4021 results about "Frequency shift" patented technology

An apparatus generates femtosecond pulses from laser amplifiers by nonlinear frequency conversion. The implementation of nonlinear frequency-conversion allows the design of highly nonlinear amplifiers at a signal wavelength (SW), while still preserving a high-quality pulse at an approximately frequency-doubled wavelength (FDW). Nonlinear frequency-conversion also allows for limited wavelength tuning of the FDW. As an example, the output from a nonlinear fiber amplifier is frequency-converted. By controlling the polarization state in the nonlinear fiber amplifier and by operating in the soliton-supporting dispersion regime of the host glass, an efficient nonlinear pulse compression for the SW is obtained. The generated pulse width is optimized by utilizing soliton compression in the presence of the Raman-self-frequency shift in the nonlinear fiber amplifier at the SW. High-power pulses are obtained by employing fiber amplifiers with large core-diameters. The efficiency of the nonlinear fiber amplifier is optimized by using a double clad fiber (i.e., a fiber with a double-step refractive index profile) and by pumping light directly into the inner core of this fiber. Periodically poled LiNbO3 (PPLN) is used for efficient conversion of the SW to a FDW. The quality of the pulses at the FDW can further be improved by nonlinear frequency conversion of the compressed and Raman-shifted signal pulses at the SW. The use of Raman-shifting further increases the tuning range at the FDW. For applications in confocal microscopy, a special linear fiber amplifier is used.

Fiber, cable, and wireless data channels are typically impaired by reflectors and other imperfections, producing a channel state with echoes and frequency shifts in data waveforms. Here, methods of using OTFS pilot symbol waveform bursts to automatically produce a detailed 2D model of the channel state are presented. This 2D channel state can then be used to optimize data transmission. For wireless data channels, an even more detailed 2D model of channel state can be produced by using polarization and multiple antennas in the process. Once 2D channel states are known, the system turns imperfect data channels from a liability to an advantage by using channel imperfections to boost data transmission rates. The methods can be used to improve legacy data transmission modes in multiple types of media, and are particularly useful for producing new types of robust and high capacity wireless communications using non-legacy OTFS data transmission methods.

A method of modulating communications signals, such as optical fiber, wired electronic, or wireless signals in a manner that facilitates automatic correction for the signal distortion effects of echoes and frequency shifts, while still allowing high rates of data transmission. Data symbols intended for transmission are distributed into N×N matrices, and used to weigh or modulate a family of cyclically time shifted and cyclically frequency shifted waveforms. Although these waveforms may then be distorted during transmission, their basic cyclic time and frequency repeating structure facilitates use of improved receivers with deconvolution devices that can utilize the repeating patterns to correct for these distortions. The various waveforms may be sent in N time blocks at various time spacing and frequency spacing combinations in a manner that can allow interleaving of blocks from different transmitters. Applications to channel sounding / characterization, system optimization, and also radar are also discussed.

A base station having the strongest downlink signal is identified by utilizing a unique slope of a pilot tone hopping sequence being transmitted by a base station. Specifically, base station identification is realized by determining the slope of the strongest received pilot signal, i.e., the received pilot signal having the maximum energy. In an embodiment of the invention, the pilot tone hopping sequence is based on a Latin Squares sequence. With a Latin Squares based pilot tone hopping sequence, all a mobile user unit needs is to locate the frequency of the pilot tones at one time because the pilot tone locations at subsequent times can be determined from the slope of the Latin Squares pilot tone hopping sequence. The slope and initial frequency shift of the pilot tone hopping sequence with the strongest received power is determined by employing a unique maximum energy detector.

A transmitter and corresponding method for transmitting an OFDM signal in a communications channel, including a plurality of base-band OFDM modulators, each for modulating a respective data signal onto a plurality of orthogonal sub-carriers and outputting a respective sub-channel OFDM signal; and a fast convolution filter and up-converter for applying fast convolution filtering and digital up-conversion to the sub-channel OFDM signals to output a combined OFDM signal that includes each of the sub-channel OFDM signals, the fast convolution and up-converter filtering each of the sub-channel OFDM signals and frequency shifting all of the sub-channel signals to respective designated frequencies within the combined OFDM signal. A corresponding receiver is also provided.

In a system having a plurality of cells participating in a Coordinated Multi-Point (CoMP) operation, a method for transmitting Reference Signals (RSs) to User Equipment (UE) includes generating, by Base Station (BS) included in each of the plurality of cells, a subframe including RSs for a UE located in the each of the plurality of cells, and transmitting the generated subframe to the UE by the BS. The RSs include RSs for channel measurement, and RSs for data demodulation, the plurality of cells are grouped according to frequency shift values applied to the RSs for channel measurement and RS allocation patterns are determined for two cells among the plurality of cells according to a predetermined rule.

