Device for suppressing narrow-band interference in satellite navigation receiver. RU patent 2513028.

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to radioelectronics and can be used as a cheap means of suppressing narrow-band interference at the input of a navigation receiver of signals from GLONASS, GPS, Galileo and Compass satellites. The interference suppressing device includes a spectrum analyser, having a first discrete Fourier transform (DFT) unit, a unit for selecting narrow-band interference, a unit for rejecting narrow-band interference having a second DFT unit, the output of which is connected to an inverse DFT unit, and an adder; a memory unit is connected between the input of the analyser and the non-inverting input of the adder, and the output of the rejection unit is connected to the inverting input of the adder.

EFFECT: designing a cheap means of suppressing narrow-band interference in conditions where there is a large amount of unstable narrow-band interference, using few hardware resources and computational costs without peak loads, as well as high reliability of timely determination of narrow-band interference owing to constant signal scanning for presence of said interference.

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The technical field to which the invention relates

The invention relates to the field of radio electronics and may be used for suppression of the receivers of satellite navigation signals, particularly GPS, GLONASS, Galileo and Compass. The invention can also be used for other satellite navigation systems, operating in accordance with the same principles.

The level of technology

Currently, the scope of application of satellite navigation systems (SNS)such as GPS and GLONASS and Galileo and Compass, constantly expanding due to the improvement of the navigation receivers, which is achieved by improving processing algorithms navigation signals and use of navigation equipment in the complexes. In particular, to the navigation receivers are required to receive weak signals in conditions of shading (for example, forest, urban and natural canyons) and in premises.

As the receivers are becoming more sensitive, even a weak level of narrow-band interference from consumer electronics has a negative impact on the detection and tracking of navigation signals.

This is because a transmitter installed on the navigation satellite has little power. For example, the power of navigation GPS signal is approximately 50 W. When the satellite is at a distance of 20,000 km from the Earth's surface. This leads to the fact that the firm capacity accepted navigation signal under the open sky is just 10 -16 W or 130 dBm. When you move the receiver to the premises of the power of the received signal is another 20-40 dB less. So even a hindrance rather low power, being on the frequency of signal, can completely disrupt navigation receiver.

Increased sensitivity GPS receiver to narrowband interference due to the spectral properties of the civil code GPS, code standard precision GLONASS and similar codes used in navigation system Galileo and Compass. As periodic, these codes lead to linachtal spectrum of the transmitted by satellites navigation signal. Similar properties have and frequency characteristics of the agreed filters correlators. The coincidence of the frequency narrow-band interference with a local maximum frequency characteristics matched filter correlator can cause the receiver significantly more harm than conventional thermal noise of the same capacity. However algorithms increase the sensitivity of the receiver is effective if the only white noise, are helpless to counteract narrowband interference.

One of the sources of interference are clock generators mass digital devices such as personal computers, laptops, smartphones, and tablet PCs. Another source of interference are switching power supplies and monitors (screens). The processes occurring in these devices are of a quasi-periodic nature that causes the generated noise are concentrated along the spectrum, i.e. narrowband. Sources of interference are also transmitters mobile base station that can interfere significantly exceeding the capacity level of thermal noise in the low-noise amplifier receiver.

The most dangerous is interference from electronic equipment, the spectrum of which falls in the same frequency ranges, which occupy satellite navigation signals. The higher the sensitivity GPS receiver, the stronger the influence of narrow-band interference on his work with weak signals, as it increases the quantity of dangerous narrowband noise present in almost any room with electronic equipment. If the signal level of the satellite - 160 dBm affecting its support narrowband interference in the average room with electronic equipment of the units, at the level of the satellite signal - 170 dBm such interference dozens.

Thus, the task of highly effective and at the same time, lightweight suppression narrowband interference to commercial navigation receivers is relevant.

Signals of satellite navigation systems such as GPS, GLONASS, Galileo and Compass, occupy a wide band of frequencies through the use of spread spectrum technology. Unlike useful navigation signals interfering noise signals are usually narrowband (focused on spectrum), and, as already noted, it is a narrow-band interference are the biggest threat to receivers. The difference in the shape of the spectrum creates conditions for the selection of the useful signal in the presence of narrow-band interference.

For the efficient production of navigation signals the receiver impose additional modules designed for detection and suppression of narrowband interference. Interference rejection before they enter the correlators is the most reliable and the most expensive way of dealing with interference.

