588 results about "Digital down conversion" patented technology

A method and apparatus provides OFDM signal compression for transfer over serial data links in a base transceiver system (BTS) of a wireless communication network. For the uplink, an RF unit of the BTS applies OFDM cyclic prefix removal and OFDM frequency transformation of the baseband signal samples followed by frequency domain compression of the baseband signal samples, resulting from analog to digital conversion of received analog signals followed by digital downconversion, forming compressed coefficients. After transfer over the serial data link, the baseband processor applies frequency domain decompression to the compressed coefficients prior to further signal processing. For the downlink, the RF unit performs frequency domain decompression of the compressed coefficients and applies OFDM inverse frequency transformation of the decompressed coefficients and OFDM cyclic prefix insertion prior to digital upconversion and digital to analog conversion, generating the analog signal for transmission over the antenna.

A method and apparatus provide signal compression for transfer over serial data links in a base transceiver system (BTS) of a wireless communication network. For the uplink, an RF unit of the BTS applies frequency domain compression of baseband signal samples, resulting from analog to digital conversion of received analog signals followed by digital downconversion, forming compressed coefficients. After transfer over the serial data link, the baseband processor then applies frequency domain decompression to the compressed coefficients prior to normal signal processing. For the downlink, the baseband processor applies frequency domain compression of baseband signal samples and transfers the compressed coefficients to the RF unit. The RF unit applies frequency domain decompression to the compressed coefficients prior to digital upconversion and digital to analog conversion, generating the analog signal for transmission over the antenna. This abstract does not limit the scope of the invention as described in the claims.

A signal compression method and apparatus for a base transceiver system (BTS) in a wireless communication network provides efficient transfer of compressed signal samples over serial data links in the system. For the uplink, an RF unit of the BTS compresses baseband signal samples resulting from analog to digital conversion of a received analog signal followed by digital downconversion. The compressed signal samples are transferred over the serial data link to the baseband processor then decompressed prior to normal signal processing. For the downlink, the baseband processor compresses baseband signal samples and transfers the compressed signal samples to the RF unit. The RF unit decompresses the compressed samples prior to digital upconversion and digital to analog conversion to form an analog signal for transmission over an antenna. Compression and decompression can be incorporated into operations of conventional base stations and distributed antenna systems, including OBSAI or CPRI compliant systems.

A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200, 1800, 2800) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Distortion introduced by an analog-to-digital converter (304) may be compensated using a variety of adaptive techniques. Linear distortion is compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

The invention relates to a detection method of standing-wave ratio of a time division duplex communication system, which comprises the following steps: a forward signal is sampled by switching a switch at a time interval of standing-wave ratio measurement; a reverse signal is sampled by switching the switch at the next time interval of standing-wave ratio measurement; the forward and the reverse signals is coupled and delivered to a digital-to-analog converter through a coupling passage, the delivered signal is sampled and quantized by using an AD sampler and processed by means of digital down-conversion to obtain a sampled data of baseband; a reflection coefficient |gamma_AD| is obtained by calculating, the transmission characteristic difference CF_R(Omega 0) between a forward detection channel and a reverse detection channel is obtained at the current frequency after table lookup process; and the standing-wave ratio VSWR is calculated based on the reflection coefficient |gamma_AD| and the transmission characteristic difference CF_R(Omega 0). Therefore, the invention realizes the multiplexing of a normal reception channel and the reverse and the forward standing-wave ratio channels, enables the normal reception channel to be used in standing-wave ratio detection, and ensures the equivalency of front/reverse power samplings by measuring the front and the reverse powers of the pilot frequency.

A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Linear distortion is first compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).

The invention discloses a signal acquisition system and a signal acquisition method for a satellite navigation receiver so as to realize compatible processing of a plurality of GNSS satellite signals. The system comprises a channel parameter control list, a data storage, a digital down-conversion and down-sampling module, and a related energy accumulation and signal acquisition module, wherein the channel parameter control list stores control parameters and state parameters of a plurality of logical channels; the data storage stores intermediate-frequency sample data of satellite signals received by the receiver according to the control parameters; the digital down-conversion and down-sampling module performs digital down-conversion and down-sampling operation on the intermediate-frequency sample data according to the control parameters and the state parameters to acquire satellite sample data with zero intermediate frequency and low sample rate; and the related energy accumulation and signal acquisition module completes satellite signal despread, related energy accumulation, and signal acquisition and output according to the control parameters and the state parameters.

