Abstract: Self-interference cancellation in two-way relayed communications is improved by creating models of upconverter and downconverter imperfections and then compensating for those imperfections before self interference cancellation processing. The model includes compensation for phase offset, for amplitude imbalance and for leakage in the mixers.

Abstract: A novel and useful apparatus for and method of I/Q gain mismatch compensation for use in a communications receiver. The invention is operative to calculate an estimate of the I/Q gain mismatch. Each input sample is subsequently multiplied by the inverse of the estimate to generate compensated samples. The training sequence portion of the uncompensated input samples is used to generate the I/Q gain mismatch estimate. In accordance with the present invention, the H matrix used in calculating the gain mismatch estimate is pre-calculated for several channel lengths and stored in memory. An estimate of the channel is generated which provides the channel length and the location in the input sample buffer of the first training sequence sample to be used in calculating the gain mismatch estimate. The channel length is used to determine the number of training sequence samples to be used and to select one of the previously calculated H matrices.

Abstract: Methods, apparatuses and systems are provided for use in a wireless routing network. One apparatus, for example, includes an adaptive antenna that is configurable to receive a transmission signal from a transmitter and in response transmit corresponding outgoing multi-beam electromagnetic signals exhibiting a plurality of selectively placed transmission peaks and transmission nulls within a far field region of a coverage area. The adaptive antenna may also be configured to selectively receive at least one incoming electromagnetic signal directed through the coverage area. The adaptive antenna includes at least one antenna array and logic. The antenna array has a plurality of antenna elements. The logic is operatively coupled to the antenna array and configured to selectively control the placement of the transmission peaks and transmission nulls within the outgoing multi-beam electromagnetic signals.

Abstract: A novel and useful apparatus for and method of DC offset compensation for use in a communications receiver. The invention is operative to calculate an estimate of the DC offset which is subsequently subtracted from each input sample to generate compensated samples. The training sequence portion of the uncompensated input samples is used to generate an estimate of the DC offset. The vector used in calculating the offset estimate is pre-calculated for several channel lengths and stored in memory. An estimate of the channel is generated which provides the channel length and the location in the input sample buffer of the first training sequence sample to be used in calculating the offset estimate. The channel length is used to determine the number of training sequence samples to be used and to select one of the previously calculated vectors.

Abstract: A method and apparatus for mitigating co-channel and inter-channel interference in an antenna array system. It is determined by a base station or other transmitter employing an antenna array that transmission of at least a first downlink signal will generate a co-channel or inter-channel ghost signal at at least one location that may be susceptible to such ghost signal (e.g., as interference). As such, a weight to be applied to the at least first downlink signal is adjusted to reduce mitigate the undesirable effect of the ghost signal at the location before transmission of the at least first downlink signal.

Abstract: An RF circuit configured to inteface a balanced port (1, 2, 11, 12) with an unbalanced port (4, 14) by emulating the function of a balun. Reactive components (20, 30, 120, 130) in both branches of a balanced circuit form two resonant circuits by resonating with parasitic reactance. At a predetermined operating centre frequency, one of the two resonant circuits is above resonance and the other is below resonance, resulting in a 180° phase difference between the signals delivered by the two branches. When used to interface an unbalanced signal source (10) to a balanced load (40), the input impedance may be set to a real value matching the output impedance of the signal source by selection of the reactive component (20, 30) values.

Abstract: The present invention relates to a balanced circuit arrangement and methods for linearizing and calibrating such a circuit arrangement, wherein linearization is obtained by introducing a load imbalance between the output branches of the balanced circuit arrangement. Thus, a controllable extraneous imbalance is created between the output loads of the balanced circuit arrangement to thereby obtain a linearization by means of even-order non-linearity.

Abstract: Multi-channel self-interference cancellation is provided in relayed electromagnetic communication between a first device and one or more other devices on one or more shared frequency channels. Specifically, near signals are generated at the first device and transmitted to a relay station. A composite signal is received at the first device from the relay station containing relayed versions of the near signals and relayed versions of remote signals transmitted from the one or more other devices, the composite signal having frequency channels including the one or more shared frequency channels, each shared frequency channel occupied by at least one of the relayed near signals and one of the relayed remote signals. One or more cancellation signals are selectively generated, each having a frequency band corresponding to one of the shared frequency channels. The cancellation signals are combined with the composite signal to produce a desired signal representing the relayed remote signals.

