CN101997789A - Vector signal generating method and generator - Google Patents

Abstract

The invention discloses a generation method and generator of a vector signal, which is realized through virtual design of LabVIEW language. Firstly, a baseband digital signal generator is established to generate and output baseband signals of I channel data and Q channel data; secondly, a pulse is established Shaping filter and I/Q modulator are used to filter and modulate the baseband signal; finally, a D/A converter is established to convert the digital modulated signal into an analog signal and output it. The invention can generate vector signals based on different modulation methods, change signal spectrum, simulate channel noise, transmit analog signals, etc. according to user needs.

Description

A method and generator for vector signal generation

technical field

The invention relates to the field of digital communication measurement, in particular to a vector signal generation method and generator.

Background technique

A communication system, see Figure 1, usually consists of three elements: transmitter, channel and receiver.

The function of the transmitter is to inject the signal generated by the information source into the carrier, and then modulate it into a signal suitable for transmission in the channel by changing the amplitude, frequency or phase of the carrier. The modulation process can move the spectrum of the source signal to any position, which is beneficial to the transmission of the signal, and the spectrum resources can be fully utilized by means of multiplexing. The channel is the medium of signal transmission, and the signal will be attenuated to different degrees during the transmission process, and its main source is additive noise. Therefore, the receiver needs to use the corresponding demodulation algorithm to extract the original signal information from the carrier. The accuracy of actual demodulation depends on the selection of demodulation algorithm, signal-to-noise ratio and other factors.

As for the signal generator, especially the vector signal generator, the design of the virtual instrument can be carried out through the LabVIEW language, so as to realize the function of the vector signal generator.

LabVIEW is an innovative graphical programming environment developed by National Instruments Corporation of the United States. Compared with text-based programming languages, it proposes a block-based system design method. Each LabVIEW program can be designed as a virtual instrument (VI), and at the same time, a VI can also have multiple subVIs.

The core idea of LabVIEW is structured data flow. Every VI operation must follow the data flow specification, that is, a node can only run when all inputs are available, and the result after the operation is completed is used as input and output to the next node. .

Contents of the invention

The purpose of the present invention is to provide a vector signal generation method and generator, which can generate vector signals for use in related tests.

On the one hand, the present invention provides a kind of generation method of vector signal, and it realizes by LabVIEW language, comprises the following steps:

1.1. Establish a baseband digital signal generator to generate random binary sequences, map the binary sequences into baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data in IQ modulation and output;

1.2, set up the pulse shaping filter, make it limit the signal bandwidth of the baseband symbol of the I passway of step 1.1 output and the Q passway and output the filtered signal by the RC filter satisfying the Nyquist condition;

1.3. Establish an I/Q modulator so that it modulates the filtered I channel data and Q channel data through a matched carrier, and modulates the modulated signal and the signal of the I/Q channel through product modulation and outputs it;

1.4. Establish a D/A converter to convert the digital modulation signal output in step 1.3 into an analog signal and output it.

The working steps of the baseband digital signal generator in the described step 1.1 include:

1.1.1. Generate a binary sequence;

1.1.2. Map the binary sequence to baseband symbols through the constellation diagram;

1.1.3. Multiply the amplitude of the baseband symbol by an energy control constant;

1.1.4. Separate the energy-controlled baseband symbols into I channel data and Q channel data in IQ modulation and output them.

The working steps of the pulse shaping filter in the step 1.2 include:

1.2.1, obtain the baseband symbol stream, and set up a raised cosine filter and a shift register at the same time;

1.2.2, performing shaping filtering on the baseband symbols through the root cosine filter at the transmitting end;

1.2.3. Perform matched filtering on the baseband symbols through the shift register at the receiving end.

The working steps of the I/Q modulator in the step 1.3 include:

1.3.1, the filtered I channel data is modulated by a cos(2πf _c t) carrier;

1.3.2. Modulate the filtered Q channel data through a sin(2πf _c t) carrier;

1.3.3. The data modulated by the above two steps and the signal of the I/Q channel are multiplied and output.

The method also includes the step of providing a user interface for a user to set related parameters.

