Digital phased array optical fiber data transmission method

Abstract

The present application relates to a kind of digital phased array optical fiber data transmission methods in the field of phased array digital processing.The method frames data group in optical fiber transmission, digitalizes the problem of data deframing as geometric progression, realizes data group framing, data deframing with asynchronous FIFO, the FIFO depth needed is far less than data frame length, compared with ping-pong operation, can effectively reduce the demand of program to resource, it is favorable to the low-power design of digital receiving component, while it can improve the digital processing capacity of beam forming board card, improves the ability of digital multi-beam forming.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of digital phased array optical fiber data transmission method in the field of digital phased array. BACKGROUND

[0002] In current digital multi-beam phased array, the digital pre-processing of each array element channel data is usually completed in digital receiving assembly, and ping-pong operation is used when framing each array element channel data, two whole frame data are stored, and read-write operation is performed on two memories. Since the number of array element channels is large, a large amount of FPGA resources are occupied, which seriously affects the low-power and low-cost design of digital receiving assembly.

[0003] In the receiving end of beam forming board card, ping-pong operation is still used when framing, which occupies a large number of FPGA resources, seriously affects the digital processing capacity of beam forming board card, and restricts the number of digital multi-beam forming.

[0004] In order to reduce the resource demand of hardware board card and improve the efficiency of digital receiving assembly and beam forming board card, a new optical fiber data transmission method must be explored. SUMMARY

[0005] Therefore, the present application provides a digital phased array optical fiber data transmission method to solve the problems in the background art, which can effectively reduce the resource demand of hardware board card.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A digital phased array optical fiber data transmission method comprises the following steps:

[0008] (1) The digital receiving assembly filters, amplifies, down-converts and AD samples the radio frequency analog signals of each array element channel, and performs digital pre-processing in FPGA to obtain zero intermediate frequency complex signal data;

[0009] (2) The zero intermediate frequency complex signal data is subjected to data rate conversion through asynchronous FIFO to realize framing of the data, the framed data is subjected to electro-optical conversion, and the optical signal is output through optical fiber;

[0010] (3) After receiving the optical signal sent by the digital receiving assembly, the beam forming board card performs optical-electric conversion on the optical signal, and performs data rate conversion through asynchronous FIFO in FPGA to complete the framing of the data, and obtains zero intermediate frequency complex signal data of each array element channel;

[0011] (4) According to the beam pointing and array element coordinates, the weight corresponding to each array element channel is calculated, and the zero intermediate frequency complex signal data of each array element channel is weighted and summed to obtain the data after beam synthesis;

[0012] (5) The data after beam synthesis is subjected to data rate conversion through asynchronous FIFO to realize data framing, and the framed data is subjected to electro-optical conversion and output to a subsequent processing terminal through optical fiber.

[0013] Further, in step (2) and step (5), when the data is framed, the asynchronous FIFO continuously writes and intermittently reads, the writing clock is clk, the reading clock is clk z , and clk z , after a0 data are stored in the FIFO, reading is started, after reading the data stored in the current FIFO, the newly written data is a0q n , q = clk z / clk, n is the reading times, that is, the remaining data in the FIFO conforms to a geometric progression, after n reading processes, reading is stopped, until a0 data are stored in the FIFO again to start reading; wherein a0 satisfies the following formula:

[0014]

[0015] In the formula, L is the data content length in each frame, n is the minimum value satisfying the above formula, and the depth of the FIFO is greater than a0, so that the FIFO is not emptied.

[0016] Further, in step (3), when the data is deframed, the asynchronous FIFO intermittently writes and continuously reads, the writing clock is clk z , the reading clock is clk, and clk z , after b0 data are stored in the FIFO, reading is started, after reading the data stored in the current FIFO, the newly written data is b0p n , p = clk z / clk, n is the reading times, that is, the newly written data in the FIFO conforms to a geometric progression, after L data are continuously written, writing is stopped; after waiting for the next frame of data, writing is restarted; wherein b0 satisfies the following formula:

[0017]

[0018] In the formula, L is the data content length in each frame, n is the minimum value satisfying the above formula, and the depth of the FIFO is greater than (b0+L·(p-1)), so that the FIFO is not filled.

