KEITHLEY INSTRUMENTS, INC.

Patent Trials and Appeals Board

Feb 6, 2020

13862135 - (D) (P.T.A.B. Feb. 6, 2020)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
13/862,135 04/12/2013 Kevin Cawley 9151-US0 5577
37965 7590 02/06/2020
MICHAEL A. NELSON
TEKTRONIX, INC.
14150 S. W. KARL BRAUN DRIVE
P.O. BOX 500, M/S 50-LAW
BEAVERTON, OR 97077-0001
EXAMINER
RIVERA-PEREZ, CARLOS O
ART UNIT PAPER NUMBER
2838
NOTIFICATION DATE DELIVERY MODE
02/06/2020 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
eofficeaction@appcoll.com
patdocketing@millernash.com
patents@tektronix.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte KEVIN CAWLEY, WAYNE GOEKE, and
GREGORY SOBOLEWSKI
Appeal 2019-002244
Application 13/862,135
Technology Center 2800

Before LINDA M. GAUDETTE, JEFFREY B. ROBERTSON, and
MICHAEL G. McMANUS, Administrative Patent Judges.

GAUDETTE, Administrative Patent Judge.

DECISION ON APPEAL1
The Appellant2 appeals under 35 U.S.C. § 134(a) from the Examiner’s
decision finally rejecting claims 1, 3, 4, and 6–12.3
We reverse.

1 This Decision includes citations to the following documents: Specification
filed Apr. 12, 2013 (“Spec.”); Final Office Action dated Oct. 6, 2017
(“Final”); Appeal Brief filed Aug. 6, 2018 (“Appeal Br.”); Examiner’s
Answer dated Nov. 16, 2018 (“Ans.”); and Reply Brief filed Jan. 16, 2019
(“Reply Br.”).
2 We use the word “Appellant” to refer to the “applicant” as defined in 37
C.F.R. § 1.42(a). The Appellant identifies the real party in interest as
Keithley Instruments, LLC. Appeal Br. 3.
3 We have jurisdiction under 35 U.S.C. § 6(b).
Appeal 2019-002244
Application 13/862,135

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CLAIMED SUBJECT MATTER
The invention relates “to a power supply that is designed to power a
capacitive device under test (DUT), such as a battery-operated wireless
device that requires high-bandwidth performance such as those that have
current pulse loading and require extremely fast load regulation at the end of
long cables.” Spec. ¶ 17. The power supply simulates the battery to the
DUT, e.g., a cellular phone, or provides an arbitrary voltage to the DUT. Id.
¶¶ 11, 17.
The power supply “is generally designed so that neither the transient
response thereof nor its stability are affected by the cable or the load to
which the cable is connected.” Id. ¶ 21. The power supply is a high-
bandwidth voltage-controlled-current-source (VCCS) for sending power
over the load cables to the DUT. Id. “The stability and transient response
may be set by the current sources gain, gm, and an external capacitor
provided with the power supply and located close to the DUT, e.g., at the
end of the cable.” Id. The voltage-controlled-current-source has a specific,
e.g., high transconductance (gm). Id. ¶ 22. “The output impedance of the
supply at direct current (DC) is generally equal to 1/gm, and the provided
capacitor is typically a very good high-frequency capacitor of 10[µ]F in
value, for example.” Id. “The parasitics of the capacitor may be extremely
small in order to dominate any parallel capacitance supplied by the DUT.”
Id.
Figure 4 illustrates an embodiment of the inventive system, and is
reproduced below. Id. ¶ 15.
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In Figure 4, a VCCS consists of NPN transistor 408 coupled with resistor
409, voltage source 410 (VSET), amplifier 412, and op-amp 406. Spec. ¶ 33.
DUT 402 has voltage VDUT and impedance ZDUT, and cable inductance 404
provides LCABLE. Id. “[C]apacitor 414 . . . is positioned close to the DUT 402
and is large enough to dominate the loop depending on the implementation.
For example, if the capacitance of a cellular phone is 5–10 μF, then the
value of the capacitor 414 should be 10 μF.” Id.
Claim 1, reproduced below, is illustrative of the claimed subject
matter:
1. A system for sourcing a voltage for a device under test
(DUT), comprising:
a voltage-controlled-current source (VCCS);
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Application 13/862,135

