Direction-finding performance of a Ka-band ESM receiver

This paper covers development trends in communication and radar electronic warfare (EW). Threat scenario and role of EW sensors in developing Electronic Order of Battle (EOB) are described. EW is subdivided into Electronic Support Measure (ESM), Electronic Counter Measure (ECM) and Electronic Counter-counter Measure (ECCM) systems. Developments in communication ESM and ECM systems and their constituents are described. Under COM ECM, jammer system configuration and realisation of the constituent subsystems, jamming strategies used for effectively countering various types of communications are described. Developments in critical subsystems and configurations of typical radar EW systems are discussed. Finally the status of the indigenous developments in ESM, ECM and integrated systems are described.

Since cognition has become an important topic in Electronic Warfare (EW) systems, Electronic Support Measures (ESM) are used to monitor, intercept and analyse radar signals. Low Probability of Intercept (LPI) radars is preferred to be able to detect targets without being detected by ES systems. Because of their properties as low power, variable frequency, wide bandwidth, LPI Radar waveforms are difficult to intercept with ESM systems. In addition to intercepting, the determination of the waveform types used by the LPI Radars is also very important for applying counter-measures against these radars. In this study, a solution for the LPI Radar waveform recognition is proposed. The solution is based on the training of Support Vector Machine (SVM) after applying Principal Component Analysis (PCA) to the data obtained by Time-Frequency Images (TFI). TFIs are generated using Choi-Williams Distribution. High energy regions on these images are cropped automatically and then resized to obtain uniform data set. To obtain the best result in SVM, the SVM Hyper-Parameters are also optimized. Results are obtained by using one-against-all and one-against-one methods. Better classification performance than those given in the literature have been obtained especially for lower Signal to Noise Ratio (SNR) values. The cross-validated results obtained are compared with the best results in the literature.

Electronic support measures (ESM) systems use different methods for direction finding (DF). Performance of a DF antenna array is an essential measure of the overall ESM system. A common DF method of phase interferometry using a circular interferometer is discussed. Typically a circular interferometer employs a polarizer to match the desired incident polarizations to the polarization of the antenna array. This paper describes a simulation method for evaluation of polarizer impact on direction finding performance of a circular interferometer. Simulation of DF antenna performance of a circular interferometer with and without a polarizer, using method-of-moments antenna simulation and spreadsheet based post-processing. The benefits of simulation include being a cost effective way of performance prediction for a new design or for the influence of installation structures on an existing system. Sample DF accuracy results are discussed and compared to previously published specifications. This work is based on analysis conducted on the ESM system for the surface combatant force guided missile frigates (FFG ) upgrade project.

This paper provides an update on research and development within the Australian defence industry of microwave photonics systems and their application to electronic warfare (EW) receivers. The major developments have diverged into two primary streams: the development of EW receivers to accommodate the signal transmission characteristics of microwave photonic links and development of broadband optical signal processing components.

The field of circular (or cylindrical) arrays has received far less attention than that devoted to linear and planar arrays. At first sight this seems surprising since one of their principal advantages is the ability to deflect beams electronically through 360° with little change of either beamwidth or sidelobe level. Circular arrays have been applied, to a limited extent, in both communication systems and navigational aids since the late 1930s. There has, however, been surprisingly little change in their scale of application since that date, though there are now signs of a significant increase of interest in such arrays for applications to DF (Direction Finding) and ESM (Electronic Support Measures) systems. The analysis and general understanding of the properties of circular arrays has progressed steadily for many years and the most significant developments were probably made by several groups of workers in the 1960s when the concept of phase mode excitation was developed. The lack of applications in the past is prob ably due to the fact that the basic problems of exciting circular arrays with the correct values of amplitude and phase are, in general, more complex than for linear arrays. Furthermore, electronic scanning of directional patterns for circular arrays may be difficult to implement and can require both the amplitude and phase of each element of the array to be changed.

Five basic actions are involved in the sequence of events taken to protect a `platform' (airplane, ship, or tank): pre-engagement collection of intelligence, also known as electronic warfare support measures; self-concealment; threat detection; processing of threat information; and response. The area of electrooptic warfare is used to illustrate these actions.

