158results about "Automatic frequency control details" patented technology

An AFC control apparatus in mobile communication equipment includes a depreading unit, first integrator, and control section. A despreading section despreads the reception signal. The first integrator integrates despread outputs obtained by despreading, of pilot symbols contained in a pilot channel of the reception signal, N (N is a number of 2 or more) consecutive first symbols and N second symbols succeeding the N first symbols, and generates first and second integral outputs. The control section detects any phase shift amount between the first and second integral outputs and controls the frequency of the local signal in accordance with the detected phase shift amount. An AFC control method and mobile communication equipment having the above apparatus and method are also disclosed.

An AFC circuit for controlling an oscillation frequency of a local oscillator is disclosed. An f / V converter converts a frequency of an FSK signal to a received signal voltage varying depending on the frequency of the FSK signal. A window generator generates a voltage window including a reference voltage corresponding to a center frequency of the FSK signal. The oscillation frequency of the local oscillator is controlled depending on a deviation of the received signal voltage from the voltage window so that the received signal voltage falls into the voltage window.

In a QAM demodulator including an adaptive equalizer, a method of carrier tracking comprising the following steps is disclosed: (A) sampling a QAM signal received from a transmission channel; (B) recovering a symbol clock function from the sampled QAM signal; (C) applying the sampled QAM signal to the adaptive equalizer in order to obtain a QAM equalized signal in a Blind Equalization (BE) mode; (D) using a slicer to locate a nearest plant point for the QAM Blind equalized signal for each recovered symbol clock; (E) using a complex conjugate multiplier to obtain an instantaneous inphase component and an instantaneous quadrature component of a phase angle error signal; (F) using a linear phase detector to obtain an instantaneous phase angle error for each symbol clock; (G) averaging the instantaneous phase angle error signal by using a carrier loop filter; (H) using a complex multiplier to insert an inverse of the averaged phase angle error signal into the QAM Blind equalized signal to compensate for the carrier phase angle error; and (I) repeating the steps (D-H) to close a carrier frequency loop.

A method and apparatus for the detection and correction of large carrier offsets. A set of known correction carrier offsets are used to translate an input signal having a carrier offset. After applying each correction carrier offset, a state of a timing recovery loop is evaluated. The set of known correction carrier offsets are sequentially used to translate the input signal until the timing recovery loop is locked. The carrier offset is substantially acquired when the timing recovery loop is locked.

A method of establishing communication at a tag includes calculating a metric for each of a plurality of automatic frequency control (AFC) hypotheses where the plurality of AFC hypotheses correspond to a timing used by an access point; based on the calculated metrics, identifying one or more relevant AFC hypotheses; performing a check on a demodulated data stream identified using the one or more relevant AFC hypotheses; identifying a valid AFC hypothesis based at least in part on the check; and determining where a frame starts based at least in part on the check.

An arrangement (900), method and unit for AFC in a communication system (100) having: a frequency estimator (980) producing a decision-directed frequency estimate from a received signal; and an AFC loop receiving the decision-directed frequency estimate and performing therewith frequency control. The AFC process may use a CRC-decision directed frequency estimate as the final stage in a multi-stage AFC process (preceded by SCH- and midamble-derived frequency estimate stages), such that a verified received data sequence is used to re-construct a local copy of the ideal received data symbols expected at the output of a detector. This local copy is then correlated with the actual detector output and the results used to estimate the frequency error present on the received signal. The AFC process is inherent suited for discontinuous receive (DRX) applications. This provides the advantage of allowing required frequency correction accuracy to have minimal impact on the error rate of the received data in various channel configurations.

In a particular embodiment, an oscillator adjustment circuit is disclosed. The oscillator adjustment circuit includes a resonator portion comprising a capacitive element coupled to an inductive element and a signal balancing portion comprising a secondary coil of the transformer. The inductive element comprises a primary coil of a transformer. The secondary coil has a grounded center tap.

