A body contacting substrate integrated waveguide (SIW) slot antenna with 1 GHz cut‐off frequency is presented for deep tissue thermometry. The SIW is shorted at one end and fed by an exponentially tapered microstrip line with a defected ground structure. An inclined (137°) off‐centred, asymmetric twin slot (23.3×3 mm2) etched on the SIW ground plane is optimised for resonance at 1.3 GHz and directional power deposition over 1.2–1.4 GHz. Antenna measurements indicate >10 dB return loss and high immunity to ambient electromagnetic interference. Antenna brightness temperature measurements indicate the ability to detect a 10 mm diameter hot spot with a temperature rise of 0.6°C at 45 mm depth from the phantom surface.

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This article presents the pre‐clinical evaluation of our custom‐built, single‐band microwave radiometer centered at 1.3 GHz for deep tissue thermometry, and a pilot study on volunteers for passive detection of inflammation in knee joints. The electromagnetic (EM) compatibility of the battery‐operated radiometer for clinical use was assessed as per International Special Committee on Radio Interference (CISPR) 22 standard. The ability to detect inflammation in knee joints was assessed using a substrate integrated waveguide antenna connected to the radiometer. EM compatibility tests carried out in the laboratory indicated device immunity to intentional radiated interference up to −20 dBm injected power in the global system for mobile communication frequency band, and pre‐compliance to CISPR 22 standard. Radiometer temperature measurements recorded at the lateral and medial aspects of both knees of 41 volunteers indicated mean temperature greater than 33°C for the diseased sites compared with the mean temperature of 28°C measured for the healthy sites. One‐way analysis of variance statistics indicated significantly (P < 0.005) higher radiometer temperature at the diseased sites unlike the healthy sites. Thus, the EM pre‐compliance of the device and the potential to measure deep tissue inflammation were demonstrated. Bioelectromagnetics. 2019;40:402–411. © 2019 Bioelectromagnetics Society.

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