The invention discloses a high-sensitivity satellite navigation signal capturing method and a system. The system comprises a digital down-conversion module, an average sampling and block accumulation module, an FFT (fast Fourier transform) module, a circumference shifting module, a local PRN (pseudo random noise) code FFT conjugate memory, a complex multiplier module, an IFFT (inverse fast Fourier transform) module, a differential coherence integration module, a peak detection module and a sequential control module. The digital down-conversion module realizes digital down-conversion operation for satellite digital intermediate frequency signals; the average sampling and block accumulation module averagely samples satellite data and completes a block accumulation function; the FFT module searches code phase frequency domains; the circumference shifting module utilizes Doppler circumference shifting search to replace frequency compensation; the local PRN code FFT conjugate memory stores a local PRN code FFT conjugate result; the complex multiplier module realizes signal de-spreading; the IFFT module calculates different code phase coherence results; the differential coherence integration module accumulates differential coherence energy of de-spread satellite signals; the peak detection module realizes signal capturing output; and the sequential control module controls timing sequence of the various modules of the system. Weak signal capturing speed and sensitivity of a satellite navigation receiver are improved, and parameters can be configured flexibly.

A radio-frequency (RF) receiver includes a receiver analog circuitry and a receiver digital circuitry. The receiver analog circuitry resides within a first integrated circuit and the receiver digital circuitry resides within a second integrated circuit. The second integrated circuit couples to the first integrated circuit via a one-bit digital interface. The receiver analog circuitry receives an RF signal and processes the received RF signal to generate a digital signal. The receiver analog circuitry provides the digital signal to the receiver digital circuitry. The receiver digital circuitry includes a digital down-converter circuitry that mixes the digital signal with an intermediate frequency (IF) local oscillator (LO) signal to generate a digital down-converted signal. The receiver digital circuitry also includes a digital filter circuitry that filters the digital down-converted signal to generate a filtered digital signal.

The invention relates to a standing wave detecting system and a standing wave detecting system method for a radio frequency remote system, which fully use a hardware module of a DPD processing subsystem in the radio frequency remote system and count an average power by adopting a base band power statistic module, so that the precision of the standing wave detection is improved and the cost of the standing wave detection is reduced. The standing wave detecting system comprises a switch, a forward power feedback link, a backward power reading link, and a radio frequency feedback link, an analogue digital converter, a digital down-conversion module, the base band power statistic module and a monitoring subsystem, which are connected sequentially. The switch is connected with the forward power feedback link, the backward power reading link, and the radio frequency feedback link respectively; the base band power statistic module is used for performing statistic on the forward power feedback link and the backward power reading link and then computing the average power under the control of the monitoring subsystem; and the monitoring subsystem is used for computing a standing-wave ratio according to the average power.

A cost-effective continuous phase logic-based modulator and demodulator are provided to allow communications using binary frequency shift keying (BFSK) as well as M-ary FSK techniques. The modulator of the 1-bit precision modem architecture is based on a 1-bit precision numerically controlled oscillator (NCO), which provides complete programmability with respect to a frequency of the 1-bit precision logic-based modulator and/or demodulator. The 1-bit precision NCO includes an adder and a phase accumulator register which is clocked by a master clock signal. A two-input multiplexer has a single bit symbol value to generate BFSK, or larger input multiplexers can be implemented to provide M-ary FSK. The output of the 1-bit precision NCO is upconverted to an intermediate frequency using a simple logic function, i.e., XNOR logic. Alternatively, the intermediate frequency may be arrived at without the need for upconversion by directly utilizing a harmonic alias at a desired IF frequency. The undesirable portion of the upconverted signal may be suppressed using I/Q image rejection, and/or an appropriate bandpass filter may be used. A band limited, hard limited signal at the high IF is presented to the 1-bit precision demodulator as a receive IF signal, which is treated as a 1-bit quantization of the signal. The receive IF signal is digitally down-converted to a low IF signal to produce an alias signal at the low IF frequency.

