U.S. patent application number 16/377180 was filed with the patent office on 2020-04-02 for device for electric and magnetic measurements.
The applicant listed for this patent is SKYWORKS SOLUTIONS, INC.. Invention is credited to Dinhphuoc Vu HOANG, Guohao ZHANG.
Application Number | 20200103448 16/377180 |
Document ID | / |
Family ID | 1000004509213 |
Filed Date | 2020-04-02 |
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United States Patent
Application |
20200103448 |
Kind Code |
A1 |
HOANG; Dinhphuoc Vu ; et
al. |
April 2, 2020 |
DEVICE FOR ELECTRIC AND MAGNETIC MEASUREMENTS
Abstract
Device for electric and magnetic measurements. In some
embodiments, an electrical probe can be configured to include an
unshielded inner conductor at an end of a coaxial assembly to allow
an electrical field to induce differential-mode currents in the
coaxial assembly. In some embodiments, a magnetic probe can be
configured to include a loop connected to inner and outer
conductors of a coaxial assembly to induce a common mode current by
a change in magnetic field flux through the loop. In some
implementations, such probes can be utilized to obtain near-field
measurements to facilitate applications such as electromagnetic
(EM) shielding designs.
Inventors: |
HOANG; Dinhphuoc Vu;
(Anaheim, CA) ; ZHANG; Guohao; (Nanjing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SKYWORKS SOLUTIONS, INC. |
Woburn |
MA |
US |
|
|
Family ID: |
1000004509213 |
Appl. No.: |
16/377180 |
Filed: |
April 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16056399 |
Aug 6, 2018 |
10254324 |
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16377180 |
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14020796 |
Sep 7, 2013 |
10041987 |
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16056399 |
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61698615 |
Sep 8, 2012 |
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61698617 |
Sep 8, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 27/04 20130101;
G01R 29/10 20130101; G01R 29/0821 20130101; G01R 31/002 20130101;
G01R 1/07 20130101; G01R 29/0871 20130101; G01R 31/001 20130101;
G01R 27/32 20130101; G01R 29/0878 20130101; G01R 27/02
20130101 |
International
Class: |
G01R 29/08 20060101
G01R029/08; G01R 27/32 20060101 G01R027/32; G01R 31/00 20060101
G01R031/00; G01R 1/07 20060101 G01R001/07; G01R 29/10 20060101
G01R029/10 |
Claims
1. A probe for sensing an electromagnetic (EM) field proximate a
radio-frequency (RF) device having lateral dimensions X and Y, the
probe comprising: a coaxial assembly having a proximal end and a
distal end, the coaxial assembly including an inner conductor and
an outer conductive shield between the proximal and distal ends;
and a sensing element implemented at the distal end of the coaxial
assembly, the sensing element configured to measure a field
strength of the EM field, the sensing element having a dimension
less than the lesser of the lateral dimensions X and Y to thereby
allow a plurality of localized measurements of the EM field
strengths associated with different locations of the RF device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/056,399, filed Aug. 6, 2018 and entitled,
"DEVICE FOR ELECTRIC AND MAGNETIC MEASUREMENTS," which is a
continuation of U.S. patent application Ser. No. 14/020,796, filed
Sep. 7, 2013 and entitled "SYSTEMS, DEVICES AND METHODS RELATED TO
NEAR-FIELD ELECTRIC AND MAGNETIC PROBES," which claims priority to
U.S. Provisional Application Nos. 61/698,615, filed Sep. 8, 2012
and entitled "SYSTEMS, DEVICES AND METHODS RELATED TO NEAR-FIELD
ELECTRIC AND MAGNETIC PROBES," and 61/698,617, filed Sep. 8, 2012
and entitled "SYSTEMS AND METHODS RELATED TO NEAR-FIELD
ELECTROMAGNETIC SCANNERS," each of which is expressly incorporated
by reference herein in its entirety.
BACKGROUND
Field
[0002] The present disclosure generally relates to characterization
of electromagnetic (EM) fields associated with radio-frequency (RF)
modules.
