AWR White Papers

Radar Systems

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Design Challenges of Next-Generation AESA Radar Phased-array antennas were first used in military radar systems to scan the radar beam quickly across the sky to detect planes and missiles. These systems are becoming popular for a variety of applications and new active electronically-scanned arrays (AESAs) are being used for radar systems in satellites and unmanned aerial vehicles. As these systems are deployed in new and novel ways, size and performance requirements are becoming critical and are being addressed through innovative architectures and system capabilities made possible through improvements in microwave and signal processing technologies such as GaN power amplifiers (PAs), new MMIC/Extreme MMIC devices, heterogeneous More-than-Moore integration, cost reductions for transmit/receive (T/R) modules, new mmWave silicon ICs, and electro-optic integration. 6 To support these development efforts, electronic design automation (EDA) technologies are evolving to provide designers with system architecture, component specifications, physical design of individual components, and verification prior to proto- typing. This white paper examines these technology trends and presents several examples where advances in AWR Design Environment software are supporting next-generation AESA and phased-array radar development. Phased-Array Technology An AESA-based radar, also known as active phased-array radar (APAR), consists of individual radiating elements (antennas), each with a T/R solid-state module containing a low-noise receiver, PA, and digitally-controlled phase/delay and gain elements. Phase and amplitude control of the input signal to the individual elements provides steerable directivity of the antenna beam over both azimuth and elevation, which allows the radar to aim the main lobe of the antenna in the desired direction. Unlike a mechanically steered radar, a phased array can rotate its pattern in space with practically no delay. Digital control of the module transmit/receive gain and timing permits the design of an antenna with not only beam steering agility and interleaving radar modes, but also extremely low sidelobes, which provides a significant reduction in antenna radar signature compared to passive ESA and mechanically steered antennas. 7 The width of the beam depends on the number of elements in the array. By increasing the number of elements (or sensors) in an array, the beam becomes sharper and thus more efficient in detecting smaller size targets. Today's AESA radars typically consist of thousands of individual elements electrically interconnected through increasingly complex structures designed for reduced size and weight, as well as increased performance (in other words, lower loss). At lower RF frequencies (< 10GHz), where a longer wavelength increases the antenna size and spacing, the RF, intermediate frequency (IF), and/or baseband signal routing can be addressed with discrete components and off-the-shelf MMICs on printed circuit boards (PCBs)/packaging. The impact of longer traces will be offset by the lower PCB losses at these frequencies and the interface to the antenna can be considered independent of the IC unit cell due to the relatively flexible packaging requirements. However, at mmWave frequencies (> 30GHz), physically short antenna spacings (~λ/2 < 5mm), packaging losses, and manufacturing challenges with impedance-controlled multi-layer packaging interconnects make high-functionality ICs and sophisticated integration schemes more attractive. Designing these types of complex packaging schemes for high-frequency signaling must be addressed with circuit simulation and EM analysis specialized for RF and microwave electronics. 8 6. 7. 8. Xiaoxiong Gu et al., "W-Band Scalable Phased Arrays for Imaging and Communications," IEEE Commun. Mag., April 2011, pp. 196-20. Radar Systems 12

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