Optical delay calibration method and device for broadband phased array

Abstract

The invention discloses an optical time delay calibration method of a broadband phased array. According to the method, the defect that a traditional optical time delay measurement method is only limited to a single measurement domain such as a time domain, a frequency domain or a phase domain is overcome, resources of multiple dimensions such as the time domain, the frequency domain and the polarization domain are reused, and the optical time delay measurement accuracy is improved based on the constructed optical domain vernier effect. By solving an indefinite equation formed by two optical pulse sequences in different polarization states, the measurable range of the optical time delay in a high-speed measurement scene is extended. The invention also discloses an optical time delay calibration device of the broadband phased array. Compared with the prior art, large-range, high-precision, multi-channel and rapid time delay measurement and calibration can be realized.

Description

Technical Field

[0001] The present invention relates to a method and device for calibrating optical delay of a broadband phased array. Background Art

[0002] Delay calibration for wideband phased arrays is a key step in improving array system performance. Efficient delay calibration can significantly reduce phase errors in signal transmission, thereby improving beamforming accuracy and directivity. In fields such as radar, communications, and sonar, the accuracy and efficiency of delay calibration directly determine overall system performance. Consequently, current systems place higher demands on delay calibration technology, requiring it to balance wide-range, high-precision, multi-channel, and high-speed measurement. In large-scale arrays or multi-antenna systems, multi-channel delay consistency is crucial for array gain, beam direction stability, and sidelobe suppression. However, factors such as inter-channel device variations, inconsistent link lengths, and environmental variations make multi-channel delay measurement and calibration extremely challenging. Multi-channel calibration requires not only consistent measurement accuracy across all channels but also sufficient measurement efficiency to support real-time or near-real-time calibration.

[0003] However, existing high-precision delay measurement methods often require a trade-off between measurement range and speed. If multiple channels need to be calibrated, the measurement time overhead will increase exponentially, becoming a bottleneck restricting the further development of delay calibration technology. Common optical delay measurement methods are mainly based on the time domain, frequency domain, and phase domain. The time domain method directly measures the optical transmission delay by calculating the time interval between the detection and reference signals, making it suitable for long-distance and large-scale delay measurement. However, its accuracy is limited by pulse width and detector response, and it is difficult to achieve sub-picosecond accuracy. The frequency domain method uses the frequency characteristics of the optical signal to measure, with fast measurement speed and femtosecond accuracy. However, its measurement range is limited by the modulation frequency, and it requires high system stability and light source coherence, resulting in limited anti-interference capabilities. The phase domain method derives the optical delay from the phase shift between the reference and detection signals, and has extremely high measurement accuracy. However, the single-frequency measurement range is limited by the wavelength, and multi-frequency modulation is required to achieve phase unwrapping, which reduces measurement speed.

[0004] In summary, traditional technologies with a single measurement domain are unable to simultaneously meet the comprehensive requirements of broadband phased arrays for large-range, high-precision, multi-channel, and high-speed measurements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing single measurement domain broadband phased array optical delay calibration technology and provide a broadband phased array optical delay calibration method to achieve large-scale, high-precision, multi-channel and fast delay measurement and calibration.

[0006] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0007] A method for calibrating optical delay of a broadband phased array comprises the following steps:

[0008] S1. Two optical pulse sequences with different time-frequency characteristics are transmitted in parallel in two orthogonal polarization states in the optical domain to obtain an optical signal, and the optical signal is divided into two paths, one as a reference optical signal and the other as a detection optical signal;

[0009] S2. Perform photoelectric conversion on the reference optical signal and the detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array;

[0010] S3. Convert the reference photocurrent signal and the measured photocurrent signal into the digital domain respectively. In the digital domain, obtain the unambiguous coarse delay of the nth optical link to be calibrated of the broadband phased array by solving the indeterminate equation based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states;

[0011] S4. Perform delay compensation on each of the optical links to be calibrated of the broadband phased array according to the obtained deviation between the delay of each of the optical links to be calibrated and the set delay.

[0012] Furthermore, the following steps are included between steps S3 and S4:

[0013] The unambiguous coarse delay of each optical link to be calibrated in the broadband phased array is phase-unwrapped and combined with the carrier frequency phase shift of two optical pulse sequences to obtain the precise delay of each optical link to be calibrated in the broadband phased array.

[0014] Preferably, the parallel transmission of two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain is specifically achieved by the following method: using two electrical pulse signals with different time-frequency characteristics as modulation signals, and intensity modulating the continuous single-frequency optical signal through a dual-polarization Mach-Zehnder modulator.

