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Slot line nonreciprocal phase shifter

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US3602845A
US3602845A US3602845DA US3602845A US 3602845 A US3602845 A US 3602845A US 3602845D A US3602845D A US 3602845DA US 3602845 A US3602845 A US 3602845A
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slot
ferrite
phase
line
toroid
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John P Agrios
Nathan Lipetz
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US Secretary of Army
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US Secretary of Army
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01PWAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00Auxiliary devices
    • H01P1/18Phase-shifters
    • H01P1/19Phase-shifters using a ferromagnetic device
    • H01P1/195Phase-shifters using a ferromagnetic device having a toroidal shape

Abstract

A nonreciprocal microwave energy phase shifter utilizing a slot line for propagating microwave energy and a ferrite member which is magnetically biased to produce a magnetic field therein which is orthogonal to and interacts with the RF magnetic field cyclically generated along the slot line. The ferrite may be in the form of a toroid to provide a closed-loop magnetic field and which is produced by a latching current.

Description

PATENTED-Auw I971 20 FERRITE F IG.

DIELECTRIC SUBSTRATE INVENTORS JOHN P. AGR/OS a NATHAN L/PETZ BY J 54W j 'AGENT 5M 4 vhi ATTORNEYS United States Patent John P. Agrios Long Branch;

Nathan Llpetz, Oakburst, both of, NJ. 6,085 Jan. 27, 1970 Aug. 31, I971 The United States of America as represented by the Secretary of the Army inventors Appl. No. Filed Patented Assignee SLOT LINE NONRECIPROCAL PHASE SHIFTER 16 Claims, 5 Drawing Figs.

us. Cl ass/24.1, 333/84 R Int Cl H0lp 1/32 Field ofSearch 33311.1, 24.1, 84 M References Cited OTHER REFERENCES G. H. Robinson et al.. Slot Line Application to Miniature Ferrite Devices, IEEE Trans. on MTT, Dec. 1969, pp. 1097-1101333-84 M G. H. Robinson et al., Application of Slot Line T0 Miniature Ferrite Devices, 1969 PGM'IT Symposium Record, pp. 106- Primary Examiner-Herman Karl Saalbach Assistant Examiner-Paul L. Gensler Attameys- Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Jack H. Stanley ABSTRACT: A nonreciprocal microwave energy phase shifter utilizing a slot line for propagating microwave energy and a ferrite member which is magnetically biased to produce a magnetic field therein which is orthogonal to and interacts with the RF magnetic field cyclically generated along the slot line. The ferrite may be in the form of a toroid to provide a closed-loop magnetic field and which is produced by a latching current.

SLOT LINE NONRECIPROCAL PHASE SHIFTER BACKGROUND OF THE INVENTION This invention relates to nonreciprocal microwave devices and more particularly to nonreciprocal phase-shifting devices employing a slot line for propagating microwave energy. A nonreciprocal phase-shifting device is one which will shift by a given amount the phase of microwave energy passing in one direction through the device and will shift by a different amount the phase of the microwave energy passing in the opposite direction through such device. In the microwave region, miniaturization of components becomes an absolute necessity, and since presently available phase-shifting devices are rather complicated and bulky, such devices have proved to be impractical for use in microwave circuitry.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide an improved nonreciprocal phase-shifting device for microwave systems which are extremely small and light in weight.

It is another object of the present invention to provide an improved nonreciprocal phase-shifting device adapted for use with slot lines.

In accordance with one embodiment of the invention, the nonreciprocal phase shifter includes a ferrite substrate, a slot line on one surface of the substrate for propagating RF microwave energy, and means for producing in the substrate a magnetic bias field orthogonally oriented to the RF magnetic field of the propagated microwave energy. The ferrite substrate may be in the form of a toroid having a substantial longitudinaldimension and have a square hysteresis loop magnetization characteristic. t

In another embodiment of the invention, the nonreciprocal phase shifter includes a dielectric substrate with the slot line on one surface of the substrate. Also included is a ferrite toroid positioned over the slot line and means for producing a closed magnetic field loop in the toroid which is characterized by a square hysteresis loop.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description'taken in connection with the accompanying drawing in which:

FIG. 1 illustrates one embodiment of the invention;

