Self-adaptive high-dynamic spread spectrum tracking receiver

Abstract

A self-adaptive high-dynamic spread spectrum tracking receiver relates to the technical field of satellite communication and comprises an AGC loop, an A / D converter, a PN code capturing and tracking loop, a single carrier loop, a despreading device, a phase discriminator, a phase shift signal generator and a low-pass processor. The method comprises the following steps of: converting a signal into a digital signal, subsequently generating an output tracking signal through a PN code capturing and tracking loop, processing through a single carrier loop to obtain a captured tracking signal and an amplitude excitation signal, and finally carrying out de-spreading and phase discrimination to generate an azimuth error voltage signal and a pitching error voltage signal; the receiver can stably receive and process spread spectrum signals sent by a high-speed target.

Description

Technical Field

[0001] The utility model relates to the technical field of satellite communication, in particular to an adaptive high-dynamic spread-spectrum tracking receiver. Background Art

[0002] For spread-spectrum signals, generally, the PN code and demodulated data recovered and generated by a tracking receiver are used to perform correlation despreading and demodulation on the differential path signals, remove the influence of the diagonal error extraction of the spreading code and modulation data, obtain the maximum spreading gain, detect and recover the differential path signals, and multiply them with the phase-shifted low-frequency signals to detect the azimuth and elevation angle error information, so as to ensure better demodulation performance.

[0003] However, when the target moves at a high speed, its relative speed with respect to the tracking receiver changes very fast, which will result in a large Doppler frequency change rate. The Doppler frequency change rate refers to the change amount of the Doppler frequency per unit time.

[0004] The existing tracking receiver designs often have difficulty adapting to this extreme situation. Especially in the traditional AGC loop design, since the gain control is a multiplicative relationship and the essence of this AGC loop is non-linear, it is difficult to conduct a detailed theoretical design in terms of response speed and control accuracy. And because the control gain of a non-linear system does not linearly decrease as the controlled quantity approaches the expected value, there may be a large tracking error during the tracking stage.

[0005] That is, in a communication system, the strength of the actually received signal varies greatly. To ensure the normal progress of communication, a voltage signal is generated here to control the AGC. It is necessary to adjust the amplitude of the signal received by the receiver in real time, which should change with the signal strength, so that the amplitude of the signal received by the receiver is stabilized within the automatic gain control range. If this control voltage is not linear at this time, then this control voltage will not change linearly, which will lead to a large change in the amplitude of the signal received by the receiver and is very likely to exceed the automatic gain control range, resulting in the receiver losing lock.

[0006] In addition, a high-speed moving target will cause the signal strength to change rapidly, which poses a challenge to the AGC loop because the traditional AGC loop design may not be able to adjust the signal power quickly and accurately, thus affecting the tracking performance.

[0007] Therefore, we propose a tracking receiver that can stably receive and process the spread-spectrum signals emitted by high-speed targets. Summary of the Utility Model

[0008] In order to overcome the deficiencies in the background art, the utility model discloses an adaptive high-dynamic spread-spectrum tracking receiver.

[0009] To achieve the above-mentioned invention object, the utility model adopts the following technical solutions:

[0010] An adaptive high-dynamic spread-spectrum tracking receiver, comprising:

[0011] An AGC loop, configured to receive a spread-spectrum signal, and after processing in a linear manner, output a normalized signal and a gain control signal;

[0012] An A / D converter, configured to convert the normalized signal and the gain control signal into digital signals;

[0013] A PN code acquisition and tracking loop, including a PN code acquisition unit and a PN code tracking unit, wherein the PN code acquisition unit is configured to generate an acquisition relative position; the PN code tracking unit adopts a non-coherent delay-locked loop structure, and generates an output tracking signal according to the digital normalized signal and the acquisition relative position signal;

[0014] A single-carrier loop, configured to receive the gain control signal and the output tracking signal, and process to obtain the acquired tracking signal and an amplitude excitation signal, and the amplitude excitation signal is output to the AGC loop;

[0015] A despreader, configured to demodulate the acquired tracking signal;

[0016] A phase discriminator, configured to detect the phase error between the acquired tracking signal and the demodulated signal;

[0017] A phase shift signal generator, configured to generate three phase shift signals, wherein the first phase shift signal is synthesized with the spread-spectrum signal and then output to the AGC loop;

[0018] A low-pass processor, configured to receive the demodulated signal, the second phase shift signal, and the third phase shift signal, generate an azimuth error voltage signal by mixing and phase discriminating the demodulated signal and the second phase shift signal, and generate a pitch error voltage signal by mixing and phase discriminating the demodulated signal and the third phase shift signal.

