US3657668A - Hybrid t-junction constructed in waveguide having a cut-off frequency above the operating frequency - Google Patents

Hybrid t-junction constructed in waveguide having a cut-off frequency above the operating frequency Download PDF

Info

Publication number
US3657668A
US3657668A US40074A US3657668DA US3657668A US 3657668 A US3657668 A US 3657668A US 40074 A US40074 A US 40074A US 3657668D A US3657668D A US 3657668DA US 3657668 A US3657668 A US 3657668A
Authority
US
United States
Prior art keywords
waveguide
junction
series
hybrid
arm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US40074A
Other languages
English (en)
Inventor
George Frederick Craven
Raymond Richard Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STC PLC
Original Assignee
International Standard Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Application granted granted Critical
Publication of US3657668A publication Critical patent/US3657668A/en
Assigned to STC PLC reassignment STC PLC ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P5/00—Coupling devices of the waveguide type
    • H01P5/12—Coupling devices having more than two ports
    • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
    • H01P5/19—Conjugate devices, i.e. devices having at least one port decoupled from one other port of the junction type
    • H01P5/20—Magic-T junctions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/18—Phase-shifters
    • H01P1/182—Waveguide phase-shifters

Definitions

  • ABSTRACT A hybrid T-junction constructed in waveguide for operation below its cut-off frequency.
  • the series arm of the hybrid provides a parallel resonant circuit in series with the symmetrical arms of the hybrid.
  • the shunt arm provides a series resonant circuit at the midpoint of the series arm.
  • the equivalent circuit is a lumped circuit bridged-T, which exhibits the properties of balance and isolation associated with bridge networks.
  • This invention relates to electrical waveguide arrangements, and particularly to an evanescent mode waveguide hybrid T- junction.
  • a waveguide hybrid T-junction constructed in waveguide having a cut-off frequency above the operating frequency, comprising a rectangular main waveguide forming first and second symmetrical arms of the junction dimensioned to have a cut-off frequency above the operating frequency, a first branch rectangular waveguide, dimensioned to have a cut-off frequency above the operating frequency, directly coupled into a first wall of said main waveguide forming a series arm to provide a parallel resonant circuit at the operating frequency and a second branch retangular waveguide dimensioned to have a cut-off frequency above the operating frequency, directly coupled to a second wall of said main waveguide forming a shunt arm to provide a series resonant circuit at the operating frequency at the midpoint of said series arm.
  • FIG. 1 is a perspective view of an evanescent mode waveguide hybrid T-junction
  • FIG. 2 is a basic schematic diagram of a known form of hybrid junction
  • FIGS. 3 and 4 are equivalent circuits of the junction of FIG. 1
  • FIGS. 5 to 12 are equivalent circuits of alternative forms of evanescent mode resonators
  • FIG. 13 is an equivalent circuit of the junction of FIG. 1,
  • FIGS. 14 and 15 are all-pass filter networks
  • FIGS. 16 and 17 are equivalent circuits of single-section and multi-section phase equalizers respectively using an evanescent mode hybrid junction and junctions,
  • FIG. 18 is a perspective view of a multi-section phase equalizer
  • FIG. 19 shows part of a known form of phase equalizer
  • FIG. 20 is a perspective view of an evanescent mode phase equalizer
  • FIGS. 21 and 22 are perspective views of alternative forms of an evanescent mode waveguide series (E) T-junction,
  • FIGS. 23 and 24 are perspective views of alternative forms of an evanescent mode waveguide shunt (H) T-junction,
  • FIGS. 25 and 26 are perspective views of alternative forms of an evanescent mode waveguide right angle (E) bend.
  • FIGS. 27 and 28 are perspective views of alternative forms of an evanescent mode waveguide right angle (H) bend.
  • a rectangular main waveguide 1 has a first branch rectangular waveguide 2 directly connected into one side wall, and a second branch rectangular waveguide 3 directly connected into one broad wall, the branch 3 being located transversely to the main guide 1 symmetrically about the broad wall center line of the branch 2.
  • adjustable capacitive screws4 and 5 Located on the broad wall longitudinal center line of the guide 1 are adjustable capacitive screws4 and 5, each at the mid-point of the length l of the respective portion of the guide 1 on either side of the branch junction and each extending into the respective portion of the guide.
  • a thin dielectric plate 7 which constitutes a capacitive obstacle.
  • An adjustable dielectric screw 8 moveable in or out of a corresponding threaded transverse aperture 9 in the plate 7 may be provided for tuning purposes.
  • an adjustable capacitive screw 10 Located on the broad wall longitudinal center line of the branch 3, at a distance 1 from the junction plane and the dielectric plate 7 is an adjustable capacitive screw 10 extending into the branch 3.
  • an adjustable capacitive screw 11 Located at the center of the junction, i.e. at the intersection point of the guide land the branch 2 center lines, is an adjustable capacitive screw 11.
  • the waveguide arrangement shown in FIG. 1 is designed to function as an evanescent mode hybrid T-junction, and accordingly all the guide is dimensioned to have a cut-off frequency above the required operating frequency.
  • dominant mode waveguide ceases to propagate progressive waves below its cut-off frequency, and the mode is said to be evanescent.
