CN111064529A - Method and device for determining occupied bandwidth and modulation coefficient of modulation signal - Google Patents
Method and device for determining occupied bandwidth and modulation coefficient of modulation signal Download PDFInfo
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B17/00—Monitoring; Testing
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Abstract
The invention provides a method and a device for determining the occupied bandwidth and the modulation coefficient of a modulation signal, wherein the method comprises the following steps: sending a measurement instruction to the tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction; mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal; decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q; the occupied bandwidth and the modulation coefficient of the modulation signal are determined according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion, the problems that in the related technology, the occupied bandwidth and the modulation coefficient of the tested equipment are measured through a frequency spectrograph, the testing speed is low, more frequency spectrometers are needed during batch production, and the cost is high can be solved, the processing speed is increased, the frequency spectrograph is not needed for detection, and the cost is effectively reduced.
Description
Technical Field
The invention relates to the field of intelligent traffic, in particular to a method and a device for determining the occupied bandwidth and the modulation coefficient of a modulation signal.
Background
DSRC (dedicated short-range communication technology) is a communication technology which is specially used for long-distance radio frequency identification in the intelligent traffic field in China, is widely applied in the ETC (electronic toll collection) field, and has a wide development space in the MTC (manual semi-automatic toll collection) field. Currently, DSRC on-board equipment mainly includes an OBU (on-board unit) and a CPC (composite access card). In the ETC field, the OBU is more and more widely applied, and the market reservation is increased day by day. In the field of MTC, CPC is a new generation DSRC product for solving the freeflow problem of the expressway, and is characterized by having 5.8GHz and 13.56MHz communication functions, supporting reading and writing of entrance and exit information and a segmented charging function, being distributed to vehicles in an entrance lane of a closed toll station of the toll road, being recovered in an exit lane and being reusable. In typical application, when an MTC entrance lane writes entrance information into a CPC through 13.56MHz communication, a 5.8GHz function module in a card is started, and a vehicle runs to a 5.8GHz ETC portal frame signal coverage area, an ETC portal frame RSU adopts a 5.8GHz special short-range communication technology to communicate with the CPC, and writes charging information into the CPC card to complete a charging function.
When CPC or OBU are produced and delivered from a factory, the requirements that the occupied bandwidth and the modulation coefficient are within the national standard range must be met, and once the two transmission indexes are unstable, the identification failure in the using process can be caused. Traditional production process flow adopts the frequency spectrograph to measure occupation bandwidth and modulation factor, but when CPC card or OBU's market demand sharply increased, the production line also need carry out large-scale expansion production, and this must purchase a large amount of frequency spectrometers, and the very big increase of manufacturing cost of product is not conform to the interests demand of enterprise.
Aiming at the problems that in the related technology, the occupied bandwidth and the modulation coefficient of the tested equipment are measured through a frequency spectrograph, the testing speed is low, and more frequency spectrometers are needed during batch production, so that the cost is high, a solution is not provided.
Disclosure of Invention
The embodiment of the invention provides a method and a device for determining the occupied bandwidth and the modulation coefficient of a modulation signal, which are used for at least solving the problems that in the related technology, the occupied bandwidth and the modulation coefficient of a tested device are measured through a frequency spectrograph, the testing speed is low, and more frequency spectrometers are needed during batch production, so that the cost is high.
According to an embodiment of the present invention, there is provided a method for determining an occupied bandwidth and a modulation factor of a modulation signal, including:
sending a measurement instruction to a tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction;
mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal;
decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
Optionally, determining the occupied bandwidth and the modulation factor of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion includes:
respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and determining the occupied bandwidth of the modulation signal through fast Fourier transform;
and determining the modulation coefficient of the modulation signal through the intermediate frequency signal I or the intermediate frequency signal Q.
Optionally, taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, respectively, and determining the occupied bandwidth of the modulation signal by fast fourier transform includes:
respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and extracting a predetermined number of points;
performing fast Fourier transform on the predetermined number of points to generate a spectrum of signal amplitude and frequency components, and converting the spectrum into a power spectrum of the intermediate-frequency signal;
and determining the occupied bandwidth of the modulation signal by estimating the sum of the powers of the intermediate frequency signal in the infinite frequency domain through the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths.
