Abstract: An integrated adaptive spatial-temporal system and method for controlling narrowband and wideband sources of interference. The system includes an N element antenna array which receives a spread spectrum signal and interference signals, each element receiving a different phase shifted version of the spread spectrum and interference signals; a spatial filter including an antenna pattern former responsive to the antenna array which combines the phase shifted spread spectrum and interference signals according to controlling weights to null N-1 of the interference signal; an adaptive narrow band, e.g., temporal filter, responsive to the spatial filter for filtering any remaining narrowband interference signals from the combined signal; and feedback subsystem responsive to the narrow band filter for adjusting the controlling weights of the antenna pattern former until the operation of the spatial filter is optimized and nulls wideband interference signals before narrowband interference signals.

Abstract: An apparatus and methods for tracking a power level of a signal received at a base station of a code division multiple access (CDMA) digital cellular communication system. The apparatus comprises a storage unit for storing a first table comprising automatic gain control voltages corresponding to a series of received signal levels and a second table comprising variable attenuation control voltages corresponding to the automatic gain control voltages.

Abstract: An AGC method and apparatus is provided for a receiver to control the signal power of a received RF signal over a wide dynamic range and significantly reduce the ADC clipping time to a level appropriate for cellular communications. The AGC apparatus comprises an ADC (analog-to-digital converter) for generating digital samples of a received signal, a controller for providing a receiver gain setting based on the digital samples generated and an actuator for applying the receiver gain setting. The controller compares digital samples generated by the ADC to a first predetermined reference level, accumulates an error signal, calculates an attenuation adjustment based on the accumulated error signal and sums the attenuation adjustment with a previously calculated receiver gain setting for providing the actuator with an updated receiver gain setting which is applied therein.

Abstract: An antenna performance monitor comprises an antenna sensor for coupling to n antenna radiating a radio frequency signal. The antenna sensor generates signals Vm and Im representative of the antenna input voltage and current. An A/D converter is coupled to the antenna sensor for digitizing signals Vm and Im. A data processor is coupled to the A/D converter for generating outputs representative of impedance magnitude and phase angle of the antenna substantially concurrently with changes in frequency of the radio frequency signal.

Abstract: An apparatus for automatic gain control (AGC) of a digital QPSK demodulator is disclosed. The apparatus for automatic gain control of a QPSK demodulator comprising a variable gain amplifier for controlling an amplification gain of a QPSK-demodulated signal by a predetermined gain control signal comprises a signal magnitude estimator for estimating the magnitude of I and Q-channel signals in the QPSK demodulator by using the equation S.sub.mag =MAX.vertline.I.vertline.,.vertline.Q.vertline.)+1/2MIN(.vertline.I.vertli ne.,.vertline.Q.vertline.), and a control signal generator for generating a gain control signal according to the magnitude of the input signal outputted from the signal magnitude estimator, and outputting the gain control signal to a variable gain amplifier.

Abstract: An apparatus for performance improvement of a digital wireless receiver comprises a processing circuit for processing a plurality of received signals and providing a processed signal, wherein each of the plurality of received signals is weighted and combined to provide the processed signal; and a generation circuit for computing a composite reference signal for use in weight generation. The composite reference signal is computed as a weighted average of a coherent reference signal value and a constant-modulus reference signal value.

Abstract: Transmission mode selection is enabled, so communication reliability, transmission speed, and equipment utilization efficiency are all high. A first transmission system whereby spectrum spreading is accomplished with a spread code 1 and data is transmitted, and a second transmission system whereby data is transmitted with a spread code 2, are provided. In high-reliability transmission mode, identical data from a data buffer is transmitted through both the first and second transmission systems to achieve space diversity. In high-speed mode, data divided by a data division circuit is transmitted simultaneously through the first and second transmission systems, making possible efficient data transfer. Control information insertion circuits append transmission mode data to the transmitted data.

