Digital automatic gain control structure in the receiving process of power line carrier communication

Abstract

The invention discloses a digital automatic gain control structure in a power line carrier communication receiving process, relates to the technical field of power line carrier communication, solves the technical problem that narrowband interference has a great influence on accurate evaluation of signal energy, and the key points of the technical solution are to realize rapid adjustment of large signal saturation and accurate counting and analysis of pulse interference through an energy saturation preprocessing unit; to realize detection and suppression of narrowband interference signals in and out of the band through a narrowband interference detection and suppression unit, thereby improving the accuracy of effective signal energy estimation; to realize rapid convergence of a power line carrier signal with continuously changing amplitude through an exponential sliding averager, thereby effectively reducing the jitter of gain adjustment.

Description

Technical Field

[0001] The present application relates to the technical field of power line carrier communication, and in particular to a digital automatic gain control structure in a power line carrier communication receiving process. Background Art

[0002] Power Line Communication (PLC) uses existing power lines as a signal transmission medium to achieve data transmission. As a type of wired communication system, it has the characteristics of wide coverage and low access cost, so it has also been widely used in smart meter reading, power equipment monitoring and smart home. With the advancement of communication technology, power line communication will also take on more business needs.

[0003] As a medium for transmitting electric energy, the channel characteristics of power lines are not ideal for the application scenarios of carrier communication. The main reasons are that the characteristic impedance of the transmission medium is unstable, the signal amplitude-frequency response is not flat, and the high-frequency part is severely attenuated. At the same time, due to the differences in the working conditions of the electrical equipment carried on the transmission power line, various interferences and noises will be caused, mainly including narrowband interference, pulse interference and white noise. In order to effectively improve the spectrum utilization rate, carrier communication adopts OFDM (orthogonal spectrum multiplexing) technology, and uses cyclic prefix, pseudo-random scrambling code and diversity copy coding technology in the signal modulation process to improve the anti-interference performance. However, the characteristic of OFDM technology is that the peak-to-average signal power is relatively large, about 12db, which easily leads to distortion of the received signal and puts forward higher requirements on the automatic gain control performance of the receiver.

[0004] The existing more common power line carrier communication automatic gain control technology often focuses on the dynamic range and adjustment accuracy, without fully considering the complex electromagnetic environment where interference and noise coexist on the power line, and ignores the rapid changes in the amplitude of the received signal, resulting in poor consistency in gain adjustment and insufficient accuracy in useful signal power assessment, leading to a decline in receiver performance. Summary of the invention

[0005] The present application provides a digital automatic gain control structure in the power line carrier communication receiving process, the technical purpose of which is to reduce the influence of narrowband interference on the accurate evaluation of signal energy, and to improve the anti-interference ability of the receiver by reasonably allocating analog gain and digital gain, and the automatic gain control convergence result has good consistency.

[0006] The above technical objectives of this application are achieved through the following technical solutions:

[0007] A digital automatic gain control structure in a power line carrier communication receiving process, comprising an analog front-end module, a software processing module and a digital hardware module connected in sequence;

[0008] The analog front-end module includes an analog programmable amplifier and an analog-to-digital converter, and the output of the analog programmable amplifier is input to the analog-to-digital converter;

[0009] The software processing module includes an energy saturation preprocessing unit, a narrowband interference detection and suppression unit and a gain distributor; the output of the analog-to-digital converter is input to the energy saturation preprocessing unit, and the output of the energy saturation preprocessing unit is input to the gain distributor and the narrowband interference detection and suppression unit respectively;

[0010] The digital hardware module includes a digital amplifier, an energy evaluation and error calculation unit and an exponential sliding averager; the output of the narrowband interference detection and suppression unit is input to the digital amplifier, the output of the digital amplifier is input to the energy evaluation and error calculation unit, and the output of the energy evaluation and error calculation unit is input to the exponential sliding averager;

[0011] The exponential sliding averager is connected to the gain divider, and the output of the gain divider is input to the digital amplifier and the analog programmable amplifier respectively.

[0012] Furthermore, the energy saturation preprocessing unit includes an energy saturation depth estimation unit, a pulse interference judgement device, a pulse interference limiter and a gain control table; the analog-to-digital converter is connected to the energy saturation depth estimation unit, the energy saturation depth estimation unit is connected to the pulse interference judgement device, the pulse interference judgement device is connected to both the pulse interference limiter and the gain control table, the pulse interference limiter is connected to the gain control table; the gain control table is connected to the gain distributor.