  • Waveguide in which the dominant mode is evanescent has a positive imaginary (inductive) characteristic impedance 2,) to an incident TE mode and a real propagation constant (7), and therefore behaves es sentially as a pure reactance. If a short section of this guide is terminated in an obstacle which presents a conjugate (capacitive) reactance at a frequency below the cut-off frequency, the incident power at that frequency will be completely transmitted through the section.
  • the basic requirement for a four-port matched hybrid junction is a type of lattice (bridge) network which in its more restricted form consists of a bridged-T network.
  • a network with these properties, realized in propagating guide is a resonant slot hybrid junction which has been fully described in Resonant-slot hybrid junctions and channel dropping filters G.F. Craven, D.W. St-opp and RR. Thomas, Proc. I.E.E., Vol. 112, No. 4, Apr. 1965, pp. 669-680, and British Patent specifications 987,593 and 1,053,071.
  • each of the conjugate arms are provided by a length of main rectangular waveguide, and each of the other two arms is provided by a branch waveguide joined to a broad wall of the main waveguide.
  • There is a transverse resonant slot in the main waveguide providing coupling between the first mentioned two arms and one of the other arms, and a longitudinal resonant slot in the main waveguide providing coupling to the remaining other arm.
  • FIG. 2 This can be represented as shown in FIG. 2, with the main rectangular propagating waveguide length 20 having a transverse (series) resonant slot 21 and'a longitudinal (shunt) resonant slot 22.
  • the two branch guides, one to each slot, are not shown.
  • the shunt and series slots are in the same reference plane, and the transverse (series) slot 21 couples only to the transverse component of the magnetic field; the longitudinal (shunt) slot 22 coupled only to the longitudinal component of the magnetic field.
  • the two slots do not couple to each other.
  • the longitudinal slot 22 appears at its reference plane in the main guide as a series resonant circuit.
  • the equivalent circuit of FIG. 3 shows an equivalent quarter-wave line (M4) which inverts the parallel resonant circuit to a series resonant circuit in the main guide.
  • the necessary conditions for matching the junction are derived from inspection of FIG. 3.
  • the impedance connected to the series transformer terminals is 22 so that for a match.
  • the impedance connected across the shunt transformer terminals is Z /2 and for a match 01/ o1 n3' ip' 2n
  • the branch guide 2 functions as the shunt arm and that the guide 3 functions as the series arm.
  • evanescent mode resonator Two types are possible 11' section and T section. The classification follows from either a capacitance at each end of a length I of evanescent guide (11 section), or one capacitance in the center of a length l of evanescent guide (T section). These two types are shown in FIGS. 5 and 6 respectively, and their equivalent circuits in FIGS. 7 and 8.
  • FIGS. 9 and show the circuits of FIGS. 7 and 8 respectively redrawn to include such a network, the impedance inverting networks being enclosed in solid rectangles.
  • FIGS. 9 and 10 the resonant elements are effectively connected together by equivalent quarter-wave lines.
  • the 11' section resonator appears as shown in FIG. 11, and this is the type of circuit (parallel resonant) required for the series arm 3
  • Z image impedance
  • Z sinh yl the phase constant of the network
  • the T section resonator appears as shown in FIG. 12, and seen from its input terminals behaves as a series resonator. This is the type of circuit required for the shunt arm 2.
  • a second characteristic of the series resonator of FIG. 12 is the shunt element (shown within the dashed outline rectangle) which is the remnant of the original section of FIG. 10 when it is modified to include the impedance inverter at the input terminals.
  • the equivalent source impedance With a load resistance of R, the equivalent source impedance consists of the load resistance and the remnant, which is an inductive reactance Z tanh in parallel.
  • the equivalent source impedance, 2,, expressed in series form is then I This shows that the equivalent series source impedance is reduced by the inductive reactance of the shunt element. If this reactance is controlled by a shunt capacitance, the source resistance can be varied and matched to the load impedance.
  • FIG. 13 shows the equivalent circuit of the evanescent mode hybrid T-junction as a bridged-T network, analogous to the bridged-T network shown in FIG. 4, but representing the impedance of the main waveguide 1 as functions of the inductive characteristic impedance (2 of evanescent waveguide, y, and the length I, of each portion of the guide 1 on each side of the junction.
  • the matching parameters of the series arm 3 are the tuning of the parallel resonant circuit (by screw 8 and/or screw 10) at the input terminals to control the reactive component, and the suitable selection of the length 1 to control the impedance transformation.
  • the matching parameters of the shunt arm 2 are similar.
  • the capacitive screw 6 is tuned to control the reactive component of the series resonant circuit, and the length 1 is selected to control the impedance transformation. Minor fine adjustment can be made by the screw 11 to provide a variable source impedance to the shunt arm as already described.
  • the screws 4 and 5 are tuned to give the earlier mentioned conjugate match condition for full energy transfer through the respective portions.
  • each of the main waveguide portions I may each contain two spaced capacitive obstacles, one at each end of the length 1,.
  • capacitive screws have been described for obtaining the necessary capacitive reactances, it is to be understood that any suitable means of obtaining the required capacitive reactances may be used.
