A pulse compression based radio frequency communication band range difference measurement system and method

Abstract

A kind of radio frequency communication wave band distance difference measurement system and method based on pulse compression technique, including radio frequency communication wave band transmitter and receiver: transmitter includes radio frequency signal source, exports radio frequency wave band single-frequency sine wave signal or linear sweep signal;Low-frequency signal source, exports single polarity periodic pulse wave signal;High-speed electronic switch, radio frequency power amplifier, log antenna, for transmitting radio frequency signal;Method includes distance difference measurement method and distance difference calculation digital signal processing algorithm.The present application utilizes radio frequency wave band communication technology based on pulse compression technique, realizes high sensitivity, high precision, low cost, strong expansibility distance difference measurement calculation, and can be used in the ranging and positioning of navigation, aerospace, unmanned aerial vehicle, automatic driving and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to a radio frequency communication band range difference determination system and method based on pulse compression technology, the system comprising a radio frequency communication band transmitter and a radio frequency communication band receiver, the method comprising a range difference calculation digital signal processing algorithm based on the above-mentioned system. BACKGROUND

[0002] Pulse compression processing is to obtain the corresponding pulse compression output signal through signal processing technology, so that higher output signal signal-to-noise ratio can be obtained without increasing the radar transmitting power. According to the implementation method, it can be divided into time domain pulse compression and frequency domain pulse compression processing method.

[0003] The traditional pulse compression ranging system is commonly used in radar, and the transmitting and receiving systems are located at the radar end. In order to realize high sensitivity and high precision, the attenuation of electromagnetic waves by the reflecting material is offset, which often requires higher transmitting power and higher transmitting frequency, the transmitting frequency is usually in X band and higher, and the signal isolation between the transmitting end and the receiving end is needed, and the cost of the receiver system is also higher. At the same time, the demodulation algorithm of the traditional pulse compression ranging system is too complex, and the receiver requires higher cost.

[0004] CN2018104411843 gives a system for bidirectional time-of-flight ranging and communication based on wireless pulse radio frequency signals, including: UWB device, ranging device, wherein the wireless pulse radio frequency signal device is used for communication through wireless pulse radio frequency signal, and ranging through bidirectional time-of-flight ranging method; the ranging device and the wireless pulse radio frequency signal device, the ranging device includes a processor, a transceiver, an antenna, an ID register, the ranging device includes a processor, a transceiver, an antenna, a setting module, an ID register and a communication interface, wherein the processor is used for data processing; the transceiver is connected with the processor, the transceiver is also connected with the antenna, the transceiver is used for outputting ranging request through the antenna, and also receiving ranging request of other ranging devices through the antenna, the antenna is used for data transmission; the ID register is a non-volatile memory, used for storing ID identification number of all ranging devices.

[0005] CN2015109540688 provides a radio frequency (RF) signal ranging method and system, which can estimate the distance between a transmitting node and a receiving node without relying on RF received signal strength measurement hardware. The method includes: obtaining a table showing the relationship between the occurrence probability of different ranging codewords and the distance between nodes, where the distance between nodes is the distance between the transmitting and receiving nodes; transmitting a ranging group column through the transmitting node, the ranging group column including multiple groups with different levels of RF transmission power, the group content containing the RF transmission power information of the group; receiving the groups transmitted by the transmitting node through the receiving node, and constructing a ranging codeword based on the receiving result; estimating the distance between the transmitting and receiving nodes based on the constructed ranging codeword and the obtained table showing the relationship between the occurrence probability of different ranging codewords and the distance between nodes. This method is particularly suitable for the field of positioning technology. Summary of the Invention

[0006] The purpose of this invention is to propose a radio frequency band communication technology based on pulse compression to achieve a high-sensitivity, high-precision, low-cost, and highly scalable distance difference measurement system, which can be used for high-precision ranging, multi-target detection, and three-point positioning. It can be applied to ranging and positioning in fields such as navigation, aerospace, drones, and autonomous driving. The system includes a radio frequency communication band transmitter and a radio frequency communication band receiver, and the method includes a digital signal processing algorithm for distance difference calculation.

[0007] The technical solution of this invention is a distance difference measurement system for radio frequency communication bands based on pulse compression technology. The system includes a radio frequency communication band transmitter and a radio frequency communication band receiver.

[0008] The radio frequency communication band transmitter includes the following components that are electrically connected in sequence:

[0009] Radio frequency signal source, outputting a single-frequency sine wave signal or a linear sweep frequency signal in the radio frequency band;

[0010] A low-frequency signal source that outputs a unipolar periodic pulse wave signal;

[0011] The high-speed electronic switch enables pulse shaping by multiplying two signals.

[0012] Radio frequency power amplifiers effectively improve the power of pulse compression signals output by transmitters;

[0013] Logarithmic antennas are used to transmit radio frequency signals.

[0014] Both the radio frequency (RF) signal source and the low-frequency signal source are input to a high-speed electronic switch, then mixed and amplified by an RF power amplifier before being transmitted by a logarithmic antenna.

[0015] A further design feature of the radio frequency communication band transmitter is that the output signal frequency of the radio frequency signal source is adjustable between 1 GHz and 1.5 GHz, and the output signal power is adjustable between -40 dBm and 0 dBm. Specifically, the output signal of the radio frequency signal source can be a single-frequency sine wave signal or a linearly swept frequency signal.

[0016] A further design of the radio frequency communication band transmitter is that the low-frequency signal source can output a periodic pulse wave signal. The pulse wave is unipolar, with a high level of 5 volts and a low level of zero. The frequency is continuously adjustable between 1 kHz and 100 kHz, the duty cycle is continuously adjustable between 0 and 100%, and the output signal amplitude is continuously adjustable between 0 and 5 volts.

[0017] A further design feature of the radio frequency communication band transmitter is that the high-speed electronic switch must support a switching rate of at least 100kHz, and the frequency range of the input signal channel must cover the 1GHz to 1.5GHz band. The high-speed electronic switch enables pulse shaping by multiplying two signals.

