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MINiATUhi/ED HlGH-EFFiCl£NCY |i*^»Ma1to=ta(iftw^^^«^

R F FILTERS

Contrqci No AF 33 (COO)"2288!

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I

INTERIM ENGINEERING HEPORT NO. 6

MIN[ATURJLZED HIGH -ft FFtC lEMC Y

H-F FILTERS

*'o»' the Period 29 March 1.954 u« 2*» June 1A54

BALC'O iu:s!•;A!«.' H I.AHOI!ATOH!KS

4S)-:'i:J i'.diaon I'IUH:

N<",vai'i. 2. New Jeruuy

Contract No. AF 33(60O)-22»ai K, O. No- R-U2-19 SK-66^; 27 August 1064

I

buieo Research Laboratories Interim Hewort No. 8

AF 33(600}-22861 R-F Filters

NOTICES

When Government drawings, specifications, or other data are used

for any purpose other than in connection with a definitely related Govern-

ment procurement operation, the United States Government thereby incurs

no responsibility nor any obligation whatsoever; and the fact that the

Government m&y have formulated, furnished, or in any way supplied the

said drawings, specifications* or other data, i« not to b« regarded by Im-

plication or otherwise as in any manner licensing the holder or any other

person or uorporation, or conveying any righta or permission to manu-

facture, ufciO, or sell any patented invention thai may in any way be re-

lated thereto.

The information furnished herewith iu made available for study

upon the understanding that the Government's proprie:.ary Interests in and

relating thereto shall not be impaired, It is desired that the Office of the

Judge Advocate, Wright Air "Development Center, Wright-Patterson Air

Force BaBe, Ohio, be promptly notified of any apparent conflict between

the Government's proprietary intercuts and those of others.

The U. S. Government ia abaolved from any litigation which may

ensue from the Contractor's infringing on the foreign patent rights which

may be involved.

1!J

J - - . --. Ba4eo Research Laboratories AF p3(600)-223Gl

i inter mi Report No. G R-*' Alters

j FOREWORD

Thi ' i i the sixth interim report submitted under Contract No, AF •

33{GOO)-22BHl, Expenditure Order No. R-112-19 SB-662, Miniaturised • -

High-Efficiency R-F Filters

The program is being directed by Mr. C.R. Winston of Vvrright Aij

Development Center, Directorate of Laboratories, Components and

Systems Laboratory. The work covered by thin report was performed

under the direct supervision of Mr, Neqdttt Brgul. Project Engineer

at Balro Research Laboratories and Dr. Seymour Edolburg, Head of

the Electronics Division.

Balco Research Laboratories interita Report. No, 6

AF 3:j((>oo/-2^Ub: R-F Filter

: •

ABSTRACT

* This* report contains a discussion of investigations being conducted

on r~f Miters and their components, This period is primarily a con-

struction period accompanied by experimentation with some theoretical

investigations of certain phases of the work. The results of the investi-

gations are also presented.

We are investigating which type of filter design is to be used in

constructing the low-pass filter with a cutoff frequency of 30 mc, The

beat type of filter design for the low-pas* 1500 nn- filter is also being

investigated with emphasis on both electrical performance and physical

compactness.

Low-pass filters with cutoff frequencies at 190 mc, 275 me and

400 mc are under construction. Construction of the final miniaturized

model of the high.-pass 2600-me filter has been completed.

With rospert to the variable-f„ filters, a new approach to the

shielding problems has been found which appears to have interesting

posaibilit ie.--. Ways of varying the impedances are now being investigated.

Balco Research Laboratories interim Heourt No 6

AF 3^<600)-2z89i U-F Filters

3 PURPOSE

The purpose of this program in the development of a series of min-

iaturized, high-efficiency* r-f filters to be used in ronjunction with the

antennae of various receivers and transmitters for suppression of spuri-

ous radiations and harmonics. In particular, the following units are to

be designed and constructed.

