CN116886128A - Method and device for generating and detecting characteristic current based on Chirp signal - Google Patents
Method and device for generating and detecting characteristic current based on Chirp signal Download PDFInfo
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Abstract
The application relates to the technical field of power line communication, and discloses a method and a device for generating and detecting characteristic current based on a Chirp signal. In one embodiment, two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth with opposite frequency modulation directions are adopted to represent binary different bit signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals and the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals, a characteristic current time sequence is generated based on the Chirp signals, and a time stamp of the characteristic current sequence based on a forward zero crossing point of the Chirp signals is used as a switching timing point and an effective switching duration is used as a switching duration to switch current of a low-voltage radio supply area into power frequency current on a power line. Since the autocorrelation performance of the Chirp signal is very special, the detection capability of the characteristic current can be very strong.
Description
Technical Field
The application relates to the technical field of power line communication, in particular to a method and a device for generating and detecting characteristic current based on a Chirp signal.
Background
This section is intended to provide a background or context to the embodiments of the application that are recited in the claims. The description herein is not admitted to be prior art by inclusion in this section.
The early power line power frequency communication is a communication technology for superimposing small distortion on the voltage or current of a power grid to transmit information, such as TWACS (two-way power frequency communication technology), and the technology can complete communication identification between devices by installing a distortion signal transmitting end and a distortion signal receiving end at different positions of the power grid, so that the technology has great benefits in the fields of power distribution automation and the like, but the power line is not a special communication line, and noise such as harmonic waves generated by a complex structure of a low-voltage station area and various electric loads can generate great interference on the power frequency communication, especially in the synchronous part of the power frequency communication.
The power saving company of Zhejiang, national net, introduced technical Specification for household transformation relation identification based on characteristic Current, part 1, month 1, 2021: and (3) sending a current signal, namely, issuing at least two rounds of topology identification parameters through a characteristic current communication technology, and respectively creating at least two rounds of topology identification execution result tables by the energy controller according to the topology identification parameters issued by the master station. Meanwhile, through at least two rounds of topology identification task execution, the master station can accurately acquire the identification result of each station area, and then can accurately comb out a station area topology identification structure diagram, so that the station area topology identification is completed rapidly and accurately, the scheme is simple and practical, and the low-voltage station area topology identification method and device based on the characteristic signals are easy to realize.
The communication synchronization is the basis of accurately receiving information by a receiving end, at present, a signal with a specific frequency (such as 833.33 Hz) is mainly switched in the power frequency current, data is transmitted in an OOK (on-off keying) modulation mode, and the single-frequency signal is compared at the receiving end to complete synchronization and demodulation, so that the data is recovered. But the frequency domain synchronization is greatly affected by interference, and the transmission current power is relatively high. In addition, because the characteristic current of switching is a single-frequency sine wave, a 783.33/883.33Hz main frequency component is formed after the characteristic current is modulated by the frequency of a power frequency signal (such as 50 Hz), and abundant odd harmonic components are added, so that strong harmonic pollution is caused to a power grid, and the power quality of the power grid is reduced. Since the detection success rate of the characteristic current switched by single frequency is completely dependent on the signal quality of 783.33Hz and 883.33Hz frequency points, namely: signal to noise ratio. The ideal power frequency is 50Hz, the actual power frequency can float between 48Hz and 52Hz, and when the power frequency is 49Hz, the 16 and 18 harmonics thereof fall just near the frequency points of 783.33Hz and 883.33Hz respectively; similarly, when the power frequency is 52Hz, 15 and 17 harmonics of the power frequency also just fall near 783.33Hz and 883.33Hz frequency points respectively, so that the detection success rate of the characteristic current is affected.
Disclosure of Invention
The application aims to provide a method and a device for generating and detecting characteristic current based on a Chirp signal, which have strong characteristic current detection capability, especially single-frequency interference resistance, because the self-correlation performance of the Chirp signal is very special, so that lower transmitting current or shorter symbol length can be adopted under the condition of equal receiving performance compared with the prior scheme.