[0015] Further preferably, the expressions of the two electrical pulse signals with different time-frequency characteristics are:

[0016]

[0017] Wherein, a=1,2 is the serial number of the electric pulse signal; b is the pulse index number in the electric pulse signal; T rep,a is the repetition period of the ath electric pulse signal; T wid,a is the pulse width of the ath electrical pulse signal; f ais the carrier frequency of the ath electrical pulse signal; rect(t) is the pulse envelope function, which determines the amplitude envelope of the pulse. When |t|≤0.5, rect(t)=1, and when |t|>0.5, rect(t)=0.

[0018] Preferably, the unambiguous rough delay of the nth optical link to be calibrated of the broadband phased array is obtained by the following method: using a cross-correlation algorithm to extract the time difference between two different optical pulse sequences between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, and then solving the following indeterminate equation to obtain the unambiguous rough delay τ of the nth optical link to be calibrated rough,n :

[0019] τ rough,n =τ mea,n,1 +x·T rep,1 =τ mea,n,2 +y·T rep,2

[0020] Where, T rep,1 、T rep,2 are the repetition periods of the first and second optical pulse trains, τ mea,n,1 , τ mea,n,2 are the time difference of the first optical pulse sequence and the time difference of the second optical pulse sequence between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, respectively. x is The corresponding minimum positive integer solution, y is The corresponding smallest positive integer solution, τ Δn is the absolute optical delay of the nth optical link to be calibrated.

[0021] Based on the same inventive concept, the following technical solutions can also be obtained:

[0022] An optical delay calibration device for a broadband phased array, comprising:

[0023] The signal generation module generates an optical signal by transmitting two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain in parallel. The optical signal is then split into two paths: one as a reference optical signal and the other as a detection optical signal.

[0024] an optoelectronic conversion module for performing optoelectronic conversion on a reference optical signal and a detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array;

[0025] A digital processing module is used to convert the reference photocurrent signal and the measured photocurrent signal into the digital domain. In the digital domain, based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states, the unambiguous coarse delay of the nth optical link to be calibrated in the broadband phased array is obtained by solving the indeterminate equation.

[0026] The calibration module is used to perform delay compensation on each optical link to be calibrated of the broadband phased array according to the deviation between the delay of each optical link to be calibrated of the broadband phased array and the set delay.

[0027] Furthermore, the digital processing module is also used to perform phase expansion on the unambiguous coarse delay of each optical link to be calibrated in the broadband phased array, and combine it with the carrier frequency phase shift of the two optical pulse sequences to obtain the precise delay of each optical link to be calibrated in the broadband phased array.

[0028] Preferably, the parallel transmission of two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain is specifically achieved by the following method: using two electrical pulse signals with different time-frequency characteristics as modulation signals, and intensity modulating the continuous single-frequency optical signal through a dual-polarization Mach-Zehnder modulator.

[0029] Further preferably, the expressions of the two electrical pulse signals with different time-frequency characteristics are:

[0030]

[0031] Wherein, a=1,2 is the serial number of the electric pulse signal; b is the pulse index number in the electric pulse signal; T rep,a is the repetition period of the ath electric pulse signal; T wid,a is the pulse width of the ath electrical pulse signal; f a is the carrier frequency of the ath electrical pulse signal; rect(t) is the pulse envelope function, which determines the amplitude envelope of the pulse. When |t|≤0.5, rect(t)=1, and when |t|>0.5, rect(t)=0.

[0032] Preferably, the unambiguous rough delay of the nth optical link to be calibrated of the broadband phased array is obtained by the following method: using a cross-correlation algorithm to extract the time difference between two different optical pulse sequences between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, and then solving the following indeterminate equation to obtain the unambiguous rough delay τ of the nth optical link to be calibrated rough,n :

[0033] τ rough,n =τ mea,n,1 +x·T rep,1 =τ mea,n,2 +y·T rep,2

[0034] Where, T rep,1 、T rep,2 are the repetition periods of the first and second optical pulse trains, τ mea,n,1 , τ mea,n,2 are the time difference of the first optical pulse sequence and the time difference of the second optical pulse sequence between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, respectively. x is The corresponding minimum positive integer solution, y is The corresponding smallest positive integer solution, τ Δn is the absolute optical delay of the nth optical link to be calibrated.

