32results about How to "Frequency error" patented technology

The invention allows for the accurate, real-time readout of the optical frequency of a swept-wavelength laser device by counting the number of fringes of a calibrated etalon that occur as the laser is swept. The distinguishing feature of the present invention is that the etalon fringe signal is phase-locked to a slave signal of a higher multiple frequency. The higher frequency of the slave signal divides the frequency interval of the etalon fringe spacing by the additional frequency multiple. The slave signal therefore generates a scale for optical frequency that is of higher resolution than possible with the etalon alone. The phase-lock also insures that the slave signal tracks monotonic scans of the optical frequency regardless of scan profile.The invention also allows for the precise, real-time control of the optical frequency of a laser during the sweep of the laser. By comparing a signal proportional to the transmission of light through a calibrated Fabry-Perot etalon to a reference control signal, the phase difference between etalon transmission signal and the reference signal may be fed back to the laser to drive the phase difference to zero (phase-lock). The phase-lock ensures that the optical frequency profile of the sweep follows exactly the frequency profile of the reference signal. Tailoring the input reference signal controls the velocity of the optical-frequency sweep.

A communication semiconductor integrated circuit has a demodulator circuit built in a single semiconductor chip. The demodulator circuit is constructed to demodulate a received OFDM-modulated packet signal including a preamble that has two or more fixed-signal sequences, and to have a frequency-error estimating / correcting function that estimates the frequency error of the received signal by using the received preamble and corrects the received signal for the frequency error, a fast Fourier transform function (FFT portion 210) that converts the time-axis information of the corrected received signal to frequency-axis information, a transmission path response estimating / correcting function that estimates the status of the transmission path from the converted signal and corrects the received signal for the transmission path response, and an averaging function that averages the received signal after being corrected for the frequency error so that the averaging can be performed before the fast Fourier transform process.

A global positioning system (GPS) receiver and method are provided for detecting a jammer signal using fast Fourier transform (FFT). A correlator correlates GPS signals received from GPS satellites with codes based on a plurality of carrier frequency signals having predetermined frequency offsets therebetween, and computes n correlated samples associated with each of the GPS satellites. A memory stores the n correlated samples associated with each of the GPS satellites and n FFT bins corresponding thereto. A FFT processor transforms the n correlated samples read from the memory using n-point FFT to obtain the n FFT bins, and transfers the n FFT bins to the memory. A peak detector detects largest peaks exceeding a lowered detection threshold from the FFT bins associated with each of the GPS satellites. A jammer detection unit makes a determination as to whether a peak relatively far away from other peaks is present among the largest peaks, and detects a signal of a peak far away from other peaks.

A method for fast acquisition, in as little as 6-15 seconds, of signals from a satellite in a Satellite Positioning System (SATPS), such as GPS or GLONASS, that does not require permanent storage of satellite ephemeris information at an SATPS ground station. This SATPS signal acquisition method can be used whenever the "new" station initially powers up or has lost lock on one or more SATPS signals that must be (re)acquired. A reference SATPS station provides the new SATPS station with an estimated reference station location and ephemeris information for one or more identified SATPS satellites visible from the reference station. The new station receives and uses this information to establish carrier frequency ranges to search for the identified SATPS satellite, by limiting the search to a reduced frequency range based upon estimated Doppler shift of SATPS signals received from this satellite. The actual frequency shift may differ from the estimated Doppler shift, due in part to errors in a frequency source used by the new station. When a first SATPS satellite signal is acquired and locked onto by the new station, the error in the new station frequency source is estimated, and the frequency range for searching for an SATPS signal from another satellite is reduced. Acquisition of additional SATPS satellite signals occurs more quickly. This system also allows the use of less accurate timing sources for the new stations. A new station need not store ephemeris information for the SATPS satellites but may call upon and use the ephemeris information available at the reference station.

A delta-sigma converter has coarse and fine ADCs, wherein an integrated error signal is coupled to the coarse ADC whose output drives a DAC to create feedback that achieves loop balance. The coarse ADC provides the most significant bits of the result. The integrated error signal is also applied to a fine ADC whose output bits are not incorporated into the feedback, but which are combined with those of the coarse ADC and the combination applied to a filter that averages the hunting that represents loop balance. A DC feed forward circuit shunts the integrator with a replica of the applied input signal to apply it to the coarse ADC through a summer, allowing its output to be just the integrated error signal without including the applied input. If continuous integration is used, an AC feed forward circuit provides a compensatory voltage that is removed from the integrator output (or alternatively, is added to its input) and that corrects for a frequency dependent error.