FIG. 2 illustrates another embodiment of the invention wherein a ferrite toroid is utilized to provide a latching-type phase shifter; 1

FIG, 3 illustrates a modified version of the phase shifter shown in FIG. 2; and

FIGS. '4 and 5 illustrate a phase shifter in accordance with the invention wherein a dielectric substrate is utilized as the 7 support for the slot line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown at 10 a ferrite substrate on which is deposited, by any suitable means well known in the art, a slot line 12. Slot line 12 comprises a parallel pair of longitudinally spaced metal strips 14 separated by a very narrow slot 16. A variable DC magnetic bias field is applied transversely to ferrite substrate 10 in the direction H by any suitable means well known in the art. Microwave energy propagated along the slot line 12 sets up anRF electric field across the slot 16 and an RF'magnetic field as at 17 whose field lines are orthogonal to the RF electric field. Since the RF magnetic field linescurve and return to the slot I6 at onehalfwave intervals they may be considered to be elliptically propagating wave and the electron spins of the ferrite to cause the permeability of the ferrite to be different for the two directions of microwave propagation. While the physical length of the slot line 12 willintroduce a delay or phase shift in the propagated microwave energy, the change in permeability in the ferrite superimposes on this phase shift a further phase shift hereinafter referred to as a differential phase shift. By

changing the magnitude of the applied DC magnetic bias field across ferrite substrate 10, the magnitude of the differential phase shift is changed and hence a variable microwave phase shifter results. The nonreciprocal characteristic of the phase shifter is due to the orthogonal orientation of the RF magnetic field and the DC magnetic bias field which may be varied by any suitable means as, for example, by an electromagnet.

FIGS. 2-5 illustrate digital-latching-type phase shifters employing the same principles of operation as that shown in FIG. 1. In these figures like reference numerals refer to like elements. Referring now to FIG. 2, at 20 there is shown a ferrite toroid having a substantial longitudinal dimension and a square hysteresis loop magnetization characteristic. The slot line 12 is longitudinally and'axially positioned on an outer surface of ferrite 20 such that the slot 16 of slot line 12 is substantially along a line parallel to the longitudinal axis of ferrite toroid 20. A single or multiple wound conductor 22 extends longitudinally through the opening 24 of ferrite toroid 20 and is looped around an inner and outer surface of the toroid as shown. The terminals of conductor 22 are connected to a pulsed DC current source 26. While the conductor 22 is shown looped around the toroid surface distal the slot line 12, the conductor loop 22 may also be wound around any other portions of ferrite toroid 20 which does not include slot line I2. With the pulsed DC current in the direction shown by arrow 27, the closed magnetic field path produced in ferrite toroid 20 will be that indicated at 28. As in FIG. I, the DC magnetic bias field and the RF magnetic field of a wave propagated along slot line 12 are orthogonally oriented to provide the interaction for achieving'a nonreciprocal phase shift of the RF-propagated wave. Latching is obtained by using the square loop hysteresis characteristic of the ferrite toroid 20 Thus, after the DC energizing pulse is removed, the magnetization will follow the square loop hysteresis curve of the ferrite material so that ferrite toroid 20 will remain magnetized at remanence. By changing the amplitude or the pulse width of the current pulse from source 26, the remanent magnetization of ferrite toroid 20 can be changed to yield a change in the differential phase shift ofthe device.

In FIG. 3, slot line 12 is shown positioned longitudinally within the ferrite toroid 20 along one inner surface thereof. As in FIG. 2, the slot 16 of slot line 12 is along a line parallel to the longitudinal axis of the toroid 20 and the ferrite is energized by passing a latching DC current pulse through a suitable wire conductor 22. The latching and phase-shifting operation of the device shown in FIG. 3 is similar to that shown in FIG. 2.

In FIG. 4, the slot line 12 is positioned on a dielectric substrate 30 and the ferrite toroid 20 is positioned above the slot line 12 such that the slot I6 is parallel to the longitudinal axis of the toroid. The ferrite toroid 20 is energized by passing a DC current pulse through a suitable wire conductor 22 to provide the orthogonal magnetic bias means. RF energy propagated along slot line 12 will produce an RF magnetic field which is elliptically polarized along the longitudinal dimension of slot I2 so that it interacts with the orthogonally oriented latching magnetic bias. If desired, substrate 30 may be replaced by a second ferrite toroid magnetized in a direction opposite to that shown for ferrite toroid 20.