[0019] b0p n ≤b0+L·(p-1)

[0020] The depth of the FIFO is greater than (b0+L·(p-1)), so that the FIFO is not filled.

[0021] Compared with the background art, the present application has the following advantages:

[0022] 1. Digitize the framing problem in fiber optic transmission and use asynchronous FIFO to achieve data framing. The FIFO depth is much smaller than the data frame length, which effectively reduces the program's resource consumption.

[0023] 2. The frame de-framing problem in optical fiber transmission is digitized, and asynchronous FIFO is used to implement data frame de-framing. The FIFO depth is much smaller than the data frame length, which effectively reduces the program's resource consumption.

[0024] 3. The saved resources can be used to enhance digital multibeamforming capabilities. Attached Figure Description

[0025] Figure 1 This is a block diagram illustrating the composition principle of the present invention.

[0026] Figure 2 This is the high-speed data frame structure of the present invention. Detailed Implementation

[0027] Reference Figure 1 , Figure 2 The present invention will now be further described.

[0028] A digital phased array fiber optic data transmission method, such as Figure 1 As shown, it includes the following steps:

[0029] (1) The digital receiving component filters, amplifies, downconverts and AD samples the radio frequency analog signals of each array element channel, and performs digital preprocessing in the FPGA to obtain zero intermediate frequency complex signal data;

[0030] Inside the receiving component, the radio frequency analog signal (center frequency f0) is transmitted through the local oscillator signal f. b The frequency is down-converted to the intermediate frequency, and then sampled by an AD converter (sampling frequency is f). s The sampling period is T s After that, the center frequency f z for:

[0031] f z =f0-f b -f s

[0032] The sampled digital intermediate frequency real signals of each array element can be expressed as:

[0033] x l (nT s )=s(nT s cos(2πf) z / f s n-2πf0α T r l l=1,2,...,N

[0034] wherein n represents a time variable, s(nT s ) represents a baseband signal, (·) T represents a transpose, N represents a number of array element channels, r l is an array element position coordinate:

[0035] r l = (x l , y l , z l ) T , l = 1, 2, …, N

[0036] α is a slow vector:

[0037]

[0038] wherein c is a light speed, θ and are a bearing angle and a pitch angle of an incoming wave respectively.

[0039] After orthogonal down-conversion and low-pass filtering, a real part of a zero intermediate frequency complex signal data of the lth array element can be represented as:

[0040]

[0041] An imaginary part of the zero intermediate frequency complex signal data of the lth array element can be represented as:

[0042]

[0043] The real part is rounded to 16 bits and placed in a high byte, and the imaginary part is rounded to 16 bits and placed in a low byte, to form the zero intermediate frequency complex signal data;

[0044] (2) The zero intermediate frequency complex signal data is subjected to data rate conversion through an asynchronous FIFO to realize framing of the data, and the framed data is subjected to electro-optical conversion and output through an optical fiber as an optical signal;

[0045] A fiber data transmission frame structure is shown in Figure 2 . Wherein the frame header and the frame tail are defined as 0x1ACFFC1D; the frame length is an actual frame data content length L; wherein the time stamp represents a count within a second, used to realize synchronization of multiple different frame data at the same time.

[0046] When the data is framed, the asynchronous FIFO continuously writes at a low speed and intermittently reads at a high speed, and it is necessary to consider whether the FIFO will be read empty. The write clock is clk, the read clock is clk z , the data content length in each frame is L, a0 data are stored in the FIFO after which reading starts, after a0 data are read, a0·q data are written, wherein q = clk / clk z, that is, the remaining data in the FIFO conforms to a geometric progression, and the reading stops after n reading processes, and restarts after a0 data are stored in the FIFO; where a0 satisfies the following formula:

[0047]

[0048] n takes the minimum value satisfying the above formula, and the depth of the FIFO is greater than a0, so that the FIFO is not emptied.

