Active Electronically Scanned Array Research Articles

A Near‐Zero Index Metamaterial Lens for Reduced Complexity and High‐Performance Active Electronically Scanned Arrays

AbstractA lens consisting of an anisotropic near‐zero index metamaterial (NZIM) is introduced for improving the far‐field performance of active electronically scanned arrays (AESA). Several simulation studies demonstrate how the NZIM lens (metalens) can be functionalized to transform the embedded element pattern of an array from a typical cosinusoidal shape to a flat‐topped pattern, dramatically reducing the gain at wider angles. This corresponds to reductions in scan loss and suppression of grating lobes in the desired field of view (FOV), especially for arrays with large element spacing (i.e., sparse or thinned arrays). The metalens concept is demonstrated through several simulation studies illustrating the beam shaping capability of NZIM materials. A fabricated metalens demonstrates full suppression of grating lobes and minimal scan loss with a ±10° FOV, which is ideally suited for limited FOV applications such as geosynchronous satellite communications.

Progressive Test and Evaluation Strategy for Verification of KF-X AESA Radar Development

This paper describes a progressive test and evaluation strategy for verification of Korean Fighter eXperimental (KF-X) AESA(Active Electronically Scanned Array) radar development. Three progressive stages of development test and evaluation were officially performed from simulated test conditions to actual operating conditions according to standards: radar function/performance and avionics integration. KF-X AESA radar development is repeatedly verified by progressive stages consisting of five tests: Roof-lab ground test, System Integration Laboratory(SIL) ground test, Flying Test Bed(FTB) test, KF-X ground test, and KF-X flight test. As a result, the risk factor decreases as stages and tests progress. Therefore, development test and evaluation of KF-X AESA radar are successfully performed at low development risk.

A C-band folded planar low-pass filter utilizing U-shaped probe for high power TR module

In this paper, a C-band folded low-pass filter is realized in the planar circuit by utilizing a U-shaped probe. The proposed filter consists of four microstrip patches and a U-shaped probe. The configuration, equivalent circuit and design method of the proposed filter are demonstrated. A prototype of the low-pass filter operating in C-band has been designed, fabricated and measured. The maximum insertion loss of the fabricated filter is about 0.8 dB from 5 GHz to 6 GHz, while the maximum return loss is -11 dB. The out of band rejection is over 30 dB at 12 GHz. The measured results show reasonable correlation with the ideal circuit and the simulated results. The proposed low-pass filter can be used for the high power transmit/receive (TR) module in active electronically scanned array (AESA).

X-band MMICs for a Low-Cost Radar Transmit/Receive Module in 250 nm GaN HEMT Technology

This paper describes Monolithic Microwave Integrated Circuits (MMICs) for an X-band radar transceiver front-end implemented in 0.25 μm GaN High Electron Mobility Transistor (HEMT) technology. Two versions of single pole double throw (SPDT) T/R switches are introduced to realize a fully GaN-based transmit/receive module (TRM), each of which achieves an insertion loss of 1.21 dB and 0.66 dB at 9 GHz, IP1dB higher than 46.3 dBm and 44.7 dBm, respectively. Therefore, it can substitute a lossy circulator and limiter used for a conventional GaAs receiver. A driving amplifier (DA), a high-power amplifier (HPA), and a robust low-noise amplifier (LNA) are also designed and verified for a low-cost X-band transmit-receive module (TRM). For the transmitting path, the implemented DA achieves a saturated output power (Psat) of 38.0 dBm and output 1-dB compression (OP1dB) of 25.84 dBm. The HPA reaches a Psat of 43.0 dBm and power-added efficiency (PAE) of 35.6%. For the receiving path, the fabricated LNA measures a small-signal gain of 34.9 dB and a noise figure of 2.56 dB, and it can endure higher than 38 dBm input power in the measurement. The presented GaN MMICs can be useful in implementing a cost-effective TRM for Active Electronically Scanned Array (AESA) radar systems at X-band.