TYPE OF FILTER

High Pa a a Low Pass

High Pasa Low Paws

High Pass Low Paee

High Pass

High Pass Low Pa8a

High S'&SB

High Paws Low Paaa

CUTOFF FREQUENCY (mc)

1.8 30

200 400

210 27 5

2800

145 Uh.)

400

340 1500

Performanr<j goals for (host.- units arc aa follows*- a maximum in-

sertion loss of 2 db i" thr- pass hand- a minimum attenuation of 50 db in

the yiop band, and pbyHieal Hivse to be (mid to a minimum. Detail requirementa

Bale a {tesesrefl Laboratories AF 33(800)-228Gl interim Report No. 6 H-F Filters

•rtchiding power rating aad impedance are sa\ forth in Exhibit WOES 52-49

dated 37 May 1952.

During the sixth quarterly period, development work was continued

according to the general procedures outlined in the Fifth Interim Report.

In particular, the work included: (1) construction of experimental models

of filters with cutoff frequencies of 1.8 me and 30 mc; (2) construction of

low-pass filters with cutoff frequencies from 100 mc to 400 mc; (3) final

testing of the high-pass 2800-mc filter; (4) design und experimentation for

the low-pass, 1500-me filter, (5> continued theoretical and experimental

investigation of variable fc filters,

HIGH-PASS 1.8-MC FILTER

The miniature high-temperature capacitors under order have been

delivered and an experimental model using thews components and specially

constructed miniature inductor*? wound on powdered iron loroids, has

been built. The attenuation characteristics of this unit are shown in

figure i,

This experimental model will now be miniaturized and the minia-

turised unit constructed inside a tube with an oui^ide diameter of I 1/4

inches and an overall length oi' less than seven Inches. Tin., performance

of the miniaturized unit at high temperature is expeote *>e very close

•2-

Balco Re.sc.Avch Laboratories Interim Reuort Kfai 8

AF 3•^600^-22861

•

j

to its p or for man ee art roofn temperature Results of high-temperature

performance test? now being made will he reported in our next monthly

letter.

LOW-PASS 30-MC FILTER

Transmission line filters with cutoff frequencies in the 30-me re-

gion, although efficient, became rather large and bulky in overall physi-

cal dimensions. For this reason a. design using lumped parameters would

be preferable If satisfactory filter performance can be maintained. An

experimental model using lumped parameters had been previously been

constructed, as reported. Us performance was found to be satisfactory,

;>nd the unit was considered to merit miniaturization. We have therefore

begun constructional details for a miniaturized final model, which will

fhen be tented under high and low temperature conditions

LOW-PASS FJLTEHS WITH Fc FROM 190 MO TO 400 MC

k iw-pnaa filters with cutoff frequencies at 190 mc, 276 mc and

400 mc: ar-<* under construction. During the pan* period, some weak points

in the mechanical design have been corrected, special consideration being

given to compactness and ruggedness of the units.

•3-

f Bai-:o Research Laboratories Interim TJeport No. g

AF 33(800)-2286i -

', •

One eeriotes m.#eh*wk:a* design consideration has been to incorpo-

rate bit© the emits preventive -And compensative measures to overcome

fhe relative differences of *xpwwton of its various par to at high tempera-

tures. The units have been so designed that their operation is not much

affected at 200°C. it is estimated that the. cutoff frequency will shift only

a few percent at that temperature. The performance of this filter at high

temperature is now being investigated,

HIGH-PASS 2S00-MC FILTEH

Construction of the final miniaturi/cd model has been completed.

The unit in now being tested at both high and low temperatures.

LOW - PASS 1 500 - MC FILT E H

Filters with cutoff frequencies below 500 mc and those with cutoff

frequencies above 2000 mc show fundamental differences of design. Since

ihe 1900-mc cutoff filters fall between thet»e two catagoriee;, we are in-

vestigating the advantages of both types of design before making our

choice.

We have constructed a unit using transmission lines and lumped

parameters, which will be tested at 200°C, A design incorporating trans-

mission line sections with discontinuities is also being investigated. The

. i

•4-

Balco Ftesearch ! .aborstcriea A If 33(0OQ)-2286 j Interim Report No, 6 H-F Filters

final decision on design will depend on results obtained from our Investi-

gations. Both optimum performance and physical compactness will be

'•onsidered.

