B. Kapilevich

Variety of Approaches to Designing Microwave Active Filters

Microwave active filters continue to attract the attention of specialists because of their unique performance. The paper is targeted at providing microwave and RF designers with an introduction to the state of the art including both of current tendencies and unsolved problems. Emphasis is placed on a physical interpretalion of general principles of design and practical realizations of microwave active filters.

Microwave sensor for accurate measurements of water solution concentrations

The paper presents results of sensitivity estimations of the microwave sensor designed for controlling concentration of various mixture solutions. It consists of the resonator supporting TM010 mode with the axial glass tube filled with the solution under test. Concentrations of both organic (sugar, alcohol) and inorganic (NaCl, KMnO4 ) water solutions were determined with high accuracy. The sensitivity of the sensor in determination of NaCl is 0.4 dB/(mg/ml) within the concentration range 0 - 1 %. It is about the two orders higher than sensitivity of the sensor based on near field dielectric resonator.

Effects of 100 GHz radiation on alkaline phosphatase activity and antigen-antibody interaction.

Equipment that generates microwave radiation (MWR) spanning the frequency range of 300 MHz-100 GHz is becoming more common. While MWR lacks sufficient energy to break chemical bonds, the disagreement as to whether MWR exposure is detrimental to cellular dysfunction may be difficult to clarify using complex systems such as whole animals, cells, or cell extracts. Recently, the high frequency range of terahertz (THz) radiation has been explored and sources of radiation and its detectors have been developed. THz radiation is associated with the frequency interval from 100 GHz to 20 THz and constitutes the next frontier in imaging science and technology. In the present study, we investigated the effect of radiation in the low frequency THz range (100 GHz) on two defined molecular interactions. First, the interaction of soluble or immobilized calf alkaline phosphatase with the substrate p-nitrophenylphosphate and second, the interaction between an antibody (mouse monoclonal anti-DNP) and its antigen (DNP). Irradiation of enzyme either prior to addition of substrate or during the enzymatic reaction resulted in small but significant reductions in enzyme activity. These differences were not observed if the enzyme had previously been immobilized onto plastic microwells. Exposure of immobilized antigen to radiation did not influence the ability of the antigen to interact with antibody. However, irradiation appeared to decrease the stability of previously formed antigen-antibody complexes. Our data suggest that 100 GHz radiation can induce small but statistically significant alterations in the characteristics of these two types of biomolecular interactions.

Optimized Microwave Sensor for Online Concentration Measurements of Binary Liquid Mixtures

This paper describes microwave sensors designed for online measurements concentration of binary liquid mixtures. It is based on the cylindrical resonator having axial glass tube filled with the liquid under test. The input coupling element has been optimized using 3D EM simulator (CST Microwave Studio) in order to reach maximum sensitivity and concentration resolution. The sensor can be calibrated for a variety of organic and inorganic binary mixtures. Examples of operation of the sensor with mixtures such as water-methanol, magnesium-sulphate, and water-sodium chloride-glucose are reported.

Detecting Hidden Objects on Human Body Using Active Millimeter Wave Sensor

The paper describes millimeter wave (MMW) sensors designed for detecting both metallic and nonmetallic objects placed on a human body and hidden under clothes. The sensor is based on the synchronized detection principle and estimating a power of back-scattered signal from hidden objects. Time-gating algorithm combined with preliminary determined threshold level has been implemented in order to reach detection probability of ~ 90% or more for metal and plastic hidden objects at the distance up to 3 m.

Non-Imaging MM-Wave FMCW Sensor for Pedestrian Detection

This paper describes a millimeter-wave sensor that is able to detect pedestrians, thereby reducing the likelihood of human road injuries or fatalities. The sensor consists of a transmit/receive channel module, operating in the millimeter-wave range (W-band) using frequency-modulated-continuous-wave mode. The laboratory prototypes of the sensor have been designed and tested in real-life environment. An analysis of system performance and experiments conducted has indicated a high-resolution, detection ability of both adults and children at a distance of up to 100-150 m.

Portable Passive Millimeter-Wave Sensor for Detecting Concealed Weapons and Explosives Hidden on a Human Body

This paper describes a portable passive millimeter-wave sensor designed for remote detection of both metallic and non-metallic objects hidden on a human body under cloth. The sensor is based on a directly detection and analyses of the energy emitted by a human body. The algorithm of detection estimates unimodality features of traces recorded in the process of a manual scan. The sensor demonstrates a detection probability in the laboratory environment close to 100% at a distance of up to 3 m for the tested samples of explosives and metal objects hidden under cloth.

Radiation measurements in the new tandem accelerator FEL

The Israeli tandem electrostatic accelerator FEL (EA-FEL), which is based on an electrostatic Van der Graaff accelerator was relocated to Ariel 3 years ago, and has now returned to operation under a new configuration. In the present FEL, the millimeter-wave radiation generated in the resonator is separated from the electron beam by means of a perforated Talbot effect reflector. A quasi-optic delivery system transmits the out-coupled power through a window in the pressurized gas accelerator tank into the measurement room (in the previous configuration, radiation was transmitted through the accelerator tubes with 40 dB attenuation). This makes it possible to transmit useful power out of the accelerator and into the user laboratories. After re-configuring the FEL electron gun and the e-beam transport optics and installing a two stage depressed collector, the e-beam current was raised to 2 A. This recently enabled us to measure both spontaneous and stimulated emissions of radiation in the newly configured FEL for the first time. The radiation at the W-band was measured and characterized. The results match the predictions of our earlier theoretical modeling and calculations.

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.

Microwave Characterization of Powders Using Multiresonance Cell

This paper describes the microwave characterization of powders using a multiresonance cell supporting TE10p modes in a rectangular cavity. An identification of the resonating modes excited in the cell has been done in order to extract the real and imaginary parts of a complex dielectric constant of the material under test. Calibration of the cell has been performed using the empty resonator. An error analysis was employed in order to estimate the uncertainty caused by coupling elements needed to connect the measuring cell with a network analyzer. The CST Microwave Studio solver was used to evaluate degrading measurement accuracy caused by a presence of coupling elements. Comparison of the measured data with 3-D electromagnetic simulation has demonstrated a good agreement. The validation of the method described has been done for the α-lactose monohydrate powder as a tested material at X-band. The role of density of powder has been estimated too. The same approach can be easily extended to the microwave characterization of other powder materials.