FIG. 5 illustrates another embodiment which employs the same principle of operation as that shown in FIGS. 1-4. Referring now to FIG. 5, the substrate 30 on which slot line 12 is longitudinally positioned is inclosed by ferrite toroid 32. A latching current is provided by passing a DC pulse through wire conductor 22 which extends longitudinally through a central aperture 34 provided therefor in substrate 30.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

l. A nonreciprocal microwave energy phase shifter comprising a ferrite substrate, a slot line on one surface of said substrate for propagating RF microwave energy,

and means for producing in said ferrite substrate a magnetic bias field orthogonally oriented to the RF magnetic field of said propagated microwave energy.

2. The phase shifter in accordance with claim 1 wherein said slot line comprises a pair of longitudinally spaced metal strips separated by a very narrow slot, and wherein said RF magnetic field is elliptically polarized along said narrow slot.

3. The phase shifter in accordance with claim 2 wherein said ferrite substrate is in the form ofa toroid having a substantial longitudinal dimension.

4, The phase shifter in accordance with claim 3 wherein said slot is along a line parallel to the longitudinal axis of said ferrite toroid.

5. The phase shifter in accordance with claim 3 wherein the magnetization of said ferrite toroid is characterized by a square hysteresis loop.

6. The phase shifter in accordance with claim 4 wherein the magnetization of said ferrite toroid is characterized by a 8. The phase shifter in accordance with claim 4 wherein said slot line is on one inner surface of said ferrite toroid and said magnetic-field bias-producing means is in circuit with a portion of said ferrite toroid not including said slot line.

9. A nonreciprocal microwave energy phase shifter comprising a substrate, a slot line on one surface of said substrate for propagating RF microwave energy,

a ferrite toroid positioned over said slot line,

and means for producing a closed magnetic-field loop in said toroid, said magnetic field being characterized by a square hysteresis loop.

10. The phase shifter in accordance with claim 9 wherein said substrate is a dielectric.

11, The phase shifter in accordance with claim 10 and further including a latching current-carrying conductor extending through the aperture of said ferrite toroid.

12. The phase shifter in accordance with claim 11 wherein said ferrite toroid is above said slot line.

13. The phase shifter in accordance with claim 10 wherein said ferrite toroid surrounds said slot line and said dielectric substrate.

- 14. The phase shifter in accordance with claim 13 and further including a central aperture in said dielectric substrate and a latching current conductor extending through said aperture.

15. The phase shifter in accordance with claim 12 wherein the slot of said slot line is along a line parallel to the axis of said ferrite toroid.

16. The phase shifter in accordance with claim 9 wherein said substrate is a second ferrite toroid.

Claims (16)

