A spread spectrum distance measurement method based on Sunzi theorem distance deambiguation

Abstract

The invention discloses a spread spectrum ranging method based on Sunzi theorem distance deambiguation. The method generates three pseudo code sequences at the transmitting end and generates a spread spectrum intermediate frequency signal; mixes the analog signal of the uplink mixer with the spread spectrum intermediate frequency signal to generate an uplink radio frequency signal, and sends it through an antenna; after the satellite receives the uplink radio frequency signal sent by the ground antenna, it despreads the signal by processing to obtain three pseudo code sequences; compares the three pseudo code sequences at the transmitting and receiving end to obtain the remainders when the three pseudo codes are measured; calculates the number of code chips using the formula of Sunzi theorem; calculates the total time delay of microwave round trip space, removes the ground zero value and the satellite zero value, and obtains the space distance from the ground antenna port to the satellite. The invention can select the appropriate number and length of pseudo codes according to the actual distance, and the ranging accuracy is consistent with the traditional pseudo code ranging accuracy.

Description

Technical Field

[0001] The invention discloses a spread spectrum ranging method for performing distance deambiguation based on the Sunzi theorem, which can be applied to a spread spectrum ranging device for performing distance deambiguation based on the Sunzi theorem in an integrated transmitter and receiver, is suitable for a satellite system with frequency conversion forwarding, and can perform single-station ranging or multi-station ranging and orbit determination on a satellite. Background Art

[0002] In the field of aerospace measurement and control, traditional ranging generally adopts two systems: acoustic ranging and pseudo-code ranging. The USB system adopts acoustic ranging, which uses a mechanism of multiple acoustic wheels to resolve distance ambiguity. This mechanism has a long distance capture time and low ranging accuracy. It is a relatively traditional ranging method. In the spread spectrum system, pseudo-code ranging generally resolves distance ambiguity through orbit prediction or adding data frames. The maximum unambiguous distance of pure pseudo-code ranging is related to the pseudo-code length. The short code matching distance is short. Although long code ranging can increase the unambiguous distance, the capture time is long and it is not suitable for ranging systems that require fast capture. Summary of the invention

[0003] The purpose of the present invention is to avoid the deficiencies in the above-mentioned background technology and provide a spread spectrum ranging method for distance deambiguation based on the Sunzi theorem. This ranging method is suitable for a satellite system with frequency conversion forwarding.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A spread spectrum distance measurement method based on Sunzi theorem distance deambiguation includes the following steps:

[0006] (1) Parameter initialization, determine the pseudo code periods m1, m2, and m3, calculate the product M of the three, and find the m i A number M that is divisible by two other numbers with a remainder of 1 i , i=1,2,3;

[0007] (2) Get the pseudo code clock f w , code element width The phase value that is less than an integer number of chips is PHn;

[0008] (3) Generate a pseudo code clock through a pseudo code frequency generator, drive three pseudo code generators to generate pseudo code sequences of three lengths, and send the pseudo code clock to a carrier frequency generator to generate a local intermediate frequency single carrier signal;

[0009] (4) The pseudo codes generated by the three pseudo code generators are summed, and the sequence obtained by the summation is used to phase modulate the local intermediate frequency single carrier signal. The modulated signal is converted into a spread spectrum intermediate frequency signal through a digital-to-analog converter; the analog signal of the uplink mixer is mixed with the spread spectrum intermediate frequency signal to generate an uplink radio frequency signal, which is sent out through the antenna;

[0010] (5) After the satellite receives the uplink RF signal from the ground antenna, it is converted and forwarded by the satellite frequency converter and then sent back to the ground, where it is mixed with the ground downlink local oscillator to generate a downlink intermediate frequency input signal;

[0011] (6) After the downlink intermediate frequency input signal is sampled and digitally down-converted, the signal is despread by the capture and tracking module to obtain three pseudo code sequences;

[0012] (7) Compare the three pseudo code sequences obtained in step (6) with the pseudo code sequence generated in step (3) to obtain the remainders C1, C2, and C3 when the three pseudo codes are measured;

[0013] (8) Using Sun Tzu's Theorem Formula C 总 '=C1*M1+C2*M2+C3*M3Calculate C 总 ', calculate C 总 'The remainder C when divided by M 总 ;