The application discloses a characteristic current generation method based on a Chirp signal, which comprises the following steps:
two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth in opposite frequency modulation directions are adopted to represent binary different bit signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals, the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals, and a characteristic current time sequence is generated based on the Chirp signals; and
and taking a time stamp of the characteristic current sequence based on the forward zero crossing point of the Chirp signal as a switching timing point and the effective switching duration as switching duration to switch the current of the low-voltage power supply station area into the power frequency current on the power line.
In a preferred embodiment, the duty cycle of the switched current signal is a constant value, or the effective switching duration of the switched current signal is inversely proportional to the instantaneous frequency of the Chirp signal.
In a preferred embodiment, the effective switching duration of the switched current signal is a constant value.
In a preferred embodiment, the switching period of each bit in the characteristic current sequence is an integer multiple of the period of the power frequency current, and the starting point of the switching is the positive zero crossing point or the negative zero crossing point of the power frequency current.
In a preferred embodiment, the frequency of the rising Chirp signal varies from low to high to represent binary bit 1 and the frequency of the falling Chirp signal varies from high to low to represent binary bit 0.
In a preferred embodiment, the frequency of the rising Chirp signal varies from low to high to represent binary bit 0 and the frequency of the falling Chirp signal varies from high to low to represent binary bit 1.
In a preferred embodiment, the rising Chirp signal or the falling Chirp signal represents a binary bit 1, and a switching current value of 0 represents a binary bit 0.
In a preferred embodiment, the product of the spread bandwidth and the information bandwidth of the Chirp signal is much larger than 1, wherein the information bandwidth is the inverse of the bit symbol duration.
The application also discloses a characteristic current generating device based on the Chirp signal, which comprises:
the time sequence generation module is used for representing binary different bit signals by adopting two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth and opposite frequency modulation directions, and generating a characteristic current time sequence by using an information coding sequence to be transmitted based on the Chirp signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals and the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals; and
and the switching module is used for switching the current of the low-voltage power supply station area into the power frequency current on the power line by taking the time stamp of the characteristic current sequence based on the forward zero crossing point of the Chirp signal as a switching timing point and the effective switching duration as switching duration.
The application also discloses a characteristic current detection method based on the Chirp signal, which comprises the following steps:
analog-to-digital conversion is carried out on the current signal on the power line;
the current signals after the analog-to-digital conversion are respectively subjected to cross correlation calculation with the local rising Chirp signals and the local falling Chirp signals to obtain related reference signals, and low-pass filtering is respectively carried out;
subtracting the low-pass filtered related reference signals;
detecting the peak value of the subtracted related reference signals; and
and judging that the current transmission bit is 0 or 1 according to the polarity of the peak value.
In a preferred embodiment, the step of determining the current transmission bit according to the polarity of the peak value further includes: and judging whether the rising Chirp signal or the falling Chirp signal is detected according to the positive and negative signs of the peaks so as to demodulate the information coding sequence sent on the power line.
In a preferred embodiment, the calculated length of the cross correlation calculation is an integer multiple of the period of the power frequency current, and the calculated starting point is a zero crossing point of the power frequency current.
The application also discloses a characteristic current detection method based on the Chirp signal, which comprises the following steps:
analog-to-digital conversion is carried out on the current signal on the power line;
performing correlation calculation on the current signal after analog-to-digital conversion and the Chirp signal to obtain a correlation reference signal and performing low-pass filtering;
peak value detection is carried out on the low-pass filtered related reference signals; and
and detecting whether a Chirp signal exists in the received signal according to whether the peak value exceeds a preset threshold value, so as to judge whether the current transmitted bit is 1 or 0.
In a preferred embodiment, the Chirp signal is a rising Chirp signal or a falling Chirp signal, wherein the rising Chirp signal represents a Chirp signal whose signal frequency varies from low to high and the falling Chirp signal represents a Chirp signal whose signal frequency varies from high to low.
