GB760133A - Improvements in or relating to travelling wave tubes - Google Patents

Abstract

760,133. Travelling-wave tubes. WESTERN ELECTRIC CO., Inc. Dec. 29, 1953 [Dec. 30, 1952], No. 36053/53. Class 39(1). [Also in Group XL(b)] A travelling-wave tube comprises a waveguide loaded by transverse slot resonators which extend right through the guide wall, the guide preferably being of rectangular section and having a rectangular sectioned ridge. In one form, Fig. 1, a rectangular waveguide has one wall slotted, the slots 14 forming resonators. The, guide supports a transverse E mode whose electric field is perpendicular to wall 12 and comprises ridge 13, which may be hollow or solid and a separate member or integral with the guide, to broaden the frequency band. The ridge and guide are of copper, or of gold plated molybdenum or tungsten. The spot length and ridge height are tapered at the ends for impedance matching and the beam passes between the walls of slit 15. Input and output guides are connected to curved ends 19, 20. Magnetic focussing is provided by pole pieces 77, 78, Fig. 7, integral with the envelope, and the tube envelope may be otherwise of glass or non- magnetic metal. The slots 14 may be formed by photoengraving metal sheets. The spatial harmonic wave may have a positive or a negative phase velocity, and the device may be an oscillator or amplifier. In another embodiment, Fig. 2, (not shown) <#>2 wires are secured to the guide by a frame, the ridge height, wire length and frame width tapering at each end for impedance matching. The frame is brazed or soldered to the guide. In a backward wave oscillator, Fig. 7, wire tape 52 is wrapped helically around waveguide 51, the parts of the tape extending across the open side of the guide being in length. The beam passes on both sides of the wire tape 52. The collector end of the guide is terminated by wedges 70 of resistance material between the ridge and side walls of the guide, and the ouput guide 71 is tapered for impedance matching. The device is tuned by varying the beam velocity. The guides need not be of rectangular cross section. The devices may work at millimetre wavelengths. The design is discussed mathematically, and a numerical example is given.