37 results about "Spread spectrum radar" patented technology

A device for detecting a demodulated signal received by a spread spectrum receiver and converted into digital samples. The device is characterized by a matched filter for calculating the correlation between an incoming signal and at least one reference signal, an oscillator for generating a sampling frequency, and a sampling circuit for re-sampling the demodulated digital sample signal at the sampling frequency, which is such that the timing of samples of the references signals of the matched filter corresponds to the timing of a sample signal going from the sampling circuit to the matched filter. The device also includes a multiplier in which the sample signal is multiplied by a carrier replica generated locally before the sampling circuit or thereafter, to remove the carrier from the sample signal.

A system for sensing aircraft and other objects uses bistatic radar with spread-spectrum signals transmitted from remotely located sources such as aircraft flying at very high altitudes or from a satellite constellation. A bistatic spread spectrum radar system using a satellite constellation can be integrated with a communications system and/or with a system using long baseline radar interferometry to validate the digital terrain elevation database. The reliability and safety of TCAS and ADS-B are improved by using the signals transmitted from a TCAS or ADS-B unit as a radar transmitter with a receiver used to receive reflections. Aircraft and other objects using spread spectrum radar are detected by using two separate receiving systems. Cross-Correlation between the outputs of the two receiving systems reveals whether a noise signal is produced by the receiving systems themselves or is coming from the outside.

A spread spectrum communications system is provided for reducing the number of required matched filters to simplify the configuration associated with the reception. In a spread spectrum transmitter, a plurality of spread channel signals are synthesized by shifting their respective phases by a time sufficiently shorter than one symbol period. In a spread spectrum receiver, a plurality of spread code sequences are set one by one at a tap of a single matched filter in one symbol period in a time division manner to recover transmitted data.

A spread spectrum transmitter provides delays having different magnitudes to spread spectrum (SS) signals for a plurality of channels, and multiplexes the SS signals to generate transmission multiplex SS signal. A spread spectrum receiver calculates a partial correlation value between the transmission multiplex SS signal and spreading codes multiplied to the SS signals, multiplies the partial correlation values by a prescribed matrix prepared based on each orthogonal code sequence to calculate a plurality of orthogonal correlation values. The receiver identifies for a respective channel each parallel data sequence related in advance to an orthogonal code sequence whose orthogonal correlation value is a maximum, corrects delay differences of the parallel data sequences, and then performs sampling and parallel-serial conversion to obtain a serial demodulated data sequence.

The spread spectrum receiver employs circuits based on direct conversion techniques. These circuits enable realization of spread spectrum receivers of greatly reduced complexity and of much higher chip rates that can be implemented with the standard approach of a fully digital receiver. With these circuits, the digital processing is performed at the data symbol rate and not at a multiple of the chip rate that is customary in state-of-the art spread spectrum and CDMA receiver design.

An automotive spread MIMO-configured radar system has a plurality of transceiver antenna units for transmitting mutually orthogonal radar waves. Each transceiver antenna unit has a plurality of range gates to indicate a range detected by the transceiver antenna unit. At least one specific transceiver antenna unit (TRx₁) is configured to transmit a reference signal received directly by at least one transceiver antenna unit (TRx₂) that is separated by an a priori known distance from the specific transceiver antenna unit (TRx₁). An evaluation and control unit is configured for reading out the plurality of range gates for the transceiver antenna unit (TRx₂), and, based on the read-out range gate that indicates the received reference signal and based on the a priori known distance, for synchronizing the specific transceiver antenna unit (TRx₁) and the transceiver antenna unit (TRx₂) that received the reference signal and/or for correcting a measured Doppler shift.

A method of direction of arrival estimation with an automotive spread radar system. The automotive spread radar system includes a plurality of at least two transceiver antenna units, which are configured to work in a MIMO configuration, wherein the transceiver antenna units are arranged at a priori known positions. The automotive spread radar system is configured to determine, for each transceiver unit antenna unit of the plurality of transceiver antenna units, a range of a target reflecting radar waves that have been transmitted by at least the specific transceiver antenna unit by reading out a plurality of range gates assigned to a specific transceiver antenna unit. The method and radar system are capable of estimating a direction of arrival without the need of ensuring a synchronization of antennas on the scale of a radar carrier frequency.

A fraction chip correlation device for a spread spectrum receiver for receiving signals modulated with spread spectrum codes and a method for operating fractional chip correlation to spread spectrum signals received by the spread spectrum receiver are disclosed. In the present invention, at least one delayed version of an input signal is generated to be correlated with a local code replica to accomplish fractional chip correlation. By doing so, correlators can operate at a low speed, so that power consumption of the receiver can be significantly reduced.

Disclosed is a method for acquiring a user signal from among several received from multiple users in a single burst. The method includes receiving a plurality of user signals in a single transmission burst, suppressing multiuser interference among at least some of the plurality of received signals, and determining a carrier frequency of at least one signal from among the interference suppressed plurality of received signals. Said signals may rotate due to a lack of synchronization while being equalized. Also described is a multiuser receiver for acquiring at least one user signal from among several user signals received from multiple users in a single burst. An antenna is for receiving a plurality of user signals in a single spread spectrum transmission burst, a matched filter is for despreading the signals, a multiuser equalizer is for suppressing mutual interference among at least a portion of the plurality of user signals, and a carrier lock circuit is for determining a carrier frequency of at least one user signal of the portion.

