374 results about "Signal leakage" patented technology

A method of detecting oscillation in an on-frequency repeater having an RF signal path coupled between an input antenna and an output antenna. In accordance with the present invention, a first RF signal power level within the RF signal path is detected during an un-muted period in which transmission of an output RF signal through the output antenna is enabled. A second RF signal power level within the RF signal path is detected during a mute period in which transmission of an RF signal through the output antenna is disabled. The first and second detected RF signal power levels are then compared, which provides an indication of signal leakage, and thus oscillation.

A transceiver (10) includes an RF transmitter (12) and an RF receiver (14) coupled together through a duplexer (30) or non-filtering multiport device (30′). Either device may leak significant portions (56, 58) of the transmit signal (20) into the receive signal (44), and may significantly distort the transmit signal (20). Distortion is compensated in the transmitter (12) through the use of a linear predistorter (68) that is adjusted in response to an RF feedback signal obtained from the antenna-side of the device. Transmit signal leakage is compensated in the receiver (14) by producing an RF cancellation signal (106) that, when combined with the receive signal (44) at RF at least partially cancels the transmit signal portions (56, 58) leaked into the receive signal (44). Residual leakage signal and intermodulation products thereof may be cancelled digitally.

A high performance single-pole-double-throw (SPDT) Transmitter/Receiver (T/R) FET switch utilizes a plurality of multi-gate FETs in series to realize low insertion loss, low harmonic distortion and high power handling capabilities. The SPDT switch consists of an antenna port, a transmitter branch coupled to a transmitter port through a plurality of multi-gate FETs in series and a receiver branch coupled to a receiver port through a plurality of multi-gate FETs in series. When a high power signal passes from the transmitter port to the antenna port through the transmitter branch, the receiver branch is required to be shut off electrically to prevent the high power signal from leaking to receiver port. This leakage can degrade the isolation of the switch and cause harmonic distortion. Furthermore, the transmitter branch is required to provide a resistance as small as possible to reduce the power loss when it passes through the transmitter branch to the antenna port. In the receiver branch, two of the gate metals in the multi-gate FETs are fabricated with gate sizes several times larger than the others. Furthermore, a heavily doped cap layer is utilized between the gate fingers in a multi-gate FET to reduce the channel resistance of FET, thereby lowering the insertion loss.

A system for detecting and locating a digital TV leakage signal in an HFC network. The system comprises a headend unit and a leakage detector. The headend unit receives the TV signal at the headend for use as a reference signal. The reference signal is sampled at a rate corresponding to a time reference signal, to produce reference signal samples. The reference signal samples and timestamp are transmitted to the leakage detector. The detector receives the digital TV signal from a leakage source, for detection as a leakage signal. The detector includes a cross-correlation processor. The leakage signal is sampled at a rate corresponding to the time reference signal, to produce leakage signal samples. The cross-correlation processor performs a cross-correlation of the reference signal samples with the leakage signal samples to produce a cross-correlation function having a peak, and the TV leakage signal is detected from this peak.

An RFID-tag communication device including (a) an antenna from which a transmission signal is transmitted toward an RFID tag and through which a reply signal transmitted from the RFID tag in response to the transmission signal is received, for radio communication with the RFID tag, (b) a first-cancel-signal output portion operable to generate a digital first cancel signal for suppressing a leakagel signal from a received signal which is received through the antenna and which contains the leakage signal as well as the rely signal, the leakage signal being a part of the transmission signal which is transmitted from the antenna and which is returned to and received by the antenna, (c) a first-cancel-signal control portion operable to control an amplitude and/or a phase of the first cancel signal generated by the first-cancel-signal output portion, (d) a first-cancel-signal D/A converting portion operable to convert the first cancel signal generated by the first-cancel-signal output portion, into an analog signal, (e) a first signal combining portion operable to combine together the analog first cancel signal generated by the first-cancel-signal D/A converting portion, and the received signal, to obtain a first composite signal.

The invention discloses a wireless terminal transceiver of a 60GHz RoF (Radio over Fiber) access system. Secondary subharmonic frequency mixing is adopted, and the frequency of a needed local oscillation signal is reduced in a frequency multiplication frequency mixing way, so that the problem of leakage of the local oscillation signal to an antenna, i.e., a radiofrequency transmitting end in the conventional wireless terminal transceiver scheme is solved, and the circuit modulation performance is improved. Meanwhile, a downlink medium frequency analog signal obtained after secondary subharmonic down-conversion is subjected to downlink medium frequency digital signal processing after ADC (Analog to Digital Conversion) to obtain a needed downlink digital baseband signal; and an uplink digital baseband signal is subjected to uplink medium frequency digital signal processing to obtain an uplink medium frequency digital signal. A series of medium frequency digital signal processing such as odd-even extraction or interpolation, symbol modulation, delay filtering, demodulation or modulation and the like is performed in a digital domain, so that the problem of IQ orthogonal mismatch caused by 90-degree phase change on a local oscillation signal for obtaining two paths of analog signals in an analog frequency domain of the conventional receiver is solved.