The application also discloses a characteristic current detection device based on the Chirp signal, which comprises:
the analog-to-digital converter is used for performing analog-to-digital conversion on the current signal on the power line;
a rising Chirp signal correlator coupled to the analog-to-digital converter and configured to perform a cross-correlation calculation on the analog-to-digital converted current signal and a local rising Chirp signal;
a first low pass filter coupled to the rising Chirp signal correlator and low pass filtering the resulting correlated reference signal;
a falling Chirp signal correlator coupled to the analog-to-digital converter and configured to perform a cross-correlation calculation on the analog-to-digital converted current signal and a local falling Chirp signal;
a second low pass filter coupled to the falling Chirp signal correlator and low pass filtering the resulting correlated reference signal;
an adder coupled to the first and second low pass filters and subtracting the low pass filtered correlated reference signals;
a peak detector coupled to the adder and detecting a peak value of the subtracted correlation reference signal; and
a determiner coupled to the peak detector and demodulating the currently transmitted bit to be either "0" or "1" depending on the polarity of the peak.
The application discloses a method and a device for generating and detecting a characteristic current signal based on Chirp. According to the method, the characteristic current pulse modulated by Chirp is switched by the on-off load of the transmitting end, the current signal is subjected to relevant demodulation at the receiving end, and the current signal carrying information is identified to complete communication synchronization. Because the Chirp signal has the characteristics of broadband, low power spectral density and noise-like property, the influence on the electric energy quality of the power grid is relatively small. Meanwhile, as the autocorrelation performance of the Chirp signal is very special, the characteristic current detection capability is very strong, especially the single-frequency interference resistance capability is achieved, and therefore, lower sending current or shorter symbol length can be adopted compared with the existing scheme under the condition of the same receiving performance. The application can also adjust the pulse width to be inversely proportional to the instantaneous frequency of the Chirp signal, thereby achieving the purpose of adjusting the frequency spectrum density shape of the transmitted signal, leading the transmitted signal to present broadband white noise characteristics and reducing the influence on a power grid.
The numerous technical features described in the description of the present application are distributed among the various technical solutions, which can make the description too lengthy if all possible combinations of technical features of the present application (i.e., technical solutions) are to be listed. In order to avoid this problem, the technical features disclosed in the above summary of the application, the technical features disclosed in the following embodiments and examples, and the technical features disclosed in the drawings may be freely combined with each other to constitute various new technical solutions (which should be regarded as having been described in the present specification) unless such a combination of technical features is technically impossible. For example, in one example, feature a+b+c is disclosed, in another example, feature a+b+d+e is disclosed, and features C and D are equivalent technical means that perform the same function, technically only by alternative use, and may not be adopted simultaneously, feature E may be technically combined with feature C, and then the solution of a+b+c+d should not be considered as already described because of technical impossibility, and the solution of a+b+c+e should be considered as already described.
Drawings
Fig. 1 is a flowchart of a characteristic current generation method based on a Chirp signal according to a first embodiment of the present application.
Fig. 2 is a schematic diagram of a Chirp signal waveform in accordance with one embodiment of the present application.
Fig. 3 is a schematic diagram of a burst generated based on a Chirp signal in one embodiment in accordance with the application.
Fig. 4 is a schematic diagram of a switching signal based on a fixed closing time generated by a Chirp signal in accordance with one embodiment of the present application.
Fig. 5 is a schematic diagram of the power spectral density of a switching signal for a fixed closing time in accordance with one embodiment of the application.
Fig. 6 is a schematic diagram of a switching signal based on a variable closing time generated by a Chirp signal in accordance with one embodiment of the present application.
Fig. 7 is a schematic diagram of the power spectral density of a switching signal with variable closing time in accordance with one embodiment of the present application.
Fig. 8 is a schematic diagram of OOK and BOK modulation waveforms based on a Chirp signal in accordance with one embodiment of the present application.