Optionally, determining the occupied bandwidth of the modulation signal by estimating the sum of the powers of the intermediate frequency signal in the infinite frequency domain through the sum of the powers of the power maps of the intermediate frequency signal between the occupied bandwidths comprises:
determining the occupied bandwidth of the modulation signal by the way that the ratio of the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths and the sum of the powers in the infinite frequency domain is equal to a predetermined percentage according to the following formula:
Optionally, determining the modulation factor of the modulation signal by the intermediate frequency signal I or the intermediate frequency signal Q includes:
extracting intermediate frequency signals in one or more modulation periods in the intermediate frequency signal I or the intermediate frequency signal Q;
determining an envelope of the intermediate frequency signal within the one or more modulation periods;
obtaining one or more maxima A in the envelopemaxAnd one or more minimum values Amin；
According to the maximum value one or more AmaxAnd the one or more minimum values AminDetermining a modulation coefficient of the modulation signal.
Optionally, according to said one or more maximum values AmaxAnd the one or more minimum values AminDetermining the modulation factor of the modulation signal comprises:
according to said one maximum value AmaxAnd said one minimum value AminDetermining a modulation coefficient M of the modulation signal:
or
According to the plurality of maximum values AmaxAnd the plurality of minimum values AminDetermining a modulation coefficient M of the modulation signal:
wherein N is the maximum value AmaxOr minimum value AminThe number of the cells.
Optionally, mixing the received modulation signal with a local oscillator signal of the radio frequency chip to obtain an intermediate frequency signal includes:
and after mixing the received modulation signal with a local oscillation signal of a radio frequency chip, performing low-pass filtering processing, and outputting the intermediate frequency signal.
According to another embodiment of the present invention, there is also provided an apparatus for determining an occupied bandwidth and a modulation factor of a modulation signal, including:
the sending module is used for sending a measuring instruction to the tested equipment and receiving a modulation signal returned by the tested equipment according to the measuring instruction;
the frequency mixing module is used for mixing the modulation signal with a local oscillation signal of the radio frequency chip to obtain an intermediate frequency signal;
the decomposition module is used for decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and the determining module is used for determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
Optionally, the determining module includes:
the first determining submodule is used for respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal and determining the occupied bandwidth of the modulation signal through fast Fourier transform;
and the second determining submodule is used for determining the modulation coefficient of the modulation signal through the intermediate frequency signal I or the intermediate frequency signal Q.
Optionally, the first determining sub-module includes:
an extraction unit, configured to take the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, respectively, and extract a predetermined number of points;
the generating unit is used for carrying out fast Fourier transform on the predetermined number of points to generate a spectrum of signal amplitude and frequency components, and converting the spectrum into a power spectrum of the intermediate frequency signal;
the first determining unit is used for determining the occupied bandwidth of the modulation signal in a mode of estimating the sum of the powers of the intermediate frequency signal in an infinite frequency domain through the sum of the powers of the power maps of the intermediate frequency signal between the occupied bandwidths.
Optionally, the first determining unit is further configured to
Determining the occupied bandwidth of the modulation signal by the way that the ratio of the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths and the sum of the powers in the infinite frequency domain is equal to a predetermined percentage according to the following formula:
Optionally, the second determining sub-module includes:
an extracting unit, configured to extract an intermediate frequency signal in one or more modulation periods in the intermediate frequency signal I or the intermediate frequency signal Q;
a second determining unit for determining an envelope of the intermediate frequency signal within the one or more modulation periods;
an acquisition unit for acquiring one or more maxima A in the envelopemaxAnd one or more minimum values Amin；
A third determination unit for determiningOne or more of AmaxAnd the one or more minimum values AminDetermining a modulation coefficient of the modulation signal.