The invention discloses a direct sequence/frequency hopping signal system array antenna adaptive beamforming system. The adaptive beamforming system has strong anti-jamming capability. According to the technical schemes of the invention, DS-FH (direct sequence/frequency hopping) mixed spread spectrum signals outputted by a frequency hopping transmitter pass through each array element channel of anarray antenna; mixers mix received radio frequency signals; A/D converters convert mixed signals into digital signals; the digital signals are subjected to frequency hopping carrier capturing, and then, a frequency synthesizer outputs reference local oscillation signals in a mixed manner; the de-hopping of the radio frequency DS-FH signals is realized; de-hopped direct sequence spread spectrum signals are subjected to primary down-conversion through digital down converters; a plurality of paths of intermediate-frequency direct sequence spread spectrum signals which are obtained after digitaldown-conversion is performed are sent to an adaptive beamforming module; the adaptive beamforming module generates a path of spread spectrum signals through weighting; the adaptive beamforming moduleperforms de-spreading processing on the spread spectrum signals; a weight vector is solved through adopting a recursive least squares (RLS) algorithm; minimum output power is obtained according to theobtained weight vector; and nulls at interference sites are formed.

The invention relates to a frequency change system group delay test method which comprises the following steps of: generating an FM (Frequency Modulation) carrier signal of which the carrier frequency is the center frequency of a working frequency band of a frequency change system by a signal source; then dividing the signal into two paths, wherein one path of signal is input to the frequency change system by an attenuator and used as the input of a first A/D (Analog-to-Digital) converter by the attenuator after being output by the frequency change system, the other path of signal is used as the input of a second A/D converter, and the two A/D converters synchronously sample data by using the same reference clock; then respectively carrying out Hilbert transformation, digital down conversion and non-coherent demodulation on two paths of A/D sampled data; and carrying out digital phase comparison on the two paths of demodulated base band signals to obtain a group delay value of the frequency change system. A group delay test result of all frequency points of the frequency change system in the frequency band can be obtained by changing the carrier frequency of the FM carrier signal in the working bandwidth of the frequency change system and repeating the processing; and the measuring precision depends on system heat noise, the correcting precision of a test cable and A/D sampling resolution.

The invention relates to a method and device for receiving signal in wireless base station, which converts the upstream signal to high intermediate frequency signal through the front of analogue radio wide band by the antenna of the base station. After being sampled digitally by high speed A/D, multi-path digital channel signals are send to the PLC digital down frequency conversion circuit and divided into multi-path base band orthogonal signals, The after software base band processing based on the base band digital signal processing technology, the bit flow is formed and send to BSC (base station controller) for further processing. In the device, a radio frequency front processing module, a high speed wide band A/D converter, a PLC digital down frequency conversion module and a base band digital signal processing module are connected in order.

The invention discloses a measuring method for pseudo code delay of a spread spectrum signal with high dynamic range and low signal-to-noise ratio. A spread spectrum receiver is used for performing ADC (Analog to Digital Converter) sampling on an intermediate frequency analog signal; the intermediate frequency analog signal is subjected to digital downconversion to obtain a baseband complex signal r(k)=I(k)+jQ(k); the baseband complex signal is simultaneously outputted to a pseudo code capturing unit, a carrier and pseudo code closed-loop tracking unit and a pseudo code time delay open-loop estimation unit; the carrier and pseudo code closed-loop tracking unit is used for tracking carrier frequency and pseudo code phase according to the captured doppler frequency and pseudo code phase information; a pseudo code time delay measuring pulse is used for outputting the doppler frequency and the pseudo code phase information to the pseudo code time delay open-loop estimation unit and outputting the pseudo code phase information to a pseudo code time delay calculation unit; the pseudo code time delay calculation unit is used for correcting closed-loop tracking measurement data of the pseudo time delay by using the open-loop estimation result and realizing quick high-precision measurement of the pseudo time delay. By the adoption of the method, the quick high-precision measurement of the pseudo time delay in the complex environment can be realized.

