Method, device and correction method for quickly estimating frequency deviation in a large range

Abstract

The present invention discloses a method for rapidly estimating frequency deviation in a large range, the method comprising: a transmitting end sends a signal x(λ) at time T0, a receiving end obtains a received signal y(λ) at time T1, and obtains: #imgabs0# through a processor; obtains: #imgabs1# through a processor; establishes a new function: #imgabs2#; outputs #imgabs3#; uses a real-valued signal to obtain #imgabs4#; substitutes #imgabs5# and #imgabs6# into a cross-correlation function through a processor to obtain a frequency deviation #imgabs7#. The present invention is based on an FFT model, screens out constants, splits Y(n), establishes a model of a frequency-free signal and a frequency-deviation signal, so that the model meets the solution requirements of the cross-correlation function, and realizes rapid measurement of the frequency deviation. The present invention can be widely used in existing wireless uplink and downlink communication systems to solve the problem of time / frequency asynchrony when communicating between terminals.

Description

Technical Field

[0001] The invention relates to a method, a device and a correction method for quickly estimating frequency deviation in a large range, and belongs to the technical field of carrier waves. Background Art

[0002] In the traditional parallel transmission system, the entire signal band is divided into multiple parallel non-orthogonal subcarriers, each subcarrier is modulated separately, and the entire system constitutes frequency division multiplexing. There is no spectrum overlap between two adjacent subcarriers, which is conducive to eliminating subcarrier interference. However, this frequency division multiplexing method reduces the utilization of the spectrum. In order to improve the utilization of the spectrum, the idea of ​​parallel transmission and FDM with spectrum overlap, namely orthogonal frequency division multiplexing OFDM, was proposed in the mid-1960s.

[0003] Multi-carrier technology divides the transmission bandwidth into many narrowband sub-carriers for parallel transmission, which can achieve a higher transmission rate in a limited bandwidth. In traditional frequency division multiplexing technology, the sub-carriers do not overlap with each other and a protection interval is added, resulting in low frequency utilization. In OFDM technology, the sub-carriers are orthogonal. From the perspective of the time domain, each sub-carrier has an integer multiple of periods within an OFDM symbol period, and each adjacent sub-carrier differs by one period. From the perspective of the frequency domain, at the center of each sub-carrier, the values ​​of other sub-carriers are zero, thereby saving precious frequency resources and improving frequency utilization.

[0004] In the OFDM system, the modulated digital signal at the transmitter is converted into an analog signal through D / A, modulated by the RF center frequency, and sent into the wireless channel for transmission. At the receiving end, the RF analog signal is first adjusted, moved from RF to baseband, and then sampled and digitized at a sampling rate F, and finally sent to the OFDM demodulator. However, if a carrier frequency deviation Δf occurs due to unstable crystal oscillators at both ends of the transmitter and receiver, the Doppler effect in a mobile environment, or phase noise introduced into a nonlinear channel, not only will the signal of the corresponding channel fall on other channels when adjusting the signal, resulting in bit errors, but it may also destroy the orthogonality of the subcarriers and cause interference between subcarriers. Summary of the invention

[0005] The purpose of the present invention is to provide a method, device and correction method for quickly estimating frequency deviation in a large range. The method and device not only solve the problem of channel confusion and mutual interference between subcarriers caused by frequency deviation of OFDM structure signals in the prior art, but also solve the problem of large measurement amount and slow measurement speed in previous frequency deviation correction methods.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for quickly estimating frequency deviation in a large range, the method comprising:

[0007] After the transmitter sends out a real-valued signal x(λ) at time T0;

[0008] The receiving end collects the received signal at time T1, which is recorded as y(λ), where x(λ) and y(λ) are both baseband time domain signals;

[0009] The processor gets: ,in, , f d is the frequency deviation;

[0010] The processor performs a fast Fourier transform on the received signal to obtain: , n=1,2...N;

[0011] Create a new function: ;

[0012] Screening constant , output ;

[0013] Use a real-valued signal to create a new function without frequency deviation: ;

[0014] Through the processor and Substituting into the cross-correlation function, we get the frequency deviation , where the original peak point is at A, the peak point after shift is at B, and the output frequency deviation;

[0015] Where k=1:(N-1), k+1=2:N.

[0016] The further improved scheme in the above technical scheme is as follows:

[0017] 1. In the above solution, the receiving end is a microphone or an antenna.

[0018] 2. In the above scheme, the real-valued signal is filtered out by a filter to remove signals of other frequencies other than the real-valued signal.

