Direct Radar Signal Generation and Acquisition – Part 3

Direct Radar Signal Detection, Generation and Acquisition

Radar signal detection and generation has changed dramatically in the past 30 years. Today’s digital signal processing capabilities with modular high-speed AWGs and digitizers offer a wide range of possibilities to simulate radar signals and include simulated objects to verify the performance of a radar system

This direct radar signal generation and acquisition application note is Part 3 of a three part series. In part one of this radar series we provided an overview on the challenges that are introduced with modern radar signals and the instruments you can use to overcome them. In the second radar application note of this series you learned how to use various methods to create modern radar signals. This includes multi-channel RF generation for phased antennas, sequencing of various pulse patterns and how to deal with imperfections in signal generation through waveform correction.

In this third part of the radar application note series you will learn how to detect and digitize radar. This part covers bandwidth and storage requirements as well as analysis software to deeply analyze received radar signals.

Radar Signal Analysis: VSA, Scopes, and Digitizers

Analyzing Radar Signals has never been an easy task. In the past, only indirect measurements in the frequency domain using analog or digital swept spectrum analyzers were possible. The introduction of the Vector Spectrum Analyzer (VSA) changed the situation dramatically as those devices could capture the amplitude and phase characteristics of any RF signal within the analysis bandwidth.

Digitizers for RF Applications

Even when sampling rate or analog bandwidth are not a problem for the successful acquisition of an IF/RF signal, the large amount of waveform data generated in the process may be a challenge. In VSAs, the IF signal is digitized by two ADCs with identical sample rate, at least twice the IF bandwidth as required by the Nyquist Sampling Theorem. The two ADC paths represent the In-phase and Quadrature parts of the complex signal. When analysis bandwidth is lower than the maximum given by the Nyquist Theorem, a combination of a low-pass filter at each I/Q component and a down-sampling process can further reduce the amount of data created by the digitizer. In a Digital Sampling Oscilloscope (DSO) or digitizer, the complete IF/RF signal must be digitized, requiring a sampling rate at least twice the maximum frequency coverage of the original signal. Download Part 3: Direct Radar Signal Generation to see several approaches availalable to you to ease the problem described above.

Waveform Capture, Seamless Streaming, Continuous Storage

Many times, a thorough analysis of complex Radar or EW scenarios require extremely long captures without losing any events. The simplest way to do this is digitizing the complete radar signal for the duration of the experiment. No matter how long the internal acquisition memory is, when it is full, it is necessary to transfer the content to an external storage or processing device (i.e. a computer). As transfer time is usually much longer than acquisition time, the loss of events appearing during transfer is inevitable. In order to avoid this loss download this application note and learn several possible strategies.

Modern Radar Systems at a glance

In the first part of this series of three application notes we explained key elements that distinguish modern radar systems form historical pure analog radars systems. These new methods are pulse compression, ultra-high bandwidth in the multiple GHz range, high signal complexity by applying digital signal processing methods, and finally the application of phased array antennas, providing unmatched flexibility in antenna beam forming. 

Direct Radar Signal Generation and Acquisition – Part 1

In the second part we discussed the three basic methods of modern radar signal creation. This is creating the signal in the base band with following up-conversion in analog domain or generation the IF signal directly within an Arbitrary Waveform Generator also with follow-on analog up-conversion. 

Direct Radar Signal Generation and Acquisition – Part 2

Finally, if you have a very broad-band Arbitrary Waveform Generator you can directly create the FR radar signal in the Arbitrary Waveform Generator and feed it via an amplifier into an antenna or even in a phase array antenna. In this final third part of the series of application notes we focused on capturing radar signals with modern high bandwidth digitizers or real-time oscilloscopes. We discussed the bandwidth requirements and challenges when digitizing a radar signal and showed tools like VSA to deeply analyze the digitized radar signals. Especially with modular small form factor digitizer phased array antenna radar detection system can be easily realized. A set of AXIe modules consisting of M8131A digitizer, M8132A signal processor with customer programmable FPGA and the M8121A arbitrary waveform generator is available to detect, manipulate and re-sent radar signals in most flexible way.

Download this (Part 3) Radar Signal Detection and Acquisition Application Note.