Fig. 9 is a schematic structural diagram of a characteristic current generating device based on a Chirp signal in a third embodiment according to the present application.
Fig. 10 is a schematic diagram of a correlator output waveform in accordance with one embodiment of the present application.
Fig. 11 is a flowchart of a characteristic current detection method based on a Chirp signal according to a fourth embodiment of the present application.
Fig. 12 is a flowchart of a characteristic current detection method based on a Chirp signal in a fifth embodiment according to the present application.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be understood by those skilled in the art that the claimed application may be practiced without these specific details and with various changes and modifications from the embodiments that follow.
The following outline of some of the innovative features of embodiments of the present application:
in order to overcome the problems mentioned in the prior art, the application discloses a method and a device for generating and detecting a characteristic current signal based on Chirp. According to the method, the characteristic current pulse modulated by Chirp is switched by the on-off load of the transmitting end, the current signal is subjected to relevant demodulation at the receiving end, and the current signal carrying information is identified to complete communication synchronization. Because the Chirp signal has the characteristics of broadband, low power spectral density and noise-like property, the influence on the electric energy quality of the power grid is relatively small. Meanwhile, as the autocorrelation performance of the Chirp signal is very special, the characteristic current detection capability is very strong, especially the single-frequency interference resistance capability is achieved, and therefore, lower sending current or shorter symbol length can be adopted compared with the existing scheme under the condition of the same receiving performance. Furthermore, the application can adjust the pulse width to be inversely proportional to the instantaneous frequency of the Chirp signal, thereby achieving the purpose of adjusting the spectrum density shape of the transmitted signal, leading the transmitted signal to present broadband white noise characteristics and reducing the influence on a power grid.
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.
A first embodiment of the present application relates to a method for generating a characteristic current based on a Chirp signal, the flow of which is shown in fig. 1, the method comprising the steps of:
step 101, using two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth in opposite frequency modulation directions to represent binary different bit signals. A Chirp signal in which the signal frequency varies from low to high is referred to as a rising Chirp signal, and a Chirp signal in which the signal frequency varies from high to low is referred to as a falling Chirp signal. And generating a characteristic current time sequence based on the Chirp signal and the information coding sequence to be transmitted.
And 102, performing current switching on the low-voltage power supply station area to power frequency current on a power line by taking a time stamp of a forward zero crossing point of a characteristic current sequence based on a Chirp signal as a switching timing point and an effective switching duration as switching duration.
The characteristic current is generated based on a switching signal generated by a Chirp signal (i.e., a Chirp signal). Chirp is a spread spectrum modulation technique that does not require a pseudo-random code sequence. Since the frequency bandwidth occupied by the chirp signal is much larger than the information bandwidth, a large system processing gain can also be obtained. The chirp technology is widely used in radar and sonar technologies, for example, in radar positioning technology, it can be used to increase the radio frequency pulse width, increase the communication distance, increase the average transmitting power, and at the same time, maintain a sufficient signal spectrum width without reducing the range resolution of the radar.
The Chirp signal refers to a signal in which the instantaneous frequency varies linearly with time. The time domain expression of the Chirp signal can be written as (with amplitude normalization, initial phase zero):
wherein omega 0 Is the center angular frequency of the Chirp signal. According to the definition of the spread spectrum processing gain, the spread bandwidth of the signal is approximately equal to B and the information bandwidth is 1/T, so the processing gain brought by the spectrum spreading is equal to BT, and the time bandwidth product is usually selected as BT > 1. In the analysis of the signal matched filter detection, BT is the maximum peak of the matched filter output.
In one embodiment, the product of the spread bandwidth and the information bandwidth of the Chirp signal is much greater than 1, where the information bandwidth is the inverse of the bit symbol duration.