  • an all-pass filter or all-pass network are illustrated in the lattice or bridge network of FIG. 14 and FIG. 15.
  • Such a network transmits energy from zero frequency to infinite frequency, and with correct choice of component values no amplitude change occurs.
  • the phase of the input to output voltage is, however, a function of frequency, as is evident from the extreme conditions; at zero frequency cur rent takes the ADCB path, whereas at infinite frequency current takes the ACDB path.
  • the network has a maximum phase change of All-pass filters of this type are used to correct the phase characteristics of conventional low-pass filters.
  • FIG. 16 to introduce series and parallel resonant circuits, the network can be used as a correction network for bandpass filters.
  • This general lattice structure can be reduced to a bridged-T network, and therefore the structure of FIG. 4, and FIG. 13, is applicable to all-pass network applications.
  • the basic design variable is the cavity length I. Z, Z sinh -yl) is used as a variable and the L/C ratio treated as a constant.
  • a multi-section phase-equalizer is shown in FIG. 17, and is realized either by directly coupling together in cascade the main waveguide portions of a corresponding number of hybrid junctions each as shown in FIG. 1, or by an integral structure as shown in FIG. 18, in which there is an effective merging of output-input main arms of successive hybrid junctions into a single common arm, and like references to FIG. 1 have been used.
  • the input for phase-correction is applied to one end main guide 1A and the corrected output derived from the other end ID of the main guide, and each series and shunt arm 2 and 3 is terminated by a short circuit (not shown).
  • the equalizer is realized with two identical bandpass filters 30 each in the two shortcircuited (31) arms in the way shown in FIG. 19.
  • the equivalent quarter wave shift can be realized as shown in FIG. 20 by having one main arm 1 of the hybrid junction comprising a series resonant ('l" section) cavity containing a single central capacitive screw 5, and the other main arm 1 comprising a parallel resonant (11' section) cavity containing a capacitive screw 4 located at the end of the section remote from the junction and a dielectric plate 40, which may have an adjustable dielectric screw 41, filling the guide section at the junction plane between the end of the section and the broad wall of the series arm 3.
  • Each of the main arms then couple into identical multi-section bandpass filters (not shown) terminated by a short circuit.
  • Input is the shunt arm 2, and output the series arm 3.
  • the bandpass filters integrate into the hybrid junction assembly.
  • Tjunctions both series (E) and shunt (H) are necessary components in many systems. Either type of junction can readily be realized in evanescent guide because either junction is merely a special case of an evanescent mode hybrid junction in which one of the isolated arms (shunt or series) is short circuited at its junction with the other arms.
  • a right angled bend can be considered as a special case of a T-junction with one of its arms short cir-' cuited.
  • FIGS. 21 and 22 show alternative forms of an evanescent mode series (E) waveguide T-junction, with, in FIG. 21, three T-section evanescent mode resonators, each of length 1, between capacitive screw 4 and dielectric plate 7, between capacitive screw 5 and dielectric plate 7, and in the series arm 3 between dielectric plate 7 and capacitive screw 10.
  • E evanescent mode series
  • FIG. 22 there are three 1r section evanescent mode resonators, each of half length 1/2, provided respectively between dielectric plates 40A, 40B and 7.
  • FIGS. 23 and 24 show alternative forms of an evanescent mode shunt (H) waveguide T-junction.
  • H evanescent mode shunt
  • FIG. 23 there are three T-section evanescent mode resonators, each of length 1, between capacitive screws 4 and 11, between capacitive screws 5 and 11, and in the shunt arm between capacitive screws 6 and 11.
  • FIG. 24 there are three 11' section evanescent mode resonators, each of half length 1/2, formed respectively between dielectric plates 40A, 40B and 6.
  • FIGS. 25 and 2 show alternative forms of an evanescent mode waveguide right angle (H) band.
  • H evanescent mode waveguide right angle
  • FIG. 25 there are two 71' section evanescent mode resonators each of half length l/2 formed respectively between dielectric plate 40A and 7.
  • FIG. 26 there are two T-section evanescent mode resonators, each of length 1, formed between capacitive screws l0, l1 and 4
  • FIGS. 27 and 28 show alternative forms of an evanescent mode right angle (E) band.
  • E evanescent mode right angle
  • FIG. 27 there are two 11' section evanescent mode resonators, each of half length 1/2, formed respectively between dielectric plates 40 and 6.
  • FIG. 28 there are two T-section evanescent mode resonators, each of length 1, formed between capacitive screws 4, 6 and l l.
  • a rectangular main waveguide forming first and second symmetrical arms of the junction dimensioned to have a cutoff frequency above the operating frequency
  • a first branch rectangular waveguide dimensioned to have a cut-off frequency above the operating frequency, directly coupled into a first wall of said main waveguide forming a series arm to provide a parallel resonant circuit at the operating frequency;
  • a second branch rectangular waveguide dimensioned to have a cutoff frequency above the operating frequency, directly coupled to a second wall of said main waveguide forming a shunt arm to provide a series resonant circuit at the operating frequency at the midpoint of said series arm;
  • a third capacitive obstacle located at the junction of said first and second symmetrical arms.

