for receiving angle-modulated radio signals includes detecting occurrence of interference from adjacent channels when an evelope of demodulated signal of the received radio signals exceeds a threshold. This receiver improves the quality of received signals, attenuates them, limits the amplitude thereof, or blocks them and to insert interpolation signals in replacement thereof when the detection output is transmitted thereto.

Abstract: A spatial diversity system for digital mobile telephone networks which comprises at least two antennas, one antenna being part of a primary (or master) unit and the other being part of a diversity (or slave) unit, each unit having processing means to detect the "quality" of digital audio signals received by their respective antennas, the "quality" comprising link quality, AGC level and parity errors; the primary unit being capable of comparing the "quality" of the audio signals received by each antenna, selecting the higher "quality" signal and transmitting the higher "quality" signal to the telephone network.

Abstract: An FM receiver includes a first antenna and a second antenna. A first pulse generator produces a first pulse according to a noise signal included in the signal received by the first antennas, and a second pulse generator produces a second pulse according to a noise signal included in the signal received by the second antennas. A calculation circuit including shift registers is provided for shifting data, which is either one of the first and second pulses, in one direction in accordance with the first pulse from the first pulse generator and for shifting the switch data in another direction in accordance with the second pulse from the second pulse generator. Also, a switch circuit is provided for switching on a transmission line for a signal received at either one of the first and second antenna in response to the data produced from the calculation circuit.

Abstract: The invention relates to a signal diversity arrangement for a mobile reception, comprising a receiver and a diversity processor, which receives the input signals and applies a different input signal to the receiver when interference occurs. The diversity processor comprises an interference detector operating in the analog mode and a comparator, to whose first input is applied the output signal of the interference detector and to whose senond input is applied a suitably set voltage V1. The comparator shows on its output the occurence of interference by way of a binary signal when the threshold voltage V at the second input is exceeded.

Abstract: A receiver includes a video switch operated by a controller for selecting antenna or auxiliary (baseband) video signals for display. When placed in a "VCR" operating mode the controller first selects the auxiliary input for display. If a video signal is not present at the auxiliary input the controller causes the switch to select the output of a tuner thereby providing an automatic signal search to locate the VCR signal which may be applied to either of the antenna and auxiliary inputs. An extension of the search includes tuning the tuner to channel 3 and, if no signal is found, tuning the tuner to channel 4. Upon failure to find an active video signal on either channel the tuner is returned to the last channel received prior to selecting the VCR mode of operation thereby releaving the user of both mode selection and channel selection requirements for locating the VCR signal.

Abstract: An arrangement ensuring the change-over of two channels through which the same digital information is conveyed with automatic data alignment over a .+-.3.5 bit range comprises for each channel an array of buffer stores operating at a write rate H.sub.i /N.sub.i (where i=1, 2), an oscillator operating at a rate H which provides reading of the buffer stores at the rate H/N and being synchronized in phase-opposition with one or the other of the write rates, and a logic comparator controlling the write rates H.sub.i /N.sub.i, the routing of the write rates to the input of the oscillator, as well as a change-over switch for the data.In the buffer store of the channel assumed to be the one whose quality degrades, the data are converted into N parallel streams at the rate H.sub.2 /N and are read at the rate H/N of the oscillator. In the other channel, the write rate of the buffer store is forced to the rate H.sub.

Abstract: A receiver comprising a switching circuit responsive to an antenna switching signal for switching between two antennas to produce a received signal, a noise estimating circuit for estimating the quantity of noise from the received signal, and an integrating circuit for integrating the noise to produce a first control signal which serves as the antenna switching signal.

Abstract: A signal selection system is disclosed wherein a plurality of received signals are analyzed to determine their statistical characteristics. These characteristics are compared to a predetermined statistical distribution. The signal that is statistically closest to the statistical characteristics of a known signal is selected for further processing and reception.

Abstract: A signal quality monitor, and a protective relay system using the monitor, which utilizes both AC and DC signals from the receiver agc stage to monitor a plurality of different signal parameters. A signal responsive to the noise in the communication channel which transmits at least one of the protective relay signals used in a protective relay comparison function, is also used in the trip circuits of the associated circuit interrupter to continuously adapt or modify the trip level in response to channel noise.

Abstract: In a space diversity receiver for receiving broadcast signals and having first and second antennas coupled to first and second receiving circuits, respectively, for supplying first and second output signals therefrom to a switching circuit which normally selectively supplies the one of the output signals detected to have a superior or better signal to noise ratio; a judging circuit is provided for comparing the better signal to noise ratio of an output signal with a predetermined value and for producing a stop or inhibiting signal when the signal to noise ratio is lower than the predetermined value, and such inhibiting signal temporarily causes the switching circuit to stop switching between the output signals and to continuously supply one of the output signals.