The current modulation method for Chirp spread spectrum communication can use two orthogonal Chirp signals to form binary quadrature keying (Binary orthogonal keying, BOK). In a BOK system, two orthogonal Chirp signals are used, whose Chirp directions (Chirp directions) are exactly opposite. One is positive (i.e. signal frequency changes from low to high), called rising Chirp signal or up-Chirp, and the other is negative (i.e. signal frequency changes from high to low), called falling Chirp signal or down-Chirp, respectively, used to represent different bit signals. For example, "1" is represented by up-chirp, and "0" is represented by down-chirp. The time domain expressions of the Up-chirp and Down-chirp signals are respectively
Wherein, we change Chirp symbol time to 0.ltoreq.t.ltoreq.T for convenience of description. It should be noted that the rising Chirp signal is perfectly orthogonal to the falling Chirp signal, i.e.: their cross-correlation is zero, forming a pair of quadrature modulated signals.
In one embodiment, the rising Chirp signal with a frequency that varies from low to high represents binary bit 1 and the falling Chirp signal with a frequency that varies from high to low represents binary bit 0.
In another embodiment, the frequency of the rising Chirp signal varies from low to high to represent binary bit 0 and the frequency of the falling Chirp signal varies from high to low to represent binary bit 1.
The characteristic current based on the Chirp signal is different from the existing characteristic current signal, and the frequency of the characteristic current is linearly changed along with the time. Given a bit symbol duration T, chirp center frequency f 0 And the bandwidth B of the spread spectrum, the corresponding Chirp signal is generated according to the formula c (t), and the waveform of the Chirp signal is shown in figure 2. The forward zero crossing pulse sequence is then extracted and the pulse train generated based on the Chirp signal (fixed closure time) is shown in fig. 3. The pulse width of the high level can be set constant or inversely proportional to the frequency factor, and the power spectral density of the fixed on-time switching signal is shown in fig. 5. The pulse train (variable on-time) generated based on the Chirp signal is shown in fig. 6, and the power spectral density of the variable on-time switching signal is shown in fig. 7. If the pulse width of the high level is set to be constant, since the duty ratio of the Chirp signal corresponding to the low frequency part is relatively low, the power spectral density corresponding to the low frequency part is also relatively low (as shown in fig. 5). In order to make the power spectral density of the switching signal relatively flat in the frequency band used, the duty cycle of the switching signal may be set to be variable so that it is inversely proportional to the Chirp instantaneous frequency (as shown in fig. 6), and the corresponding switching signal power spectral density is relatively flat in the frequency band used (as shown in fig. 7).
In one embodiment, the duty cycle of the switched current signal is a constant value, or the effective switching duration of the switched current signal is inversely proportional to the instantaneous frequency of the Chirp signal.
In one embodiment, the effective switching duration of the switched current signal is a constant value.
In one embodiment, the switching period of each bit in the characteristic current sequence is an integer multiple of the period of the power frequency current, and the starting point of switching is the positive zero crossing point or the negative zero crossing point of the power frequency current.
In other embodiments, the rising Chirp signal or the falling Chirp signal may be used to represent binary bit 1, where the switching current value is 0 to represent binary bit 0, so as to implement On-Off Keying (OOK) modulation On the information bit.
The second embodiment of the application also discloses a characteristic current generating device based on the Chirp signal, which comprises a time sequence generating module and a switching module. The characteristic current generating device in the second embodiment may be used to generate the characteristic current in the first embodiment. Two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth in opposite frequency modulation directions are adopted to represent binary different bit signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals, the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals, and a time sequence generation module generates characteristic current time sequences based on the Chirp signals. The switching module is used for switching the current of the low-voltage power supply station area into the power frequency current on the power line by taking the time stamp of the forward zero crossing point of the characteristic current sequence based on the Chirp signal as a switching timing point and the effective switching duration as switching duration.
The switching method synchronous with the power frequency zero crossing can greatly reduce the frame synchronous detection of the characteristic current based on the Chirp signal, and comprises the following specific steps:
step 1: generating a characteristic current time sequence based on the Chirp signal, and performing current switching on the low-voltage power supply station area by taking a time stamp of the sequence as a switching timing point, wherein the switching duration can be fixed or variable, and the switching period of each bit is the symbol length of the Chirp signal and T (for example, T=0.12 sec). Because the power frequency is not strictly 50Hz/60Hz, the switching bit period is selected as an integral multiple of the power frequency period, thereby ensuring that the switching point of the next bit is synchronous with the power zero crossing. The modulation mode may be OOK or BOK, as shown in fig. 8.