Abstract: A receiving system comprises a plurality of receiving branches 1, 2, - - - n each including an adaptive antenna. A variable gain controlled amplifier 31, 32, - - - 3n is provided in each receiving branch 1,2, - - - n for setting an amplification factor of a receiving signal in each receiving branch. Automatic gain control unit 7 inputs receiving signals from the plural receiving branches 1,2, - - - and n at predetermined sampling intervals and controls the amplification factors of the variable gain controlled amplifiers 31, 32, - - - 3n. An adaptive antenna processing unit 8 performs an adaptive antenna processing based on the receiving signals sent from the plural receiving branches 1,2, - - - n. A timing control device 71, 72 or 73 allows the automatic gain control unit 7 to renew the amplification factor of each variable gain controlled amplifier 31, 32, - - - 3n in response to each elapse of a predetermined interval longer than the sampling interval of the automatic gain control unit 7.

Abstract: In a base station transmitter/receiver of a cellular system, a plurality of antennas are oriented in each sector and radiate radio transmission signals and receive radio reception signals to produce received signals. A signal processing circuit is connected to the antennas to process the received signals into output reception signal and to process input transmission signal into the radio transmission signals in response to the received signal. Thus, the signal processing circuit serves to vary the directivities of the antennas in each sector and to thereby control a composite directivity formed by the varied directivities.

Abstract: There is provided a method of rapid Received Signal Strength Indication (RSSI) of a time-dispersed signal having echoes (where the time dispersal represents a significant fraction or more of the transmitted symbol interval). It comprises a sliding correlation of a received signal against a known sequence or via channel sounding to obtain the time-dispersal function of the communications channel upon which the signal is transmitted and a summation of the squares of the quadrature components of the energies at relative maxima of the correlations (correlation peaks determined with reference to a threshold level) to integrate the energy defined by the correlation function to determine the energy present among the time-dispersed echoes utilizing the time-dispersal function.

Abstract: A rake-type CDMA base station receiver equipment, including a plurality of correlators each having a received signal as its input, a plurality of diversity combiners for respective receiver branches, and a measurer for measuring the quality of the received signal. To reduce the number of correlators and diversity combiners, the receiver equipment further includes switches for switching the correlators to the different combiners, and controllers for controlling the switches on the basis of data sent from the measurer for measuring the quality of the received signal or on the basis of the capacity loading of the base station receiver equipment.

Abstract: Process and apparatus for extracting a useful signal emitted by an implanted active medical device in the presence of parasitic signals. This device includes a plurality of signal receivers located at distinct points. The signal receivers are sensitive to the magnetic component of the electromagnetic signals and separated from each other by a distance that is negligible as compared to the wavelength of the electromagnetic signal. A plurality of amplifiers are provided with one amplifier being associated with each signal receiver and each amplifier having an adjustable gain. The amplified signals are summed by an adder, and the summed signal (V(t)) is evaluated using a magnitude (.vertline.V.vertline.) representative of the level of the summed signal.

Abstract: A method and an apparatus for adaptively canceling an interference signal in any D/U ratio is disclosed. The method and apparatus are directed to being implemented in a two-branch space-diversity system having an array of first and second receivers assigned to a first diversity branch and a second diversity branch, respectively. The feature resides in the ratiow.sub.2 /w.sub.1 =(m.sub.1 g.sub.1 m.sub.2 g.sub.2 *) / (m.sub.2.sup.2 g.sub.2 g.sub.2 *),wherein w.sub.1 and w.sub.2 are the weights by which a first branch signal and a second branch signal, respectively, are to be multiplied, m.sub.1 and m.sub.2 are the gains of the first and second receivers, and g.sub.1 and g.sub.2 are the transmission coefficients of the interference signals received by the first and second receiver, respectively.

Abstract: In an automatic gain control circuit which has a variable gain amplifier 30 for amplifying an input TDM reception signal 160 in accordance with a controllable gain, an analog-to-digital converter 40 for converting an amplified TDM reception signal 170 into a digital signal 180, and control section 50 for determining an optimized value of the controllable gain in response to the digital signal 180 so as to supply the variable gain amplifier 30 with the optimized value of the controllable gain, the optimized value of the controllable gain is determined by the use of a signal of the time slot S(-1) immediately before the predetermined time slot S(0) when receiving the input TDM reception signal 160.

