Danny Hardon

Linear FM radar operating in the Tera-Hertz regime for concealed objects detection

Sub-millimeter and Terahertz waves maintain reasonable penetration depth in certain common materials, such as cloth, plastic, wood, sand and soil. Therefore, THz radiation can detect concealed weapons since many non-metallic, non-polar materials are transparent to this type of radiation (and are not transparent to visible radiation). Target compounds such as explosives and illicit drugs have characteristic THz spectra that can be used to identify these compounds. Investigation, design and development of a sub-millimeter wave remote sensing RADAR system for homeland security applications are presented. The RADAR, operating at 330GHz is based on transmission of a frequency modulated continuous wave (FMCW) and aimed at detection of concealed objects for ranges up to 20m. The system consists of 2 horn-lens antennas integrated with a homodyne transceiver. The synthesized linear FM signal with a frequency span of 200MHz at X-band is multiplied by a factor of 32 to generate the transmitted Tera-Hertz wave. Using a splitter, the signal is fed to an antenna and to a local oscillator port of a second harmonic balanced mixer. As a result, an intermediate frequency signal is obtained, containing the information on the target. Distance measurements were made by performing data acquisition and signal processing commercial programs, resulting in a range resolution better than 1cm. Preliminary Tera-Hertz imaging was also carried out to perform a three-dimensional image of the object.

FMCW MM-wave non-imaging sensor for detecting hidden objects

MM-wave sensor operating at 94 GHz has been developed for detecting hidden objects such as weapons, explosives etc. It is based on a frequency modulated continuous wave (FMCW) and includes the two high gain horn-lens antennas integrated with a homodyne transceiver. The synthesized linear FMCW signal in Ku-band is multiplied by a factor 6 to generate the transmitted signal at 94 GHz. An intermediate frequency (IF) signals obtained in the output port of the mixer is employed for detecting hidden objects. Post detecting procedure was performed using and MatLab processing. Experiments have demonstrated an efficiency of the designed sensors for homeland security applications.

Quasi-noise illumination in mm-wave imaging: From concept to realization

The paper describes the W-band single-pixel imaging de tector with a pulse-noise source in the Tx-channel and the direct detecting circuitry in the Rx-channel. The detector is maintained on X-Y programmable scanner controlled by LabView interface which is integrated with MatLab used for online image reconstruction. The application of an incoherent illumination generated by the frequency-limited quasi noise source improves image quality compared with the coherent mode widely used in conventional active imagers.

Complex Permittivity Measurements of Textiles and Leather in a Free Space: An Angular-Invariant Approach

The paper describes the complex permittivity measurements of textiles and leathers in a free space at 330 GHz. The destructive role of the Rayleigh scattering effect is considered and the angular-invariant limit for an incidence angle has been found out experimentally within 25–30 degrees. If incidence angle exceeds this critical parameter, the uncertainty caused by the Rayleigh scattering is drastically increased preventing accurate measurements of the real and imaginary parts of a bulky material. The phenomenon must be taken into consideration in predicting shielding effectiveness of materials covering hidden object in concealed threat detection with millimeter-wave radar systems.

Single pixel THz detector for remote imaging

High-resolution single-pixel detector operating near 0.33 THz is described. It consists of FMCW transmitter based on multiplying chain (x32) and heterodyne receiver with sub-harmonic mixer. The X-band FMCW synthesizer is employed as a driver of multiplying chain and LO of the mixer. The Gaussian-beam antennas are used in the Rx and Tx channels. The detector was mounted on the scanning platform and can be employed in various homeland security applications where the remote detection of hidden objects both metal and plastics is required.

W-Band Rectenna Coupled With Low-Barrier Mott Diode

Design and characterization of a W-band rectenna, consisting of a 2 × 2 patch sub-array integrated with matching elements and rectifying circuitry is presented. The key element of the rectenna is a Mott diode that has permitted considerable improvement of RF-to-DC conversion efficiency in comparison with commercially available GaAs mm-wave diodes. The experimental setup was equipped by two focusing lenses, allowing a concentration of RF power within the beam spot of a 1 cm diameter at a distance of 1 m. The tuneable W-band source delivering 0.4 W RF CW power was employed to perform large-signal experiments and to measure load characteristics of the rectenna. The measured RF-to-DC conversion efficiency with the single Mott diode is approximately 17%, which is approximately 5 times higher than the commercial counterpart (Microsemi).

Detecting power lines using 330GHz FMCW sensor

330 GHz sensor is developed for detecting power lines along the traffic of low altitude flying aircrafts. It is based on a frequency modulated continuous wave (FMCW) mode of operation and includes the two high gain horn-lens antennas integrated with a homodyne transceiver. The FMCW signal at X-band is multiplied by a factor of 32 to generate the transmitted signal. An intermediate frequency (IF) signal obtained in the output port of the 2-nd harmonic mixer is employed for processing. Power line detection was done by data acquisition unit based on LabView interface and resulting in a range resolution about 5cm. Experiments carried out with real-world power lines have demonstrated an applicability of sub-mm wave range for improving flight safety conditions of such aircrafts.

Millimeter-Wave Imager With Multi-Source Noise Illumination

This paper presents the design and testing results of a millimeter-wave imager with multi-source illumination of targets. The four full W-band noise sources placed at the vertices of a kite-shape are used to improve the uniformity of illumination. The antenna system consists of an offset parabolic focusing flapping mirror of 30-cm diameter fed by a scalar corrugated horn. The 3-dB diameter of the beam is ~10 mm at a distance of ~2.3 m. The mirror collects signals back scattered by the target during the scanning process. A singlepixel demonstrator has been assembled and tested, allowing an image to be acquired at a rate of 5 s/frame. A LabVIEW interface combining six independent sub windows has been developed to provide continuous observation of the restored images in various target positions. In addition, the examples of millimeter images of metallic and non-metal objects are presented.

Microwave target enhancement using the perspectives of multiple-angular images

This In this paper, we describe the image processing techniques needed to produce sharp images using microwave technology. A scanning system produces a set of images representing the return of an object at several angles. By treating each point as a vector and calculating the autocorrelation function, we can produce relatively sharp images of the target. The technology can be used for detecting hidden targets.

Monitoring of atmosphere attenuation in W-band

The paper describes a system aimed at monitoring variations of the atmospheric attenuation in W-band. It consists of an Rx - Tx module designed and assembled to be used for operating at 95 GHz frequency. The transmitting part of this module includes W-band sources generating 1 W pulse of duration 100 ns. The receiving part consists of the input LNA and balanced mixer driven by LO and IF active detector. Single 48 inches Cassegrain antenna (gain 57 dB and 3 dB beamwidth = 0.1 degrees) is used for both transmission and reception of the signal reflected from the target placed on the distance about 137 m. The azimuth-elevation rotary joint based on overmoded corrugated waveguides was employed in order to provide accurate positioning to this antenna. Examples of monitoring the variations of attenuation during rain fall are presented, too.