Patent GB-1032601-A (GB)
Title: Improvements in or relating to microwave amplifiers and oscillators
IPC: H03F3/12
Filed: 1963-03-21
Abstract: 1,032,601. Negative resistance amplifiers and oscillators; parametric amplifiers. WESTERN ELECTRIC CO. Inc. March 21, 1963 [March 22, 1962 (2)], No. 11195/63. Headings H3B and H3T. [Also in Division H1]  A microwave amplifier comprises a waveguide having a slot in one wall, across which is mounted a negative resistance device such as a tunnel or PNPN diode; radiation from the slot is prevented by mounting over it external to the waveguide a second resonant waveguiding structure. The slot 12 (Fig. 1, not shown), may conveniently be formed in a plate 11 fitting into an aperture in the waveguide, the crystal diode 13 having one terminal attached to a wall of the slot and the other to a lead 14 passing through a bore in the plate 11, forming with lead 14 a decoupling capacitor for signal frequency. The lead 14 serves to apply operating bias to the crystal diode 13. The second resonant waveguiding structure may comprise a rectangular guide 21, Fig. 2, tuned by means of a movable piston 22. The arrangement, which may also be used as an oscillator, is primarily intended for use in increasing the power available and/or the degree of amplification. Thus a number of amplifier units may be evenly spaced around a circumference of a circular waveguide to increase the power handled (Fig. 4, not shown) or two or more circumferences spaced a quarter-wavelength apart so as to increase both power and gain (Fig. 9, not shown). In another embodiment a number of amplifier units are spaced at quarter-wave intervals along a rectangular waveguide, alternate units being placed on opposite sides of the waveguide (Fig. 6, not shown). In a further embodiment a number of diodes 34 (Fig. 3, not shown) are placed in slots 33 around the circumference of a concentrio waveguide 31, 32 and are enclosed in a further waveguide comprising a concentric cylinder 35 which is tuned by means of a movable annular conducting ring 38. In operation as an amplifier, the waveguide 53 (Fig. 5, not shown) containing the amplifying negativeresistance device is terminated in reflecting piston 55 and connected to one port of a threeport circulator 50, to the other ports of which are respectively connected the source 51 and load 52. In order that the coupling between the negative resistance device and waveguide may be varied, the slot 72, Fig. 7, in which the device 73 is located, may be formed in a slide 71 having tapered sides 78 and operating in a crossslot in the waveguide 70, the second waveguiding structure 74 being mounted on the slide 71. In an amplifier a number of such units may be located at quarter-wave intervals along a rectangular waveguide, alternate units being placed on opposite sides of the waveguide (Fig. 8, not shown). The arrangement may also be used as a paramagnetic amplifier. In this a variable-capacity diode 102, Fig. 10, is located in a slot in one wall of waveguide 100 in which the signal is transmitted and the second resonant waveguide structure comprises a tapering transition section 105 to which is connected a second smaller waveguide 106 by which the pump frequency is introduced.