CN110943949B - Broadband angle tracking method based on SC-FDE transmission system - Google Patents

Broadband angle tracking method based on SC-FDE transmission system Download PDF

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CN110943949B
CN110943949B CN201911165535.3A CN201911165535A CN110943949B CN 110943949 B CN110943949 B CN 110943949B CN 201911165535 A CN201911165535 A CN 201911165535A CN 110943949 B CN110943949 B CN 110943949B
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timing
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CN110943949A (en
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陈大海
杨大龙
谢顺钦
杜少轩
俞平原
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Institute of Electronic Engineering of CAEP
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Abstract

The invention discloses a broadband angle tracking method based on an SC-FDE transmission system, and relates to the field of radio communication. The invention outputs two paths of intermediate frequency signals after radio frequency sum signals and difference signals received by an antenna respectively pass through a signal conditioning circuit, wherein a difference channel does not carry out AGC closed-loop control, but directly uses AGC amplification of a sum channel to carry out channel gain control; respectively carrying out A/D sampling, digital preprocessing, signal synchronization and channel estimation on the two paths of output intermediate frequency signals; in the signal synchronization process, the difference channel does not carry out synchronization parameter estimation, but directly uses the synchronization information of the sum channel to carry out synchronization error correction; and further extracting azimuth and pitch angle error information according to channel estimation results of the sum channel and the difference channel, performing low-pass filtering respectively, and outputting the information to the ACU. The invention saves a special tracking receiver, does not need to provide special requirements for receiving antenna design, a servo unit processing algorithm, a plurality of receiving devices and the like, and is simple and practical.

Description

Broadband angle tracking method based on SC-FDE transmission system
Technical Field
The invention relates to the field of radio communication, in particular to a broadband angle tracking method based on an SC-FDE transmission system.
Background
When the radio measurement and control system tracks a low elevation angle target, due to multipath effects generated by reflection and refraction of a terrain environment, changes of received signals in amplitude and phase can be caused, so that the precision of the tracked target is reduced, and even the tracked target is lost, and therefore, the problem of low elevation angle tracking needs to be solved. How to reduce the influence of multipath effect on low-angle target tracking performance mainly includes methods of reducing antenna side lobes, diversity technology (polarization diversity, space diversity, frequency diversity and the like), data guidance (GPS information, radar height information, theoretical flight trajectory and the like), single-axis tracking, off-axis tracking, multi-information source fusion and the like. The above techniques all require a separate tracking receiver to extract the angular error information, and in addition, special requirements are put forward on the design of a receiving antenna, a servo unit processing algorithm, various external information sources, the number of receiving devices, and the like.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention provides a broadband angle tracking method based on an SC-FDE transmission system, and aims to solve the problems that an independent tracking receiver is required to extract angle error information and special requirements are provided for receiving antenna design, a servo unit processing algorithm, various external information sources, the number of receiving devices and the like in the prior art.
Orthogonal Frequency Division Multiplexing (OFDM) and Single Carrier Frequency Domain Equalization (SC-FDE) are two signal transmission systems that can effectively overcome multipath propagation. The OFDM system adopts a multi-carrier mode to divide a channel into a plurality of subchannels, and the channel of each channel is flat, so that the frequency selective fading problem is avoided. SC-FDE employs a similar architecture to OFDM, but compensates for the frequency selective channel mainly by frequency domain equalization. In addition, the SC-FDE system keeps the advantage of low peak-to-average power ratio of the traditional single carrier system and has better power utilization rate. The invention provides a demodulation and tracking integrated low elevation angle tracking method by utilizing an SC-FDE system to transmit broadband signals and combining the characteristics of the broadband signals, saves a special tracking receiver, does not need to provide special requirements for receiving antenna design, a servo unit processing algorithm, a plurality of receiving devices and the like, and is simple and practical.
In order to solve the problems in the prior art, the invention is realized by the following technical scheme:
a broadband angle tracking method based on an SC-FDE transmission system is characterized in that: the method comprises the following steps:
for radio frequency and signal RF received by antenna∑Difference signal RF△Outputs two paths of intermediate frequency signals IF after passing through signal conditioning circuits respectively∑And IF△Wherein, the difference channel does not carry out AGC closed-loop control, but directly uses AGC amplification of the sum channel to carry out channel gain control; to the output two intermediate frequency signals IF∑And IF△Respectively carrying out A/D sampling, digital preprocessing, signal synchronization and channel estimation; in the signal synchronization process, the difference channel does not carry out synchronization parameter estimation, but directly uses the synchronization information of the sum channel to carry out synchronization error correction; and further extracting azimuth and pitch angle error information according to channel estimation results of the sum channel and the difference channel, respectively performing low-pass filtering, and outputting the information to an antenna control unit.