Stabilized carrier recovery is achieved even at the time of a low C / N ratio by measuring the phase of a signal and controlling VCO or NCO (Numerical Controlled Oscillator) using only a period having few constellation points. At this time, false lock phenomenon is avoided as follows. That is, relatively short SYNC modulated by an already-known pattern is entered into a modulation wave, VCO or NCO oscillation frequency is swept in a wide range and sweep is stopped at a frequency in which the SYNC can be received, thereby carrying out coarse control AFC. Further, a period having long to some extent, having few constellation points is provided in the modulation wave and then, a difference between the frequency of a received modulated signal and a local oscillation signal of VCO or NCO is obtained in this period. This frequency difference is analyzed according to the phase differential function method, self-correlation function method or count method, and the VCO or NCO is controlled based on this result of analysis.

A multi-phase voltage-control oscillator including a first voltage-control oscillator circuit and a second voltage-control oscillator circuit is provided. The first voltage-control oscillator circuit includes a first LC tank and a first inductor assembly unit. The second voltage-control oscillator circuit includes a second LC tank and a second inductor assembly unit. A mutual inductance effect is generated between the inductors of the first voltage-control oscillator and the inductors of the second voltage-control oscillator.

Semiconductor devices provided with high performance high-frequency circuits that reduce interference caused by inductors are provided. In the semiconductor device including a modulator circuit to modulate a carrier wave by a base band signal to output an RF signal and a demodulator circuit to demodulate the RF signal by use of the carrier wave to gain the base band signal and a local oscillator to generate the carrier wave, inductors respectively having a closed loop wire are adopted. Interference caused by mutual inductance is reduced by the closed loop wire. For example, where inductors are adopted in the modulator circuit, a closed loop wire is disposed around the outer periphery of the inductors.

A phase locked loop, voltage controlled oscillator, and phase-frequency detector are provided. The phase locked loop comprises a phase-frequency detector (PFD), a loop filter (LF), a voltage controlled oscillator (VCO), and a 3-stage frequency divider. The PFD receives a reference signal and a feedback signal to determine phase and frequency errors. The LF), coupled to the phase-frequency detector, filters the phase and frequency errors to generate a control voltage. The VCO, coupled to the loop filter, generates a VCO output signal according to the control voltage. The 3-stage frequency divider, coupled to the voltage controlled oscillator, divides the frequency of the VCO output signal 3 times to generate the feedback signal.

In a communication system using the time diversity transmission scheme, the communication system provided with the stable automatic frequency control circuit with the wide frequency pull-in range and under low CN ratio transmission is achieved by removing the modulation phase from the received data through the application of the data correlation of the time diversity. The frequency offset in the received signal is compensated as the phase rotator rotates the phase of the received signal, the phase converter converts the phase rotator output into a phase, the serial-to-parallel converter converts the phase converter outputs into serial-to-parallel sequence, the delay units gives a delay to the serial-to-parallel converter output, the phase adder adds the serial-to-parallel converter output to the delay unit output, the multiplier multiplies the phase adder output by a certain value, the integrator integrates the multiplier output, another integrator integrates the integrator output, and the phase rotator controls the phase of the received signal based on the other integrator output.

A voltage controlled oscillator having a wide oscillation frequency band, desirable carrier-noise characteristic, and desirable linearity of the oscillation frequency relative to a control voltage. The voltage controlled oscillator includes an oscillation unit and a control unit. The oscillation unit generates an output signal having an oscillation frequency corresponding to the control voltage in one of a plurality of oscillation frequency bands. The oscillation unit includes a switching unit for selecting one of the plurality of oscillation frequency bands in accordance with a switching signal. The control unit generates the switching signal in accordance with the control voltage.

A variable frequency oscillator (VFO) circuit having an increased frequency tuning range to selectively obtain operating frequencies above and below a set frequency. The circuit includes a tank inductor connected in parallel with a tank capacitor for primarily defining the set oscillating frequency of the VFO circuit. A switchable capacitor is included for selectively providing a predetermined step-wise decrease of the oscillating frequency to a frequency value below the set frequency of the circuit, and a varactor is included for accommodating selective tuning of the oscillating frequency within a range of frequency values below the set frequency. The inventive circuit selectively includes a switchable inductance element which is selectively electromagnetically coupled to the tank inductor to decrease the overall inductance value of the VFO circuit and, thereby, selectively increase the oscillating frequency above the set frequency value.

