664 results about "Automatic frequency control" patented technology

The present invention provides for a system and method for improvement of radio transmitter and receiver frequency accuracy for a local radio communication unit that communicates digital data with a remote communication unit. In the local unit the received radio signal is down-converted, and converted to complex baseband digital samples by an analog-to-digital converter. A downlink digital phase rotator applies a fine frequency shift to the samples in accordance with a receiver frequency offset command. The resultant baseband signal is used by the data demodulator and by a receiver frequency error estimator to obtain receiver frequency errors. A data modulator generates baseband complex samples which are shifted in carrier frequency by an integrated uplink digital phase rotator in accordance with a transmitter frequency offset command. The modulated samples are then converted by a digital-to-analog converter and upconverted in frequency for radio transmission to the remote unit. The local oscillator signals for both upconverter and downconverter are phase locked to a reference frequency generated by a VCXO. An automatic frequency control (AFC) function nulls the transmitter and receiver frequency error by the frequency adjustment commands to the uplink and downlink phase rotators or to the VCXO digital-to-analog converter (VCXO DAC) by feedback control principals based on measured receiver frequency error. During frequency track mode when communications between local and remote units are possible, the AFC only adjusts radio frequency via phase rotator commands and the VCXO command remains fixed, thereby avoiding communications performance degradation by VCXO frequency quantization error due to the VCXO DAC. The AFC adjusts VCXO frequency only during a preliminary acquisition mode prior to data communications, or to back out excessively large frequency offsets accumulated in the downlink and uplink phase rotators during track mode. When a VCXO adjustment is made in track mode, phase rotator adjustments are simultaneously applied to cancel the errors in transmitter and receiver radio frequencies caused by the step change due to VCXO frequency quantization thereby mitigating VCXO frequency quantization noise.

Disclosed is a system and method for providing an oscillating signal of relatively precise frequency without using a signal provided by a crystal as a reference. Disclosed is a feedback oscillator circuit configured to output an oscillating signal having a frequency defined by a reference signal. The oscillating signal can be sent to one or more circuits including at least one frequency sensitive element. The frequency sensitive element produces an output signal which depends on the frequency of the oscillating signal. A controller controls the reference signal in order to cause an attribute of the output signal to have a value within a desired range.

The present invention provides for a system and method for improvement of radio transmitter and receiver frequency accuracy for a local radio communication unit that communicates digital data with a remote communication unit. In the local unit the received radio signal is down-converted, and converted to complex baseband digital samples by an analog-to-digital converter. A downlink digital phase rotator applies a fine frequency shift to the samples in accordance with a receiver frequency offset command. The resultant baseband signal is used by the data demodulator and by a receiver frequency error estimator to obtain receiver frequency errors. A data modulator generates baseband complex samples which are shifted in carrier frequency by an integrated uplink digital phase rotator in accordance with a transmitter frequency offset command. The modulated samples are then converted by a digital-to-analog converter and upconverted in frequency for radio transmission to the remote unit. The local oscillator signals for both upconverter and downconverter are phase locked to a reference frequency generated by a VCXO. An automatic frequency control (AFC) function nulls the transmitter and receiver frequency error by the frequency adjustment commands to the uplink and downlink phase rotators or to the VCXO digital-to-analog converter (VCXO DAC) by feedback control principals based on measured receiver frequency error. During frequency track mode when communications between local and remote units are possible, the AFC only adjusts radio frequency via phase rotator commands and the VCXO command remains fixed, thereby avoiding communications performance degradation by VCXO frequency quantization error due to the VCXO DAC. The AFC adjusts VCXO frequency only during a preliminary acquisition mode prior to data communications, or to back out excessively large frequency offsets accumulated in the downlink and uplink phase rotators during track mode. When a VCXO adjustment is made in track mode, phase rotator adjustments are simultaneously applied to cancel the errors in transmitter and receiver radio frequencies caused by the step change due to VCXO frequency quantization thereby mitigating VCXO frequency quantization noise.

A communication system using OFDM transmission from a base station to subscriber units, includes means for achieving a bi-directional channel. These means comprise transmitting means in the subscriber units for the transmission of signal synchronous with the guard time interval in the OFDM transmission, and receiving means in the base station for the reception of the transmitted signals. The system also includes signal shaping means in the receiver of the base station and / or the subscriber unit for the application of a window in time to signals received therein. A communication system includes a combination of CDMA modulation codes and OFDM coding / decoding means to achieve orthogonality between signals from the various users in the uplink. A communication system includes a combination of OFDM and channeling means for achieving orthogonality between signals from the various users in the uplink. Automatic Frequency Control is achieved with means in the mobile unit for achieving a frequency-lock to the base station.

A method for generating stabilized particle acceleration by a radio-frequency (RF) accelerator is described, comprising operating the accelerator in a warm-up mode during a warm-up time period, without injecting charged particles or without accelerating injected charged particles, and operating the accelerator in a beam-on mode during a beam-on time period after the warm-up time period, to accelerate charged particles injected by the charged particle source. Automatic frequency control to match an expected frequency of the accelerator during the beam-on time period, prior to the start of the beam-on time period, for stability, is also described.

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.