[0019] 3. In the above scheme, the real-valued signal and the imaginary-valued signal transformed from the real-valued signal are respectively passed through a low-pass filter, and then down-sampled by a sampler to output real and imaginary data.

[0020] 4. In the above scheme, a pilot signal is used instead of a real-valued signal.

[0021] 5. In the above scheme, the received signal y(λ) is a discrete signal.

[0022] The present invention also provides a frequency deviation correction method, based on the obtained f d , ,y new (λ) is the corrected signal.

[0023] The present invention also provides a device for quickly estimating frequency deviation in a large range, comprising:

[0024] A receiving end, used for receiving a real-valued signal sent by a transmitting end;

[0025] Filter, used to filter out clutter and retain real-valued signals;

[0026] Low-pass filter, used to further filter out clutter;

[0027] Sampler, used for interval sampling;

[0028] The processor is written with frequency deviation estimation sequence instructions and cross-correlation function formulas, and is used to drive the receiver, filter, low-pass filter and sampler to collect frequency deviation signals and non-frequency deviation signals, satisfy the cross-correlation function, complete the calculation, and output the frequency deviation results.

[0029] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] 1. The method, device and correction method for rapidly estimating frequency deviation in a large range of the present invention are based on the FFT model, screen out constants, split Y (n), and establish models of frequency deviation-free signals and frequency deviation signals to meet the requirements for solving the cross-correlation function, thereby realizing rapid measurement of frequency deviation. The method can be widely used in existing wireless uplink and downlink communication systems to solve the problem of time / frequency asynchronism during communication between terminals.

[0031] 2. The method, device and correction method for quickly estimating frequency deviation in a large range of the present invention can obtain the frequency deviation value by optimizing the method model with only one OFDM frame signal, with small amount of calculation, fast measurement speed and high estimation efficiency; at the same time, the frequency deviation calculation method is applicable to the full bandwidth, with a wider range of application and higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Attached Figure 1 The figure is a flow chart of a method for rapidly estimating frequency deviation within a large range according to the present invention. DETAILED DESCRIPTION

[0033] The method and device of the present invention are used to solve the frequency deviation problem of OFDM signal structure and similar signal structures.

[0034] Embodiment 1: A method for quickly estimating frequency deviation in a large range, see the attached Figure 1 , the method comprising:

[0035] The transmitter sends a signal x(λ) at time T0, and uses a microphone as the receiver to collect an audio signal (received signal) at time T1, recorded as y(λ). x(λ) and y(λ) are baseband time domain signals, and the audio signal is input into the filter. Here, the filter frequency is set according to the audio signal frequency to filter out clutter for subsequent processing.

[0036] The filtered audio signal (real-valued signal) x(λ) is phase-shifted by the processor to obtain a complex analytical signal:

[0037] ,in,

[0038] , f d For frequency deviation.

[0039] The processor further performs a fast Fourier transform (FFT) on the analytical signal, transforming it from the time domain to the frequency domain to facilitate the analysis of the frequency deviation, and obtains: , n=1, 2...N, establish a new function , screening constant , output At the same time, when the real-valued signal is known at the transmitter and receiver, the function is obtained using the real-valued signal , let k=1:(N-1), k+1=2:N, and we get: and , the frequency deviation output And the output without frequency deviation Substituting into the cross-correlation function (xcorr), we can find the coordinate point A of the peak without frequency deviation and the coordinate point B of the peak after shift. .

[0040] Embodiment 2: A device for rapidly estimating frequency deviation over a large range comprises a receiving end, a filter, a low-pass filter and a sampler arranged in series, and also comprises a processor connected to the above-mentioned devices, wherein the receiving end is various microphones, antennas, etc. for receiving and collecting signals, the filter is used to filter out interference to prevent the real-valued signal from being affected by other interference signals, and the low-pass filter and the sampler are used to further filter the band and take samples at intervals to reduce the amount of data for easy processing; and the processor is pre-written with frequency deviation estimation sequence instructions and formulas, wherein the sequence instructions include controlling the receiving end to receive the collected signal, controlling the filter and the low-pass filter to filter, issuing a downsampling command to the sampler, and also including formulas and conversion instructions for performing phase transformation and combining the signal branches to form complex numbers and then performing FFT transformation, as well as establishing a new function formula and substituting it into the cross-correlation function for solution.

[0041] Here, the processor can not only output the frequency deviation solution value, but also present the waveform analysis on the output interface, showing the displacement of the peak value, intuitively reflecting the frequency deviation amount.

