Microwave sensor

Almost all microwave methods are non-contact [1] and allow simultaneous measurement of the magnitude and the frequency of vibrations. The distance between the inspected surface and microwave sensor can vary from several millimeters to a few meters. However, the accuracy of the measurement of vibration magnitude also depends on a distance between the microwave sensor and the object as well as the shape of the inspected surface. 

Dual-technology sensors consist of two different sensor technologies incorporated together into one sensor unit. For example, a dual technology sensor could consist of a passive infrared detector and a monostatic microwave sensor integrated into the same sensor unit. 

KDC Technology has developed a cost-effective microwave sensor technique for monitoring constituents and moisture in a wide variety of products including foods (KDC 1993). The KDC sensor is adaptable to measurement of process parameters of products contained in tubes, chutes, bins, vessels as well as moving on conveyer lines. 

In the case of pulverized coal flow measurement, the concentration of the pulverized coal is measured by low-power, low-frequency microwave sensors. The variation in the microwave transmission characteristic (dielectric load) is caused by the changing coal concentration, which produces shifts in measurement frequency. The resulting quantifiable values indicate the coal density. This concentration measurement is performed by a microwave transmitter and a microwave receiver, as shown in Figure 3.90. The velocity of the pulverized coal is measured by two identical microwave devices by crosscorrelation. Here, the pair of sensors detect the stochastic signals resulting from the charged coal particles, which are nearly identical but shifted by the time the pulverized coal gets from one sensor to the other. 

The passive microwave sensor detects natural background microwave radiation. Oil slicks on water absorb some of this signal in proportion to their thickness. While this cannot be used to measure thickness absolutely, it can yield a measure of relative thickness. The advantage of this sensor is that it can detect oil through fog and in darkness. The disadvantages are the poor spatial resolution and relatively high cost. 

Fig. 5. Top left Laser-induced Raman backscatter (381 nm) and two fluorescence return signals (414, 482 nm) measured during an overflight over an oleyl alcohol slick and adjacent clean sea areas bottom left the simultaneously obtained passive microwave L-band data top right same lidar sensor, Raman backscatter (381 nm) and fluorescence return signal at 500 nm during an overflight over a Murban cmde oil spill and adjacent clean sea areas bottom right same passive microwave sensor, over an artificial oil spill in the New York Bight.

As a first step, short-range microwave sensors will be introduced that operate at a frequency of 24 GHz. These sensors can be used to build a virtual safety belt around the vehicle covering a variety of functions. 

Short-range microwave sensors are being introduced in series in the near future. The major benefit to the customer is the multi-usage capability of this sensor opening up the opportunity to build a sensor platform. 

Nyfors, E. and P. Vainikainen. 1989. Industrial Microwave Sensors. Norwood, MA Artech House. 

Electromagnetic sensors Microwave heaters Microwave near field sensors Microwave sensors... 

Haung M, Yanj J, Wang J, Peng J (2007) Microwave sensor for measuring the properties of a liquid drop. Meas Sci Technol 18(7) 1934-1938... 

Rowe DJ, Porch A, Barrow DA, Allender CJ (2013) Microfiuidic microwave sensor for simultaneous dielectric and magnetic characterization. IEEE Trans Microw Theory Tech 61(1) 234—243... 

R. Nakamura and A. Kajiwara, "Empirical study of stepped-FM UWB microwave sensor," Proc. IEEE Radio and Wireless Symposium (RWS 2010), pp. 363-366, Jan. 2011. 

Ryohei Nakamura, PhD, is a research associate in the University of Kitakyushu, Kitakyushu, Japan. His research interests include communication network systems, wireless communications, radio propagation, and measurement engineering. He contributed in the publications of numerous papers on ultra-wideband radio propagations, wireless sensors, microwave sensors, and patient care monitoring systems. 

The DSCS-III satellite offers six covert communications channels and is equipped with spatial user-jammer discrimination capability, which sometimes is known as antenna nulling capability, to achieve high discrimination performance. According to the published literature, two channels in this satellite system deploy high-efficiency 40 W TWTAs and the remaining four channels each use only 10 W TWTAs. This means that the total RF output of the TWTAs is 120 W. Assuming a DC-to-RF efficiency of 40% each, the DC input power required for the TWTAs will be close to 300 W. The batteries must supply this amount of DC power. In addition, additional DC power is required to operate the antenna stabilization mechanisms and the various electronics, electro-optic, and microwave sensors onboard the satellite. The solar panels must be capable of charging the batteries to meet all the DC power consumption. 

This section identifies rechargeable or secondary battery requirements best suited for communications and surveillance and reconnaissance satellites. The battery power requirements are strictly dependent on several factors, including launch orbits such as LEO, elliptical, or GSO orbital height the type of stabilization technique used (i.e., mono-spin, dual-spin, or three-axis configuration) satellite operational life attitude control system and the overall DC power requirements needed to power the electronic and electrical subsystems, the electro-optical and microwave sensors, and the attitude and stabilization control mechanisms. 

Microwave sensors are based on radiation and reception of electromagnetic radiation In the GHz range. Because of the Doppler effect, the frequency of the reflected wave will differ from that of the emitted wave In relation to the speed of the object reflecting the radiation. The reflected wave Is compared with the Initial emitted wave. 

The U.S. Bureau of Mines Research Center In Minneapolis, Minnesota, recently tested three types of warning sensors to be used when heavy trucks are backed up In mlnes. They tested Infrared, ultrasonic and microwave sensors. The microwave sensor system was most effective, especially because It was little affected by environmental conditions. A 10.525 GHz wave was used and the movement of an object In relation to the sensor was detected by the Doppler effect. When the truck was backing up, the system was able to detect the presence of a person at a distance of four to six meters. 

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