CN108494438A - A kind of generation method, generating means and the sending device of hybrid spread spectrum signal - Google Patents

Abstract

The invention provides a method, a generating device and a sending device for a hybrid spread spectrum signal. The generating device includes: a direct spread module, used to perform direct sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and perform polarity conversion on the first spread spectrum signal; a frequency hopping module, used to generate multiple Road frequency hopping carrier; hybrid spread spectrum signal generating module, electrically connected with the direct spread module and the frequency hopping module respectively, for according to the first spread spectrum signal through polarity conversion and the multiple frequency hopping carriers, Generate mixed spread spectrum signals. The generation device provided by the present invention multiplies the polarity-converted first spread-spectrum signal by multiple frequency-hopping carriers respectively, and combines all the multiplied results to generate a high-speed mixed spread-spectrum signal. Based on the advantages of strong concealment of direct spread communication system and strong anti-interference performance of frequency hopping system, the data rate is improved.

Description

A generating method, generating device and sending device of a hybrid spread spectrum signal

technical field

The present invention relates to the technical field of signal processing, and more specifically, to a generation method, generation device and transmission device of a mixed spread spectrum signal.

Background technique

In modern communications, especially in modern military communications, anti-detection, anti-jamming, anti-interception, and high efficiency have become the necessary technical characteristics of modern military communications. For example, the LINK16 military communication data link used by the modern United States and NATO is The three-dimensional modulation technology of frequency hopping, spread spectrum and time hopping is adopted to achieve the purpose of improving communication confidentiality, anti-detection and anti-jamming. It has become an important information sharing platform for the land, sea and air forces, which greatly improves the The coordinated combat capability of the three armed forces and the overall combat effectiveness of local campaigns.

However, in the existing technology, the same pseudo-random sequence is usually used to directly spread the information. Therefore, when under attack, if the enemy already knows the frequency hopping pattern used by the system, he can use the known pseudo-random sequence to The information of each frequency hopping point is successfully despread. Therefore, there is still a hidden danger of the system being attacked and cracked in the prior art. Moreover, for the transmission of spread-spectrum signals, in the prior art, an up-converter is usually used to perform analog up-conversion on the spread-spectrum signal before transmission, but the cost of using an up-converter is relatively high, and due to the problems of temperature drift and aging of the analog circuit, the The transmitted spread spectrum signal is easily distorted.

Contents of the invention

The present invention provides a method for generating a mixed spread spectrum signal, a generating device and a sending device for overcoming the above-mentioned problems or at least partially solving the above-mentioned problems.

According to one aspect of the present invention, there is provided a device for generating a hybrid spread spectrum signal, comprising:

A direct spread module, configured to perform direct sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and perform polarity conversion on the first spread spectrum signal;

A frequency hopping module, configured to generate multiple frequency hopping carriers;

A hybrid spread spectrum signal generating module, electrically connected to the direct spread module and the frequency hopping module respectively, for generating a mixed spread spectrum signal according to the polarity-converted first spread spectrum signal and the multiple frequency hopping carriers .

According to another aspect of the present invention, there is provided a device for transmitting a mixed spread spectrum signal, including: a DAC module, a differential-single-ended conversion module, and the above-mentioned generating device for a mixed spread spectrum signal; wherein,

The device for generating the mixed spread spectrum signal is used to generate the mixed spread spectrum signal;

The DAC module is electrically connected to the generating device of the mixed spread spectrum signal, and is used to convert the mixed spread spectrum signal into a differential analog signal;

The differential-to-single-end conversion module is electrically connected to the DAC module, and is used to convert the differential analog signal into a single-end analog signal and send the single-end analog signal.

According to another aspect of the present invention, a method for generating a mixed spread spectrum signal is provided, including:

performing direct-sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and performing polarity conversion on the first spread spectrum signal;

Generate multiple frequency hopping carriers;

A mixed spread spectrum signal is generated according to the polarity converted first spread spectrum signal and the multiple frequency hopping carriers.

The invention provides a method for generating a hybrid spread spectrum signal, a generating device, and a transmitting device, by multiplying the polarity-converted first spread spectrum signal with multiple frequency-hopping carriers respectively, and multiplying all the multiplied The results are combined to generate a high-speed hybrid spread spectrum signal, which improves the sampling rate of transmitted data on the basis of the strong concealment of the direct spread communication system and the strong anti-interference performance of the frequency hopping system. The sending device can directly send the generated mixed frequency signal through the DAC module and the differential-single-ended conversion module. Compared with the traditional analog up-conversion with the up-converter, it greatly saves the cost and avoids the temperature drift of the analog circuit , Aging problem.