Fiber, cable, and wireless data channels are typically impaired by reflectors and other imperfections, producing a channel state with echoes and frequency shifts in data waveforms. Here, methods of using OTFS pilot symbol waveform bursts to automatically produce a detailed 2D model of the channel state are presented. This 2D channel state can then be used to optimize data transmission. For wireless data channels, an even more detailed 2D model of channel state can be produced by using polarization and multiple antennas in the process. Once 2D channel states are known, the system turns imperfect data channels from a liability to an advantage by using channel imperfections to boost data transmission rates. The methods can be used to improve legacy data transmission modes in multiple types of media, and are particularly useful for producing new types of robust and high capacity wireless communications using non-legacy OTFS data transmission methods.

A wireless combination time, frequency and spectral shaping communications method that transmits data in convolution unit matrices (data frames) of N×N (N2), where generally either all N2 data symbols are received over N spreading time intervals (each composed of N time slices), or none are. To transmit, the N2 sized data frame matrix is multiplied by a first N×N time-frequency shifting matrix, permuted, and then multiplied by a second N×N spectral shaping matrix, thereby mixing each data symbol across the entire resulting N×N matrix (TFSSS data matrix). Columns from this N2 TFSSS data matrix are selected, modulated, and transmitted, on a one element per time slice basis. At the receiver, the replica TFSSS matrix is reconstructed and deconvoluted, revealing the data. The method can accommodate multiple users at once, can adapt to changing channel conditions, and is particularly useful for coping with channel impairments such as Doppler shifts.

The present invention relates to an apparatus for producing optical pulses of a desired wavelength. The apparatus includes an optical pulse source operable to generate input optical pulses at a first wavelength. The apparatus further includes a higher-order-mode (HOM) fiber module operable to receive the input optical pulses at the first wavelength, and thereafter to produce output optical pulses at the desired wavelength by soliton self-frequency shift (SSFS). The present invention also relates to a method of producing optical pulses having a desired wavelength. This method includes generating input optical pulses using an optical pulse source, where the input optical pulses have a first wavelength and a first spatial mode. The input optical pulses are delivered into an HOM fiber module to alter the wavelength of the input optical pulses from the first wavelength to a desired wavelength by soliton self-frequency shift (SSFS) within the HOM fiber module, thereby producing output optical pulses having the desired wavelength.

The present invention relates to optical heterodyne detection cavity ringdown spectroscopy. In one aspect the invention relates to an optical system (1) comprising a ring-down cavity cell (3) defining a resonant optical cavity, means for directing coherent light selected from the group consisting of continuous or quasi-continuous light into said optical cavity (8, 9, 10, 11, and 12), means for altering the resonant optical cavity so as to generate a frequency shift of the coherent light in the optical cavity (6, 7), means for coupling said coherent light into the optical cavity and means for decoupling the frequency shifted coherent light out of said optical cavity (5, 6, 7), means for optically combining (10, 11, 12) said decoupled frequency shifted coherent light with another portion of coherent light not in optical communication with the optical cavity and means for optical heterodyne detection (13) of the intensity of said combined light. A method for optical detection is also described as well as methods and apparatus for detecting a parameter of a sample.

Systems and methods for receiving an OFDM preamble without knowledge of channel characteristics are provided. An OFDM preamble signal with frequency shifted cyclic extensions is received. Taken together the cyclic extensions form a frequency shifted version of the OFDM preamble signal. Frequency offsets and timing offsets are estimated and corrected in an efficient manner using a simple concatenation approach in the time domain, followed by a summation of the OFDM preamble signal and the concatenation after a transformation of the OFDM preamble and the concatenation into the frequency domain. Phase errors in the frequency domain are estimated and corrected after FFT transformations of the received signals. A valid preamble is detected and additional parameters for receiving subsequently transmitted OFDM symbols in a channel are extracted from the OFDM preamble. The methods are computationally efficient and robust. Receiver implementations for performing the methods in a DVB receiver are disclosed.