Abstract: A space diversity receiving system for the central station of a multi-direction time division multiplex communication network having a plurality of satellite stations, and one central station. Each satellite station transmits signals to the central station during an assigned time slot. The central station receives burst signals from the satellite stations. A first receiver has a main antenna. A second receiver has a supplementary antenna. Both receivers include a demodulator coupled to the corresponding antenna and a detector for detecting bit errors in the resulting demodulated signals, and for providing error pulses when appropriate. Each satellite station, needing space diversity, has a counter for competitively counting the error pulses from the receivers. A signal switcher responds to the demodulated signals and the counter for selecting a demodulated signal having a lower bit error rate.

Abstract: A signal switch and combining system for a radio communication system having two receivers (R.sub.A, R.sub.B) includes a comparator operable to determine which of the receiver output signal to noise ratios is the greatest at any instant. There is also a threshold detector arranged to determine when the difference between the two signal to noise ratios exceeds any one or more of a number of predetermined threshold levels. A gating network (GN) responds to the outputs of the comparator and threshold detector (CT) to control a switching and impedance network SZ. This controls the connection of ratio signals from the two receivers (R.sub.A, R.sub.B) to an output load. The network is arranged to connect to the load either one of the two radio signals or a combination of the two signals in one of a number of predetermined ratios. The signal to noise ratios of the two receiver output signals are conveniently indicated by the receiver automatic gain control signals.

Abstract: An FM noise reducing circuit which comprises an operational amplifier for comparing intermediate frequency signal levels and multipath signal levels, and a multiplexer controlled by output signals from the operational amplifier is arranged to carry out attenuation of high frequency components as well as blending of outputs from right and left channels in response to the output signals of the operational amplifier.

Abstract: A bit synchronous switching system is disclosed which has applicability in a space diversity system of digital telecommunications. Two versions of a signal waveform are received at two remote locations from the same signal source. The end user is able always to receive the more intelligible signal by means of instantaneous switching logic. An acquisition and tracking circuit, which can include a delay lock loop, keeps the two signal streams synchronized. One data stream is used as a reference and the time delay of the other is varied so that the time differential between the two streams is tracked out. The system features continuous tracking and does not require any frame synchronization to be superimposed on the data stream.

Abstract: A plurality of horizontally directive antenna sectors are arranged in a configuration to receive signals from remote transmitters over a given angle in the horizontal plane. A scanning system is operative in one of several modes to sequentially couple each sector to a receiver. In its first mode, each sector is sequentially scanned with the peak signal level therefrom being compared to a reference level. If the signal level on any sector exceeds the reference level the scanner activates to its second mode wherein scanning of all sectors continues for a predetermined interval after which the system advances to a selective scanning mode wherein scan is limited to that sector with the largest stored signal level relative to the reference level, and to those sectors adjacent said sector for a predetermined time interval. At the end of this interval, scanning is inhibited and the receiver is coupled to that sector which exhibited the strongest relative signal level during the scanning sequences.

Abstract: A control arrangement for a radio communication system in which mobile users communicate with one another and with a central dispatcher via repeaters. In a first embodiment, the repeater station providing the best quality received signal from a mobile station is caused to re-transmit that signal without the signal traversing lengthy telephone lines to and from a central station. A second embodiment, a repeater station having a local and plural satellite receivers selects the best quality signal among those received by its local receiver and its satellites for re-transmission.

Abstract: A system which selects the highest quality signal from similar signals includes a signal quality detector for each of the signals and a comparator. Each detector provides an output level indicative of the quality of the signal and these signals indicative of the quality of the signal are sequentially provided to a first input of the comparator. The comparator is responsive to signal levels indicating a higher quality signal level than that of a reference level applied to a second input of the comparator for providing that signal out of the selecting system and providing a new reference signal level indicative of the higher quality signal to the second input of the comparator. The system also ranks the input signals according to their quality by repeating the comparison with the successively highest quality signal removed from the comparison.

Abstract: A circuit for providing an indication of the signal/noise ratio of a single frequency signal as received by a receiver has first and second signal paths extending from its input to a comparator contained in the circuit. The first signal path includes a narrow band-pass filter, while the second signal path includes a notch filter. Means are provided in each signal path, for integrating the output of the respective filter. The comparator compares the outputs of the integrating means and outputs when the output of the first signal path integrating means is equal to or greater than the output of the second signal path integrating means. The time which elapses between the receipt of the signal at the input and the beginning of the comparator's output provides an indication of the signal/noise ratio. Such circuits can be used in selecting receivers in multi-receiver arrangements.

Abstract: A noise detector circuit for radio receivers is disclosed. The circuit includes a delay circuit for slightly delaying a received signal. A comparator compares the level of the received signal with the delayed signal to generate a pulse sequence having a number of pulses per unit that is proportional to the level of said noise. A counter counts the number of pulses to detect the level of the noise in the received signal.