CN112688671A

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Info

Publication number: CN112688671A
Application number: CN202011277466.8A
Authority: CN
Inventors: 全大英; 邢国鹏; 俞晨斌; 金小萍
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2020-11-16
Filing date: 2020-11-16
Publication date: 2021-04-20

Abstract

本发明提供了一种线性调频脉冲发生装置，包括一个脉冲计时器、一个时间频率变换表、一个线性调频相位生成器、一张频率响应查找表、一个数字频率合成器(DDS)和一个乘法器，本发明解决了FPGA实现的线性调频脉冲发生装置的带内不平度补偿中运算量巨大的问题，具有易于实现、计算量小、补偿后平坦度好的特点，满足超大带宽、超高精度的线性调频脉冲产生的需求。

The invention provides a chirp pulse generating device, comprising a pulse timer, a time-frequency conversion table, a chirp phase generator, a frequency response look-up table, a digital frequency synthesizer (DDS) and a multiplier The invention solves the problem of huge calculation amount in the in-band unevenness compensation of the linear frequency modulation pulse generating device realized by FPGA, has the characteristics of easy implementation, small calculation amount and good flatness after compensation, and meets the requirements of ultra-large bandwidth and ultra-high precision. Chirp generation needs.

Description

Linear frequency modulation pulse generating device

Technical Field

The invention relates to the technical field of signal generation applied to communication and radar equipment, in particular to a linear frequency modulation pulse generating device.

Background

Chirp signals have a number of applications in ultra-wideband communications and high-resolution, low-probability-of-intercept radars. As the system bandwidth increases, the frequency response of the chirp pulse generator varies to affect the communication and target detection performance of the system, so that the frequency response of the transmitter needs to be compensated. The traditional compensation method needs frequency domain or time domain equalization in the whole bandwidth, and the computation amount is huge. Especially, in the case of GHz level signal bandwidth, a large amount of computing resources are consumed.

In order to make up for the deficiency of the existing scheme in terms of calculation amount, it is necessary to invent a device which is easy to implement, small in calculation amount and good in flatness after compensation so as to meet the requirements of communication and radar equipment on a high-precision linear frequency modulation signal generator.

Disclosure of Invention

The invention aims to provide a linear frequency modulation pulse generating device, which solves the problem of huge calculation amount in-band unevenness compensation of the linear frequency modulation pulse generating device realized by an FPGA. Therefore, the invention adopts the following technical scheme:

1-a) a pulse timer, whose function is to generate a pulse start time and to generate an intra-pulse time scale in units of sampling rate; the intra-pulse time scale refers to the sampling time inside the generated linear frequency modulation digital pulse;

the pulse timer is limited by the main frequency of the FPGA and needs to work in parallel, namely, a plurality of sampling moments are output at the working clock beat of each FPGA;

1-b) a time-frequency conversion table for calculating the instantaneous frequency of the chirp signal following the variation of the time within the pulse; the specific calculation formula is as follows:

f_rt＝gama*t_s

wherein is t_sAt the sampling moment, gama is the chirp rate of the chirp signal, f_rtThe signal frequency corresponding to the sampling moment;

1-c) a chirp phase generator for generating a chirp signal instantaneous phase from the intra-pulse time scale and the chirp signal instantaneous frequency; the linear frequency modulation phase generator adopts a linear frequency modulation signal generation formula during calculation, or adopts a two-stage accumulator to realize the calculation;

1-d) a frequency response look-up table for use in signal generation for frequency response look-up of a system of signal transformation, filtering and DAC hardware circuits; the frequency response lookup table takes the instantaneous frequency of the linear frequency modulation signal corresponding to the intra-pulse time scale as input, takes the frequency response coefficient of the corresponding frequency point as output, and obtains the frequency response coefficient by searching the lookup table according to the instantaneous frequency of the linear frequency modulation signal;

the generation method of the frequency response lookup table comprises three steps: a first step) calculating a frequency sampling interval according to a chirp sampling rate; second step) generating a single-frequency signal of a frequency sampling point, and further testing the frequency characteristic of each sampling frequency point; third step) storing and forming a frequency characteristic table;

1-e) a digital frequency synthesizer DDS for searching sine and cosine tables according to the instantaneous phase of the linear frequency modulation signal to generate a standard pulse waveform of the linear frequency modulation signal;

1-f) a multiplier for real-time frequency characteristic modulation, i.e. multiplying the frequency response coefficient obtained by table lookup to the generated standard chirp signal pulse shape.

