Sherif Sayed Ahmed

A Novel Fully Electronic Active Real-Time Imager Based on a Planar Multistatic Sparse Array

The interest in active millimeter-wave and microwave imaging systems is increasing due to their utilization in security, medical, and industrial applications. Imaging systems using monostatic arrays suffer from the high number of antenna positions, making a fully electronic solution very costly and impractical. Multistatic arrays, however, offer the chance for high reduction factors in the number of antennas, and then allow for fully electronic solutions. Here, a new array architecture is presented, which is suitable for real-time operation and is capable of delivering high image quality in means of resolution and dynamic range. Various technological solutions were developed for the imaging purpose, which are introduced in detail. An example array for operation from 72 to 80 GHz is demonstrated. The imaging system hardware is introduced, along with several imaging results of humans with concealed objects.

Advanced Microwave Imaging

Due to the enormous advances made in semiconductor technology over the last few years, high integration densities with moderate costs are achievable even in the millimeter-wave (mm-wave) range and beyond, which encourage the development of imaging systems with a high number of channels. The mm-wave range lies between 30 and 300 GHz, with corresponding wavelengths between 10 and 1 mm. While imaging objects with signals of a few millimeters in wavelength, many optically opaque objects appear transparent, making mm-wave imaging attractive for a wide variety of commercial and scientific applications like nondestructive testing (NDT), material characterization, security scanning, and medical screening. The spatial resolution in lateral and range directions as well as the image dynamic range offered by an imaging system are considered the main measures of performance. With the availability of more channels combined with the powerful digital signal processing (DSP) capabilities of modern computers, the performance of mm-wave imaging systems is advancing rapidly.

Low Power Wideband Receiver and Transmitter Chipset for mm-Wave Imaging in SiGe Bipolar Technology

This paper presents a chipset aiming at high resolution imaging systems for real-time people screening applications operating near the W-band. The frequency of operation ranges from 70 GHz to 82 GHz for optimal image resolution and depth of focus. The frequency generation for both receiver and transmitter chips consists of a mixer based frequency quadrupler with an input amplifier requiring -20 dBm of input power. The receiver RFIC contains 4 channels including LO generation and distribution. The measured receiver conversion gain is 23 dB with a SSB NF around 10 dB over a wide frequency range from 70 GHz up to 82 GHz. The transmitter RFIC includes LO generation, distribution and 4 output amplifiers with an output power of more than 0 dBm in a frequency range from 70 GHz to 82 GHz. Both ICs are supplied from a single 3.3 V supply voltage and the power consumption is 180 mW/channel for the receiver and 145 mW/channel for the transmitter.

Fully Electronic

The demand on advanced personnel screening systems led to the development of several active and passive imagers. Among them, active multistatic imaging ensures high image quality and allows fully electronic screening. An active E-band imager is presented in this paper, which measures in real-time and delivers images of 30-dB dynamic range. Imaging of humans is achieved by optimizing the acquisition time using a dedicated digital signal processing solution. This paper introduces the system hardware, the calibration procedure, and several measurement results demonstrating high quality imaging capabilities.

E

This work reports measurement results for the scanning of 2D and 3D objects in W-band (75 to 110 GHz) using active 2D planar arrays in multistatic configuration with digital beamforming technique. The image quality of the object reflectivity depends mainly on the frequency band, array configuration, signal polarization, and focusing method. Multistatic measurements allow for higher dynamic range, reduced antennas count and the feasibility for cross-polarization measurements. Measurements meet the theoretical expectation and the simulation results down to 4 mm resolution. Two multistatic arrays will be presented and compared in terms of image resolution, antennas count, SNR and digital processing needed.

-Band Personnel Imager of 2 m

Personnel screening is demanded nowadays for securing air traffic as well as critical infrastructures. The millimeter-waves are able to penetrate clothes and detect concealed objects, making them an attractive choice for security screening. Imaging methods based on multistatic architecture can ensure high quality imagery in terms of resolution and dynamic range. Following the advances in semiconductor technology, fully electronic solutions delivering real-time imaging are becoming feasible. Furthermore, the continuously increasing capabilities of digital signal processing units allow for the utilization of digital-beamforming techniques for image reconstruction, thus offering new opportunities for imaging systems to use sophisticated operation modes. Based on these modern technologies, an advanced realization addressing personnel screening in E-band with planar multistatic sparse array design is demonstrated.

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The interest on active millimeter-wave and microwave imaging systems is increasing nowadays due to their utilization in security, medical, and industrial applications. Imaging systems using monostatic arrays suffer from the high number of antenna positions, making a fully electronic solution very costly and impractical. Multistatic arrays, however, offer the chance for high reduction factors in the number of antennas, and then allow for fully electronic solutions. Here, a new array architecture is presented, which is suitable for real-time operation and is capable of delivering high image quality in means of resolution and dynamic range. An example array is demonstrated for operation from 72 to 80 GHz. The imaging system hardware is introduced, along with imaging results of humans.

Aperture Based on a Multistatic Architecture

A technique for the automatic detection of concealed dielectric objects carried by persons is presented. The method is applicable for microwave personnel scanners with sufficient signal bandwidth and is expected to resolve the trade-off with the privacy of the scanned persons, allowing for efficient detection without the need for a human operator. Algorithm description along with measurement results in W-band are presented.

Multistatic mm-Wave Imaging with Planar 2D-Arrays

The demand on advanced personnel screening systems led to the development of several active and passive imagers. Among them, active multistatic imaging ensures high image quality and allows fully electronic screening. An active E-band imager is introduced in this paper, which operates in real-time and delivers images of 30-dB dynamic range. Imaging of humans is achieved by optimizing the acquisition time using a dedicated digital signal processing solution.

Personnel screening with advanced multistatic imaging technology

At airport security checkpoints, authorities are demanding improved personnel screening devices for increased security. Active mm-wave imaging systems deliver the high quality images needed for reliable automatic detection of hidden threats. As mm-wave imaging systems assume static scenarios, motion effects caused by movement of persons during the screening procedure can degrade image quality, so very short measurement time is required. Multistatic imaging array designs and fully electronic scanning in combination with digital beamforming offer short measurement time together with high resolution and high image dynamic range, which are critical parameters for imaging systems used for passenger screening. In this paper, operational principles of such systems are explained, and the performance of the imaging systems with respect to motion within the scenarios is demonstrated using mm-wave images of different test objects and standing as well as moving persons. Electronic microwave imaging systems using multistatic sparse arrays are suitable for next generation screening systems, which will support on the move screening of passengers.