Performing IDFT on the sum channel estimation result to obtain the sum channel impulse response estimation value IΣ(n),1≤n≤NUW，NUWRepresents the length of the UW sequence; the update rate is Rs/Nb，RsRepresenting the symbol rate, NbRepresenting the frame length; let the value with the maximum energy be IΣ(P) with the sequence number value P; correspondingly, the impulse response estimated value at the position P in the difference channel impulse estimation result is IΔ(p), the tracking angle error value is E ═ IΣ(p)×IΔ(p)*，(·)*The representation is taken as the conjugate, which corresponds in part to the azimuth error EA＝Real[IΣ(p)×IΔ(p)*]Imaginary part corresponding to pitch angle error EE＝Imag[IΣ(p)×IΔ(p)*]And then respectively provided to the antenna control unit after low-pass filtering.
The maximum energy is expressed as: max [ | IΣ(n)|2],1≤n≤NUWAnd | represents taking an absolute value.
The signal conditioning circuit mainly comprises a low noise amplifier module, an analog down-conversion module, a filtering module and an AGC amplification module.
The A/D sampling refers to the intermediate frequency receiving signal is subjected to the fixed sampling frequencySampling; the digital preprocessing specifically refers to preprocessing the digital signal after A/D sampling, mainly comprising a digital down-conversion module, a multistage filtering extraction module and a matched filtering module, and outputting 4 times of symbol rate R after preprocessingsBaseband I, Q signal; the multistage filtering extraction module realizes integral multiple extraction and fractional multiple extraction.
The signal synchronization specifically refers to performing synchronization processing on a baseband I, Q signal, including UW sequence synchronization, carrier synchronization and timing synchronization; firstly, realizing UW sequence synchronization according to the autocorrelation characteristic of the UW sequence, then realizing carrier synchronization through the UW sequence phase relationship of adjacent transmission frames, realizing timing frequency offset estimation through the frequency domain correlation of the UW sequence of the adjacent transmission frames, and then completing timing error correction through a complete timing loop; the carrier synchronization specifically refers to carrier frequency offset estimation and correction.
M frame transmitting signal s [ mN ]b+n]Expressed as:
Figure BDA0002287349530000031
wherein N isUWDenotes the length of the UW sequence, sUW[n]Represents a UW sequence;
the received signal after passing through the channel is represented as:
Figure BDA0002287349530000032
in the above formula, h (L) represents the channel impulse response with length L, x [ n ]]Representing the waveform of the transmitted signal, theta representing the timing offset present in the received signal, af representing the carrier frequency offset, fsRepresenting the signal sampling rate, ω n]Representing gaussian white noise.
The UW sequence synchronization first multiplies the received signal by the conjugate of the UW sequence and performs correlation accumulation, and then obtains the position d of the frame header by detecting the peak value of the accumulation result, as follows,
Figure BDA0002287349530000033
after the synchronous position of the UW sequence is obtained, the carrier synchronization is carried out through the phase relation between the front data block and the rear data block, the calculation is as follows,
Figure BDA0002287349530000034
under the condition that the sampling deviation theta of the front and the back data frames is approximately equal and the channel characteristics are approximately equal, the formula (2) is replaced by the formula (4), and phi (delta f) can be simplified into phi
Figure BDA0002287349530000035
Considering the transmitted data as uncorrelated with noise, the maximum likelihood of Δ f is estimated as
Figure BDA0002287349530000041
After the carrier synchronization is finished, only one timing deviation theta which changes slowly along with time exists in the received data, the time change rate of the received data can be estimated through the frequency domain correlation of the inter-frame UW sequence, and then the residual fixed timing deviation is compensated through a timing loop. Assuming that the data after carrier synchronization satisfies:
Figure BDA0002287349530000042
DFT (digital Fourier transform) conversion is carried out on the second UW sequence position in the two frames of data before and after the received data, wherein
Figure BDA0002287349530000043
Wherein the content of the first and second substances,
Figure BDA0002287349530000044
H[k]、XUW[k]and Ωn[k]Respectively represent
Figure BDA0002287349530000049
h (l), UW sequence and ω n]DFT of (2).
