Random Noise Radar System Research Articles

A Portable Real-Time Digital Noise Radar System for Through-the-Wall Imaging

We present the design and implementation of a portable, digital, real-time random noise radar system operating in the ultrahigh frequency range for through-the-wall detection and imaging. Noise radar technology is combined with modern digital signal processing approaches to architect a system to covertly perform range imaging of obscured stationary and moving targets as well as to detect the presence of humans via micro-Doppler detection combined with empirical mode decomposition. We model the propagation and sampling nonidealities in the system and propose techniques to overcome the effect of these nonidealities. Experimental results demonstrate the system's capability to image target scenes and characterize human activity from different stand-off distances.

Design and Implementation of True Random Noise Radar System

The design theory and experimental results of a true random noise radar system are presented in this paper. Target range information can be extracted precisely by correlation processing between the delayed reference and the signal received from a target, and the velocity information by the Doppler processing with successive correlation data. A K-band noise radar system was designed using random FM noise signal, and the characteristics of the fabricated system were examined with laboratory and outdoor experiments. A C-band random FM noise signal was generated by applying a low-frequency white Gaussian noise source to VCO(Voltage Controlled Oscillator), and a K-band Tx noise signal with 100 MHz bandwidth was obtained by using a following frequency multiplier. Two modified wave-guide horn arrays were designed and fabricated, and used for the Tx and Rx antennas. The required amount of Tx/Rx isolation was attained by using a coupling cancellation circuit as well as keeping them apart with predetermined spacing. A double down-conversion scheme was used in the Rx and reference channels, respectively, for easy post processing such as correlation and Doppler processing. The implemented noise radar performance was examined with a moving bicycle and a very high-speed target with a velocity of 150 m/s. The results extracted by the Matlab simulation using the logging data were found to be in a reasonable agreement with the expected results.

Monopulse radar based on spatiotemporal correlation of stochastic signals

The theory and technique of angle-of-arrival (AOA) estimation using random-noise or other stochastic transmit waveforms is addressed. The additional uncertainties induced by signal itself and the statistical complexity of the received signals result in major challenges. The statistical properties of the random-noise interferometer and monopulse radar system are studied and compared theoretically using an approximation method. Furthermore, a random-noise coherent correlation receiver (CCR) architecture is proposed. The concept of mean monopulse characteristic curve (MMCC) is introduced. Experimental results using an X-band random-noise monopulse radar system validate the theoretical predictions of random-noise monopulse characteristics and suggest potential applications such as surveillance, imaging, and maneuvering target tracking.

Implementation of fully polarimetric random noise radar

A heterodyne correlation receiver technique has been developed for coherent processing of backscatter data acquired by a radar system transmitting ultrawideband (UWB) random noise waveforms. In such a receiver, the reflected signal is correlated with a time-delayed and frequency-shifted version of the transmitted waveform, which is able to provide the phase of the reflected waveform. We describe the implementation of fully polarimetric capability in a coherent random noise radar system operating in the ultrahigh frequency (UHF) range designed for foliage penetration (FOPEN) applications. Using this implementation, the polarimetric response of various foliage targets has been characterized.

Broadband polarization interferometric time-integrating acousto-optic correlator for random noise radar

We describe a time-integrating acousto-optic correlator (TIAOC) developed for imaging and target detection using a wideband random-noise radar system. This novel polarization interferometric in-line TIAOC uses an intensity-modulated laser diode for the random noise reference and a polarization-switching, self-collimating acoustic shear-mode gallium phosphide (GaP) acousto-optic device for traveling-wave modulation of the radar returns. The time-integrated correlation output is detected on a 1-D charge-coupled device (CCD) detector array and calibrated and demodulated in real time to produce the complex radar range profile. The complex radar reflectivity is measured in more than 150 radar range bins in parallel on the 3000 pixels of the CCD, improving target acquisition speeds and sensitivities by 150 over previous serial analog correlator approaches. The polarization interferometric detection of the correlation using the undiffracted light as the reference allows us to use the full acousto-optic device (AOD) bandwidth as the system bandwidth. Also, the experimental result shows the fully complex random-noise signal correlation and coherent demodulation without an explicit carrier, demonstrating that optically processed random-noise radars do not need a stable local oscillator.