V A RIA B LE - F FILTE KS

vious reports, difficulties have been encountered due to the radiation of

the transmission linos. During the pagt month, this hae been eliminated

by using a different approach to the shielding problem. Except for a 5-db

hump (no wider than 8% of the total past* bund) before cutoff, the new

attenuation characteristics curve adhered very closely to that predicted

by theory. The insertion loss was low, for the most part undsr 1 db;

che attenuation of the stop band was measured up to three times the cut-*

off frequency and was found to be over 80 dbg. Furthermore, the rise

from cutoff to 60-db attenuation w;is within 10 percent.

Later experimentation revealed that, the hump in the curve near

cutoff was caused by incorrect, series arm impedancea and could be

eliminated by careful adjustment.

Most of our efforts have been concentrated on improving the

transmission-line series arms of the filter. As mentioned in our pre- •

Interim Heport No. 8 R~v Filters •

Since ihi:. new approach showed such great possibilities, a prac-

tical way of varying the impedances will bo studied and an attempt mode

to construct a working model,

CONCLUSIONS • - -

There are several distinct type;? of filter design which together

cover the frequency range of the exhibit. These types of design have

been investigated and experimental models have been built,

The remainder of the program calls for the construction of final

model* of some of these types as samples for the exhibit. All units are

being carefully constructed and ruggedi/.ed to meet the environmental

conditions'* The building phase wllJ be accompanied by necessary

experimentation.

PHOGHAM FOR THE NEXT INTERVAL

1. Representative models of high-pass and low-pnss filters will

be built and tested at 200 degrees Centigrade. One model will be of the

ait lumped-parameter type, one of the distributed parameter type and

one of the combined lumped and distributive types. Results of the teats

will be reported in our monthly reports.

•

• 6- •

Balco Reestfftych Labc atorica AF 33(P0")-228G; Interim Report No. H R-F Filters

2. Work will be continued on miniaturizing into final form the

high -pas ,5 filters up to 400 roc.

3 With respect to the variable-f filters, further theoretical and

experimental work will be done an the shielded aeries arm configuration.

Approved by

.

Seymour Edelburg, Head, Electrodes Div.

Prepared by: ^jL&s*dJjM£ N'eoriel tergal, /px\j£<:t Engineer

-7-

inttfim *<wiit3T! 'tti u

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I . y u i u

Atteouofion Characteristics of Unmrniafurized Hiigh-Pass Futyr

CuU'lf Frequency;'H-TV:

i(fi£5(u^^lJ11J^^^^^^A^C:VK£?a^^j>*.v^*'A»a«*rr.»r./*

Because of our limited supply, you are requested to return this copy WHEN IT KAS SERVED YOUR PURPOSE so that rt may be made available to other requesters. Your cooperation

vrrw*w5*Mw.*MB«rA

NOTICE: WHEN GOVERNMENT OR OTHER DRAWINGS, SPECIFICATIONS OR OTHER DATA ATfEnTslD FOR ANY PtJRPOSE OTHER THAN ZH CONNECTION WITH A DEFINITELY RELATED GOVERNMENT PROCUREMENT OPERATION. THE U. 8. GOVERNMENT THEtifeB/ INCURS NO RESPONSIBILITY, NOR ANY OBLIGATION WHATSOEVER; AM,? THE FACT THAT THE GOVERNMENT MAY HAVE FORMULATED, FURNISHED, OR JO* ANY WAY SUPPLIED THE SAID DRAWINGS, SPECIFICATIONS, OR OTHER DATA IS NOT TO BE REGARDED BY IMPLICATION OR OTHERWISE AS IN ANY MANNER LICENSING THE HOLDER OR ANY OTHER PERSON OR CORPORATION, OR CONVEYING ANY RIGHTS OR PERMISSION TO MANUFACTURE, USE OR SELL ANY PATENTED INVENTION THAT MAY IN «W WAY BE RELATED THERETO.

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