SIW Slot Antenna for Passive Measurement of Thermal Anomalies in Biological Tissues

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 mm 2 ) 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.