Abstract: To address the poor versatility of traditional dedicated radar signal generation systems, a general-purpose analog radar signal generation system is proposed based on virtual instrument technology, integrating an arbitrary waveform generator and a vector signal source. Using the Agilent VEE design program, the system is centrally controlled and managed through a user-friendly control panel, allowing for flexible setting of waveforms, waveform parameters, center frequency, and output power. Furthermore, it facilitates system integration and expansion. Keywords: Virtual Instrument, VEE, Radar, Arbitrary Waveform Generator, Vector Signal Generator Abstract: Traditional application-specific radar signal generators had a great limitation on application; we proposed a simulated system based on a virtual instrument for radar signal generation, which integrated an arbitrary waveform generator and a vector signal generator. We employed Agilent VEE for remote system control via the soft panel of the program, which was convenient for adjusting waveform, carrier frequency, output power, and system updates. Keywords: VEE, Virtual Instrument, Radar, Arbitrary Waveform Generator, Vector Signal Generator 1 Introduction Traditional radar transmitters use dedicated signal generation modules, which cannot arbitrarily set waveform forms, parameters, signal center frequency, signal power, etc. This limits the scope of application to a certain extent. Especially in the pre-research and exploration stages of radar and new technologies, it is necessary to experiment or evaluate various radar signals. Designing a dedicated signal generation module for each radar signal would be extremely costly. If virtual instrument technology is used, high-performance commercial test instruments[1] can be integrated, and the functions of the system can be designed through programming. Various radar signals can be effectively simulated, and the parameters of the radar signals can be set with greater flexibility, overcoming the problem of poor universality and meeting a variety of application requirements. 2 Radar signal generation system The block diagram of the radar signal generation principle is shown in Figure 1. The baseband signal generation module uses D/A conversion to convert the digital stored waveform into I/Q two-channel baseband analog signal output. The I/Q modulation module modulates the I/Q two-channel signals with orthogonal carriers, shifting the signal center frequency to the radio frequency or microwave frequency band. The final output of the system is the required radar signal. [align=center] Figure 1. Radar signal generation principle diagram[/align] 3 Radar signal simulation system based on virtual instruments In the pre-research and demonstration stage of the new radar system, the radar signal generation system based on virtual instruments can meet the application requirements. Using arbitrary waveform generator, vector signal source and pulse signal source as hardware platform, virtual instrument software is developed under Agilent VEE for control, realizing the simulation of a general radar signal generation system. 3.1 System Hardware Structure Design The system structure diagram is shown in Figure 2. The functions of each module are described below. [align=center] Figure 2. Instrument Hardware Connection[/align] 3.1.1 Arbitrary Waveform Generator The arbitrary waveform generator completes the output of baseband or intermediate frequency analog IQ signals through digital storage and digital-to-analog conversion. Through software control, the arbitrary waveform generator simulates the baseband analog signal generation module, achieving the following functions: 1. Playback control of the pulse waveform output, realizing the output of single pulse waveforms or pulse waveform sequences. 2. The pulse time width and waveform parameters within the pulse (such as frequency or bandwidth) can be set. 3. The pulse time width and resampling rate can be set through software. 3.1.2 Vector Signal Source The vector signal source inputs I/Q signals to complete quadrature modulation and up-conversion. Through remote control, the following functions are achieved: 1. The output radar signal center frequency and output power can be adjusted. 2. The amplitude and phase balance of the I/Q branches can be adjusted. 3.1.3 Pulse Generator The pulse generator can provide the required trigger pulse for radar pulse modulation and set the pulse repetition frequency (PRF). It realizes the coherence and synchronization between various modules. The key modules in the above system are the arbitrary waveform generator and the vector signal source. Major instrument manufacturers have corresponding products. In order to verify the implementation of the system, we selected the Agilent Technologies' arbitrary waveform generator N6030A[2] and vector signal source E8267D[3], and selected the company's 81110A pulse generator[4] as the pulse source. Among them, 81110A and E8267D are connected to the industrial control computer through the GPIB bus, while N6030A is connected to the industrial control computer through the PXI bus. The industrial control computer runs the virtual instrument software and communicates with each instrument through the PXI bus and GPIB bus respectively to realize the remote control of the instrument. 