An electronic system (10) includes a phase-locked loop (30) and a frequency synthesis circuit (20), for generating a jitter-free output clock (CLK1, CLK2) at a desired frequency. The phase-locked loop (30) includes a voltage-controlled oscillator (37) that produces a number (N) of equally spaced clock phases at a frequency (fVCO) that depends also upon a programmable feedback frequency divider (38) and a prescale divider (32). The frequency synthesis circuit (20) generates the output clock (CLK1, CLK2) at a frequency under the control of a frequency select word (FREQ) that indicates the number of clock phases between successive clock edges. A central processing unit (12), either itself or from a look-up table (13), generates a feedback divide integer (M) and the frequency select word (FREQ) according to a desired frequency (f), by way of a minimization of the frequency error. The frequency of the output clock (CLK1, CLK2) can be generated in a jitter-free manner, since only integer values are used in the frequency synthesis circuit (20), at relatively low frequency error.

System and method for determining an optimal transmission center frequency for a traffic station (30) in a satellite communication system (100) includes transmitting, by the traffic station (30) in a first uplink channel, a first burst of information in a first uplink TDMA frame to a satellite (10) and receiving, by the traffic station (30) in a first downlink channel, a downlink TDMA frame including a reference burst (210) and the first burst of information. A Doppler offset ratio is calculated based on a measured frequency shift of the received first burst of information. A local oscillator offset ratio is calculated based on a measured frequency shift of the reference burst and the Doppler offset ratio. An adjusted transmission frequency of a second uplink channel is calculated based on the Doppler offset ratio and the local oscillator offset ratio.

A system, method and device for frequency acquisition. In particular, the embodiments allow for a mobile telephone to simultaneously receive data and / or voice signals while acquiring a GPS signal for its navigation feature. The system, method and device of the present embodiments employ a digital rotator and a local oscillator in concert to acquire the respective signals, correct any frequency errors associated with those signals, and maintain a local timing reference suitable for receiving and transmitting data through a mobile network while simultaneously providing an accurate location through a GPS system.

Synchronization method for a multi-carrier transceiver using a filter bank, for example a cosine modulated filter bank, a wavelet packet filter bank or a complex modulated filter bank, the transceiver comprising a transmitter (100) and a receiver (300) able to communicate with each other over a communication channel (200), the method comprising the following steps: sending a periodic and coded training sequence over the communication channel (200) with the transmitter (100), determining in the receiver (300) time alignment information from the received training sequence, performing a coarse synchronization of the receiver (300) to said transmitter (100) using said time alignment information, sending modulated data (1) in data mode over the communication channel (200) with the transmitter (100), pilot signals being multiplexed into said data (1), tracking sampling frequency offset and phase jitter within the receiver (300) using the pilot signals, performing the continuous synchronization of the transceiver with the help of the tracking information determined in the step of tracking. The invention also relates to a multi-carrier transceiver, consisting of a transmitter (100) and a receiver (300), able to perform this synchronization method.

A frequency-control unit is used for controlling an external controllable reference-frequency source. The frequency-control unit includes a filter unit with a controllable filter parameter, which is configured to derive, using the filter parameter, from a frequency-error signal a frequency-control signal for minimizing the frequency error of the reference frequency; and a correlation unit, which is configured to determine from frequency errors of the reference frequency at different points in time a correlation measure indicative of a correlation between the frequency errors at the different points in time. The frequency-control unit is configured to adapt the controllable filter parameter of the filter unit in dependence on the determined correlation measure. The value of the filter parameter can depend also on a receiver path strength, such as an RSCP value.

A frequency error correction device for an OFDM receiver is proposed. The receiver receives an OFDM signal with a preamble section and a payload section including pilot carriers. The frequency error correction device includes a first frequency correction unit for correcting a relative phase error in a predetermined period of time based upon a frequency error in the preamble section of the OFDM signal in time domain, and a second frequency correction unit for correcting a remaining phase error in every predetermined period of time based upon the pilot carriers of the OFDM signal in frequency domain.

A clock synthesis circuit) including a phase-locked loop and one or more frequency synthesis circuits is disclosed. The phase-locked loop includes a voltage-controlled oscillator (VCO) having a sequence differential stages o produce equally spaced clock phases. The frequency synthesis circuit includes a sequence of adder-and-register units that select one of the VCO clock phases. An output multiplexer receives each of the selected clock phases, and selects among these clock phases in sequence; the output of the multiplexer is applied to a first toggle flip-flop that changes state in response to rising edge transitions at the output of the multiplexer. A second toggle flip-flop is clocked by the output of the first toggle flip-flop, itself toggling in response to rising edge transitions at the output of the first toggle flip-flop. One or more additional flip-flops can be similarly connected in sequence. The additional toggle flip-flop enables the VCO to be formed with fewer stages for a given frequency resolution, reducing noise and thus frequency error.