Landscapes

  • Control Of Motors That Do Not Use Commutators (AREA)
  • Waveguide Connection Structure (AREA)
US40074A 1969-06-06 1970-05-25 Hybrid t-junction constructed in waveguide having a cut-off frequency above the operating frequency Expired - Lifetime US3657668A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB28698/69A GB1200870A (en) 1969-06-06 1969-06-06 Improvements in electrical waveguide arrangements

Publications (1)

Publication Number Publication Date
US3657668A true US3657668A (en) 1972-04-18

Family

ID=10279677

Family Applications (1)

Application Number Title Priority Date Filing Date
US40074A Expired - Lifetime US3657668A (en) 1969-06-06 1970-05-25 Hybrid t-junction constructed in waveguide having a cut-off frequency above the operating frequency

Country Status (8)

Country Link
US (1) US3657668A (de)
JP (1) JPS5114234B1 (de)
BE (1) BE751513A (de)
BR (1) BR7019531D0 (de)
CH (1) CH518014A (de)
DE (1) DE2027602A1 (de)
FR (1) FR2045890B1 (de)
GB (1) GB1200870A (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0209220A1 (de) * 1985-05-20 1987-01-21 Texas Instruments Incorporated Zuleitung für eine an beiden Enden gespeiste Resonanzschlitzatennenanordnung
US5019831A (en) * 1985-05-20 1991-05-28 Texas Instruments Incorporated Dual end resonant slot array antenna feed having a septum
US5611239A (en) * 1994-09-21 1997-03-18 Magnetrol International Inc. Microwave point instrument with self-test circuit
WO1999000865A1 (en) * 1997-06-30 1999-01-07 Raytheon Company Compact, ultrawideband matched e-plane power divider
CN101694894A (zh) * 2009-10-16 2010-04-14 成都赛纳赛德科技有限公司 波导连通器
CN104091996A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形h面支节
CN104091994A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形he面支节
CN104091997A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形e面支节
CN104091995A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形eh面支节
CN104091998A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 三路支节
US20150372370A1 (en) * 2014-06-24 2015-12-24 The Boeing Company Enhanced hybrid-tee coupler
US20220140463A1 (en) * 2020-10-30 2022-05-05 The University Of Chicago Millimeter-wave resonator and associated methods

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5527973A (en) * 1978-08-21 1980-02-28 Fujitsu Ltd Vehicle mount radar

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2685065A (en) * 1949-02-17 1954-07-27 Gen Precision Lab Inc Microwave power divider

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2649576A (en) * 1949-10-07 1953-08-18 Bell Telephone Labor Inc Pseudohybrid microwave device
US3058072A (en) * 1956-11-15 1962-10-09 Raytheon Co Microwave filters

