Nonlinear synthetic aperture radar imaging using a harmonic radar

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

doi:10.1117/12.2177219

Cited by 14 publications

(13 citation statements)

References 22 publications

(19 reference statements)

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“…This distance offset d 0 is a correction that accounts for the non-negligible delay of signals propagating within the radar, which every signal will experience just before transmission from the antenna and just after capture by the antenna. If d 0 is ignored, the calculation given by (8) will result in a consistent over-estimate of the true value of d because the phase of V rec relative to V trans will always contain such a delay. For short standoff distances ( For a particular nonlinear radar, the distance d 0 may be extracted by (a) measuring delay through each of the cables, connectors, and components in the transmit and receive paths, adding them up, and dividing by 2, or (b) placing a nonlinear target directly in front of the antenna (d = 0) and calculating range-to-target using (9).…”

Section: Wireless Experimentsmentioning

confidence: 96%

“…Recently, the authors demonstrated over-the-air detection and ranging of nonlinear targets using transmit waveforms that were chirped [6] or stepped [7] across an ultra-wide bandwidth. Selecting the stepped-frequency transmit waveform, the authors generated images of nonlinear targets using a synthetic aperture [8] and demonstrated moving target indication of nonlinear targets [9]. Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Throughout the authors' stepped-frequency work [7][8][9], reflected harmonics have been assumed to be constant in both magnitude and phase across the relevant band of received frequencies at the target (or constant in magnitude and linear in phase when the target is placed at a standoff distance). This condition is necessary to range the target using an inverse Fourier Transform [10,11].…”

Section: Introductionmentioning

confidence: 99%

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Phase responses of harmonics reflected from radio-frequency electronics

et al. 2016

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The phase responses of nonlinear-radar targets illuminated by stepped frequencies are studied. Data is presented for an experimental radar and two commercial electronic targets at short standoff ranges. The amplitudes and phases of harmonics generated by each target at each frequency are captured over a 100-MHz-wide transmit band. As in the authors' prior work, target detection is demonstrated by receiving at least one harmonic of at least one transmit frequency. In the present work, experiments confirm that the phase of a harmonic reflected from a radio-frequency electronic target at a standoff distance is linear versus frequency. Similar to traditional wideband radar, the change of the reflected phase with respect to frequency indicates the range to the nonlinear target.

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Section: Wireless Experimentsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase responses of harmonics reflected from radio-frequency electronics

et al. 2016

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“…Consequently, the nth harmonic received at the radar, f r , has a bandwidth of nB centered around n f 0 , due to the linear multiplication of the fundamental frequency band. For a harmonic radar operating at the nth harmonic, the maximum unambiguous range to the target, R max , and the down range resolution,∆R, are given by, respectively [52] …”

Section: Unambiguous Range and Range Resolutionmentioning

confidence: 99%

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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“…One of the less common nonlinear mechanisms is passive intermodulation (PIM) distortion, which occurs in antennas [1,2], cables, connectors [2][3][4], metal-to-metal junctions [5,6], and various components [7,8]. A recent development has led to the exploitation of nonlinearities in electronic circuits to detect and track nonlinear targets [9][10][11][12][13][14][15].…”

Section: Introductionmentioning

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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Nonlinear synthetic aperture radar imaging using a harmonic radar

Cited by 14 publications

References 22 publications

Phase responses of harmonics reflected from radio-frequency electronics

Phase responses of harmonics reflected from radio-frequency electronics

Static and Moving Target Imaging Using Harmonic Radar

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

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