DESIGN OF MEDICAL RADIOMETER FRONT-END FOR IMPROVED PERFORMANCE.

Q3 Engineering
O Klemetsen, Y Birkelund, S K Jacobsen, P F Maccarini, P R Stauffer
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引用次数: 43

Abstract

We have investigated the possibility of building a singleband Dicke radiometer that is inexpensive, small-sized, stable, highly sensitive, and which consists of readily available microwave components. The selected frequency band is at 3.25-3.75 GHz which provides a reasonable compromise between spatial resolution (antenna size) and sensing depth for radiometry applications in lossy tissue. Foreseen applications of the instrument are non-invasive temperature monitoring for breast cancer detection and temperature monitoring during heating. We have found off-the-shelf microwave components that are sufficiently small (< 5 mm × 5 mm) and which offer satisfactory overall sensitivity. Two different Dicke radiometers have been realized: one is a conventional design with the Dicke switch at the front-end to select either the antenna or noise reference channels for amplification. The second design places a matched pair of low noise amplifiers in front of the Dicke switch to reduce system noise figure.Numerical simulations were performed to test the design concepts before building prototype PCB front-end layouts of the radiometer. Both designs provide an overall power gain of approximately 50 dB over a 500 MHz bandwidth centered at 3.5 GHz. No stability problems were observed despite using triple-cascaded amplifier configurations to boost the thermal signals. The prototypes were tested for sensitivity after calibration in two different water baths. Experiments showed superior sensitivity (36% higher) when implementing the low noise amplifier before the Dicke switch (close to the antenna) compared to the other design with the Dicke switch in front. Radiometer performance was also tested in a multilayered phantom during alternating heating and radiometric reading. Empirical tests showed that for the configuration with Dicke switch first, the switch had to be locked in the reference position during application of microwave heating to avoid damage to the active components (amplifiers and power meter). For the configuration with a low noise amplifier up front, damage would occur to the active components of the radiometer if used in presence of the microwave heating antenna. Nevertheless, this design showed significantly improved sensitivity of measured temperatures and merits further investigation to determine methods of protecting the radiometer for amplifier first front ends.

提高医用辐射计性能的前端设计。
我们已经研究了建造一种廉价、小尺寸、稳定、高灵敏度的单波段迪克辐射计的可能性,它由现成的微波元件组成。所选频段为3.25-3.75 GHz,这为有损耗组织中的辐射测量应用提供了空间分辨率(天线尺寸)和传感深度之间的合理折衷。该仪器的预期应用是用于乳腺癌检测的非侵入性温度监测和加热过程中的温度监测。我们已经发现现成的微波元件足够小(< 5毫米× 5毫米),并提供令人满意的整体灵敏度。已经实现了两种不同的迪克辐射计:一种是传统的设计,在前端有迪克开关来选择天线或噪声参考通道进行放大。第二种设计在Dicke开关前放置一对匹配的低噪声放大器,以降低系统噪声系数。在构建辐射计的原型PCB前端布局之前,进行了数值模拟以测试设计概念。这两种设计在以3.5 GHz为中心的500 MHz带宽上提供了大约50 dB的总功率增益。尽管使用三级联放大器配置来增强热信号,但没有观察到稳定性问题。在两个不同的水浴中校准后,测试了原型的灵敏度。实验表明,与迪克开关在前面的其他设计相比,在迪克开关之前(靠近天线)实现低噪声放大器时,灵敏度更高(36%)。在交替加热和辐射读数期间,还在多层模体中测试了辐射计的性能。经验测试表明,首先配置Dicke开关时,在微波加热应用过程中,开关必须锁定在参考位置,以免损坏有源元件(放大器和功率计)。对于前面有一个低噪声放大器的配置,如果在微波加热天线的存在下使用,将会损坏辐射计的有源组件。尽管如此,这种设计显示出对测量温度的显着提高的灵敏度,值得进一步研究以确定保护放大器第一前端辐射计的方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Progress In Electromagnetics Research B
Progress In Electromagnetics Research B Engineering-Electrical and Electronic Engineering
CiteScore
2.70
自引率
0.00%
发文量
14
期刊介绍: Progress In Electromagnetics Research (PIER) B publishes peer-reviewed original, comprehensive and tutorial review articles on all aspects of electromagnetic theory and applications. It is a new journal in 2008, and freely available to all readers via the Internet. Manuscripts submitted to PIER B must not have been submitted simultaneously to other journals. Authors are solely responsible for the factual accuracy of their articles, and all articles are understood to have received clearance(s) for publication.
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