3995 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.

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 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.

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.

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.

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.

A communications system, such as part of a real-time location system, includes a transmitter that can be part of a location processor, tag emission reader or tag interrogator that generates a frequency shift key (FSK) modulated wireless communication signal representative of digital data and transmits the communications signal over a wireless communications channel. A receiver such as incorporated within a tag transceiver used in the real-time location system receives the FSK modulated communication signal. The receiver includes a circuit for calculating the magnitude of low and high tones of the FSK modulated communication signal and a threshold for amplitude shift keyed (ASK) channel data and FSK channel data to derive the digital data even in the presence of on-tone jammers in the communications channel.