The invention discloses a self-adapting resonance control method for transmitting non-contact electric energy, which is characterized by obtaining a phase difference by detecting and calculating the voltage and current outputted by a non-contact electric energy transmitting system contravariant mechanism, and adjusting the driving frequency of the inverter by outputting the electric energy to a PI adjustor and an oscillating element. After a transient state process, the phase difference of the voltage and current outputted by the inverter is zero, thus achieving self-adapting resonance control of circuits. The method guarantees separability between the receiving mechanism and the transmitting mechanism of the system only by detecting the voltage and current outputted by the contravariant mechanism, with the self-adapting resonance control function completely achieved by hardware circuits, while complicated control algorithm is not required. The method not only has self-adapting control capability on load change, but also has adjustment actions to the parameter variations of all the components after the output of the contravariant mechanism; besides, the method has the advantages of guaranteeing the system always works under a resonance condition, ensuring the output power and transmission efficiency reach the maximum value, and promoting the practicability process of the transmission technology of the non-contact electric energy.

A frequency offset correction value estimation section (21) receives a signal including a predetermined fixed pattern from a transmission side, thereafter, selects a combination of fixed patterns used in a process of estimating a frequency offset is selected depending on the state of a channel, and an estimation result of the frequency offset calculated by the combination of the fixed patterns is output as a correction value of a determined frequency offset. A frequency offset correction section (22) receives the received signal obtained after the correction is performed for correcting a frequency offset of the received signal on the basis of the correction value, and an equalizer (23) demodulates the received signal by using a predetermined algorithm.

A voltage-controlled oscillator device with an LC-resonant circuit, in particular for implementing integrated voltage-controlled oscillators for the lower GHz range, is disclosed. The device achieves continuous frequency tunability in a wide range in particular with a low level of phase noise and phase jitter. In the voltage-controlled oscillator, a second inductor can be periodically switched in parallel and / or in series with at least one first inductor of the LC-resonant circuit by way of a switching means actuated with the oscillator frequency. A control input of the switching means is connected to a variable dc voltage. In that respect the relationship of the duration of the conducting state and the duration of the non-conducting state of the switching means is variable within an oscillation period of the oscillator in dependence on the value of the control voltage. In accordance with the relationship of the duration of the conducting state and the duration of the non-conducting state of the switching means within an oscillation period of the oscillator the time-averaged effective inductance is variable in dependence on the value of the control voltage.

A silicon bipolar VCO implementing a double-coupled transformer is disclosed. The VCO circuit, which is suitable in the field of integrated RF circuits, has been integrated into a universal LNB having a down-converter block and PLL merged into a single die and implemented in silicon bipolar technology. The integrated transformer is formed by three turns of stacked metal layers, where the topmost metal layer is employed for the resonator inductance. The VCO is missing conventional biasing resistors and decoupling capacitors, thus improving phase noise and tuning range performance.

In RF transceivers, a method and a system for a frequency feedback adjustment in digital receivers are provided. A DC offset may result from the difference in frequencies between an RF transmitter and an RF receiver. An adjustment of the receiver's frequency may be implemented after synchronization occurs and may be performed by utilizing the Forward Error Correction (FEC) repetition rate in a header of a Bluetooth packet. The adjustment may be performed when the frequency difference exceeds a threshold value. In another aspect, adjusting the frequency of the RF receiver may be performed by modifying and / or changing a phase locked loop (PLL) trimmer register. This approach may allow an RF receiver to operate, in some instances, without the need for an equalizer. In this regard, the power consumed by the RF receiver may be minimized and / or the overall cost of the RF receiver may be reduced.

Channel acquisition in a digital television signal receiver is improved by determining the carrier tracking loop frequency offsets and the symbol timing recovery offsets for each channel in the television receiver. Offsets are stored in respective EEPROMs for each channel. When a channel is to be acquired in the TV receiver the tune command will be applied to the appropriate EEPROMs and the respective values are conveyed to the VSB demodulator to start acquisition of the channel.

A locator using Navstar constellation signals for determining geographical location of a mobile receiver. The locator is integrated with a mobile unit of a cellular network, which derives its reference frequency from a local oscillator (26). A frequency measuring module (28) counts the number of digital numbers derived from the local oscillator passing between two consecutive time-tagged indicators of the cellular network. The estimated frequency is calculated by dividing the number of digital numbers by the nominal time interval (T0) between the indicators.

An apparatus and a method for mitigating interference between uplink signals of a user equipment in a mobile communication system are provided. The apparatus includes a frequency regulator for, when fast movement of a user equipment is confirmed, changing a transmit frequency by calculating a frequency offset compensation value which compensates for a frequency required for a transmit frequency band.

