70 results about "Barker code" patented technology

A receiver for a wireless local area network, WLAN, having a low power listening mode of operation. The receiver includes two separate paths in the analog front end, AFE. One path includes a low resolution and low power analog to digital converter, ADC. The other path includes a high resolution and high power ADC. In listen mode, only the low resolution ADC is powered and provides inputs to a packet detector for identifying a barker code. When the correct barker code is received, the high resolution ADC is enabled and coupled to a receiver for receiving a payload in the data packet.

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.

Very efficient sidelobe suppression of Barker codes is achieved through the use of a mismatched filter, which is comprised of a conventional matched filter cascaded with a computationally efficient filter based on multiplicative expansion. Several constant parameters are introduced in the terms of the expansion and are optimized to improve the performance of the filter. Optimized mismatched filters for length 13, 11, 7 and 5 Barker codes are presented. For each of these codes, filters with one, two and three stages are studied. The technique is extended to compound Barker codes based on their representation in a factored form in the z-domain. Hardware requirements for the filters discussed in the disclosure are also presented.

A transmitter and a transmitting method in a code division multiplexing (CDM) wireless communication system are provided. The transmitter includes a DC offset unit, a Barker code generating unit, a multiplier, a unipolar code generating unit, a Kronecker product unit, and a modulator. The DC offset unit transforms digital transmitting data to bipolar data, and the Barker code generating unit generates a Barker code. The multiplier multiplies the bipolar data with the Barker code and outputting the multiplying result, and the unipolar code generating unit generates a predetermined unipolar code. The Kronecker product unit multiplies the multiplying result from the multiplier and the unipolar code based on the Kronecker product, and outputs the result thereof, and the modulator modulates the output of the Kronecker produce unit through the On-Off keying modulation scheme.

The invention discloses a method for generating periodic polyphase complementary sequence sets, which comprises the following steps of: continuously sampling perfect sequences at an equal interval to obtain a group of subsequences; and combining the subsequences in the group to obtain the periodic polyphase complementary sequence sets, wherein the summation of periodic autocorrelation functions of all the subsequences has impulse characteristics; the number of the obtained complementary sets is the same as that of the adopted perfect sequences; and the lengths and number of the subsequences can be regulated in real time and selected flexibly according to the needs of actual factors. The method can be used for realizing the application of multi-access interference-free transmission of communication systems, channel estimation, the synchronization of the communication systems, reduction in a peak-to-average power ratio (PAPR), the design of other signals (such as quasi-barker codes, low / zero-correlation zone sequences and the like), and the like.

In a code division multiple communication system which prevents the dropout of a whole packet and does not require the generation of a carrier from a received signal, under bad communication path, by generating an orthogonal code with chip synchronization from a correlation peak of a synchronization code sequence output from a surface acoustic wave matched filter, a preamble division of a spectrum spread signal is composed of plural synchronization burst. Each synchronization burst is composed of a synchronization packet division having the Barker code of 11 chips and a dummy division. The period of one synchronization burst (Tburst) is set equally to the period of one symbol in a data division (Tsymbol) which is modulated by the orthogonal sequential code of 64 chips. When the correlation peak of at least one from among plural synchronization code sequences is detected, the orthogonal code can be generated in accordance with the start timing of the first symbol in the data division.

Electronic circuitry for high-power, high-frequency excitation of electromagnetic acoustic transducers (EMAT) without the use of a matching transformer is described. This circuit contains a least 4 switching devices such as power Mosfet transistors, arranged in an H-Bridge configuration that are designed to drive various EMATs over a wide range of frequencies. The switching devices can be connected in parallel with respect to the H-Bridge and switched in sequence for greater power output and variety of wave forms. This circuit configuration can provide a many excitation waveforms including, Churp, Hemming window tone burst, rectangular tone burst and Barker Code wave forms.An improved electronic pulser circuit based on the H-bridge topology is designed for driving the sensor coils of an electromagnetic acoustic transducer (EMAT) to correct the disadvantages of conventional H-bridge pulsers and pulsers that require the use of an output transformer. A plurality of switching devices, primarily power Mosfets, are connected in parallel and augmented with support circuitry to provide improved performance in terms of increased power output, stability, reduced noise and complex output wave forms. This improved design provides for the application of modulated pulses such as multi-pulse, multi-frequency tone bursts of peak power outputs in excess of 20 thousand watts and frequencies in excess of 10 thousand Hertz.