[0018] A further design feature of the radio frequency communication band transmitter is that the radio frequency power amplifier operates linearly in the range of 1 GHz to 1.5 GHz, with a power gain greater than 20 dB. The radio frequency power amplifier can effectively improve the power of the pulse compression signal output by the transmitter.

[0019] A further design of the radio frequency communication band transmitter is that the logarithmic antenna operates in the frequency band of 1GHz-1.5GHz, has an antenna gain of 12-18dB, can be omnidirectional or directional in radiation direction, and has an antenna standing wave ratio of less than or equal to 1.5.

[0020] The radio frequency communication band receiver includes the following components that are electrically connected in sequence:

[0021] Log-numerical antennas are used to receive radio frequency signals;

[0022] Low-noise amplifiers improve the signal-to-noise ratio of input signals and suppress noise in input signals;

[0023] A passive mixer down-converts the input signal using the local oscillator signal;

[0024] The local oscillator signal source generates a standard sinusoidal local oscillator signal with a fixed frequency and amplitude.

[0025] Passive bandpass filters, used as intermediate frequency filters in receivers, can effectively reduce the equivalent noise bandwidth.

[0026] Intermediate frequency amplifier (IF amplifier) ​​amplifies the intermediate frequency signal, improving the receiver's sensitivity and dynamic range.

[0027] An oscilloscope or computer is used to acquire waveform signals and calculate the distance difference. The logarithmic antenna is connected in sequence to a low-noise amplifier, a passive mixer, a passive bandpass filter, an intermediate frequency amplifier, and an oscilloscope or computer for acquiring waveform signals and calculating the distance difference. The output of the local oscillator signal source is connected to the second input of the passive mixer.

[0028] A further design feature of the radio frequency communication band receiver is that the input and output impedances of each module are both 50 ohms, and each module is connected to the other using coaxial cables; each module is grounded at a single point using a 0-ohm resistor.

[0029] A further design of the radio frequency communication band receiver is that the logarithmic antenna operates in the frequency band of 1GHz-1.5GHz, has an antenna gain of 12-18dB, an antenna VSWR of less than or equal to 1.5, and is vertically polarized.

[0030] A further design of the radio frequency communication band receiver is that the low noise amplifier operates in the frequency range of 1GHz to 1.5GHz, has a noise figure of less than 1dB, and an amplifier gain of greater than 10dB.

[0031] A further design feature of the radio frequency communication band receiver is that the passive mixer operates in the 1GHz to 1.5GHz frequency range, with a typical conversion loss of less than 7dB. The passive mixer performs down-conversion, shifting the carrier frequency of the input pulse compression signal from the 1GHz to 1.5GHz frequency range to a frequency range of 90MHz-110MHz centered at 100MHz.

[0032] A further design of the radio frequency communication band receiver is that the frequency of the sinusoidal signal output by the intrinsic signal source is continuously adjustable in the range of 900MHz to 1.4GHz, and the output signal power is continuously adjustable in the range of -40dBm to 10dBm.

[0033] A further design feature of the radio frequency communication band receiver is that the passive bandpass filter has a -3dB passband of 90MHz to 110MHz and an in-band insertion loss of less than 1dB.

[0034] A further design feature of the radio frequency communication band receiver is that the intermediate frequency amplifier (IF amplifier) ​​must operate within a frequency range of 100MHz and have a gain greater than 20dB. Increasing the gain of the IF amplifier helps to improve the receiver's sensitivity.

[0035] A further design of the radio frequency communication band receiver involves using an oscilloscope for high-speed sampling of the down-converted pulse compression signal from the receiver. The oscilloscope is set to deep storage mode, and its real-time sampling rate is guaranteed to be greater than or equal to 500MHz (oscilloscope recording time = maximum storage depth divided by real-time sampling frequency). The oscilloscope's high-speed ADC performs analog-to-digital conversion on the waveform of the pulse compression signal and stores it. Simultaneously, the stored waveform data file is imported into a computer. The computer is used to run a distance difference calculation digital signal processing algorithm to digitally demodulate the down-converted pulse compression signal from the receiver.

[0036] The distance difference measured in this invention is defined as the difference between the distance from a transmitter to receiver 1 and the distance from receiver 2.

[0037] like Figure 3 As shown, the distance difference measurement system consists of one transmitter and two receivers: receiver 1 and receiver 2. A is the distance from transmitter to receiver 1, B is the distance from transmitter to receiver 2, and C is the distance between receiver 1 and receiver 2. This invention's distance difference measurement system can measure the difference d between the distance from transmitter to receiver 1 and the distance from transmitter to receiver 2, that is:

[0038] d=|AB| (1)

[0039] d represents the distance difference measured by the distance difference measurement system of this invention.

[0040] exist Figure 3 In the diagram, receiver 1 and receiver 2 are in fixed positions, and the distance C between them is a known constant.

[0041] The transmitter system mentioned in this invention transmits a pulse compressed signal, and the receiver system mentioned in this invention simultaneously receives the pulse compressed signal. After the receiver completes the pre-amplification, down-conversion, filtering, and intermediate frequency amplification of the signal, it uses an oscilloscope to sample and store the pulse compressed signal waveform at high speed in real time. At the same time, the waveform data after sampling and quantization by the ADC is imported into the computer. The computer runs a distance difference calculation digital signal processing algorithm to digitally demodulate the pulse compressed signals after down-conversion from the two receivers.

[0042] The distance difference calculation digital signal processing algorithm of the present invention applies the above-mentioned distance difference measurement system, and the distance difference calculation digital signal processing algorithm includes:

[0043] Half-wave rectification algorithm is used to extract the positive half-cycle (positive polarity) waveform of the pulse envelope of a pulse compression signal;

[0044] The low-pass filtering algorithm filters out the carrier signal, further improving the signal-to-noise ratio and extracting the envelope of the pulse signal;

[0045] Matched filtering algorithm is used to calculate the phase difference between the signals received by two receivers;

[0046] The distance difference calculation algorithm is used to calculate the distance difference between two receivers and transmitters.