Optionally, the third determining unit is further configured to
According to said one maximum value AmaxAnd said one minimum value AminDetermining a modulation coefficient M of the modulation signal:
or
According to the plurality of maximum values AmaxAnd the plurality of minimum values AminDetermining a modulation coefficient M of the modulation signal:
wherein N is the maximum value AmaxOr minimum value AminThe number of the cells.
Optionally, the mixing module is further used for
And after mixing the received modulation signal with a local oscillation signal of a radio frequency chip, performing low-pass filtering processing, and outputting the intermediate frequency signal.
According to a further embodiment of the present invention, a computer-readable storage medium is also provided, in which a computer program is stored, wherein the computer program is configured to perform the steps of any of the above-described method embodiments when executed.
According to yet another embodiment of the present invention, there is also provided an electronic device, including a memory in which a computer program is stored and a processor configured to execute the computer program to perform the steps in any of the above method embodiments.
According to the invention, a measurement instruction is sent to the tested equipment, and a modulation signal returned by the tested equipment according to the measurement instruction is received; mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal; decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q; the occupied bandwidth and the modulation coefficient of the modulation signal are determined according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion, therefore, the problems that in the related technology, the occupied bandwidth and the modulation coefficient of the tested equipment are measured through a frequency spectrograph, the testing speed is low, more frequency spectrometers are needed during batch production, and the cost is high can be solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is a block diagram of a hardware structure of a mobile terminal of a method for determining an occupied bandwidth and a modulation factor of a modulation signal according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for determining an occupied bandwidth and a modulation factor of a modulated signal according to an embodiment of the present invention;
FIG. 3 is a flow diagram of occupied bandwidth determination according to an embodiment of the present invention;
FIG. 4 is a flow chart of modulation factor determination according to an embodiment of the present invention;
fig. 5 is a block diagram of an apparatus for determining an occupied bandwidth and a modulation factor of a modulated signal according to an embodiment of the present invention.
Detailed Description
The invention will be described in detail hereinafter with reference to the accompanying drawings in conjunction with embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
Example 1
The method provided by the first embodiment of the present application may be executed in a mobile terminal, a computer terminal, or a similar computing device. Taking a mobile terminal as an example, fig. 1 is a block diagram of a hardware structure of the mobile terminal of the method for determining an occupied bandwidth and a modulation factor of a modulation signal according to an embodiment of the present invention, as shown in fig. 1, a mobile terminal 10 may include one or more processors 102 (only one is shown in fig. 1) (the processor 102 may include, but is not limited to, a processing device such as a microprocessor MCU or a programmable logic device FPGA, etc.), and a memory 104 for storing data, and optionally, the mobile terminal may further include a transmission device 106 for a communication function and an input/output device 108. It will be understood by those skilled in the art that the structure shown in fig. 1 is only an illustration, and does not limit the structure of the mobile terminal. For example, the mobile terminal 10 may also include more or fewer components than shown in FIG. 1, or have a different configuration than shown in FIG. 1.
The memory 104 may be used to store a computer program, for example, a software program of application software and a module, such as a computer program corresponding to the message receiving method in the embodiment of the present invention, and the processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, so as to implement the method described above. The memory 104 may include high speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory located remotely from the processor 102, which may be connected to the mobile terminal 10 via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The transmission device 106 is used for receiving or transmitting data via a network. Specific examples of the network described above may include a wireless network provided by a communication provider of the mobile terminal 10. In one example, the transmission device 106 includes a Network adapter (NIC), which can be connected to other Network devices through a base station so as to communicate with the internet. In one example, the transmission device 106 may be a Radio Frequency (RF) module, which is used for communicating with the internet in a wireless manner.
In this embodiment, a method for determining an occupied bandwidth and a modulation factor of a modulation signal operating in the mobile terminal or the network architecture is provided, and fig. 2 is a flowchart of a method for determining an occupied bandwidth and a modulation factor of a modulation signal according to an embodiment of the present invention, as shown in fig. 2, the flowchart includes the following steps:
step S202, sending a measurement instruction to a tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction;
specifically, a communication interface can be used to send a measurement instruction to the device to be tested, and a modulation signal is received through the communication interface, wherein the communication interface can adopt RS232 serial port communication, and the frame format of the data communication protocol is "frame header + command + data + check + frame tail".