The linear frequency modulation pulse generating device only adopts one multiplier to replace the calculation of an equalizing filter of a time domain or a frequency domain aiming at the characteristics of linear frequency modulation signals, is easy to realize and has small calculation amount; according to actual needs, different sampling rates can be selected and adopted, the requirements of ultra-large bandwidth and ultra-high precision on in-band flatness can be met, and the method is good in flexibility and high in precision.

Drawings

Fig. 1 is a block diagram of a chirp generation device according to the present invention.

Fig. 2 is a flowchart of a method for generating a frequency response lookup table according to the present invention.

Detailed Description

In order to fully understand the technical content of the present invention, specific embodiments are given below, and the technical solution of the present invention is described and explained in more detail with reference to the accompanying drawings.

Fig. 1 is a block diagram of a chirp generator according to the present invention, which includes a pulse timer 11, a time-frequency conversion table 12, a frequency response look-up table 13, a chirp phase generator 14, a digital frequency synthesizer DDS 15, and amultiplier 16.

The time-frequency conversion table 12 and the frequency response look-up table 13 are stored in different storage units, respectively.

The pulse timer 11 is connected with a memory for storing a time frequency conversion table 12 and a linear frequency modulation phase generator 14, and provides an intra-pulse time scale for the time frequency conversion table and the linear frequency modulation phase generator; the memory storing the time frequency translation table 12 is connected to a chirp phase generator 14, said chirp phase generator 14 retrieving the chirp instantaneous frequency from the time frequency translation table 12; the chirp phase generator 14 is connected to a digital frequency synthesizer (DDS)15, and provides a chirp signal instantaneous phase to the digital frequency synthesizer (DDS) 15; the digital frequency synthesizer (DDS)15 is connected to amultiplier 16, and provides a standard chirp waveform to themultiplier 16; the memory storing the frequency response look-up table 13 is connected to amultiplier 16, said multiplier 16 reading out the frequency response coefficients from the frequency response look-up table 13; themultiplier 16 is often complex.

The time frequency conversion table 12 provides a comparison relation of the instantaneous frequency of the linear frequency modulation signal along with the change of the intra-pulse time scale, the input is the intra-pulse time scale, and the output is the instantaneous frequency of the linear frequency modulation signal; the frequency response lookup table 13 provides a comparison relationship of the system frequency response coefficient with the change of the instantaneous frequency of the chirp signal, the input is the instantaneous frequency of the chirp signal, and the output is the system frequency response coefficient.

The pulse timer 11 is used for generating a pulse starting time and generating an intra-pulse time scale by taking a sampling rate as a unit; the intra-pulse time scale is the sampling time inside the generated linear frequency modulation digital pulse; the pulse timer needs to work in parallel, namely, a plurality of sampling moments are output at the working clock beat of each FPGA.

A time-frequency conversion table 12 for calculating the instantaneous frequency of the chirp signal following the variation of the time within the pulse; the specific calculation formula is as follows:

f_rt＝gama*t_s

wherein is t_sAt the sampling moment, gama is the chirp rate of the chirp signal, f_rtIs the signal frequency corresponding to the sampling time.

The chirp phase generator 14 is operative to generate a chirp signal instantaneous phase from the intra-pulse time scale and the chirp signal instantaneous frequency; the calculation of the linear frequency modulation phase generator adopts a linear frequency modulation signal generation formula, or adopts a two-stage accumulator to realize.

A frequency response lookup table 13, which is used as a frequency response lookup table of a system composed of signal transformation, filtering and DAC hardware circuits in signal generation; the frequency response lookup table takes the instantaneous frequency of the linear frequency modulation signal corresponding to the intra-pulse time scale as input and takes the frequency response coefficient of the corresponding frequency point as output; the frequency response coefficient is obtained by retrieving the look-up table based on the chirp signal instantaneous frequency.

The method for generating the frequency response lookup table 13, as shown in fig. 2, includes three steps: a first step (21) of calculating a frequency sampling interval based on a chirp sampling rate; a second step (22) of generating a single-frequency signal of a frequency sampling point, and further testing the frequency characteristic of each sampling frequency point; the third step (23) is to store and form a frequency characteristic table, namely a frequency response lookup table.

The digital frequency synthesizer DDS 15 is used for searching sine and cosine tables according to the instantaneous phase of the linear frequency modulation signal to generate a standard pulse waveform of the linear frequency modulation signal;

themultiplier 16 is used for real-time frequency characteristic modulation, namely multiplying a frequency response coefficient obtained by table lookup to the generated standard linear frequency modulation signal pulse waveform; multipliers often take the form of complex numbers.