A method (and algorithm) for detection of 802.11a and 802.11b frames in an 802.11 transmission, calculates DCC (delayed copy correlation) and LCC (local copy correlation) magnitudes and compares their normalized values with threshold values. When a signal is detected, (i.e., AGC locks) the algorithm checks for a valid 802.11a frame, and it exploits the DCC properties of the received symbols. Because of the repetitions of short preambles in received symbols, the DCC is high when the short preamble symbols are present. Further, 802.11b detection may be based on Barker correlation properties simultaneously. A counter array is maintained for each position in a Barker window, and is incremented if the normalized LCC of the incoming sequence with the Barker code exceeds a threshold. An 802.11b packet is declared if the maximum value of the counter array exceeds a predetermined number in a specified number of Barker windows.

The invention discloses a radar target detecting method, relates to a radar detection technology, and aims to provide a radar detecting method with both high range resolution and high velocity resolution for the condition that a conventional radar detecting technology which adopts a single waveform cannot simultaneously solve the problems of range ambiguity and velocity ambiguity. The radar target detecting method disclosed by the invention mainly comprises the following steps of: a step 1 of transmitting a radar wave signal, wherein the radar wave signal comprises m pulses, each pulse has a repetition period of T, each pulse is a radar wave pulse comprising k linear frequency modulation sub-pulses and a k-bit barker code or a combined barker code is formed by the k linear frequency modulation sub-pulses of each pulse; a step 2 of receiving an echo; a step 3 of judging whether a radar target is detected, executing a step 4 if yes, and repeating the steps 1 to 3 if the radar target is not detected; and the step 4 of determining a target distance and a moving velocity according to a radar echo signal.

An interwoven spreading code is formed by a stretched spreading code series at a first frequency and a mirror of the stretched spreading code series at a second frequency. The interwoven spreading code can be used to spread a baseband signal. Data can be recovered through correlation of a received signal with the interwoven spreading code. The spreading code used in forming the interwoven spreading code can be a Barker code.

A method for removing direct current (DC) interference from a signal received by a communication receiver is provided that removes both a DC offset signal induced by the communication receiver and transmitter. The method includes removing the estimated DC offset from the received signal, correcting a frequency shift in the received signal, estimating a second DC offset signal induced by a source of the received signal, such as a transmitter and removing the estimated second DC offset from the received signal. The receiver DC offset signal is estimated and removed prior to performing a timing carrier offset correction using Barker code manipulation to remove receiver-induced DC offset interference and to sum all Barker chips after effectively multiplying Barker codes to correlate to a Barker sequence unaffected by the receiver DC offset signal.

The invention discloses a detecting device based on combined barker code burst pulses. The device comprises a sub-pulse generation unit, a pulse combination unit, a pulse compression unit, a transmission unit, a receiving unit and a processing unit, wherein the sub-pulse generation unit is coupled with the pulse combination unit; the pulse combination unit is coupled with the sub-pulse generation unit and the pulse compression unit; the pulse compression unit is coupled with the pulse combination unit, the transmission unit and the processing unit; the transmission unit is coupled with the pulse compression unit; the receiving unit is coupled with the processing unit; and the processing unit is coupled with the receiving unit and the pulse compression unit. The device provided by the invention solves the problem that the conventional detecting device cannot eliminate fuzzy distance and fuzzy speed at the same time.

The invention discloses a transmitting device of an ultrasonic diagnostic equipment, including a transmitting control unit and a transmitting drive unit which is connected with the transmitting control unit, the transmitting control unit is used for the output of the Barker code pulse signal, the transmitting drive unit is used for amplifying the input Barker code pulse signal and the output of the high-voltage Barker code pulse signal. The transmitting device of the ultrasonic diagnostic equipment of the invention adopts the Barker code rather than the simple pulse as the incentive signal of an ultrasonic sensor, as the Barker code has the nature of an acute autocorrelation function, the higher signal-to-noise ratio is obtained and the resolution of the ultrasound image is improved; at the same time, the invention adopts the single transmission method, which also ensures the high frame rate of the ultrasound image.