[0014] (9) Calculate the total time delay τ of microwaves going back and forth in space 总 =τ w *(C 总 +PHn), remove the ground zero value τ 地面零值 and the zero value τ on the star 星上零值 , according to the speed of light C, we can get the spatial distance from the ground antenna to the satellite:

[0015]

[0016] Compared with the background technology, the present invention has the following advantages:

[0017] 1. The present invention proposes a method for distance deambiguation by adding pseudocodes with different pseudocode periods for measurement in a system without orbit prediction or data frame. Based on the pseudocode system, the method measures the distance of the target by two or three pseudocodes with mutually prime pseudocode periods to improve the maximum unambiguous distance. The maximum unambiguous distance can be adjusted by selecting a suitable pseudocode period according to the actual situation. The method can directly obtain the actual distance value without the help of other auxiliary means.

[0018] 2. The distance range measured by the traditional pseudo-code ranging method is related to the length of the pseudo-code period. The longer the pseudo-code period, the farther the measured distance range is. The longer the pseudo-code period, the more difficult it is to capture the receiver. If the distance is greater than the pseudo-code period, orbit prediction and other methods are used to resolve the distance ambiguity. This method is based on the problem-solving idea of ​​Sun Tzu's theorem, that is, the Chinese remainder theorem. Two or three pseudo-codes with mutually prime pseudo-code periods are used to measure the distance of the satellites separately. The remaining number of code chips when measuring the distance for each pseudo-code length can be obtained respectively. The total number of pseudo-code code chips for the current measured distance can be accurately obtained using the remaining number of code chips.

[0019] 3. The present invention can select the appropriate number and length of pseudo codes according to the actual distance, and the ranging accuracy is consistent with the traditional pseudo code ranging accuracy. Compared with the traditional ranging, there is no need to change the hardware design. The ranging algorithm is compatible with the hardware platform of the traditional ranging system, and long-distance ranging can be implemented without the system providing distance prediction or other auxiliary measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle of an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in further detail below.

[0022] A spread spectrum ranging method based on Sunzi theorem distance deambiguation. Pseudo-code ranging measures the total number of code chips C in the two-way space. 总 + The phase value PHn of the whole code chip is not enough to obtain the distance value, so the key to the success of the measurement lies in accurately measuring C 总 , total number of chips C 总 = pseudo code period length P i *Number of pseudo code cycles i + Number of remaining chips C i Since the measured distance may be greater than the code length of the current pseudo code period, the space may contain several pseudo code periods. If there is no orbit prediction or data frame, the number of pseudo code periods N in the space cannot be obtained. i This method can directly obtain C by adding pseudo-code measurements of different lengths without adding auxiliary measures to the system. 总 .

[0023] This method uses two or more pseudocodes whose pseudocode periods are prime to each other to measure the distance of the satellite. The two-way distance value to be measured is the dividend, and the pseudocode periods that are prime to each other are equivalent to the divisors. Corresponding quotients and remainders will be obtained. According to the Sun Tzu theorem, the minimum value that can meet the requirements of all equations is the two-way distance value to be measured, and this value is less than the product of all divisors. To accurately measure the actual distance value, the unambiguous value must be greater than the actual measured value, that is, the product of all divisors is greater than the maximum measured two-way distance value.

[0024] The transmit-receive integrated spread spectrum ranging device based on Sunzi's theorem for distance deambiguation performs two-way ranging of the target under the scheduling of the program, and can obtain the chip remainder C of each measurement. i According to the formula of Sun Zi's theorem, the total number of complete chips C can be directly calculated. 总 , the spatial delay is obtained based on the pseudo code clock rate, and then converted into a distance value based on the speed of light.

[0025] This method is particularly suitable for distance measurement or orbit determination of high-orbit synchronous satellites.

[0026] This method can be applied to Figure 1 The illustrated transmitter-receiver integrated spread spectrum distance measurement device for distance deambiguation based on the Sunzi theorem comprises the following modules:

[0027] AD sampler 1; carrier frequency generator 2; short code, carrier capture and tracking unit 3; pseudo code frequency generator 4; pseudo code 1 generator 5; pseudo code 2 generator 6; pseudo code 3 generator 7; Sunzi determinate ambiguity resolution module 8; distance solution 9; pseudo code frequency generator 10; pseudo code 1 generator 11; pseudo code 2 generator 12; pseudo code 3 generator 13; carrier frequency generator 14; DA converter 15.