Abstract: In a diversity transmission system the problem arises that almost no improvement can be obtained when the signals to be received show frequency selective fading within the band width of the signal to be transmitted. To solve this problem the signal to be received is separated by filter banks into a number of sub-band signals. Corresponding sub-band signals of different filter banks are combined by the combiners into combined sub-band signals. These combined sub-band signals are combined to a broad band signal by a final combiner.

Abstract: In a combining circuit comprising first and second frequency converting sections (20a, 20b) for frequency converting first and second received signals from two independent antennas (10a, 10b) under the control of a control circuit (30) into first and second frequency-converted signals, first and second preliminary amplifying sections (60a, 60b) preliminarily amplify the first and the second frequency-converted signals under the control of the control circuit (30) to produce first and second preliminary amplified signals having first and second output levels, respectively. The first and the second preliminary amplified signals have first and second noise power levels, respectively, which are equal to each other. First and second main amplifying sections (40a, 40b) mainly amplify the first and the second preliminary amplified signals by first and second amplification degrees in proportional to the first and the second output levels, respectively.

Abstract: A radio link for a digital radio transmission system having spatial and/or angular diversity is optimized in real time by first varying the relative phase .phi. between the two channels to locate an absolute minimum of the analog bit error rate function BER.sub.n (.phi.) with both channels having the same nominal attenuation level, and then by unbalancing the relative attenuation level T of the two channels in order to optimize the dispersion Ban.sub.n (T) of the recombined data spectrum while holding the relative phase at its previously optimized value.

Abstract: Improved apparatus for a radio communication network having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceiver units which communicate with one or two host computers for storage and manipulation of data collected by bar code scanners or other collection means associated with the mobile transceiver units. The radio network is adaptive in that in order to compensate for the wide range of operating conditions a set of variable network parameters are exchanged between transceivers in the network. These parameters define optimized communication on the network under current network conditions. Examples of such parameters include: the length and frequency of the spreading code in direct-sequence spread spectrum communications; the hop frame length, coding, and interleaving in frequency-hopping spread spectrum communications; the method of source encoding used; and the data packet size in a network using data segmentation.

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: In a digital radio communications system, a transmit signal is delayed and sent on a first diversity channel and a nondelayed version of the signal sent on a second diversity channel. At the receiving site, first and second diversity channel signals are recovered and normalized into first and second constant-amplitude signals. Predominant components of the constant-amplitude signals are phase-and-amplitude aligned with each other by feedback loops including phase-and-amplitude alignment circuits, an adder and an AGC amplifier. The output of the AGC amplifier or the output of the subtracter is selected and applied to a matched filter to which a decision feedback equalizer is coupled.

Abstract: A receiver module 140 controls the amplitude of a random burst signal 200 in a TDMA system. A random burst signal 200 presence detector 330 detects when the random burst signal 200 has arrived during a timeslot reserved for the random access burst 200. After detection, a control processor monitors the signal strength or amplitude of the random access burst 200 for a predetermined time period, determines the amount of AGC attenuation required, and inserts the required AGC attenuation to control the amplitude of the random access burst 200 for the duration of the timeslot.

Abstract: An interference cancellation circuit which can remove the interference signal caused by other systems and contained in received signals. The interference signal can be cancelled even if the interference signal is not directly obtained or plural interference signals exist, or the interference signal is a wide band signal or raster interference simply by receiving two signals which have passed through different transmission paths, combining the main signals contained in each of the received signals in a manner to offset each other to the extract interference signal, and removing the interference signal component from the received signal based on the expected interference signal.

Abstract: A method and appartus for diversity reception in a communication system wherein at least a dual branch receiver is provided with a stored replica of expected reference information that is correlated with the received time-dispersed signals to obtain an estimate of the transmission channel's impulse response as seen by each branch, and determine, among other things, phase error between the branch local oscillators and the time-dispersed signals. Matched filters are constructed which then coherently align the time-dispersed signals from each branch with that branch's local oscillator, also constituting the first part of the equalization. The diversity processing stage may perform bit by bit selection on the re-aligned signals, maximal ratio combining of the re-aligned signals, or equal gain combining of the re-aligned signals, following each by a sequence estimation which uses similarly selected or combined channel distortion compensation parameters to complete the equalization process on the new signal.