An ultrasonic surgical dissection system and method that employs an ultrasonic waveform that provides improved dissection of tissue while simultaneously providing improved hemostasis is disclosed. The disclosed system provides an ultrasonic waveform that includes a carrier frequency that may be pulse modulated at a predetermined rate and / or duty cycle. Embodiments are presented wherein the disclosed system provides an ultrasonic waveform having a frequency modulated carrier frequency. Additionally or alternatively, the disclosed waveform may be amplitude modulated. In yet another embodiment, an amplitude modulation of the ultrasonic signal may be synchronized, at least in part, with a frequency modulation of the ultrasonic signal. The frequency modulation and / or amplitude modulation may include continuously variable modulations and / or substantially instantaneous transitions between a first frequency and a second frequency and / or a first amplitude and a second amplitude.

Computerized wireless transmitter / receiver system that automatically uses combinations of various methods, including transmitting data symbols by weighing or modulating a family of time shifted and frequency shifted waveforms bursts, pilot symbol methods, error detection methods, MIMO methods, and other methods, to automatically determine the structure of a data channel, and automatically compensate for signal distortions caused by various structural aspects of the data channel, as well as changes in channel structure. Often the data channel is a two or three dimensional space in which various wireless transmitters, receivers and signal reflectors are moving. The invention's modulation methods detect locations and speeds of various reflectors and other channel impairments. Error detection schemes, variation of modulation methods, and MIMO techniques further detect and compensate for impairments. The invention can automatically optimize its operational parameters, and produce a deterministic non-fading signal in environments in which other methods would likely degrade.

A method and a measurement apparatus are provided for determining the transition impedance between two electrode parts of a subdivided neutral electrode used in high-frequency surgery. These make it possible for the purely capacitive component of the transition impedance to be measured. For this purpose a resonant-frequency shift is measured, which occurs when a basic resonant circuit is expanded to an expanded resonant circuit by incorporating the two electrode parts into it in parallel. In particular, in order to determine the basic resonant frequency of the basic resonant circuit and / or the sample resonant frequency of the expanded resonant circuit, the phase shift between current and voltage is measured and the frequency is adjusted until current and voltage are in phase.

Under a known pressure is externally applied to a reference member to which an optical fiber is fixed, test light is allowed to enter the optical fiber, and at least one of a reference Brillouin measurement for determining a reference Brillouin frequency shift amount based on the Brillouin scattering phenomenon, and a reference Rayleigh measurement for determining a reference Rayleigh frequency shift amount based on the Rayleigh scattering phenomenon is performed. A Brillouin measurement coefficient or a Rayleigh measurement coefficient is determined from these calculation results. An optical fiber is fixed to a sample member, the volumetric change of which is unknown, and the same sample Brillouin measurement or sample Rayleigh measurement is performed to determine the frequency shift amount. The volumetric change of the sample member is determined from the sample Brillouin or the sample Rayleigh frequency shift amount, and from the Brillouin or the Rayleigh measurement coefficient.

A mode-locked laser with intracavity frequency conversion is disclosed. In one embodiment the conversion frequency is improved by reducing the temporal, spatial, or polarization overlap between pulses at the fundamental frequency and pulses at a frequency-shifted frequency.

An apparatus for repeating signals includes a receive antenna for receiving input signals, processing circuitry for processing the input signals to form repeated signals, and a transmit antenna for transmitting the repeated signals. The processing circuitry includes an adaptive digital filter configured to generate cancellation signals that are added to the input signals to cancel unwanted feedback signals from the input signals. A frequency shifting circuit adds a frequency shift to the input signals, after the addition of the cancellation signals, to form repeated signals that are frequency shifted from the input signals. A digital signal processor is coupled to the adaptive digital filter for digitally adapting the filter. The digital signal processor utilizes the frequency shift of the transmission signals to adapt the adaptive digital filter.

A method of modulating communications signals, such as optical fiber, wired electronic, or wireless signals in a manner that facilitates automatic correction for the signal distortion effects of echoes and frequency shifts, while still allowing high rates of data transmission. Data symbols intended for transmission are distributed into N×N matrices, and used to weigh or modulate a family of cyclically time shifted and cyclically frequency shifted waveforms. Although these waveforms may then be distorted during transmission, their basic cyclic time and frequency repeating structure facilitates use of improved receivers with deconvolution devices that can utilize the repeating patterns to correct for these distortions. The various waveforms may be sent in N time blocks at various time spacing and frequency spacing combinations in a manner that can allow interleaving of blocks from different transmitters. Applications to channel sounding / characterization, system optimization, and also radar are also discussed.