항공기 AESA 레이다에서 TWS를 이용한 지상 이동 표적 추적

A target-tracking method using the ground moving target indicator (GMTI) mode on active electronically scanned array (AESA) radar is proposed. The GMTI mode can operate in wide ground areas. However, the 3-dB beamwidth of the X-band radar is narrow, and a target is detected on multiple adjacent beams. To delete overlapping target plots, beam-to-beam processing considering a real-time system is proposed. In addition, a track while scan (TWS) multiple-target-tracking algorithm was constructed for the system. Through a flight test with true car mounted GPS, it was confirmed that the real-time processing ability and target-tracking performance of the GMTI algorithm were satisfactory.

From the Editors of the Special Issue on Multiplatform and Multifunctional RF Systems

The idea for this Special Issue on Multiplatform and Multifunctional RF Systems [(MPRFS) and (MFRFS)] was conceived in 2020 on the strength of a very successful workshop on Multiplatform RF Systems organized by the European Defence Agency (EDA). The editors were further motivated by the realization that modern platforms such as fighter jets, drones, reconnaissance aircraft, frigates, destroyers, and submarines have limited real estate for the inclusion of even more sensors—giving rise to the field of MFRFS. MFRFS represents a research and technology endeavor to realize multiple RF functions such as radar, electronic attack (EA), electronic support (ES), and communications (Comms) in a platform– sensor suite through the sharing of hardware architectures. There is no standard definition for MFRFS, but one interpretation is the use of active electronically scanned array (AESA) antennas for radar, EA, ES, and Comms so that the overall number of antennas distributed over a given platform may be reduced. There are, of course, other valid interpretations not predicated on the use of ASEAs, but rather aim to consolidate multiple functions into one suite of common hardware. The concept of MPRFS is based on the controlled utilization of RF systems that are available within an interconnected and spatially dislocated multiplatform constellation. Individual platforms may be strategically positioned and managed to improve constellation performance in complex operational environments. MPRFS and MFRFS are areas of active research and this is set to intensify in the coming years. We, as guest editors, are pleased to publish this first special issue dedicated to the field of MPRFS and MFRFS and, as the field matures, we are confident that future special issues will follow. This special issue comprises four interesting contributions. Each is briefly summarized.

Real-Time Multiple Input Multiple Output (MIMO) Radar Using Software Defined Radio

In this paper, commercially-available software-defined radios (SDRs) are used to build a 64-channel, reconfigurable Active Electronically Scanned Arrays (AESA) radar operating in C-band (NATO G-band). The SDRs are used to design and implement a 3-dimensional multi-input and multi-output (MIMO) radar. The flexibility of the SDRs has been harnessed to evaluate the performance of a linear frequency modulated continuous wave (LFMCW) MIMO radar using three different methods of achieving the orthogonality, namely Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), and Code Division Multiplexing (CDM). In addition, the radar’s parameters are user-selectable and can be rapidly changed such that the radar can be used in different environments without requiring changes to the hardware. Measurements indicate that the radar is capable of detecting and localizing multiple targets in all 3-dimensions, including bearing, range, and Doppler. The MIMO radar operates in real-time, with a refresh rate of only 3 seconds. Experimental results are generated for the TDM mode of operation with further research reporting on the CDM and FDM modes of operation.

Moving target detection and tracking with multiplatform radar network (MRN)

A multiplatform radar network (MRN) composed of multiple transmitting and receiving facilities is advantageous over monostatic radar in moving target detection (MTD) and tracking due to the diversity gain. Within the framework of the Internet of Battlefield Things (IoBT), the authors propose that the airborne platforms equipped with the cognitive multimodal radar (CMR), the subarray-based MIMO radar (SMR), the active electronically scanned array (AESA) radar, and the adaptive radar countermeasures (ARC) should team up in target detection and tracking. To obtain better target detection and tracking performance, the probing signals from the CMR, the SMR, and the AESA radar are adaptively optimised based on the scenario under consideration. The ARC consists of two parts: 1) RF signal sensing and recognition with deep neural network (DNN), that is, to detect, identify, and localise multiple radio frequency emitters; 2) intelligent fake return creation and jamming to confuse the enemy radars in real time in the field. This work aims to serve as a good reference for future researchers interested in developing MRN with diverse nodes and the general teaming of radars on the battlefield.