Cheaper way to identify and combat narrowband interference contained in patent [1]. The method is to monitor several indicators of the presence of interference. One of them is the ratio of the change in temperature with a velocity change of care hours receiver. This indication method is based on the fact that the speed of care varies in accordance with a small temperature changes, and if there was a sharp change in velocity of care, it is an indicator of the presence of interference. Another indicator is implemented by monitoring the ratio of signal to noise ratio. This indication method is based on the fact that if this ratio drops sharply, more than preset value (for example, 3 dB), then there is a fault signal. Another indicator is implemented by monitoring the output of the correlator. Is the correlation of the received GPS signal with the SRP in the first correlator. The yield of the first correlation function indicates that the SRP is present in the accepted GPS signal. Correlation of the received GPS signal with a shifted to delay version of the SRP in the second correlator is used to indicate interference. The delay should be sufficient for the release of the second correlator showed that shifted the delay SRP is not in the accepted signal. An indicator of the presence of interference is falling output value of the first correlator, which coincides with the increase of the output value of the second correlator. The following method indicate interference is based on the correlation of the input signal GPS with pseudo-code not accepted by the GPS receiver. This is the code that does not match 32 codes used, i.e. code that is reserved for other uses. In addition, using data of the almanac contains information about the position of all satellites in the system, you can select the satellite, which is not included in the reception range of the receiver, and use the SRP. In the absence of interference and with a fairly strong signal correlation with unused SRP will show a low value. When the disturbance is present, the correlation will show a high value. The more correlators, which show an increase in the value, the greater the likelihood of interference. Another method of indicating the presence of interference is to observe the signal strength: the ratio of the power of the received signal with the capacity values of the signal, which is well known. The sharp increase in signal power will indicate unwanted signal and the noise source. Classification methods interference can be combined, as it is safer to have two (or more) of the indicator for the best confirmation of the presence of interference.

If an obstacle is detected, it can be taken countermeasures. The simplest of them is blocking the work of the receiver for the duration of narrowband interference. So avoid erroneous jumps in the position or speed. The device can display a message about the availability of signal interference and can show the correct position. It may also mean that the correct item is not available. The navigation device can also use an alternate method of navigation calculations during the active phase of narrow-band interference, in which position is determined as the last known good position, last known direction and the last known speed. The disadvantage described method is that it is not valid suppression of narrow-band interference, and the probability of detection depends on the number of indicators. Detection and counteraction without their interference suppression in the input signal is the most economical, but the least effective method of struggle against interference.

Method of detection and suppression of narrowband interference before it reaches the entrance of the correlators are given in patent [2]. The patent describes a system of suppression of narrowband interference for use in broadband receiver. Suppression system includes a tool to convert the received signal from the time domain into the frequency, means for suppression of disturbances component in the frequency domain above the threshold tool to determine the threshold and recovery solution for signal through the conversion of the frequency domain into the time.

The principle is based on the fact that narrow-band noise in the input signal is converted to a strong "pulse", i.e. discrete components in the frequency domain. Discrete components, with the amplitude that exceeds the threshold, suppressed in the frequency domain. The threshold is determined by averaging the amplitude of the received signal in the time domain. The inverse transform of the signal from the frequency domain in coherent continuous output signal in the time domain signals, almost equal to the accepted signal with significantly reduced components narrowband interference.

This system of suppression of narrow-band interference is one of the types of systems Ricchi interference in the frequency domain, which provides continuous suppression of narrow-band component interference within the right of the input signal. In addition, with the exception of delay, the system provides "real time" to suppress interference without prior knowledge of frequency, phase, or amplitude components interference. However, the system of suppression of narrow-band interference, described in the patent [2], has the disadvantage is the increased demands for computing resources.

Method for detection and elimination of narrowband interference in the frequency domain is presented in the patent [3]. The method is based on the nonlinear amplitude-frequency filtering in real time using the technology of fast Fourier transform (FFT). The received signal is digitized and converted into the frequency domain by using the FFT. The FFT output is a set of complex (real and imaginary) numbers, which represents the frequency components of the digitized signal. The noise reduction algorithm consists of three steps. At the first stage of the Converter in polar form of the signal spreads the signal to its amplitude and phase components. At the next stage, the signal amplitude is normalized, to eliminate narrow-band interference with a large amplitude. At the last stage, the signal is converted from the polar coordinate system in a rectangle with an amplitude that is installed in some arbitrary value that is necessary to return to normalized range. As there is no need to calculate the threshold, no additional consumption of computing resources. Each data point is processed without delay time. Cleared from interference signal is converted by using the inverse fast Fourier transforms the time domain.