[0047] The distance difference calculation digital signal processing algorithm, wherein the half-wave rectification algorithm only retains the portion of the waveform amplitude greater than 0, and sets the portion less than 0 to 0.

[0048] The distance difference calculation digital signal processing algorithm includes a low-pass filtering algorithm: the processing result of the half-wave rectification algorithm is filtered by a digital low-pass filter to remove the carrier signal, further improving the signal-to-noise ratio and extracting the envelope of the pulse signal. The cutoff frequency of the digital low-pass filter is set to the frequency of the pulse envelope signal, which is the frequency of the periodic pulse wave signal generated by the low-frequency signal source.

[0049] The matched filtering algorithm, the cross-correlation function R xy (m), specifically:

[0050]

[0051] In the above formula, x(n) represents the waveform signal data sequence output by receiver 1, y(n) represents the waveform data sequence output by receiver 2, and m represents the number of points that the sequence y(n) is shifted during the operation.

[0052] Let f be the pulse envelope frequency of the pulse compression signal generated by the transmitter, in Hz; let f be the phase difference between the signals received by the two receivers. The unit is radians; the propagation speed of electromagnetic wave signals is the speed of light c, with units of m / s. Therefore, the formula for calculating the distance difference is:

[0053]

[0054] Equation (1) describes the phase difference between the signals received by the two receivers. The calculation formula is:

[0055]

[0056] Among them, f s is the sampling frequency of the oscilloscope's ADC, in Hz; f is the pulse envelope frequency of the pulse compression signal, in Hz; m is the number of sampling points offset from the origin by the main peak point of the cross-correlation function; c is the speed of light, the speed of signal propagation, in m / s.

[0057] This invention relates to a digital signal processing algorithm for distance difference calculation:

[0058] Half-wave rectification algorithm: Only the portion of the signal waveform with amplitude greater than 0 is retained, while the portion less than 0 is set to 0. The phase difference between the output signals of the two receivers after down-conversion is represented as the phase difference of the pulse envelope signal on the pulse compression signal waveform. The pulse envelope signal is the periodic waveform of the periodic pulse wave signal generated by the low-frequency signal source. Before performing cross-correlation calculations on the two pulse compression signals, noise on the pulse envelope can be filtered out as much as possible, effectively extracting the envelope signal and improving the accuracy of distance difference measurement.

[0059] Specifically, for the down-converted pulse compression signals output by the two receivers, after sampling and storage by the high-speed ADC of the oscilloscope, and importing the two waveform data sequences into the computer, the distance difference calculation digital signal processing algorithm of this invention first performs a half-wave rectification algorithm to convert the bipolar pulse envelope signal into a unipolar pulse envelope.

[0060] Low-pass filtering: The low-pass filtering algorithm is characterized by applying a digital low-pass filter to the processing result of the half-wave rectification algorithm. This filters out the carrier signal, further improving the signal-to-noise ratio and extracting the envelope of the pulse signal. The cutoff frequency of the digital low-pass filter is set to the frequency of the pulse envelope signal, which is the frequency of the periodic pulse wave signal generated by the low-frequency signal source.

[0061] In the circuit system, the receiver uses a mixer to downconvert the carrier of the received pulse compression signal, and at the same time uses a bandpass filter to extract the downconverted carrier signal, filter out the combined frequency components of other interference signals, reduce the equivalent noise bandwidth, and improve the signal-to-noise ratio. However, the noise superimposed on the envelope of the pulse compression signal still needs to be further filtered out.

[0062] Both receivers use identical digital low-pass filters, so the phase shift introduced by the filters is the same and will not affect the cross-correlation function calculation of the delay and distance difference between the two signals.

[0063] The commonly used design algorithms for digital filters have been published and are mature, and will not be described in detail in the technical solution of this invention.

[0064] Matched filtering algorithm: Since the pulse compressed signals received by both receivers originate from the same transmitter and have identical circuit structures, the waveform data sequences of the two signals after carrier down-conversion, analog-to-digital conversion, storage, and import into the computer exhibit strong correlation. The matched filtering algorithm performs cross-correlation calculations on the waveform data sequences output by the low-pass filtering algorithms of the two receivers. The cross-correlation function R... xy (m) can be represented as:

[0065]

[0066] In the above formula, x(n) represents the waveform signal data sequence output by receiver 1, y(n) represents the waveform data sequence output by receiver 2, and m represents the number of points that the sequence y(n) is shifted during the operation.

[0067] If there is no phase difference between the signals from the two receivers, then the cross-correlation function R xy The x-coordinate of the maximum point of (m) is m = 0; if there is a phase difference between the two signals, then the cross-correlation function R xy The maximum value of (m) will have its corresponding x-coordinate offset relative to zero, and the amount of offset is proportional to the phase difference. Meanwhile, if R... xy If the x-coordinate of the maximum point (m) is greater than 0, it means that the phase of x(n) lags behind that of y(n); if R xy If the x-coordinate m<0 at the maximum point, it means that x(n) leads y(n) in phase.

[0068] Distance difference calculation algorithm: Let the pulse envelope frequency of the pulse compression signal generated by the transmitter be f, in Hz; the phase difference between the signals received by the two receivers is... The unit is radians; the propagation speed of electromagnetic wave signals is the speed of light c, with units of m / s. Therefore, the formula for calculating the distance difference is:

[0069]

[0070] It is particularly important to note that because the pulse envelope of the pulse compression signal transmitted by the transmitter is periodic, when the phase delay between the output signals of the two receivers after down-conversion exceeds 180° (i.e., the time delay between the two received signals reaches more than half of 1 / f), it will be impossible to determine and distinguish the relative time delay and lead of the output signals of the two receivers. Here, 1 / f represents the period of the periodic pulse wave signal generated by the low-frequency signal source of the transmitter. Furthermore, if the phase difference between the two received signals is as high as an integer multiple of 1 / f, the cross-correlation function R... xy The maximum phase offset between the maximum point of (m) and the origin will not exceed one 1 / f period. At this time, the time difference converted by the phase offset between the main peak point of the cross-correlation function and the origin will be much smaller than the actual time difference.