It should be understood that the technical contents of the present invention are further disclosed from the perspective of specific embodiments, which aim to make the contents of the present invention easier to understand, but do not represent embodiments of the present invention and the rights are not limited thereto. The scope of the invention is set forth in the appended claims and all obvious modifications which are within the spirit of the invention are intended to be embraced therein.

Claims

Translated fromChinese

1.一种线性调频脉冲发生装置，其特征在于包括以下五个组成部分：1. A linear frequency modulation pulse generating device is characterized in that comprising the following five components:

1-a)一个脉冲计时器，其作用是产生脉冲起始时刻，并以采样率为单位产生脉内时间刻度；所述脉内时间刻度，是指所产生的线性调频数字脉冲内部的采样时刻；1-a) A pulse timer, the function of which is to generate the pulse start time, and to generate an intra-pulse time scale in units of sampling rate; the intra-pulse time scale refers to the sampling time inside the generated chirp digital pulse ;

所述脉冲计时器，受限于FPGA的主频，需要并行工作，即在每个FPGA工作时钟节拍输出多个采样时刻；The pulse timer is limited by the main frequency of the FPGA and needs to work in parallel, that is, to output multiple sampling moments in each FPGA working clock beat;

1-b)一个时间频率变换表，用作线性调频信号瞬时频率跟随脉内时刻变化的计算；具体计算公式为：1-b) A time-frequency conversion table, which is used for the calculation of the instantaneous frequency of the chirp signal following the time change in the pulse; the specific calculation formula is:

f_rt＝gama*t_sfr_rt = gama*t_s

其中为t_s采样时刻，gama为线性调频信号调频斜率，f_rt为采样时刻对应的信号频率；where_ts is the sampling time, gama is the FM slope of the chirp signal, and_frt is the signal frequency corresponding to the sampling time;

1-c)一个线性调频相位生成器，用作根据脉内时间刻度和线性调频信号瞬时频率生成线性调频信号瞬时相位；所述线性调频相位生成器计算时采用线性调频信号生成公式，或者采用两级累加器实现；1-c) A chirp phase generator for generating the instantaneous phase of the chirp signal according to the intra-pulse time scale and the instantaneous frequency of the chirp signal; the chirp phase generator uses the chirp signal generation formula for calculation, or uses two Stage accumulator implementation;

1-d)一张频率响应查找表，用作信号产生中信号变换、滤波和DAC硬件电路组成的系统的频率响应查表；所述频率响应查找表以脉内时间刻度对应的线性调频信号瞬时频率为输入，以对应频点的频率响应系数为输出，根据线性调频信号瞬时频率，通过检索该查找表得到频率响应系数；1-d) A frequency response lookup table, used as the frequency response lookup table of the system composed of signal conversion, filtering and DAC hardware circuit in signal generation; the frequency response lookup table is based on the instantaneous time scale of the chirp signal corresponding to the pulse time scale. The frequency is the input, the frequency response coefficient of the corresponding frequency point is the output, and the frequency response coefficient is obtained by retrieving the lookup table according to the instantaneous frequency of the chirp signal;

所述频率响应查找表的生成方法包括三个步骤：第一步)根据线性调频脉冲采样率，计算频率采样间隔；第二步)生成频率采样点单频信号，进而测试每个采样频点的频率特性；第三步)存储形成频率特性表格；The generation method of the frequency response lookup table comprises three steps: the first step) according to the chirp sampling rate, calculate the frequency sampling interval; the second step) generate the frequency sampling point single frequency signal, and then test the frequency of each sampling frequency point. frequency characteristic; the third step) storage to form a frequency characteristic table;

1-e)一个数字频率合成器DDS，用于根据线性调频信号瞬时相位，查找正弦和余弦表格，生成标准的线性调频信号脉冲波形；1-e) a digital frequency synthesizer DDS for looking up a sine and cosine table according to the instantaneous phase of the chirp signal, and generating a standard chirp signal pulse waveform;

1-f)一个乘法器，用于实时频率特性调制，即将查表得到的频率响应系数乘到所生成的标准的线性调频信号脉冲波形。1-f) A multiplier for real-time frequency characteristic modulation, that is, multiplying the frequency response coefficient obtained by looking up the table by the generated standard chirp signal pulse waveform.

2.如权利要求1所述的一种线性调频脉冲发生装置，其特征在于该装置可以完成带内不平度补偿的信号带宽高达GHz级别，满足超大带宽、超高精度的线性调频脉冲产生的需求。2. A kind of chirp generating device as claimed in claim 1, it is characterized in that this device can complete the signal bandwidth of in-band unevenness compensation up to GHz level, and meet the needs of ultra-large bandwidth, ultra-high-precision chirp generation .