Abstract :
The requirements to be satisfied by a transfer element for the comparison of u.h.f. with d.c. power are stated under the headings of transfer properties and matching and residual losses, and the need for a new type of coaxial bolometer is discussed in the light of them. A coaxial film bolometer which satisfies these requirements for all frequencies between 200 Mc/s and 4 Gc/s is described, and the factors affecting its accuracy are discussed. The range of power that can be handled directly by the instrument is 2¿200 mW, the v.s.w.r. relative to 50 ohms is of the order of 0.98 and the uncertainty in measurement is within 1% for powers between 20 and 200 mW. The design is not confined to a particular size. A smaller bolometer element, which handles powers down to 0.1 mW with an upper frequency limit of about 20 Gc/s, and a larger bolometer element, which handles powers up to 2 watts with an upper frequency limit of 3 Gc/s, are feasible.