On the other hand, the present invention also provides a kind of vector signal generator, it realizes by LabVIEW language, comprises:

The baseband digital signal generator is used to generate random binary sequences, map the binary sequences into baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data output in IQ modulation;

A pulse shaping filter, connected to the output of the baseband digital signal generator, used to limit the signal bandwidth of the baseband symbols of the I channel and the Q channel and output the filtered signal through an RC filter satisfying the Nyquist condition ;

The I/Q modulator is connected to the output end of the pulse shaping filter, in order to modulate the filtered I channel data and Q channel data through a matched carrier, and combine the modulated signal with the I/Q channel The signal is modulated by product and output;

The D/A converter is connected to the output terminal of the I/Q modulator, and is used to convert the digital modulation signal output by the I/Q modulator into an analog signal and output it.

The baseband digital signal generator also includes:

A module that generates binary sequences;

A module that maps a binary sequence to a baseband symbol through a constellation diagram;

A module that multiplies the amplitude of the baseband symbols by an energy control constant;

A module that separates the energy-controlled baseband symbols into I-channel data and Q-channel data in IQ modulation and outputs them.

The pulse shaping filter also includes:

Obtain the baseband symbol stream and build a raised cosine filter and a shift register module;

A module for shaping and filtering baseband symbols through the root cosine filter at the sending end;

A module for performing matched filtering on baseband symbols through the shift register at the receiving end.

The I/Q modulator also includes:

A module that modulates the filtered I channel data through a cos(2πf _c t) carrier;

A module that modulates the filtered Q channel data through a sin(2πf _c t) carrier;

A module that modulates the data modulated by the above two modules and the signal of the I/Q channel through product modulation and outputs it.

The generator also includes a user interface module for the user to set the modulation method, the number of symbols per slot, the sampling frequency, and the carrier frequency.

Adopt the generating method and generator of a kind of vector signal of the present invention, it carries out virtual design by LabVIEW language and realize, at first set up baseband digital signal generator, produce the baseband signal of I channel data and Q channel data and output; Secondly Build the pulse shaping filter and I/Q modulator to filter and modulate the baseband signal; finally build the D/A converter to convert the digital modulation signal into an analog signal and output it. The invention can generate vector signals based on different modulation methods, change signal spectrum, simulate channel noise, transmit analog signals, etc. according to user needs.

Description of drawings

FIG. 1 is a schematic diagram of constituent elements of a current communication system;

Fig. 2 is the flowchart of described method;

Fig. 3 is the functional block diagram of described generator;

Fig. 4 is the working flowchart of described baseband digital signal generator;

Fig. 5 is the workflow diagram of described pulse shaping filter;

Fig. 6 is a working flowchart of the I/Q modulator.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

With reference to Fig. 2, the present invention provides a kind of generation method 100 of vector signal, and it is realized by LabVIEW language, comprises steps 101,102,103,104, can set up vector signal generator 200 among Fig. 3 by described method 100, following Face these steps for an introduction:

101. Establish a baseband digital signal generator to generate baseband symbols and separate them into I channel data and Q channel data for output.

Establish a baseband digital signal generator to generate random binary sequences, map the binary sequences to baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data in IQ modulation and output them .

Modern communication systems require greater information throughput, higher signal quality, better security and digital signal compatibility. The advantage of digital signals is that designers can do any processing on digital signals: they can send signals at any time; they can be mixed with other information; they can use various digital modulation mechanisms to reduce the amount of transmitted data and improve efficiency. Among many digital modulation algorithms, IQ quadrature modulation is a modulation mechanism that improves the effective transmission rate and resists signal interference without increasing the bandwidth.