1. A nonreciprocal microwave energy phase shifter comprising a ferrite substrate, a slot line on one surface of said substrate for propagating RF microwave energy, and means for producing in said ferrite substrate a magnetic bias field orthogonally oriented to the RF magnetic field of said propagated microwave energy.
2. The phase shifter in accordance with claim 1 wherein said slot line comprises a pair of longitudinally spaced metal strips separated by a very narrow slot, and wherein said RF magnetic field is elliptically polarized along said narrow slot.
3. The phase shifter in accordance with claim 2 wherein said ferrite substrate is in the form of a toroid having a substantial longitudinal dimension.
4. The phase shifter in accordance with claim 3 wherein said slot is along a line parallel to the longitudinal axis of said ferrite toroid.
5. The phase shifter in accordance with claim 3 wherein the magnetization of said ferrite toroid is characterized by a square hysteresis loop.
6. The phase shifter in accordance with claim 4 wherein the magnetization of said ferrite toroid is characterized by a square hysteresis loop.
7. The phase shifter in accordance with claim 3 wherein said slot line is on one outer surface of said ferrite toroid and said magnetic-field bias-producing means is in circuit with a portion of said ferrite toroid not including said slot line.
8. The phase shifter in accordance with claim 4 wherein said slot line is on one inner surface of said ferrite toroid and said magnetic-field bias-producing means is in circuit with a portion of said ferrite toroid not including said slot line.
9. A nonreciprocal microwave energy phase shifter comprising a substrate, a slot line on one surface of said substrate for propagating RF microwave energy, a ferrite toroid positioned over said slot line, and means for producing a closed magnetic-field loop in said toroid, said magnetic field being characterized by a square hysteresis loop.
10. The phase shifter in accordance with claim 9 wherein said substrate is a dielectric.
11. The phase shifter in accordance with claim 10 and further including a latching current-carrying conductor extending through the aperture of said ferrite toroid.
12. The phase shifter in accordance with claim 11 wherein said ferrite toroid is above said slot line.
13. The phase shifter in accordance with claim 10 wherein said ferrite toroid surrounDs said slot line and said dielectric substrate.
14. The phase shifter in accordance with claim 13 and further including a central aperture in said dielectric substrate and a latching current conductor extending through said aperture.
15. The phase shifter in accordance with claim 12 wherein the slot of said slot line is along a line parallel to the axis of said ferrite toroid.
16. The phase shifter in accordance with claim 9 wherein said substrate is a second ferrite toroid.
US3602845A 1970-01-27 1970-01-27 Slot line nonreciprocal phase shifter Expired - Lifetime US3602845A (en)

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Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3678395A (en) * 1970-10-14 1972-07-18 Gte Sylvania Inc Broadband planar balanced circuit
US3707688A (en) * 1971-03-31 1972-12-26 Sperry Rand Corp High frequency gyromagnetic device employing slot transmission line
US3891949A (en) * 1972-11-30 1975-06-24 Licentia Gmbh Slit line-type microwave circuit construction
US3968457A (en) * 1974-02-12 1976-07-06 Thomson-Csf Microwave non-reciprocal junction device
US3986149A (en) * 1975-08-29 1976-10-12 The United States Of America As Represented By The Secretary Of The Air Force High power reciprocal co-planar waveguide phase shifter
US4027253A (en) * 1973-05-18 1977-05-31 Societe Lignes Telegraphiques Et Telephoniques Non-reciprocal broadband slot line device
US4506234A (en) * 1983-06-17 1985-03-19 The United States Of America As Represented By The Secretary Of The Navy Amplitude and phase modulation in fin-lines by electrical tuning
US4980657A (en) * 1989-09-29 1990-12-25 Westinghouse Electric Corp. Coplanar waveguide frequency selective limiter
US5772820A (en) * 1995-08-07 1998-06-30 Northrop Grumman Corporation Process for fabricating a microwave power device
US7138813B2 (en) 1999-06-30 2006-11-21 Cascade Microtech, Inc. Probe station thermal chuck with shielding for capacitive current
US7138810B2 (en) 2002-11-08 2006-11-21 Cascade Microtech, Inc. Probe station with low noise characteristics
US7164279B2 (en) 1995-04-14 2007-01-16 Cascade Microtech, Inc. System for evaluating probing networks
US7176705B2 (en) 2004-06-07 2007-02-13 Cascade Microtech, Inc. Thermal optical chuck
US7187188B2 (en) 2003-12-24 2007-03-06 Cascade Microtech, Inc. Chuck with integrated wafer support
US7190181B2 (en) 1997-06-06 2007-03-13 Cascade Microtech, Inc. Probe station having multiple enclosures
US7221172B2 (en) 2003-05-06 2007-05-22 Cascade Microtech, Inc. Switched suspended conductor and connection
US7221146B2 (en) 2002-12-13 2007-05-22 Cascade Microtech, Inc. Guarded tub enclosure
US7250779B2 (en) 2002-11-25 2007-07-31 Cascade Microtech, Inc. Probe station with low inductance path
US7250626B2 (en) 2003-10-22 2007-07-31 Cascade Microtech, Inc. Probe testing structure
US7268533B2 (en) 2001-08-31 2007-09-11 Cascade Microtech, Inc. Optical testing device
US7330023B2 (en) 1992-06-11 2008-02-12 Cascade Microtech, Inc. Wafer probe station having a skirting component
US7330041B2 (en) 2004-06-14 2008-02-12 Cascade Microtech, Inc. Localizing a temperature of a device for testing
US7348787B2 (en) 1992-06-11 2008-03-25 Cascade Microtech, Inc. Wafer probe station having environment control enclosure
US7352168B2 (en) 2000-09-05 2008-04-01 Cascade Microtech, Inc. Chuck for holding a device under test
US7368925B2 (en) 2002-01-25 2008-05-06 Cascade Microtech, Inc. Probe station with two platens
US7492172B2 (en) 2003-05-23 2009-02-17 Cascade Microtech, Inc. Chuck for holding a device under test
US7535247B2 (en) 2005-01-31 2009-05-19 Cascade Microtech, Inc. Interface for testing semiconductors
US7554322B2 (en) 2000-09-05 2009-06-30 Cascade Microtech, Inc. Probe station
US7656172B2 (en) 2005-01-31 2010-02-02 Cascade Microtech, Inc. System for testing semiconductors
US8319503B2 (en) 2008-11-24 2012-11-27 Cascade Microtech, Inc. Test apparatus for measuring a characteristic of a device under test