Step 2: the receiving end filters and samples the current signals, performs cross correlation calculation on the received signals, calculates a length bit T, and calculates a power frequency zero crossing point of a starting point bit. The correlation calculation length T approximates to an integer multiple of the power frequency period. And then moving to the next relevant calculation window in the sliding length bit power frequency period.
The third embodiment of the present application also discloses a characteristic current detecting device based on a Chirp signal, the structure of which is shown in fig. 9, and the characteristic current detecting device in the third embodiment can be used for detecting the characteristic current generated in the first or second embodiment. The device comprises: an analog-to-digital converter (ADC) 901, a rising Chirp signal correlator 902, a first Low Pass Filter (LPF) 903, a falling Chirp signal correlator 904, a second low pass filter 905, an adder 906, a peak detector 907, and a determiner 908.
The analog-to-digital converter 901 is used for analog-to-digital converting a current signal on a power line. The rising Chirp signal correlator 902 is coupled to the analog-to-digital converter 901 and is used to perform a cross-correlation calculation of the analog-to-digital converted current signal with the local rising Chirp signal. The first low pass filter 903 is coupled to the rising Chirp signal correlator 902 and low pass filters the resulting correlated reference signal. The falling Chirp signal correlator 904 is coupled to the analog-to-digital converter 901 and is used to cross-correlate the analog-to-digital converted current signal with the local falling Chirp signal. The second low pass filter 905 is coupled to the falling Chirp signal correlator and low pass filters the resulting correlated reference signal. Adder 906 is coupled to first low-pass filter 903 and second low-pass filter 905 and subtracts the low-pass filtered correlated reference signals. A peak detector 907 is coupled to the adder 906 and detects the peak value of the subtracted correlation reference signal. Decision device 908 is coupled to peak detector 907 and demodulates the currently transmitted bits to either a "0" or a "1" depending on the polarity of the peak.
Wherein, the correlation reference signal of the correlator can be generated in advance according to the following formula:
wherein f AC Is a power frequency, typically 50Hz/60Hz. Since Chirp is a linear frequency modulation signal, the signal R is modulated by power frequency up (t) and R down (t) is composed of two chirped signals superimposed, while retaining many of the advantages of chirped signals.
Note that when the BOK modulation is used to generate the characteristic current, the rising Chirp signal correlator 902 and the falling Chirp signal correlator 904 are used to perform correlation calculation, respectively, whereas when the OOK modulation is used to generate the characteristic current, the rising Chirp signal correlator 902 alone or the falling Chirp signal correlator 904 alone may be used to perform correlation calculation. A schematic diagram of the output waveform of the correlator is shown in fig. 10.
The fourth embodiment of the application also discloses a characteristic current detection method based on a Chirp signal, the detection method is suitable for switching current modulated by BOK, the detection flow is shown in figure 11, and the method comprises the following steps:
step 1101, performing analog-to-digital conversion on the current signal on the power line.
In step 1102, the current signals after the analog-to-digital conversion are respectively cross-correlated with the local rising Chirp signal and the local falling Chirp signal to obtain related reference signals, and each of the reference signals is subjected to low-pass filtering.
In step 1103, the low-pass filtered correlated reference signals are subtracted.
In step 1104, a peak value of the subtracted correlation reference signal is detected.
Step 1105, determining the current transmission bit as "0" or "1" according to the polarity of the peak value.
In one embodiment, the calculated length of the cross-correlation calculation is an integer multiple of the period of the power frequency current, and the calculated starting point is the power frequency current zero-crossing point.
