Experiences are shared from a recent radar measurement and characterization effort. A regimented data collection procedure ensures repeatability and provides an expedited alternative to typical narrowband capabilities. Commercially-available instrumentation is repurposed to support wideband data collections spanning a contiguous range of frequencies from 700 MHz to 40 GHz. Utilizing a 4-port network analyzer, both monostatic and quasi-monostatic measurements are achievable. Polarization is varied by way of a custom-designed antenna mount that allows for the mechanical reorientation of the antennas. Computational electromagnetic modeling is briefly introduced and serves in validating the legitimacy of the collection capability. Data products presented will include high-range resolution profiles and inverse synthetic aperture radar (ISAR) imagery.
Today’s military radars are being challenged to satisfy multiple mission requirements and operate in complex, dynamic electromagnetic (EM) environments. They are simultaneously constrained by practical considerations like cost, size, weight and power (SWaP), and lifecycle requirements. Tomorrow’s radars need to be resilient to changing operating environments and capable of doing more with fewer resources. Radar research supports this shift toward more agile and efficient radar systems, and current trends include modular hardware and software development for multi-purpose, scalable radio frequency (RF) solutions. Software-defined radios (SDRs) and other commercial-off-the-shelf (COTS) technology are being used for flexible waveform generation, signal processing, and nontraditional radar applications. Adaptive RF technology, including apertures and other front-end components, are being developed for multi-purpose functionality and resiliency. Together, these research trends will result in a technology framework for more robust future systems that are capable of implementing cognitive processing techniques and adapting their behavior to meet the demands of a congested and contested EM environment.
We present an analysis of receiver performance when diverse waveforms such as the advanced pulse compression noise (APCN) are used. Two perspectives within the shared channel are considered: <i>(1) </i>a radar transceiving APCN in the presence of other radar interference sources, and <i>(2)</i> a communications system transceiving M-ary quadrature amplitude modulation (QAM) in the presence of a radar interference sources practicing waveform diversity. Through simulation, we show how waveform diversity and the ability to tune the APCN spectrum characteristics minimizes interference for co-channel users.
The conditions for orthogonality in Multiple Input Multiple Output (MIMO) radar enable a virtual array gain beneficial to beamforming on receive. However, this condition imposes a constraint on transmit beamforming for various reasons. As a result, a performance loss can be expected when compared to a traditional monostatic phased array. With this in mind, we analyze the complex scattering coefficients for a scenario in which MIMO radar beamforming is used to illuminate an arbitrary target obfuscated by different line-of-sight obstructions such as foliage and/or buildings. Using finite-difference time-domain (FDTD) modeling, our simulations will grow the understanding of how plausible MIMO radar is for detecting targets in challenging environments.
This work demonstrates the feasibility of using the advanced pulse compression noise (APCN) radar waveform for synthetic aperture radar (SAR). Using a simple image formation process (IFP), we not only show that we can successfully form images using the APCN waveform, but we grow our understanding of how different combinations of APCN waveforms and side lobe weighting functions impact SAR image quality. In this paper, an analysis is presented that compares the target range point spread function (PSF) for several simulated SAR images.
Experimental results from recent field testing with the noise correlation radar (NCR) are presented as a proof of concept. In order to understand the effectiveness of the NCR, a predetermined set of measures is established. We discuss the three experimental configurations used in evaluating the system’s range resolution/error, robustness to interference, and secure radio frequency (RF) emission. We show that the advanced pulse compression noise (APCN) radar waveform has low range measurement error, is robust to interference, and is spectrally nondeterministic. In addition, we determine that an improvement in range resolution due to phase modulation is achieved as a function of the random code length rather than the compressed pulse length.
Noise radar systems encounter target fluctuation behavior similar to that of conventional systems. For noise radar
systems, however, the fluctuations are not only dictated by target composition and geometry, but also by the non-uniform
power envelope of their random transmit signals. This third dependency is of interest and serves as the basis for
the preliminary analysis conducted in this manuscript. General conclusions are drawn on the implications of having a
random power envelope and the impacts it could have on both the transmit and receive processes. Using an advanced
pulse compression noise (APCN) radar waveform as the constituent signal, a computer simulation aids in quantifying
potential losses and the impacts they might have on the detection performance of a real radar system.
In an effort to enhance the security of radar, the plausibility of using a complex, aperiodic random signal to modulate
a pulse linear frequency modulation (LFM) or "chirp" radar waveform across both its fast-time and slow-time samples
is investigated. A non-conventional threat is considered when illustrating the effectiveness of the proposed waveform as
an electronic counter-countermeasure (ECCM). Results are derived using stretch processing and are assessed using the
receiver cross-correlation function with a consideration for the unmodulated case as a basis for comparison. A tailored radar
ambiguity function is also included in the analysis, and is used to demonstrate how the proposed waveform possesses an
ideal characteristic suitable for combating today's electronic warfare (EW) threats while preserving its inherent functionality
to detect targets.
This work investigates the plausibility of target detection using a pulsed linear frequency modulated (LFM) noise
waveform conglomerate. The results were generated from simulation and demonstrated that the proposed transmit waveform
structure possesses the ability to successfully mask any "chirp-like" characteristic making recognition and/or corruption
by unintended 2nd-party passive receivers virtually impossible. Due to the fact that the pulsed LFM noise transmit signal
was digitally stored as a reference, we were able to employ classical correlation mixing techniques that enabled the target
detection approach to successfully resolve targets at range in the presence of interference.
In addition, the process of using various binary random signal modulation schemes for the purpose of masking
conventional pulsed radar waveform is also investigated. This work describes research involving target detection using a
pulsed linear frequency modulated (LFM) waveform modulated by various discrete random signals. The results include
a measure of correlation assessing the effectiveness of the various random signal modulators, Monte Carlo simulations
identifying the loss introduced by the random signal modulators during the transmit process, matched filter receiver analysis
analytically comparing the probability of detection performance when the random signal modulators are considered, and
ambiguity functions to assess the uncertainty of the transmit waveform as a function of Doppler and time.