722 results about "Digital intermediate frequency" patented technology

A frequency modulated continuous wave (FMCW) radar system is provided that includes a receiver configured to generate a digital intermediate frequency (IF) signal, and an interference monitoring component coupled to the receiver to receive the digital IF signal, in which the interference monitoring component is configured to monitor at least one sub-band in the digital IF signal for interference, in which the at least one sub-band does not include a radar signal.

A digital IF receiver (DRX) module directly compatible with advanced radar systems such as synthetic aperture radar (SAR) systems. The DRX can combine a 1 G-Sample/sec 8-bit ADC with high-speed digital signal processor, such as high gate-count FPGA technology or ASICs to realize a wideband IF receiver. DSP operations implemented in the DRX can include quadrature demodulation and multi-rate, variable-bandwidth IF filtering. Pulse-to-pulse (Doppler domain) filtering can also be implemented in the form of a presummer (accumulator) and an azimuth prefilter. An out of band noise source can be employed to provide a dither signal to the ADC, and later be removed by digital signal processing. Both the range and Doppler domain filtering operations can be implemented using a unique pane architecture which allows on-the-fly selection of the filter decimation factor, and hence, the filter bandwidth. The DRX module can include a standard VME-64 interface for control, status, and programming. An interface can provide phase history data to the real-time image formation processors. A third front-panel data port (FPDP) interface can send wide bandwidth, raw phase histories to a real-time phase history recorder for ground processing.

The invention discloses a micro/nano satellite measure and control communication integral transmitting and receiving system and a realization method thereof. The method comprises the following steps: 1) uplink signal processing: 11) receiving and processing radio-frequency signals to obtain analog intermediate-frequency signals; and 12) carrying out analog to digital conversion and digital underlocking on the analog intermediate-frequency signals and dividing into two paths of uplink digital intermediate-frequency signals, namely, one path of the signals is sent to a satellite-mounted computer by QPSK (quadrate phase shift keying) demodulation and uplink protocol processing so as to finish uplink data transmission, and the other path of the signals is subjected to the PM (phase modulation) demodulation to obtain side sound signals and PSK (phase shift keying) remote signals, and the PSK remote signals are subjected to BPSK (binary phase shift keying) demodulation to convert into a remote control command which is sent to the satellite-mounted computer so as to finish the remote control; and 2), downlink signal processing: 21), acquiring two paths of data from the satellite-mounted computer and a storage unit, namely, one path of data which is subjected to downlink protocol processing, BPSK modulation, combination with the side sound signals and downlink measure and control carrier PM modulation is combined with the other path of data which is subjected to the downlink protocol processing and the QPSK modulation to enter a satellite-ground radio-frequency emission channel; and 22) converting into radio-frequency signals to finish the remote measure and the downlink data transmission.

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.

The invention discloses a multi-dimensional fast acquisition method and system for satellite signals. The acquisition system comprises a digital intermediate frequency mixer, a local code generator, a partial matching filter (PMF), a fast Fourier transform (FFT) module, an acquisition detection module, an acquisition verification module and an acquisition judgment module; the technical problems of limited detection frequency offset range, high hardware implementation complexity, long processing delay and the like a satellite signal acquisition algorithm under a high dynamic environment can be solved via the algorithms of frequency adaptive adjustment, partial matching filter, fast Fourier transform and the like; the method and the system have the remarkable advantages of simple structure, low technical implementation complexity, short processing delay, large detection frequency offset range and the like, wherein the detectable Doppler frequency shift range is +/- 50 KHz, the Doppler frequency change rate is +/- 50 Hz, stable reception of radio communication under the extremely high dynamic environment having the flight speed of 20Ma and the acceleration of 180g can thus be realized, and the acquisition tracking time is less than 100ms.