A_n和θ_n的值如表2-1所示：The digital signal generator generates random binary data, maps the binary bits to symbols and separates the symbols into in-phase and quadrature components in IQ modulation. The mapping method varies according to different modulation methods, and the most intuitive method is through the signal constellation diagram (constellation diagram). The constellation diagram shows all possible symbol values for different modulation methods on the two-dimensional complex plane. In order to minimize burst errors during transmission, all symbol mapping here adopts Gray code (Gray Code). The symbols after baseband modulation can be expressed in the complex plane as

The values of A _n and θ _n are shown in Table 2-1:

Table 2-1 Modulation symbol table

modulation method S _l S _Q BPSK A _n cos θ _n , θ _n =0, π; A _n =1 None

In the actual implementation process, considering the energy control of the modulated symbol, the amplitude of the output symbol needs to be multiplied by a control constant D. This constant can be derived from the constellation diagrams of different modulation algorithms. For PSK, the relationship between the average symbol energy E _s and Δ is derived:

E _s ＝|Δ·e ^-fθ | ² ＝Δ(D is the symbol amplitude of the complex plane, q is the phase of the symbol)

For QAM, the situation is more complicated. The relationship between the average symbol energy E _s and Δ is derived:

(M is the QAM series, D is half of the distance between two adjacent characters (horizontal and vertical directions), E _k is the energy of the kth symbol)

Referring to Fig. 4, the working steps of the baseband digital signal generator in the step 101 include:

generate a binary sequence;

Map the binary sequence to baseband symbols through the constellation diagram;

multiplying the amplitude of the baseband symbols by an energy control constant;

The energy-controlled baseband symbols are separated into I channel data and Q channel data in IQ modulation and output.

102. Establish a pulse shaping filter to limit the bandwidth of the baseband symbol signal and perform filtering through the filter.

A pulse shaping filter is established to limit the signal bandwidth of the baseband symbols of the I channel and Q channel output in step 101 and output the filtered signal through an RC filter satisfying the Nyquist condition.

A pulse-shaping filter is applied to the baseband modulation symbols to limit the bandwidth of the signal. In addition, it avoids inter-symbol interference (ISI) by satisfying the Nyquist criterion. A pulse-shaping filter that satisfies the Nyquist criterion is also called a Nyquist filter.

The RC filter has a zero-crossing point in each symbol period in the time domain, which satisfies the Nyquist condition; in the frequency domain, the low-frequency band is unity gain, the mid-band raised cosine spectrum, and the high-band zero gain can effectively control the bandwidth of the signal. In order to maximize the signal-to-noise ratio at the sampling moment, two root-raised cosine (RRC) filters are usually used in practical applications: one is used as a shaping filter at the sending end, and the other is used as a matching filter at the receiving end. The total effect of the two is equivalent to A single RC filter, in this way, can not only make the signal-to-noise ratio reach the highest when sampling, but also can not introduce intersymbol interference in a certain band-limited flat channel.

The impulse response of the RRC filter is defined as follows:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; rrc</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\frac{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&pi;t</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; ]</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&alpha;t</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 16</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="t"\; filenames="H2009100567209E0000022.png"\; state="\{\{state\}\}">t</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}$

With the help of the shift register of LabVIEW, the transmitting end applies P _rrc (t) to the modulated baseband signal in each symbol period, which is equivalent to applying a root raised cosine filter in the frequency domain.

Referring to Fig. 5, the working steps of the pulse shaping filter in the step 102 include:

Obtain the baseband symbol stream, and simultaneously establish a raised cosine filter and a shift register;

performing shaping filtering on the baseband symbols through the root cosine filter at the sending end;

At the receiving end, the baseband symbols are matched and filtered through the shift register.

103. Establish an I/Q modulator to modulate and output the filtered baseband signal.

An I/Q modulator is established to modulate the filtered I-channel data and Q-channel data through a matched carrier, and modulate the modulated signal and the signal of the I/Q channel through product modulation and output.

