Engineering topics
Publications and source records attributed to Barr, T. A..
Summed signals and dielectric-filled antenna improve measurement. Improved FM radar for measuring thickness of coal seam eliminates spectrum splitting and reduces magnitude of echo from front coal surface.
Front-surface, local-oscillator radar directly compares frequency of signals reflected from front and back surfaces of coal deposits. Thickness is measured directly as frequency difference. Transmitter is frequency modulated, so thickness is computed directly from frequency difference. Because front and back reflections are detected in combination rather than separately, masking of comparatively weak back signal is less problem. Also system is not sensitive to extraneous reflections from targets between transmitting antenna and coal surface.
An FM radar for the measurement of coal thickness wherein an FM transmitter is modulated by the combination of two signals; One, for example, could be a frequency of 100 Hz, and the other a frequency of 15 Hz. A horn-type antenna is used which is filled with a material having a dielectric constant approximating that of coal.