Abstract: A duplexer structure for allowing an RF transmitter and an RF receiver to share a common antenna includes impedance matching circuitry to match the receiver input impedance to the antenna impedance during a receive operation and impedance transformation circuitry to transform the antenna impedance to a lower impedance at the receiver input terminals during a transmit operation. The impedance matching circuitry and the impedance transformation circuitry of the duplexer share one or more passive components, thus reducing the overall number of components required to implement the duplexer. This reduction in component count reduces the amount of chip area required to implement the duplexer and increases the ease with which the RF transceiver is integrated onto a semiconductor chip. In one embodiment, the duplexer uses a differential topology to provide common mode noise rejection and even harmonic distortion cancellation within a transceiver.

Abstract: Disclosed is an apparatus for commonly using an antenna for a call signal and a television (TV) broadcasting signal in a radio communication terminal including an antenna, a phone duplexer, a TV tuner, an LC parallel circuit, connected between the antenna and the phone duplexer, for forming an LC resonance circuit for a call signal frequency band, an LC series circuit connected to a connected point of the LC parallel circuit and the antenna and to a DC power supply terminal, a stub for impedance matching one terminal of which is connected between a capacitor and an inductor of the LC series circuit and the other terminal of which is connected to the TV tuner, and a path providing section for providing a path between a connected point of the stub and the TV tuner and a ground terminal in accordance with a switching control signal provided according to a TV or call operating mode.

Abstract: A direct conversion receiver is disclosed, in which a DC offset is estimated in two stages. A coarse DC estimation is performed, and the estimate is removed from the received sequence. Then, a coarse synchronization is performed in order to estimate the synchronization position within the burst. Subsequently, a coarse channel estimation and a finer DC estimation are performed simultaneously, and the refined DC estimate is removed. Finally, a refined synchronization and channel estimation are performed, and the refined estimate of the channel is fed to an equaliser, which acts on the received signal, after removal of the refined estimate of the DC component.

Abstract: An RF mixer circuit having reduced intermodulation products includes a cascode transconductance amplifier including a first transistor having a control electrode connected to receive an input signal and serially connected with a second transistor having a control electrode connected to receive a bias potential. A balanced mixer is coupled to the second transistor by a first inductive element for receiving an amplified input signal current, and receiving a local oscillator signal and producing an output signal with an intermediate frequency related to the frequencies of the amplifier input signal and the local oscillator. A feedback circuit is provided from the second transistor to the control electrode of the first transistor including a resistor serially connected with a capacitor, whereby the feedback circuit compensates for signal phase shift by the inductive element.

Abstract: The present invention provides a method and system for estimating common amplitude and phase errors of a multiple channel wireless system. The multiple channel wireless system includes a plurality of transmission channels formed between a plurality of transmission antennas and a plurality of receiver antennas. The method includes estimating transmission channel elements between each transmission antenna and receiver antenna pair of the multiple channel wireless system. Calibration symbols are transmitted from each transmit antenna. Signals are received that correspond to the calibration symbols having traveled through the transmission channels. Received calibration symbols are estimated based upon spatial processing of the received signals and the estimated transmission channel elements. Common amplitude and phase errors are estimated for each transmit and receive antenna pair by comparing the transmitted calibration symbols with the received calibration symbols.

Abstract: A system and a method for wireless communications includes an antenna, a GPS circuit with a GPS matching circuit that is coupled to the antenna, a communications circuit with a communications matching circuit that is coupled to the antenna. The communications matching circuit is adapted to switch between different impedances, for example, to match the communications circuit with the antenna for a particular communications band or to isolate the communications circuit from the antenna. The communications matching circuit or the GPS matching circuit may be actively adapted.