[0071] Therefore, the upper limit of the distance difference measurement scheme proposed in this invention is determined by the pulse envelope period of the pulse compression signal. In practical applications of distance difference measurement, the time delay of the pulse compression signal output by the two receivers after carrier down-conversion needs to meet the condition that the time delay is less than half of the pulse envelope period. This is shown in the following equation:

[0072]

[0073] The phase difference between the signals received by the two receivers as described in equation (6) The calculation formula is:

[0074]

[0075] Among them, f s is the sampling frequency of the oscilloscope's ADC, in Hz; f is the pulse envelope frequency of the pulse compression signal, in Hz; m is the number of sampling points offset from the origin by the main peak point of the cross-correlation function; c is the speed of light, the speed of signal propagation, in m / s.

[0076] The theoretical maximum resolvable distance of this invention is determined by the maximum sampling frequency of the oscilloscope. The theoretical maximum resolvable distance is equal to the speed of light multiplied by the maximum sampling rate frequency.

[0077] Beneficial effects:

[0078] 1. The transmitter has relatively low power and a low carrier frequency, allowing the use of mature components and chips to construct the transmitter circuit, thus reducing the system cost.

[0079] 2. The transmitter and receiver systems use pulse compression signals for communication, which saves transmission power, improves the signal-to-noise ratio, and enhances the receiver's sensitivity and anti-interference capabilities.

[0080] 3. A high-speed digital oscilloscope can be used directly at the receiver end for sampling and storage, and the sampled signal can be directly imported into a computer for digital signal processing, which simplifies the complexity of the receiver system and reduces system costs.

[0081] 4. In the digital signal processing algorithm for distance difference calculation, the signal-to-noise ratio and the measurement accuracy of distance difference can be effectively improved by preprocessing through half-wave rectification and digital low-pass filtering.

[0082] 5. During the demodulation process of the receiver, specifically in the digital signal processing algorithm for distance difference calculation, a digital matched filtering algorithm (for calculating the cross-correlation function) is employed. This enables the distance difference measurement system to perform measurements under low signal-to-noise ratio conditions, effectively improving the receiver's sensitivity and distance difference measurement accuracy. For an oscilloscope with a sampling rate of 5 GSa / s, the theoretical maximum accuracy can reach 0.12 meters.

[0083] 6. The communication band frequency used in this distance difference measurement system is moderate, and the component cost is significantly lower than that used in high-frequency radar communication systems. The transmitter and receiver hardware circuits of this system are completely modular, and the real-time digital oscilloscope, as the core device for pulse compression signal demodulation, has good scalability, making it easy to maintain and upgrade the system. Attached Figure Description

[0084] Figure 1 This is a block diagram of a radio frequency communication band transmitter.

[0085] Figure 2 This is a block diagram of a radio frequency communication band receiver.

[0086] Figure 3 This is a schematic diagram of a distance difference measurement implementation case.

[0087] Figure 4 It is the waveform of the carrier down-conversion pulse compression signal from the two receivers, acquired by an oscilloscope.

[0088] Figure 5 It is the waveform of the output signals from the two receivers after half-wave rectification and digital low-pass filtering.

[0089] Figure 6 It is the waveform of the cross-correlation function of two digital sequences. Detailed Implementation

[0090] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0091] transmitter such as Figure 1 The radio frequency communication band transmitter includes:

[0092] Radio frequency signal source, outputting a single-frequency sine wave signal or a linear sweep frequency signal in the radio frequency band;

[0093] A low-frequency signal source that outputs a unipolar periodic pulse wave signal;

[0094] The high-speed electronic switch enables pulse shaping by multiplying two signals.

[0095] Radio frequency power amplifiers effectively improve the power of pulse compression signals output by transmitters;

[0096] Logarithmic antennas are used to transmit radio frequency signals.

[0097] A further design feature of the radio frequency communication band transmitter is that the radio frequency signal source is constructed using an LMX2571 phase-locked loop module, with an output signal frequency adjustable between 1 GHz and 1.5 GHz and an output signal power adjustable between -40 dBm and 0 dBm. Specifically, the output signal of the radio frequency signal source can be a single-frequency sine wave signal or a linearly swept frequency signal.

[0098] The radio frequency signal source outputs a carrier signal that generates a pulse compression signal. This frequency band avoids commonly used mobile communication frequency bands, resulting in relatively low electromagnetic interference in the environment. At the same time, devices in this frequency band are relatively mature, commonly available in the market, and have advantages such as low attenuation and low cost.

[0099] A further design of the radio frequency communication band transmitter is that the low-frequency signal source is made using a DDS9958 signal source module, which can output a periodic pulse wave signal. The pulse wave is unipolar, with a high level of 5 volts and a low level of zero. The frequency is continuously adjustable between 1 kHz and 100 kHz, the duty cycle is continuously adjustable between 0 and 100%, and the output signal amplitude is continuously adjustable between 0 and 5 volts.

[0100] The periodic low-frequency pulse signal generated by the low-frequency signal source and the radio frequency carrier signal are directly multiplied by a high-speed switching circuit to generate a pulse compression signal with a certain pulse width. The high-level width of the low-frequency pulse signal determines the time domain width of the pulse compression signal.

[0101] A further design feature of the radio frequency communication band transmitter is that the high-speed electronic switch is made using an HMC270 electronic switch, which must support a switching rate of at least 100kHz, and the frequency range of the input signal channel must cover the 1GHz to 1.5GHz band. The high-speed electronic switch enables pulse shaping by multiplying two signals. Compared to pulse shaping using analog multipliers or mixers, the pulse signal shaped by the high-speed electronic switch has steeper edges, less radio frequency carrier signal distortion, and a lower noise floor.