The invention relates to a navigational satellite signal receiving module, comprising a radio frequency input unit, a base band processing unit, a sensor unit and a information output unit; wherein the radio frequency input unit is used for receiving a navigational satellite signal and outputting a digital intermediate frequency signal, the base band processing unit is used for acquiring satellite navigation information and positioning and resolving the current position of the receiving module, the sensor unit is used for acquiring the speed, acceleration or directional information of the current receiving module and outputting the speed, acceleration or directional information to the base band processing unit, and the information output unit is used for outputting the current position of the receiving module in NMEA format. By adopting the technical scheme of the invention, processing on sensor information of a user MCU can be eliminated, only a UART interface reported by a navigation message is processed, and navigation positioning information of NMEA-0183 and sensor information can be simultaneously acquired and reported. Thus, user demand can be met flexibly, not only accuracy of positioning is improved, but also port occupancy rate and processing overhead of the user MCU are reduced. The invention can be applicable to navigational satellite positioning systems such as GPS, Beidou navigation satellite system, GLONASS and Galileo navigation satellite system.

Disclosed is a receiver digital filter for a digital IF signal processor suitable for the specification of each communication standard in a communication system that supports at least one communication standard. The filter for each standard is constructed as one block, and includes a block for externally implementing the constructed block. The coefficient of the digital filter constructed in one block is implemented with an external input or an internal filter coefficient calculator by a basic filter building block. In this manner, the common resources required in the digital filter used in each communication standard are shared, and only the additionally required resources are selectively implemented. Since the shared resources are calculated by dynamic programming, a considerably smaller number of additional resources are required.

The invention relates to a system for measuring a radio-frequency signal high-speed sweeping frequency spectrum based on a digital local oscillator. The system comprises a radio frequency conversion unit, an intermediate frequency signal conditioning unit and a digital intermediate frequency signal processing and controlling unit which are sequentially connected in series. The digital intermediate frequency signal processing and controlling unit is provided with a digital scan synchronous control circuit module and a programmable digital oscillator, wherein the digital scan synchronous control circuit module is connected with an in-phase quadrature (IQ) signal shunt processing circuit module through the programmable digital oscillator, the digital scan synchronous control circuit module is connected with a first local oscillator device, a detector, or a fast fourier transform (FFT) convertor. The invention further relates to a method which is based on the system and achieves synchronous control for the scanning in high-speed sweeping frequency spectrum measurement. Due to the fact that the system and method for measuring radio-frequency signal high-speed sweeping frequency spectrum based on the digital local oscillator are adopted, scanning time is greatly shortened, local frequency accuracy in a scanning process is improved, circuit hardware is simplified, cost is reduced, working performance is stable and reliable, and range of application is wide.

The invention discloses an onboard automatic speed measuring and height measuring radar system and a speed measuring and height measuring method. The system comprises an antenna, a transmitter, a superhet receiver, a broadband digital intermediate-frequency receiver, a center computer and a power module. The transmitter generates four sawtooth wave linear frequency modulation radio-frequency signals and achieves space symmetric configuration through the antenna; the superhet receiver and the broadband digital intermediate-frequency receiver complete echo signal digital demodulation together and calculate the frequency, amplitude, phase and signal-to-noise ratio information of echo signals; the center computer separates the speed information and the height information of the same echo beam by applying Doppler principle directivity based on the space symmetry and the timing sequence relevance of four beams, and the information is used for calculating the flight speed value and the flight height value of an aircraft. According to the onboard automatic speed measuring and height measuring radar system and the speed measuring and height measuring method, the same radar can be used for automatically measuring the speed and the height, the structure of an aircraft avionics system is simplified, the measuring precision is high, and the onboard automatic speed measuring and height measuring radar system and the speed measuring and height measuring method can be used for measuring carrier aircraft flight parameters.

The invention discloses a zero intermediate frequency transmitter and a correction method and a device of a sideband and the local leakage of the zero intermediate frequency transmitter. The correction method includes the following steps: A. setting the pre-correction parameters of the sideband and the local leakage and receiving the input of base-band digital signals; B. establishing a pre-correction model of the sideband and the local leakage with the pre-correction parameters of the sideband and the local leakage and carrying out pre-correction treatment of the input base-band digital signals with the model; C. treating the base-band digital signals which are carried out the pre-correction treatment into radiofrequency signals; D. receiving at least a part of radiofrequency signals and treating the part of the radiofrequency signals into digital intermediate frequency signals; E. revising the pre-correction parameters of the sideband and the local leakage by making use of the input base-band digital signals or base-band digital signals which are carried out pre-correction treatment and the digital intermediate frequency signals and returning to step B. The device comprises a numerical pre-correction unit and a self-adaptive treatment unit. The method and the device can correct the sideband and local leakage of the zero intermediate frequency transmitter in a real time manner.

