摘要:
Techniques to reduce signal amplitude peak-to-average ratio (PAR) in a wireless communications system are described. The apparatus may include a signal conditioning module to receive a baseband signal. The signal conditioning module may split the baseband signal along multiple paths, delay one or more of the paths, and combine the multiple paths to form a conditioned signal having lower signal amplitude PAR than the baseband signal. Other embodiments are described and claimed.
摘要:
A system and method for noise cancellation is disclosed herein generally having at least one microphone, a processor, and a speaker array. The processor may contain an adaptive filtering feature, to separate desirable sound from undesirable sound. The undesirable sound may be suppressed by the processor by creating a canceling waveform and transmitting the canceling waveform to the user's head via a speaker array. The desirable sound may be enhanced by increasing the amplitude of the waveform and transmitting the amplified waveform to the user's head via a speaker array. The sound transmitted to the user's head by the system may be localized using an image tracking subsystem and speaker array. The image tracking system may track the actual visible image or alternatively a heat (e.g. infrared) image of the user's head.
摘要:
An apparatus provides an optical wavelength division multiplexed signal having 2M optical channels such that each of M information-bearing signals are differentially encoded onto 2 of the 2M optical channels. In particular, the apparatus comprises M inverters, 2M electrical-to-optical converters and a multiplexer. Each electrical-to-optical converter provides an optical signal at a different one of 2M wavelengths. The apparatus receives the M information-bearing signals and (a) creates M optical signals, each at a different wavelength, by converting each of the M information bearing signals into the optical domain via M of the 2M electrical-to-optical converters, and (b) creates M inverted optical signals, each at a different wavelength, by first inverting each of the M information bearing signals (via the M inverters) before conversion into the optical domain via the remaining M electrical-to-optical converters. The M optical signals along with the M inverted optical signals are then applied to the multiplexer, which provides an optical wavelength division multiplexed (WDM) signal having 2M channels.
摘要:
A method and apparatus are disclosed for frequency offset estimation and interleaver synchronization, using periodic signature sequences, such as Barker codes. The periodic signature sequence is used for interleaver synchronization or frequency offset estimation or both. The periodic signature sequence is transmitted over a certain number of bins in both the upper and lower sides of the DAB signal. Since the signature sequences are assigned to specific bins known to the receiver, any shift of the correlated peak from the expected location due to frequency offset errors can be estimated by the frequency offset algorithm. If the Barker sequence is placed, for example, in the last column of the DAB interleaver, the location of the Barker sequence upon correlation of the received digital signal identifies the beginning of an interleaver block. A Barker sequence is transmitted over a signature frame every L data frames on each side band, where L is generally the number of OFDM frames that can fill the interleaver memory. If the maximum frequency offset is M, then the frequency offset algorithm utilizes a search window of size n+2M (between bins N−M through N+n+M), and attempts to maintain the Barker sequence in the center of the search window. At the receiver, the Barker sequence is mapped to the OFDM signature bins that do not belong to uncertainty regions (the group of bins that can fall out of the receiver processing range for maximum positive and negative frequency offset values). Thus, the Barker sequence bins are processed by the disclosed receiver as long as the frequency offset does not exceed the specified maximum frequency offset.
摘要:
A novel antenna diversity technique for OFDM receivers is disclosed. A method and apparatus are disclosed for combining in the frequency domain the various signals received on each of the multiple antennas in an OFDM communication system. At the OFDM transmitter, the transmitted signal is differentially encoded over frequency, as opposed to time, to differentially encode the transmitted signal in the frequency domain with respect to consecutive bins (OFDM sub-carriers). The OFDM receiver processes a signal received on a number of diversity branches and combines the received signals using a post-detection combining technique after differential decoding. Each frame is independently processed by a differential decoder and then delayed to align each symbol in a given frame. The post-detection combining of the frame data inherently scales the received samples and thereby implements an optimal maximum ratio combining mechanism. Unlike conventional maximum ratio combining techniques, the faded bins are scaled individually by the differential decoder, based on their own power levels rather than the overall power of the OFDM frame. Thus, bins with higher magnitudes will be weighted more heavily than bins having severe channel fading.
摘要:
A transmission system encodes blocks of source data with error correction codes and spreads encoded data for each source block over a range of time and frequencies. This has the effect of reducing the impact of flat fading. This is because if a portion of the encoded data corresponding to a block of source data is lost, as a result of flat fading during a time interval, other portions, transmitted at a different time, may not be affected. A receiving system may therefore recover the original block of source data based on the portions of the encoded data that were received, including error correction bits. The transmission and receiving systems may be orthogonal frequency division multiplexed (OFDM) communications systems.
摘要:
A target receives two signals of different modes in association with a first location and another two signals in association with a second location. The first two signals are assumed to have been emitted effectively simultaneously from the first location, and the second two signals are assumed to have been emitted effectively simultaneously from the second location. A first distance is calculated in view of a receipt time difference of the first two signals in view of differing rates of propagation assumed between these two signals; a second distance is calculated in view of another receipt time difference of these second two signals in view of differing rates of propagation assumed between each of these other signals. A possible location of the target is then calculated in view of the first distance and its associated first location and the second distance and its associated second location.
摘要:
Circuits, systems and methods that utilize two transducers, of which at least one is a piezoelectric transducer, adapted and coupled to receive and/or generate signals that include a power transmission component and an informational content in the forms of sound waves, mechanical vibrations, and/or electromagnetic energy. In one version, two transducers each receive and/or generate separate vibrational energy signals that bear information and transmit electrical power. Two or more transducers coupled to a switching circuit may send or receive piezo-electrical circuit output signals that include a carrier wave having different frequencies that are within separate frequency ranges. Two or more transducers may generate output signals that are simultaneously processed by or multiplexed by a switching circuit.
摘要:
Circuits, systems and methods that utilize two transducers, of which at least one is a piezoelectric transducer, adapted and coupled to receive and/or generate signals in the forms of sound waves, mechanical vibrations, and/or electromagnetic energy. In one version, two transducers each receive and/or generate separate vibrational energy signals that bear information. Two or more transducers coupled to a switching circuit may send or receive piezo-electrical circuit output signals that include a carrier wave having different frequencies that are within separate frequency ranges. Two or more transducers may generate output signals that are simultaneously processed by or multiplexed by a switching circuit.
摘要:
A system and method for digital watermarking a video signal with an increased bit rate is achieved by inserting the additional information which constitutes the watermarking signal within the video signal on the chrominance signal. Thus, the additional information is “impressed” upon the chrominance component of the video signal. The human visual system is much less sensitive to chrominance than to luminance, and therefore, additional distortion which results from the higher bit rate can be allowed on the chrominance signal and yet such distortion will not be detected by the human visual system.