The use of surface acoustic wave (SAW) devices is a widely adopted method for implementing unique identification tags that operate completely passively and can be interrogated wirelessly. Interrogation can be done in the time- or frequency-domain, where in the latter case bandwidth is a restraining factor. Conventional signal evaluation is based on the fast Fourier transformation (FFT), which suffers from resolution limitations. Modern model-based frequency estimators have been investigated for SAW ID-tag identification. A state-space algorithm is applied to measured data and compared to FFT evaluation results.
In frequency modulated continuous wave sensor systems for object distance measurement, use of the fast Fourier transformation for frequency estimation is widely adopted because of its comparably low execution time and available implementations. Inherent resolution restrictions make modern state-space based frequency estimators a viable alternative to this approach. Estimation of the correct model order, crucial to accurate distance measurement when used in a setup with an unknown number of targets, may be avoided by using active transponders. In this paper, application of a state-space frequency estimator is investigated with the use of measurement data in a system with an a priori known number of active targets. Evaluation results are analyzed and compared to performance of the Fourier transformation.
In this paper a novel local position measurement (LPM) technology is presented. The LPM system operates in the 5GHz ISM band and consists of lightweight transponders of which the 3-D position is measured, and base stations located around the measurement field. Transponder and base stations operate similar to conventional radar systems and consist of RF electronics as well as signal processing elements. The RF-part in the transponders is the key element for the position measurement system. The measurement accuracy of the LPM system is in the range of some centimeters despite a high measurement rate of 1000 measurements per second.
This contribution describes the components necessary for measurement of the three-dimensional local position of objects with high accuracy and high measurement rate. The methodology is based on the FMCW (frequency modulated continuous wave) technology in state of the art technology described as sensor system. A high speed real-time network collects data and transfers it to a master processing unit (MPU) where 3-D position data is calculated. It is described how to measure and how to process position data for a local, wide area measurement system. Results are shown for a series of static measurements and an outdoor Motocross race.
The objective of the presented research program is to design and develop a prototype system for measuring the length of a moving log in an outdoor environment. Investigations on different sensor concepts proved the suitability of certain radar and optical solutions. The two systems, one applying microwaves and evaluating the Doppler-shift, the other using digital image processing are described in detail.
Surface acoustic wave (SAW) devices, used as filters or diplexers, are well established components in communications applications like in mobile handsets or television sets. The characteristics of SAW devices make them also well suitable for the application of wireless sensors or wireless identification tags. A great advantage of SAW sensors is their completely passive operation without the need for additional power supplies. SAW sensors can be designed to sense several physical or chemical quantities like temperature, pressure, stress, or gas concentration. During operation of the wireless sensor the energy delivered from an RF pulse sent by an interrogation unit is picked up by the antenna, stored in the surface acoustic wave, modified by the sensor effect and is finally transmitted back to the interrogation unit. In this paper the basic operating principles of SAW devices are reviewed and two applications, a state-of-the-art tire pressure sensor and a moisture sensor, are presented.
In this contribution the various influences on the accuracy of a near range precision radar are described. The front-end is a monostatic design operating at 34 - 36.2 GHz. The hardware configuration enables different modes of operation including FM-CW and interferometric modes. To achieve a highly accurate distance measurement, attention must be paid to various error sources. Due to the use of a six-port it is rather complicated to determine the corresponding error propagation. In the following the results of investigations on how to achieve an exceptional accuracy of +/- 0.1 mm are described.
KEYWORDS: Sensors, Radar, Calibration, Phase measurement, Digital signal processing, Signal processing, Receivers, Distance measurement, Diodes, Monte Carlo methods
The application of six-port technology in the receiving part of a radar front-end is described in this contribution. This receiver allows measuring magnitude and phase of the radar signal without the need of down-conversion. According to the applications and the availability of the devices needed for assembling the prototype sensor the frequency of operation was set to 35 GHz. The structure of the six-port as well as the calibration and measurement algorithms are described in detail. The accuracy of the phase measurement is 2 - 10 degrees depending on the power level of the signal. Another key element of the proposed radar sensor is a direct frequency counter. With this circuit it is possible to measure the frequency of operation within 120 microseconds. The accuracy of the distance reading of the radar is directly related to the accuracy of the frequency measurement and has reached 0.1 mm.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.