Description of drawings

FIG. 1 is a schematic structural diagram of a device for generating a mixed spread spectrum signal according to an embodiment of the present invention;

FIG. 2 is a schematic workflow diagram of a device for generating a mixed spread spectrum signal according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of a hardware structure of an apparatus for sending mixed spread spectrum signals according to an embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Fig. 1 is a schematic structural diagram of a device for generating a hybrid spread spectrum signal according to an embodiment of the present invention. As shown in Fig. 1, the device includes:

A direct spread module, configured to perform direct sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and perform polarity conversion on the first spread spectrum signal;

A frequency hopping module, configured to generate multiple frequency hopping carriers;

A hybrid spread spectrum signal generating module, electrically connected to the direct spread module and the frequency hopping module respectively, for generating a mixed spread spectrum signal according to the polarity-converted first spread spectrum signal and the multiple frequency hopping carriers .

Specifically, the direct spread module is used to perform direct sequence spread on the symbol information flow to generate a first spread spectrum signal, and perform polarity conversion on the first spread spectrum signal.

Among them, the direct sequence spread spectrum is to directly use the spread spectrum code sequence with a high code rate to spread the frequency spectrum of the signal at the transmitting end. The specific implementation of direct sequence spread spectrum is: multiplying the low code rate baseband signal information flow generated by the information source with a set of pseudo-random codes to realize direct sequence spread spectrum.

Perform polarity conversion on the first spread spectrum signal generated after the direct spread spectrum sequence. The specific process is to add a 1 to the back of each bit of the information sequence of the first spread spectrum signal, so that the information sequence becomes the signed number of +1 and -1, thereby obtaining the baseband signal of BPSK modulation, which is obtained here The baseband signal modulated by BPSK is the first spread spectrum signal after polarity conversion.

The frequency hopping module is used to generate multiple sine wave carriers with frequency hopping and initial phase setting. The role of the hybrid spread spectrum signal generation module is:

Multiplying the first spread-spectrum signal after polarity conversion with each sine wave carrier in the multi-channel sine wave carrier to generate corresponding multi-channel carrier modulation signals carrying frequency information and phase information; Carrier modulation signals are combined to generate a high-speed mixed spread spectrum signal.

The device provided in this embodiment multiplies the polarity-converted first spread-spectrum signal by multiple frequency-hopping carriers respectively, and combines all multiplied results to generate a high-speed mixed spread-spectrum signal. Based on the advantages of strong concealment of direct spread communication system and strong anti-interference performance of frequency hopping system, the sampling rate of transmitted data is improved.

Based on the foregoing embodiments, the hybrid spread spectrum signal generation module further includes:

A multiplier unit, configured to multiply the polarity-converted first spread-spectrum signal by each frequency-hopping carrier in the multiple frequency-hopping carriers to generate multiple frequency-hopping carrier modulation signals;

A parallel-to-serial conversion unit, electrically connected to the multiplier unit, for combining the multiple frequency-hopping carrier modulation signals into one modulation signal;

Wherein, the one modulation signal is the mixed spread spectrum signal.

Based on the above embodiments, the frequency hopping module is a direct digital frequency synthesizer.

Specifically, the direct digital frequency synthesizer can generate multiple frequency-hopping carriers whose frequency and phase information meet actual needs, and separate the multiple frequency-hopping carriers from the polarity-converted first spread-spectrum signals obtained in the above-mentioned embodiments Multiplied together, a multi-channel frequency-hopping carrier modulation signal carrying frequency information and phase information is obtained.

It should be noted that the frequency and phase of the frequency hopping carrier can be configured flexibly and accurately by using the direct digital frequency synthesizer, and the frequency and phase can realize rapid hopping to meet the speed requirement of frequency hopping frequency switching; at the same time, in this embodiment The frequency hopping carrier generated by the direct digital frequency synthesizer has a continuous phase when each frequency point is switched, which reduces the phase tracking of each frequency point when the receiving end performs carrier tracking. The information flow chip is aligned with the frequency hopping frequency switching position, which is convenient for reception Coherent accumulation when the terminal captures the signal.

Based on the above embodiments, the direct spread module, the frequency hopping module and the hybrid spread spectrum signal generation module are all located in the same FPGA chip.

The generation device provided by this embodiment improves the generation rate of the mixed frequency signal and reduces the bit error of the mixed frequency signal by setting the direct spread module, the frequency hopping module and the hybrid spread spectrum signal generation module in the same FPGA chip Rate.