[0049] (3) After the beam forming board card receives the optical signal sent by the digital receiving component, the optical signal is optoelectronic converted, and the data rate conversion is performed in the FPGA through the asynchronous FIFO, the data is de-framed, and the zero intermediate frequency complex signal data of each array element channel is obtained;

[0050] When the data is de-framed, the asynchronous FIFO writes intermittently at high speed and reads continuously at low speed, and whether the FIFO is full needs to be considered. The write clock is clk z , the read clock is clk, the data content length in each frame is L, b0 data are stored in the FIFO to start reading, and after b0 data are read, b0·p data are written, where p = clk z / clk, that is, the re-written data in the FIFO conforms to a geometric progression, and the writing stops after L data are continuously written, and the writing restarts after the next frame of data arrives; where b0 satisfies the following formula:

[0051]

[0052] n takes the minimum value satisfying the above formula, and the following can be obtained:

[0053] b0p n ≤b0+L·(p-1)

[0054] The depth of the FIFO is greater than (b0+L·(p-1)), so that the FIFO is not full.

[0055] (4) According to the beam pointing and array element coordinates, the weight corresponding to each array element channel is calculated, and the zero intermediate frequency complex signal data of each array element channel is weighted and summed to obtain the data after beam synthesis;

[0056] (5) The data after beam synthesis is subjected to data rate conversion through the asynchronous FIFO, the data is framed, the framed data is optoelectronic converted, and the optical signal is output to the next stage processing terminal through the optical fiber. The framing method of the data is the same as that in step (2).

Claims

1. A digital phased array optical fiber data transmission method, characterized by, The method comprises the following steps: (1) The digital receiving assembly filters, amplifies, down-converts and AD samples the radio frequency analog signals of each array element channel, and performs digital pre-processing in the FPGA to obtain zero intermediate frequency complex signal data; (2) The zero intermediate frequency complex signal data is subjected to data rate conversion through an asynchronous FIFO to realize data framing, and the framed data is subjected to electro-optical conversion and output through an optical fiber; (3) After receiving the optical signal sent by the digital receiving assembly, the beam forming board card performs photoelectric conversion on the optical signal, and performs data rate conversion through an asynchronous FIFO in the FPGA to complete data deframing, thereby obtaining zero intermediate frequency complex signal data of each array element channel; (4) According to the beam pointing and array element coordinates, the corresponding weight of each array element channel is calculated, and the zero intermediate frequency complex signal data of each array element channel is weighted and summed to obtain data after beam synthesis; (5) The data after beam synthesis is subjected to data rate conversion through an asynchronous FIFO to realize data framing, and the framed data is subjected to electro-optical conversion and output through an optical fiber to a subsequent processing terminal; In the step (2) and step (5), the asynchronous FIFO continuously writes and discontinuously reads when framing the data, the writing clock is clk, the reading clock is clk z , and clk z , after a0 data are stored in the FIFO, the reading is started, after the data stored in the current FIFO are read, the re-written data is a0q n , q = clk / clk z , n is the reading times, that is, the re-written data in the FIFO conforms to the geometric progression; In step (3), the data is de-framed, the asynchronous FIFO writes intermittently and reads continuously, the write clock is clk, and the read clock is clk z , and clk z < clk, after b0 data is stored in the FIFO, the reading starts, after the data stored in the current FIFO is read, the newly written data is b0 p n , p = clk / clk z , n is the reading times, that is, the newly written data in the FIFO conforms to the geometric progression.

2. A digital phased array optical fiber data transmission method according to claim 1, wherein, In steps (2) and (5), after n reading processes, the reading is stopped until a0 data are stored in the FIFO, and then the reading is restarted; wherein a0 satisfies the following formula: In the formula, L is the data content length in each frame, n is the minimum value satisfying the above formula, and the depth of the FIFO is greater than a0, so that the FIFO cannot be read empty.

3. A digital phased array optical fiber data transmission method according to claim 1, wherein, In step (3), after L data are continuously written, the writing is stopped, and the writing is restarted after the next frame of data arrives; wherein b0 satisfies the following formula: In the formula, L is the data content length in each frame, n is the minimum value satisfying the above formula, and the depth of the FIFO is greater than (b0+L·(p-1)), so that the FIFO cannot be written full. b0p n ≤ b0+ L · (p - 1) ​

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