Agilent 1950-05 free download

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HEWLETT-PACKARD JOURNAL T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S BUSHED CALIFORNIA THE HEWLETT-PACKARD COMPANY, 395 PAGE MILL ROAD, PALO ALTO, CALIFORNIA Direct Reading UHF Power Measurements A T HIGH frequencies as at low the power In use, the instrument operates as easily and -/^-flowing in a system is a frequently- quickly as a vacuum-tube voltmeter. sought factor. In fact, at high frequencies The high-frequency power to be measured power assumes extreme significance, for nei is absorbed in a bolometer element. Since ther voltage nor current as such can be read such elements customarily have an imped ily measured. ance of 200 ohms and are operated with 50- Figure 1 shows a direct-reading high-fre ohm transmission systems, an intermediate quency power meter that measures the out device is required to transform the bolo put power from signal generators, oscillators, meter impedance down to the line imped and similar equipment. In effect, this power ance so that maximum power transfer can meter is an automatic version of the common occur. Such a device is the tunable bolometer bolometer substitution bridge; but, because mount shown in Figure 2. its operation is automatic, measurements can The frequency at which high-frequency be made quickly