Aspects of a method and system for communicating via a spatial multilink repeater are provided. In this regard, a received signal may be frequency shifted to generate a plurality of repeated signals, wherein each repeated signal may be shifted by a different frequency with respect to the received signal. Each repeated signal may comprise one or more signal components and a phase and / or amplitude of each of the components may be controlled to control a directivity of the repeated signals. Each of the repeated signals may be generated by quadrature down-converting said received signal by mixing the received signal with a first LO signal pair, up-converting the down-converted signal by mixing it with a second LO signal pair, and adding or subtracting an in-phase portion and a quadrature-phase portion of the up-converted signal.

Wireless communications transceivers include a transmitter that is configured to selectively frequency shift and transmit portions of broadband information over multiple non-contiguous narrowband frequency bands / segments, each of which is too narrow to carry the broadband information. A receiver also is configured to receive and selectively frequency shift portions of broadband information from multiple non-contiguous narrowband frequency bands / segments, each of which is too narrow to carry the second broadband information. Broadband information thereby may be transmitted and received in a regulated communications environment, even though a given provider may only be assigned discontinuous frequency bands / segments, none of which is wide enough to carry the entire broadband information.

A method is described, which includes controlling a coordinated transmission between network control elements and terminals on resource elements, detecting whether a resource element includes a specific element, and selecting a resource element for the coordinated transmission, when it is detected that the resource element does not include a specific element. The application also describes some further aspects to improve a coordinated transmission such as a coordinated multipoint transmission is improved.

Systems and methods for receiving MIMO signals for testing and analyzing operation of MIMO communications devices. Examples of systems and / or methods for receiving MIMO signals include a measuring receiver with N RF paths consisting of N downconverters. Each downconverter achieves a frequency shift of the input MIMO signal equal to a shifting frequency of a first intermediate frequency (IF) plus a delta determined by the signal bandwidth multiplied by an integer number between 1 and N. The shifted N MIMO signals are combined to generate one combined analog MIMO signal. An analog to digital converter converts the combined analog MIMO signal to a stream of digital samples where the samples may be tested and analyzed with metrics on signals communicated in a MIMO environment. Example systems and method for receiving MIMO signals may also be implemented as a MIMO channel emulator such that samples generated by the ADC may be upconverted to output copies of the original signals to a receiver DUT, for example.

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.

Aspects of a method and system for inter-PCB communication utilizing a spatial multi-link repeater are provided. In this regard, a signal may be transmitted between printed circuit boards via one or more repeaters, wherein the repeaters may frequency shift received signals to generate repeated signals. Each of the repeated signals may be generated by quadrature down-converting said received signal by mixing the received signal with a first LO signal pair, up-converting the down-converted signal by mixing it with a second LO signal pair, and adding or subtracting an in-phase portion and a quadrature-phase portion of the up-converted signal. Each repeated signal may comprise one or more signal components and a phase and / or amplitude of each of the components may be controlled to control a directivity of the repeated signals. The repeater may reside on one of the plurality of printed circuit boards.

Apparatus and methods for fluorescence imaging using radiofrequency multiplexed excitation. One apparatus splits an excitation laser beam into two arms of a Mach-Zehnder interferometer. The light in the first beam is frequency shifted by an acousto-optic deflector, which is driven by a phase-engineered radiofrequency comb designed to minimize peak-to-average power ratio. This RF comb generates multiple deflected optical beams possessing a range of output angles and frequency shifts. The second beam is shifted in frequency using an acousto-optic frequency shifter. After combining at a second beam splitter, the two beams are focused to a line on the sample using a conventional laser scanning microscope lens system. The acousto-optic deflectors frequency-encode the simultaneous excitation of an entire row of pixels, which enables detection and de-multiplexing of fluorescence images using a single photomultiplier tube and digital phase-coherent signal recovery techniques.

An oversampled filter bank structure that can be implemented using popular and efficient fast filter banks to allow subband processing of an input signal with substantially reduced aliasing between subbands. Even subbands (SB0, SB2, SB4, . . . ) of an input signal (x(n)) are frequency-shifted (212, 1012, 1012′, 1012″) prior to analysis filtering (214, 214′, 214″) at a 2× oversampled filter bank, subband processing (240, 240′, 240″), and synthesis filtering (216, 216′, 216″). A subsequent frequency-shift (218, 218′) returns the even subbands to their original band positions. The odd subbands (SB1, SB3, SB5, . . . ) are delayed (252) to compensate for the processing time of the frequency shifting. Separate analysis (214, 214′) and synthesis (216, 216′) filter banks may be provided for the even and odd subbands, or common complex analysis (284) and synthesis (286) filter banks may be used. In another embodiment, the subbands are processed in four subband paths (Paths 0, 1, 2, 3), and 4× oversampling is used. A filter bank structure (1400) for 2-D data is also provided.