GB597262A - Improvements in or relating to ultra-high-frequency electrical apparatus - Google Patents

Abstract

597,262. Testing radio apparatus ; wave-guides. ALLEN, W. D., and JOHN. STON, J. E. M. Aug. 23, 1945, No. 21662. [Class 40 (v)] [Also in Group XXXVI] An arrangement for effecting a test or measurement on ultra-high-frequency electromagnetic wave apparatus by observation of the standing wave conditions set up in a length of wave-guide connecting the apparatus with a source of oscillations, comprises an energy pick-up device continuously movable from end to end of a selected portion of the wave-guide and means for rectifying the energy picked up and supplying the resultant D.C. output to the terminals of a cathode-ray oscillograph. In the form shown, an ultra-high-frequency oscillator 10 is connected by a rectangular waveguide 12 to the apparatus under test at 14. Projecting through a slot in the inner curve of a semicircular portion of the wave-guide 12 is a probe 15 carried by a rotatable drum 16 adapted to be driven by motor 20 and shaft 21. Energy collected by probe 15 is rectified at 17 and the resultant voltage after amplification at 28 is fed to one pair of deflecting plates x1, x2 of a cathode-ray oscillograph 29. The other pair of deflecting plates yl, y2 is supplied with a sinusoidalvoltage generated in a cored coil 25 by the rotation of an eccentric iron disc 23 on shaft 21. This will give a graphical representation on tube 29 of the standing wave conditions in the semicircular part of guide 12. Instead of a sinusoidal time base, a linear time base may be used. This may be generated or synchronized by a stepped cam 31 on shaft 21. The guide 12 may be provided with an attenuator in the form of a blade 33 of lossy material which may be variably inserted in a slot in the guide wall. There may also be provided a wavemeter 35 in the form of a calibrated tunable stub. Fig. 2 shows a constructional form of the semicircular part of wave-guide 12 and associated parts. Two semicircular members 12a, 12b are each provided with channels which, when secured together, form the curved part of wave-guide 12 leaving a slot 12c along the inner curved wall. Drum 16 is mounted on shaft 21a so as to rotate in close proximity to the inner curved wall of guide 12, and is formed with a flange 16b which substantially closes slot 12c. Leakage is further prevented by suitably dimensioned channels 16c. Probe 15 is adjustably positioned in a bore in drum 16 so as to constitute a coaxial line for feeding energy through an axially disposed guide 36 to a rectifier unit 42 which supplies an output to a contact blade 48 for feeding to the cathoderay oscillograph. Instead of a rotating probe, a reciprocating probe could be used. Alternatively, the probe may be kept stationary while the standing waves are made continuously to pass the probe by means of a suitable phaseshifter such as that described in Specification 597,258.