Further, the received modulation signal is mixed with a local oscillation signal of the radio frequency chip, and then the intermediate frequency signal is output after low-pass filtering processing.
Step S204, mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal;
the method comprises the steps of carrying out initialization configuration on a radio frequency chip, firstly setting the frequency of a local oscillator of the radio frequency chip to be fc, and assuming that the frequency of a received carrier signal is fx, outputting an intermediate frequency signal fi through a low-pass filter after the received carrier signal and the local oscillator of the radio frequency chip are mixed, wherein the fi must meet the requirement of being capable of modulating a baseband signal of 256KHz or 512 KHz. The radio frequency unit is initialized, the local oscillator of the radio frequency chip is configured by sending an instruction through the upper computer, the frequency of the mixed intermediate frequency signal is 4MHz, the modulated signal with 512KHz or 256Khz can be satisfied, and the modulated signal and the baseband signal are random waves or square waves.
Step S206, decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
step S208, determining an occupied bandwidth and a modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
The intermediate frequency signal fi is subjected to quadrature down-conversion in the radio frequency chip to obtain two paths of intermediate frequency signals I, Q, and then AD sampling is performed to form digital signals which can be processed by the FPGA. According to the regulation of the frequency shift of the modulation signal, the occupied bandwidth and the modulation coefficient of the modulation signal are calculated by estimating the occupied bandwidth and the modulation coefficient of the intermediate frequency signal.
Through the steps S202 to S208, the problems that in the related art, the occupied bandwidth and the modulation coefficient of the tested equipment are measured through the frequency spectrograph, the testing speed is low, more frequency spectrometers are needed in batch production, and the cost is high can be solved.
In an embodiment of the present invention, the step S208 may specifically include:
s2081, respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and determining the occupied bandwidth of the modulation signal through fast Fourier transform;
specifically, S2081 specifically includes:
respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and extracting a predetermined number of points;
performing fast Fourier transform on the predetermined number of points to generate a spectrum of signal amplitude and frequency components, and converting the spectrum into a power spectrum of the intermediate-frequency signal;
and determining the occupied bandwidth of the modulation signal by estimating the sum of the powers of the intermediate frequency signal in the infinite frequency domain through the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths. Further, the occupied bandwidth of the modulation signal is determined in such a way that the ratio of the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths and the sum of the powers in the infinite frequency domain is equal to a predetermined percentage according to the following formula:
IQ of the intermediate frequency signal is used as a real part and an imaginary part of the intermediate frequency signal, limited points are extracted, fast Fourier transform (fft) is carried out on the IQ, a power spectrum of the intermediate frequency signal is solved, a power spectrum of an infinite frequency domain is estimated according to the power spectrum of wired points, integral calculation is carried out according to a formula, and 2w is the estimated occupied bandwidth. The modulation information transmitted by the CPC card or the OBU is a random number, I, Q signals are output through the radio frequency module, I, Q signals carry the modulation information of the random number, then the FPGA receives I, Q signals after AD conversion, points such as 2048 are extracted from I, Q signals, fast Fourier transform (fft) is carried out, and the signals obtained after the conversion are the amplitude values of frequency components corresponding to the current intermediate frequency signals, namely the amplitude spectrum corresponding to the current intermediate frequency signals. The sampling frequency f of fftsampleThe ratio of the number of the extracted points n is the resolution of the amplitude spectrum. The relationship between the square of the amplitude and the frequency is the power spectrum.
The fourier transform takes 2048-point transform, the sampling clock is 20Mhz, and the signal is in the form of SIG ═ I + Qj. The Fourier transform adopts a streamline design mode to only transform points extracted in fixed time, the transformation cannot be carried out in real time, and the phase of a real part I and an imaginary part Q of a signal is fixed in a lead-lag relationship.