The invention provides a high-performance anti-collision surface acoustic wave delay line type wireless sensor system. A transponder sensing chip input transducer is a code interdigital transducer (input dependence transponder), the codes of the transponder sensing chip input transducer are compatible codes which belong to the same compatible code group, and a transponder which adopts the same compatible code encoding chip is called a similar transponder. The transponder sensing chip is provided with at least two same-frequency output dependence transducers arranged along a sound track, and the preferable codes of the transponder sensing chip are barker codes. The starting delay distances of the first output transducers and the input transducers of different similar transponder chips are mutually different; intervals among all output transducers are consistent; and a design causes all echo peaks to be distinguished by a reader after electromagnetic echoes simultaneously generated by the similar transponders are overlapped within a test range of a nominal sensing amount. The reader is provided with a compatible code generation component and barker code demodulation component. The anti-collision function of the system is equal to a value obtained by that the number of different types of transponders is multiplied by a time sequence capacity.

At sending end, a PN sequence is repeated for multiple times continuously. The training sequence is constituted after positive and negative polarities of front some segments of PN sequence are determined by barker code. Emission data are constituted by weighted addition in point to point between the said training sequence and OFDM original data. At receiving end, sectional correlation calculation with barker code as weight value is carried out so as to obtain objective function value utilized to evaluate point of time synchronization. The point making the objective function value exceed prearranged threshold is a point of time synchronization. The method possesses advantages of fast synchronization speed and simple implementation, suitable for synchronization of OFDM system under packet transmission.

Methods, system and apparatuses for carrier frequency offset estimation are disclosed. The method includes: receiving a preamble sequence rn with a correlator and correlating the preamble sequence with a locally stored Barker code bn to obtain a correlation result cn; extracting peak values from every L points in cn to form a peak value sequence xn, L being a length of a Barker code that corresponds to the sampling rate; performing frequency offset estimation to xn by using at least two frequency offset estimation apparatuses, the at least two frequency offset estimation apparatuses adopting different delay parameters D; and inputting the results output from the at least two frequency offset estimation apparatuses into a frequency offset combination module to calculate a final carrier frequency offset estimate, whereby accurate frequency estimation can be achieved and an appropriate acquisition range of frequency offset can be ensured.

The invention discloses a pulse accumulation frame based dual frequency velocity ambiguity resolution method and system. The system includes an emission subsystem and a receiving subsystem; a basebandsignal generation module generates a Barker code or a chirp signal to output to a microwave transmitting module, and the microwave transmitting module performs frequency mixing on the received baseband signal to modulate to a microwave frequency band, and outputs the microwave frequency band to an external antenna to radiate into space after power amplification; a microwave receiving module converts an echo signal input by a receiving antenna from the microwave frequency band into intermediate frequency, and outputs the intermediate frequency to an intermediate frequency receiving module to perform intermediate frequency signal gain control, so that the intermediate frequency signal amplitude level output to a signal processing module can be controlled within an appropriate range; and thesignal processing module adjusts pulse repetition rates between frames according to the types of pulse accumulation frames, alternatively accomplishes the velocity measurement frame accumulation of high repetition frequency and the velocity measurement frame accumulation of low repetition frequency, generates corresponding synchronous pulses to output to other modules, and completes signal acquisition, pulse compression accumulation and target detection functions as well.

The base station transmits a synchronization signal that contains a pattern of repeated SYNC's generated by dividing FFT size by N wherein the pattern of repeated SYNC's is inverted in polarity for each of the SYNC's according to a code outputted from a code generating circuit. CP length is M / N of FFT size, and the number of divisions (M+N) of a symbol of the synchronization signal is brought into agreement with the code length L of Barker code. The mobile station detects the synchronization signal by using a first matched filter that has as many taps as (FFT size / N) stages, and uses a pattern of SYNC's generated by dividing FFT size by N as a tap coefficient, and a second matched filter that has as many taps as (M+N) stages and uses Barker code as a tap coefficient.

