US1762969A - High-frequency attenuating network - Google Patents

Description

June 10, 1930. .1. F.- FARRINGTON I ,959

men FREQUENCY A'i'ffifiunluq nsrwogx' med. April 10, 1925 i UNITED s'rATss PATENT orrlcs I I". rm'nre'ror, OI I'LUBKII'G, rmw YORK, ABSIGNOB, BY ASSIGMTS, 1'0 METRIC comm, IIjOOmBATED, A OOBPOBATIOI 01' m YORK HIGH-FREQUENCY ATTEI I'UATIKG NETWORK Application fled April 10,

This invention relates to non-reactive atv tenuation networks adapted to be used for current attenuation for measurements and other urposes at radio frequencies. 6* In fi ld strength measuring sets and other radio signaling systems," it frequently is desirable to impress local oscillations u n a certain portion of a receiver circuit. attercagplting to govern the amplitude of these 10 l' y applied t has been the practicetouseapotentiometerconnectedbetween the source of oscillations and the point tow 'chtheomillationsaretobeapplied 1:1 van fl'ltzithissydzemisthagasthe l5 m nu .x is therksim a1ance which the' we is tered, p ucmg a vanatlon m thefrequencyoftheoscillatlonswu Inordertoovemnnethis Inanetzoworkhasbeendevised whichcompnses a plurality of attenuation units which may inserted at will to produce difierent ratios of input current to output current without altering the input impedance of the net: work. Ineonstructingunitsofboth and lowattenuation values foruse at frequen cies adapted to work into the same termmat-I ing cc to produce anattenuation net at work having a constant in ut impedanoe as llldllmfill'ew 1 '1: i t

'50 A further feature of the an vunit's, hereinafter .aretothehigh 1925. Serial m. 88,088.

attenuation box for use in high frequency apparatus in which units having different attenuation values are adapted to work into different terminat' impedances.

These objects and features of the invention and others which will be apparent as the nature of the invention is disclosed are attained by emplo an attenuation network composed of a urality of units, each unit comrising a -resistance"network ha neg- Egible inductance and capacity. rtam network units hereinafter the high attenuation units, such for exampltfa as those correspon to attenuations o ter than 10 decibels are #:1- u to work izto a given ce, while other ted as low attenuation units for exam le those co --2 l in to attenuations of le s than 10 are adapted to operate with a difier'ent terminating impedance. The low attenuation units A attenuation units by means of an L network which, taken in connection with.tbe impedance of the low attenuation presents the proper termination for the attenuation units. 7 The shunt impedance of the low attenuatingunitsisofsuchlargevaluethattheca- 'ty effect becomes troublesome at high muencies thst;l units are made 0; 111: impedance an unt impedance 0 1: high attenuation units is of such small value that it is incapable of being constructed noninductivel when the leads areconsidere unless the units are made of impedance, hence it desirable to construct the various units to o to be- I tween difl'erent ces.

Altho h the novel features which are believed to characteristic of this invention will be pointed out with 'cularity in the claims appended hereto, t e invention itself, its objects and advantages, the mode of its operation and the manner of its organizatlon will be better understood by referring to the following description taken in connection withthe'accompan drawing forming a partihe'reof in which ig.-1 is a diagrammatic'representationof a this invention, and'Flg, ,1! 0;

view partly in section of one form of attennetwork comprising sections A and B. En-

ergy passed through this attenuation network, is impressed upon a translating circuit herein shown as a tuned loop aerial or anftenna circuit including inductances 5 and tunin capacity 7, across theresistance 6 inserte between the 'inductances. Receiver B may be anysuitable form of apparatus to be actuated by energy vfrom the oscillation generator and may include a detector, such as a rectifier, and suitable indicating means 19.

Section A of the attenuation network comprises units of difierentattenuation values which for purposes of illustration may be considered as capable of. producing current ratios equivalent to 10, 20, and decibels,

each such network unit being composed of a T-resistance network 8 so designed that, when the proper terminating impedance is employed, the impedance looking into the section remains constant irrespective of the number of units connected in the circuit. Section B is composed of units of lower attenuation value such for example, as that of 1, 2, 3 and 4' decibels similarly constructed of T -resistance networks 9, but adapted to work into a terminating impedance difierent from that with which section A is designed to operate. 1

Section B is connected to section A through a transition network composedof series resistance 10 and shunt resistance 11 having such values that the sum of the impedance of resistance 10, and impedance of resistance 11 taken in connection with section B in parallel thereto, is equal to the required terminating impedance for section A whereas resistance Y 11 taken in connection with section A in par allel thereto,'presents substant y the pro er terminating impedance for section Section B is terminated at its other end in an impedance consisting substantially .wholly of resistance'12 .in series with resistance6 which is connected in the loop circuit. Re-

sistances 12 and 6 combined present the proper terminating impedance for section B.

In Fig. 2 is shown a method ofconstructing the various units 8 or '9 so that they may be plugged into the circuit at will and when removed the capacity ofthe units will benegligible. Resistance units 8, which should be wound so as to have a minimum of inductance and capacity, are mounted on an insulating plug 20 sup orted by and adapted to slide in panel 21. he inductance is reduced by makm the wires short and winding-them nonin actively in accordance with known meth-- ods and the capacities are reduced by making the resistances and the leads of as small'area as possible. Contacts 13, 1t and 15 make connection between the three resistance units and the line 16, 17 when the plug is in the position shown. With the plug ushed down resistances 8 are disconnected m the line 16, 17 at contacts 13, 14 and 15 and line 16 is completed by conductin bar 18 which then connects contacts 13 an ance units are entirely disconnected in the latter position their capacity to the line and to ground will be negligible.

