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Back to : Designing_252C Verifying | HomeKeysight TechnologiesDesigning, Verifying and Testing Stepped Frequency RadarSystems for Commercial and A/D Applications Application NoteIntroduction Stepped Frequency Radar (SFR) is well known for non-destructive testing and ground searching applications. With SFR, the echoes of stepped frequency pulses are synthesized in the frequency domain to obtain shorter pulses in the time domain. Using frequency hopping, both high resolution and a high signal-to-clutter ratio can be achieved. As a high range resolution radar technique, SFR offers a number of key advantages over other techniques like regular pulse radar. Such advantages include target classification, resolution of multiple targets, accurate range profile, detection of low radar cross section (RCS) targets in clutter, and low cost. Because of these advantages, SFR is today widely used in both the commercial and aerospace/defense (A/D) industries. This application note introduces a simulation platform--Keysight Technologies, Inc. SystemVue electronic system level (ESL) design software--which easily links to measurement tools to enable the design, validation and test of SFR systems under different environments. The simulation platform with test environment includes return signal RCS and background clutter. A template SFR design is also provided. SFR design is performed in SystemVue. Then, simulation results are evaluated with Tx and Rx measurements. Users can customize the template SFR design to their own systems and run simulations in the platform to evaluate the design's performance. The simulation platform also can be used as a test platform for SFR component test. As an example, an SFR system with target returns and ground clutter will be presented that uses the platform for both simulation and test. The proposed platform works very well for design, as well as for verification and testing of SFR systems. 03 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application Note Problem Solution As shown in Figure 1, SFR transmits sequences of N pulses at a Successfully designing, verifying and testing today's SFR systems fixed pulse-repetition frequency, but not at a fixed radar frequency. under different real-world environments requires a simulation Each pulse in the sequence of a stepped frequency waveform platform with links to a test environment that includes return has the same pulse width and time duration, but different carrier RCS and background clutter. One such solution is the SystemVue frequency. That frequency is given by f i = fo+N*dF, where dF is the ESL design software. As a comprehensive, model-based design amount of frequency increased, indicating that frequency hopping environment for challenging physical layer (PHY) communications and time division are used. systems, it integrates modeling, simulation, reference intellectual property (IP), hardware generation, and measurement links into a single, versatile development platform across RF and baseband domains that transitions easily from algorithms into hardwareFreq (HZ) verification. fN-i SystemVue's platform-based design approach produces increased, f fi early confidence that SFR system designs will not only work in the real world, but also achieve superior results, given available fo fo processing power, analog performance and environmental condi- time tions. Connecting measurement equipment to SystemVue via its T measurement links expands the concept to validation and test of SFR systems as well. NT Figure 1. Shown here is a typical SFR waveform. Using SystemVue, a working reference design of the SFR system is created and used to generate test vectors. The reference design Using this approach, SFR systems are able to overcome the power also processes received signals captured from live measurements. and bandwidth limitations of simple pulsed radar. Transmitting A signal generator and arbitrary waveform generator (AWG) then longer pulses extends their range capability, while also retaining render simulated signals for testing SFR hardware receivers and the wide bandwidth needed for high resolution. In any radar transmitters. A signal analyzer and signal analysis software (e.g., receiver, the received echo signals include both target returns Keysight's 89600 Vector Signal Analysis (VSA) software), capture and background clutter. In SFR radar, this clutter interferes with and analyze the signals. For further analysis and signal processing, target detection, making it difficult to find the actual number of measured signals can be brought back into SystemVue. targets or even fail to detect small targets. In this case, it is hard to find a closed-form analytical solution, and as a result, simulation becomes very important.04 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application NoteExample: Simulating a SFR SystemAs an example of how the SystemVue simulation platform canbe used to design, verify and test SFR systems, consider the SFRsystem designed in Figures 2 and 3. In the signal generator, a SFRsource is followed by an RF modulator, then two target models anda clutter model are set. The output of the signal generator simulatesthe SFR received signal, including target return and clutter.Figure 2. A stepped frequency radar simulation design is shown here. R1 ([email protected] Models) StepFreQType_Mode=Positive Hop PRF=10e3Hz Delta_Freq=4e6Hz NumOfSteqFreq=128 SampleRate=1e9HzFigure 3. Illustrated here is the step frequency signal generation