3.2 Virtual Instrument Software Design The system software composition is shown in Figure 3. It adopts a modular program structure, which facilitates the upgrade and expansion of the system. The instrument driver is a collection of instrument function control functions and instrument parameter variables. The instrument control module is a subset of the instrument driver defined by the program. It extracts the instrument function functions and parameters required to build the system from the driver to suit the user's needs. [align=center] Figure 3. System software composition block diagram[/align] 3.2.1 VEE graphical development environment The virtual instrument development environment includes common application development environments such as VC++, VB, MATLAB, and graphical development environments specifically for test and measurement applications such as NI LabVIEW, Agilent VEE, etc. In the development process, the Agilent VEE (Virtual Engineering Environment) development environment is selected [5]. VEE adopts object-oriented programming technology and is suitable for system simulation and instrument optimization control in the field of test and measurement. Its main features are: graphical processing of programming language, writing code in the form of data flow diagram, and high programming efficiency. It provides rich instrument I/O drivers to control bus interfaces such as VXI, GPIB, PXI, and serial port. It provides a large number of function libraries and can be mixed with C/C++, MATLAB, etc. 3.2.2 Design of Instrument Control Module Based on Driver The instrument driver is a collection of control functions and parameters that realize the functions of the instrument. It is the bridge between the software and the instrument. Instruments are all accompanied by corresponding drivers when they are produced, and virtual instrument software is built on the instrument driver [6]. By receiving the user setting parameters from the user operation panel, it realizes rich signal setting functions and completes the task of automatic control. By calling the interface functions of the instrument driver [7], [8], [9], a system that meets the functional requirements can be designed. Figure 4 illustrates the software flow. The functions of the software include instrument addressing, inter-instrument coherent setting, resampling clock setting, output power configuration of each stage, selection of trigger source, configuration of trigger pulse PRF value, configuration of output signal center frequency, signal waveform modeling, data generation and storage, and waveform output playback control. The waveform playback control part is a subprocess, and its flowchart is shown in Figure 5. Its function is to control the waveform playback process of arbitrary waveform generator by calling the function of arbitrary waveform generator driver. The two branches realize the output of single pulse waveform and the output of pulse waveform sequence, respectively. [align=center] Figure 4. Virtual Instrument Program Execution Flowchart[/align] [align=center] Figure 5. Waveform Playback Flowchart[/align] Figure 6 shows the image of the I/Q two-line linear frequency modulated baseband (-300～+300MHz) analog signal output by the arbitrary waveform generator in single waveform output mode, under the control of the trigger pulse of PRF = 2000KHz, displayed on a digital storage oscilloscope. The trigger pulse width is 300us, and the pulse waveform width is 16us. [align=center] a. Time axis resolution 100us/division b. Time axis resolution 2.00us/division Figure 6. Linear Frequency Modulated Signal and Trigger Pulse[/align] 4 Conclusion The radar signal simulation system based on virtual instruments has the following innovations compared with the previous dedicated radar signal system: 1) Versatility: The waveform signal form, center frequency, power, pulse repetition frequency, etc. can all be set very flexibly. 2) Software-defined system functions facilitate system upgrades and easy integration of other instruments into the system, expanding system functionality. 3) Make full use of laboratory resources to reduce R&D costs and cycle, applicable to the R&D and experimental stages of new radar system architecture. References [1]. Wang Jun, Chi Qinhe, Speed ​​Radar Signal Processing System Based on Virtual Instrument Technology, Microcomputer Information, 2003, Vol. 19 [2]. Agilent Technology, Overview of N6030A Arbitrary Waveform Generator Technology [3]. Agilent Technology, Technical Data of E8267D PSG Vector Signal Generator [4]. Agilent Technology, Technical Data of 81110 Pulse Code Generator [5]. Robert Helsel, HP VEE Visual Programming 3rd Edition, China-HP DSP Technology Research Center, Tsinghua University Press, 1999 [6]. Zhao Huibing, Virtual Instrument Technical Specifications and System Integration, Tsinghua University Press, 2003 [7]. Agilent Technology, N6030A Users' Guide [8]. Agilent Technology, E8267D PSG Signal Generators Programming Guide [9]. Agilent Technology, 81110A Reference Guide