665 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.

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.

An architecture for providing high-speed access over frequency-division multiplexed (FDM) channels allows transmission of ethernet frames and / or other data across a cable transmission network or other form of FDM transport. The architecture involves downstream and upstream FDM multiplexing techniques to allow contemporaneous, parallel communications across a plurality of frequency channels. Moreover, an automatic frequency control resolves some issues of a free-running clock in an upstream tuner of the central concentrator by performing adjustments based on the average frequency error of a number of active upstream tones. In the preferred embodiments of the present invention, the automatic frequency control (AFC) utilizes a feedback loop for at least each active upstream tone. Also, the average of the active upstream tones is determined and is utilized in providing feedback to adjust the automatic frequency control (AFC).

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 manual and automatic fluid control system and method for use in open and laparoscopic laser surgery and electrosurgery is disclosed. The system includes a manual mode along with several automatic modes which can effectuate both suction and irrigation, either individually or simultaneously. In the various automatic modes, the suction and / or irrigation is automatically activated during activation of a medical apparatus for laser surgery or electrosurgery without requiring separate activation from the surgeon or operating room staff. Several safety features for monitoring the fluid control system are also incorporated within the system such as fluid sensors for detecting the absence of irrigation fluid, pressure sensors and vacuum systems for monitoring fluid pressure, fluid sensors for monitoring fluid volume, and warning signals for detecting empty containers. All of the safety features are designed to automatically deactivate suction and / or irrigation means contained within the fluid control system upon detection of unsafe levels. Finally, specially designed suction / irrigation hand pieces are disclosed for use in connection with the fluid control system.

Multi-energy radiation sources comprising charged particle accelerators driven by power generators providing different RF powers to the accelerator, capable of interlaced operation, are disclosed. Automatic frequency control techniques are provided to match the frequency of RF power provided to the accelerator with the accelerator resonance frequency. In one example where the power generator is a mechanically tunable magnetron, an automatic frequency controller is provided to match the frequency of RF power pulses at one power to the accelerator resonance frequency when those RF power pulses are provided, and the magnetron is operated such that frequency shift in the magnetron at the other power at least partially matches the resonance frequency shift in the accelerator when those RF power pulses are provided. In other examples, when the power generator is a klystron or electrically tunable magnetron, separate automatic frequency controllers are provided for each RF power pulse. Methods and systems are disclosed.

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.

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 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.

A radio signal transmitted from a transmitter to a receiver of a mobile communications system, such as the GSM system, often suffers from a phenomenon known as frequency offset by which the frequency of the radio signal is changed from a first frequency to a second frequency. A method is therefore provided for automatically correcting the frequency at the receiver to restore the received radio signal to approximately the first frequency using a multistage frequency correction algorithm. The radio signal comprises a training sequence that is known to the receiver and data symbols that are not known to the receiver. In the first stage of the frequency correction, the frequency offset is coarsely estimated based on the training sequence only, and the data symbols are frequency corrected by back-rotating the received data symbols and the training sequence by the frequency offset estimate. The frequency corrected data symbols and training sequence are then input into the second stage of the frequency correction where they are used to determine a second estimate of the frequency offset that should be more accurate because the second estimate of the frequency offset is based on a larger number of symbols including symbols in the previously frequency corrected training sequence and data symbols. Using this second frequency offset estimate, the data symbols in the received radio signal are frequency corrected by back-rotating the received data symbols by the second frequency offset estimate and are output for detection.

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.

A voltage control type temperature compensation piezoelectric oscillator, includes: a voltage control type oscillation circuit; an automatic frequency control (AFC) circuit outputting a control voltage for controlling an oscillation frequency of the voltage control type oscillation circuit based on an external control voltage; a temperature compensation voltage generating circuit generating a temperature compensation voltage; and a gain variable circuit varying a gain of the temperature compensation voltage. In the oscillator, the gain variable circuit is controlled by the control voltage outputted from the AFC circuit, and the oscillation frequency of the voltage control type oscillation circuit is controlled by an output voltage of the gain variable circuit.

The invention relates to a device for realizing multi-mode mobile communication terminal frequency switch and automatic control, and a relative method, wherein each mode sending / receiving module of multi-mode mobile terminal shares one crystal vibrator to save cost and energy consumption, to allow the terminal to use automatic frequency lock ring at each mode, to effectively keep the carrier wave synchronous of communication chain. And the invention comprises: a multi-mode automatic frequency control word refresher, a voltage-control crystal vibrator and a digit / analogue converter; the refresher is used to select and calculate the frequency control word of target mode; the digit / analogue converter based on said control word generates control voltage via digit signal; said vibrator based on the control voltage generates reference frequency signal; and the invention also provides a multi-mode automatic frequency control word refreshing module to replace the multi-mode automatic frequency control word refreshing device.