Accurate classification or recognition of phase modulated radar waveforms, typically accomplished via the combination of pulse parameter estimates and matched filtering, poses a simple problem in ideal conditions. In less than ideal conditions, carrier frequency, time offset, pulse amplitude, initial phase, and bandwidth are unknown to the electronic warfare (EW) receiver rendering the application of a matched filter futile. Recognition of these waveforms is critical in various spectrum management, surveillance, and EW applications. This effort investigates the use of features extracted from the ambiguity function (AF) of an intercepted pulse. Specifically, this effort will expand upon the methodology of previous work done which uses the autocorrelation as a basis for extracting features. To test the efficacy of this work, extensive Monte Carlo testing employed. Simulation results prove that the methodology implemented herein achieves an overall correct classification rate of about 90% at a signal-to-noise ratio (SNR) of −2 dB on data similar to the training data.

Most methods of radio emission source localization are based on an estimation of received signal parameters. Evaluation of signal reception direction is used in a method called a direction of arrival (DOA). The DOA is one of the most commonly used location methods in wireless systems. Its important advantage is independence from knowledge of a time-frequency structure of the received signal. Therefore, this method is used primarily in military radio reconnaissance systems and electronic warfare. In this paper, we evaluate errors in determining the DOA resulting from propagation phenomena occurring in an urbanized environment. A maximum power received from a given direction is the basis for the estimation of the DOA in most radio direction-finders. Thus, the direction of maximum radiation of the localized object is important because it causes a change of the extremum in a power azimuth spectrum (PAS). Simulation studies are the basis for assessing the DOA error for the transmitters with the directional antennas. To model the impact of propagation phenomena, a multi-elliptical model is used. This model considers the majority of propagation phenomena occurring in the urbanized environment. The possibility of considering patterns of the transmitting and receiving antenna is its important advantage. In this case, the Gaussian is used to model the pattern of the directional antennas. The assessment of the DOA error is carried out for non-line-of-sight conditions between the receiver and transmitter, i.e., the radio direction-finder and localized object, respectively. In simulation studies, the influence of the transmitting antenna parameters, i.e., its beamwidth and direction of maximum radiation, on a shape of the received PASs and their extremums is considered.

TSV technology enables small size, high density, high integration, and high performance 3D integration. Currently, its application or even commercialization is occurring in Memory IC, high performance logic IC, and MEMS, microwave and millimeter wafer application will become an emerging field in coming years with booming of the 5G, millimeter wave radar. For high frequency application, TSV interposer based 2.5D/3D integration is a competitive choice. This paper proposes a dual redundant TSV interconnection design in High resistivity Si interposer for Millimeter Wave Applications. To verify the feasibility of this design, a set of test structures that can work at millimeter wave is designed, which is made of dual redundant TSV interconnection linked CPW lines. Process is developed for High resistivity Si TSV interposer and Test structures are fabricated and tested, the results show that the insertion loss of the test structure with dual redundant TSV interconnect is <1.57 dB@40GHz.

In order to increase the coherent accumulation time to improve signal-to-noise ratio (SNR), a novel four-element antenna system of direction finding is presented to solve the problem of low direction finding (DF) accuracy in miniature meter wave radar. This method adopts virtual polarization technique to obtain virtual polarization receiving of right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) signals. It can realize omnibearing angle measurement. Mathematical models of signal are established by means of quantitative analysis of five major factors, which can affect DF accuracy. Formulas of error are derived for angle measurement. Experimental data results indicate that it can achieve good performance for angle measurement, if five influencing factors are quantified and controlled in limited range.

A theoretical result for processing signals that have unknown distributions and priors in white Gaussian noise

The scheme of mono-pulse direction finding is well established. This paper uses a method of electromagnetic simulation to evaluate the direction finding performance of a number of common mono-pulse schemes. The mono-pulse variants include amplitude comparison of mechanically squinted beams, electronic squint and a linear interferometer. The advantage of simulation is that performance and other features of each scheme can be evaluated prior to implementation. The electromagnetic simulation is based on readily available Method of Moment (MOM) code with additional post processing. This work is applicable to situations that require emitter direction information such as cognitive radio systems, smart communication networks and electronic warfare.

