Micro-Fabricated DC Comparison Calorimeter for RF Power Measurement

Sensors

Bilel Neji¹  Jing Xu¹  Albert H. Titus¹ 

[1] Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA; E-Mails:

关键词: RF power sensor;    micro-calorimeter;    microfluidics;    temperature sensor;    DC comparison;   

DOI  :  10.3390/s141120245

来源: mdpi

【 摘 要 】

Diode detection and bolometric detection have been widely used to measure radio frequency (RF) power. However, flow calorimeters, in particular micro-fabricated flow calorimeters, have been mostly unexplored as power meters. This paper presents the design, micro-fabrication and characterization of a flow calorimeter. This novel device is capable of measuring power from 100 μW to 200 mW. It has a 50-Ohm load that is heated by the RF source, and the heat is transferred to fluid in a microchannel. The temperature change in the fluid is measured by a thermistor that is connected in one leg of a Wheatstone bridge. The output voltage change of the bridge corresponds to the RF power applied to the load. The microfabricated device measures 25.4 mm × 50.8 mm, excluding the power supplies, microcontroller and fluid pump. Experiments demonstrate that the micro-fabricated sensor has a sensitivity up to 22 × 10⁻³ V/W. The typical resolution of this micro-calorimeter is on the order of 50 μW, and the best resolution is around 10 μW. The effective efficiency is 99.9% from 0–1 GHz and more than 97.5% at frequencies up to 4 GHz. The measured reflection coefficient of the 50-Ohm load and coplanar wave guide is less than −25 dB from 0–2 GHz and less than −16 dB at 2–4 GHz.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.