Mm-wave Sensor Research Articles

Energy Beamforming in Wireless Powered mmWave Sensor Networks

This paper studies the beneficial combination of wireless power transfer and millimeter-wave (mmWave) communications in wireless sensor networks. In particular, an mmWave wireless powered sensor network is considered, where the access point (AP) employs beamforming techniques to transfer energy to the sensors of a selected sector of the cell. The served sensors harvest and store energy from the received signal, and use it to power their uplink transmissions. We consider a random energy beamforming scheme but also propose several intelligent schemes that steer the beam to specific areas of the cell by considering the sensors' locations. This setup is investigated from a large-scale point-of-view where spatial randomness is considered with the aid of Poisson point processes. The performance of the network is described in terms of the energy outage probability and the beam outage probability. We show that, depending on the scenario, each of the considered energy beamforming schemes can provide significant gains to the network's performance. Finally, we study an event monitoring application of our theoretical framework, where the active sensors observe a random event in the network and the AP attempts to estimate it based on the received information; this scenario is evaluated in terms of the estimation's mean squared error.

Contactless monitoring of food drying and freezing processes with millimeter waves

Millimeter (mm) waves are of interests to monitor the properties of interest (POIs) of food products which are opaque for optical and infrared frequencies as they not suffer from all the atomic and intermolecular absorption processes situated in the latter bands of the Electromagnetic (EM) spectrum. They also offer a higher penetration depth into water containing products than the IR domain. With respect to the microwave domain, they are less perturbed by ionic contributions of food products, hydration shell effects and finally they offer a higher spatial resolution compared to microwaves. In the considered mm-wave frequency range, the dipole moment of free water molecules plays a dominant role compared to the other constituents, hence the electromagnetic interaction depends mainly on the amount and phase state of free water present in food products. These features make mm-wave based sensors an appealing alternative for monitoring and quality control of food processes. However, the effectiveness of mm-wave sensing solutions has not yet been explored in the food industry. In this paper, we present a real time, contactless and non-destructive sensor methodology based on mm-waves to monitor food processes. An analytical model is developed to estimate the dielectric properties of food products with varying POIs and to establish the relation between the mm-wave sensor's output and the POIs. A drying and freezing process of potato slabs are monitored by measuring the transmission and reflection coefficients by means of mm-wave sensors. The theoretical and experimental results are compared and validated. It will be proven that mm-wave based sensors are a promising real time, contactless and non-destructive monitoring tool for food quality control.

A Newly Developed mm-Wave Sensor for Detecting Plaques of Arterial Vessels.

Microcalcifications within the fibrous cap of the arteriosclerotic plaques lead to the accrual of plaque-destabilizing mechanical stress. New techniques for plaque screening with small detectors and the ability to differentiate between the smooth and hard elements of plaque formation are necessary. Vascular plaque formations are characterized as calcium phosphate containing structures organized as hydroxylapatite resembling the mineral whitlockite. In transmission and reflexion studies with a simple millimeter wave (mm-wave)-demonstrator, we found that there is a narrow window for plaque detection in arterial vessels because of the tissue water content, the differentiation to fatty tissue, and the dielectric property of air or water, respectively. The new sensor is based on a sensing oscillator working around 27 GHz. The open-stub capacitance determines the operating frequency of the sensor oscillator. The capacitance depends on the dielectric properties of the surrounding material. The sensor components were completely built up in surface mount technique. Completed with a catheter, the sensor based on microwave technology appears as a robust tool ready for further clinical use.

Wireless Biometric Individual Identification Utilizing Millimeter Waves

Biometrics offer a personal and convenient way of keeping our identities and our data secure. Here, we introduce a method of using mm-wave sensors to identify various individuals. In our system prototype, the compact radar sensor has two transmit antennas and four receive ones. The transmitter(s) send a sequence of signals which are reflected and scattered from a nearby part of the body of a user (a hand in our demo case). Different signal processing algorithms are applied to the received signals in order to create a rich feature dataset. In our demo system, the resulting dataset is classified using a random forest machine learning model, which is shown to facilitate identifying a group of individuals with high accuracy. This technology has promising implications in terms of using mm-wave radars as an independent or an auxiliary tool for biometric authentication.

A mm-Wave Sensor for Remote Measurement of Moisture in Thin Paper Layers

We present the design and performance of a moisture sensor operating at 200 GHz for remote measurement of water content in paper. The system aims at industrial processes such as offset print and paper production. The moisture content in the paper is derived through an accurate measurement of the loss of a signal transmitted through the paper. The system is designed to achieve high accuracy in the measurement of the loss presented by the paper, not affected by 1/f or drift noise. The sensor is capable of resolving 0.005 dB loss achieving a moisture resolution of 0.1% for moisture content higher than 15%. The resolution can be improved if necessary in exchange for longer measurement times. The sensor is tested in offset print and paper production processes and measured values are compared to laboratory measured samples of the paper.

Design and simulation of a high efficiency Rotman lens for mm-wave collision avoidance sensor

Multi-beam approaches using beamforming antenna array architectures have been identified as one solution for overcoming the limited fields-of-view provided by highly directional mm-wave sensors. They are also ideal front end systems for collision avoidance devices. Rotman lenses offer a compact, rugged and reliable alternative to electronically scanned antenna technologies but architectures that operate at frequencies <20GHz perform poorly at higher frequencies on account of greater losses and dispersion. This paper outlines the design process for providing Rotman-based lenses, examining various levels of simulation that are needed for designs that function at K and W-band frequencies. The impact of using microstrip structures is demonstrated. A key advantage of our approach is that it is compatible with monolithic fabrication, leading the way towards smart collision avoidance sensors.