An integrated RF system design platform enables radar developers to explore various architectural options, signal processing algorithms, RF component requirements, and target/environment factors. Using high-level behavioral RF/digital signal processing (DSP) models, designers can quickly implement a virtual radar system to investigate tradeoffs between choice of waveform, RF-component selection, and antenna details. Developing phased-array antennas for radars utilizing MIMO and beam-steering technology requires special design tools to design the array configuration, antenna elements, and feed network, along with a platform that can incorporate this simulation data into the larger radar simulation. As the desired simulated radar performance is achieved, the platform should support co-simulation with circuit and antenna electromagnetic (EM) analysis to transition from conceptual design to physical realization.
Maximizing radar performance requires thorough analysis and optimization of each subassembly and component in the system. Designers require specific simulation technologies to capture and analyze time-domain, pulsed and modulated frequency responses, link budget (power, noise), and spurious signals in order to predict the overall radar performance, inclusive of device nonlinearities and chain impairments. Simulation must incorporate signal generation, transmission, antenna, T/R switching, clutter, noise, jamming, receiving, signal processing for moving target-indication (MTI) and moving-target detection (MTD), constant false-alarm rate (CFAR), and channel propagation.
Commercial and defense radar systems operating in the millimeter-wave (mmWave) spectrum and utilizing advanced semiconductor and integration technologies are being driven by new size and performance requirements. System designers require a comprehensive system model library that includes RF behavioral, file, and circuit-based models and DSP components for simulating different fixed-point formats, as well as antenna, radar-cross section (RCS) target and propagation models for multi-path fading, Doppler shift, RF clutter, jamming, and more.
Designers often rely on existing architectures, waveforms, and known component specs to define their initial system and simulation setup in order to expedite radar system development and perform critical measurements. Depending upon the application, developers may choose a continuous wave (CW) radar for a radio altimeter or proximity sensor, a frequency-modulated CW (FMCW) radar for automotive, or pulsed radar for synthetic aperture and weather tracking. Pre-configured simulation radar examples allow developers to adopt existing systems and modify them to a particular application and test benches enable them to perform parametric tests on individual circuit modules, including benchmarks such as noise figure (NF), gain, voltage standing-wave ratio (VSWR), intermodulation distortion, and more. In addition, functional performance simulation examples guide developers conducting more rigorous end-to-end system evaluation, enabling them to understand the response to factors such as multiple targets, clutter, jamming, and noise.
The benefits of MIMO and beam-steering phased-array systems over omni-directional antennas include higher directivity, fast-electronic steering (beams that can be re-directed in milliseconds), and the ability to emit multiple beams simultaneously for multifunctional operations. Simulation tools need to support these antenna designs and array configurations, allowing interactive specification of the layout, feed network details, RF-link settings, gain tapers, and element failures. With hierarchical EM analysis that ensures the proper design and placement of antennas and mounting structures, in-situ circuit co-simulation enables radar designers to study the interactions between antenna arrays and the RF front-end circuitry.
This 2.4 GHz radar based on the Massachusetts Institute of Technology (MIT) OpenCourseWare (OCW) online course, was built with widely-available low-frequency Wi-Fi components. The intermediate frequency (IF) baseband signal from the radar unit was amplified and filtered using breadboard components and a laptop was used to sample the down-converted spectrum. NI AWR software was used to re-design the radar using smaller, less expensive surface-mount technology (SMT) components, including a voltage controlled oscillator (VCO), attenuator, power amplifier (PA), 3-dB coupler, low-noise amplifier (LNA), and mixer. This homodyne system self-mixed for its downconversion so that the IF spectrum could be sampled by the PC.
Advance driver-assist system (ADAS) technology based on 77 GHz radar utilize smaller antennas (one-third of the size of the current 24-GHz ones), higher permitted transmit power, and, most importantly, wider available bandwidth, to enable higher object resolution. NI AWR software provides RF-aware system design software that supports radar simulations with detailed analysis of RF front-end components, including nonlinear RF chains, advanced antenna design, and channel modeling. Co-simulation with circuit and EM analysis provides accurate simulation of system performance prior to building and testing, all within a platform that manages automotive radar product development—from initial architecture and modulation studies through the physical design of the antenna array and front-end electronics based on either III-V or silicon integrated circuit (IC) technologies.
Synthetic Aperture Radar (SAR)
SAMPL Lab students built an efficient, easy-to-use SAR simulator that connects to MATLAB for signal processing. SAR is a type of radar used to create 2D and 3D representations of an object and uses the motion of the radar antenna over a targeted region to provide finer spatial resolution than is possible with conventional beam-scanning radars. The SAMPL Lab design focuses on sub-Nyquist sampling of the received signal and full reconstruction of the image.
Smart (CW) Radar
Respiratory gating and tumor tracking are two promising motion-adaptive lung cancer treatments that minimize the incidence and severity of normal tissues and precisely deliver a radiation dose to the tumor. However, conventional gating techniques are either invasive to the body or bring insufficient accuracy and discomfort to the patients. Graduate students at Texas Tech University, under the direction of Dr. Changzhi Li and in partnership with the National Science Foundation (NSF) and Cancer prevention and Research Institute of Texas (CPRIT), used NI AWR design software to develop a smart DC-coupled radar sensor to track the tumor location and thus control the radiation beam.
Massive MIMO and beam-forming signal processing enabled by phased-array antenna systems are expected to play a critical role in 5G as both greatly enhance coverage and the user experience across the entire range of frequency bands, including the mmWave spectrum. New phased-array modeling capabilities in NI AWR Design Environment platform provide ease of configuration, reduced overhead, and shorter design and simulation times by enabling designers to configure the array’s geometry using either a standard or custom layout pattern.
AWR Design Environment
The AWR Design Environment platform provides a single, complete design environment that seamlessly integrates simulation and design technology and manages the circuit/system/EM components within a project, supporting schematic design entry and fully-synchronized physical design and layout.
Visual System Simulator
Visual System Simulator™ (VSS) system design software supports development of end-to-end radar system development VSS software supports with radar specific analyses and component modeling for RF, DSP, target and channel propagation.
Microwave Office circuit design software features APLAC multi-rate, transient, and transient-assisted harmonic balance (HB) and time variant (circuit envelope) analysis for linear and nonlinear circuit simulation of radar front-end components. Design aids include load-pull analysis, network synthesis (optional), design for manufacturing (optimization, yield and statistical analysis), device libraries, and process design kits (PDKs) to address MMIC, RFIC, PCB and multi-chip module designs.
The AXIEM proprietary full-wave planar EM simulator based on method-of-moments (MoM) fast-solver technology simulates planar antenna arrays used in MIMO and beam-steering antenna systems.
Analyst™ 3D finite-element method (FEM) EM analysis models 3D antennas and package and board interconnects, including wire bonds, air bridges and ball grids.
The RF Planner accelerates development of first-cut links for radio communications systems, cellular, or military radio, enabling designers to efficiently determine spurious-free dynamic range and bandwidths and providing spurious analysis from device nonlinearities, as well as cascaded measurements such as NF, P1dB, signal-to-noise ratio (SNR), and IM3.
The radar library within the phased-array generator wizard enables rapid configuration of phased-array antenna systems, supporting feed network development, gain tapering, and simulation of MIMO and beam-forming arrays.