[0102] A further design feature of the radio frequency communication band transmitter is that the radio frequency power amplifier operates linearly in the range of 1 GHz to 1.5 GHz, with a power gain greater than 20 dB. The radio frequency power amplifier can effectively improve the power of the pulse compression signal output by the transmitter, thereby improving the performance indicators of the pulse compression signal transmission and reception system, such as operating distance, ranging accuracy, and positioning accuracy.

[0103] A further design of the radio frequency communication band transmitter is that the logarithmic antenna operates in the frequency band of 1GHz-1.5GHz, has an antenna gain of 12-18dB, can be omnidirectional or directional in radiation direction, and has an antenna standing wave ratio of less than or equal to 1.5.

[0104] Both the radio frequency (RF) and low-frequency (LFM) signal sources are input to a high-speed electronic switch, then mixed and amplified by an RF power amplifier before being transmitted by a logarithmic antenna.

[0105] Receiver, such as Figure 2 The radio frequency communication band receiver includes:

[0106] Log-numerical antennas are used to receive radio frequency signals;

[0107] Low-noise amplifiers improve the signal-to-noise ratio of input signals and suppress noise in input signals;

[0108] A passive mixer down-converts the input signal using the local oscillator signal;

[0109] The local oscillator signal source generates a standard sinusoidal local oscillator signal with a fixed frequency and amplitude.

[0110] Passive bandpass filters, used as intermediate frequency filters in receivers, can effectively reduce the equivalent noise bandwidth.

[0111] Intermediate frequency amplifier (IF amplifier) ​​amplifies the intermediate frequency signal, improving the receiver's sensitivity and dynamic range.

[0112] An oscilloscope or computer is used to acquire waveform signals and calculate the distance difference. The logarithmic antenna is connected in sequence to a low-noise amplifier, a passive mixer, a passive bandpass filter, an intermediate frequency amplifier, and an oscilloscope or computer for acquiring waveform signals and calculating the distance difference. The output of the local oscillator signal source is connected to the second input of the passive mixer.

[0113] A further design feature of the radio frequency communication band receiver is that the input and output impedances of each module are both 50 ohms, and each module is connected to the other using coaxial cables; each module is grounded at a single point using a 0-ohm resistor.

[0114] A further design of the radio frequency communication band receiver is that the logarithmic antenna operates in the frequency band of 1GHz-1.5GHz, has an antenna gain of 12-18dB, an antenna VSWR of less than or equal to 1.5, and is vertically polarized.

[0115] A further design feature of the radio frequency communication band receiver is that the low-noise amplifier is made using an SPF5043Z amplifier module, operating in the 1GHz to 1.5GHz frequency band, with an input noise voltage less than [missing information]. The noise figure is less than 1dB, and the amplifier gain is greater than 10dB. Using a low-noise-figure RF low-noise amplifier in the receiver preamplifier stage can effectively improve the receiver's sensitivity.

[0116] A further design feature of the radio frequency communication band receiver is that the passive mixer is made using a Minicircuits RMS-11X+ mixer, with an operating frequency range covering the 1GHz to 1.5GHz band and a typical conversion loss of less than 7dB.

[0117] In embodiments of the present invention, the passive mixer uses a diode passive mixer, which can achieve a larger dynamic range of the input signal, a lower noise figure, and less combination frequency components and interference at the output, thus improving the sensitivity of the receiver. The passive mixer performs down-conversion, shifting the carrier frequency of the input pulse compression signal from the 1GHz to 1.5GHz frequency range to a frequency range of 90MHz-110MHz centered at 100MHz.

[0118] A further design of the radio frequency communication band receiver is that the passive mixer performs down-conversion, shifting the carrier frequency of the input pulse compression signal from the 1GHz to 1.5GHz frequency range to a frequency range of 90MHz-110MHz centered at 100MHz.

[0119] A further design of the radio frequency communication band receiver is that the intrinsic signal source is made using an LMX2571 phase-locked loop, the frequency of the output sine wave signal is continuously adjustable in the range of 900MHz to 1.4GHz, and the output signal power is continuously adjustable in the range of -40dBm to 10dBm.

[0120] A further design of the radio frequency communication band receiver is that the passive bandpass filter is made using a simple RLC circuit, with a -3dB passband of 90MHz to 110MHz and an in-band insertion loss of less than 1dB.

[0121] A further design feature of the radio frequency communication band receiver is that the intermediate frequency amplifier is constructed using an ADL5330 controllable gain amplifier circuit module, with an operating frequency range covering 100MHz and a gain greater than 20dB. Increasing the gain of the intermediate frequency amplifier helps to improve the receiver's sensitivity.

[0122] A further design of the radio frequency communication band receiver involves using an oscilloscope for high-speed sampling of the down-converted pulse compression signal from the receiver. The oscilloscope is set to deep storage mode, and its real-time sampling rate is guaranteed to be greater than or equal to 500MHz (oscilloscope recording time = maximum storage depth divided by real-time sampling frequency). The oscilloscope's high-speed ADC performs analog-to-digital conversion on the waveform of the pulse compression signal and stores it. Simultaneously, the stored waveform data file is imported into a computer. The computer is used to run a distance difference calculation digital signal processing algorithm to digitally demodulate the down-converted pulse compression signal from the receiver.

[0123] In this technology, the distance difference is defined as the difference between the distance from a transmitter to receiver 1 and the distance from receiver 2.

[0124] like Figure 3 As shown, the distance difference measurement system consists of one transmitter and two receivers: receiver 1 and receiver 2. A is the distance from transmitter to receiver 1, B is the distance from transmitter to receiver 2, and C is the distance between receiver 1 and receiver 2. This invention's distance difference measurement system can measure the difference d between the distance from transmitter to receiver 1 and the distance from transmitter to receiver 2, that is:

[0125] d=|AB| (9)

[0126] d represents the distance difference measured by the distance difference measurement system of this invention.