According to the symmetric characteristic of fft, after Fourier transform of fixed extraction points, the power spectrogram is a frequency point
Power spectrum of (a). For signals of a single frequency point, power is mainly concentrated near a central frequency, and power of infinite frequency components is close to that of noise and can be ignored. Thus, it isSaid occupied bandwidth is adopted
The power spectrum of the bandwidth is approximately equal to the power spectrum of the estimated infinite bandwidth.
Setting the local oscillator of the radio frequency chip to mix with the input measuring signal to theoretically generate an intermediate frequency signal with 4Mhz frequency width and recording the intermediate frequency signal as fI4MhzActually, due to the characteristics of the radio frequency chip, frequency offset occurs to generate an intermediate frequency signal floating around 4Mhz, so that the intermediate frequency signal needs to be generated at the frequency chip
Within the bandwidth, the central frequency point corresponding to the maximum power value is obtained, i.e. the central frequency of the actual intermediate frequency signal, and is recorded as fImax. The integral interval of the estimated occupied bandwidth is [0, 2 fImax]At the center frequency fImaxAnd integrating the two symmetrical intervals as a starting point until the power ratio reaches B, wherein B is more than 0.5 and less than 1.
S2082, determining the modulation coefficient of the modulation signal according to the intermediate frequency signal I or the intermediate frequency signal Q.
Further, step S2082 specifically includes: extracting intermediate frequency signals in one or more modulation periods in the intermediate frequency signal I or the intermediate frequency signal Q; determining an envelope of the intermediate frequency signal within the one or more modulation periods; obtaining one or more maxima A in the envelopemaxAnd one or more minimum values Amin(ii) a According to the maximum value one or more AmaxAnd the one or more minimum values AminDetermining a modulation coefficient of the modulation signal.
In particular, according to said maximum AmaxAnd said one minimum value AminDetermining a modulation coefficient M of the modulation signal:
testing modulation coefficient, needing to test low and high modulation coefficient, CPC card or OBU transmitting modulation signal whose modulation information is square wave, mixing frequencyThen, the output if signal I, Q carries the modulation information of the square wave, and the relationship of the signal amplitude value is not changed after mixing. In a modulation period, the envelope of the modulation period is calculated by comparing the maximum value points of the carrier wave of the modulation signal, then the maximum value and the minimum value are taken, and the modulation coefficient of the modulation signal can be calculated by the formula. Or
The maximum value and the minimum value of the envelope are easily influenced by interference signals, so that a plurality of periods are used, the amplitude is calculated to obtain an average value, finally, the modulation coefficient is calculated, and the maximum value A and the minimum value A are obtained according to the maximum value AmaxAnd the plurality of minimum values AminDetermining a modulation coefficient M of the modulation signal:
wherein N is the maximum value AmaxOr minimum value AminThe number of the cells.
According to the orthogonal relation of intermediate frequency signals I, Q, any I or Q signal can reflect the amplitude of the whole intermediate frequency signal, therefore, one path of I (Q) signal is selected, the intermediate frequency signal of one modulation period is selected, the envelope of the intermediate frequency signal of one modulation period is firstly obtained by taking the maximum value in the period of one carrier signal, and then the maximum value A of the envelope is takenmaxAnd a minimum value AminThe modulation factor can be calculated according to a formula. And after the occupied bandwidth and the modulation coefficient are calculated, the occupied bandwidth and the modulation coefficient are uploaded to a computer through a communication interface module to be displayed or stored in a database.
In the process of production, the volume of CPC card or OBU is very big, and required frequency spectrograph is also very many, and the frequency spectrograph is expensive, uses loaded down with trivial details, causes the great increase of the cost of production, and is unfavorable for line workman's operation. The device with low price, convenient use and light volume is designed and used for replacing a frequency spectrograph, and the test of the occupied bandwidth and the modulation factor is completed within the required precision range. The whole system mainly comprises a radio frequency receiver, an ADC, an FPGA, an upper computer and the like, wherein the FPGA is mainly used for processing and calculating signal data at a radio frequency front end and has a communication function with the upper computer; the upper computer is mainly used for using, debugging and displaying the device by a user. Fig. 3 is a flowchart of occupied bandwidth determination according to an embodiment of the present invention, as shown in fig. 3, including:
step 301, setting a frequency FC of the local oscillator signal, and mixing the local oscillator signal with the modulation signal to obtain an intermediate frequency signal, where the frequency of the intermediate frequency signal may be 4Mhz, so that the CPC card or the OBU transmits a random carrier signal, that is, a random binary number, to be modulated on a carrier to obtain a modulation signal.