Carrying out conjugate multiplication on corresponding frequency points of two adjacent frames to obtain delta FθFunction Ψ (. DELTA.F) ofθAnd k) is:
Figure BDA0002287349530000045
then Δ FθThe maximum likelihood estimate of (c) is:
Figure BDA0002287349530000046
in order to simplify the calculation process, the more accurate delta F can be obtained by weighted average of the calculation results of a few frequency pointsθAnd (6) estimating the value. And feeding back the timing estimation result to a fractional filtering extraction module in digital preprocessing to form a complete timing synchronization loop so as to eliminate timing deviation.
Channel estimation: the SC-FDE transmission frame structure ensures that the received data satisfies the circular convolution characteristic, and may use fft (fast Fourier transform) to perform frequency domain fast processing, but before performing frequency domain equalization, the channel needs to be estimated first. After the carrier synchronization and the timing synchronization are completed, the DFT of the second UW sequence signal of the data frame satisfies the following conditions:
Figure BDA0002287349530000047
since the UW sequence satisfies the frequency domain constant amplitude characteristic, the estimate of H [ k ] can be expressed as:
Figure BDA0002287349530000048
wherein, omega'n[k]Represents omegan[k]·XUW *[k]。
SC-FDE equalization: after obtaining the channel estimation result of the length of the UW sequence, it is necessary to interpolate the channel estimation result to Nb-NUWWithin the data block. Frequency domain equalizer coefficient C [ k ] designed by MSE criterion]Satisfies the following conditions:
Figure BDA0002287349530000051
although it is used for
Figure BDA0002287349530000052
Already contains the noise energy part, but considering the existence of randomness, in order to suppress the amplification effect of noise under a deep fading channel, a constant term C corresponding to a predefined signal-to-noise ratio is introduced into a denominator, so that the equalizer coefficient can be expressed as:
Figure BDA0002287349530000053
the DFT of the received signal in the effective data region and the first UW sequence region is expressed as:
Figure BDA0002287349530000054
the equalizer processed signal X k can be expressed as:
Figure BDA0002287349530000055
wherein the content of the first and second substances,
Figure BDA0002287349530000056
and (3) demodulation output: to obtain
Figure BDA0002287349530000057
Then, the obtained product was obtained by IDFT (inverse Digital Fourier transform)
Figure BDA0002287349530000058
To obtain the estimated value of the original transmitting signal
Figure BDA0002287349530000059
The entire demodulation process is completed.
The method is suitable for wideband signals with symbol period TsThe minimum multipath time delay difference of the actual channel is smaller than the minimum multipath time delay difference of the actual channel, so that a main path signal and a multipath signal can be distinguished in a channel impulse response estimation result, and angle error information is extracted from the main path signal, therefore, the method is defined as a broadband angle tracking method based on an SC-FDE transmission system.
Compared with the prior art, the beneficial technical effects brought by the invention are as follows:
1. the signal processing method is adopted to realize effective extraction of the broadband angle error signal and inhibit the interference of multipath signals, and no special requirements are provided for the design of a receiving antenna, a servo unit processing algorithm, various external information sources, the number of receiving devices and the like, so that the realization method is simple and economic.
2. Because SC-FDE transmission can be combined with various modulation mode signals, and the synchronous processing is irrelevant to the specific modulation mode, the method is suitable for various modulation mode signals, such as PSK (Phase Shift keying), QAM (Quadrature Amplitude modulation), APSK (Amplitude Phase Shift keying) and other signals, and has good universality;
3. the SC-FDE demodulation and tracking function integration is realized, a special tracking receiver is omitted, and the equipment amount is saved.
Drawings
FIG. 1 is a diagram illustrating a SC-FDE transmission frame structure;
FIG. 2 is a schematic diagram of an SC-FDE demodulation architecture;
FIG. 3 is a block diagram of an SC-FDE broadband angular tracking system.
Detailed Description
The technical scheme of the invention is further elaborated in the following by combining the drawings in the specification.