I/Q modulation has two purposes: one is to integrate separate in-phase and quadrature data streams to improve spectrum utilization; the other is to increase the frequency of the baseband signal to a range suitable for long-distance transmission. The baseband signals of the two channels are modulated by two orthogonal carriers, namely cos(2πf _c t) and sin(2πf _c t), and the sum of the product modulation and the I/Q channel signals is the final output signal.

Referring to Fig. 6, the working steps of the I/Q modulator in the step 103 include:

The filtered I channel data is modulated by a cos(2πf _c t) carrier;

The filtered Q channel data is modulated by a sin(2πf _c t) carrier;

The data modulated by the above two steps and the signal of the I/Q channel are product-modulated and output.

104. Establish a D/A converter to convert the digital modulation signal output in step 103 into an analog signal and output it.

The D/A converter is designed to realize D/A conversion, which converts the I/Q modulation signal generated by the software into a physical signal and transmits it through the analog channel. The transmission of physical signals requires precise timing control and synchronization of sending and receiving. Two function generators are used here: one as an external clock source and the other as a start trigger for two signal acquisition cards. The parameters of the DAQ board are shown in Table 2.2 below:

Table 2.2

As an embodiment, the method 100 of the present invention further includes the step of providing a user interface for the user to set related parameters, and the user sets the modulation method, number of symbols per slot, sampling frequency, carrier frequency, etc. through the interface.

Referring to Fig. 3, the present invention also provides a kind of vector signal generator 200, and it realizes by LabVIEW language, comprises:

The baseband digital signal generator 201 is used to generate random binary sequences, map the binary sequences into baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data output in IQ modulation;

A pulse shaping filter 202, connected to the output terminal of the baseband digital signal generator 201, is used to limit the signal bandwidth of the baseband symbols of the I channel and the Q channel and pass through an RC filter satisfying the Nyquist condition to output and filter signal of;

The I/Q modulator 203 is connected to the output end of the pulse shaping filter 202 to modulate the filtered I channel data and Q channel data through a matched carrier, and combine the modulated signal with the I/Q The signal of the channel is modulated by the product and output;

The D/A converter 204 is connected to the output terminal of the I/Q modulator 203, and is used for converting the digital modulation signal output by the I/Q modulator 203 into an analog signal and outputting it.

As an embodiment, the baseband digital signal generator 201 also includes:

A module that generates binary sequences;

A module that maps a binary sequence to a baseband symbol through a constellation diagram;

A module that multiplies the amplitude of the baseband symbols by an energy control constant;

A module that separates the energy-controlled baseband symbols into I-channel data and Q-channel data in IQ modulation and outputs them.

As an embodiment, the pulse shaping filter 202 further includes:

Obtain the baseband symbol stream and build a raised cosine filter and a shift register module;

A module for shaping and filtering baseband symbols through the root cosine filter at the sending end;

A module for performing matched filtering on baseband symbols through the shift register at the receiving end.

As an embodiment, the I/Q modulator 203 further includes:

A module that modulates the filtered I channel data through a cos(2πf _c t) carrier;

A module that modulates the filtered Q channel data through a sin(2πf _c t) carrier;

A module that modulates the data modulated by the above two modules and the signal of the I/Q channel through product modulation and outputs it.

In addition, the generator further includes a user interface module, which is used for the user to set the modulation method, the number of symbols per slot, the sampling frequency, and the carrier frequency.

It should be pointed out that a vector signal generator 200 of the present invention and a vector signal generation method 100 of the present invention are the same or similar in principle and embodiment, so the repeated parts are not Let me repeat.

Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention, as long as within the spirit of the present invention, changes to the above embodiments, Modifications are intended to fall within the scope of the claims of the present invention.