A treadmill includes a body having a belt for supporting an exerciser, an exerciser detecting portion installed in a predetermined area of the body to detect movement of the exerciser, a driving motor coupled to the body to drive the belt, a control portion for generating a first control signal for adjusting a rotation speed of the driving motor based on a signal received from the exerciser detecting portion, a motor driving portion for adjusting the rotation speed of the driving motor according to the first control signal received from the control portion, and an electrical braking portion for reducing the rotation speed of the driving motor. The treadmill quickly follows acceleration or deceleration of an exerciser; provides an experience as if the exerciser is exercising on the ground, thereby improve an exerciser's exercising experience; accepts various exercising patterns of an exerciser; resolves a problem in that a motor driving portion is tripped due to a load caused by quick deceleration; and preprocesses measured values of an exerciser's position to resolve a problem in that a speed of a belt cannot be controlled due to measurement errors contained in measured values.

The invention relates to an automatic frequency tracking method and a system for an ultrasonic transducer. A direct digital frequency synthesizer is used as a signal source, wherein the direct digital frequency synthesizer can be an independent integrated chip and also be achieved by the method that a digital part of a DDS is integrated in a site programmable logical element FPGA and then a digital-analog converter is additionally added. The design of the invention adopts a frequency sweeping and tracking policy, and an automatic frequency controller achieved by the programmable element controls the output frequency of the DDS according to a feedback signal sampled from the self transducer end so as to achieve the full digitization automatic frequency tracking and ensure that the ultrasonic transducer work near a resonance point all the time to obtain the optimal efficiency. A phase comparator utilizes a trigger to give out the arriving time difference of two riser edge signals of two input signals I ph and V ph aiming to the sensitive characteristics of the riser edge signals, and the sequence of the riser edge signals of the two input signals I ph and V ph is given out by a Dirrect pin.

Components of a radio-frequency (RF) apparatus including transceiver circuitry and frequency modification circuitry of a crystal oscillator circuit that generates a reference signal with adjustable frequency may be partitioned in a variety of ways, for example, as one or more separate integrated circuits. The frequency modification circuitry may be implemented as part of a crystal oscillator circuit that includes digitally controlled crystal oscillator (“DCXO”) circuitry and a crystal. The frequency modification circuitry may include at least one variable capacitance device and may be employed to generate a reference signal with adjustable frequency. The adjustable reference signal may be provided to other components of the RF apparatus and / or the RF apparatus may be configured to provide the adjustable reference signal to baseband processor circuitry. Automatic frequency control (AFC) circuitry may be integrated with other components of RF circuitry and may generate frequency control signals for the frequency modification circuitry based on, for example, a signal received from a temperature sensor. Digital-to-analog converter (DAC) circuitry may be integrated with other components of RF circuitry to enable all-digital frequency control communications from baseband processor circuitry to RF circuitry.

Preferred embodiments of the present invention provide systems and methods that automatically correct the desired on-time of switching elements as the resonant frequency changes, so as to maintain the correct proportional value.

The invention discloses a phase-locked loop frequency synthesizer which comprises a phase detection discriminator, a charge pump, a low-pass loop filter, a voltage controlled oscillator with a switched capacitor array, a frequency divider, an automatic frequency controller, a voltage comparison circuit and a relock control circuit, wherein the voltage comparison circuit judges whether tuning voltage Vtune output to the voltage controlled oscillator by the low-pass loop filter is in the preset voltage range in real time when the phase-locked loop frequency synthesizer is at the phase-locked loop loss lock detection stage; and the relock control circuit dynamically adjusts a value of a control word of the switched capacitor array of the voltage controlled oscillator according to the comparison result of the voltage comparison circuit. The invention also discloses a corresponding phase-locked loop loss lock detecting and adjusting method. By the phase-locked loop frequency synthesizer and the phase-locked loop loss lock detecting and adjusting method, increase of reference harmonic energy can be avoided; interference is reduced, and the coarse tuning time is shortened.

Components of a radio-frequency (RF) apparatus including transceiver circuitry and frequency modification circuitry of a crystal oscillator circuit that generates a reference signal with adjustable frequency may be partitioned in a variety of ways, for example, as one or more separate integrated circuits. The frequency modification circuitry may be implemented as part of a crystal oscillator circuit that includes digitally controlled crystal oscillator (“DCXO”) circuitry and a crystal. The frequency modification circuitry may include at least one variable capacitance device and may be employed to generate a reference signal with adjustable frequency. The adjustable reference signal may be provided to other components of the RF apparatus and / or the RF apparatus may be configured to provide the adjustable reference signal to baseband processor circuitry. Automatic frequency control (AFC) circuitry may be integrated with other components of RF circuitry and may generate frequency control signals for the frequency modification circuitry based on, for example, a signal received from a temperature sensor. Digital-to-analog converter (DAC) circuitry may be integrated with other components of RF circuitry to enable all-digital frequency control communications from baseband processor circuitry to RF circuitry.

A terminal includes at least one wireless communication application module (1) and a plurality of further application modules (4, 5, 6, 8). Multiple radio frequency clock signals are generated for the different modules having respective clock frequency characteristics and including at least first and second clock frequencies that are not integral multiples nor sub-multiples of each other nor of a third frequency. The clock generation comprises reference frequency means (14), fractional-N phase-locked loop frequency synthesizer means (15) responsive to the reference frequency means, and different automatic frequency control means for adjusting clock frequencies relative to received signals. The reference frequency means (14) is arranged to supply a common reference frequency signal to a plurality of the fractional-N phase-locked loop frequency synthesizer means (17, 18, 19, 25, 26, 41,42) that supply the first and second clock frequencies respectively for the application modules. Selective activation means (30,52) selectively activates and de-activates the phase lock loop means as required by the corresponding application module or modules.