US2401634A - Ultra high frequency coupling device - Google Patents

Description

June 4, 1946. s. GUBIN ULTRA HIGH FREQUENCY COUPLING DEVICE Filed April 18. 1942 inventor fizzb (Ittorueg Patented June I I UNITED s A'rss PATENT orrlcsk TRA men rgrzc ooUrLinG Samuel Gubin, Merchantvlllef, n.1, assignor to America, a corporation of 0 Radio Corporation of Delaware Application April 18, 1e42, Serial No. 439,459 I I l i This invention relates quency circuit to a coaidal transmission line :in

. such a manner that the power transfer through capacitive couplings which have complementary frequency characteristics have been used heretofore to obtain automatically the desired frequency response. Also various mechanical expedients have been employed. For example-an I inductive coupling may be varied as the frequency is varied, by mechanically connecting the coupling and frequency controlling elements. Such mechanical coupling usually involves expensive and complicated structure.

This invention is an improvement of my copending application Serial No. 372,565, filed December 31. 1940, in that this application pertains to a method and means for providing coupling between a suitable ultra high frequency tuned circuit and a coaxial cable. It is an object of the invention to provide simple, inexpensive and improved means for transferring ultra high frequency energy'at a substantially constant level over a wide range of frequencies. An additional object-is to provide means for efllciently coucults over a wide range of frequencies. Another object is to provide improved means for tuning a' parallel line and a section of coaxial cabie'to effect a constant energy transfer between them. Anadditional object is to provide means for efficiently coupling a balanced resonant ultra high frequency circuit to a single ended circuit of a wide range offrequencies. Another object is to provide means for tuning a resonant circuit and a section of coaxial cable so that'the energy transferred between them follows a predetermined frequency' characteristic.

The invention will be described by reference to the accompanying drawing which is a schematic circuit diagram of one embodiment thereof,

in which the frequency range is of the order of '60 to 200 megacrcles.

Referring to the drawing. theanode's i and I Claims. 178-44) generally to ultra nun frequency coupling devices and particularly to improved, means for coupling a tuned high fretubes are connected to the open I .onant circuitcomprising the parallel lines I and endsof the resl. The circuit is tuned by the shorting bar 5 and the tuning condenser 0 which is connected across the open ends of the lines 3 and I. In operation, the condenser 8 and the shorting bar lare adjusted to maintain a substantially constant current in the resonant circuit throughout 7 the desired range of frequencies. In order to pling two single ended ultra high frequency clrthus maintain the input impedance of the circuit at a uniform value it is desirable to link the actuating mechanisms for the shorting bar and the controlling mechanism of the condenser in a com-' plementary manner as indicated by the dash lines.

One end of a coaxial cable, comprising asheath II and an inner'conductor II, is connected to a suitable output circuit such as an antenna. The

other end of the coaxialcable is terminated in a special cable section comprising the outer shell I3 and an inner threaded conductor H which carries a nut II. which is prevented from. rotating by any suitable means. The ratio of thediameters of the conductor it and the shell ill should be the same as the ratio of the diameters of the conductor 12 and sheath Ii of the coaxial cable. in order to match the surge impedances. The threaded conductor is supported by a contact bearing l6 insulated from the shell ll by the insert 35 and connected to the conductor l2 and an insulating bearing [1 supported by the shell it. A shaft i8 and a control knob il'are suitably connected to the threaded conductor toprovide for rotation thereof. The shell it is ro.-

the sheath II. The loop II should preferably Q be of low impedance and should be coupled as closely as practicable to the resonant line 3, 4.

