Recent MTI experiments using ARL's synchronous impulse reconstruction (SIRE) radar

Wall clutter mitigation for MIMO radar configurations in urban sensing

“…Instead of the use of orthogonal waveforms, a sequential multiplexing of the transmitters with simultaneous reception at multiple receivers is assumed. This signaling approach is a viable option for TWRI operations and is the salient feature of three known through-the-wall radar imaging systems; one is built by the Army Research Lab [8], the other by the Defense Research and Development Canada [9], and the third by MIT Lincoln Lab [4]. With the assumption of sequential multiplexing, a signal model can thus be developed based on single active transmitters.…”

Sparsity-based ranging for dual-frequency radars

“…More specifically, we are interested in a low cost, low complexity 1-D system for range-to-motion estimation. Instead of wideband pulsed or stepped-frequency radar systems, [7][8][9] we employ dual-frequency radars, which estimate the target range by phase comparison of the radar returns at two carrier frequencies. 10,11 The maximum unambiguous range for the dual-frequency approach depends on the frequency difference between the two carrier signals, and, thus, the two frequencies can be chosen to satisfy any desired range ambiguity, e.g., the spatial extent of the urban structure being interrogated.…”

Frequency-Modulated Interrupted Continuous Wave as Wall Removal Technique in Through-the-Wall Imaging

“…However the practical exploitation of crosspolarized components is limited because they are far weaker than co-polarized components and the generation and reception of pure polarizations through typical antennas for through-wall detection is challenging [22]. 4 In this paper we present an alternative wall removal technique for through-wall detection based on frequency modulated interrupted continuous wave (FMICW) waveforms; although used in the past for ocean sensing radar systems and ionospheric channel sounding, these signals have not been used yet in TTWD scenarios to the best of our knowledge. FMICW waveforms are switched on and off at the transmitter providing listening intervals at the receiver, which is switched with a complementary pattern; using suitable switching patterns it is possible to ensure that these listening intervals do not include undesired wall reflections, which are therefore attenuated or removed at the receiver.…”

“…The assumption is that stationary clutter, including wall reflections, does not change while performing measurements with moving targets; undesired signals can therefore be removed by simply subtracting data referring to different measurement instants. This subtraction can be performed either on raw data (coherent subtraction) [4][5], or on images after the application of beam-forming algorithms (non-coherent subtraction) [9]. The stationary background to be subtracted from the data can be estimated with more refined methods, for instance averaging the previous received signals [2], or with suitable weights to cope with targets that stop for a while during the measurement [3].…”

“…Different UWB waveforms have been used in these systems, including short impulses [2][3][4], noise [5] and pseudo-noise waveforms based on M-sequences [6], stepped frequency continuous wave (SFCW) signals [7][8][9], and frequency modulated continuous wave (FMCW) signals [10][11][12][13][14][15].…”