[0035] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0036] This invention addresses the shortcomings of traditional optical delay measurement methods, which are limited to a single measurement domain such as the time domain, frequency domain, or phase domain. It reuses resources in multiple dimensions, including the time domain, frequency domain, and polarization domain. Based on the constructed optical domain vernier effect, this invention solves the indeterminate equation composed of two optical pulse sequences in different polarization states. This extends the measurable range of optical delay in high-speed measurement scenarios, enabling large-scale, high-precision, multi-channel, and rapid optical delay measurement and calibration for broadband phased arrays.

[0037] The present invention further combines the phase domain method on the basis of the above technical solution. By extracting the carrier frequency phase shift of the optical pulse sequence and combining it with the unambiguous rough delay obtained by the above technical solution, more accurate delay data is obtained, thereby further improving the measurement accuracy of the optical link delay to be calibrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure is a schematic diagram showing the structural principle of a specific embodiment of the optical delay calibration device for a broadband phased array according to the present invention. DETAILED DESCRIPTION

[0039] To address the shortcomings of traditional optical delay measurement methods that are limited to a single measurement domain such as the time domain, frequency domain or phase domain, the solution of the present invention is to multiplex resources in multiple dimensions such as the time domain, frequency domain, and polarization domain. Based on the constructed optical domain vernier effect, by solving the indeterminate equation composed of two optical pulse sequences in different polarization states, the measurable range of optical delay in high-speed measurement scenarios is extended, and large-scale, high-precision, multi-channel, and fast optical delay measurement and calibration of broadband phased arrays are realized.

[0040] The optical delay calibration method for a broadband phased array proposed in the present invention comprises the following steps:

[0041] S1. Two optical pulse sequences with different time-frequency characteristics are transmitted in parallel in two orthogonal polarization states in the optical domain to obtain an optical signal, and the optical signal is divided into two paths, one as a reference optical signal and the other as a detection optical signal;

[0042] S2. Perform photoelectric conversion on the reference optical signal and the detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array;

[0043] S3. Convert the reference photocurrent signal and the measured photocurrent signal into the digital domain respectively. In the digital domain, obtain the unambiguous coarse delay of the nth optical link to be calibrated of the broadband phased array by solving the indeterminate equation based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states;

[0044] S4. Perform delay compensation on each of the optical links to be calibrated of the broadband phased array according to the obtained deviation between the delay of each of the optical links to be calibrated and the set delay.

[0045] The optical delay calibration device for a broadband phased array proposed in the present invention comprises:

[0046] The signal generation module generates an optical signal by transmitting two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain in parallel. The optical signal is then split into two paths: one as a reference optical signal and the other as a detection optical signal.

[0047] an optoelectronic conversion module for performing optoelectronic conversion on a reference optical signal and a detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array;

[0048] A digital processing module is used to convert the reference photocurrent signal and the measured photocurrent signal into the digital domain. In the digital domain, based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states, the unambiguous coarse delay of the nth optical link to be calibrated in the broadband phased array is obtained by solving the indeterminate equation.

[0049] The calibration module is used to perform delay compensation on each optical link to be calibrated of the broadband phased array according to the deviation between the delay of each optical link to be calibrated of the broadband phased array and the set delay.

[0050] Based on the above technical solution, the present invention further improves the accuracy of delay measurement through the following method:

[0051] The unambiguous coarse delay of each optical link to be calibrated in the broadband phased array is phase-unwrapped and combined with the carrier frequency phase shift of two optical pulse sequences to obtain the precise delay of each optical link to be calibrated in the broadband phased array.

[0052] To facilitate public understanding, the technical solution of the present invention is described in detail below through a specific embodiment with reference to the accompanying drawings:

[0053] The structure of the optical delay calibration device for broadband phased array in this embodiment is as follows: Figure 1 As shown, the system includes a laser, an arbitrary waveform generator, a dual-polarization Mach-Zehnder modulator, a coupler, a circulator, an optical switch, a photoelectric detection module, a multi-channel analog-to-digital converter, a solver module, and a control module. The laser outputs a continuous single-wavelength optical signal, which is then fed into the dual-polarization Mach-Zehnder modulator. This optical signal is intensity-modulated by two electrical pulse trains with different time-frequency characteristics generated by the arbitrary waveform generator. The modulated optical signal is input into the coupler and split into two paths: one serving as a reference optical signal and the other as a detection optical signal. This signal enters the circulator and is then output from one end of the circulator to the optical switch. The optical switch is responsible for rapidly switching and selecting the N optical links to be calibrated in the broadband phased array, thereby controlling the detection optical signal to enter the nth optical link to be calibrated for delay measurement. The detection echo optical signal, containing the delay information of the optical link to be calibrated, is then input into the other end of the circulator. Two photodetectors perform beat frequency processing on the reference and detection echo optical signals, respectively, to generate two photocurrent signals. After being converted by a multi-channel analog-to-digital converter, the two photocurrent signals are input into the solution module. In the digital domain, based on the optical domain vernier effect, the indeterminate equation consisting of the folded light transmission delay is solved to obtain the unambiguous delay of the optical link to be calibrated. The measurement accuracy of the delay of the optical link to be calibrated is further improved by extracting the phase shift of the carrier signal. Subsequently, by comparing the deviation between the measured delay and the theoretical delay, the calibration signal corresponding to each optical link to be calibrated is generated, and the control module is used to complete the delay compensation.

[0054] The laser output center frequency is f c The optical signal E i (t), its expression is:

[0055] E i (t) = E o expj(2πf c t) (1)

[0056] Among them, E o is the amplitude of the optical signal.

[0057] The optical signal is sent to the dual-polarization Mach-Zehnder modulator for modulation, and the two electrical pulse signals w1(t) and w2(t) with different time-frequency characteristics are modulated into the optical signal Ei In the two orthogonal polarization states of s and p of (t), the modulated optical signal can be expressed as:

[0058]

[0059] Where M is the electro-optical modulation coefficient.

[0060] The electrical pulse signals w1(t) and w2(t) can be designed according to actual needs. As long as they have different time-frequency characteristics, the optical domain vernier effect can be achieved, thereby extending the optical delay measurement range. The electrical pulse signal in this embodiment is generated by an arbitrary waveform generator and its expression is:

[0061]

[0062] Wherein, a=1,2 is the serial number of the electric pulse signal; b is the index number of the electric pulse sequence; T rep,a is the repetition period of the ath electric pulse signal; T wid,a is the pulse width of the ath electrical pulse signal; f a is the carrier frequency of the ath electrical pulse signal; rect(t) is the pulse envelope function, which determines the amplitude envelope of the pulse. When |t|≤0.5, rect(t)=1, and when |t|>0.5, rect(t)=0.

[0063] The modulated optical signal is sent to the optical coupler and divided into a detection optical signal and a reference optical signal. The detection optical signal is sent to the circulator for reflection measurement (through measurement can also be used). The optical switch is used to sequentially measure the N optical links to be calibrated in the broadband phased array. The measurement time for each link is T m , satisfying T m >T rep,a , the expression of the light signal reflected back after measurement is:

[0064]

[0065] Among them, α n and τ n are the transmission loss and measured delay of the nth optical link to be calibrated respectively.

[0066] The reference optical signal and the measurement optical signal are then sent to different photoelectric detection modules for photoelectric conversion to form a reference photocurrent signal and a measurement photocurrent signal. Taking the nth optical link to be calibrated as an example, the expressions of the two photocurrent signals can be written as:

[0067]

[0068] Among them, η is the responsiveness of the photoelectric detection module, τ refis the transmission delay of the reference optical signal through the link; the relative delay difference between the measured optical signal and the reference optical signal is τ Δn =2τ n -τ ref .

[0069] The two photocurrent signals are then input into a multi-channel analog-to-digital converter for analog-to-digital conversion, and the resulting digital signals are input into the solution module for further processing. According to formulas (5) and (6), τ can be extracted by the time difference between the pulse sequences. Δn However, the time measurement accuracy of two pulse sequences is limited by the pulse width and sampling rate, and in order to increase the measurement speed, T must be reduced. m , thereby reducing T rep,a , which limits the measurable range of optical delay; on the other hand, the carrier frequency f a The phase shift is used to extract the high-precision τ Δn , but there is a 2π ambiguity problem in the phase, namely:

[0070]

[0071] in, is the phase error of the phase detector, Defined as the floor sign.