In one embodiment, the step of determining the current transmission bit according to the polarity of the peak value further comprises: and judging whether the rising Chirp signal or the falling Chirp signal is detected according to the positive and negative signs of the peaks, so as to demodulate the information coding sequence sent on the power line.
The fifth embodiment of the present application also discloses a characteristic current detection method based on a Chirp signal, the detection method is suitable for switching current modulated by OOK, a detection flow is shown in fig. 12, the method comprises the following steps:
step 1201, performing analog-to-digital conversion on a current signal on a power line;
step 1202, performing correlation calculation on the current signal after analog-to-digital conversion and the Chirp signal to obtain a correlation reference signal and performing low-pass filtering;
step 1203, performing peak detection on the low-pass filtered correlation reference signal; and
in step 1204, whether a Chirp signal exists in the received signal is detected according to whether the peak exceeds a preset threshold, so as to determine whether the current transmission bit is "1" or "0".
In one embodiment, the Chirp signal is a rising Chirp signal or a falling Chirp signal, wherein the rising Chirp signal represents a Chirp signal whose signal frequency varies from low to high and the falling Chirp signal represents a Chirp signal whose signal frequency varies from high to low.
According to the application, the characteristic current pulse modulated by Chirp is switched by the on-off load of the transmitting end, the current signal is subjected to relevant demodulation at the receiving end, and the current signal carrying information is identified to complete communication synchronization. If a switching mode synchronous with the power frequency is adopted, the receiving end can judge the direction of the characteristic current through the positive and negative of the correlation value, the relative positions of the transmitting end and different receiving ends in the low-voltage station area are determined, and the power of the transmitting current is reduced. The application can also adjust the pulse width to be inversely proportional to the instantaneous frequency of the Chirp signal, thereby achieving the purpose of adjusting the spectrum density shape of the transmitted signal, leading the transmitted signal to present broadband white noise characteristics and reducing the influence on a power grid.
It should be noted that in the present patent application, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. In the present patent application, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, and two cases are included: the act is performed solely on the basis of the element and is performed on the basis of the element and other elements. Multiple, etc. expressions include 2, 2 times, 2, and 2 or more, 2 or more times, 2 or more.
All references mentioned in this specification are to be considered as being included in the disclosure of the application in its entirety so as to be applicable as a basis for modification when necessary. Furthermore, it should be understood that the foregoing description is only of the preferred embodiments of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement, or the like, which is within the spirit and principles of one or more embodiments of the present disclosure, is intended to be included within the scope of one or more embodiments of the present disclosure.
In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
Claims (15)
1. A method for generating a characteristic current based on a Chirp signal, comprising:
two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth in opposite frequency modulation directions are adopted to represent binary different bit signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals, the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals, and a characteristic current time sequence is generated based on the Chirp signals; and
and taking a time stamp of the characteristic current sequence based on the forward zero crossing point of the Chirp signal as a switching timing point and the effective switching duration as switching duration to switch the current of the low-voltage power supply station area into the power frequency current on the power line.
2. The method of claim 1, wherein the duty cycle of the switched current signal is a constant value, or wherein the effective switching duration of the switched current signal is inversely proportional to the instantaneous frequency of the Chirp signal.
3. The method of claim 1, wherein the effective switching duration of the switched current signal is a constant value.
4. The method of claim 1, wherein the switching period of each bit in the sequence of characteristic currents is an integer multiple of the period of the power frequency current, and the starting point of the switching is a positive zero-crossing or a negative zero-crossing of the power frequency current.
5. The method of claim 1, wherein the rising Chirp signal has a frequency that varies from low to high representing binary bit 1 and the falling Chirp signal has a frequency that varies from high to low representing binary bit 0.
6. The method of claim 1, wherein the rising Chirp signal has a frequency that varies from low to high representing binary bit 0 and the falling Chirp signal has a frequency that varies from high to low representing binary bit 1.
7. The method of claim 1, wherein the rising Chirp signal or the falling Chirp signal represents a binary bit 1 and the switching current value of 0 represents a binary bit 0.
