US2449975A - Microwave vacuum tube - Google Patents

Description

p 8, 1948. H. o. BISHOP ET AL 2 ,449,975

MICROWAVE VACUUM TUBE Filed Jun e' 21, 1946 a I 25 r T /22 FIG.3 I 8* INVENTOR.

HAROLD O. BISHOP DONALD KIRK JR.

Attorney Patented Sept. 28, 1948 f 'U-NITED STATE ail 49,975

MICROWAVE vAoUuM TUBE Harold 0. Bishop and Donald Kirk, Jn,

United States Navy Application June 21, 1946, Serial No. 678,177 7 Claims. (01.,250-9158) (Granted under the act of March '3, 1883, as

amended April 30, 1928; 3'70 O. G. 757) I This'invention relates to radio vacuum tubes and more specifically is concerned with cathode ray tubes utilized for the generation, amplification, and/or frequency conversion 01' microwaves.

In the electronic art associated with the utilization of microwaves, frequencies above 1000 megacycles are generated, mixed and amplified. Becausethe period of such oscillations is one billio'nth jioooooom) of a seccnd'or less, electron transit tim'e' becomes critically important. electronic devices utilized in this frequency region must either limit electron paths to a small fraction of the distance they would travel in one halfcycle, or utilize electron beams in such a way as to avoid dependence on transit time. In these latter devices. the transit time does not have, to be kept to a small fraction of one half-cycle of the operating frequency, which means that their useiul frequency range goes to very much higher frequencies.

An object 01' this invention is to provide a vac-' uum tube which can function as an amplifier,

detectonmixer, or oscillator at frequencies above 1000 megacycles, without limitation due to elec- All electron beam in the same direction, as it passes through the tube.

tron-transit time therein; and wherein high deflection sensitivity is achieved through the use use or a novel deflection means, resulting in markedly higher tube transconductance for these various tube functions.

In the drawings:

Figure 1 is a schematic view of a typical embodiment of the invention, utilized as an ampliher or. as an oscillator. c

Figure 2 is a schematic view of a typical embodiment oi the invention, utilized as a frequency 1 mixer or converter, such as would be useful in a superheterodyne receiver circuit.

Fig. 3 illustrates a. simplified form of part the apparatus shown in Fig. 2.

--Flgure 1 shows an arrangement of electrodes within a cathode ray tube. Electron gun I provides a beam of electrons H which passes through'the tube to strike collector plates Hi. It and II. Deflector plates 2-4, 3-4, l-4', 5-4. 6-6, etc., are arranged along the path of said electron beam ll so as to deflect the beam in a cumulative manner. The voltages developed on said deflector plates are phased by a system of quarter-wave stubs 9 and excited through input loop I and connecting line 8. As this arrangement of deflector plates and tuning stubs so as to constantly deflect a given portion of the The beam thus deflected from its neutral path can travel from the end of the deflector plate arrangement to the collector plate arrangement I 0, l0 and II through a separation distance that is not critical to the tubes operation. The transit time can be comparatively long without affecting tube operation. When this beam reaches the collector plates the alternate flow to electrode It! then to electrode l0" causes a current to flow in the shorted quarter-wave line at its resonant frequency. Output loop l3 and its associated coaxial line are shown as a typical method for coupling to the tube to obtain a useful output.

Considering the overall operation of the tube shown in Figure l, a comparatively weak signal of the proper frequency can be introduced as an input to loop 8. 'The multiplicity of deflector plates is excited by this input voltage and causes a deflection of the electron beam markedly greater than that which would be caused by a conventional pair of deflector plates. This beam then strikes the collector plates and excites the output circuit [2 so that an amplified signal may be taken off'at'loop IS. The input 8 may connect to the output I 3 through a circuit providing the phase relations necessary for oscillation of the tube and associated circuit.

Figure 2 shows another application of the vacuum tube of this invention in which two sets of deflector plates l5-l5' and l6l6' are arranged so as to deflect the electron beam in a single plane. When fo-and f; are in phase, additive, the beam is widely deflected and spends most of its cycle striking plates 20 and 20, thus flowing to 3+ through connector 22. When f0 and f5 are out of phase, bucking, the beam is deflected very little and strikes plate 2| most of the time, thus flowing to 3+ through connector 23. This change of electron flow from connector 22 to connector 23 and back to connector 22, for every phase change of 360 between incoming signals fs and fo, occurs at the difference frequency. .fsf0. If circuit 25 is tuned to this difierence frequency, a useful output can be obtained.

The tube can be used as a converter instead of a mixer by connecting tuned circuit 26 to leads 20 and 20', and coupling the loop 21 to said tuned circuit 26. The output Of loop 2'! is then adjusted in phase and applied to deflector plates I 6-4 6 so that the in component in the tube output regenerates the excitation applied to de-

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