A radio communication device, which transmits or receives a signal at a predetermined carrier frequency. The device includes a reference oscillator, which generates a clock frequency having a clock frequency error relative to a specified frequency thereof, a processor, which estimates the clock frequency error and parses the error to determine coarse and fine error correction components, at least one frequency synthesizer, which responsive to the clock frequency and to the coarse error correction component, generates a partially corrected frequency having a residual frequency error, which partially corrected frequency is applied to process the signal and baseband processing circuitry, which applies the fine error correction component to process the signal so as to correct the residual frequency error.

A delta-sigma converter has coarse and fine ADCs, wherein an integrated error signal is coupled to the coarse ADC whose output drives a DAC to create feedback that achieves loop balance. The coarse ADC provides the most significant bits of the result. The integrated error signal is also applied to a fine ADC whose output bits are not incorporated into the feedback, but which are combined with those of the coarse ADC and the combination applied to a filter that averages the hunting that represents loop balance. A DC feed forward circuit shunts the integrator with a replica of the applied input signal to apply it to the coarse ADC through a summer, allowing its output to be just the integrated error signal without including the applied input. If continuous integration is used, an AC feed forward circuit provides a compensatory voltage that is removed from the integrator output (or alternatively, is added to its input) and that corrects for a frequency dependent error.

The present invention discloses a bedside or point of care assay for properly positioning a feeding tube in the stomach of a patient based on detecting the presence of a hydrolytic enzyme found in the stomach by an ester substrate which can be impregnated on a pH strip. The application of this test reduces the risk of tube misplacement and the resulting harm to the patient that occurs in the event of tube misplacement.

The semiconductor device provided assures stable communication processes. For example, a varactor diode for adjusting the reference frequency is comprised within a digital crystal-controlled oscillating circuit provided as an internal circuit of the front-end circuit for generating the reference oscillation signal of a PLL circuit or the like. The varactor diode is formed to a semiconductor layer DF of the so-called SOI structure in the structure where an embedded insulating layer, a n−type semiconductor region, a p type semiconductor region, and a n+ type semiconductor region are formed in this sequence and the n+ type semiconductor region is connected to a cathode node which becomes the frequency adjusting node. Moreover, a p+ type semiconductor region connected to the p type semiconductor region is formed in both sides of the n+ type semiconductor region, and this p+ type semiconductor region is connected to an anode node to which the ground voltage is applied. Accordingly, noise transferred to a frequency adjusting node via the embedded insulating layer from a semiconductor substrate can be reduced.

A system and method for minimizing the frequency error of satellite modem signals at a satellite gateway. The gateway downstream baud (symbol) clock and the elements that control the upstream frequency (i.e., local oscillators in the conversion chain, A / D sample clocks) are locked to a common frequency reference. The gateway sends upstream satellite frequency offset information, such as satellite ephemeris data from which to calculate Doppler offset, to the satellite modem. The satellite modem locks the frequency of the satellite modems master oscillator to the recovered baud rate using a frequency locked loop. The satellite modem uses its master oscillator as the carrier reference for the upstream frequency up conversion. The satellite modem uses or calculates the upstream satellite frequency offset and compensates for this offset by shifting its center frequency.

The present invention discloses a bedside or point of care assay for properly positioning a feeding tube in the stomach of a patient based on detecting the presence of a hydrolytic enzyme found in the stomach by an ester substrate which can be impregnated on a pH strip. The application of this test reduces the risk of tube misplacement and the resulting harm to the patient that occurs in the event of tube misplacement.

A portable radio system, a portable radio equipment to be used in the same and a frequency error prediction method can be adapted to large frequency error by making tap number smaller and frequency error smaller. The portable radio system employs an automatic frequency control for detecting a frequency shift of an internal oscillator of a portable radio equipment with reference to a received wave transmitted from a base station having higher precision of frequency and adjusting the frequency of the internal oscillator by feeding back the frequency shift to the internal oscillator. Coordinate rotation digital computation (CORDIC) is employed for calculation of arctangent in the automatic frequency control.

A repeater converts a frequency of a received signal based on a local oscillating frequency and transmits a transmitting signal of a frequency that is different from the frequency of the received signal. Here, the local oscillating frequency includes a local oscillating error that may be different in a plurality of repeaters. Accordingly, the repeater cancels the local oscillating frequency error itself in a frequency conversion so that transmitting frequencies between the plurality of repeaters may be identical.

