Moving target indication with non-linear radar

Gallagher, Kyle A.; Narayanan, Ram M.; Mazzaro, Gregory J.; Ranney, Kenneth I.; Martone, Anthony F.; Sherbondy, Kelly D.

doi:10.1109/radar.2015.7131219

Cited by 21 publications

(17 citation statements)

References 8 publications

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“…Therefore, the loading conditions of the two measurements are slightly different. The spectrum analyzer is matched to 50 Ω throughout the bands of interest with an input reflection coefficient 11 S of less than 20 dB, which provides a 99% power transfer. The differences between the loading conditions for the fundamental and second harmonic measurements is therefore expected to be negligible compared to using a 50 Ω termination.…”

Section: System Test Resultsmentioning

confidence: 99%

Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement System

et al. 2018

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Radio frequency (RF) circuit elements that are traditionally considered to be linear frequently exhibit nonlinear properties that affect the intended operation of many other RF systems. Devices such as RF connectors, antennas, attenuators, resistors, and dissimilar metal junctions generate nonlinear distortion that degrades primary RF system performance. The communications industry is greatly affected by these unintended and unexpected nonlinear distortions. The high transmit power and tight channel spacing of the communication channel makes communications very susceptible to nonlinear distortion. To minimize nonlinear distortion in RF systems, specialized circuits are required to measure the low level nonlinear distortions created from traditionally linear devices, i.e., connectors, cables, antennas, etc. Measuring the low-level nonlinear distortion is a difficult problem. The measurement system requires the use of high power probe signals and the capability to measure very weak nonlinear distortions. Measuring the weak nonlinear distortion becomes increasingly difficult in the presence of higher power probe signals, as the high power probe signal generates distortion products in the measurement system. This paper describes a circuit design architecture that achieves 175 dB of dynamic range which can be used to measure low level harmonic distortion from various passive RF circuit elements.

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Section: System Test Resultsmentioning

confidence: 99%

Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement System

et al. 2018

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“…The PRI, τ b , is defined as the time it takes to collect data from all N frequency samples (N = 81) to create one range profile. The maximum Doppler frequency, f Dmax , is given by [61] …”

Section: Moving Target Imaging Approachmentioning

confidence: 99%

“…Dividing both sides by the number of complete data collections taken, M, yields the Doppler frequency step size, ∆ f D , given by [61] …”

Section: Moving Target Imaging Approachmentioning

confidence: 99%

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Static and Moving Target Imaging Using Harmonic Radar

et al. 2017

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Nonlinear radar exploits the difference in frequency between radar waves that illuminate and are reflected from electromagnetically nonlinear targets. Harmonic radar is a special type of nonlinear radar that transmits one or multiple frequencies and listens for frequencies at or near their harmonics. Nonlinear radar differs from traditional linear radar by offering high clutter rejection and is particularly suited to the detection of devices containing metals and semiconductors. Examples include tags for tracking insects, tags worn by humans for avoiding collisions with vehicles, or for monitoring vital signs. Such tags contain a radio-frequency (RF) nonlinearity, often a Schottky diode, connected to a suitable antenna. Targets with inherent nonlinearities, such as metal contacts, semiconductors, transmission lines, antennas, filters, and ferroelectrics, also respond to nonlinear radar. In this paper, the successful exploitation of harmonic radar for moving target imaging and synthetic aperture imaging of targets, while suppressing clutter signals from linear targets, are presented. Our results demonstrate some unique advantages of harmonic radar over its traditional linear counterpart.

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“…Finally, the bandwidth covered by the third-order intermod products (180MHz) fixed the HRR cell size at approximately 0.83m, much smaller than the target spacing. These initial experiments indicate that if certain requirements are satisfied, then a non-linear system should be able to exploit inter-modulation products to obtain additional information for coherent processing, including moving target indication (MTI) [7] and synthetic aperture radar (SAR) processing [5,8]. Signal degradation will likely occur, however, due to various noise sources; especially since the signals of interest are usually extremely weak.…”

Section: System Definition and Operation In A Perfect Worldmentioning

confidence: 99%

Instantaneous, stepped-frequency, nonlinear radar

et al. 2015

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Researchers have recently developed radar systems capable of exploiting non-linear target responses to precisely locate targets in range. These systems typically achieve the bandwidth necessary for range resolution through transmission of either a stepped-frequency or chirped waveform. The second harmonic of the reflected waveform is then analyzed to isolate the non-linear target response. In other experiments, researchers have identified certain targets through the inter-modulation products they produce in response to a multi-tone stimulus. These experiments, however, do not exploit the phase information available in the inter-modulation products.We present a method for exploiting both the magnitude and phase information available in the inter-modulation products to create an "instantaneous" stepped frequency, non-linear target response. The new approach enables us to both maintain the unambiguous range dictated by the fundamental, multi-tone separation and obtain the entire target signature from a single transmitted waveform. IntroductionSeveral organizations have considered the application of radar to the problem of detecting electronic devices in secured areas. One approach envisions the use of portals to detect the unwanted devices before individuals can carry them into the restricted area [1]. Other approaches consider the use of radar to detect the objects at greater distances, thereby eliminating the need for a portal [2,3]. In both cases, however, the detection systems exploit a target device's non-linear, harmonic responses to a specific transmitted waveform [4,5]. Since natural objects fail to produce this non-linear response, these new systems offer the opportunity to dramatically reduce the number of false alarms generated at a desired detection probability. They accomplish this through analysis of the complex magnitude of harmonics and inter-modulation (intermod) products produced by the target. In what follows we restrict our attention to only non-linear radar systems that are capable of detecting targets at a distance.While earlier magnitude-based non-linear target detectors leverage harmonic responses-including intermod products-to reduce the number of false alarms, they fail to leverage the phase information also available in those harmonics and intermod products. If this additional information could be captured, then it should be possible to measure the range to the target. In particular, if the phase information could be recorded for intermod products from many regularly spaced frequencies (i.e. a multi-tone system), then it would be possible to create an "instantaneous" stepped-frequency waveform in the receive band (i.e. the harmonic band) of the radar. That is, by considering all of the intermod products of order p, it would be possible to simultaneously measure all of the frequency samples required by a stepped frequency radar system (at the expense of introducing a larger system bandwidth). These intermod products would occur around integer multiples of the transmitted frequencies-integer...

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Moving target indication with non-linear radar

Cited by 21 publications

References 8 publications

Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement System

Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement System

Static and Moving Target Imaging Using Harmonic Radar

Instantaneous, stepped-frequency, nonlinear radar

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