Multitone harmonic radar is presented. The radar transmits multiple closely-spaced tones and receives nonlinear mixing products as well as harmonics. Harmonic and multitone responses are recorded from commercially-available RF devices. An original method for discriminating between electronic targets, by receiving at least two nonlinear mixing products near a harmonic, is presented. Target detection is demonstrated experimentally for a novel pulsed two-tone harmonic radar. Experimental results are extrapolated to estimate radar design parameters to achieve a realistic standoff range.

An extensive review of nonlinear radar systems is performed. Emphasis is placed on designs relevant to detecting RF electronics that were not intentionally manufactured as visible radar targets. The state of the art in nonlinear radar is conveyed by presenting high-level system architecture, explaining the rationale behind design decisions pertaining to that architecture, and listing the specifications that nonlinear radar designers have achieved. The authors' recent advancements in nonlinear radar technology are summarized.

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.

Data about users is collected constantly by phones, cameras, Internet websites, and others. The advent of so-called ‘Smart Things’ now enable ever-more sensitive data to be collected inside that most private of spaces: the home. The first step in helping users regain control of their information (inside their home) is to alert them to the presence of potentially unwanted electronics. In this paper, we present a system that could help homeowners (or home dwellers) find electronic devices in their living space. Specifically, we demonstrate the use of harmonic radars (sometimes called nonlinear junction detectors), which have also been used in applications ranging from explosives detection to insect tracking. We adapt this radar technology to detect consumer electronics in a home setting and show that we can indeed accurately detect the presence of even ‘simple’ electronic devices like a smart lightbulb. We evaluate the performance of our radar in both wired and over-the-air transmission scenarios.

An extensive review of nonlinear radar systems is presented. Emphasis is placed on designs relevant to detecting electronics which were not intentionally manufactured as visible radar targets. The state-of-the-art in nonlinear radar is conveyed by presenting a high-level system architecture, explaining the rationale behind design decisions pertaining to that architecture, and listing the specifications that nonlinear radar designers have achieved. The authors’ recent advancements in nonlinear radar technology are summarized, with an emphasis on recent techniques used to linearize the radar transmitter and establish extremely high sensitivity in the radar receiver.