Evaluate the Cooling Performance of Transmit/Receive Module Cooling System in Active Electronically Scanned Array Radar

The active electronically scanned array (AESA) radar consists of many transmit/receive (T/R) modules and is used to track missiles approaching destroyers and fighters. The performance of the AESA radar depends on the T/R module temperature. The T/R module temperature should be maintained under 80 °C to guarantee the performance of the AESA radar. In order to match the design requirements of the cooling system of the AESA radar, it is necessary to evaluate the cooling performance according to various operation/installation environments. In this study, computational fluid analysis was performed by changing the number of T/R modules and the coolant mass flow rate to evaluate the cooling performance of the AESA radar coolant channel. The number of T/R modules was changed from 2 to 16, and the number of coolant inlet Re was changed from 277 to 11,116. As a result, it was confirmed that the temperature increased as the number of T/R modules increased. In addition, when the coolant status was laminar flow, it was confirmed that the cooling performance was significantly lowered. Therefore, the coolant status should be transient or turbulence to decrease the temperature of the T/R module. Additionally, the correlation between the arrangement of the T/R module and the cooling flow must be considered to cool the AESA radar.

AESA 레이다의 동시운용모드를 위한 빔 스케줄링 기법

The modern active electronically scanned array (AESA) airborne radar features an interleaved mode, whereby situational awareness can be maximized via incorporation of the radar’s electronic beam pointing capability. This interleaved mode can enable simultaneous operation of two or more modes, such as the air-to-air and sea surface-search modes, via the technique of time-sharing. One of the key requirements for successful realization of the interleaved mode is a beam scheduler design that facilitates effective control of the allocated resources for each mode. Thus, in this paper, we propose an effective beam scheduler that can control the allocated resources for each mode through the mode-switching option based on the radar’s frames, bars, and beams. Furthermore, the proposed beam scheduler involves the mode-switching decision logic and calculates the processing ratio for each mode.

항공기탑재 레이다용 X-대역 Low-Profile 능동위상배열 안테나 설계 및 제작

The results of the fabrication of active electronically scanned array (AESA) antennas with low-profile, low-weight, wide-scan, and thermal stability characteristics for aircraft-mounted radar are described. To reduce the size and weight of the antenna, a transmit–receive block is constructed in a quasi-tile structure in which the radio-frequency circuit-related transmit–receive module is a brick type, which is a flat structure, and the control board is a tile type, which is a stacked structure, to reduce the depth of the front of the antenna. In addition, the depth of the rear part of the antenna was reduced by manufacturing power and plate-shaped control-related modules at the rear of the antenna. The reduced antenna depth maximizes the effective isotropic radiated power (EIRP) and gain to noise temperature (G/T) by enlarging the antenna aperture. The manufactured antenna can scan a wide angle of ±70°. The cooling efficiency is improved by using a dual cooling structure that allows the cooling water to pass through the front cooling plate and then through the rear cooling plate. The EIRP of the manufactured AESA antenna is 104.04 dBmi, and G/T is 7.46 dB/K in Taylor weighting.

Impact of bandwidth on antenna‐array noise matching

This letter expands the treatments of wideband noise analysis of antenna arrays by including bandwidth effects on beam-equivalent receiver noise temperature, , and the active reflection coefficient, . The particular focus of the letter is on receiver noise decorrelation in wideband systems having noise bandwidth 1 Hz. The new analysis and simulations show increase in and the departure of from that obtained using contemporary analyses for 1 Hz. Although the paper also shows that for many applications over moderate bandwidths and close connection between the receiver and array the influence of on is not significant, the simulations of a 71-element array demonstrate that the noise decorrelation due to wide can result in tens of percent (as much as 45.5% in simulations described in this letter) increase in above the low-noise amplifier minimum noise temperature, which should be taken into account at the design stage of ultra-wide band systems, such as those under investigation by, for example, the Defense Advanced Research Project Agency (DARPA) in its wideband adaptive RF protection (WARP) program and ultra-sensitive active electronically scanned array (AESA) radars for tracking stealth objects.