The present invention relates generally to communications, and more specifically to a method and apparatus for generating local oscillator signals used for up- and down-conversion of RF (radio frequency) signals. A major problem in the design of modulators and demodulators, if the leakage of local oscillator (LO) signals into the received signal path. The invention presents a number of highly integratable circuits which resolve the LO leakage problem, using regenerative divider circuits acting on oscillator signals which are running at a multiple or fraction of the frequency of the desired LO signal, to generate in-phase (I) and quadrature (Q) mixing signals. Embodiments of these circuits also use harmonic subtraction and polyphase mixers, as well as virtual local oscillator TM (VLO) mixing signals. VLO mixing signals are signal pairs which emulate local oscillator signals by means of complementary mono-tonal and multi-tonal mixing signals.

A system operates to adaptively control the stability of an on-frequency repeater. A unique signature is imposed on RF signals transmitted by the repeater, and RF signals received by the repeater analyzed to detect signal components corresponding to the signature. The signature and the detected signal components are correlated by a micro-controller, which operates in accordance with an Adaptive Control Algorithm to adjust the ERP of RF signals transmitted by the repeater to limit signal leakage and thereby control the stability of the repeater.

The invention discloses a linear and nonlinear comprehensive precoding method and a linear and nonlinear comprehensive precoding device for a multi-user multiple-input multiple-output (MIMO) system. The method comprises the following steps of: acquiring the channel state information of each user by using a transmitter; performing linear precoding processing matrix design according to the novel maximum signal-leakage-noise ratio principle of each user; performing geometric mean resolution on an equivalent channel of each user, and acquiring a corresponding user feed-forward processing matrix; extracting the lower triangular part of an equivalent channel matrix after the transformation of a feed-forward matrix and a linear precoding matrix as a feedback processing matrix for nonlinear precoding; and sequentially performing basic processing such as scrambling, modulation and the like, nonlinear dirty paper coding processing, feed-forward matrix processing and linear precoding matrix processing on a signal, and transmitting the processed signal by using the transmitter. By the method and the device, the comprehensive design of linear precoding and the nonlinear precoding is realized, known interference is eliminated, unknown interference is suppressed, the two shortcomings that the known interference is incompletely eliminated and that the gain of each equivalent channel is unbalanced in the linear precoding based on the maximum signal-leakage-noise ratio principle are overcome, and system performance is improved.

The system and method for radar calibration using antenna leakage is a simplified means of calibrating the channels in amplitude and phase using natural signal leakage between antennas. It utilizes as calibration signal a wideband sinusoidal Frequency Modulated Continuous Wave (FMCW) waveform with a modulation index and modulation frequency chosen to generate spectral components (or discrete signal frequencies) that fall within the receiver Doppler passband of the radar. The calibration signal is radiated out of the transmitting antenna and enters the radar receiver front-end through the transmit-to-receive antenna leakage which occurs naturally. This technique provides a low-complexity (simpler hardware realization) means for achieving a wideband calibration rapidly and is a practical alternative to the conventional calibration approach that relies on generating offset Doppler signals that are coupled into the radar receiver front-end through the use of couplers and cabling within the radar.

A tuner and demodulator performing image rejection in an analog cable television system. Various embodiments disclose a tuner including an analog RF section to generate a complex intermediate frequency digital signal, an image rejection module configured to perform image rejection on the complex intermediate frequency digital signal to generate an enhanced image rejection signal, a signal channel select filter configured to perform digital on-chip filtering on the enhanced image rejection signal to generate a filtered signal, and a demodulator configured to demodulate the filtered signal to generate digital output signals. In some embodiments, the tuner is substantially or fully monolithic. In some embodiments, the tuner performs image rejection by applying an algorithm to estimate a signal correlation between the signal band and the image band of the complex intermediate frequency digital signal, and providing adaptive filtering to reduce signal leakage and image leakage.

The invention relates to the technical field of radar modulation, in particular to a method and a system for eliminating linear frequency modulation continuous wave (LFMCW) radar modulation leakage. The method comprises the steps of: extracting a path of modulation leakage signals by means of an IF signal, fitting a path of modulation leakage signals based on a reference modulation signal, carrying out self-adaptive adjustment on fitting parameters according to correlation operation and fitting error operation of the two paths of modulation leakage signals, and realizing cancellation of modulation signal leakage in a full-digital domain; and carrying out self-adaptive adjustment on fitting parameters such as fitting signal amplitude coefficients and phase positions until the maximum correlation value and the minimal fitting error are obtained, wherein a fitting modulation signal obtained at the moment is approximate to the modulation leakage signals contained in the IF signal, and a target echo signal after eliminating modulation leakage is obtained through subtracting the modulation leakage signals from the IF signal. The method and the system realizes the cancellation of the IF modulation leakage signals in the full-digital domain, simplifies design of the front segment of radar radio frequency, and makes the entire radar system simple and flexible in structure.