Example 1
Referring to the accompanying fig. 3, this embodiment discloses:
a broadband angle tracking method based on an SC-FDE transmission system comprises the following steps:
for radio frequency and signal RF received by antenna∑Difference signal RF△Outputs two paths of intermediate frequency signals IF after passing through signal conditioning circuits respectively∑And IF△Wherein, the difference channel does not carry out AGC closed-loop control, but directly uses AGC amplification of the sum channel to carry out channel gain control; to the output two intermediate frequency signals IF∑And IF△Respectively carrying out A/D sampling, digital preprocessing, signal synchronization and channel estimation; in the signal synchronization process, the difference channel does not carry out synchronization parameter estimation, but directly uses the synchronization information of the sum channel to carry out synchronization error correction; and further extracting azimuth and pitch angle error information according to channel estimation results of the sum channel and the difference channel, respectively performing low-pass filtering, and outputting the information to an antenna control unit.
Example 2
Referring to fig. 1-3 of the specification, this embodiment discloses as another preferred embodiment of the present invention:
a broadband angle tracking method based on an SC-FDE transmission system comprises the following steps:
for radio frequency and signal RF received by antenna∑Difference signal RF△Outputs two paths of intermediate frequency signals IF after passing through signal conditioning circuits respectively∑And IF△Wherein, the difference channel does not carry out AGC closed-loop control, but directly uses AGC amplification of the sum channel to carry out channel gain control; to the output two intermediate frequency signals IF∑And IF△Respectively carrying out A/D sampling, digital preprocessing, signal synchronization and channel estimation; in the signal synchronization process, the difference channel does not carry out synchronization parameter estimation, but directly uses the synchronization information of the sum channel to carry out synchronization error correction; further extracting azimuth and pitch angle according to channel estimation results of sum and difference channelsThe error information is output to the antenna control unit after being respectively subjected to low-pass filtering; performing IDFT on the sum channel estimation result to obtain the sum channel impulse response estimation value IΣ(n),1≤n≤NUW，NUWRepresents the length of the UW sequence; the update rate is Rs/Nb，RsRepresenting the symbol rate, NbRepresenting the frame length; let it have the maximum energy (max [ | I)Σ(n)|2],1≤n≤NUW| represents an absolute value) is IΣ(P) with the sequence number value P; correspondingly, the impulse response estimated value at the position P in the difference channel impulse estimation result is IΔ(p), the tracking angle error value is E ═ IΣ(p)×IΔ(p)*，(·)*The representation is taken as the conjugate, which corresponds in part to the azimuth error EA＝Real[IΣ(p)×IΔ(p)*]Imaginary part corresponding to pitch angle error EE＝Imag[IΣ(p)×IΔ(p)*]And then respectively provided to the antenna control unit after low-pass filtering.
Example 3
Referring to fig. 1-3 of the specification, this embodiment discloses as another preferred embodiment of the present invention:
as shown in FIG. 1, FIG. 1 is a SC-FDE transmission frame structure, in which the UW (uniform word) sequence is a Chu sequence with Constant Amplitude Zero Auto-Correlation (CAZAC) characteristics, NbIndicating the transmission frame length and VD indicating the valid data sequence. Each frame comprises two UW sequences with the length of NUWThe former is used as cyclic prefix for eliminating the interference between blocks, and the latter is used for channel estimation and auxiliary synchronization.
SC-FDE demodulation step: fig. 2 is a SC-FDE signal demodulation architecture, which mainly includes modules such as a/D sampling, digital preprocessing, signal synchronization, channel estimation, and frequency domain equalization.
1) A/D sampling: the intermediate frequency received signal is sampled at a fixed sampling rate.
2) Digital preprocessing: the digital signal after A/D sampling is preprocessed, mainly including digital down-conversion and multi-stage filtering extraction (includingIntegral multiple extraction and fractional multiple extraction), matched filtering and the like, and finally outputting 4 times of symbol rate RsBaseband I, Q signal.
3) Signal synchronization: the baseband I, Q signals are synchronized, including UW sequence synchronization, carrier synchronization, and timing synchronization. The method comprises the steps of firstly realizing UW sequence synchronization according to the autocorrelation characteristic of a UW sequence, then realizing carrier synchronization (carrier frequency offset estimation and correction) through the phase relation of the UW sequence of adjacent transmission frames, realizing timing frequency offset estimation through the frequency domain correlation of the UW sequence of the adjacent transmission frames, and then completing timing error correction through a complete timing loop.
Suppose that the mth frame transmits a signal s [ mN ]b+n]Expressed as:
Figure BDA0002287349530000081
wherein N isUWDenotes the length of the UW sequence, sUW[n]Denotes the UW sequence.