[0013] Furthermore, the narrowband interference detection and suppression unit includes a narrowband detector, a narrowband notch filter and a FIR filter, the narrowband detector is connected to both the narrowband notch filter and the FIR filter; the pulse interference determiner is connected to the narrowband detector, and the FIR filter is connected to the digital amplifier.

[0014] Furthermore, the energy evaluation and error calculation unit includes an energy calculation unit, a logarithmic transformation unit and an energy error calculation unit which are connected in sequence; the digital amplifier is connected to the energy calculation unit, and the energy error calculation unit is connected to the exponential sliding averager.

[0015] The beneficial effects of the present application are as follows: according to the automatic gain control loop implemented by the digital automatic gain control structure in the power line carrier communication receiving process of the present application, rapid adjustment of large signal saturation and accurate counting and analysis of pulse interference are achieved through the energy saturation preprocessing unit; detection and suppression of narrowband interference signals in and out of the band are achieved through the narrowband interference detection and suppression unit, thereby improving the accuracy of effective signal energy estimation; rapid convergence of the power line carrier signal with continuously changing amplitude is achieved through the exponential sliding average, thereby effectively reducing the jitter of gain adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural diagram of the digital automatic gain control structure described in this application;

[0017] Figure 2 It is a structural schematic diagram of an energy saturation preprocessing unit;

[0018] Figure 3 It is a structural schematic diagram of a narrowband interference detection and suppression unit;

[0019] Figure 4 It is a structural diagram of the energy evaluation and error calculation unit;

[0020] Figure 5 This is the schematic diagram of the exponential moving average. DETAILED DESCRIPTION

[0021] The technical solution of the present application will be described in detail below with reference to the accompanying drawings.

[0022] Figure 1 Schematic diagram of the structure of the digital automatic gain control structure in the power line carrier communication receiving process described in this application, such as Figure 1 As shown, the control structure includes an analog front-end module, a software processing module and a digital hardware module which are connected in sequence.

[0023] The analog front-end module includes an analog programmable amplifier and an analog-to-digital converter, and the output of the analog programmable amplifier is input to the analog-to-digital converter. Specifically, the analog programmable amplifier is used to appropriately amplify the analog signal amplitude of the power line carrier to ensure that the analog signal input is at the optimal operating point of the analog-to-digital converter ADC. The ADC is used to perform analog-to-digital conversion on the power line carrier analog signal, and the output digital signal is 12 bits, so the maximum signal amplitude is 2^11, that is, 2048.

[0024] Among them, the effective gain range of the analog programmable amplifier is 18db~56db, and its actual gain is set by the external gain control word. If the gain control word exceeds the setting range, the maximum gain value or the minimum gain value is taken.

[0025] The initial optimal operating point of the ADC is selected as 15db back-off of the ADC input full-scale power, which can be expressed by the following formula: ref =10*logA 2 The selection of reference power ensures that the useful signal will not introduce clipping noise in the ADC part, while meeting the required accuracy of subsequent digital signal processing.

[0026] The software processing module includes an energy saturation preprocessing unit, a narrowband interference detection and suppression unit, and a gain divider; the output of the analog-to-digital converter is input to the energy saturation preprocessing unit, and the output of the energy saturation preprocessing unit is input to the gain divider and the narrowband interference detection and suppression unit respectively. Specifically, the energy saturation preprocessing unit is used to quickly evaluate the energy saturation degree of the input digital signal, and then transmit the saturation information to the gain divider. The gain divider is used to process the signal energy evaluation information, and reasonably adjust the analog gain and digital gain to complete the convergence of the automatic gain control. The narrowband interference detection and suppression unit is used to detect the existence information of narrowband interference and realize narrowband suppression to retain the valid signal.