The invention discloses a sound wave communication system on the basis of OFDM (orthogonal frequency division multiplexing). The sound wave communication system includes that at a sound wave transmission end, original data are modulated into sound wave signals of a data frame composed of a plurality of OFDM symbols after channel coding, and the sound wave signals are transmitted through a loudspeaker; at a sound wave receiving end, a microphone receives the sound wave signals and the sound wave signals are subjected to demodulating and channel decoding and restored into the original data. During communication, the symbols are synchronized by pilot frequency information, the data frames are synchronized by inserting barker codes, processing is simplified, bit error rate is low, efficiency of sound wave communication is improved, the sound wave communication is developed, and the sound wave communication method has good application prospect.

Using corrective grouping bit sequence output from demodulator, the invented technique is completed through decision module in frame synchronization. Synchronous code is composed of 7 bits barker code. Data at sending end are sent according to frame. Frame synchronization code group and data frame start-up word are inserted in front of each data frame, which is modulated and then sent to channel. Serial-parallel conversion is carried out at receiving end. Hardware sends each word received at the receiving end to decision module in frame synchronization for further processing. The decision module in frame synchronization is controlled by specific mathematic mode. The invention combines hardware with software, providing features of simple circuit, reliable synchronization, small program size and less resources needed. Good fault tolerant capability is kept under low S / N ratio. It is easy to modify and upgrade software. Thus, the invention raises quality and security greatly.

An interwoven spreading code is formed by a stretched spreading code series at a first frequency and a mirror of the stretched spreading code series at a second frequency. The interwoven spreading code can be used to spread a baseband signal. Data can be recovered through correlation of a received signal with the interwoven spreading code. The spreading code used in forming the interwoven spreading code can be a Barker code.

The invention discloses a signal frame generating method of a power line carrier wave communication system based on OFDM, synchronous signal frames and control signal frames in signal frames are all obtained by modulating linear frequency modulation signals with pseudo random sequences or barker codes or truncation codes of the pseudo random sequences and the barker codes as modulation signals. As the pseudo random sequences and the barker codes have good dependency and the linear frequency modulation signals also have good self-correlation and cross-correlation performance, generated synchronous signals and control signals also have good dependency, and the synchronous signals have the function that data symbols of a receiving terminal and data symbols of a sending terminal are accurately synchronized. The control signals also have good dependency, so that the receiving terminal can accurately demodulate the current control type of the corresponding system after receiving the control signals, and the signal frames obtained through the method is high in whole accuracy, has constant envelope amplitude and are strong in anti-noise performance. Meanwhile, the frequency band ranges of the synchronous signals and the control signals can be adjusted conveniently, namely the frequency band range of the signal frames is adjustable.

The invention relates to the technical field of ground end VDES signal detection. The invention provides a VDES satellite receiver frame header detection method and system, and the method comprises the steps: S1, carrying out the preprocessing of a received signal, constructing a periodic sequence through employing the double-Barker code characteristics in a frame structure of a ground end VDES signal, and forming a preprocessed signal; S2, performing Fourier transform on the preprocessed signal, based on the periodicity of the preprocessed signal, a peak value appears in a specific position of a transformed sequence, performing constant false alarm rate detection of the ground end VDES signal, and detecting the ground end VDES signal; S3, performing multiple times of constant false alarmrate detection, and when multiple times of ground end VDES signals are continuously detected, considering that the detected ground end VDES signals exist. The method has the technical characteristic of constant false alarm rate detection, and is beneficial to non-coordinated communication signal investigation of a satellite receiver.

The invention discloses a sound wave communication method on the basis of OFDM (orthogonal frequency division multiplexing). The sound wave communication method includes steps of modulating original data subjected to channel coding into sound wave signals of a data frame composed of a plurality of ODFM symbols, transmitting the sound wave signals via a loudspeaker, subjecting the sound waves received by a microphone to demodulating and channel decoding to restore the original data. During communication, the symbols are synchronized by pilot frequency information, the data frames are synchronized by inserting barker codes, processing is simplified, bit error rate is low, efficiency of sound wave communication is improved, the sound wave communication is developed, and the sound wave communication method has good application prospect.