The received signal after passing through the channel can be expressed as:
Figure BDA0002287349530000082
in the above formula, h (L) represents the channel impulse response with length L, x [ n ]]Representing the waveform of the transmitted signal, theta representing the timing offset present in the received signal, af representing the carrier frequency offset, fsRepresenting the signal sampling rate, ω n]Representing gaussian white noise.
The UW sequence synchronization first multiplies the received signal by the conjugate of the UW sequence and performs correlation accumulation, and then obtains the position d of the frame header by detecting the peak value of the accumulation result, as follows,
Figure BDA0002287349530000083
after the synchronous position of the UW sequence is obtained, the carrier synchronization is carried out through the phase relation between the front data block and the rear data block, the calculation is as follows,
Figure BDA0002287349530000084
under the condition that the sampling deviation theta of the front and the back data frames is approximately equal and the channel characteristics are approximately equal, the formula (2) is replaced by the formula (4), and phi (delta f) can be simplified into phi
Figure BDA0002287349530000085
Considering the transmitted data as uncorrelated with noise, the maximum likelihood of Δ f is estimated as
Figure BDA0002287349530000086
After the carrier synchronization is finished, only one timing deviation theta which changes slowly along with time exists in the received data, the time change rate of the received data can be estimated through the frequency domain correlation of the inter-frame UW sequence, and then the residual fixed timing deviation is compensated through a timing loop. Assuming that the data after carrier synchronization satisfies:
Figure BDA0002287349530000091
DFT (digital Fourier transform) conversion is carried out on the second UW sequence position in the two frames of data before and after the received data, wherein
Figure BDA0002287349530000092
Wherein the content of the first and second substances,
Figure BDA0002287349530000093
H[k]、XUW[k]and Ωn[k]Respectively represent
Figure BDA0002287349530000094
h (l), UW sequence and ω[n]DFT of (2).
Carrying out conjugate multiplication on corresponding frequency points of two adjacent frames to obtain delta FθFunction Ψ (. DELTA.F) ofθAnd k) is:
Figure BDA0002287349530000095
then Δ FθThe maximum likelihood estimate of (c) is:
Figure BDA0002287349530000096
in order to simplify the calculation process, the more accurate delta F can be obtained by weighted average of the calculation results of a few frequency pointsθAnd (6) estimating the value. And feeding back the timing estimation result to a fractional filtering extraction module in digital preprocessing to form a complete timing synchronization loop so as to eliminate timing deviation.
4) Channel estimation: the SC-FDE transmission frame structure ensures that the received data satisfies the circular convolution characteristic, and may use fft (fast Fourier transform) to perform frequency domain fast processing, but before performing frequency domain equalization, the channel needs to be estimated first. After the carrier synchronization and the timing synchronization are completed, the DFT of the second UW sequence signal of the data frame satisfies the following conditions:
Figure BDA0002287349530000097
since the UW sequence satisfies the frequency domain constant amplitude characteristic, the estimate of H [ k ] can be expressed as:
Figure BDA0002287349530000098
wherein, omega'n[k]Represents omegan[k]·XUW *[k]。
5) SC-FDE equalization: after obtaining the channel estimation result of the length of the UW sequence, it is necessary to interpolate the channel estimation result to Nb-NUWWithin the data block. Frequency domain equalizer coefficient C [ k ] designed by MSE criterion]Satisfies the following conditions:
Figure BDA0002287349530000101
although it is used for
Figure BDA0002287349530000102
Already contains the noise energy part, but considering the existence of randomness, in order to suppress the amplification effect of noise under a deep fading channel, a constant term C corresponding to a predefined signal-to-noise ratio is introduced into a denominator, so that the equalizer coefficient can be expressed as:
Figure BDA0002287349530000103
the DFT of the received signal in the effective data region and the first UW sequence region is expressed as:
Figure BDA0002287349530000104
the equalizer processed signal X k can be expressed as:
Figure BDA0002287349530000105
wherein the content of the first and second substances,
Figure BDA0002287349530000106
6) and (3) demodulation output: to obtain
Figure BDA0002287349530000107
Then, the obtained product was obtained by IDFT (inverse Digital Fourier transform)
Figure BDA0002287349530000108
To obtain the estimated value of the original transmitting signal
Figure BDA0002287349530000109
The entire demodulation process is completed.