Claims (10)

1. a generation method of vector signal, it is realized by LabVIEW language, is characterized in that, may further comprise the steps: 1.1. Establish a baseband digital signal generator to generate random binary sequences, map the binary sequences into baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data in IQ modulation and output; 1.2, set up the pulse shaping filter, make it limit the signal bandwidth of the baseband symbol of the I passway of step 1.1 output and the Q passway and output the filtered signal by the RC filter satisfying the Nyquist condition; 1.3. Establish an I/Q modulator so that it modulates the filtered I channel data and Q channel data through a matched carrier, and modulates the modulated signal and the signal of the I/Q channel through product modulation and outputs it; 1.4. Establish a D/A converter to convert the digital modulation signal output in step 1.3 into an analog signal and output it. 2. The method according to claim 1, characterized in that, the working steps of the baseband digital signal generator in the step 1.1 include: 1.1.1. Generate a binary sequence; 1.1.2. Map the binary sequence to baseband symbols through the constellation diagram; 1.1.3. Multiply the amplitude of the baseband symbol by an energy control constant; 1.1.4. Separate the energy-controlled baseband symbols into I channel data and Q channel data in IQ modulation and output them. 3. The method according to claim 2, characterized in that, the working steps of the pulse shaping filter in said step 1.2 include: 1.2.1, obtain the baseband symbol stream, and set up a raised cosine filter and a shift register at the same time; 1.2.2, performing shaping filtering on the baseband symbols through the root cosine filter at the transmitting end; 1.2.3. Perform matched filtering on the baseband symbols through the shift register at the receiving end. 4. the method for claim 3 is characterized in that, the working step of the I/Q modulator in the described step 1.3 comprises: 1.3.1, the filtered I channel data is modulated by a cos(2πf _c t) carrier; 1.3.2. Modulate the filtered Q channel data through a sin(2πf _c t) carrier; 1.3.3. The data modulated by the above two steps and the signal of the I/Q channel are multiplied and output. 5. The method according to claim 4, further comprising the step of providing a user interface for users to set related parameters. 6. A vector signal generator, which is realized by LabVIEW language, is characterized in that, comprising: The baseband digital signal generator is used to generate random binary sequences, map the binary sequences into baseband symbols, perform energy control on the formed baseband symbols, and finally separate the baseband symbols into I channel data and Q channel data output in IQ modulation; A pulse shaping filter, connected to the output of the baseband digital signal generator, used to limit the signal bandwidth of the baseband symbols of the I channel and the Q channel and output the filtered signal through an RC filter satisfying the Nyquist condition ; The I/Q modulator is connected to the output end of the pulse shaping filter, in order to modulate the filtered I channel data and Q channel data through a matched carrier, and combine the modulated signal with the I/Q channel The signal is modulated by product and output; The D/A converter is connected to the output terminal of the I/Q modulator, and is used to convert the digital modulation signal output by the I/Q modulator into an analog signal and output it. 7. generator as claimed in claim 6, is characterized in that, described baseband digital signal generator also comprises: A module that generates binary sequences; A module that maps a binary sequence to a baseband symbol through a constellation diagram; A module that multiplies the amplitude of the baseband symbols by an energy control constant; A module that separates the energy-controlled baseband symbols into I-channel data and Q-channel data in IQ modulation and outputs them. 8. The generator of claim 7, wherein the pulse shaping filter further comprises: Obtain the baseband symbol stream and build a raised cosine filter and a shift register module; A module for shaping and filtering baseband symbols through the root cosine filter at the sending end; A module for performing matched filtering on baseband symbols through the shift register at the receiving end. 9. The generator of claim 8, wherein the I/Q modulator further comprises: A module that modulates the filtered I channel data through a cos(2πf _c t) carrier; A module that modulates the filtered Q channel data through a sin(2πf _c t) carrier; A module that modulates the data modulated by the above two modules and the signal of the I/Q channel through product modulation and outputs it. 10. The generator according to claim 9, characterized in that, the generator further comprises a user interface module for the user to set the modulation method, the number of symbols per slot, the sampling frequency, and the carrier frequency.

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