Step 302, subjecting the mixed intermediate frequency signal to quadrature down-conversion decomposition inside the rf chip, outputting I, Q signals, and adjusting I, Q phase relationship of the signals, so that I leads Q phase by 90 degrees, and then obtaining a set of information signals, which are expressed by complex numbers, i.e. real part and imaginary part of the intermediate frequency signal. The lead-lag relationship of the I, Q signal is fixed as the real and imaginary parts of the fourier transform.
Step 303, setting a counter, continuously extracting the real part and the imaginary part of the signal, setting the paper extraction number to reach a preset number, setting the start and end signals of the fourier transform, wherein the preset number can be 2048, extracting 2048 points from the signal, and designing the start and end of the fourier transform.
And step 304, performing fast Fourier transform on the extracted predetermined number of points.
Thus according to an approximation formula
The central frequency point is taken as a starting point, point-by-point integration is carried out in the left and right intervals until the integration and the integral of the whole interval meet the relation of B (B is more than 0.5 and less than 1). The occupied bandwidth is W-p 1-p 2.
Fig. 4 is a flowchart of modulation factor determination according to an embodiment of the present invention, as shown in fig. 4, including:
step 401, setting a frequency FC of a local oscillator signal, and mixing the local oscillator signal with a modulation signal to obtain an intermediate frequency signal, where the frequency of the intermediate frequency signal may be 4 Mhz;
step 402, enabling the CPC card or the OBU to send a modulation signal with a square wave as a baseband signal, after receiving the modulation signal, performing frequency mixing, and acquiring by the FPGA, the signal is a sinusoidal signal with square wave envelope. And taking an extreme point for the sinusoidal signal, and converting the signal into an envelope form of square waves.
Step 403, in one period of the square wave, taking the maximum value and the minimum value of the envelope, namely the modulated amplitude value of the signal, continuously taking a plurality of periods to calculate an average value, and finally calculating the modulation coefficient of the modulation signal.
For example, to reduce interference, 189 cycles are continuously averaged, and the average is calculated according to the formula
The modulation factor can be obtained. A plurality of square wave periods are taken, the time for solving the modulation coefficient is increased, and the error is reduced.
According to the embodiment of the invention, RS232 serial port communication is adopted, a user sends a measurement instruction, and the device quickly returns measurement information. And converting the high-frequency signal into a low-frequency signal, converting the continuous analog signal into a discrete digital signal, and measuring the occupied bandwidth and the modulation coefficient in the FPGA. The FPGA can accelerate the processing speed of digital signals and has higher operation precision. When the occupied bandwidth is measured, a formula is designed and modified, and the whole power spectrum is estimated by utilizing the approximation of local power spectrum classes, so that the purpose of calculating the occupied bandwidth is achieved. The modulation factor is calculated by mainly using the principle that the modulation factor of a signal is unchanged before and after frequency mixing. The modulation coefficient of the modulation signal can be approximately estimated only by requiring the modulation coefficient of the intermediate frequency signal.