As shown in fig. 3, the radio frequency sum and difference signals RF received for the antennasΣ、RF△Respectively output 2 paths of intermediate frequency signals IF after passing through signal conditioning circuits (including modules of low noise amplification, analog down conversion, filtering, AGC amplification and the like)Σ、IF△Wherein, the difference channel does not carry out AGC (automatic Gain control) closed-loop control, but directly uses AGC amplification of the sum channel to carry out channel Gain control; then, A/D sampling, digital preprocessing, signal synchronization and channel estimation are respectively carried out on the 2 paths of intermediate frequency signals, wherein synchronous parameter estimation is not carried out in difference channel processing, and a sum channel synchronous parameter (UW sequence position) and synchronous error correction (carrier frequency offset correction and timing error correction) are directly used; further extracting azimuth and pitch angle error information according to the sum and difference channel estimation results; and finally, performing low-pass filtering on the 2 angular errors and outputting the angular errors to an ACU (antenna control unit).
The angle error extraction method comprises the following steps: performing IDFT on the sum channel estimation result to obtain the sum channel impulse response estimation value IΣ(n),1≤n≤NUW，NUWRepresents the length of the UW sequence and the update rate is Rs/Nb，RsRepresenting the symbol rate, NbIndicating the frame length, provided with maximum energy
Figure BDA0002287349530000111
| represents an absolute value) is IΣ(P) the numerical value is P. Correspondingly, let the impulse response estimation value at the P position in the channel impulse estimation result be IΔ(p), the tracking angle error value is E ═ IΣ(p)×IΔ(p)*，(·)*The representation is taken as the conjugate, which corresponds in part to the azimuth error EA＝Real[IΣ(p)×IΔ(p)*]Imaginary part corresponding to pitch angle error EE＝Imag[IΣ(p)×IΔ(p)*]And then, the signals are provided to an ACU (antenna control unit) after low-pass filtering, respectively.
4.5 applicability of the method
The method is suitable for a broadband SC-FDE transmission system, wherein the length N of the UW sequenceUWThe length should be larger than the maximum multipath time delay of the actual channel, and the frame length is NbShould be much shorter than the actual channel coherence time (about 5%) with a symbol period TsThe minimum multipath time delay difference of the actual channel is smaller than the minimum multipath time delay difference of the actual channel, so that a main path signal and a multipath signal can be distinguished in a channel impulse response estimation result, and angle error information is extracted from the main path signal, therefore, the method is defined as a broadband angle tracking method based on an SC-FDE signal system.

Claims (6)

1. A broadband angle tracking method based on an SC-FDE transmission system is characterized in that: the method comprises the following steps:
for radio frequency sum signal received by antenna
Figure DEST_PATH_IMAGE001
Difference signal
Figure 536953DEST_PATH_IMAGE002
Respectively output two paths of intermediate frequency signals after passing through a signal conditioning circuit
Figure DEST_PATH_IMAGE003
And
Figure 250831DEST_PATH_IMAGE004
wherein, the difference channel does not carry out AGC closed-loop control, but directly uses AGC amplification of the sum channel to carry out channel gain control; for two paths of output intermediate frequency signals
Figure 296148DEST_PATH_IMAGE003
And
Figure 160198DEST_PATH_IMAGE004
respectively carrying out A/D sampling, digital preprocessing and signal processingSynchronization and channel estimation; in the signal synchronization process, the difference channel does not carry out synchronization parameter estimation, but directly uses the synchronization information of the sum channel to carry out synchronization error correction; further extracting azimuth and pitch angle error information according to channel estimation results of the sum channel and the difference channel, respectively performing low-pass filtering, and outputting the information to an antenna control unit;
the signal conditioning circuit mainly comprises a low noise amplifier module, an analog down-conversion module, a filtering module and an AGC (automatic gain control) amplification module; the A/D sampling refers to sampling an intermediate frequency receiving signal according to a fixed sampling frequency; the digital preprocessing specifically refers to preprocessing the digital signal after A/D sampling, mainly comprising a digital down-conversion module, a multistage filtering extraction module and a matched filtering module, and outputting 4 times of symbol rate after preprocessing
Figure DEST_PATH_IMAGE005
Baseband I, Q signal; the multistage filtering extraction module realizes integral multiple extraction and fractional multiple extraction.