The invention relates to an interference suppression method based on BeiDou-I satellite signal reception. The method comprises the following steps of: (1) receiving N*(1-theta) BeiDou digital intermediate-frequency data and buffering the front N*theta sampling point data; (2) selecting window functions with the window length of N, combining the received N*(1-theta) BeiDou digital intermediate-frequency data and the received front N*theta sampling point data into N data to be analyzed in time sequence and sequentially multiplying the N data to be analyzed by N window function quotients; (3) carrying out FFT (Fast Fourier Transform) on the N data subjected to windowing treatment and storing the real part data and the imaginary part data of the N frequency points subjected to FFT; (4) calculating the module values of the frequency points subjected to the FFT; (5) calculating a threshold value according to the average value of the module values and the module values the current batch of data under a non-interference environment; (6) calculating attenuation quotients corresponding to interference frequency points; (7) attenuating according to the interference frequency point positions and the attenuation quotients which are acquired through calculation; and (8) carrying out IFFT (Inverse Fast Fourier Transform) on a frequency domain signal subjected to interference suppression.

A digital all-optical distributed system allowing multiple-service access is characterized by comprising an access unit, an expansion unit and a remote unit, wherein the access unit and the expansion unit are connected through optical fiber, and the expansion unit and the remote unit are connected through optical fiber; the access unit or the expansion unit is connected with the network, and the remote unit is connected with the network; and a switching unit can be further arranged and is connected with the access unit which is used for 1+1 backup through a feeder line cable and optical fiber. The access unit in the system couples multiple service radio-frequency signals from a signal source, converts the signals into digital baseband signals and transmits the digital baseband signals to the expansion unit, the expansion unit realizes shunting of digital baseband downlink signals and combining of digital baseband uplink signals and transmits the digital baseband signals to the remote unit through optical fiber. The system can provide services such as wireless access, fixed network broadband, WLAN (wireless local area network) signal transmission and the like, can develop multiple functions on the basis of digital intermediate frequency and can support star, daisy chain and mixed networking.

A digital front end transceiver system (300) for a software radio system comprising: a transmitter module (310) adapted to digitally interpolate, up-convert and combine baseband digital in-phase (I) and quadrature (Q) channels to form a digital intermediate frequency (IF) IQ signal for conversion to an analogue IF IQ signal for transmission; and a receiver module (320) adapted to separate, down-convert and decimate a received digital IF IQ signal into baseband digital I and Q channels. The transmitter and receiver modules use a common fixed sampling and IF conversion rate f_s, where f_s is a quadruple of the bandwidth of the baseband signal, such that the system can be applied in a software radio system for a wireless communication application having any baseband bandwidth by selecting the fixed sampling rate based on the baseband bandwidth.

The invention provides a Beidou satellite user equipment receiving anti-jamming method which solves the anti-jamming problem of a Beidou satellite navigation system in practical use and relates to the technical field of satellite navigation and intelligent antennas. The anti-jamming algorithms of space-time adaptive-filtering and Kalman filtering are combined, digital intermediate-frequency signal data is corrected by calculating the amplitude-phase error correcting weight number of a channel, a covariance matrix is estimated, an adaptive weight number is calculated, and the weight coefficient of an adaptive filter is updated. Accurate zero traps are performed to jamming on a directional diagram of a receiving antenna of Beidou satellite user equipment without knowing about the directions of jamming and signals, various kinds of jamming are inhibited, and the integrity of the signals is maintained. The invention has low calculated amount, good robustness, high anti-jamming capability and no damage to the signals.