Example 2
According to another embodiment of the present invention, there is also provided an apparatus for determining an occupied bandwidth and a modulation factor of a modulation signal, and fig. 5 is a block diagram of the apparatus for determining an occupied bandwidth and a modulation factor of a modulation signal according to an embodiment of the present invention, as shown in fig. 5, including:
the sending module 52 is configured to send a measurement instruction to the device under test, and receive a modulation signal returned by the device under test according to the measurement instruction;
the frequency mixing module 54 is configured to mix the modulation signal with a local oscillation signal of the radio frequency chip to obtain an intermediate frequency signal;
the decomposition module 56 is configured to decompose the intermediate frequency signal through quadrature down-conversion in the radio frequency chip to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and perform analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
a determining module 58, configured to determine an occupied bandwidth and a modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
Optionally, the determining module 58 includes:
the first determining submodule is used for respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal and determining the occupied bandwidth of the modulation signal through fast Fourier transform;
and the second determining submodule is used for determining the modulation coefficient of the modulation signal through the intermediate frequency signal I or the intermediate frequency signal Q.
Optionally, the first determining sub-module includes:
an extraction unit, configured to take the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, respectively, and extract a predetermined number of points;
the generating unit is used for carrying out fast Fourier transform on the predetermined number of points to generate a spectrum of signal amplitude and frequency components, and converting the spectrum into a power spectrum of the intermediate frequency signal;
the first determining unit is used for determining the occupied bandwidth of the modulation signal in a mode of estimating the sum of the powers of the intermediate frequency signal in an infinite frequency domain through the sum of the powers of the power maps of the intermediate frequency signal between the occupied bandwidths.
Optionally, the first determining unit is further configured to
Determining the occupied bandwidth of the modulation signal by the way that the ratio of the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths and the sum of the powers in the infinite frequency domain is equal to a predetermined percentage according to the following formula:
Optionally, the second determining sub-module includes:
an extracting unit, configured to extract an intermediate frequency signal in one or more modulation periods in the intermediate frequency signal I or the intermediate frequency signal Q;
a second determining unit for determining an envelope of the intermediate frequency signal within the one or more modulation periods;
an acquisition unit for acquiring one or more maxima A in the envelopemaxAnd one or more minimum values Amin；
A third determination unit for determining one or more A's according to the maximum valuemaxAnd the one or more minimum values AminDetermining a modulation coefficient of the modulation signal.
Optionally, the third determining unit is further configured to
According to said one maximum value AmaxAnd said one minimum value AminDetermining a modulation coefficient M of the modulation signal:
or
According to the plurality of maximum values AmaxAnd the plurality of minimum values AminDetermining a modulation coefficient M of the modulation signal:
wherein N is the maximum value AmaxOr minimum value AminThe number of the cells.
Optionally, the mixing module 54 is further configured to
And after mixing the received modulation signal with a local oscillation signal of a radio frequency chip, performing low-pass filtering processing, and outputting the intermediate frequency signal.
It should be noted that, the above modules may be implemented by software or hardware, and for the latter, the following may be implemented, but not limited to: the modules are all positioned in the same processor; alternatively, the modules are respectively located in different processors in any combination.
Example 3
Embodiments of the present invention also provide a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to perform the steps of any of the above method embodiments when executed.
Alternatively, in the present embodiment, the storage medium may be configured to store a computer program for executing the steps of:
s1, sending a measurement instruction to the tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction;
s2, mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal;
s3, decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and S4, determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
Optionally, in this embodiment, the storage medium may include, but is not limited to: various media capable of storing computer programs, such as a usb disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic disk, or an optical disk.
Example 4
Embodiments of the present invention also provide an electronic device comprising a memory having a computer program stored therein and a processor arranged to run the computer program to perform the steps of any of the above method embodiments.
Optionally, the electronic apparatus may further include a transmission device and an input/output device, wherein the transmission device is connected to the processor, and the input/output device is connected to the processor.
Optionally, in this embodiment, the processor may be configured to execute the following steps by a computer program:
s1, sending a measurement instruction to the tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction;
s2, mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal;
s3, decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and S4, determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments and optional implementation manners, and this embodiment is not described herein again.