The disadvantage of this system of suppression of narrowband interference is the requirement of large hardware resources, including memory, which complicates its implementation, as well as a significant distortion of the useful signal.

Another direction of creating a robust navigation receivers is adaptive filtering of the signal before initial processing. In such devices is used tunable notch filter that performs functions whitening interference. This algorithm is implemented in the receiver with spread spectrum method direct sequence (Direct Sequence Spread Spectrum, or DSSS), described in the patent [4]. The rejection of one or more of narrow-band interference is based on the spectral analysis of the signal amplitude in the discovery channel. To denote the spectral analysis is used in English the term "frequency bin" or simply "bin", meaning the permissions item in frequency. Here and below, to indicate component of the spectrum uses the term "bin" or "frequency bin". To determine which frequency components of spectral analysis contain interfering signals, the amplitude and frequency bins are compared with the threshold. Frequency of Bina with the obstacle is determined by the amplitude exceeding the threshold. Reject filters cut out the appropriate narrowband interference.

Input can consist of a useful signal extended range and one or more powerful concentrated on spectrum interference. Receiver with control signal automatic gain control (AGC) maintains a constant level of the input signal. The input signal is first converted to an intermediate frequency signal, then digitized and converted into a quadrature (I/Q) signal.

The device consists of two channels, channel interference detection and signal channel. The signal comes in both channels simultaneously. The discovery channel interference is the spectral analysis of the I/Q signal. The amplitude detector determines the amplitude of the I/Q signal in the frequency bins. Passing on information about amplitude in the frequency bins produced signal automatic gain control (AGC). Then the amplitude of the frequency of Bina is compared with the threshold is determined by the number of Bina, contains a narrow-band interference.

The signaling channel contains delay, and frequency-selective reject filters. Notch filters are used to cut out one or more of narrow-band signals in accordance with rooms frequency bins containing interference. Notch filters are implemented as two banks valid digital filters. One Bank filters are used to filter the in-phase (I) components of the signal, and the other to filter quadrature (Q) components. Each filter Bank uses the architecture of the multistage Decimator-interpolator. The Bank notch filter is implemented as the Bank of bandpass filters and parallel included with them delay lines. The delay time equals half the duration of the impulse response bandpass filters. Bank output bandpass filters is subtracted their exit delay lines. This operation implements the Bank notch filters.

Weighting filters are stored in memory for various Central frequency and loaded into the filters depending on frequency interference suppressed.

After rejestrowania interference demodulator performs signal demodulation extended spectrum to estimate the desired signal.

The advantage of this algorithm cut escapology interference is to use a simple algorithm analysis of the amplitude spectrum. The disadvantage of this method suppression is that the use of multistage digital filters requires the use of multiple-bit multipliers, and the number of operations is very high, as you have to calculate the convolution of the input signal pulse response of the filter that you want to implement filtering of the signal. Another disadvantage is the increased demand of memory to store the weights. Thus, for realization of this suppressor require big hardware resources, leading to increased power consumption.

Another example of adaptive filtering of the signal before initial processing is adaptive transversal filter (APF), described in the patent [5]. At the filter input signal, digital multi-bit analog-to-digital Converter (ADC) and containing a mixture of useful signals spread spectrum, thermal noise and narrow-band interference.

Digital input is filtered using a digital filter with finite impulse response (FIR), using the previously calculated weights of the filter. Filter produces a digital signal, which has reduced the number of partially suppressed narrowband interference. The degree of suppression of narrowband interference increases with increase of its capacity. Weight of the digital filter are generated recursively by updating the previous scales through the works of digital baseband signal or digital output signal. Preventing excessive drift digital scale is made by periodic discharge of scales in a value of zero and reinitialization.

The disadvantage of using ATP is that for effective interference rejection you want the filter with pulse response large length, which significantly increases the cost of the receiver.