The invention provides a radio remote unit (RRU). The RRU comprises at least one radio remote and an interface (IR) processing unit, wherein each radio remote is connected with the IR processing unit through a CAT5E wire and connected with an antenna to process received uplink analog radio frequency signals into uplink data containing uplink digital intermediate frequency signals and send the data to the IR processing unit from which downlink data containing downlink digital intermediate frequency signals is received and processed into downlink analog radio frequency signals which are sent tothe antenna; and the IR processing unit processes uplink data, which contain uplink digital intermediate frequency signals and are from each radio remote, into uplink digital baseband signals which are sent to a BBU and processes downlink digital baseband signals from the BBU into downlink data which contain downlink digital intermediate frequency signals and send the downlink data through a ratio remote. The RRU can perform the coverage by using a plurality of ratio remotes, thereby expanding the transmission capacity.

The invention discloses a beam position and phase measurement system and method based on the full digitalization technology. The system comprises a simulation front end part and a digital processing part. In the simulation front end part, the undersampling technology is utilized for carrying out undersampling on input signals from a beam position detector, the sampling rate is accurately adjusted through a phase-locked loop digitally controlled and is made to be four times larger than the digital intermediate frequency signal frequency obtained after the input signals of the beam position detector are undersampled, and a digital orthogonal sequence of the input signals of the beam position detector is directly obtained. In the digital processing part, digital processing is carried out on the digital orthogonal sequence obtained through undersampling of the simulation front end part, the beam position and the phase position of an accelerator are measured, and the phase position is modified on line in real time. Digital processing modules are integrated on a single chip FPGA, and the system structure is greatly simplified. By means of the appropriate sampling rate, the orthogonal sequence of the input signals is directly obtained after ADC sampling, and the signal phase position and amplitude digital processing algorithm is greatly simplified.

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 an antenna feeder tester and an extending device error correction method by using the antenna feeder tester. The antenna feeder tester comprises a signal synthesis module, a power divider, a directional coupler, a test port, an amplitude and phase receiver module, an FPGA digital intermediate frequency processor and a CPU controller, wherein the signal synthesis module comprises an excitation signal source and a local vibration signal source; and the amplitude and phase receiver module comprises an R channel and an A channel, and one A/D conversion module is arranged behind each of the R channel and the A channel. During measurement, after correction is finished at the test port of the instrument, the antenna feeder tester of the invention is then used to measure transmission parameters of an extending device in the case when the extending device is connected, the transmission parameters of the extending device are used for correcting test data when the extending device is connected with a tested piece according to a theoretical loss formula of a cable, correction does not need to be carried out again, and the measurement precision and the test efficiency are thus improved.

The invention belongs to the technical field of human-computer interaction, and particularly relates to a micro-motion gesture recognition method based on millimeter-wave radar and a convolutional neural network. The method mainly comprises the following steps: designing radar parameters and micro-motion gestures according to an application scene; using a millimeter-wave radar for periodically transmitting linear frequency modulation signals with determined radar parameters and receiving echo signals reflected by hands of a human body, and carrying out ADC sampling after difference frequency is carried out on the echo signals and transmitted signals to obtain digital intermediate frequency signals; processing the digital intermediate frequency signal, and calculating characteristic parameters of the micro-motion gesture; selecting a certain feature, and establishing a data set of multiple gestures; designing a convolutional neural network for the millimeter-wave radar feature image, and inputting a gesture data set for training to obtain a classification model; and calling the classification model to realize classification and recognition of various gestures. The method is high inpracticability, can be applied to the fields of smart home, air input, sign language translation, mechanical control, VR, AR and the like, and is wide in application prospect.

Disclosed is an apparatus and a method for up-converting frequencies of digital Intermediate Frequency (IF) signals input through at least two paths, and then outputting IF signals to which at least two frequencies are allocated in a communication system. The apparatus includes Serializer/Deserializers (SerDeses), down-converters, up-converters, a signal adder, a Digital-to-Analog Converter (DAC), and a Band-Pass Filter (BPF), etc. In relation to digital IF signals respectively input through at least two paths, first, the frequency down-conversion is performed, and then, the up-conversion to relatively low frequencies is performed.