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a first cable coupled with a positive terminal of the
VCCS configured to be coupled with a positive terminal of the
DUT via a first cable end;
a second cable coupled with a negative terminal of the
VCCS configured to be coupled with a negative terminal of the
DUT via a second cable end;
a capacitor coupling the first cable to the second cable at
a point between the VCCS and the first and second cable ends,
the capacitor being independent of a capacitance of the DUT,
wherein the capacitor is configured to dominate an open loop
gain frequency roll-off through a gain of one, and wherein the
capacitor is included in a voltage feedback loop for the VCCS
such that a change in voltage across the capacitor causes a
change in current provided by the VCCS.
Appeal Br. 15 (Claims Appendix).
REJECTIONS
1. Claims 1, 3, and 6 are rejected under 35 U.S.C. § 103 as
unpatentable over Keithley (“Stabilizing Fast Transient Response Power
Supply/Load Circuits, Keithley Application Note Series 2870 (Dec. 31
2007)).
2. Claims 4 and 7–10 are rejected under 35 U.S.C. § 103 as
unpatentable over Keithley in view of van Ettinger (US 2006/0273771 A1,
pub. Dec. 7, 2006).
3. Claims 11 and 12 are rejected under 35 U.S.C. § 103 as
unpatentable over Keithley in view of Hashimoto (US 2011/0018549 A1,
pub. Jan 27, 2011).
OPINION
Keithley discloses “Series 2300 Battery/Charger Simulators (fast
transient response power supplies) [that] are . . . designed for powering
RFIC power amplifiers, mobile phone handsets, and other portable,
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battery-operated products in R&D and manufacturing environments.”
Keithley4 p. 1, col. 1. For reference, Keithley Figure 2 is reproduced below.
Keithley Figure 2 is a “Simplified Series 2300 measurement schematic with
reactive load and remote-sense feedback.” Id. at col. 2.
The Examiner found that Keithley discloses a system for sourcing a
voltage for a device under test (DUT) as recited in claim 1, with the
exception of a “capacitor . . . configured to dominate an open loop gain
frequency roll-off through a gain of one” (claim 1). See Final 2–3. The
Examiner found that one of ordinary skill in the art would have configured
Keithley’s capacitor to dominate an open loop gain frequency roll-off
through a gain of one to obtain more stable regulation with a faster transient
response. Id. at 3.
The Appellant argues that the Examiner erred reversibly in finding
that Keithley’s power supply 230X is a VCCS. Appeal Br. 10. The
Appellant argues that power supply 230X is a voltage-controlled-voltage-
source (“VCVS”). Id. In support of this argument, the Appellant quotes