Based on the above-mentioned embodiments, this embodiment provides a sending device for a mixed spread spectrum signal, the sending device includes: a DAC module, a differential-single-ended conversion module, and a generating device for a mixed spread spectrum signal in the above embodiment; wherein,

The device for generating the mixed spread spectrum signal is used to generate the mixed spread spectrum signal;

The DAC module is electrically connected to the generating device of the mixed spread spectrum signal, and is used to convert the mixed spread spectrum signal into a differential analog signal;

The differential-to-single-end conversion module is electrically connected to the DAC module, and is used to convert the differential analog signal into a single-end analog signal and send the single-end analog signal.

Specifically, the purpose of this embodiment is to send the generated mixed frequency signal. This embodiment can directly send the generated mixed frequency signal through the DAC module and the differential-single-ended conversion module, which is different from the traditional method of using up-conversion Compared with the analog up-conversion of the converter, the cost is greatly saved, and the problems of temperature drift and aging of the analog circuit are avoided.

Based on the above embodiments, the sending device in this embodiment further includes: a clock module, electrically connected to the DAC module, and configured to provide a clock signal for the DAC module.

Based on the above embodiment, the DAC module is further configured to send the clock signal to the device for generating the mixed spread spectrum signal, so that the DAC module and the device for generating the mixed spread spectrum signal are synchronized.

Preferably, the DAC module is a DAC chip, and the specific model is AD9739 chip.

Specifically, the AD9739 chip is an ultra-high-speed DAC chip with a quantization number of 14 bits and a maximum sampling rate of 2.5Gsps. A notable feature of this chip is that it can use its own hybrid mode to directly send S-band signals, which is different from traditional Compared with the up-conversion method, the cost is greatly saved, and the reliability of the equipment is improved.

Based on the above-mentioned embodiments, this embodiment, as a preferred embodiment, will specifically describe the present invention in conjunction with the accompanying drawings:

Fig. 2 is the workflow schematic diagram of the generation device of the hybrid spread spectrum signal provided according to the embodiment of the present invention, as shown in Fig. 2, the workflow of this generation device is:

The signal code in the form of bit information flow is multiplied by the preset pseudo-random code to perform direct sequence spread spectrum to obtain the first spread spectrum signal, and the polarity conversion of the first spread spectrum signal is performed.

According to the frequency hopping pattern and parameter design, the total frequency information and phase information that meet the actual needs are obtained. In order to increase the data rate, the frequency hopping carrier adopts 12 channels of parallel processing, and the frequency information and phase information corresponding to each frequency hopping carrier are obtained by calculating the total frequency information and phase information. And use a direct digital frequency synthesizer to generate 12 frequency hopping carriers whose frequency information and phase information meet the above requirements, and multiply the 12 frequency hopping carriers with the first spread spectrum signal after polarity conversion respectively to obtain 12 modulation signals of frequency information and phase information.

Perform parallel-serial conversion of the obtained 12 modulation signals into a high-speed modulation signal, transmit the signal to the ultra-high-speed AD9739 chip for digital-to-analog conversion into a differential analog signal, and then convert the differential analog signal through a balun into a Single-ended analog signal output to realize the generation and transmission of mixed spread spectrum signals.

It should be noted that the balun is a balanced-unbalanced transformer, which can also be called a differential-single-ended transformer. TC1-33-75G2+ is selected, and the frequency characteristic is relatively stable. The balun is electrically connected with the AD9739 chip, and is used to convert the differential analog signal into a single-ended analog signal,

By changing the preset pseudo-random code and then performing the above process, the first spread spectrum signal of the direct sequence spread spectrum corresponding to the different pseudo-random code can be obtained, thereby realizing variable pseudo-random code. By modifying the rate at which the frequency information of the frequency hopping pattern changes, the control of the switching rate of the frequency hopping frequency can be realized.

Taking the S-band signal of hybrid spread spectrum at the sending end as an example, the specific implementation process of the present invention is further described:

The frequency band of the frequency hopping carrier under the high signal-to-noise ratio is radio frequency, and the noise is Gaussian white noise.

Step 1. First, the sending end adopts a bit stream with a rate of 2.5kHz, and directly multiplies the bit stream with a set of pseudo-random codes with a length of 1024 to perform direct sequence spread spectrum to obtain the spread spectrum information sequence, and the spread spectrum The chip rate is 2.56MHz.