Another example of adaptive filtering of the signal is the filter line coding with prediction (LCP filter), described in the patent [6]. Periodic and quasi-periodic signals acting as a hindrance, effectively filtered out using LCP filter. LKP the filter receives adopted digitized signal and generates a set of coefficients predictions and the set of coefficients of an error. Predicted coefficients allow to submit to periodic and/or quasi-periodic signal interference. The difference between the input signal and the predicted signal is called the residual or forecast error is the output signal, containing useful transmitted data contained in the signal extended range.

Compared to the ATF is cheaper implementation of suppression of narrowband interference. However, the disadvantage of this algorithm is that the effectiveness of interference rejection decreases with increase in the number of narrowband interference, if they become larger than the number of the LPC coefficients of the filter. In addition, the use of multiple-bit multiplications significantly increases the complexity of the receiver.

Another example of adaptive filtering of the signal is the use of filter infinite impulse response (IIR), described in the article [7]. The algorithm uses adaptive notch (ARF), which is able to detect, measure and cut a single continuous interference. Module ARF consists of a simple filter infinite impulse response (IIR) second order lattice structure. When no signal interference received signal bypasses the ARF module, so that the deterioration of the ratio signal-to-noise induced ARF, can be avoided. An algorithm for the detection and assessment of continuous harmonic interference works in the time domain. Because of this it is not necessary to perform the transformation of temporary into the frequency domain, resulting in the reduction of hardware complexity. The suggested scheme can suppress multiple persistent harmonic interference by cascade module ARF. Detection threshold continuous harmonic interference is determined in accordance with the signal-to-noise and low probability of false positives. Estimation of the error of power interference is reduced when the ratio of the power noise to the signal increases. When several persistent harmonic interference proposed module ARF will be adaptive to adjust the cutting spectral component with the frequency of the strongest continuous harmonic noise that appears on the sign.

You must consider the fact that inside the electrical equipment is present, a large number of narrow-band interference and interference unstable, especially when moving the antenna of the receiver. Because of this, you must constantly reassess the presence of narrow-band interference, as described in patent [8]. Adaptive suppression of unwanted signals in dynamic jamming environment is implemented on the basis of the FIR filter. This method can track relatively rapid changes in noise conditions and cut short narrowband signals that are present in the broadband signal.

In patent [8] FIR filter is implemented in the frequency domain by performing the FFT signal multiplying it by the transfer function in the frequency domain and then perform the inverse FFT. The transfer function is calculated dynamically in real time by determining the energy of the signal in the frequency domain and exceptions bins that contain a hindrance. The signal is delayed for the time required to calculate the transfer function. Therefore, the relatively rapid changes in jamming environment can be tracked and rejestrowany.

Another method of suppression is compensation. This method is based on the principle of selection harmonic interference type of a mixture of useful signal to interference and noise and interference compensation by subtracting. In the scheme agent, described in the patent [9]is used, the method of selection interference with the generator, forming pomenovany signal. Its distinctive feature is the presence of an oscillator with phase adjustment (PLL). Since it is assumed that the capacity of interference at the input significantly more power desired signal generator is controlled directly input any pre-filtered input signal. Generator polioptera signal generates a signal, as close as possible instant value to an obstruction. For this purpose it is necessary to monitor the instantaneous values of the three main parameters interference - amplitude, frequency and phase. In this method of accuracy assessment of instantaneous values of the amplitude and phase of very high requirements.

The advantage of such schemes is their ability to compensate for interference very minimal distortion in the signal. However, the amplitude or phase instability interference makes the application of this method impractical. Thus, one of the main shortcomings of the method of compensation is a strong restriction imposed on the class suppressed signal interference.

For solving the problem of suppression of narrowband interference requires the use of algorithms of digital processing, optimized to run on the hardware platform with limited computing resources and memory, which occupies little space in the implementation in VLSI and low consumption.

From the considered technical solutions as a prototype of the chosen way of rejectee narrowband interference, described in the patent [4], as the closest to the proposed device.

Disclosure of the invention

The invention solves the problem of creating device suppression narrowband interference in satellite navigation receiver. The peculiarity of the present invention is to save hardware resources and reducing the computational cost using the direct calculation of the discrete Fourier transform (DFT) and the inverse discrete Fourier transform (DPF) for a partial set of frequencies. It is important to emphasize that the use of the proposed invention DFT and ODPF to incomplete set of frequencies is more effective from the point of view of economy computational costs than the fast Fourier transform (FFT), which is used in some similar devices.