Cited By (56)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3678395A (en) * 1970-10-14 1972-07-18 Gte Sylvania Inc Broadband planar balanced circuit
US3707688A (en) * 1971-03-31 1972-12-26 Sperry Rand Corp High frequency gyromagnetic device employing slot transmission line
US3891949A (en) * 1972-11-30 1975-06-24 Licentia Gmbh Slit line-type microwave circuit construction
US4027253A (en) * 1973-05-18 1977-05-31 Societe Lignes Telegraphiques Et Telephoniques Non-reciprocal broadband slot line device
US3968457A (en) * 1974-02-12 1976-07-06 Thomson-Csf Microwave non-reciprocal junction device
US3986149A (en) * 1975-08-29 1976-10-12 The United States Of America As Represented By The Secretary Of The Air Force High power reciprocal co-planar waveguide phase shifter
US4506234A (en) * 1983-06-17 1985-03-19 The United States Of America As Represented By The Secretary Of The Navy Amplitude and phase modulation in fin-lines by electrical tuning
US4980657A (en) * 1989-09-29 1990-12-25 Westinghouse Electric Corp. Coplanar waveguide frequency selective limiter
US7330023B2 (en) 1992-06-11 2008-02-12 Cascade Microtech, Inc. Wafer probe station having a skirting component
US7589518B2 (en) 1992-06-11 2009-09-15 Cascade Microtech, Inc. Wafer probe station having a skirting component
US7348787B2 (en) 1992-06-11 2008-03-25 Cascade Microtech, Inc. Wafer probe station having environment control enclosure
US7595632B2 (en) 1992-06-11 2009-09-29 Cascade Microtech, Inc. Wafer probe station having environment control enclosure
US7492147B2 (en) 1992-06-11 2009-02-17 Cascade Microtech, Inc. Wafer probe station having a skirting component
US7321233B2 (en) 1995-04-14 2008-01-22 Cascade Microtech, Inc. System for evaluating probing networks
US7164279B2 (en) 1995-04-14 2007-01-16 Cascade Microtech, Inc. System for evaluating probing networks
US5772820A (en) * 1995-08-07 1998-06-30 Northrop Grumman Corporation Process for fabricating a microwave power device
US7626379B2 (en) 1997-06-06 2009-12-01 Cascade Microtech, Inc. Probe station having multiple enclosures
US7436170B2 (en) 1997-06-06 2008-10-14 Cascade Microtech, Inc. Probe station having multiple enclosures
US7190181B2 (en) 1997-06-06 2007-03-13 Cascade Microtech, Inc. Probe station having multiple enclosures
US7292057B2 (en) 1999-06-30 2007-11-06 Cascade Microtech, Inc. Probe station thermal chuck with shielding for capacitive current
US7138813B2 (en) 1999-06-30 2006-11-21 Cascade Microtech, Inc. Probe station thermal chuck with shielding for capacitive current
US7616017B2 (en) 1999-06-30 2009-11-10 Cascade Microtech, Inc. Probe station thermal chuck with shielding for capacitive current
US7514915B2 (en) 2000-09-05 2009-04-07 Cascade Microtech, Inc. Chuck for holding a device under test
US7518358B2 (en) 2000-09-05 2009-04-14 Cascade Microtech, Inc. Chuck for holding a device under test
US7688062B2 (en) 2000-09-05 2010-03-30 Cascade Microtech, Inc. Probe station
US7969173B2 (en) 2000-09-05 2011-06-28 Cascade Microtech, Inc. Chuck for holding a device under test