[0072] To this end, this embodiment first uses optical pulse sequences in two polarization states to construct a vernier effect for delay measurement to extend the measurement range of optical link delay. Specifically, the cross-correlation algorithm is used to extract two different optical pulse sequences w between the measured photocurrent and the reference photocurrent in the nth link to be tested. a (t) time difference τ mea,n,a :

[0073]

[0074] Where Δτ represents the delay measurement error introduced by the cross-correlation measurement, is the floor symbol, when τ Δn <T rep,a , then τ mea,n,a =τ Δn , indicating that the optical delay measurement at this time is within the measurable range of the pulse sequence a. When τ Δn >T rep,a To obtain the absolute optical delay τ Δn , then we need to solve Specific value of . To construct the indeterminate equation:

[0075] τ rough,n =τ mea,n,1 +x·T rep,1 =τ mea,n,2 +y·Trep,2 (9)

[0076] τ rough,n =τ Δn +Δτ (10)

[0077] Among them, τ rough,n is the unambiguous rough delay of the nth optical link to be measured obtained based on the vernier effect, which contains the measurement error Δτ, and x is The corresponding minimum positive integer solution, y is The corresponding minimum positive integer solution; when 2|Δτ|<|T rep,1 -T rep,2 |, and 0.5 <T rep,1 / T rep,2 <2, the smallest positive integer pair {x,y} that satisfies the above equation (10) is The correct answer.

[0078] After obtaining the unambiguous optical link delay to be calibrated, the phase unwrapping process can be further completed:

[0079]

[0080] Substituting equations (7) and (10) into equation (11), we can obtain the following expression:

[0081]

[0082] The carrier frequency phase shift It can be obtained through a variety of existing technologies. For example, the two photocurrent signals are directly input into a commercial phase detection module. The phase detection module will output a voltage signal proportional to the phase shift value in real time. The corresponding phase shift value can be solved by sampling the voltage signal; or the two photocurrent signals are input into an analog-to-digital converter for sampling, and then the relative phase shift value of the two signals can be accumulated in the digital domain through a matched filtering algorithm; or the two photocurrent signals are subjected to orthogonal (IQ) down-conversion processing respectively, and then the phase shift value is obtained through IQ demodulation processing. It can be concluded from formula (12) that if and only if the delay error Δτ and the phase detection error satisfy When the conditions This formula is valid. Finally, the delay τ of the nth optical link to be calibrated can be obtained n :

[0083]

[0084] Then, by comparing the error between the measured delay and the set delay, a calibration signal corresponding to each optical link to be calibrated is generated, and the delay compensation is completed using the control module.

[0085] For sampled digital signals, the minimum time interval is the inverse of the sampling rate, typically on the order of hundreds of picoseconds to nanoseconds. Further phase detection of the carrier signal overcomes measurement speed limitations and improves the accuracy of delay measurement and calibration to sub-picoseconds, effectively supporting fast, large-scale, and high-precision delay calibration for broadband phased arrays.

Claims

1. A method for optical delay calibration of a broadband phased array, characterized in that: The following steps are involved: S1. Two optical pulse sequences with different time-frequency characteristics are transmitted in parallel in two orthogonal polarization states in the optical domain to obtain an optical signal, and the optical signal is divided into two paths, one as a reference optical signal and the other as a detection optical signal; S2. Perform photoelectric conversion on the reference optical signal and the detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array; S3. Convert the reference photocurrent signal and the measured photocurrent signal into the digital domain respectively. In the digital domain, obtain the unambiguous coarse delay of the nth optical link to be calibrated of the broadband phased array by solving the indeterminate equation based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states; S4. Perform delay compensation on each of the optical links to be calibrated of the broadband phased array according to the obtained deviation between the delay of each of the optical links to be calibrated and the set delay.

2. The optical delay calibration method for a broadband phased array according to claim 1, wherein: The following steps are also included between steps S3 and S4: The unambiguous coarse delay of each optical link to be calibrated in the broadband phased array is phase-unwrapped and combined with the carrier frequency phase shift of two optical pulse sequences to obtain the precise delay of each optical link to be calibrated in the broadband phased array.

3. The optical delay calibration method for a broadband phased array according to claim 1 or 2, wherein: The parallel transmission of two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain is specifically achieved by the following method: using two electrical pulse signals with different time-frequency characteristics as modulation signals, intensity modulating the continuous single-frequency optical signal through a dual-polarization Mach-Zehnder modulator.

4. The optical delay calibration method for a broadband phased array according to claim 3, wherein: The expressions of the two electrical pulse signals with different time-frequency characteristics are: Wherein, a=1,2 is the serial number of the electric pulse signal; b is the pulse index number in the electric pulse signal; T rep,a is the repetition period of the ath electric pulse signal; T wid,a is the pulse width of the ath electrical pulse signal; f a is the carrier frequency of the ath electrical pulse signal; rect(t) is the pulse envelope function, which determines the amplitude envelope of the pulse. When |t|≤0.5, rect(t)=1, and when |t|>0.5, rect(t)=0.