2. The broadband angle tracking method based on the SC-FDE transmission system according to claim 1, wherein: performing IDFT on the sum channel estimation result to obtain the sum channel impulse response estimation value
Figure 771308DEST_PATH_IMAGE006
，
Figure DEST_PATH_IMAGE007
，
Figure 452825DEST_PATH_IMAGE008
Represents the length of the UW sequence; the update rate is
Figure DEST_PATH_IMAGE009
，
Figure 188700DEST_PATH_IMAGE010
Which is indicative of the rate of the symbols,
Figure DEST_PATH_IMAGE011
representing the frame length; setting the value of maximum energy to
Figure 184338DEST_PATH_IMAGE012
Serial number of
Figure DEST_PATH_IMAGE013
(ii) a In the corresponding, difference signal channel impulse response estimation result
Figure DEST_PATH_IMAGE015
The impulse response estimate at a location is
Figure 181113DEST_PATH_IMAGE016
Then the tracking angle error value is
Figure DEST_PATH_IMAGE017
，
Figure 236794DEST_PATH_IMAGE018
The representation is taken as conjugate, which corresponds in part to the azimuthal error
Figure DEST_PATH_IMAGE019
Imaginary part corresponding to pitch angle error
Figure 787861DEST_PATH_IMAGE020
And then respectively provided to the antenna control unit after low-pass filtering.
3. The method according to claim 2, wherein the method for tracking the wideband angle based on the SC-FDE transmission system comprises: the maximum energy is expressed as:
Figure DEST_PATH_IMAGE021
，
Figure 386857DEST_PATH_IMAGE022
representing taking the absolute value.
4. The broadband angle tracking method based on the SC-FDE transmission system according to claim 1, wherein: the signal synchronization specifically refers to performing synchronization processing on a baseband I, Q signal, including UW sequence synchronization, carrier synchronization and timing synchronization; firstly, realizing UW sequence synchronization according to the autocorrelation characteristic of the UW sequence, then realizing carrier synchronization through the UW sequence phase relationship of adjacent transmission frames, realizing timing frequency offset estimation through the frequency domain correlation of the UW sequence of the adjacent transmission frames, and then completing timing error correction through a complete timing loop; the carrier synchronization specifically refers to carrier frequency offset estimation and correction.
5. The method according to claim 4, wherein the method for tracking the wideband angle based on the SC-FDE transmission system comprises: the UW sequence synchronization specifically means that a received signal is multiplied by the conjugate of the UW sequence and correlated accumulation is performed, and then the position of a frame header is obtained by detecting the peak value of the accumulation result; after the UW sequence synchronization position is obtained, carrying out carrier synchronization through the phase relation between the front data block and the rear data block; after the carrier synchronization is completed, only one timing deviation slowly changing along with the time exists in the received data
Figure DEST_PATH_IMAGE023
Estimating the time change rate of the UW sequence frequency domain correlation between frames, and compensating the residual fixed timing deviation by a timing loop; and feeding back the timing estimation result to a fractional filtering extraction module in digital preprocessing to form a complete timing synchronization loop so as to eliminate timing deviation.
6. The broadband angle tracking method based on the SC-FDE transmission system according to claim 1, wherein: the channel estimation specifically means that after carrier synchronization and timing synchronization are completed, the DFT of the second UW sequence signal of the data frame satisfies
Figure 706980DEST_PATH_IMAGE024
In the formula (I), wherein,
Figure DEST_PATH_IMAGE025
、
Figure 871245DEST_PATH_IMAGE026
、
Figure DEST_PATH_IMAGE027
and
Figure 909608DEST_PATH_IMAGE028
respectively represent
Figure DEST_PATH_IMAGE029
、
Figure 43786DEST_PATH_IMAGE030
UW sequence and
Figure DEST_PATH_IMAGE031
DFT of (2); wherein
Figure 483995DEST_PATH_IMAGE032
Indicating the data after being subjected to carrier synchronization,
Figure DEST_PATH_IMAGE033
is expressed as length of
Figure 553582DEST_PATH_IMAGE034
The channel impulse response of (2);
Figure DEST_PATH_IMAGE035
representing white gaussian noise;
Figure 79241DEST_PATH_IMAGE026
the estimate of (d) can be expressed as:
Figure 751531DEST_PATH_IMAGE036
wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE037
to represent
Figure 983929DEST_PATH_IMAGE038
。
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