[0127] exist Figure 3 In the diagram, receiver 1 and receiver 2 are in fixed positions, and the distance C between them is a known constant.

[0128] The transmitter system mentioned in this invention transmits a pulse compressed signal, and the receiver system mentioned in this invention simultaneously receives the pulse compressed signal. After the receiver completes the pre-amplification, down-conversion, filtering, and intermediate frequency amplification of the signal, it uses an oscilloscope to sample and store the pulse compressed signal waveform at high speed in real time. At the same time, the waveform data after sampling and quantization by the ADC is imported into the computer. The computer runs a distance difference calculation digital signal processing algorithm to digitally demodulate the pulse compressed signals after down-conversion from the two receivers.

[0129] The digital signal processing algorithm for distance difference calculation in this invention is described below:

[0130] The digital signal processing algorithm for distance difference calculation consists of the following four parts: 1) half-wave rectification algorithm, 2) low-pass filtering algorithm, 3) matched filtering algorithm, and 4) distance difference calculation algorithm.

[0131] Half-wave rectification algorithm:

[0132] The half-wave rectification algorithm is characterized by retaining only the portion of the signal waveform with amplitude greater than 0, and setting the portion less than 0 to 0. The phase difference between the output signals of the two receivers after down-conversion is represented on the pulse compression signal waveform as the phase difference of the pulse envelope signal, which is the periodic waveform of a periodic pulse wave signal generated by a low-frequency signal source. Before performing cross-correlation calculations on the two pulse compression signals, noise on the pulse envelope can be filtered out as much as possible, effectively extracting the envelope signal and improving the accuracy of distance difference measurement.

[0133] Specifically, for the down-converted pulse compression signals output by the two receivers, after sampling and storage by the high-speed ADC of the oscilloscope, and importing the two waveform data sequences into the computer, the distance difference calculation digital signal processing algorithm of this invention first performs a half-wave rectification algorithm to convert the bipolar pulse envelope signal into a unipolar pulse envelope.

[0134] Low-pass filter:

[0135] The low-pass filtering algorithm is characterized by applying a digital low-pass filter to the processing result of the half-wave rectification algorithm. This filters out the carrier signal, further improving the signal-to-noise ratio and extracting the envelope of the pulse signal. The cutoff frequency of the digital low-pass filter is set to the frequency of the pulse envelope signal, which is the frequency of the periodic pulse wave signal generated by the low-frequency signal source.

[0136] In the circuit system, the receiver uses a mixer to downconvert the carrier of the received pulse compression signal, and at the same time uses a bandpass filter to extract the downconverted carrier signal, filter out the combined frequency components of other interference signals, reduce the equivalent noise bandwidth, and improve the signal-to-noise ratio. However, the noise superimposed on the envelope of the pulse compression signal still needs to be further filtered out.

[0137] Both receivers use identical digital low-pass filters, so the phase shift introduced by the filters is the same and will not affect the cross-correlation function calculation of the delay and distance difference between the two signals.

[0138] The commonly used design algorithms for digital filters have been published and are mature, and will not be described in detail in the technical solution of this invention.

[0139] Matched filtering algorithm: Since the pulse compressed signals received by both receivers originate from the same transmitter and have identical circuit structures, the waveform data sequences of the two signals after carrier down-conversion, analog-to-digital conversion, storage, and import into the computer exhibit strong correlation. The matched filtering algorithm performs cross-correlation calculations on the waveform data sequences output by the low-pass filtering algorithms of the two receivers. The cross-correlation function R... xy (m) can be represented as:

[0140]

[0141] In the above formula, x(n) represents the waveform signal data sequence output by receiver 1, y(n) represents the waveform data sequence output by receiver 2, and m represents the number of points that the sequence y(n) is shifted during the operation.

[0142] If there is no phase difference between the signals from the two receivers, then the cross-correlation function R xy The x-coordinate of the maximum point of (m) is m = 0; if there is a phase difference between the two signals, then the cross-correlation function R xy The maximum value of (m) will have its corresponding x-coordinate offset relative to zero, and the amount of offset is proportional to the phase difference. Meanwhile, if R... xy If the x-coordinate of the maximum point (m) is greater than 0, it means that the phase of x(n) lags behind that of y(n); if R xy If the x-coordinate m<0 at the maximum point, it means that x(n) leads y(n) in phase.

[0143] Distance difference calculation algorithm:

[0144] Let f be the pulse envelope frequency of the pulse compression signal generated by the transmitter, in Hertz; let f be the phase difference between the signals received by the two receivers. The unit is radians; the propagation speed of electromagnetic wave signals is the speed of light c, with units of m / s. Therefore, the formula for calculating the distance difference is:

[0145]

[0146] It is particularly important to note that because the pulse envelope of the pulse compression signal transmitted by the transmitter is periodic, when the phase delay between the output signals of the two receivers after down-conversion exceeds 180° (i.e., the time delay between the two received signals reaches more than half of 1 / f), it will be impossible to determine and distinguish the relative time delay and lead of the output signals of the two receivers. Here, 1 / f represents the period of the periodic pulse wave signal generated by the low-frequency signal source of the transmitter. Furthermore, if the phase difference between the two received signals is as high as an integer multiple of 1 / f, the cross-correlation function R... xy The maximum phase offset between the maximum point of (m) and the origin will not exceed one 1 / f period. At this time, the time difference converted by the phase offset between the main peak point of the cross-correlation function and the origin will be much smaller than the actual time difference.

[0147] Therefore, the upper limit of the distance difference measurement scheme proposed in this invention is determined by the pulse envelope period of the pulse compression signal. In practical applications of distance difference measurement, the time delay of the pulse compression signal output by the two receivers after carrier down-conversion needs to meet the condition that the time delay is less than half of the pulse envelope period. This is shown in the following equation:

[0148]

[0149] The phase difference between the signals received by the two receivers as described in Equation 11 The calculation formula is:

[0150]

[0151] Among them, f s is the sampling frequency of the oscilloscope's ADC, in Hz; f is the pulse envelope frequency of the pulse compression signal, in Hz; m is the number of sampling points offset from the origin by the main peak point of the cross-correlation function; c is the speed of light, the speed of signal propagation, in m / s.