Abstract: In a radio transceiver operating in a time division duplex system, a cancellation use transmission signal which is reverse in phase and equal in amplitude to a leakage transmission signal from an antenna in the signal transmission is supplied to an input port of the receiving amplifier of a receiver connected to an antenna system applied in common to the signal transmission. The transmission signal is fed via a circulator, which separates a transmission and reception path, to the antenna. The leakage transmission signal from the antenna is inputted via the circulator to the receiving amplifier. The cancellation use transmission signal is fed to the receiving amplifier via a second circulator which distributes the transmission signal and cancellation use signal disposed at an output side of the transmitting amplifier.

Abstract: A radio communications transceiver which operates to transmit radio signals via a transmit antenna and receive radio signals via a receive antenna, wherein said transmit and receive antennas are disposed to provide at least a substantial amount of radio signal isolation therebetween. The radio communications transceiver further includes a cancellation device comprising a first coupler coupled to the transmit antenna and arranged to extract a sample of the transmit signal, a second coupler coupled to the receiver antenna and arranged to extract a sample of the received signal, a correlator fed on first and second inputs with the transmit and the received signal samples respectively, the correlator operating to generate an error signal representative of a correlation of the transmit and received radio signals, which error signal is fed to a modulator which operates to modulate the transmit signal sample, consequent upon the error signal.

Abstract: A communications device transmitting and receiving RF signals having an antenna including an antenna core, a plurality of first polarized antenna elements wound about the antenna core in a first direction, a plurality of second polarized antenna elements wound about the antenna core in a second direction, and a plurality of RF PIN diodes inserted in the plurality of first and second polarized antenna elements at the points where the plurality of first polarized antenna elements and the second polarized antenna elements overlap. A communications device and method for decreasing fading of a call due to multipath by switching between polarizations of the antenna when the power level of the RF signals drops below a predetermined threshold. A communications device and method for decreasing fading of a call by averaging power levels on both polarizations of the antenna.

Abstract: Connector switch apparatus which can provide either a cable or satellite television signal or a ghost-free off-air television signal. The apparatus obtains the cable or satellite television signal from a cable or satellite tuner, which can be included in the apparatus; and includes a television tuning device for producing a ghost-free off-air television signal, and a switch which provides either of those signals. The television tuning device employs use of antenna directionality control and ghost cancellation to produce a ghost-free off-air television signal. In particular, the television tuning device obtains an off-air television signal from a antenna, which may or may not be included therein, whose directionality can be changed to change reception quality of a received off-air television signal; and includes a baseband ghost cancellation unit which can perform baseband ghost cancellation.

Abstract: A balanced differential radio receiver (100) has an antenna (64) operative for receiving a modulated signal. A first pair of mixers (110, 112) each having an input that receives an output (106, 108) of the antenna (64) and each of the first pair of mixers (110, 112) having an output (118, 120). A second pair of mixers (114, 116) each having an input that receives an inverse output (108, 106) of the antenna (64). A resistive adding circuit (122, 124) having a pair of inputs (118, 120). The inputs (118, 120) coupled to the output of the first pair of mixers (110, 112).

Abstract: An RF antenna and an associated receiver are proximately located in an integrated antenna/receiver unit thereby eliminating the need for baluns and inter-component cabling characteristic of prior designs. Integration of the receiver with the antenna provides for improved sensitivity as the need for utilizing signal dissipating and noise introducing cables and baluns to transmit the signal received by the antenna to the receiver is eliminated. Direct coupling of the antenna and receiver on a single gallium arsenide integrated circuit maintains balanced impedance from the antenna to the receiver.

Abstract: Television tuning systems and methods employing use of ghost cancellation and antenna directionality control to produce a ghost-free television signal. The invention employs use of a antenna whose directionality can be changed to change reception quality of a received television signal, and a baseband ghost cancellation unit which can perform baseband ghost cancellation. In a first embodiment of the invention, the directionality of the antenna is changed so that a television signal of sufficient reception quality is received from which a ghost-free television signal can be produced therefrom by the baseband ghost cancellation unit. A second embodiment of the invention further employs use of a tuner, and involves controlling the directionality of the antenna and the tuning frequency of the tuner so that a tuned television signal is produced which is properly tuned and of sufficient quality that a properly tuned ghost-free television signal can be produced therefrom by the baseband ghost cancellation unit.