5. The optical delay calibration method for a broadband phased array according to claim 1 or 2, wherein: The unambiguous rough delay of the nth optical link to be calibrated in the broadband phased array is obtained by the following method: the time difference between two different optical pulse sequences between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated is extracted using the cross-correlation algorithm, and then the unambiguous rough delay τ of the nth optical link to be calibrated is obtained by solving the following indeterminate equation: rough,n : t rough,n =t mea,n,1 +x·T rep,1 =t mea,n,2 +y·T rep,2 Where, T rep,1 、T rep,2 are the repetition periods of the first and second optical pulse trains, τ mea,n,1 , τ mea,n,2 are the time difference of the first optical pulse sequence and the time difference of the second optical pulse sequence between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, respectively. x is The corresponding minimum positive integer solution, y is The corresponding smallest positive integer solution, τ Δn is the absolute optical delay of the nth optical link to be calibrated.

6. A broadband phased array optical delay calibration device, characterized in that: include: The signal generation module generates an optical signal by transmitting two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain in parallel. The optical signal is then split into two paths: one as a reference optical signal and the other as a detection optical signal. an optoelectronic conversion module for performing optoelectronic conversion on a reference optical signal and a detection optical signal after passing through the nth optical link to be calibrated of the broadband phased array, respectively, to obtain a reference photocurrent signal and a measurement photocurrent signal, where n = 1, 2, ..., N, where N is the total number of optical links to be calibrated of the broadband phased array; A digital processing module is used to convert the reference photocurrent signal and the measured photocurrent signal into the digital domain. In the digital domain, based on the optical domain vernier effect formed by the optical pulse sequence in the two polarization states, the unambiguous coarse delay of the nth optical link to be calibrated in the broadband phased array is obtained by solving the indeterminate equation. The calibration module is used to perform delay compensation on each optical link to be calibrated of the broadband phased array according to the deviation between the delay of each optical link to be calibrated of the broadband phased array and the set delay.

7. The optical delay calibration device for a broadband phased array according to claim 6, wherein: The digital processing module is further used to perform phase expansion on the unambiguous coarse delay of each optical link to be calibrated in the broadband phased array, and combine the carrier frequency phase shift of the two optical pulse sequences to obtain the precise delay of each optical link to be calibrated in the broadband phased array.

8. The optical delay calibration device for a broadband phased array according to claim 6 or 7, characterized in that: The parallel transmission of two optical pulse sequences with different time-frequency characteristics in two orthogonal polarization states in the optical domain is specifically achieved by the following method: using two electrical pulse signals with different time-frequency characteristics as modulation signals, intensity modulating the continuous single-frequency optical signal through a dual-polarization Mach-Zehnder modulator.

9. The optical delay calibration device for a broadband phased array according to claim 8, wherein: The expressions of the two electrical pulse signals with different time-frequency characteristics are: Wherein, a=1,2 is the serial number of the electric pulse signal; b is the pulse index number in the electric pulse signal; T rep,a is the repetition period of the ath electric pulse signal; T wid,a is the pulse width of the ath electrical pulse signal; f a is the carrier frequency of the ath electrical pulse signal; rect(t) is the pulse envelope function, which determines the amplitude envelope of the pulse. When |t|≤0.5, rect(t)=1, and when |t|>0.5, rect(t)=0.

10. The optical delay calibration device for a broadband phased array according to claim 6 or 7, characterized in that: The unambiguous rough delay of the nth optical link to be calibrated in the broadband phased array is obtained by the following method: the time difference between two different optical pulse sequences between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated is extracted using the cross-correlation algorithm, and then the unambiguous rough delay τ of the nth optical link to be calibrated is obtained by solving the following indeterminate equation: rough,n : t rough,n =t mea,n,1 +x·T rep,1 =t mea,n,2 +y·T rep,2 Where, T rep,1 、T rep,2 are the repetition periods of the first and second optical pulse trains, τ mea,n,1 , τ mea,n,2 are the time difference of the first optical pulse sequence and the time difference of the second optical pulse sequence between the measured photocurrent and the reference photocurrent in the nth optical link to be calibrated, respectively. x is The corresponding minimum positive integer solution, y is The corresponding smallest positive integer solution, τ Δn is the absolute optical delay of the nth optical link to be calibrated.

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