[0152] In some embodiments of the present invention, such as Figure 3 A transmitter and two receivers are installed at the location shown, forming a right triangle. The distance between transmitter and receiver 1 is A = 15 meters, the distance between transmitter and receiver 2 is B = 25 meters, and the distance between receiver 1 and receiver 2 is C = 20 meters.

[0153] In some embodiments of the present invention, in the transmitter, a radio frequency signal source outputs a signal with a frequency of 1.2 GHz as the carrier signal, with an output power of -20 dBm. A low-frequency signal source outputs a square wave signal with a duty cycle of 50%, an amplitude of 5V, and a frequency of 50 kHz. The periodic low-frequency pulse signal generated by the low-frequency signal source and the carrier signal generated by the radio frequency signal source are directly multiplied by a high-speed switching circuit to generate a pulse compression signal with a certain pulse width.

[0154] In some embodiments of the present invention, the logarithmic antennas used by both the transmitter and receiver operate in the frequency band of 1GHz-1.5GHz, have an antenna gain of 15dB, an antenna VSWR of less than or equal to 1.5, and are vertically polarized. The transmitter antenna has an omnidirectional radiation direction, while the receiver antenna has a directional radiation direction.

[0155] In some embodiments of the present invention, the gain of the preamplifier low-noise amplifier in both receivers is 10 dB. The intrinsic signal source output frequency is 1.3 GHz, and the output power is 0 dBm.

[0156] In some embodiments of the present invention, the passive mixer used in the receiver is a diode passive mixer with an operating frequency range of 200MHz to 3GHz and a typical conversion loss of 4.5dB.

[0157] In some embodiments of the present invention, the carrier frequency of the pulse compression signal after mixing in the receiver is 100MHz.

[0158] In some embodiments of the present invention, the intermediate frequency amplifier uses the ADL5330 controllable gain amplifier circuit module with a gain set to 20dB.

[0159] In some embodiments of the present invention, a high-speed real-time digital oscilloscope with a bandwidth of 1 GHz and a maximum sampling rate of 5 GHz is used to sample the pulse compression signal after the carrier sideband output of the two receivers (the output signals of the two receivers are sampled synchronously using the dual channels of the oscilloscope).

[0160] In some embodiments of the present invention, the oscilloscope is set to store a total sampling time of 100µs. The pulse compression signal waveform digital sequences sampled and stored by the oscilloscope and imported into the computer from the two receivers each contain 20,000 points.

[0161] In some embodiments of the present invention, by combining the total sampling time and the number of sampling points stored in the oscilloscope settings, the actual sampling frequency can be determined to be 200 MSa / s, resulting in a resolution of 1.5 meters. During implementation, the real-time resolution can be improved by increasing the actual sampling frequency.

[0162] In some embodiments of the present invention, the carrier down-converted pulse compression signals output by the two receivers are sampled and stored by an oscilloscope and then converted into two digital sequences, which are then imported into a computer for digital signal processing.

[0163] In some embodiments of the present invention, during digital signal processing, the signal sampled by the oscilloscope is half-wave rectified and then subjected to a 50kHz low-pass digital filter to extract the envelope of the pulse compression signal. Subsequently, digital cross-correlation is performed on the envelope signals of the two receivers, and the number of sampling points offset from the origin relative to the main peak value of the cross-correlation function is read. The distance difference between the transmitter and the two receivers can be calculated using the aforementioned calculation formulas (11) and (13).

[0164] In some embodiments of the present invention, the waveform of the carrier down-conversion pulse compression signal output by the two receivers is acquired by a dual-channel oscilloscope as shown in the figure. Figure 4 As shown.

[0165] In some embodiments of the present invention, the oscilloscope simultaneously samples and stores the data through two channels, converting it into two digital sequences. These two digital sequences are then imported into a computer for half-wave rectification, and after passing through a digital low-pass filter with a cutoff frequency of 50kHz, the resulting waveform is as follows: Figure 5 As shown.

[0166] In some embodiments of the present invention, after the two digital sequences undergo the above-described digital signal processing steps, the cross-correlation function waveforms of the two digital sequences are finally calculated as follows: Figure 6 As shown.

[0167] In some embodiments of the present invention, it can be seen from the waveform of the cross-correlation function that the main peak of the cross-correlation function is offset from the origin by 7 points. Substituting this into the aforementioned distance difference calculation formula, the distance difference between the transmitter and the two receivers is 10.5 meters, with an error of 0.5 meters from the actual value.