[0028] The workflow of this method is as follows:

[0029] Initialize the parameters, select appropriate parameters according to the actual situation, determine the pseudo code period m1, m2, m3, calculate the product M of the three, and find the m i A number M that is divisible by two other numbers with a remainder of 1 i ;

[0030] Take the pseudo code clock as f w , code element width The phase value of less than an integer number of chips is PHn, and the total microwave round-trip space delay τ 总 =τ w *(C 总 +PHn);

[0031] The local pseudo code frequency generator generates a pseudo code clock, drives three pseudo code generators to generate pseudo code sequences of three lengths, and sends it to the carrier frequency generator to generate a local intermediate frequency single carrier signal;

[0032] The sequence obtained by summing the pseudo codes generated by the three pseudo code generators performs phase modulation on the local intermediate frequency single carrier, and the DA converter generates a spread spectrum intermediate frequency signal. The analog signal of the uplink mixer is mixed with the spread spectrum intermediate frequency signal to generate a radio frequency uplink signal that is sent out through the antenna;

[0033] After the satellite receives the uplink RF signal from the ground antenna, it is converted and forwarded by the satellite frequency converter and then sent back to the ground for mixing with the ground downlink local oscillator to generate a downlink intermediate frequency input signal.

[0034] The downlink IF input signal is sampled by the IF, and after digital down-conversion, the signal is despread by the capture and tracking module to obtain three pseudo code sequences;

[0035] The three pseudo codes obtained by the receiving end are compared with the pseudo codes of the transmitting end to obtain the remainders C1, C2, and C3 of the three pseudo codes when measured;

[0036] Using Sun Tzu's Theorem Formula C 总 '=C1*M1+C2*M2+C3*M3Calculate and get C 总 ', because C 总 Must be less than the three scores M, use C 总 'Subtract M until the value obtained is less than M, and this value is the required C 总 ;

[0037] Get C 总 Then, according to the formula τ w *(C 总 +PHn) to obtain the total time delay of the measured microwave round trip space, removing the zero value τ on the ground 地面零值 and the zero value τ on the star 星上零值 According to the speed of light C, the spatial distance from the ground antenna port to the satellite can be obtained.

[0038] The following is an example of an actual project.

[0039] A spread spectrum distance measurement method based on Sunzi theorem distance deambiguation includes the following steps:

[0040] (I) Parameter design

[0041] Initialize the parameters and select the pseudo code clock as f according to the system signal bandwidth condition w =500KHz, The distance corresponding to each code element is C×τ w =600 meters. Where C is the speed of light;

[0042] The maximum possible distance to the satellite is about 200,000 km. The working principle of distance measurement is to measure the delay between sending and receiving codes. Because the delay is the delay of the signal reaching the target and returning, the number of code elements is

[0043] According to the mutually prime condition of Sun Tzu's theorem, the three pseudo code periods m1, m2, and m3 are set to 79, 83, and 107 respectively, which are equivalent to the divisors in Sun Tzu's theorem. The product of the three is M=m1*m2*m3=701559, which satisfies the condition of being greater than 666666 and the final calculation result must be less than M;

[0044] Find out the m i A number M that is divisible by two other numbers with a remainder of 1 i ; After calculation, M1 = 12*83*107, M2 = 51*79*107, M3 = 25*79*83;

[0045] (II) Ranging Process

[0046] The process of launching the device:

[0047] The local pseudo code frequency generator 10 generates a pseudo code clock, drives the pseudo code 1 generator 11, the pseudo code 2 generator 12, and the pseudo code 3 generator 13 to generate pseudo code sequences of three lengths, and sends them to the carrier frequency generator 14 to generate a local intermediate frequency single carrier signal;

[0048] The sequence obtained by summing the pseudo codes generated by the pseudo code 1 generator 11, the pseudo code 2 generator 12, and the pseudo code 3 generator 13 performs phase modulation on the intermediate frequency carrier generated by the carrier frequency generator 14 to generate a spread spectrum intermediate frequency signal;

[0049] The uplink phase lock of the uplink uses the reference local oscillator clock to generate an analog signal for the uplink mixer. The analog signal of the uplink mixer is mixed with the spread spectrum intermediate frequency signal output by the DA converter 15 to generate a radio frequency uplink signal which is sent out through the antenna.

