Bidirectional Leaky-Wave Antenna Based on Dielectric Image Line for Remote Vital Sign Detection at mm-Wave Frequencies

A bidirectional leaky wave antenna (LWA) with beam scanning capabilities was developed based on the dielectric image line for single-tone continuous-wave Doppler radar (DR) for remote vital sign monitoring (RVSM) in a dynamic environment. It consists of a conductor-backed copper dielectric image line with two of the same dielectric layers mounted on top of each other for performance improvement. A RO6010 substrate with high permeability is used for the top two layers. The bottom layer is a RT/duroid 5880 low permittivity substrate stacked on top of the copper DIL to prevent higher order modes from being excited in the DIL channel. The dominant mode of the DIL is perturbed by making holes periodically in the DIL, and fast-wave space harmonics are generated. The scanning range of the proposed antenna through the broadside is 70.19°(−42.49° to 27.7) with an impedance bandwidth of 15 GHz (50-65 GHz), an optimum gain in the fast wave area ranging from
$15.5 \,\mathrm {dBi}$
to
$19.79 \, \mathrm {dBi}$
and an efficiency of 83.8% at
$57.5 \,\mathrm {GHz}$
. Detailed RVSM tests have been performed with the proposed antenna system. It is shown that by adjusting the operating frequency from
$50 \,\mathrm {GHz}$
to
$65 \,\mathrm {GHz}$
, multiple targets’ breathing rates (BR) and heart rates (HR) can be detected within 70° of the angular range.