4 Keithley does not include page numbers. For citation purposes, we have
numbered the pages as 1–6.
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Keithley page 1, column 2: “[t]he sense amplifier measures the voltage
directly at the load to force the power supply output to increase its
voltage to overcome the losses in the test leads and fixture to ensure the
desired (or programmed) voltage is applied to the load.” Appeal Br. 10–11.
The Appellant also argues that Keithley teaches away from including “a
capacitor ‘configured to dominate an open loop gain frequency roll-off
through a gain of one’ as recited in claim 1.” Appeal Br. 11; see also id. at
12 (citing Keithley p. 2, col. 1).
The Examiner determines that “[t]he term ‘voltage-controlled-current
source’ means that through an input voltage, an output current source is
controlled.” Ans. 2. The Examiner contends that Keithley’s power supply
230X inputs a voltage Vsense from the output voltage Vout and, based on input
voltage Vsense, power supply 230X generates a current through the output
stage (OUT AMP). Id. at 2–3. According to the Examiner, “[i]t is well
known in the art that the last stage of an amplifier has a transistor in series
with a resistor to control the output current.” Id. The Examiner further notes
that “in electrical circuits, the voltage and current are two values directly
related one with another, and if the voltage changes this change is reflected
in the current and vice versa.” Id. (referencing “Kirchhoff’s circuit law
V=I*R”). Regarding the capacitor, the Examiner contends that the
Appellant’s argument is based on Keithley’s description of the
disadvantages of using a large capacitor in parallel with the DUT. Id. at 4.
The Examiner argues that the rejection is based on Keithley’s Figure 2
embodiment, whereas the Appellant’s argument is based on Keithley’s
Figure 4 embodiment. Id. The Examiner argues that the Figure 2
embodiment uses capacitors to minimize AC noise and includes a bypass
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capacitor with a value of 10μF around the DUT, which is the same
capacitance described in the Appellant’s Specification. Id. (citing Spec.
¶ 33).
In response, the Appellant argues that Kirchhoff’s circuit law “is a
simple formula for purely resistive loads, but the relationship between
voltage and current is more complex when dealing with reactive loads, such
as the reactive load shown in Keithley Fig. 2.” Reply Br. 2–3. The Appellant
argues that Keithley’s voltage source 230X suffers from oscillations when
used with a high reactive load, and, therefore, Keithley is directed to
“provid[ing] methods for stabilizing the load circuit.” Id. at 3 (quoting
Keithley p. 1, col. 1). According to the Appellant, “[a]s one of ordinary skill
in the art would understand from Keithley, because the 230X is a voltage
source and not a current source, these oscillations are caused by the
impedance of the cable and the impedance of the DUT interacting to affect
the feedback control loop of the voltage source 230X.” Id. (citing Keithley p.
2, col. 1). As to the Examiner’s contention that Keithley does not teach
against using a capacitor with a value of 10μF, the Appellant cites Keithley
page 3, column 1, as evidence that Keithley teaches “eliminating any
capacitors in parallel with the DUT.” Id. at 4.
The Appellant’s arguments are persuasive of error in the Examiner’s
conclusion of obviousness. More specifically, the Appellant has persuaded
us that the evidence fails to support the Examiner’s findings that Keithley
discloses or suggests a VCCS and a capacitor as claimed.
Keithley discloses that “[c]ertain high reactance load conditions, such
as long wire runs and capacitive loads with low equivalent series resistance
(ESR), can cause the power supply output to begin oscillating.” Keithley p.
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1, col. 1. Similarly, the background section of the Specification discloses
that prior art attempts to solve the need for a fast transient response power
supply that has stable voltage in response to fast edge, high current pulses
from a DUT “generally include long inductive cables that cause a demand
for high bandwidth of the power supply but also cause stability problems
due to the inductance of the cables reacting with the capacitance of the
DUT.” Spec. ¶ 2. Keithley “describe[s] the various load circuit conditions
that can cause oscillation and provide[s] methods for stabilizing the load
circuit.” Keithley p. 1, col. 1. More specifically, Keithley discloses the
following four methods to ensure a stable load circuit:
1. Decreasing Lcable: Using good wiring techniques and low
impedance cable
2. Decreasing CTotal: Eliminating unnecessary capacitors,
typically on the test fixture
3. Increasing RCable: Adding resistance to the load circuit
4. Adding a compensation network to the load circuit.
Id. at p. 2, col. 1. Keithley discloses that a “way to lower cable inductance is
to keep the cable as short as possible. . . . [R]outing the cabling as directly as
possible to keep the cable length as short as possible helps ensure system
stability.” Id. at p. 3, col. 1. Keithley further discloses that “[w]herever
possible, eliminate any capacitors in parallel with the DUT. . . . Eliminating
capacitors reduces the total capacitance in the load circuit, so removing a
parallel capacitor at the DUT will improve the load circuit’s performance.”
Id. By contrast, the Specification discloses that
[a] power supply in accordance with the disclosed
technology is generally designed so that neither the transient
response thereof nor its stability [is] affected by the cable or the
load to which the cable is connected. Such a power supply
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generally consists of a high-bandwidth voltage-controlled-
current-source for sending power over the load cables to the
DUT. The stability and transient response may be set by the
current sources gain, gm, and an external capacitor provided
with the power supply and located close to the DUT, e.g., at the
end of the cable.
Spec. ¶ 21.
In sum, for the reasons discussed in the Appeal and Reply Briefs, we
are persuaded that the Examiner’s conclusion of obviousness as to claim 1 is
not supported by a preponderance of the evidence. Because the remaining
claims depend from claim 1, and the Examiner has not identified teachings
in van Ettinger or Hashimoto that cure the above noted deficiencies in
Keithley, we reverse all three grounds of rejection.
CONCLUSION
Claims
Rejected
35 U.S.C. § Reference(s)/Basis Affirmed Reversed
1, 3, 6 103 Keithley 1, 3, 6
4, 7–10 103 Keithley,
van Ettinger
4, 7–10
11, 12 103 Keithley, Hashimoto 11, 12
Overall
Outcome
1, 3, 4, 6–
12

REVERSED