A digital IF demodulator includes an analog-to-digital (A / D) converter that receives an analog IF signal and converts it to a digital IF signal. A parallel multiplier then down-converts the digital IF signal to a baseband signal having a video component and an audio component. The frequency down-conversion uses a parallel multiplier driven by an outer feedback loop that corrects gross frequency errors in said digital IF signal. The digital IF demodulator also includes a video recovery circuit that selects the video component from the baseband signal and further down-converts the baseband signal to a video baseband using a video complex mixer driven by an inner feedback loop that corrects fast phase perturbations in the video recovery circuit. Finally, the digital IF demodulator includes an audio recovery circuit that (i) receives said baseband signal from the parallel multiplier, and (ii) down-converts the audio component to an audio baseband signal using an audio complex mixer.

An outgoing transmission carrier frequency at, for example, a remote terminal, may be adjusted based on a feature rate of an incoming transmission. The adjustment may compensate for error in the outgoing transmission carrier frequency. The incoming transmission may be from a satellite or hub, for example. The outgoing transmission may be the signal that is transmitted by an antenna, or the outgoing transmission may be converted to be at another carrier frequency such as a higher carrier frequency for ultimate transmission by an antenna. Also, a remote terminal may be synchronized to a satellite network with or without knowledge of the remote terminals' geographical location and with or without time stamps.

A receiver has a receiving unit including a PLL, a mixer, and a filter, and demodulating unit including a frequency error detector for detecting a frequency error in a signal from a filter. The PLL includes a local oscillator for supplying a local oscillation signal to a mixer, a variable frequency divider for frequency-dividing the local oscillation signal based on a signal from the frequency error detector, and a phase comparator for comparing a signal from the variable frequency divider with a signal from a crystal oscillator. The PLL can reduce the frequency error of the local oscillation signal.

System and method for determining an optimal transmission center frequency for a traffic station (30) in a satellite communication system (100) includes transmitting, by the traffic station (30) in a first uplink channel, a first burst of information in a first uplink TDMA frame to a satellite (10) and receiving, by the traffic station (30) in a first downlink channel, a downlink TDMA frame including a reference burst (210) and the first burst of information. A Doppler offset ratio is calculated based on a measured frequency shift of the received first burst of information. A local oscillator offset ratio is calculated based on a measured frequency shift of the reference burst and the Doppler offset ratio. An adjusted transmission frequency of a second uplink channel is calculated based on the Doppler offset ratio and the local oscillator offset ratio.

A method and apparatus are disclosed for detecting a pilot signal in a wireless receiver using coherent combining / noncoherent detection techniques. Coherent combining / noncoherent detection techniques are used to detect the pilot signal whenever the receiver is already frequency locked, or otherwise known to have a small frequency offset Conventional noncoherent combining / noncoherent detection techniques are utilized to initially acquire the timing of the forward channel. Once the receiver is frequency locked, coherent combining / noncoherent detection techniques may be used to continuously detect the pilot signals. After the receiver is frequency locked, the residue frequency error is small over several consecutive correlator outputs The correlator outputs can thus be combined coherently (since the frequency error is known to be small), and the phase dependency is then eliminated by noncoherent detection.

The invention relates to a method of correcting frequency errors for use in CDMA mobile radio terminals which is adaptive, depending on the value of the frequency error. Thus the invention provides three different frequency error correction processing modes: a processing mode with no correction, an open-loop processing mode for coarse correction, and finally a closed-loop processing mode for very accurate correction. Said frequency error processing modes are selected by a central control unit as a function both of the value of the frequency error and of a quality factor determined by a quality control unit of a channel coefficient filter.

A spread spectrum communications system adapted to receive simultaneous signals from multiple transmitters, separates frequency error and equalizes and decodes continuous streams of data sets from a plurality of matched filters with frequency correction and which sorts through data and successfully decodes data bits.

In a method and an apparatus (1) for transmission diversity mode detection in a mobile radio receiver using a decision function, the decision function which is used for detection of the transmission diversity mode is based on the coherent processing of two successive input signal data tuples {r(k);r(k+1)} and {r(k+2);r(k+3)} and recording of a phase offset between the two tuples.

A spread spectrum communications system adapted to receive simultaneous signals from multiple transmitters, separates frequency error and equalizes and decodes continuous streams of data sets from a plurality of matched filters with frequency correction and which sorts through data and successfully decodes data bits. The spread spectrum communications system includes a transmitter and a receiver. The receiver includes an RF receiver. At least one PNB matched filter receives signals from the RF receiver. A plurality of frequency shifters receives a signal from the at least one PNB matched filter. A plurality of PNA matched filters receives data from the at least one PNB matched filter and the plurality of frequency shifters. An equalizer / decoder receives signals from the plurality of PNA matched filters.