[0019] Preferably, the AGC loop includes a synthesizer, a loop filter, an integration operator, a gain calculator, and a controllable amplifier, wherein the integration operator is configured to receive the amplitude excitation signal and the output signal of the loop filter, and the integrated result is respectively output to the synthesizer and the gain calculator;

[0020] The synthesizer is configured to synthesize the baseband signal in the spread-spectrum signal and the output signal of the integration operator to obtain an output signal as the spread-spectrum signal of the loop filter;

[0021] The gain calculator generates a gain control signal and a gain value signal according to the integration operation result and a threshold signal;

[0022] The controllable amplifier is used to amplify the spread spectrum signal and the gain value signal to generate a normalized signal.

[0023] Preferably, the baseband signal in the spread spectrum signal is output to the synthesizer through a diode.

[0024] Preferably, the single carrier loop is provided with a frequency guiding unit.

[0025] Preferably, the amplitude excitation signal is output to the AGC loop through the SPI interface.

[0026] Preferably, the spread spectrum signal includes a sum input signal and a difference input signal, where the sum input signal is an input signal of the synthesizer;

[0027] The first phase shift signal performs a phase shift process on the differential path signal through a phase shift modulator, and sends the processed differential signal to the other input end of the synthesizer.

[0028] Preferably, the output signal of the synthesizer is output to the AGC loop through down-conversion and a band-pass filter.

[0029] Due to the above-mentioned technical solution, the utility model has the following beneficial effects:

[0030] An adaptive high-dynamic spread spectrum tracking receiver disclosed by the utility model can realize high-precision normalization control of signal power by processing signals in a linear manner. At the same time, combined with a PN code acquisition and tracking loop, it can reduce the loop bandwidth to reduce the phase jitter of the loop, improve the ranging accuracy, and finally realize effective tracking and demodulation of high-dynamic targets. Especially when the Doppler frequency change rate of the target is relatively large, it can still maintain stable tracking performance. Description of the Drawings

[0031] Figure 1 is a structural schematic diagram of the utility model;

[0032] Figure 2 is a structural schematic diagram of the PN code acquisition and tracking loop;

[0033] Figure 3 is a structural schematic diagram of the AGC loop.

[0034] In the figure: 1. AGC loop; 2. A / D converter; 3. PN code acquisition unit; 4. PN code tracking unit; 5. Single carrier loop; 6. Despreader; 7. Phase discriminator; 8. Phase shift signal generator; 9. Low-pass processor. Detailed Embodiments

[0035] The technical solution of the present utility model will be described below in conjunction with the accompanying drawings in the embodiments of the present utility model. In the description, it should be understood that if there are terms such as "upper", "lower", "front", "rear", "left", "right", etc. indicating the orientation or positional relationship, they only correspond to the accompanying drawings of the present utility model. For the convenience of describing the present utility model, rather than indicating or implying that the device or element referred to must have a specific orientation:

[0036] Embodiment 1 is as follows:

[0037] Combined with the attached Figure 1 An adaptive high-dynamic spread-spectrum tracking receiver, comprising:

[0038] An AGC loop 1 for receiving a spread-spectrum signal and outputting a normalized signal and a gain control signal after processing in a linear manner. The process of processing the signal in a linear manner is as follows: using the "quantity" in the loop and the bandwidth parameter of the loop to track the amplitude of the input signal. After achieving amplitude tracking, the gain coefficient is obtained using the ratio of the obtained amplitude to the expected threshold, thereby realizing the normalization of the signal. This method solves the linear system problem of the AGC loop 1 and realizes the high-precision normalization control of the signal power;

[0039] An A / D converter 2 for converting the normalized signal and the gain control signal into digital signals, facilitating subsequent digital signal processing and improving the processing speed and accuracy;

[0040] A PN code acquisition and tracking loop, including a PN code acquisition unit 3 and a PN code tracking unit 4. The PN code acquisition unit 3 is used to generate an acquisition relative position; the PN code tracking unit 4 adopts a non-coherent delay-locked loop structure and generates an output tracking signal according to the digital normalized signal and the acquisition relative position signal;

[0041] The PN code acquisition unit 3 can quickly acquire the PN code in the normalized signal, improving the response speed of the system, and the non-coherent delay-locked loop (DLL) structure can effectively track the PN code phase change in the signal to ensure signal synchronization;