[0027] The structural diagram of the energy saturation preprocessing unit is as follows: Figure 2 As shown, the energy saturation preprocessing unit includes an energy saturation depth estimation unit, a pulse interference judge, a pulse interference limiter and a gain control table. The energy saturation depth estimation unit, i.e., the software, takes a sample point of the length of an OFDM symbol as a segment, and statistically records the number and distribution of the energy saturation points of the digital signal in the segment, i.e., the number of samples with a signal amplitude equal to 2048, and estimates the signal energy saturation depth in combination with the characteristics of the OFDM signal. If more than 5% of the sample points are energy saturated, the pulse interference judge is started. The pulse interference judge determines whether interference has arrived by comparing the energy difference between the saturated sample points and the average energy difference of other sample points to determine whether the interference has arrived; if the threshold is exceeded, the pulse interference flag is set high, and the width of the statistical pulse interference is calculated. The pulse interference flag enables the pulse interference limiter, and the pulse interference limiter dynamically limits the pulse interference signal according to the width information of the pulse interference obtained by the pulse interference judge and the demodulation requirements of the received signal to prevent saturation in the subsequent FFT transformation. When the signal is saturated and there is no pulse interference, the gain control table will read the energy saturation depth estimation result, directly find the gain step value corresponding to the saturation depth, and transmit it to the gain divider. The gain divider controls the analog programmable amplifier to make corresponding gain changes to achieve rapid coarse adjustment of signal energy.

[0028] The structural diagram of the narrowband interference detection and suppression unit is as follows: Figure 3As shown, the narrowband interference detection and suppression unit includes a narrowband detector, a narrowband notch filter and a FIR filter, the narrowband detector is connected to the narrowband notch filter and the FIR filter; the pulse interference determiner is connected to the narrowband detector, and the FIR filter is connected to the digital amplifier.

[0029] The narrowband detector performs 1024-point FFT energy calculation on the digital signal output by the pulse interference judgement of the energy saturation preprocessing unit, calculates the energy ratio between the adjacent second-largest energy integer frequency point and the maximum energy integer frequency point, and determines the precise frequency of the narrowband noise according to the energy ratio and the direction interval. If the narrowband interference frequency is within the signal passband, the ratio of the narrowband interference energy to the useful signal energy is further evaluated, and the in-band narrowband interference flag is set high. The in-band narrowband interference flag enables the narrowband notch filter. The narrowband notch filter dynamically adjusts the notch frequency and notch depth according to the narrowband interference spectrum position and interference-to-signal ratio results evaluated by the narrowband detector, and notches the energy on the specified subcarrier to retain the effective signal energy to the greatest extent. At the same time, the table is looked up to adjust the optimal operating point of the ADC. The FIR filter adopts a 64-order low-pass filter structure, which can suppress adjacent channel interference by more than 50db and complete the downsampling function at the same time.

[0030] The digital hardware module includes a digital amplifier, an energy evaluation and error calculation unit, and an exponential sliding averager; the output of the narrowband interference detection and suppression unit is input to the digital amplifier, the output of the digital amplifier is input to the energy evaluation and error calculation unit, and the output of the energy evaluation and error calculation unit is input to the exponential sliding averager. Specifically, the digital amplifier is used to amplify the amplitude of the digital signal for use by the subsequent synchronization unit. The energy evaluation and error calculation unit is used to calculate the average signal energy of a symbol of a certain length, and then perform a weighted operation with the dynamic energy threshold to obtain an energy error value. The exponential sliding averager is used to perform an exponential sliding average operation on the energy error value, and select the optimal equilibrium point in terms of energy error control accuracy and gain convergence smoothness.

[0031] The structural diagram of the energy evaluation and error calculation unit is as follows: Figure 4 As shown, the energy evaluation and error calculation unit includes an energy calculation unit, a logarithmic transformation unit and an energy error calculation unit which are connected in sequence; the digital amplifier is connected to the energy calculation unit, and the energy error calculation unit is connected to the exponential sliding averager.

[0032] The existing signal energy calculation method generally adopts the following method:

[0033] Wherein, x(n) represents a digital signal.

[0034] In this application, in order to save the implementation design resources of digital hardware, an approximate signal energy calculation method is selected, including: Wherein, P(n) represents signal energy, M represents the number of digital signal sampling points, I(n) represents the I branch digital signal, and Q(n) represents the Q branch digital signal;

[0035] The logarithmic conversion unit is used to convert the signal energy dimension from the linear unit watt to the logarithmic unit db milliwatt, which can be expressed by the following formula: sig =10*log 10 P(n). Energy error calculation can be expressed by the following formula: P err =P ref -P sig ; Among them, P ref Indicates the preset signal reference threshold energy.

