| 摘要 |
<p>MICROWAVE THERMOGRAPHIC APPARATUS Microwave thermography apparatus comprises a signalreceiving aerial which is sensitive to microwave radiation emanating from a body having a mean body temperature. A reference load capable of being maintained at a chosen temperature (TO) and of emitting a thermal noise signal at microwave frequency corresponding to temperature TO, is connected to a receiver the input impedance of which is matched to the impedance of reference load by way of a 3-port non-reciprocal circulator . Aerial is connected via a singlethrow on/off microwave switch to the input of receiver through the other port of circulator. The connections to circulator , taken in circulation order, are reference load , aerial , receiver. Aerial is preferentially designed to incorporate a tubular metallic waveguide of circular cross-section dimensioned to support TE11 wave mode and the lower order mode, the signal output from the aerial being taken by a coaxial line and the aerial incorporating a broad band waveguide coaxial line mode transformer which is arranged to select only the TE11 mode for delivery to the coaxial line. The waveguide. is filled with a low-loss dielectric material in order to provide the aerial with an impedance close to the mean body tissue impedance (about 80 ohms).</p> |