[0042] In addition, combined with Figure 2, the PN code tracking unit 4 includes a local PN code generator, a signal and local PN code correlator, early and late gate error extraction, loop filtering, a code clock DCO, a lock indication, etc.; the PN code tracking unit 4 uses a non-coherent delay locked loop, where the PN code locks the carrier first and then locks; for a multi-Δ loop, the capture range is wide and it is easy to lock; for a single-Δ loop, the phase jitter is small and the ranging accuracy is high. The timing error extraction uses the early and late gate discrimination method, where the error value is obtained by subtracting the late gate correlation value from the early gate correlation value, and then the DCO is adjusted through the loop filter to change the local code phase to complete the lock. Appropriately reducing the loop bandwidth can reduce the phase jitter of the loop. To provide high-precision distance data, a single-Δ loop is used. After the PN code tracking loop is locked, the lock indication reports to the monitoring software;

[0043] The pseudo-code loop bandwidth is adaptively processed according to the C / N0 setting, and the loop bandwidth is automatically set on the principle that the loop output meets the requirements of tracking and demodulation.

[0044] The single-carrier loop 5 is used to receive the gain control signal and output the tracking signal, and processes to obtain the captured tracking signal and the amplitude excitation signal, and the amplitude excitation signal is output to the AGC loop; by processing the gain control signal and the output tracking signal, the captured tracking signal is obtained to ensure that the system is in the phase-locked state. In addition, the captured tracking signal can also be used for feedback control to further optimize the performance of the system;

[0045] Specifically, the single-carrier loop 5 is provided with a frequency guiding unit, whose function is to help the single-carrier loop 5 acquire and track the frequency of the input signal, and the main purpose of frequency guiding is to find the correct frequency in the initial stage so that the subsequent demodulation process can proceed correctly;

[0046] In addition, the amplitude excitation signal is output to the AGC loop through the SPI interface. Since SPI does not require complex handshake signals, a relatively fast data transmission speed can be achieved, meeting the scenario of the spread spectrum signal of high-speed targets used by this receiver;

[0047] The despreader 6 is used to demodulate the captured tracking signal to recover the original data information;

[0048] The phase discriminator 7 is used to detect the phase error between the captured tracking signal and the demodulated signal, and provide necessary feedback information for the tracking receiver to adjust the signal phase;

[0049] The phase shift signal generator 8 is used to generate three phase shift signals, where the first phase shift signal is synthesized with the spread spectrum signal and then output to the AGC loop 1;

[0050] A low-pass processor 9, which is configured to receive a demodulated signal, a second phase-shifted signal, and a third phase-shifted signal, generate an azimuth error voltage signal by mixing and phase discrimination of the demodulated signal and the second phase-shifted signal, and generate an elevation error voltage signal by mixing and phase discrimination of the demodulated signal and the third phase-shifted signal;

[0051] It should be noted that after the captured tracking signal is despread and phase discriminated, it first passes through a low-pass filter to filter out high-frequency signals and then undergoes mixing and phase discrimination with the phase-shifted signal. After obtaining a signal containing angular error (azimuth / elevation) information, it is further filtered by a low-pass filter once.

[0052] Embodiment 2 is as follows:

[0053] On the basis of Embodiment 1, in combination with the attached Figure 3 , the AGC loop 1 is further defined, that is, the AGC loop 1 includes a synthesizer, a loop filter, an integral operator, a gain calculator, and a controllable amplifier. The integral operator is configured to receive an amplitude excitation signal and the output signal of the loop filter, and the results after integral operation are respectively output to the synthesizer and the gain calculator;

[0054] The synthesizer is configured to synthesize the baseband signal in the spread-spectrum signal and the output signal of the integral operator to obtain an output signal which is the spread-spectrum signal of the loop filter;

[0055] The gain calculator generates a gain control signal and a gain value signal according to the integral operation result and the threshold signal;

[0056] The controllable amplifier is configured to amplify the spread-spectrum signal and the gain value signal to generate a normalized signal;

[0057] In the structure of this AGC loop 1, an amplitude tracking technology is adopted, thereby completely solving the linear system problem of the AGC loop 1 and realizing high-precision normalization control of the signal power.

[0058] Specifically, the baseband signal in the spread-spectrum signal is output to the synthesizer through a diode; here, the diode has functions such as signal separation, reverse current prevention, signal shaping, and circuit protection.

[0059] In addition, the spread-spectrum signal includes a sum input signal and a difference input signal, where the sum input signal is an input signal of the synthesizer;

[0060] The first phase-shifted signal performs phase shift processing on the difference path signal through a phase shift modulator and sends the processed difference signal to the other input end of the synthesizer, that is, the difference signal is the other input signal of the synthesizer; among them, phase shift modulation is mainly used to generate a modulation signal, which contains useful information from the target and suppresses unwanted interference and noise at the same time.