Claims

1. A radio frequency communication band range difference measurement system based on pulse compression technique, characterized by, The transmitter includes the following in sequence: RF signal source, outputting a single-frequency sinusoidal wave signal or a linear sweep signal in the RF band; Low-frequency signal source, outputting a single-polarity periodic pulse signal; High-speed electronic switch, realizing the function of multiplying two signals, i.e. pulse shaping; RF power amplifier, effectively improving the power of the pulse compression signal output by the transmitter; Logarithmic antenna, used for transmitting RF signals; The RF signal source and the low-frequency signal source are both input to the high-speed electronic switch, and then the mixed and amplified signals are transmitted by the logarithmic antenna; The output signal frequency of the RF signal source is adjustable between 1 GHz and 1.5 GHz, and the output signal power is adjustable between -40 dBm and 0 dBm; the RF signal source output signal can be a single-frequency sinusoidal wave signal or a linear sweep signal; the RF signal source outputs a carrier signal for generating a pulse compression signal; The low-frequency signal source outputs a periodic pulse signal, which is a single-polarity signal with a high level of 5 volts and a low level of zero; the frequency is continuously adjustable between 1 kHz and 100 kHz; the duty cycle is continuously adjustable between 0 and 100%; the output signal amplitude is continuously adjustable between 0 and 5 volts; The high-speed electronic switch needs to support a switching rate of at least 100 kHz, and the frequency range of the input signal channel needs to include the 1 GHz to 1.5 GHz frequency band; the high-speed electronic switch realizes the function of multiplying two signals, i.e. pulse shaping; The linear operating frequency range of the RF power amplifier includes 1 GHz to 1.5 GHz, and the power gain is greater than 20 dB; The operating frequency range of the logarithmic antenna includes 1 GHz-1.5 GHz, the antenna gain is 12-18 dB, the radiation direction is omnidirectional or directional, and the antenna standing wave ratio is less than or equal to 1.5; The receiver includes the following in sequence: Logarithmic antenna, used for receiving RF signals; Low-noise amplifier, improving the signal-to-noise ratio of the input signal and suppressing the noise of the input signal; Passive mixer, down-converting the input signal by using a local oscillator signal; Local oscillator signal source, generating a standard sinusoidal wave local oscillator signal with fixed frequency and amplitude; Passive band-pass filter, used as an intermediate frequency filter of the receiver, which can effectively reduce the equivalent noise bandwidth; Intermediate frequency amplifier, amplifying the intermediate frequency signal to improve the sensitivity and dynamic range of the receiver; Oscilloscope, used for collecting waveform signals and calculating distance differences; The input impedance and output impedance of each module are both 50 ohms, and coaxial lines are used to connect the modules; each module is grounded through a 0-ohm resistor; The logarithmic antenna is sequentially connected to the low-noise amplifier, passive mixer, passive band-pass filter, intermediate frequency amplifier, and oscilloscope or computer for collecting waveform signals and calculating distance differences; the output end of the local oscillator signal source is connected to the second input end of the passive mixer; The logarithmic antenna is a directional antenna, the operating frequency range includes 1 GHz-1.5 GHz, the antenna gain is 12-18 dB, the antenna standing wave ratio is less than or equal to 1.5, and the polarization direction is vertical polarization; The operating frequency range of the low-noise amplifier includes the 1 GHz to 1.5 GHz frequency band, the noise coefficient is less than 1 dB, and the amplifier gain is greater than 10 dB; The passive mixer has a working frequency range of 1-1.5 GHz, and a typical conversion loss of less than 7 dB; the passive mixer realizes frequency down-conversion, and moves the carrier frequency of the input pulse compression signal from the frequency range of 1-1.5 GHz to a frequency range of 90-110 MHz with 100 MHz as the center; The local oscillator signal source outputs a sinusoidal signal with a frequency continuously adjustable in the range of 900-1.4 GHz, and the output signal power is continuously adjustable in the range of -40-10 dBm; The passive bandpass filter has a -3 dB passband of 90-110 MHz, and an in-band insertion loss of less than 1 dB; The intermediate frequency amplifier has a working frequency range containing 100 MHz, and a gain greater than 20 dB; The oscilloscope is used for high-speed sampling of the pulse compression signal after frequency down-conversion of the receiver, wherein the oscilloscope is set to a deep storage mode, and the real-time sampling rate of the oscilloscope is greater than or equal to 500 MHz; the waveform of the pulse compression signal is converted into a digital signal by using the high-speed ADC of the oscilloscope and stored, and the stored waveform data file is imported into a computer.

2. A digital signal processing method for distance difference calculation in a radio frequency communication band range difference measurement system according to claim 1, characterized by: The distance difference measurement system comprises a transmitter and two receivers, i.e., a first receiver and a second receiver; A is the distance from the transmitter to the first receiver, B is the distance from the transmitter to the second receiver, and C is the distance between the first receiver and the second receiver; the difference d between the distance from the transmitter to the first receiver and the distance from the transmitter to the second receiver is measured, i.e., d=|A-B| (1); d is the distance difference measured by the distance difference measurement system. The radio frequency communication waveband receiver performs distance difference calculation, and the digital signal processing algorithm comprises: a half-wave rectification algorithm for extracting a positive half-wave of a pulse envelope of the pulse compression signal, i.e., a positive polarity waveform; a low-pass filtering algorithm for filtering out a carrier signal, further improving a signal-to-noise ratio, and extracting an envelope of a pulse signal; a matched filtering algorithm for calculating a phase difference between signals received by the two receivers; a distance difference calculation algorithm for calculating a distance difference between the two receivers and the transmitter; the half-wave rectification algorithm only retains a part with an amplitude greater than 0, and sets a part less than 0 to 0; the low-pass filtering algorithm: filtering the processing result of the half-wave rectification algorithm by using a digital low-pass filter, filtering out a carrier signal, improving a signal-to-noise ratio, and extracting an envelope of a pulse signal; the cut-off frequency of the digital low-pass filter is set as the frequency of the pulse envelope signal, and the frequency of the pulse envelope signal is the frequency of a periodic pulse wave signal generated by the low-frequency signal source; in the formula, x(n) represents a waveform signal data sequence output by the first receiver, y(n) represents a waveform data sequence output by the second receiver, and m represents the number of points by which the sequence y(n) is moved in the operation process; the distance difference calculation algorithm: assuming that the pulse envelope frequency of the pulse compression signal generated by the transmitter is f, the unit is Hz; the phase difference between the signals received by the two receivers is φ, the unit is radian; and the propagation speed of the electromagnetic wave signal is the speed of light c, the unit is m / s, the distance difference calculation formula is: The matching filter algorithm, the cross-correlation function R xy (m), specifically: （2） ​ ​ （3） The phase difference φ between the signals received by the two receivers is calculated according to the formula: （4） wherein, f s is the sampling frequency of the oscilloscope ADC, in Hz; f is the pulse envelope frequency of the pulse compression signal, in Hz; m is the sampling point number of the main peak of the cross-correlation function from the origin; c is the propagation speed of the signal, which is the speed of light, in m / s.

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