METHOD FOR THE CONTROL OF THE IMPEDANCE MATCH IN LOW-NOISE RECEIVER CIRCUITS, AND MINIATURE MICROWAVE THERMOMETER UTILIZING THIS METHOD

摘要

The invention relates to an impedance adaptation control process in low noise reception chains and a miniature microwave thermometer of application of the said process. The process is used mainly in order to measure internal temperature by microwave thermography. The thermal radiation is picked up by means of an aerial (1) which provides a signal (2). This signal (2) is sent alternatively with a signal (5) coming from a standard source to a hyperfrequency amplifier (3) in order to compare the said signals (2,5) and to adjust the source (4) in consequence. According to the invention, in parallel, an additional impedance (15) is placed by intermittance in parallel to the input of the amplifier (3). By means of a synchronous detection (18) of the resulting signal (7), the impedance of the standard source (4) is adjusted so as to equal that of the aerial (1). The invention would, in particular, be applied for gauging the instruments for measuring the noise of dipoles and quadripoles such as microwave thermography.