8. The method of claim 1, wherein the product of the spread bandwidth and the information bandwidth of the Chirp signal is substantially greater than 1, wherein the information bandwidth is the inverse of the bit symbol duration.
9. A Chirp signal-based characteristic current generation device, comprising:
the time sequence generation module is used for representing binary different bit signals by adopting two orthogonal Chirp signals with given bit symbol duration, center frequency and spread spectrum bandwidth and opposite frequency modulation directions, and generating a characteristic current time sequence by using an information coding sequence to be transmitted based on the Chirp signals, wherein the Chirp signals with signal frequencies changing from low to high are called rising Chirp signals and the Chirp signals with signal frequencies changing from high to low are called falling Chirp signals; and
and the switching module is used for switching the current of the low-voltage power supply station area into the power frequency current on the power line by taking the time stamp of the characteristic current sequence based on the forward zero crossing point of the Chirp signal as a switching timing point and the effective switching duration as switching duration.
10. The characteristic current detection method based on the Chirp signal is characterized by comprising the following steps of:
analog-to-digital conversion is carried out on the current signal on the power line;
the current signals after the analog-to-digital conversion are respectively subjected to cross correlation calculation with the local rising Chirp signals and the local falling Chirp signals to obtain related reference signals, and low-pass filtering is respectively carried out;
subtracting the low-pass filtered related reference signals;
detecting the peak value of the subtracted related reference signals; and
and judging that the current transmission bit is 0 or 1 according to the polarity of the peak value.
11. The method of claim 10, wherein the step of determining the currently transmitted bit based on the polarity of the peak value further comprises: and judging whether the rising Chirp signal or the falling Chirp signal is detected according to the positive and negative signs of the peaks so as to demodulate the information coding sequence sent on the power line.
12. The method of claim 10, wherein the calculated length of the cross-correlation calculation is an integer multiple of the period of the power frequency current, and the calculated starting point is a power frequency current zero crossing point.
13. The characteristic current detection method based on the Chirp signal is characterized by comprising the following steps of:
analog-to-digital conversion is carried out on the current signal on the power line;
performing correlation calculation on the current signal after analog-to-digital conversion and the Chirp signal to obtain a correlation reference signal and performing low-pass filtering;
peak value detection is carried out on the low-pass filtered related reference signals; and
and detecting whether a Chirp signal exists in the received signal according to whether the peak value exceeds a preset threshold value, so as to judge whether the current transmitted bit is 1 or 0.
14. The method of claim 13, wherein the Chirp signal is a rising Chirp signal or a falling Chirp signal, wherein the rising Chirp signal represents a Chirp signal with a signal frequency that varies from low to high and the falling Chirp signal represents a Chirp signal with a signal frequency that varies from high to low.
15. A Chirp signal-based characteristic current detection device, comprising:
the analog-to-digital converter is used for performing analog-to-digital conversion on the current signal on the power line;
a rising Chirp signal correlator coupled to the analog-to-digital converter and configured to perform a cross-correlation calculation on the analog-to-digital converted current signal and a local rising Chirp signal;
a first low pass filter coupled to the rising Chirp signal correlator and low pass filtering the resulting correlated reference signal;
a falling Chirp signal correlator coupled to the analog-to-digital converter and configured to perform a cross-correlation calculation on the analog-to-digital converted current signal and a local falling Chirp signal;
a second low pass filter coupled to the falling Chirp signal correlator and low pass filtering the resulting correlated reference signal;
an adder coupled to the first and second low pass filters and subtracting the low pass filtered correlated reference signals;
a peak detector coupled to the adder and detecting a peak value of the subtracted correlation reference signal; and
a determiner coupled to the peak detector and demodulating the currently transmitted bit to be either "0" or "1" depending on the polarity of the peak.
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| CN117895977B (en) * | 2024-03-18 | 2024-05-28 | 青岛鼎信通讯科技有限公司 | Characteristic current information bit identification method |
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