Characterization of Self-Heating Process in GaN-Based HEMTs

Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This is especially true for systems operating with variable-envelope signals where accurate determination of self-heating effects resulting from strong- and fast-changing power dissipated inside transistor is crucial. In this work, we have developed an advanced measurement system based on DeltaVGS method with implemented software enabling accurate determination of device channel temperature and thermal resistance. The methodology accounts for MIL-STD-750-3 standard but takes into account appropriate specific bias and timing conditions. Three types of GaN-based HEMTs were taken into consideration, namely commercially available GaN-on-SiC (CGH27015F and TGF2023-2-01) and GaN-on-Si (NPT2022) devices, as well as model GaN-on-GaN HEMT (T8). Their characteristics of thermal impedance, thermal time constants and thermal equivalent circuits were presented. Knowledge of thermal equivalent circuits and electro–thermal models can lead to improved design of GaN HEMT high-power amplifiers with account of instantaneous temperature variations for systems using variable-envelope signals. It can also expand their range of application.

Scalable AESA 안테나를 위한 고효율 X대역 송수신블록 설계 및 제작

This paper presents the fabrication results of a scalable X-band transmit/receive block used in an active electronically scanned array (AESA) antenna. Due to the disadvantages of the miniaturization of the existing brick-type planar structure and the complexity of the tile-type stacked structure, a quasi-tile structure-based transmit/receive block was developed. The developed antenna had a radio-frequency circuit that was easy to implement in a flat type, and the control part had the advantage of miniaturization in a stacked type. It is easy to develop an AESA antenna of a desirable size by connecting the transmit/receive blocks. An ethylene glycol water-cooling structure was not added inside the transmit/receive block, as it was designed to cool one side of the block. The temperature difference between the high power amplifier(HPA) and the contact surface of the cooling plate improved by approximately 15 %. Gallium nitride devices were used in the transmit/receive module and had a higher breakdown field than conventional gallium arsenide devices. Hence, the module exhibited high efficiency when used in power-switching circuits and showed good heat dissipation efficiency and thermal conductivity. The transmit power of each transmit/receive block channel was 10 W, the receive gain was 28.4 dB, and the noise figure value was 3.4 dB.

A GaN HEMT Amplifier Design for Phased Array Radars and 5G New Radios.

Power amplifiers applied in modern active electronically scanned array (AESA) radars and 5G radios should have similar features, especially in terms of phase distortion, which dramatically affects the spectral regrowth and, moreover, they are difficult to be compensated by predistortion algorithms. This paper presents a GaN-based power amplifier design with a reduced level of transmittance distortions, varying in time, without significantly worsening other key features such as output power, efficiency and gain. The test amplifier with GaN-on-Si high electron mobility transistors (HEMT) NPT2018 from MACOM provides more than 17 W of output power at the 62% PAE over a 1.0 GHz to 1.1 GHz frequency range. By applying a proposed design approach, it was possible to decrease phase changes on test pulses from 0.5° to 0.2° and amplitude variation from 0.8 dB to 0.2 dB during the pulse width of 40 µs and 40% duty cycle.

AESA radar and IRST against low observable threats

PurposeModern fighter aircraft using active electronically scanned array (AESA) fire control radars are able to detect and track targets at long ranges, in the order of 50 nautical miles or more. Low observable or stealth technology has contested the radar capabilities, reducing detection/tracking ranges roughly to one-third (or even less, for fighter aircraft radar). Hence, infrared search and track (IRST) systems have been reconsidered as an alternative to the radar. This study aims to explore and compare the capabilities and limitations of these two technologies, AESA radars and IRST systems, as well as their synergy through sensor fusion.Design/methodology/approachThe AESA radar range is calculated with the help of the radar equation under certain assumptions, taking into account heat dissipation requirements, using the F-16 fighter as a case study. Concerning the IRST sensor, a new model is proposed for the estimation of the detection range, based on the emitted infrared radiation caused by aerodynamic heating.FindingsThe maximum detection range provided by an AESA radar could be restricted because of the increased waste heat which is produced and the relevant constraints concerning the cooling capacity of the carrying aircraft. On the other hand, IRST systems exhibit certain advantages over radars against low observable threats. IRST could be combined with a datalink with the help of data fusion, offering weapons-quality track.Originality/valueAn original approach is provided for the IRST detection range estimation. The AESA/IRST comparison offers valuable insight, while it allows for more efficient planning, at the military acquisition phase, as well as at the tactical level.