[0050] Receiving device process:

[0051] After the satellite receives the uplink RF signal from the ground antenna, it is converted and forwarded by the satellite frequency converter and then sent back to the ground for mixing with the ground downlink local oscillator to generate a downlink intermediate frequency input signal.

[0052] The intermediate frequency receiving module AD sampler 1 samples the downstream intermediate frequency input signal, performs digital down-conversion with the two orthogonal signals generated by the local carrier frequency generator 2, and obtains the I and Q two-way orthogonal spread spectrum signals COS and SIN;

[0053] Set the initial carrier frequency and pseudo code initial phase. Adjust the local oscillator of carrier frequency generator 2 and the delay of pseudo code, and perform energy detection on the signal until the signal energy exceeds the threshold, the Doppler and delay of the signal fall into the initially set capture window, and the spread spectrum signal is despread;

[0054] After capturing the signal, the carrier loop and pseudo code loop enter the tracking state to track the carrier and pseudo code phases respectively;

[0055] (III) Distance calculation

[0056] Compare the three pseudo codes obtained by the receiving end with the pseudo codes of the transmitting end to obtain the remainders C1, C2, and C3 when the three pseudo codes are measured;

[0057] Using Sun Tzu's Theorem Formula C 总 '=C1*M1+C2*M2+C3*M3, because C 总 It must be less than the product of the three, M, and finally C 总 C 总 'Subtract M until C 总 Until it is less than M;

[0058] Get C 总 Then according to the formula τ w *(C 总 +PHn) to obtain the total time delay in the measured space, removing the zero value τ on the ground 地面零值 and the zero value τ on the star 星上零值 According to the speed of light C, the spatial distance from the ground antenna to the satellite can be obtained Among them, τ 地面零值 The device of the present invention can be used to measure τ through a bias feed loop. 星上零值 Can be provided by the satellite manufacturer;

[0059] The above steps can complete the calculation of the target distance.

[0060] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution using equivalent replacement or equivalent transformation forms falls within the protection scope required by the present invention.

Claims

1. A spread spectrum ranging method based on Sunzi theorem distance deambiguation, characterized in that: The following steps are involved: (1) Parameter initialization, determine the pseudo code periods m1, m2, and m3, calculate the product M of the three, and find the m i A number M that is divisible by two other numbers with a remainder of 1 i , i=1,2,3; (2) Get the pseudo code clock f w , code element width The phase value that is less than an integer number of chips is PHn; (3) Generate a pseudo code clock through a pseudo code frequency generator, drive three pseudo code generators to generate pseudo code sequences of three lengths, and send the pseudo code clock to a carrier frequency generator to generate a local intermediate frequency single carrier signal; (4) The pseudo codes generated by the three pseudo code generators are summed, and the sequence obtained by the summation is used to phase modulate the local intermediate frequency single carrier signal. The modulated signal is converted into a spread spectrum intermediate frequency signal through a digital-to-analog converter; the analog signal of the uplink mixer is mixed with the spread spectrum intermediate frequency signal to generate an uplink radio frequency signal, which is sent out through the antenna; (5) After the satellite receives the uplink RF signal from the ground antenna, it is converted and forwarded by the satellite frequency converter and then sent back to the ground, where it is mixed with the ground downlink local oscillator to generate a downlink intermediate frequency input signal; (6) After the downlink intermediate frequency input signal is sampled and digitally down-converted, the signal is despread by the capture and tracking module to obtain three pseudo code sequences; (7) Compare the three pseudo code sequences obtained in step (6) with the pseudo code sequence generated in step (3) to obtain the remainders C1, C2, and C3 when the three pseudo codes are measured; (8) Using Sun Tzu's Theorem Formula C 总 '=C1*M1+C2*M2+C3*M3Calculate C 总 ', calculate C 总 'The remainder C when divided by M 总 ; (9) Calculate the total time delay τ of microwaves going back and forth in space 总 =τ w *(C 总 +PHn), remove the ground zero value τ 地面零值 and the zero value τ on the star 星上零值 , according to the speed of light C, we can get the spatial distance from the ground antenna to the satellite:

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