Another peculiarity of the present invention is to compute DFT in real time. When entering the next input of reference are obtained intermediate results DFT and calculated in real time output counts ODPF on the basis of previously established results DFT. This leads to save memory, to even the formation of output samples and eliminates the maximum processing load. Due to the savings of hardware resources, and reduce computational costs and decreases power consumption. In these circumstances described the device can be applied in satellite navigation receivers used in mobile applications, such as smartphones, tablet PCs, and other devices for which the savings of hardware resources and power consumption is the most important requirement.

These tasks are solved by the present invention under the assumption that the dynamics of the object on which you installed the navigation receiver, not too high. Examples of such objects can be cars or civil aircraft. In this case the distribution of narrow-band interference on the spectrum can be considered relatively constant, and the acceleration of the receiver and derived from accelerating as it moves in space is negligible.

The essence of the invention consists in the following.

Input device suppression narrowband interference goes digital quadrature signal adopted radio frequency module of satellite navigation receiver. In the General case, the input signal is a mixture of useful navigation signal, the broadband noise of the receiver and one or several narrow-band interference. The device suppression narrowband interference contains a spectrum analyzer input block allocation noise block Ricchi interference and the block of memory to store the input counts. Input device suppression of narrow-band interference is connected to the spectrum analyzer input, with the first unit of rejectee interference and to the entrance of the block of memory. The output of the spectrum analyzer is connected to the input unit of allocation of interference, and the output unit selection of interference is connected with a second entrance of the block of rejectee interference. The output of the memory block is connected with the third entrance of the block of rejectee interference. Output unit of rejectee interference is an output device suppression narrowband interference. The output signal of the device suppression of narrow-band interference, free from interference goes for blocks of detecting and tracking of satellite navigation receiver.

The block of spectrum analyzer performs the conversion of an input signal from the time domain into the frequency domain. To this end, the block of spectrum analyzer contains the first module of the discrete Fourier transform (DFT), the input and output of which is connected respectively with input and output block of spectrum analyzer. The peculiarity of the present invention is that the block of spectrum analyzer real-time calculates DFT input for the set of frequencies {F}={F 1 , F 2 , ..., F ScanMax }, which is the frequency bins N-point DFT, and the amount of ScanMax less than the length DFT N and the set of frequencies {F} after each compute DFT changed so that N/F ScanMax iterations move all N frequency bins. Thanks to the relative stationarity of the spectrum interference is possible to analyze the spectrum in parts, but not entirely, due to which reduces the computational cost. The DFT results are passed in the block allocation interference.

Block allocation interference determines the presence of narrowband interference by comparing amplitude spectral components at the output DFT threshold and generates a set of frequencies

, on which the threshold is exceeded. Thus, the block allocation interference generates a set of frequencies {F'} narrowband interference, containing not more than SuprMax elements.

This set of frequencies are passed to the block of rejectee interference through its second input. Also in this block on his first input signal input digital I / q signal, and on his third incoming signal from the output of memory block, which detained the input signal. Block Ricchi interference contains the second module of the DFT, the module inverse DFT (DPF) and adder to the inverting and reinvestiruet inputs. The first input of the second module DFT connected to the first input of the block of rejectee interference. The output of the second module DFT connected to the input module DPF. Second input of the second module DFT and module ADPF is connected to the second input of the block of rejectee interference. Exit block ODPF connected to the inverting input of the adder. Non-inverting input of the adder is connected with the third entrance of the block of rejectee interference, and the output of the adder is the output of the block of rejectee interference.

Suppression of narrow-band interference, the frequency of which are included in the set of frequencies {F'}, is executed in the block of rejectee interference. The second module of the DFT calculates DFT input for the set frequency

, which is the frequency bins N-point DFT, and SuprMax less than the length DFT N and the set of frequencies {F'} comes from the block allocation interference to the second input of the second module DFT through the second entrance of the block of rejectee interference. Due to the fact that the number of narrowband noise as measured by SuprMax, small, DFT is for a small number of points than the savings calculations. The module then DPF does N-point ODPF only for SuprMax nonzero input {F'}, which come to the second input of the module DPF. Thanks to the limited number of non-zero points when performing ADPP also saves calculations. The module output ODPF get a signal evaluation narrowband interference in the time domain, filtered from the satellite signal. Signal evaluation narrowband interference detained relative to the input signal to the operations DFT and ODPF unit Ricchi interference. Output ODPF comes to the inverting input of the adder. On the non-inverting input adder receives the signal from the output of the block of memory that represents the detainee input. Thus, the input signal and signal interference assessment are overlapping. In the adder is subtraction signal assessing interference from the detainee of the input signal, in consequence of which is the suppression of narrowband interference.