Step 2: add a 1 to each bit of the spread-spectrum modulated information sequence, so that the information sequence becomes a signed number of +1 and -1, and a baseband signal modulated by BPSK is obtained.

Step 3: Utilize the direct digital frequency synthesizer The direct digital frequency synthesizer generates 12 channels of sine wave carriers whose frequency can be hopped and whose initial phase can be set. Direct digital frequency synthesizer The data depth of the direct digital frequency synthesizer is 16384, the bit width is 14bit, and a 1/4 look-up table is used. The bit width of the phase accumulator is 48bit, and the precision is 1.96608Gbps/248. Obtain the frequency control word corresponding to each frequency hopping point (stepping of the phase accumulator) according to the frequency hopping pattern, and calculate the frequency control word corresponding to 12 channels. By changing the frequency control word, the frequency hopping can be realized, thereby obtaining 12 The frequency hopping carrier; and by changing the initial value of the phase accumulator, the initial phase of the frequency hopping carrier can be modified, and the phase can be arbitrarily configured between 0°-360°. The rate of frequency hopping carrier is 163.84MHz.

Step 4: Multiply the baseband data obtained in step 2 with the 12 frequency-hopping sine wave carriers obtained in step 3 to perform carrier modulation, and the multiplied 16-bit data is truncated to 14 bits from the high-order bits. The bandwidth of the baseband data is negligible relative to the carrier frequency, so the phase of the baseband data does not need to be set. Then 12 channels of modulated signals are input into the parallel-to-serial conversion unit, and the data is read in the form of a high-speed clock and DDR with a clock that is 3 times the carrier frequency, so as to obtain a modulated signal with a rate of 12 times the carrier frequency, thus generating a mixed signal. spread spectrum signal.

Step 5. The data processing of the above four steps is realized in the FPGA chip, and then the mixed spread spectrum signal obtained above is transmitted to the AD9739 chip for digital-to-analog conversion, because the data is differential in the FPGA and AD9739, so A differential-to-single-ended balun is connected to the output of the AD9739 to convert the output differential analog signal into a single-ended analog signal output.

Figure 3 is a schematic diagram of the hardware structure of a sending device for a hybrid spread spectrum signal according to an embodiment of the present invention. The voltage required by each device. The PROM chip XCF128X is connected to the FPGA chip to save the program of the signal generation module. A clock module is connected externally, and the clock module outputs the clock signal to the ultra-high-speed AD9739 chip. The clock signal is used as the sampling clock for the DAC to transmit data, and the AD9739 outputs the clock signal to the FPGA chip, so that the FPGA chip performs signal processing according to the clock signal. The FPGA chip is connected to the AD9739 chip for data transmission, and the output of the AD9739 is connected to a balun, which is used to convert the differential analog signal into a single-ended analog signal output.

Based on the foregoing embodiments, a method for generating a hybrid spread spectrum signal in this embodiment includes:

performing polarity conversion on the first spread spectrum signal generated through direct sequence spread spectrum;

Generate multiple frequency hopping carriers;

A mixed spread spectrum signal is generated according to the polarity converted first spread spectrum signal and the multiple frequency hopping carriers.

It should be noted that each step in the generation method of this embodiment is executed by each module in the embodiment of the above-mentioned generation device. For details, refer to the embodiment of the above-mentioned generation device, which is not limited in this embodiment.

Wherein, said generating a mixed spread spectrum signal according to the polarity-converted first spread spectrum signal and the multiple frequency hopping carriers further includes:

multiplying the polarity-converted first spread-spectrum signal by each of the multiple frequency-hopping carriers to generate multiple frequency-hopping carrier modulation signals;

Combining the multiple channels of frequency-hopping carrier modulation signals into one channel of modulation signals; wherein, the channel of modulation signals is the mixed spread spectrum signal.

As a preferred embodiment, the method for measuring the phase continuity and information flow chip and frequency hopping frequency switching synchronization of the hybrid spread spectrum signal produced by the above embodiment is: the output of the AD9739 passes through the filter, and then passes through the coaxial cable. transmitted to the receiving end. The receiving end performs quadrature mixing on the mixed spread spectrum signal received, and down-converts it to the baseband, and the down-converted signal undergoes low-pass filtering to obtain the baseband signal. After the baseband signal is down-sampled, the obtained data finds the complete frequency corresponding to the first hop and the precise starting position, and then de-hops the signal according to the frequency-hopping pattern. The de-hopped signal can observe the chip structure. By comparing the chips of the information stream, it can be concluded that the synchronization between the information stream chips and the frequency hopping frequency is switched. The de-hopped signal is de-spread using the pseudo-random code used in direct-sequence spread spectrum. Then capture the correlation peak of the despreading result, and process the obtained information to obtain the frequency and phase information, and then compare the phase difference between each frequency point to obtain the phase continuity of the mixed spread spectrum signal situation, complete the measurement process.