A communications device includes a phase and frequency tracking loop having a signal input and adjustable loop filter that establishes a predetermined tracking loop bandwidth for samples of communication signals received at the signal input and processed within the tracking loop. A tracking loop update circuit updates the loop filter operating parameters. It is operative with the loop filter for increasing or decreasing the tracking loop bandwidth of the phase and frequency tracking loop based on the measured signal-to-noise ratio in the received samples of communication signals at the signal output by the tracking loop and on the known or measured apriori tracking capabilities of demodulator based on the symbol rate of communication signal.

A differential receiver which provides for estimation and tracking of frequency offset, together with compensation for the frequency offset. Estimation and tracking of the frequency offset is undertaken in the phase domain, which reduces computational complexity and allows frequency offset estimation and tracking to be accomplished by sharing already-existing components in the receiver. Compensation for the frequency offset can be performed either in the time domain, before differential detection, or in the phase domain, after demodulation, or can be made programmably selectable, for flexibility.

The invention provides a high-speed moving body Doppler frequency difference correction method which comprises downward frequency difference correction and upward frequency difference correction; wherein, the downward frequency difference correction corrects the Doppler frequency difference of a carrier frequency signal by superposing a pilot signal generated by a standard VCO in a downward carrier frequency signal and detecting the frequency difference of the pilot signal at a mobile terminal; by detecting the frequency difference of the downward pilot signal and pre-superposing the Doppler frequency difference in the carrier frequency signal at the mobile terminal, the upward frequency difference correction corrects an upward signal g received at a fixed terminal due to Doppler frequency shift. The whole correction method evades the changes of an arrival angle and the speed of the mobile terminal, the correction is accurate and timely, and the communication quality is guaranteed to be stable and reliable.

In RF transceivers, a method and a system for a frequency feedback adjustment in digital receivers are provided. A DC offset may result from the difference in frequencies between an RF transmitter and an RF receiver. An adjustment of the receiver's frequency may be implemented after synchronization occurs and may be performed by utilizing the Forward Error Correction (FEC) repetition rate in a header of a Bluetooth packet. The adjustment may be performed when the frequency difference exceeds a threshold value. In another aspect, adjusting the frequency of the RF receiver may be performed by modifying and / or changing a phase locked loop (PLL) trimmer register. This approach may allow an RF receiver to operate, in some instances, without the need for an equalizer. In this regard, the power consumed by the RF receiver may be minimized and / or the overall cost of the RF receiver may be reduced.

A frequency offset estimator is employed that estimates the frequency offset in signal frames that include only binary Phase-Shift Keying (BPSK) carriers in OFDM systems. Specifically, the offset frequency estimator takes advantage of those OFDM systems in which some OFDM symbols only have carriers with either zero or the BPSK constellations. In many WLAN systems such as the system described in standard IEEE802.11a, transmission frames include only BPSK symbols, which are used for training and other services. By making use of these BPSK symbols in each frame, a very accurate estimate of frequency offset can be obtained. By advantageously employing the frequency offset estimator of this invention, a carrier recovery system can achieve high performance even under strong ISI and low SNR. In a specific embodiment of the invention, BPSK carriers spread to be on a line in a complex plane at an angle to the real axis. An estimate of the angle of the line including the BPSK carriers is then employed to obtain an estimate of the frequency offset.

A Method and Apparatus for Automatic Jammer Frequency Control of Surgical Reactive Jammers is disclosed. The system and method to autonomously and selectively jam frequency-hopping signals in near real-time. The system has the ability to automatically detect short duration signals (such as those output from frequency hoppers), to automatically determine if detected signal(s) should be jammed, and subsequently to automatically and extremely quickly activate the jamming transmitter on the frequency-hopper transmitter's frequency. Furthermore, the system improves upon the FFT-based front-end system by incorporating a module that automatically and iteratively comparing the digital FFT results to the analog RF signal to the arrive at a total frequency offset between the FFT results and the analog signal so that the transmitted jamming signal will be more accurately applied on the desired or target frequency. Finally, the system provides a programmable user interface so that operators can set up the system to act autonomously as intended, such that operator intervention is unnecessary when the system is placed in jamming operation mode.