Abstract: Undesired signals detected by a main antenna are cancelled by corresponding interference cancelling signals. The output of the main antenna is frequency converted to IF region and decomposed into first and second main baseband components. Decision circuits are provided for making a decision on whether each of the first and second main baseband components exceeds each of multiple thresholds and produces multibit codes as well as error signals. Auxiliary antennas respectively detect the undesired signals and feed auxiliary frequency converters for translating the frequency of the respective outputs of the auxiliary antennas to the intermediate frequency. Auxiliary quadrature demodulators are provided for respectively decomposing the output of each auxiliary frequency converter into first and second auxiliary baseband components. Correlations are detected between the first auxiliary baseband components and the first error signal and between the second auxiliary baseband component and the second error signal.

Abstract: The Troposcatter Modem Receiver includes a combiner, demodulator, baseband filter, a complex coefficient forward equalizer, a detector and a feedback circuit. The combiner is a linear maximal-ratio combiner and receives a plurality of input signals at an intermediate frequency and generates a combined output signal for presentation to the demodulator. The demodulator produces a demodulated signal which is filtered by the baseband filter prior to being presented to a first input of the equalizer. The output of the equalizer is forwarded to the detector which produces an output signal. The signal is fed back by way of the feedback circuit to a second input of the equalizer to modify the output signal.

Abstract: Diversity combiners for use in satellite and other communication systems. Such combiners are able to accommodate fast and dramatic signal fades and doppler shifts inherent in satellite communications by employing differential and common mode automatic phase control and differential and common mode signal weighting techniques. Phase control takes place in these combiners after signal weighting to decrease differential loop phase detector gradients and noise bandwidth as a function of signal-to-noise imbalance of the channels. An acquisition circuit is provided to deactivate the differential phase control loop when either signal falls below a predetermined level. During times when the faded signal reemerges, the combiner establishes optimal combining with minimum phase discontinuities on the output or phase lock reacquisition disturbances.

Abstract: A communication transmission system for electromagnetic waves comprising a transmitter, transmitting and receiving antenna with a radio link hop therebetween and a receiver having an associated diversity receiver. When there is no access to energy supply, network energy is supplied from batteries, solar systems and other power supplies which have limited power and are expensive. So as to provide energy saving operation of a system, a digital system is created and the invention provides a fade detector in the receiver for fast recognition of fading and which produces signals corresponding to the weighted switching thresholds that are derived for the connection of the diversity receiver which had previously been disconnected so as to reduce power consumption and for setting by reducing or increasing the transmission power or for the IF through connecting by way of a plurality of radio link hops or for the compensation or cancellation thereof.

Abstract: An interference cancellation system at a receiver side for digital radio system has a first quadrature phase detector for demodulating the main signal. A second quadrature phase detector (or a phase detector) is supplied with the same reference carrier and clock signal as that of the first quadrature phase detector, for phase detecting an interference signal. A decision circuit is coupled with the first quadrature phase detector to provide a baseband signal. An error signal detector provides a difference between a decision level of a digital signal and an input of the decision circuit due to the interference signal. A correlation device provides a correlation signal between an error signal and a phase detected interference signal. A control device provides a compensation signal which has the same amplitude and anti-phase as those of the interference component included in the main signal according to the correlation signal.

Abstract: An adaptive power equalizer circuit for use in a spread spectrum receiver system which includes an antenna system 12, 13 and a receiver 11, the circuit comprising adaptive power inversion circuitry 15 for producing a first signal having a minimized power level and a second signal having a substantially higher power level than that of the first signal. Such signals are supplied to a power equalizer circuitry 16 which equalizes the power levels thereof, such equalized power level signals then being combined in a suitable combiner circuit 30 for producing an output receiver output signal for the receiver 11.