GB890310A - Improvements in and relating to wavemeters - Google Patents

Abstract

890,310. Frequency measurement; capacitors. COSSOR Ltd., A. C. Aug. 25, 1959 [Aug. 25, 1958], No. 27143/58. Class 37. [Also in Group XL (b)] A strip-line wavemeter comprises an elongated conductor mounted between and insulatedly spaced from two flat conducting inter-connected earth planes and a further conductor spaced from and extending laterally of the elongated conductor, with means for varying the capacitance between the further conductor and the earth planes so as to correspondingly vary the frequency of maximum energy absorption by the further conductor. Earthed metallic planes 10, 11 (Figs. 1, 2) have clamped spacedly between them a low loss insulating sheet 12 of e.g. laminated silicon glass cloth bonded with silicone resin to opposite sides of which are bonded registering copper foil strips 15 connected at their ends to the inner conductors of coaxial cables through connectors 16, 17. Two further registering conducting strips are bonded to opposite sides of the sheet at right angles to, spaced from, and electrically coupled to strips 15, and a T member 20 sliding on guides 19 is movable by micrometer screw 23 at right angles to strips 15 to variably interpose plates 24 of high dielectric constant, e.g. polystyrene loaded with a titanate, between strips 25 and planes 10, 11 on either side of sheet 12 to vary the capacitance coupling therebetween. Radio energy passes through the strip-line system 10, 11, 15 and an energy measuring instrument, e.g. a crystal detector followed by an ammeter is connected thereto while the micrometer is adjusted to vary the resonance frequency of the system 25, 10, 11 for minimum induction and maximum absorption of energy and may be calibrated in frequency or wavelength. The metallic strips may be printed on the sheet 12, and the conductors 25 or plates 24 may be of such shape or thickness as to produce any desired relation between displacement of the plates and variation of capacitance. In a modification (Fig. 3), the insulating sheet 12 may have a slot 26 into which slides a tuning extension 221 of the micrometer screw; the slot being enclosed by U-shaped strips 25<1> on each side of the sheet.