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2685065A (en) * 1949-02-17 1954-07-27 Gen Precision Lab Inc Microwave power divider

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0209220A1 (de) * 1985-05-20 1987-01-21 Texas Instruments Incorporated Zuleitung für eine an beiden Enden gespeiste Resonanzschlitzatennenanordnung
US5019831A (en) * 1985-05-20 1991-05-28 Texas Instruments Incorporated Dual end resonant slot array antenna feed having a septum
US5611239A (en) * 1994-09-21 1997-03-18 Magnetrol International Inc. Microwave point instrument with self-test circuit
WO1999000865A1 (en) * 1997-06-30 1999-01-07 Raytheon Company Compact, ultrawideband matched e-plane power divider
CN101694894A (zh) * 2009-10-16 2010-04-14 成都赛纳赛德科技有限公司 波导连通器
CN105281002A (zh) * 2014-06-24 2016-01-27 波音公司 增强混合t形耦合器
US20150372370A1 (en) * 2014-06-24 2015-12-24 The Boeing Company Enhanced hybrid-tee coupler
EP2960984A1 (de) * 2014-06-24 2015-12-30 The Boeing Company Verbesserter hybrid-tee-koppler
US9373880B2 (en) * 2014-06-24 2016-06-21 The Boeing Company Enhanced hybrid-tee coupler
US9997820B2 (en) * 2014-06-24 2018-06-12 The Boeing Company Enhanced hybrid-tee coupler
CN105281002B (zh) * 2014-06-24 2019-10-18 波音公司 增强混合t形耦合器
CN104091994A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形he面支节
CN104091997A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形e面支节
CN104091995A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形eh面支节
CN104091998A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 三路支节
CN104091996A (zh) * 2014-07-24 2014-10-08 成都赛纳赛德科技有限公司 T形h面支节
US20220140463A1 (en) * 2020-10-30 2022-05-05 The University Of Chicago Millimeter-wave resonator and associated methods
US11682819B2 (en) * 2020-10-30 2023-06-20 The University Of Chicago Millimeter-wave resonator and associated methods

Also Published As

Publication number Publication date
BR7019531D0 (pt) 1973-02-15
FR2045890A1 (de) 1971-03-05
BE751513A (fr) 1970-12-07
GB1200870A (en) 1970-08-05
JPS5114234B1 (de) 1976-05-07
FR2045890B1 (de) 1975-01-10
CH518014A (de) 1972-01-15
DE2027602A1 (de) 1970-12-10

Similar Documents

Publication Publication Date Title
US3697898A (en) Plural cavity bandpass waveguide filter
US3452300A (en) Four port directive coupler having electrical symmetry with respect to both axes
US3657668A (en) Hybrid t-junction constructed in waveguide having a cut-off frequency above the operating frequency
Levy Directional couplers
US3882434A (en) Phase equalized filter
US4360793A (en) Extracted pole filter
US3969692A (en) Generalized waveguide bandpass filters
Pfitzenmaier Synthesis and realization of narrow-band canonical microwave bandpass filters exhibiting linear phase and transmission zeros
US2633492A (en) Guided wave frequency range, frequency selective and equalizing structure
GB2284311A (en) Hybrid notch filter
Yamamoto et al. Coupled nonuniform transmission line and its applications
CA1153432A (en) Bandpass filter with plurality of wave-guide cavities
US2767379A (en) Electromagnetic wave equalization
US2639326A (en) Electromagnetic wave microwave frequency structure using hybrid junctions
US20160276724A1 (en) Bandstop filters with minimum through-line length
US3668564A (en) Waveguide channel diplexer and mode transducer
US3034076A (en) Microwave diplexer
Young Microwave filters-1965
US3329884A (en) Frequency multiplier utilizing a hybrid junction to provide isolation between the input and output terminals
US3142028A (en) Waveguide stop-band filter utilizing hybrid circuit with lossy resonant cavities in branch arms
US2724806A (en) Electromagnetic wave hybrid junction coaxial transmission line structures
US3605044A (en) Filter structures using bimodal, bisymmetric networks
US3639862A (en) Waveguide filter utilizing evanescent waveguide, with tunable ferrite loading
US3748600A (en) Power combining network
US3449696A (en) Dual section all pass lattice filter wherein nonlinearities of two sections cancel

Legal Events

Date Code Title Description
AS Assignment

Owner name: STC PLC,ENGLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423

Owner name: STC PLC, 10 MALTRAVERS STREET, LONDON, WC2R 3HA, E

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423