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 vital radio based automatic train control system that will interface seamlessly with existing onboard ATC equipment via existing track receiver inputs or directly. The invention provides a means of extending ATC signal territory with reduced equipment installation as compared to traditional cab or wayside based ATC. The invention can be used to reduce train braking distances and reduce headway. Furthermore, the radio cab signal can be used for additional purposes including but not limited to wayside equipment monitoring and rolling equipment monitoring.

Methods and systems are provided for frequency generation suitable for use in wireless devices capable of operating at multiple frequencies. Such systems may change the loop gain of an automatic frequency control loop based on the operating frequency of the wireless device. Furthermore, such a frequency dependent loop gain may be carried out by the selection of subroutines with differing loop gains associated with the subroutines. Furthermore, the loop gain may also be temperature compensated based on the temperature of the wireless device and / or the operating frequency of the device.

Embodiments may be used to control a controllable element that has a nonlinear but monotonic relationship with a control value. In such embodiments, a system may perform control by receiving an error value corresponding to an error of an output signal from the controllable element, and determining the control value within two iterations of a Newton (Secant) algorithm, where the control value enables generation of the output signal within a predetermined tolerance to a nominal value for the control signal.

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.

A system and method is provided that searches for the frequency and phase of a CDMA transmission in an iterative manner. With its automatic frequency control (AFC) disabled, the receiving system performs a coarse search for the transmitter's CDMA phase at a nominal receiving frequency. When the coarse phase is obtained, the AFC is invoked with a large-range pull-in, to obtain an initial, coarse frequency that is likely to be closer to the transmitter's frequency than the initial nominal frequency. At this coarse frequency, the receiving system repeats its search for the transmitter's CDMA phase, starting at the previously determined coarse phase. Because this second phase determination is conducted in the presence of less frequency error, it provides for a more accurate phase determination. The AFC is again invoked, but with a small-range pull-in, to obtain a finer frequency determination. Because the finer frequency determination is conducted in the presence of less phase error, a substantial improvement in the accuracy and precision of the frequency determination can be achieved. To achieve this more accurate phase and frequency determination within the same time duration as a conventional acquisition process, the initial coarse phase determination is conducted using a rapid, albeit less accurate, process than the conventional phase determination.

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.

An automatic frequency controller includes a frequency offset estimating section that calculates phase distortion quantities and the average thereof from known signals contained in a received signal. The frequency offset estimating section obtains, from the average distortion quantity, signal powers corresponding to a plurality of candidate frequency offsets set at frequency offset estimation accuracy intervals in a frequency offset estimation range. The frequency offset estimating section looks at the signal powers through a frequency window with a frequency width corresponding to a transmission path state. This makes it possible to maximize the signal power of a frequency of a radio wave or radio waves corresponding to the transmission path state, and to place the radio wave or radio waves corresponding to the transmission path state as a frequency controlled object. This can improve demodulation accuracy. Fine adjustment of the candidate frequency offsets can improve the estimation accuracy of the frequency offset without changing the frequency offset estimation range.

The invention discloses a frequency shift elimination method based on a multi-wavelength relevant optical communication system and relates to the field of an optical communication system. Reference light which is not modulated at a receiving end enters the local oscillation input end of a 90-degree mixer; local oscillation light with a wavelength corresponding to the reference light enters the signal input end of the 90-degree mixer; after photoelectric conversion, an electrical signal with frequency shift opposite to that of electrical signals with other wavelengths subjected to photoelectric conversion is obtained; and in an electric field, the electrical signal is respectively multiplied by electrical signals with other wavelengths subjected to photoelectric conversion to effectively eliminate the frequency shift of a modulated light carrier and the corresponding local oscillation light. The method can be used for correcting and eliminating large-scale frequency shift, the tolerance degree of the system to the frequency shift can be improved. In addition, the system has low requirements on the amount of lasers; a corresponding wavelength division multiplexing structure has relatively simple structure; an optical terminal of a coherent receiving end does not need feedback devices, such as phaselocked loops, automatic frequency control devices and the like; the structure of the multi-wavelength relevant optical communication system is simplified; and system cost is saved.

An Automatic Frequency Control (AFC) circuit for a mobile terminal employs a fractional-N Phase Locked Loop (PLL) to directly reduce errors in the synthesized frequency, such as due to component tolerances, temperature drift, and the like. The frequency error is detected by the average speed of rotation of the I,Q constellation. A corresponding offset is added to the tuning frequency selection word prior to encoding, such as in a ΔΣ modulator, to generate an effective non-integer PLL frequency division factor over a specified duration. The ΔΣ modulator may include dithering the different integer values by a pseudo-random number to minimize noise in the output frequency spectrum introduced by the fractional-N division. Component and parameter selection allow a high degree of resolution in frequency control of the fractional-N PLL. By directly controlling for the frequency error, a DAC and XTAL oscillator tuning circuit may be eliminated from the AFC circuit.