[0061] As needed, the output signal of the synthesizer is output to the AGC loop 1 through downconversion and a band-pass filter; among them, downconversion converts a high-frequency input signal into a lower-frequency signal because high-frequency signals often require higher energy and larger bandwidth for transmission, and these characteristics may lead to a decline in signal quality and an increase in interference. Through downconversion, the signal can be converted to a more easily processed frequency range while reducing the requirements for hardware; downconversion usually includes two steps: mixing and low-pass filtering. The mixer multiplies the input signal by a local oscillator signal with a specific frequency, and then the unnecessary high-frequency components are removed through a low-pass filter, and the required low-frequency signal is retained;

[0062] The band-pass filter is a selective filter that only allows signals within a specific frequency range to pass through while blocking signals of other frequencies. In the spread-spectrum tracking unit 4, the role of the band-pass filter is to screen out the signal frequency band of interest and remove spurious signals and noise; the advantage of doing this is that it can improve the signal-to-noise ratio, reduce the complexity of subsequent processing, and ensure that only the target signal is focused on.

[0063] The parts not detailed in this utility model are prior art. For those skilled in the art, it is obvious that this utility model is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model; therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of this utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in this utility model, and any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. An adaptive high dynamic spread spectrum tracking receiver, characterized in that: include: An AGC loop (1) is used to receive a spread spectrum signal, process it in a linear manner, and output a normalized signal and a gain control signal; An A / D converter (2), used for converting the normalization signal and the gain control signal into a digital signal; The PN code capture and tracking loop comprises a PN code capture unit (3) and a PN code tracking unit (4), wherein the PN code capture unit (3) is used to generate a capture relative position; the PN code tracking unit (4) adopts a non-coherent delay locked loop structure and generates an output tracking signal according to a digital normalization signal and a capture relative position signal; The single carrier loop (5) is used for receiving the gain control signal and outputting the tracking signal, and processing to obtain the captured tracking signal and the amplitude excitation signal, and the amplitude excitation signal is output to the AGC loop; A despreader (6), used for demodulating the captured tracking signal; A phase detector (7) for detecting a phase error between a captured tracking signal and a demodulated signal; A phase shift signal generator (8) is used to generate three phase shift signals, wherein the first phase shift signal is synthesized with the spread spectrum signal and then output to the AGC loop (1); The low-pass processor (9) is used for receiving the demodulated signal, the second phase-shifted signal and the third phase-shifted signal, mixing and phase-locking the demodulated signal with the second phase-shifted signal to generate an azimuth error voltage signal, and mixing and phase-locking the demodulated signal with the third phase-shifted signal to generate a pitch error voltage signal.

2. The adaptive high dynamic spread spectrum tracking receiver as claimed in claim 1, characterized in that: The AGC loop (1) comprises a synthesizer, a loop filter, an integrator, a gain calculator and a controllable amplifier, wherein the integrator is used to receive the amplitude excitation signal and the output signal of the loop filter, and the result after the integration operation is output to the synthesizer and the gain calculator respectively; The synthesizer is used to synthesize the baseband signal in the spread spectrum signal and the output signal of the integral operator, and the obtained output signal is the spread spectrum signal of the loop filter; The gain calculator generates a gain control signal and a gain value signal according to the integral operation result and the threshold signal; The controllable amplifier is used to amplify the spread spectrum signal and the gain value signal to generate a normalized signal.

3. The adaptive high dynamic spread spectrum tracking receiver as claimed in claim 1, characterized in that: The single carrier loop (5) is provided with a frequency guiding unit.

4. The adaptive high dynamic spread spectrum tracking receiver as claimed in claim 1, characterized in that: The amplitude excitation signal is output to the AGC loop via the SPI interface.

5. The adaptive high dynamic spread spectrum tracking receiver as claimed in claim 2, characterized in that: The spread spectrum signal includes a sum input signal and a difference input signal, wherein the sum input signal is an input signal of the synthesizer; The first phase-shifted signal performs phase shift processing on the difference path signal through the phase-shift modulator, and the processed difference signal is sent to the other input end of the synthesizer.

6. The adaptive high dynamic spread spectrum tracking receiver as claimed in claim 5, characterized in that: The output signal of the synthesizer is output to the AGC loop (1) through down conversion and bandpass filtering.

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