Because the set of frequencies is limited to a certain number, N-point DFT and ODPF you can do with tables of compliance (look up table or LUT). This avoids computing trigonometric functions, to reduce calculation time and reduce processing load.

One of the embodiments of the invention is different in that block of memory for input counts is implemented in the form of a circular buffer, whose length is equal to the length DFT N. N-point DFT in the first and second module DFT are calculated as the income of the input counts at the entrance of the block of memory to store the input counts, gradually forming results for ScanMax and SuprMax frequency bins. To store these results in each module DFT contains blocks of memory for intermediate results DFT on ScanMax and SuprMax elements, respectively. While the outputs of the first and second block DFT connected to inputs corresponding blocks of memory. N-point ADPF is also calculated as the income of the input counts at the entrance of the block of memory to store the input counts and contains a block of memory to hold the results of DFT for SuprMax frequency bins used by the module ODPF as input parameters. The output of the block of memory to store the results DFT connected to the module input DPF. The output of the block of memory for the intermediate results of the second module DFT and the entrance of the block of memory to store the results DFT are connected by a switch.

Another distinctive feature of this variant of realization is that when a new input of reference in the block of memory to store the input counts from circular buffer to read the input count received in N steps previously current. Upon receipt of the N-th input reference calculation of the N-point DFT in the first and second module DFT is completed and the intermediate results DFT second module is copied to the memory block for results DFT module ADPF, then a block of memory for intermediate DFT results in both modules DFT is set to zero.

The result of these options, the implementation is double the memory savings block input counts due to a small increase memory for results DFT for ScanMax and SuprMax frequency bins. Owing to save memory and decreases power consumption.

Brief description of drawings

Figure 1 shows the structural scheme of satellite navigation receiver using noise suppression device. Satellite receiver contains a radio-frequency block (101), the device narrowband noise suppression (102), the unit searches navigation signals (103), block the capture and maintenance of the navigation signals and receive data (104), the unit of navigation solutions of problem (105).

Figure 2 shows a block diagram of the device suppression in satellite navigation receiver, which contains a spectrum analyzer (201), the first module DFT (202), block allocation interference (203), block of rejectee interference (204), the second module of the DFT (205), the module DPF (206), adder to the inverting and reinvestiruet inputs (207), the memory block (208).

Figure 3 shows a block diagram of unit Ricchi interference, which contains the block N-point DFT input counts (301), a block of memory for intermediate results DFT (302), switch (303), a block of memory for results DFT (304), a unit N-point DPF (305), block adder with inverting and reinvestiruet inputs (306).

Figure 4 illustrates the device noise suppression for implementation options when DFT and ODPF executed whenever the input counts. Legend: circular buffer input counts (401), a block of memory for results DFT (402), block N-point DPF (403), adder to the inverting and reinvestiruet inputs (404), a block of memory for intermediate results DFT (405).

The implementation of the invention

Figure 1 explains the usage of the offered mechanism of suppression in satellite navigation receiver. The input signal from the antenna, containing a mixture of useful navigation signal, the broadband noise input circuits of the receiver and narrowband noise enters the RF unit (101), where it is amplified, converted in quadrature signal zero frequency and subjected analog-to-digital conversion. Output RF unit turns digital quadrature signal, which is input device narrowband noise suppression (102). As this device is used the invention. Output device suppression narrowband interference obtained navigation signal, purified from narrowband interference, which is then fed to the unit search navigation signals (103). The search block detects the signals of those satellites that are visible at the point of placing the receiver's antenna and the signal level which is sufficient for their reception, estimates the parameters of these signals (Doppler shift, time, signal level) and the information received sends the block capture, maintenance and receiving data (104). Block (104) on the basis of information received from the search block (103), provides accurate waveform capture "visible" satellites in the future, accompanied by, and extracts the data from the satellite signal and transmits the data in the block to solve the navigation problem (105), which according to this data and other information available to solve the navigation problem and defines the coordinates and the speed of the object, on which the receiver. Navigation data from the output of the block decisions navigation tasks enter the equipment of the consumer.