[0036] Figure 5 The schematic diagram of the exponential sliding average is shown in FIG. 1 . The exponential sliding average is connected to a gain divider, and the output of the gain divider is input to a digital amplifier and an analog programmable amplifier respectively.

[0037] The exponential sliding average is used to smooth the gain correction value. It determines different weighting coefficients for the previous gain calibration value and the actual power error value calculated currently (the sum of the two weighting coefficients is 1), which can be expressed by the following formula: G (n) =(1-α)G (n-1) +αP err Among them G (0) =G max , P err (0) = -P ref , α=0.9. Its transfer function is a low-pass filter. When 0<α<2, the automatic gain control system is in an absolutely stable state, which can better overcome the situation of rapid changes in the amplitude of the received signal and improve the consistency of the digital automatic gain control results.

[0038] The gain distributor is used to quantize and encode the nearest integer gain compensation value obtained by the current rounding method into a gain control word available to the analog programmable amplifier and a gain coefficient of the digital amplifier. Then, it is determined whether the integer gain value is within the effective controllable gain range of the analog programmable amplifier. If it is within the effective controllable gain range, the integer gain value is preferentially assigned to the analog programmable amplifier, and the digital amplifier gain coefficient is 1. If it is not within the effective controllable gain range, the effective controllable gain of the analog programmable amplifier is preferentially set to the maximum or minimum according to the integer gain value, and then the gain coefficient of the digital amplifier is set to a value exceeding the effective controllable gain range of the analog programmable amplifier.

[0039] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CDROM, optical storage, etc.) that contain computer-usable program code.

[0040] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0041] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0042] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0043] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A digital automatic gain control structure in a power line carrier communication receiving process, characterized in that: It includes an analog front-end module, a software processing module and a digital hardware module connected in sequence; The analog front-end module includes an analog programmable amplifier and an analog-to-digital converter, and the output of the analog programmable amplifier is input to the analog-to-digital converter; The software processing module includes an energy saturation preprocessing unit, a narrowband interference detection and suppression unit and a gain distributor; the output of the analog-to-digital converter is input to the energy saturation preprocessing unit, and the output of the energy saturation preprocessing unit is input to the gain distributor and the narrowband interference detection and suppression unit respectively; The digital hardware module includes a digital amplifier, an energy evaluation and error calculation unit and an exponential sliding averager; the output of the narrowband interference detection and suppression unit is input to the digital amplifier, the output of the digital amplifier is input to the energy evaluation and error calculation unit, and the output of the energy evaluation and error calculation unit is input to the exponential sliding averager; The exponential sliding average is connected to the gain divider, and the output of the gain divider is input to the digital amplifier and the analog programmable amplifier respectively; Wherein, the energy saturation preprocessing unit includes an energy saturation depth estimation unit, a pulse interference judge, a pulse interference limiter and a gain control table; the analog-to-digital converter is connected to the energy saturation depth estimation unit, the energy saturation depth estimation unit is connected to the pulse interference judge, the pulse interference judge is connected to both the pulse interference limiter and the gain control table, and the pulse interference limiter is connected to the gain control table; the gain control table is connected to the gain distributor; the energy saturation depth estimation unit, i.e., the software, takes an OFDM symbol length sample point as a segment, and statistically records the number and distribution of digital signal energy saturation points in the segment, i.e., the number of samples with a signal amplitude equal to 2048, and estimates the signal energy saturation depth in combination with OFDM signal characteristics; The narrowband interference detection and suppression unit includes a narrowband detector, a narrowband notch filter and an FIR filter, wherein the narrowband detector is connected to both the narrowband notch filter and the FIR filter; the pulse interference determiner is connected to the narrowband detector, and the FIR filter is connected to the digital amplifier; The energy evaluation and error calculation unit comprises an energy calculation unit, a logarithmic transformation unit and an energy error calculation unit which are connected in sequence; the digital amplifier is connected to the energy calculation unit, and the energy error calculation unit is connected to the exponential sliding averager.

2. The control structure according to claim 1, characterized in that The energy calculation unit calculates the signal energy including: Wherein, P(n) represents signal energy, M represents the number of digital signal sampling points, I(n) represents the I branch digital signal, and Q(n) represents the Q branch digital signal; The logarithmic transformation unit transforms the signal energy by: sig =10*log 10 P(n); Then the energy error calculation unit obtains: P err =P ref -P sig ; Among them, P ref Indicates the preset signal reference threshold energy.

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