Radar penetration imaging using ultra-wideband (UWB) random noise waveforms

Ultra-wideband (UWB) radar has been proven to be a very powerful tool for high-resolution penetration imaging of obscured objects. The authors discuss a radar penetration imaging technique using UWB random noise waveforms. The theoretical foundations for random noise radar, the random noise radar imaging model, and the synthetic aperture radar (SAR) image formation algorithm are presented. Typical field test results using an experimental random noise radar system are demonstrated.

Generalised wideband ambiguity function of a coherent ultrawideband random noise radar

A coherent ultrawideband (UWB) random noise radar system has been developed and field tested at the University of Nebraska–Lincoln (UNL). A heterodyne correlation technique based on a time-delayed and frequency-shifted replica of the transmit waveform is used to inject coherence within this system. The radar's combined range and range rate resolution characteristics were investigated using the generalised wideband ambiguity function. As in the narrowband random noise waveform case, range and range rate resolutions can be controlled independently, the former being inversely related to the transmit bandwidth, while the latter is inversely related to the bandwidth of the integrating filter. It is also shown that UWB waveforms are not suitable for accurate range rate estimation due to the extended Doppler-spread parameter, i.e. the product of the transmit bandwidth and the target range rate, unless the correlator is matched in the delay rate as well.

Ultra-wideband continuous-wave random noise arc-SAR

A coherent ultra-wideband random noise radar system operating in the 1-2-GHz frequency range has been developed at the University of Nebraska. A unique signal processing procedure based on heterodyne correlation techniques preserves phase coherence within the system, thereby enabling it to be used for synthetic aperture radar (SAR) imaging. Data acquisition is performed using a rotating boom with antennas installed atop a van containing radar equipment. This setup facilitates a simple and low-cost mobile SAR implementation, best suited for short-range quasi-stripmap Arc-SAR imaging. The use of ultra-wideband signals provides reasonable resolution of the obtained imagery. The amplitude and the phase response of the system are used to form the frequency-domain target scattering profile matrix, which are then transformed into a SAR image. The paper discusses the theory of SAR imaging using random noise signals and presents a detailed description of the radar and experimental imagery obtained using this system.

Polarimetric processing of coherent random noise radar data for buried object detection

Random noise polarimetry is a new radar technique for high-resolution probing of subsurface objects and interfaces. The University of Nebraska has developed a polarimetric random noise radar system based on the heterodyne correlation technique. Simulation studies and performance tests on the system confirm its ability to respond to phase differences in the received signals. In addition to polarimetric processing capability and the simplified system design, random noise radar also possesses other desirable features, such as immunity from radio frequency interference. The paper discusses the theoretical foundations of random noise polarimetry, and presents examples out of the entire data set collected that demonstrate the usefulness of the image processing and Stokes matrix presentation to enhance target detection using the coherent random noise radar.

FOPEN SAR imaging using UWB step-frequency and random noise waveforms

The detection and identification of targets obscured by foliage have been topics of great interest. Several synthetic aperture radar (SAR) experiments have demonstrated promising images of terrain and man-made objects obscured by dense foliage, by using either linear frequency modulation (LFM) or step-frequency waveforms. We present here the methodology and results of a comparative study on foliage penetration (FOPEN) SAR imaging using ultrawideband (UWB) step-frequency and random noise waveforms. A statistical-physical foliage transmission model is developed for simulation applications. The foliage obscuring pattern is analyzed by means of the technique of paired echoes. The results of the comparative study demonstrates the ability of a UHF band UWB random noise radar to be used as a FOPEN SAR. Advantages of the random noise radar system include covert detection and immunity to radio frequency interference (RFI).