Figure 2 explains the work of the offered mechanism of suppression of narrowband interference in satellite navigation receiver. Digital I / q outputs of the radio-frequency block passed to the block of spectrum analyzer (201)that converts the signal from the time domain into the frequency domain. For this first module DFT (202) calculates in real time DFT input for a given set of frequencies {F}={F 1 , F 2 , ..., F ScanMax }, which is the frequency bins N-point DFT, and ScanMax less than the length DFT N and the set of frequencies {F} after each compute DFT changed so that N/F ScanMax iterations move all N frequency bins. If the ratio N/F ScanMax is not an integer, it is rounded up to the next higher whole number.

The result of the calculation DFT is passed to block allocation interference (203). Block allocation interference stores the results DFT for all N frequency bins, detects the presence of narrowband interference by comparing the amplitude of the output DFT threshold and generates a set of frequencies

, on which the threshold is exceeded. This set of frequencies are passed to the block of rejectee interference (204). In the block of rejectee interference also receives input digital I / q signal - to one input directly to another through a block of memory (208).

In the block of rejectee interference is the suppression of narrowband interference, corresponding to the set of frequencies {F'}. For this input countdown digital quadrature signal is fed to the input of the second module DFT (205). Also in the second unit of module DFT enters the control signal, which specifies a set of frequencies corresponding to narrowband interference being DFT:

. The result of running the DFT can be represented by the following formula:

The results from the output of the second module DFT (205) used by the block DPF (206)carrying ODPF for SuprMax nonzero input {F'}. The result of running DPF can be represented by the following formula:

As follows from this expression, the summation is performed on a small number SuprMax indices k, thereby saving calculations.

Signal c(n) is delayed relative to the input rating of narrowband interference in the time domain. Signal c(n) assessment of narrowband interference in the time domain with output DPF (206) comes to the inverting input of the adder (207)non-inverting input of which comes the countdown from the output of the block of memory (208). In the adder is the subtraction of signal interference assessment of the detainee of the input signal, in consequence of which is the suppression of narrowband interference. In the result of the subtraction is generated output reference unit Ricchi interference.

The structural scheme of the unit Ricchi interference for one of the variants of realization are shown in Figure 3. At the entrance of the block of rejectee interference received input counts, representing a discrete sampling of the received signal. In addition, at the entrance of the block of rejectee interference received samples from the output of the block of memory for N input counts (208), where N is the length of the DFT. Memory is implemented as a circular buffer so that the i-th entry are stored in the place of reference received by N times previously.

Input count digital quadrature signal to the input of the unit N-point DFT (301). Also in block N-point DFT enters the control signal, which specifies a set of frequencies corresponding to narrowband interference being DFT:

. DFT is for a small number of frequencies SuprMax, thereby saving calculations.

Upon receipt of each input reference perform a partial DFT calculation, i.e. the calculation works for the given input reference, then these works are accumulated in the block of memory for intermediate results DFT (302). Upon receipt of the N-th input countdown ends DFT calculation and closed switch (303). Data from a block of memory for intermediate results (302) are copied to the memory block for results DFT (304). After copying the data in the block of memory for intermediate results DFT (302) are set to zero. Data from a block of memory for results DFT (304) used by the unit N-point DPF (305)carrying ODPF for SuprMax nonzero input {F'}.

Signal c(n) assessment of narrowband interference in the time domain with output DPF (305) comes to the inverting input of the adder (306)non-inverting input of which comes the countdown x(n-N) from the output of the block of memory (208). In the adder is the subtraction of signal interference assessment of the detainee of the input signal, in consequence of which is the suppression of narrowband interference. In the result of the subtraction is generated output reference unit Ricchi interference x(n-N)c(n), lagging behind the current input reference to N times.

Figa shows that when the input reference the old input count (counting that lags N times from the current input reference) is served on the non-inverting input of the adder (404), and the inverting input of the output signal DPF (403). Output ADPF is generated every time a new input sample, using previously filled the memory block with the results of DFT (402).

From figb shows that current input entry are stored in the memory block input counts implemented in the form of circular buffer (401), the length of which is equal to the length DFT N. The same reference is served in the unit DFT, where based partly DFT is calculated for a certain set of frequencies {F'}. Intermediate result DFT is accumulated in the block of memory for intermediate results DFT (405).

FIGU and 4G show the processing of the N-th input of reference.