On the use of AESA (Active Electronically Scanned Array) Radar and IRST (InfraRed Search&Track) System to Detect and Track Low Observable Threats

The radar has been indisputably the most important sensor in the battlefield, allowing early warning and tracking of air vehicles. Modern fighter ircraft employing AESA fire control radars are able to acquire and track targets at long ranges, in the order of 50 nautical miles or more. However, the proliferation of low observable or stealth technology has contested radar capabilities, reducing their detection / tracking ranges roughly to one third. This degradation is more severe concerning fighter aircraft radars, since most stealth threats are optimised for higher frequency bands, as in the case of fire control radars. Hence, other parts of the electromagnetic spectrum have been reconsidered, such as infrared radiation (IR). Every aircraft is a source of IR, due to fuel combustion, aerodynamic friction and IR reflection. In this way, a jet fighter can be detected by an IR sensor against the cold background of the sky. Therefore, IRST systems have re-emerged, offering an alternative to the radar. Apart from their capabilities concerning target detection (whether stealth or not), IRST systems also exhibit passive operation, resilience to jamming and better angular accuracy. On the other hand, they are prone to weather conditions, especially moisture, while they cannot measure distance directly, as in the case of the radar. This work explores and compares the capabilities and limitations of the two approaches, AESA radars and IRST systems, offering also some insight to the benefits of sensor fusion.

Multifunction RF Systems for Naval Platforms.

The evolving role of modern navies has required increasingly higher levels of capability in the Radio Frequency (RF) shipboard systems that provide radar, communications, Electronic Attack (EA) and Electronic Support (ES) functions. The result has been a proliferation of topside antennas and associated hardware on naval vessels. The notion of MultiFunction RF (MFRF) systems has drawn considerable interest as an approach to reversing this trend. In a MFRF system, RF functions are consolidated within a shared set of electronics and antenna apertures that utilize Active Electronically Scanned Array (AESA) technology. This paper highlights a number of issues to be considered in the design and implementation of a naval MFRF system. Specifically, the key requirements of the RF functions of interest are first reviewed, and MFRF system design trade-offs resulting from costs and/or performance limitations in existing hardware technology are then discussed. It is found that limitations in hardware technology constrain the implementation of practical MFRF systems. MFRF system prototype development programs that have been conducted in other countries are described. MFRF resource allocation management is identified as an important future research topic.

GaN-based single-chip frontend for next-generation X-band AESA systems

AbstractA next generation of active electronically scanned array (AESA) antennas will be challenged with the need for lower size, weight, power, and cost. This leads to enhanced demands especially with regard to the integration density of the radio frequency-part inside aT/Rmodule. The semiconductor material GaN has proven its capacity for high-power amplifiers (HPA), robust receive components as well as switch components for separation of transmit and receive mode. This paper will describe the design and measurement results of a GaN-based single-chipT/Rmodule frontend (HPA, low noise anplifier, and single-pole double-throw (SPDT)) using UMS GH25 technology and covering the frequency range from 8 GHz to 12 GHz. The key performance parameters of the frontend are 13 W minimum transmit (TX) output power over the whole frequency range with peak power up to 17 W. The frontend in receive (RX) mode has a noise figure below 3.2 dB over the whole frequency range, and can survive more than 5 W input power. The large signal insertion loss of the used SPDT is below 0.9 dB at 43 dBm input power level.

Thermal-Aware Synthesis of 5G Base Station Antenna Arrays: An Overview and a Sparsity-Based Approach

Heat removal capabilities and radiation performances of several sparse antenna array topologies are studied for cooling enhancement in 5G millimeter-wave base station antennas. Both electromagnetic (EM) and thermal aspects are jointly considered for the first time in array layout optimization, and a novel connection between layout sparsity and thermal management is presented. Two types of active electronically scanned arrays (AESAs), based on the traditional and planar approaches, are examined. Thermal management in AESAs is discussed, with a focus on cooling challenges at millimeter waves. Being relatively low cost and low profile while supporting flexible beamforming, passively cooled planar AESAs with fanless CPU coolers are proposed, for the first time, to be used in 5G base stations. Additional cooling for such arrays is achieved by increasing the inter-element distances in the layout. Linear irregular arrays, spiral arrays, thinned arrays, circular ring arrays, and heat sink antenna arrays are revisited with a critical discussion on their EM and thermal performance. The results are compared with regular and square layouts that are used as benchmarks throughout this paper.