model.05 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application NoteExample: Simulating a SFR System (continued)The received signal is measured at the input of the SFR receiverand displayed in Figure 4. Note that the plot of frequency versustime in Figure 4C is in keeping with what one would expect for theSFR signals based on the carrier frequency calculation previouslydescribed. The unwrapped phase is also to be expected. Additionally,simulation shows that the SFR receiver works fine.Figure 4. Shown here is the spectrum (A), magnitude of the waveform that reflects the random characters of thetarget return, as well as the clutter property (B), frequency hopping in the received signal (C), and the unwrappedphase (D) of a received SF radar signal measured at the receiver input.The SFR waveforms resulting from the design in Figure 2 areshown in Figure 5. Note that in the red waveform (the transmissionsignal), the frequency content for each pulse is different. This isbecause the frequency content increases with the timing. Theblue-colored waveform, the received RF signal, has a delay com-pared to the transmitted signal and is being affected by clutterand noise. The green-colored waveform is the demodulated signal.Figure 5. Shown here are transmitted (red), received (blue) and demodulated (green) SFR waveforms.06 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application NoteExample: Simulating a SFR System (continued)Using this high-resolution SFR design, two targets close to oneanother can be easily detected (Figure 6). To detect the sametwo targets using a pulse radar, the pulse width would have to beincreased at least 8 times, significantly increasing system cost.Figure 6. The high-resolution SFR design was used to detect these two targets near one anotherFigure 7. Shown here is a SFR receiver test signal generation for hardwaretest.Example: Testing a SFR SystemTesting the SFR hardware receiver requires a SFR signal generator.The received signal includes target returns with environments suchas ground clutter and noise.Figure 7 shows the creation of a SFR test signal with two targetsnear each other and clutter using SystemVue. The signal is down-loaded into a vector signal generator (e.g., Keysight's ESG/MXG/PSG Arb), via a vector signal generator link model, for upconversionto RF frequencies. The generated test signal is verified using asignal analyzer.07 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application NoteExample: Simulating a SFR System (continued)In Figure 8, the received SFR signal is measured at the input ofthe SFR receiver using a signal analyzer. Plot A shows the spec-trum, while Plot B shows the waveform that reflects the randomcharacters of the target returns and clutter property. To observethe frequency hopping in the received signal, look at the plotfrequency versus time (Plot C). In plot D, the unwrapped phase isdisplayed.Figure 8. Here, a generated SFR receiver test signal was measured by using Keysight's VSA software.For SFR transmitter test, a SFR receiver (created in SystemVue) isneeded. Using a VSA link, the received waveform from the signalanalyzer is acquired and sent into the SystemVue SFR receiver fordemodulation, detection and recovery of the original target signals.Figure 9 shows an actual software receiver that was created andcan be used to test real received SFR signals. DUTFigure 9. This test setup can be used for hardware test of the SFR transmitter and receiver.08 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application NoteSummary of ResultsThe low-cost, high range resolution SFR technique offers anumber of key advantages for non-destructive testing andground-searching applications in the commercial and A/Dindustries. However, quickly and accurately developing SFRsystems requires a simulation-based solution.The simulation platform presented here enables design, as wellas verification and test of SFR systems under different real-worldenvironments. SystemVue can provide both the software receiverto test a customer's transmitter and the software transmitter totest receiver components. Moreover, it provides the control andautomation that's critical for systems test. This capability, coupledwith the platform solution's flexibility and performance is key toallowing today's engineers to develop effective SFR systems withexcellent real-world performance.Related InformationSystemVue Radar application noteshttp://literature.cdn.keysight.com/litweb/pdf/5990-5392EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5990-5393EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5990-6919EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5990-8349EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5990-7533EN.pdfhttp://literature.cdn.keysight.com/litweb/pdf/5990-8556EN.pdfSystemVue Radar product informationW1905 Web page: http://www.keysight.com/find/eesof-systemvue-radar-libraryW1905 datasheet: http://literature.cdn.keysight.com/litweb/pdf/5990-6347EN.pdfYouTube video: http://www.youtube.com/watch?v=97Px9ByNyMIWebcast: "Uncovering the Hidden Impairments in Testing Advanced RADAR Systems"09 | Keysight | Designing, Verifying and Testing Stepped Frequency Radar Systems for Commercial and A/D Applications - Application Note myKeysight For more information on Keysight Technologies' products, applications or www.keysight.com/find/mykeysight services, please contact your local Keysight A personalized view into the information most relevant to you. office. 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