An attenuating networkv of the type described which has proven satisfactory at high frequencies has been constructed with the units of section A designed to o te be tween impedances of 200 ohms an the units of section B designed to operate between imof 20 ohms. In thiscase resistance 10 was approximately 190 ohms and resistance 11 was 20 ohms. 'Remstance 12 was taken at 19 ohms, leaving one ohm for the .2 resistance 6 in the loop circuit.

When a potentiometer is used in place of the attenuation network herein described it 14. As the resist-' is extremely diflicult to the frequenc of the oscillations constant due to the impe ance being altered each time the attenuation is varied. In the operation of this circuit the uired number of units may be selected to give the desired (1 of attenua tion without efi'ecting the impedance into which the oscillator works.

Altho h'this invention has been shown and described by way of illustration only as applied to a specific system in a particular manner, it is not to be limitedthreto but only in accordance with the scope of the invention as defined by the following claims.

What is claimed is:

1. In a system including. a of oscillations and a load circuit, means for varying the attenuation of said oscillations comprising an attenuation network composed of a plurality of attenuation units each having a fixed attenuation characteristic which is difierent from that of the others, comprising groups each having a constant characteristic impendace regardles ofthe number of units and adapted to operate betweeni'difierent terminatm impedances and means for inserting eac unit in the network at will while maintaining a continui of circuit between the remaining units, sai network being connected between said source of oscillations and said load. I

i 2. In a radio receiving circuit including a loop aerial and a'source of f oscillations, a resistance includ in sai loop, a tuned circuit adapted to establish the frequency of said oscillations, an attenuation box connecting said tuned circuit and said resistance, said attenuation box being com d of i a plurality of T-resista nce units of 'fierent uency I attenuation values, certain of said units, com-' substantially constant irrespective of the number of units connected in the circuit.

3. A resistance unit for inserting a T- resistance network in a line comprising a plurality ofresistances, an insulating contact supporting means, contacts carried thereby whereby said resistances are connected to said line in' one position and whereby said resistances are disconnected from the line in another position, and other contacts also carried' by said supporting means for closing said'line when the unit is in the last mentioned position.

4. A system comprising a source of local oscillations, a load circuit, an attenuation network interconnecting said source and said load, comprisinga plurality ofunits of different attenuation values comprising a plurality of groups, the attenuation values for the units in each group occupying a range different from that of the other groups and each suchgroup being adapted to operate with a different terminating impedance than the other group, and a transition network for connecting each. pair'of adjacent groups of units. r

5. In a system, a space discharge oscillator, a' frequency establishing circuit, and a receiving circuit in combination with an attenuation box connected between said frequency establishing circuit and said receiving circuit, said attenuation box being composed of a plurality of T-resistance units having different attenuation values and comprising a plurality of groups adapted'to operate with different terminating impedances, and a transition resistance network for connecting each pair of adjacent groups of different terminating impedance in such manner that the impedance of the attenuation box as a whole remains constant while the number of units is varied.

6. In a system of the character described, an attenuation network comprising a series of units of difierent attenuation values, said units comprising a plurality of groups, the

of units of ditferent attenuation attenuation values for the units in each group occupying a range different from that of each of the other groups and each such group being adapted to operate into a different terminating impedance from that of the other groups, each pair of adjacent groups being connected by a transition network compris ing a series and a shunt resistance.

7. In a system of the character described, an attenuation network comprisi-n a series use said .units comprising a plurality of groups, the

attenuation values for the units in each group occupying a range different from that of the other groups and each such group being adapted to operate into a difierent terminating impedance from that of the other groups, each pair of adjacent groups being connected by a transition network comprising a series and a shunt resistance of such value that said series resistance and shunt resistance combined and taken with the subsequent series of groups, present the proper terminating impedance for one of each of said connected groups constituting .a pair, and said shunt resistance taken with the subsequent series of groups looking in the opposite direction presents the proper terminating impedance for'the other of each of said connected groups constituting a pair.

8. In a system of the character described, i

an attenuation network comprising a series of units each composed of a T-resistance network, said units having various attenuation values, said units comprising a plurality of groups adapted to operate into difierent terminating impedances, each pair ofadjacent groups being connected by a transition network comprising a series and a shunt resistance of such values that their combined resistance, taken with the subsequent series of groups, presents the proper terminating impedance for one of each of said connected groups constituting a pair and the shunt regroups looking in the opposite direction,

' sistance, taken with the subsequent series of of the other of each of said connected groups constituting a pair.

9. A system comprising a source of local oscillations, an attenuation network connected thereto and a work circuit to which energy is transferred from said source through said attenuation network, said attenuation network comprising-a series of units each composed of a T-resistance network, said units having various attenuation values, said units comprising a plurality of groups adapted to operate into different terminating impedances, each pair of adjacent groups being connected by atransition network COIIlPl'lS- ing series and shunt resistances of such value that their combined resistance, taken with the subsequent series of groups, presents the proper terminating impedance for one of each of said connected groups a pair, and the shunt resistance, taken with the sub uent series of groups looking in the opposite direction, presents the proper tier minating impedance of the other of each of said connected 'roups constituting a pair.

In witness w. iereof, I hereunto my name this 3 da of April, A, D. 1925.

JO F. 'FABRINGTON.

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