The invention discloses an intermediate frequency linear frequency modulation-pulse Doppler (LFM-PD) radar signal real-time processing system based on field programmable gate array (FPGA) and digital signal processor (DSP) and a method for realizing the system. The system consists of an intermediate frequency sampling module, a digital down-conversion module, a pulse compression module, a coherent accumulation module, a motion compensation module and a constant false alarm detection module. A processed radar signal enters the intermediate frequency sampling module at first; the dispersed signal is sent into the digital down-conversion module for digital down-conversion processing; then the signal enters the pulse compression module for pulse compression processing; after the coherent accumulation module accumulates out a result, the signal enters the motion compensation module to calculate the motion compensation quantity; and finally, the coherent accumulation result enters the constant false alarm detection module to detect out an object. The intermediate frequency LFM-PD radar signal real-time processing system based on FPGA and DSP can meet real-time processing requirements, is short in development cycle and strong in flexibility, and is suitable to be applied to large-scale radar detection systems.

The invention relates to a universal pseudocode synchronization system of comprehensive satellite baseband equipment, and the system comprises six parts, i.e. a digital lower variable frequency module (10), a tracking related module (20), a capture pre-processing module (30), a capture related module (40), a capture management module (50) and a tracking control module (60), and completes the pseudocode capture, carrier tracking, pseudocode tracking and bit synchronization functions of remote control or range finding data in a test to a satellite according to a preset process; and the six parts are realized in a field-programmable gate array (FPGA). According to the universal pseudocode synchronization system of the comprehensive satellite baseband equipment, the parameters of the capture module are configured flexibly according to the test needs of the actual satellite, so that the quick capture and tracking of various remote control signal or range finding signal pseudocodes are realized, and the system has better practical value and wide application prospect in the technical field of comprehensive satellite baseband testing.

The invention discloses a multi-carrier digital receiver based on digital medium frequency, which comprises a radio frequency receiving subsystem, an A/D converter, a digital baseband signal processing subsystem, an automatic frequency control subsystem, and a multi-carrier digital down-conversion subsystem; wherein, the output terminal of the radio frequency receiving subsystem is connected with the input terminal of the digital baseband signal processing subsystem sequentially by the A/D converter and the multi-carrier digital down-conversion subsystem, the input terminal of the automatic frequency control subsystem is connected with the output terminal of the digital baseband signal processing subsystem, and the output terminal of the automatic frequency control subsystem is connected with the input terminal of the radio frequency receiving subsystem. The invention establishes the multi-carrier digital down-conversion subsystem by adopting the digital medium frequency technology and utilizing the multi-carrier signal processing method, thus avoiding the limitation of the traditional digital down-conversion subsystem and realizing the multi-carrier digital receiver system.

The invention discloses a software channelized coherent frequency-agile radar receiver and a receiving method. The software channelized coherent frequency-agile radar receiver includes a local frequency oscillator module which generates a first group of single-frequency signals of a fixed frequency and a second group of single-frequency signals of a fixed frequency, a waveform generation and up-converter module which selects base band waveform required by a radar and generates corresponding intermediate-frequency waveform according to the base band waveform, and performs up conversion on the intermediate-frequency waveform to radar radio frequency, and amplifies the radar radio frequency and transmits radar radio frequency signals, and a signal acquisition and down-converter module which receives the radar radio frequency signals and performs down-conversion on the radar radio frequency signals to intermediate frequency, and amplifies the radar radio frequency signals and then performs digital sampling, and performs digital down-conversion on the radar radio frequency signals, and demodulates the signals in to the base band the digital domain. The invention also discloses a software channelized coherent frequency-agile radar receiving method. The software channelized coherent frequency-agile radar receiver and receiving method of the invention can greatly increase radar frequency-agile frequency points under the premise that no equipment is increased; and the software channelized coherent frequency-agile radar receiver and receiving method of the invention have the advantages of excellent coherent performance, multi-frequency point simultaneous receiving and wide observation distance range.