Detection and Location of Nonlinear Scatterers Using Dort Applied With Pulse Inversion

Abstract

In this paper, an experimental demonstration employing the decomposition of the timereversal operator (known as DORT) in combination with pulse inversion is reported, allowing one to detect and selectively focus on nonlinear targets. DORT is a technique based on a multistatic configuration that separates the detected targets by means of eigendecomposition of the time reversal operator allowing for selective transmission of waves towards a target of interest. Pulse inversion is a technique that enhances harmonic responses while suppressing fundamental responses. By applying DORT with pulse inversion (PI-DORT), harmonic detection and selective transmission to detected nonlinear targets can be enhanced. The results from our experiment show that PI-DORT can effectively detect and separate nonlinear targets for selective transmission.

Ultrawideband planar bow‐tie with curved directive strips for gain enhancement

“…11 The initial motivation for obtaining added gain in the bow-tie antenna described here is due to its role as a scattering target in our active investigation of multistatic detection for smart far-field wireless power transmission. [12][13][14] This work employs a multistatic detection technique involving time-reversal and pulse inversion to permit nonlinear targets, formed by connecting a passive rectifier to an antenna (to form a rectenna), to be located and distinguished. Because this technique is based on detection of harmonic responses, the antenna must have an ultrawide bandwidth and enhanced gain will result in increased backscattered energy.…”

Embedded Resonances for Discrimination of Multiple Passive Nonlinear Targets Applicable to Dort

“…Therefore, by feeding the array using the eigenvectors associated with a given eigenvalue, it is possible to selectively transmit waves onto a detected target of interest, either physically for focusing electromagnetic energy at the scatterer or virtually for imaging purposes. For this reason, DORT has been studied for various applications [1][2][3][4][5][6][7][8][9][10][11].…”

“…A recent demonstration has shown that DORT can also be applied to detection of passive nonlinear scatterers in the presence of linear scatterers [10,11]. Nonlinear scatterers refer to electronic devices containing semiconductor junctions which can generate harmonic responses upon excitation.…”

“…Nonlinear detection has been studied for applications such as detection of RF electronics, insect tracking, RFID, temperature sensing, and monitoring of human activities [12][13][14][15][16][17]. As for DORT applied to nonlinear scatterers, due to its ability to selectively focus electromagnetic energy at a scatter in addition to detection, it could find applications in wireless power transfer where harmonic responses from passive rectifiers can be exploited for detection and subsequent selective focusing (beamforming) to concentrate wireless power at a desired device [10,11]. Additionally, harmonic detection and selective focusing via DORT may also be used to adaptively send power or information to passive biomedical implants or small sensors for potential IoT applications.…”

“…When DORT is applied to nonlinear targets, the eigenvalues appearing in the harmonic bands indicate the presence of nonlinear scatterers in the probed environment. Furthermore, applying pulse inversion (PI) in addition to DORT suppresses the fundamental and odd-ordered harmonics while retaining the even ordered harmonics, thereby rejecting clutter from linear scatterers [11,18]. PI can be particularly useful when using wideband signals as there may exist some overlap between the harmonic bands.…”