Abstract: Electronically adaptable polarization antenna feed apparatus for receiving any sense of linear polarization or for receiving either sense of circular polarization. The circuit makes use of variable gain amplifiers and/or variable attenuators in each of two orthogonally polarized paths. The signal to noise ratio of a desired polarization sense is maximized by adjusting the amplitude or gain in each path to a desired ratio. If desired, polarization components from the two probes may be combined so that orthogonal polarization senses from two frequency reuse signals be used simultaneously. The apparatus may be used with linearly polarized signals and with circularly polarized signals.

Abstract: A spatial combiner for connection to a receiver used in conjunction with a lurality of direction-sensitive antennas for receiving a spread-spectrum communication signal in the presence of interference includes a steering network, a plurality of normalizers, and a plurality of combiners. The steering network combines N inputs from N antennas and produces outputs J.sub.1, J.sub.2, . . . , J.sub.M, with M being a multiple of K and K a positive integer such that each M output is a weighted sum of N inputs from the antennas. The normalizers receive and normalize the M outputs to unit energy and produce normalized outputs J .sub.1, J .sub.2, . . . , J .sub.M. The combiners receive normalized outputs and sum the first K outputs to produce output C.sub.1, sum the next K outputs to produce output C.sub.2, and continuing summing outputs in the same manner until summing the last K outputs occurs to produce output C.sub.M/K. The outputs C.sub.1 through C.sub.

Abstract: Circuitry and concomitant methodology for demodulating Direct-Sequence, Spread-Spectrum Code-Division Multiple-Access (DS/SS CDMA) channel signal using multiple samples per transmitted symbol and a minimum mean squared error criterion to suppress interference. In one embodiment, a bank of cyclically shifted filters determined with reference to the conventional matched filter for CDMA is used to demodulate the channel signal. In another embodiment, a bank of sub-filters determined with reference to the conventional matched filter for CDMA is employed to demodulate the channel signal. In yet another embodiment, the output of a conventional matched filter is oversampled to demodulate the channel signal. Each embodiment utilizes a set of adaptive coefficients selected to minimize the mean square error between the transmitted symbol and detected symbol.

Abstract: An industrial measuring apparatus comprises first and second sensors having identical measuring characteristics and arranged close to each other and also close to a common subject of measurement, for measuring the same parameter, a transmitting unit having an adder and a first subtracter respectively connected the sensors through amplifiers, and a receiving unit having a second subtracter connected to the adder and the first subtracter through two transmission lines and constituting a noise canceling device in cooperation with the adder and the first subtracter. The second subtracter produces a receiving signal by subtracting the output of the subtracter representing the difference between the outputs of the first and second sensors from the output of the adder representing the sum of the outputs of the two sensors.

Abstract: A spread-spectrum noise canceller is provided for cancelling user code noise from a spread-spectrum communication channel. The spread-spectrum noise canceller including a receiver for receiving a spread-spectrum signal including a first and at least a second signal as well as a noise canceller operatively coupled to the receiver for reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal.In addition a method is provided which cancels user code noise from a spread-spectrum communication channel. The method includes for receiving a spread-spectrum signal including a first and at least a second signal and subsequently reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal.

Abstract: Sidelobe jamming in dual diversity troposcatter link receivers is effectively suppressed by providing an auxilliary low power antenna, the output of which is differenced from the high power main antenna signals prior to processing in the receivers's dual diversity demodulator. The auxilliary antenna power is substantially equal to the sidelobe power of the main antennas. The auxilliary antenna receives jamming power that is comparable to the jamming power received by the main antennas. However, it receives much lower desired signal power. Differencing of the signals therefore, cancels jamming power with minimal effect on the desired signals.