To sum up, the present invention multiplies the polarity-converted first spread-spectrum signal with multiple frequency-hopping carriers, and combines all the multiplied results to generate a high-speed mixed spread-spectrum signal. On the basis of the advantages of strong concealment of the direct spread communication system and the strong anti-interference performance of the frequency hopping system, the data rate is improved. Using the ultra-high-speed DAC chip AD9739 with a sampling rate of up to 2.5Gsps can directly send S-band modulation signals. Compared with the traditional up-converter for analog up-conversion, it greatly saves costs and avoids temperature drift and aging of analog circuits. problem; the frequency and phase of the frequency hopping carrier can be configured flexibly and accurately by using the direct digital frequency synthesizer, and the frequency and phase can realize rapid hopping to meet the speed requirement of frequency hopping frequency switching; The phase of each frequency point of the frequency hopping carrier generated by the frequency synthesizer is continuous when switching, which reduces the phase tracking of each frequency point when the receiving end performs carrier tracking. Coherent accumulation while capturing.

Finally, the solutions of the present invention are only preferred implementations, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A generating device for mixing spread spectrum signals, characterized in that, comprising: A direct spread module, configured to perform direct sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and perform polarity conversion on the first spread spectrum signal; A frequency hopping module, configured to generate multiple frequency hopping carriers; A hybrid spread spectrum signal generating module, electrically connected to the direct spread module and the frequency hopping module respectively, for generating a mixed spread spectrum signal according to the polarity-converted first spread spectrum signal and the multiple frequency hopping carriers . 2. generating device according to claim 1, is characterized in that, described hybrid spread spectrum signal generation module further comprises: A multiplier unit, configured to multiply the polarity-converted first spread-spectrum signal by each frequency-hopping carrier in the multiple frequency-hopping carriers to generate multiple frequency-hopping carrier modulation signals; A parallel-to-serial conversion unit, electrically connected to the multiplier unit, for combining the multiple frequency-hopping carrier modulation signals into one modulation signal; Wherein, the one modulation signal is the mixed spread spectrum signal. 3. The generating device according to claim 1, wherein the frequency hopping module is a direct digital frequency synthesizer. 4. The sending device according to claim 1, wherein the direct spread module, the frequency hopping module and the hybrid spread spectrum signal generation module are all located in the same FPGA chip. 5. A sending device for a hybrid spread spectrum signal, characterized in that it comprises: a DAC module, a differential-single-ended conversion module and the generating device for the hybrid spread spectrum signal described in any one of claims 1-4; wherein, The device for generating the mixed spread spectrum signal is used to generate the mixed spread spectrum signal; The DAC module is electrically connected to the generating device of the mixed spread spectrum signal, and is used to convert the mixed spread spectrum signal into a differential analog signal; The differential-to-single-end conversion module is electrically connected to the DAC module, and is used to convert the differential analog signal into a single-end analog signal and send the single-end analog signal. 6. The sending device according to claim 5, further comprising: A clock module is electrically connected to the DAC module and used to provide a clock signal for the DAC module. 7. The sending device according to claim 6, wherein the DAC module is also used to send the clock signal to the generating device of the mixed spread spectrum signal, so that the DAC module and the The means for generating the mixed spread spectrum signal are synchronized. 8. The sending device according to claim 5, wherein the DAC module is an AD9739 chip. 9. A method for generating a hybrid spread spectrum signal, comprising: performing direct-sequence spread spectrum on the symbol information flow to generate a first spread spectrum signal, and performing polarity conversion on the first spread spectrum signal; Generate multiple frequency hopping carriers; A mixed spread spectrum signal is generated according to the polarity converted first spread spectrum signal and the multiple frequency hopping carriers. 10. The generation method according to claim 9, wherein, generating a mixed spread spectrum signal according to the first spread spectrum signal through polarity conversion and the multiple frequency hopping carriers, further comprising: multiplying the polarity-converted first spread-spectrum signal by each of the multiple frequency-hopping carriers to generate multiple frequency-hopping carrier modulation signals; Combining the multiple channels of frequency-hopping carrier modulation signals into one channel of modulation signals; wherein, the channel of modulation signals is the mixed spread spectrum signal.