The invention discloses a spread spectrum clock generation device. The device comprises that a monitoring module is used for monitoring the depth of a first in first out FIFO memory and feeding back the depth of the FIFO memory to a spread spectrum clock generator SSCG; the FIFO memory is used for caching data; the SSCG is used for receiving first clock signals and the depth of the FIFO memory fed back by the monitoring module; the frequency division number of the SSCG is adjusted according to the depth of the FIFO memory, thus obtaining the adjusted frequency division number; carrying out spread spectrum to the first clock signals according to the adjusted frequency division number, thus generating spread spectrum clock signals; through monitoring the depth of the FIFO memory in real time, continuously adjusting the frequency division number of the spread spectrum clock generator SSCG according to the depth of the FIFO memory and generating the spread spectrum clock signals according to the adjusted frequency division number, the center frequencies of the spread spectrum clock signals in different time periods alternately generate high or low conditions; and further the center frequencies of the spread spectrum clock signals in the whole time period is kept stable.

On-chip spread spectrum characterization including obtaining, from a skitter circuit, skitter data comprising a spread width corresponding to an amplitude of a spread of a spread spectrum clock signal; setting an offset pointer to a center of the spread width corresponding to the amplitude of the spread; retrieving, for each of a number of reference clock cycles, edge data indicating a location, within the spread width, of an edge of the spread spectrum during the reference clock cycle; incrementing, using the edge data, an offset counter for each reference clock cycle during which the edge of the spread spectrum crosses the offset pointer; and calculating a frequency of the spread spectrum using the offset counter and the number of reference clock cycles.

The spread spectrum radar apparatus in the present invention (i) includes: a transmission code generator (110); a reception code generator (121) generating a reception code obtained by delaying a transmission code; a spread modulator (112) spread-modulating a signal generated by a local oscillator (111) using the transmission code; a transmission antenna (113) transmitting the spread-modulated signal; a reception antenna (120) receiving a signal; a spread demodulator (122) demodulating the signal using the reception code to provide a correlation signal; a mixer (123) mixing the correlation signal and the signal generated by the local oscillator (111) to generate a radar signal; a virtual image determining unit (130) determining a virtual image; and a radar signal calculation device (160) calculating the radar signal using a virtual image determination signal, and (ii) adds a calculation and an offset signal for suppressing a peak intensity of the virtual image when the virtual image occurs.

The invention discloses a signal spread spectrum control method and system. Based on the method provided by the invention, center frequency and a duty ratio meeting requirements are output at last byconfiguring the center frequency, a spread spectrum mode, a spread spectrum depth, a spread spectrum step length, adjustment speed and other parameters in an automatic spread spectrum unit, digital spread spectrum is performed before an interface PWM signal outputs a certain frequency signal, thereby avoiding performing spread spectrum on a clock oscillation generator at the clock source, so thatthe design cost of the spread spectrum is reduced, and the stability of the system is improved.

The invention discloses a coherent spread spectrum communication system. The system is composed of a spread spectrum transmitter and a spread spectrum receiver. The spread spectrum transmitter uses an orthogonal spread spectrum code to modulate a data code. Another orthogonal spread spectrum code is further added. Baseband signals after the addition are modulated to a medium-frequency carrier wave and further radiated out through an up-conversion channel and a transmitting antenna. The spread spectrum receiver uses an antenna to receive a radiofrequency signal which undergoes down conversion through a down conversion channel and is converted into a medium frequency one. The medium-frequency signal passes through two matching filters. The impulse responses of the two matching filters are respectively the arithmetic products of the opposite sequence of each orthogonal spread spectrum code and the medium-frequency carrier wave. After output signals of the two filters are multiplied, the signals then pass through a low pass filter. Absolute value taking operations and symbol taking operations are respectively performed on an output signal of the low pass filter. An absolute value taking operation output signal undergoes threshold decision. When a threshold value is exceeded, it shows that a pseudo code is captured. A symbol taking operation output signal is then a data signal after a demodulation process.

The invention relates to a spread spectrum communication method based on a chaotic spread spectrum sequence. At a transmitting end, target information is converted into a binary sequence serving as a signal source; a length N of a spread spectrum sequence is determined according to information of the signal source and is greater than or equal to that of the signal source; under the conditions that gamma belongs to a set from 1.5 to 2 and x0 belongs to a set from -1 to 1 and is not equal to 0, +0.5 and -0.5, iteration is gradually executed for N times, so that a simulation real value sequence {x1, x2, ..., xi, ..., and xN} with the length of N is obtained; the information of the signal source is subjected to baseband modulation and then binary sequence modulation produced in the step 4, so that a spread spectrum is obtained; at a receiving end, the target information is obtained through relevant demodulation. Compared with the prior art, the spread spectrum sequence produced by the method is uniform in distribution, high in randomness, and the spread spectrum sequence is relatively sensitive to an initial value; a chaotic state can be quickly realized, and the chaos degree is relatively high; and therefore, the security, the reliability and the completeness of the information in a spread spectrum communication process are guaranteed.

The invention provides a waveform design method of an expanding zero-correlation zone; the method includes steps of forming a zero-correlation sequence by applying an initial regular base sequence generating method, introducing a spread spectrum radar polyphase code sequence to perform Kronecher multiplication with the zero-correlation sequence, so that the final sequence has quasi-perfect self-correlation property and perfect cross-correlation property within a certain zone, and has a larger zero correlation zone; thereby effectively reducing the mutual influence of the echo of adjacent distance units and improving the target detecting precision.