FIGU shows the treatment of the latter relative to similarly figa).

Figg shows that the admission of the N-th input of counting the results DFT fully formed, so they are copied from a block of memory for intermediate results DFT (405) in a block of memory for results DFT (402), data from which will be further used to calculate DPF (403). After copying memory for intermediate results DFT (405) is set to zero.

The implementation of the present invention can be made on the basis of known elements of digital technology (memory blocks, adder, LUT), among which the principal place is occupied units that implement DFT and DPF. DFT (DPF) is a well known algorithm, ways of realization of which is known from the literature (see, for example, Shoab Ahmed Khan "Digital Design of Signal Processing Systems", Wiley, 2011 p.292-296). Thus, the implementation of the present invention is not a problem.

Sources of information

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1. The device suppression narrowband interference in satellite navigation receiver, containing a spectrum analyzer, block allocation narrowband noise block Ricchi interference, with the input of the suppression of narrow-band interference is connected to the spectrum analyzer input and to the first input of a block of rejectee interference, the output of the spectrum analyzer is connected to the input unit of allocation of interference output unit selection of interference is connected with a second entrance of the block of rejectee interference with the block of rejectee interference is an output device suppression of narrow-band interference, wherein added a block of memory to store the input counts, and input devices suppression of narrow-band interference is connected to the input of the block of memory, and the memory block is connected with the third entrance of the block of rejectee interference, so that the power spectrum analyzer contains the first module of the discrete Fourier transform (DFT), the input and output of which is connected respectively with input and output block spectrum analyzer calculates DFT input for a given set of frequencies {F}={F 1 , F 2 , ..., F ScanMax }, which is the frequency bins N-point DFT, and ScanMax less than the length DFT N and the set of frequencies {F} after each compute DFT changed so that n/F ScanMax iterations move all N frequency bins, that block allocation of narrowband interference generates a set of

frequency bins employed narrowband interference, containing not more than SuprMax elements that block Ricchi interference contains the second module of the DFT computing the DFT input for the set frequency

, which is the frequency bins N-point DFT, and SuprMax less than the length DFT N, the first input of the second module DFT connected to the first input of the block of rejectee interference, and the second input of the second module DFT is on the second entrance of the block of rejectee interference that carries a set of frequencies {F'} block allocation of interference, so that the power of rejectee interference module contains N-point inverse DFT (DPF), while the output of the second module DFT connected to the first input module ADPF, and a second entrance module ODPF connected with a second entrance of the block of rejectee interference, and N-point ADPF is for SuprMax nonzero input {F'}, the fact that a block of rejectee interference contains adder to the inverting and reinvestiruet inputs, the output of the block ODPF connected to the inverting input of the adder, and its non-inverting input is connected to the third entrance of the block of rejectee interference, and the output of the adder is the output of the block of rejectee interference.

2. The device suppression narrowband interference in satellite navigation receiver according to claim 1, characterized in that the DFT and DPF are implemented using lookup tables (LUT).

3. The device suppression narrowband interference in satellite navigation receiver according to claim 2, characterized in that block of memory for input counts is implemented in the form of a circular buffer, whose length is equal to the length DFT N that N-point DFT in the first and second module DFT are calculated as the income of the input counts at the entrance of the block of memory to store the input counts, gradually forming results for ScanMax and SuprMax frequency bins stored in each module DFT contains blocks of memory for intermediate results DFT on ScanMax and SuprMax elements accordingly, the outputs of the first and second block DFT connected with inputs corresponding blocks of memory, the fact that the N-point ADPF is calculated as the income of the input counts at the entrance of the block of memory to store the input counts and contains a block of memory to hold the results of DFT for SuprMax frequency bins used by the module ODPF as input parameters, and the entrance of the block of memory to store the results DFT connected to the module input DPF, the fact that the output of the block of memory for the intermediate results of the second module DFT and the entrance of the block of memory to store the results DFT linked other through the switch.

4. The device suppression narrowband interference in satellite navigation receiver according to claim 3, wherein when a new input of reference in the block of memory to store the input counts from circular buffer to read the input count received in N steps previously newly arrived, and at receipt of the N-th input reference calculation of the N-point DFT in the first and second module DFT is completed and the intermediate results DFT second module is copied to the memory block for results DFT module ADPF, then a block of memory for intermediate DFT results in both modules DFT is set to zero.