US7352168B2 (en) 2000-09-05 2008-04-01 Cascade Microtech, Inc. Chuck for holding a device under test
US7501810B2 (en) 2000-09-05 2009-03-10 Cascade Microtech, Inc. Chuck for holding a device under test
US7423419B2 (en) 2000-09-05 2008-09-09 Cascade Microtech, Inc. Chuck for holding a device under test
US7554322B2 (en) 2000-09-05 2009-06-30 Cascade Microtech, Inc. Probe station
US7268533B2 (en) 2001-08-31 2007-09-11 Cascade Microtech, Inc. Optical testing device
US7368925B2 (en) 2002-01-25 2008-05-06 Cascade Microtech, Inc. Probe station with two platens
US7550984B2 (en) 2002-11-08 2009-06-23 Cascade Microtech, Inc. Probe station with low noise characteristics
US7295025B2 (en) 2002-11-08 2007-11-13 Cascade Microtech, Inc. Probe station with low noise characteristics
US7138810B2 (en) 2002-11-08 2006-11-21 Cascade Microtech, Inc. Probe station with low noise characteristics
US7498828B2 (en) 2002-11-25 2009-03-03 Cascade Microtech, Inc. Probe station with low inductance path
US7250779B2 (en) 2002-11-25 2007-07-31 Cascade Microtech, Inc. Probe station with low inductance path
US7639003B2 (en) 2002-12-13 2009-12-29 Cascade Microtech, Inc. Guarded tub enclosure
US7221146B2 (en) 2002-12-13 2007-05-22 Cascade Microtech, Inc. Guarded tub enclosure
US7468609B2 (en) 2003-05-06 2008-12-23 Cascade Microtech, Inc. Switched suspended conductor and connection
US7221172B2 (en) 2003-05-06 2007-05-22 Cascade Microtech, Inc. Switched suspended conductor and connection
US7492172B2 (en) 2003-05-23 2009-02-17 Cascade Microtech, Inc. Chuck for holding a device under test
US7876115B2 (en) 2003-05-23 2011-01-25 Cascade Microtech, Inc. Chuck for holding a device under test
US7250626B2 (en) 2003-10-22 2007-07-31 Cascade Microtech, Inc. Probe testing structure
US8069491B2 (en) 2003-10-22 2011-11-29 Cascade Microtech, Inc. Probe testing structure
US7187188B2 (en) 2003-12-24 2007-03-06 Cascade Microtech, Inc. Chuck with integrated wafer support
US7362115B2 (en) 2003-12-24 2008-04-22 Cascade Microtech, Inc. Chuck with integrated wafer support
US7688091B2 (en) 2003-12-24 2010-03-30 Cascade Microtech, Inc. Chuck with integrated wafer support
US7504823B2 (en) 2004-06-07 2009-03-17 Cascade Microtech, Inc. Thermal optical chuck
US7176705B2 (en) 2004-06-07 2007-02-13 Cascade Microtech, Inc. Thermal optical chuck
US7330041B2 (en) 2004-06-14 2008-02-12 Cascade Microtech, Inc. Localizing a temperature of a device for testing
US7656172B2 (en) 2005-01-31 2010-02-02 Cascade Microtech, Inc. System for testing semiconductors
US7940069B2 (en) 2005-01-31 2011-05-10 Cascade Microtech, Inc. System for testing semiconductors
US7898281B2 (en) 2005-01-31 2011-03-01 Cascade Mircotech, Inc. Interface for testing semiconductors
US7535247B2 (en) 2005-01-31 2009-05-19 Cascade Microtech, Inc. Interface for testing semiconductors
US8319503B2 (en) 2008-11-24 2012-11-27 Cascade Microtech, Inc. Test apparatus for measuring a characteristic of a device under test

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