In operation the cable section is adiustedas follows. The coupling loop II is coup e a! close ly as desired to the resonant lines I and I. The I degree of coupling to the cable section is varied by turning the knob l0 and hence the threaded conductor It to move the nut I! along the con-f ductor until the voltage transfer is a desired value. as indicated. for examphQby the, vacuum tube voltmeter. The voltmeter may comprise a diode II, the anode of which is coupled to the .50

of a pair of push-pullhigh frequency amplifier 66 inner cable conductor it through the capacitor 82. The cathode of the diode is connected through a suitable resistor 30 and the meter is to the cable sheath ii. The cable section between A and B may, if desired. be short-circuited by providing It I! instead of a, v 3 the insulating bearing described heretofore. This is particularly desirable if the cable section between A and B approaches any multiple one-quarter wave resonance. The short circuiting, previously mentioned, may of coursebe ac-' complis'hed by a. suitable switch 25 instead of the contact bearing described. r

The reactance of the coupling loop 2| should be small compared to the surge impedance of the coaxial cable at the low frequency end of the frequency range to be covered and should be of the same order of magnitude at the high frequency end of therange. At higher frequencies the in- .duced voltage increases to compensate for the increased leakage reactance in the circuit.

It will be apparent that suitable means may be.

included for mechanically connecting the tuning elements of the resonant line and the coaxial cable section to provide for unitary control as indicated by the dash line 21.

I claim as my invention:

1. An ultra high frequency device including a tunable transmission line and a, coaxial cable comprising an inner conductor and anouter conductor 'surrounding said inner conductor, an adjustable shorting bar engaging said line, a tuning capacitor connected across the open end of said line, means for varying the coupling between said f line and said cable, and adjustable shunt means connecting said cable to said coupling means.

2, An ultra high frequency device including a 4. A device of the type described in claim 2 in which said adjustable cable'section includes a slotted cable sheath and the inner conductor'ot said section includes a lead screw, a-nut carried by said screw, 9. connection from said loop to said nut through said slot'and an adjustable connection from said loop to said sheath. 5. A device of the type described in claim 3 in which said adjustable cable section includes a slotted cable sheath and the inner conductor of said section includes a lead screw, a nut carried by said screw, a connection from said loop to said nut. through said slot and an adjustable connection from said loop to said sheath.

a 6. An ultra high frequency. device including a tunable transmission line and a coaxial cable tunable transmission'line and a coaxial cable comprising an inner conductor and an outer conductor surroundingsaid' inner conductor; an adjustable shorting bar engaging said line, a tunin capacitor connected across the open end of said line, means including a loop and an adjustable section of said cableshunt-connected to said loop for varying the coupling between said line and, said cable, means for adjusting said cable section to vary the coupling between said loop and said cable section, and means for coupling said loop to said line. Y

3. An ultra high frequency device including a tunable transmission line and a coaxial cable comprising an inner conductor and an outer con; ductorsurrounding said inner conductor, an adjustable shorting bar engaging said line, a tuning capacitor connected across the open end of said line, means including a loop and an adjustable section of said cable shunt-connected to said loop for varying the coupling between said line and- I said cable, means for adjusting said cable section to vary the coupling between said loop and said cable section,'and adjustable means for coupling said loop to said line.

comprising an inner conductor and an outer conductor surrounding said inner conductor, an-adjustable shorting bar' engaging said line, a tuning capacitor connected across the open end of said' line, means including a single turn loop and an adjustable section of said cable shunt-connected to said loop for varying the coupling between said line and said cable, means for adjusting said cable section to vary the coupling between said' loop and said cable section, and means for 7 coupling said loop to said line.

7. An ultra high frequency device including a tunable transmission line and a coaxial cable comprising an inner conductor and an outer conductqr surrounding said inner conductor, an adjustable shorting bar engaging said line, a tuning" capacitor connected across the open end of said line, means including a single turn loop and an adjustable section of said cable shunt-connected to said loop for varying the coupling between said line and said cable, means for adjusting said cable section to vary the coupling between said loop and said cable section, and adjustable means for coupling said loop to said line.

8. A device of the type described in claim 2 in which said cable is connected to said adjustable cable section at a point well removed from the open end of said line.

9. A device of the type described "in claim 2 in which the impedance of said loop is small with respect to the surge impedance of said cable section.

10. A device of the type described in claim 2 in-. cluding common means for adjusting simul-- taneously said shorting bar, said tuning capacitor and said adjustable cable section.

. SAMUEL omens.

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