A method or apparatus of identifying for repair a signal leak in an HFC network, wherein a base transceiver station in the vicinity of the HFC network transmits a BTS signal over-the-air. The method comprises or apparatus performs the steps of: (a) identifying a location of the signal leak; (b) in the vicinity of the signal leak, detecting the BTS signal; (c) determining a level of the BTS signal; (d) defining a threshold level; (e) with the use of a processor, determining whether the level of the BTS signal meets or exceeds the threshold level; and (f) indicating for repair the signal leak if the level of the BTS signal meets or exceeds the threshold level.

This disclosure describes techniques for reducing adverse effects of TX signal leakage in a full-duplex, wireless communication device. The techniques make use of a notch filter to reject TX signal leakage in a signal processed in the RX path of the wireless communication device. The notch filter may be constructed as a complex notch filter using passive resistor and capacitor components to produce a notch frequency that attenuates TX signal leakage components in a desired signal. The notch filter may be applied to a down-converted, baseband signal produced by a passive mixer.

A radar system using a quadrature signal includes a quadrature push-push oscillator for generating four harmonics with a 90-degree phase difference from each other, and producing two-balanced 2^nd harmonic signals from the harmonics; a first coupler block for radiating one of the 2^nd harmonics through an antenna; a second coupler block for terminating the other 2^nd harmonic to ground; and a power combiner for combining a transmitted signal that is leaked from the first and second coupler blocks with the received signal that is radiated through the antenna. The radar system features an improved receiving sensitivity by offsetting the leakage signals of the sending end. Also, the radar system can be made very small by using a single antenna for transmitting and receiving.

Provided is a wideband active balun circuit based on a differential amplifier. The active balun circuit is configured to compensate for unbalance between two differential signals and can be applied to wideband systems, such as software defined radio (SDR) systems or ultra wideband (UWB) systems. Also, when signal unbalance is caused by changes in process conditions, such as temperature, errors in amplitude and phase between the two differential signals can be finely tuned by adjusting a voltage tuning terminal outside a chip, so that the active balun circuit can simply solve the unbalance between the two differential signals. Furthermore, input transistors that constitute a pair of differential amplifiers are provided in a cascode structure to prevent the occurrence of signal leakage and self-mixture.

The invention relates to an adaptive joint linear precoding method applicable to multi-base station coordination, belonging to the technical field of wireless communication. In the method, the multiple coordinative base stations form a coordination region; each coordinative base station acquires current channel status information from the coordinative base station to each user in the coordinationregion so as to obtain current channel matrixes; the coordinative base stations and signal leakage interference-to-noise ratios at the time of data transmission for the users are subjected to maximumprocessing to obtain anti-multiuser interference precoding matrixes; the equivalent channel matrixes of the users are subjected to singular value decomposition to obtain anti-multithread interferenceprecoding matrixes and decoding matrixes of the users for all corporative base stations; power allocation factors of the users are obtained in accordance with the channel matrixes; and the precoding matrixes of all coordinative base stations in the coordinative region for the jth user are obtained. The method has the advantages of low complicity and less overhead, is easy to realize, can be used to reduce the error rate in the wireless communication and improve transmission performance of communication systems, and particularly is suitable for a coordinative multiple point (CoMP) system of the multi-base station coordination.

Detecting a leak of an OFDM signal from an HFC network, where the HFC network extends over a network area. The OFDM signal includes a first continuous pilot subcarrier having a first harmonic. The first harmonic is defined by a pre-determined first frequency. The method or apparatus comprises the steps of or means for: (a) moving a leakage detector through the network area; (b) tuning the leakage detector to receive the first harmonic of the OFDM signal, based on the pre-determined first frequency of the first harmonic; (c) with the leakage detector, receiving over-the-air, at a received first frequency, the first harmonic of the OFDM signal leaked from the HFC network; and (d) with the leakage detector, detecting the first harmonic received in step (c), whereby the leak of the OFDM signal is detected based on the detection of the first harmonic.

The embodiment of the invention discloses an indoor distributed signal leakage check method and an indoor distributed signal leakage check device. The method comprises the following steps of: obtaining terminal measurement reports (MRs) from a base station, analyzing the MRs and obtaining MR data; filtering invalid MRs; generating neighbor cell pairs according to the MR data obtained after filtration, wherein each neighbor cell pair comprises information measured by a terminal main serving cell and information measured by an indoor distributed cell, the main serving cell is an outdoor macrocell and the indoor distributed cell is a neighbor cell of the outdoor macrocell; and finally judging whether signal leakage exists in the indoor distributed cell or not according to the information recorded by the neighbor cell pairs, computing the direction of the signal leakage of the indoor distributed cell to simply and accurately know the cell in which indoor distributed signal leakage exists in advance, and making an adjustment to prevent influence on outdoor subscribers.