Microwave leakage indication
Kashyap SC, Wong JY, Dunn JG · 1976
The paper describes two systems for automatic indication of maximum microwave leakage along a radiating slot, tested on a microwave oven and waveguide slot with focus on leakage beyond 1 mW/cm².
Plain English Summary
The first system uses a liquid crystal film backed by microwave absorbing material that changes color from black to blue when exposed to microwaves. The color change occurs at a power density determined by the film's operating temperature and the absorbing material's properties. Normal room temperature changes have negligible effect on the strip, and hot vapor effects can be minimized with thermal insulation backing. The second system uses RF detector diodes distributed on a transmission line connected to a voltmeter, indicating the maximum RF field along the slot. With diodes spaced at 2λ intervals on a 1.0-inch wide, 12-inch long slot line, the device indicates when leakage exceeds a permissible level.
Why This Matters
Existing microwave power density meters only measure leakage at a single point and require moving the probe around the oven door to find the maximum. The two systems described overcome this limitation by automatically indicating when leakage anywhere along a radiating slot exceeds a preset level. The liquid crystal strip was tested on a recent microwave oven model and a waveguide slot, with focus on the Canadian permissible level of 1 mW/cm². The diode system used a slot line configuration, with diodes spaced at 2λ intervals, and the position and level of maximum power density were varied during testing.
Finding
Results of the leakage tests as well as the effect of the surrounding temperature on the performance of the strip is discussed. It is shown that normal changes in room temperature have negligible effect and that the effect of hot vapours from the food being cooked can be minimized by a thin backing of thermal insulation on the strip.
In their words
“Results of the leakage tests as well as the effect of the surrounding temperature on the performance of the strip is discussed. It is shown that normal changes in room temperature have negligible effect and that the effect of hot vapours from the food being cooked can be minimized by a thin backing of thermal insulation on the strip.”
Show BibTeX
@article{microwave_leakage_indication_g6482,
author = {Kashyap SC and Wong JY and Dunn JG},
title = {Microwave leakage indication},
year = {1976},
}