It will be apparent to those skilled in the art that the modules or steps of the present invention described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described may be performed in an order different than that described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, the present invention is not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for determining an occupied bandwidth and a modulation factor of a modulated signal, comprising:
sending a measurement instruction to a tested device, and receiving a modulation signal returned by the tested device according to the measurement instruction;
mixing the modulation signal with a local oscillation signal of a radio frequency chip to obtain an intermediate frequency signal;
decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
2. The method of claim 1, wherein determining the occupied bandwidth and modulation factor of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion comprises:
respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and determining the occupied bandwidth of the modulation signal through fast Fourier transform;
and determining the modulation coefficient of the modulation signal through the intermediate frequency signal I or the intermediate frequency signal Q.
3. The method of claim 2, wherein determining the occupied bandwidth of the modulated signal by fast fourier transform using the if signal I and the if signal Q as real and imaginary parts of the if signal, respectively, comprises:
respectively taking the intermediate frequency signal I and the intermediate frequency signal Q as a real part and an imaginary part of the intermediate frequency signal, and extracting a predetermined number of points;
performing fast Fourier transform on the predetermined number of points to generate a spectrum of signal amplitude and frequency components, and converting the spectrum into a power spectrum of the intermediate-frequency signal;
and determining the occupied bandwidth of the modulation signal by estimating the sum of the powers of the intermediate frequency signal in the infinite frequency domain through the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths.
4. The method of claim 3, wherein determining the occupied bandwidth of the modulated signal by estimating the sum of the powers of the intermediate frequency signal in the infinite frequency domain from the sum of the powers of the power maps of the intermediate frequency signal between the occupied bandwidths comprises:
determining the occupied bandwidth of the modulation signal by the way that the ratio of the sum of the powers of the power map of the intermediate frequency signal between the occupied bandwidths and the sum of the powers in the infinite frequency domain is equal to a predetermined percentage according to the following formula:
5. The method of claim 2, wherein determining the modulation factor of the modulation signal from the intermediate frequency signal I or the intermediate frequency signal Q comprises:
extracting intermediate frequency signals in one or more modulation periods in the intermediate frequency signal I or the intermediate frequency signal Q;
determining an envelope of the intermediate frequency signal within the one or more modulation periods;
obtaining one or more maxima A in the envelopemaxAnd one or more minimum values Amin；
According to the maximum value one or more AmaxAnd the one or more minimum values AminDetermining a modulation coefficient of the modulation signal.
6. Method according to claim 5, characterized in that it consists in determining said one or more maximum values AmaxAnd the one or more minimum values AminDetermining the modulation factor of the modulation signal comprises:
according to said one maximum value AmaxAnd said one minimum value AminDetermining a modulation coefficient M of the modulation signal:
or
According to the plurality of maximum values AmaxAnd the plurality of minimum values AminDetermining a modulation coefficient M of the modulation signal:
wherein N is the maximum value AmaxOr minimum value AminThe number of the cells.
7. The method according to any one of claims 1 to 6, wherein mixing the received modulation signal with a local oscillator signal of a radio frequency chip to obtain an intermediate frequency signal comprises:
and after mixing the received modulation signal with a local oscillation signal of a radio frequency chip, performing low-pass filtering processing, and outputting the intermediate frequency signal.
8. An apparatus for determining occupied bandwidth and modulation factor of a modulated signal, comprising:
the sending module is used for sending a measuring instruction to the tested equipment and receiving a modulation signal returned by the tested equipment according to the measuring instruction;
the frequency mixing module is used for mixing the modulation signal with a local oscillation signal of the radio frequency chip to obtain an intermediate frequency signal;
the decomposition module is used for decomposing the intermediate frequency signal in the radio frequency chip through orthogonal down-conversion to obtain an intermediate frequency signal I and an intermediate frequency signal Q, and performing analog-to-digital conversion on the intermediate frequency signal I and the intermediate frequency signal Q;
and the determining module is used for determining the occupied bandwidth and the modulation coefficient of the modulation signal according to the intermediate frequency signal I and the intermediate frequency signal Q after analog-to-digital conversion.
9. A computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to carry out the method of any one of claims 1 to 7 when executed.
10. An electronic device comprising a memory and a processor, wherein the memory has stored therein a computer program, and wherein the processor is arranged to execute the computer program to perform the method of any of claims 1 to 7.
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