This paper describes a design of novel wideband co-aperture cavity-backed spiral antenna for airborne passive direction finding (DF) applications. Due to the restricted installation locations and rigorous environmental conditions, the design integrates two separate bands of cavity-backed spiral antennas into a common radome which can effectively reduce radar cross section (RCS) and the difficulty of mounting on airframe. The antenna design is modeled and optimized by using commercial electromagnetic software. Simulation results reveal good performance from 2 to 40GHz which can be considered as an excellent candidate to replace the original discrete aperture design. The proposed antenna will be supplied in amplitude and/or phase-tracking sets of typical airborne electronic warfare (EW) systems

Electronic Warfare (EW) and Radio Detection and Ranging (Radar) are two of the many applications that rely on multi-channel and phase-coherent configurations for signal processing. We provide herein an overview of the complexities and requirements of a multi-channel phase-coherent measurement system. Multiple Input Multiple Output [MIMO] systems have to overcome key technical challenges related to phase, time and frequency synchronization in order to coherently receive and process the data acquired/generated from each input/output. In practical MIMO systems, the radio hardware should be capable of acquiring and/or generating such phase coherent signals across the multiple channels. Further, the systems need to be able to sustain the phase coherence over considerable duration of time, depending on the sensitivity of the system. However, drifts will occur owing to the effects like temperature, thermal expansion, mismatched cable lengths, uncorrelated phase noise, ADC sample clock phase noise and quantization noise. Thus, a calibration process is required to compensate for the drift, whenever it crosses a particular threshold value that defines the accuracy of the phase-coherent system. In this paper, an FPGA based software-defined calibration method is presented for synchronizing the phase and magnitude across multiple channels of a system. This method allows the phase/magnitude drift over time to be periodically monitored and calibrated, when there is a need. With the FPGA built into the system, the calibration can take place remotely without the need of connecting the system to an external calibration kit. Also, measurement results are provided for a state of the art super heterodyne receiver system to show that the phase drift is lesser than ±1 degree across a 500MHz – 26.5GHz frequency range at 23°C ± 5°C for 2 and 4 channels configurations. Such systems can find use in a variety of real-world MIMO implementations such as Direction Finding, Beam Steering, Passive Radars, MIMO and Phased-Array Radar Systems, where phase coherence, alignment and /or synchronization has added advantages to multi-channel systems.

Electronic Warfare (EW) and Radio Detection and Ranging (RADAR) are two of the many applications that rely on multi-channel and phase-coherent configurations for signal processing. We provide an overview of the complexities and requirements of a multi-channel phase-coherent measurement system. Multiple Input Multiple Output [MIMO] systems have to overcome key technical challenges related to phase, time, and frequency synchronization to coherently receive and process the data acquired/ generated from each input/output. In practical MIMO systems, the radio hardware should be capable of acquiring and/or generating such phase coherent signals across the multiple channels. Further, the systems need to be able to sustain the phase coherence over considerable duration of time, depending on the sensitivity of the system. However, drifts will occur, owing to the effects of, e.g., temperature, thermal expansion, mismatched cable lengths, uncorrelated phase noise, ADC sample, clock phase noise, and quantization noise. Thus, a calibration process is required to compensate for the drift, whenever it crosses a particular threshold value that defines the accuracy of the phase-coherent system. In this paper, an FPGA based software-defined calibration method is presented for synchronizing the phase and magnitude across multiple channels of a system. This method allows the phase/magnitude drift over time to be periodically monitored and calibrated when there is a need. With the FPGA built into the system, the calibration can take place remotely without the need of connecting the system to an external calibration kit. Also, measurement results are provided for a state of the art super heterodyne receiver system to show that the phase drift is lesser than ± 1 degree across a 500 MHz to 26.5 GHz frequency range at 23 °C ± 5 °C for two and four channel configurations. Such systems can be useful in a variety of real-world MIMO implementations such as Direction Finding, Beam Steering, Passive Radars, MIMO and Phased-Array Radar Systems, where phase coherence, alignment, and/or synchronization has added advantages to multi-channel systems.