[0042] Based on the above device, the method for quickly estimating frequency deviation in a large range is:

[0043] The transmitter sends a signal x(λ) at time T0, uses the antenna as the receiver to collect the wireless signal (received signal) at time T1, and inputs the wireless signal into the filter. Here, the filter frequency is set according to the wireless signal frequency to filter out clutter for subsequent processing.

[0044] The processor performs phase transformation on the filtered wireless signal (real-valued signal) x(λ). The real-valued signal and the imaginary-valued signal are respectively passed through a low-pass filter, and then downsampled by the sampler to output the real and imaginary data, and the complex analytical signal is combined:

[0045] ,in,

[0046] , f d For frequency deviation.

[0047] The processor further performs a fast Fourier transform (FFT) on the analytical signal, transforming it from the time domain to the frequency domain to facilitate the analysis of the frequency deviation, and obtains: , n=1, 2...N, establish a new function , screening constant , output At the same time, when the real-valued signal is known at the transmitter and receiver, the function is obtained using the real-valued signal , let k=1:(N-1), k+1=2:N, and we get: and , the frequency deviation output And the output without frequency deviation Substituting into the cross-correlation function (xcorr), we can find the coordinate point A of the peak without frequency deviation and the coordinate point B of the peak after shift. .

[0048] The pilot signal may be used to replace the real-valued signal to perform measurement and obtain corrected data.

[0049] Embodiment 3: A frequency offset correction method, the method comprising:

[0050] Based on Example 1 or 2, the frequency deviation value f is obtained. d In the subsequent signal processing, when the original signal y(λ) is obtained, the processor writes a correction instruction and imports the original signal y(λ). Get the corrected signal.

[0051] By adopting the above scheme, based on the FFT model, the constant is screened out, Y(n) is split, and the models of the frequency-deviation-free signal and the frequency-deviation signal are established to meet the requirements for solving the cross-correlation function and realize the rapid measurement of the frequency deviation. This scheme can be widely used in existing wireless uplink and downlink communication systems to solve the problem of time / frequency asynchrony during communication between terminals.

[0052] In addition, through the optimization method model, only one OFDM frame signal is needed to obtain the frequency deviation value, with small calculation amount, fast measurement speed and high estimation efficiency; at the same time, the frequency deviation calculation method is applicable to the full bandwidth, with a wider range of application and higher accuracy.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for rapidly estimating frequency deviation in a large range, characterized in that: The method comprises: After the transmitter sends out a real-valued signal x(λ) at time T0; The receiving end collects the received signal at time T1, which is recorded as y(λ), where x(λ) and y(λ) are both baseband time domain signals; The processor gets: ,in, , f d is the frequency deviation; The processor performs a fast Fourier transform on the received signal to obtain: , n=1,2...N; Create a new function: ; Screening constant , output ; Use a real-valued signal to create a new function without frequency deviation: ; Through the processor and Substituting into the cross-correlation function, we get the frequency deviation , where the original peak point is at A, the peak point after shift is at B, and the output frequency deviation; Where k=1:(N-1), k+1=2:N.

2. The method for rapidly estimating frequency deviation in a large range according to claim 1, characterized in that: The receiving end is a microphone or an antenna.

3. The method for rapidly estimating frequency deviation in a large range according to claim 1, characterized in that: The real-valued signal is filtered out through a filter to remove signals of other frequencies than the real-valued signal.

4. The method for rapidly estimating frequency deviation in a large range according to claim 1, characterized in that: The real-valued signal and the imaginary-valued signal transformed from the real-valued signal are respectively passed through a low-pass filter, and then down-sampled by a sampler to output real and imaginary data.

5. The method for rapidly estimating frequency deviation in a large range according to claim 1, characterized in that: A pilot signal is used instead of a real-valued signal.

6. The method for rapidly estimating frequency deviation in a large range according to claim 1, characterized in that: The received signal y(λ) is a discrete signal.

7. A frequency deviation correction method, characterized in that: Based on any one of claims 1 to 6, f d , ,y new (λ) is the corrected signal.

8. A device for rapidly estimating frequency deviation in a large range, characterized in that: include: A receiving end, used for receiving a real-valued signal sent by a transmitting end; Filter, used to filter out clutter and retain real-valued signals; Low-pass filter, used to further filter out clutter; Sampler, used for interval sampling; A processor, having a frequency deviation estimation sequence instruction and a cross-correlation function formula, is used to drive a receiver, a filter, a low-pass filter and a sampler to collect frequency deviation signals and frequency deviation-free signals, so as to implement the method described in any one of claims 1 to 6, satisfy the cross-correlation function, complete the calculation, and output the frequency deviation result.

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