Abstract: In a receiving station having an adaptive receiving antenna, a phasing system comprises a plurality of reception paths receiving telecommunications signals derived from the same useful signal combined in transmission with a disturbing signal having a frequency band outside the frequency band of the useful signal, via a plurality of primary sources of the receiving antenna. The phasing system includes a narrowband filtering circuit for filtering the overall telecommunications signal in one of the reception paths to derive a reference signal undisturbed by the disturbing signal and solely dependent on the useful signal. In phasing circuits respectively assigned to the reception paths, the useful signal alone is set to a phase as close as possible to the phase of the reference signal in order to obtain, after signal summing at outputs of the phasing circuits, a maximum power using signal mixed with an attenuated scrambling 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.

Abstract: A system for adjusting the antenna matching network of a radio system in the presence of an interfering signal in the matching network being adjusted comprises a loop from which the interfering signal is cancelled by an adaptive interference cancellation (AIC) system. The AIC system receives an interference sensor signal having the frequency of the interfering signal. Means responsive to the interference sensor signal and phase and amplitude control signals provides a modified interference sensor signal having a phase and amplitude determined by the control signals. This modified interference sensor signal is combined with a mismatch signal which is derived from the signal in the matching network to produce a modified mismatch signal.

Abstract: The present invention preprocesses serial data sample sets so that truly ependent samples are available for further processing. Samples to be analyzed are delayed and compared in order to isolate both components that are correlated between samples, and components that are uncorrelated between samples. These components provide independent information relating the samples which are used to modify or preprocess incoming data.

Abstract: An improved technique for eliminating interference in serial data samples ving signal components which are desired to be removed before being further processed. A limited-iterative technique is employed to reduce components of the incoming data samples which are correlated among prior data samples.

Abstract: A multichannel communications receiver, e.g. a CATV converter, includes a switched filter for reducing third order intermodulation distortion by limiting the number of channels processed by the receiver. In a preferred embodiment, the filter is switchable between a highpass and a lowpass configuration by a control signal supplied to two switching diodes. The input and output of the filter are coupled by a mutual inductance which partially compensates for the effect of parasitic inductance at higher frequencies.

Abstract: In a reception system which includes a receiver having a plurality of inter-connected stages and a demodulator, and where there appears at an input of the receiver a desired signal which occupies substantially a predetermined bandwidth, and at least one undesired signal which occupies a bandwidth different from, though partially overlapping the predetermined bandwidth, the improvement includes a signal selector coupled to receiver terminals upstream of the receiver demodulator for normally continuously selecting one of the signals appearing across the receiver terminals, a gain-controlled feedback stage connected with one input thereof to an output of the signal selector for negatively feeding back to the receiver terminals one of the signals substantially 180.degree.

Abstract: A frequency conversion circuit in which effects of odd order terms in the input and output characteristics of the active elements of the circuit, which otherwise would produce IM interference, are eliminated. A superposition signal composed of two signals of different frequencies is applied, in opposite phases, to control inputs of a differential pair of transistors. A common load is coupled to the differential pair with the odd order terms being cancelled at the common connection point of the differential pair. The common load is preferably a resonant circuit.

Abstract: Apparatus for cancelling undesired signals for a radient energy receiver having first and second antennas which are spaced a distance apart and including a phase compensation circuit connected to one of the antennas and a variable phase shift circuit connected to the second antenna with the variable phase shift circuit comprising a plurality of series connected inductors wherein adjacent inductors are magnetically coupled together and a plurality of voltage variable capacitors with adjacent ones of the voltage variable capacitors connected between ground and the junction points between adjacent ones of the series connected inductors and adding means connected to the outputs of the phase compensation circuit and the variable phase shift circuit and means for supplying a variable DC voltage to the variable voltage capacitors to control their capacitance.

Abstract: A radio receiver comprises an antenna circuit represented by an equivalent circuit consisting of an antenna electromotive force, an antenna capacitance in series with said electromotive force and a cable capacitance in parallel with them, a negative capacitance circuit connected to the antenna circuit for at least partially cancelling the antenna capacitance and the cable capacitance and a tuning circuit for receiving the output of the antenna circuit. The negative capacitance circuit, composed of a capacitor, transistors and the like, improves the S/N ratio.