Description of the Related Art
[0003] An electromagnetic (EM) field can be generated from or have
an undesirable effect on a region of a radio-frequency (RF) device
such as an RF module. Such an EM interference (EMI) can degrade the
performance of wireless devices that use such an RF module. Some RF
modules can be provided with EM shields to mitigate such
performance issues associated with EMI.
SUMMARY
[0004] According to a number of implementations, the present
disclosure relates to a probe for sensing an electromagnetic (EM)
field proximate a radio-frequency (RF) device having lateral
dimensions X and Y. The probe includes a coaxial assembly having a
proximal end and a distal end. The coaxial assembly includes an
inner conductor and an outer conductive shield between the proximal
and distal ends. The probe further includes a sensing element
implemented at the distal end of the coaxial assembly. The sensing
element is configured to measure a field strength of the EM field.
The sensing element has a dimension less than the lesser of the
lateral dimensions X and Y to thereby allow a plurality of
localized measurements of the EM field strengths associated with
different locations of the RF device.
[0005] In some embodiments, the probe can further include a coaxial
connector implemented at the proximal end of the coaxial assembly.
The outer conductive shield can be connected to a ground during the
localized measurements.
[0006] In some embodiments, the sensing element can be configured
to sense the field strength of an electrical component of the EM
field. The sensing element can include an unshielded extension of
the inner conductor beyond the outer conductive shield at the
distal end of the coaxial assembly. The unshielded extension can be
configured so that an electric field acting on the unshielded
extension results in opposite differential-mode currents flowing in
the inner conductor and the outer conductive shield.
[0007] In some embodiments, the sensing element can be configured
to sense the field strength of a magnetic component of the EM
field. The sensing element can include a loop having a first end
connected to a distal end of the inner conductor and a second end
connected to a distal end of the outer conductive shield. The loop
can be configured so that a change in magnetic field flux through
the loop induces a detectable common mode current. The loop can
have at least one turn, a rectangular shape, or a circular shape.
For the circular shape example, the circular loop can have a
diameter that is 1 mm or less.
[0008] In some embodiments, the coaxial assembly can have a
characteristic impedance of approximately 50 ohms. In some
embodiments, the field strength can include a near-field strength
associated with the EM field strength present at a separation
distance from a surface of the RF device. The separation distance
can be approximately 1 mm or less.
[0009] In a number of teachings, the present disclosure relates to
a method for testing a radio-frequency (RF) device. The method
includes operating the RF device to generate an electromagnetic
(EM) emission. The method further includes positioning a sensing
element relative to the RF device to allow a measurement of the EM
emission. The measure further includes measuring a field strength
through the positioned sensing element. The measured field strength
is representative of a field distribution over a selected area that
is smaller than an overall lateral area of the RF device.
[0010] In some embodiments, the RF device can be a power amplifier
module. In some embodiments, the selected area can be less than the
overall lateral area by a factor of at least 10. The selected area
can be less than or equal to approximately 1 mm.sup.2.
[0011] In some embodiments, the field strength can include an
electric field strength. In some embodiments, the field strength
can include a magnetic field strength. In some embodiments, the
field strength can include a near-field strength associated with
the EM field strength present at a separation distance from a
surface of the RF device, with the separation distance being
approximately 1 mm or less.
[0012] In some implementations, the present disclosure relates to a
system for testing a radio-frequency (RF) device. The system
includes a control system configured to allow operation of the RF
device. The system further includes a signal generator configured
to provide an RF signal to the RF device so that the operating RF
device generates an electromagnetic (EM) emission. The system
further includes a measurement system that includes a probe
configured to measure a field strength representative of a field
distribution over a selected area that is smaller than an overall
lateral area of the RF device.
[0013] According to some implementations, the present disclosure
relates to a system for scanning for electromagnetic (EM) emission.
The system includes a fixture system configured to hold a device
under test (DUT) and provide electrical connections for the DUT.
The system further includes an operating system connected to the
fixture system and configured to allow operation of the DUT. The
system further includes a measurement system configured to obtain
field strength measurements representative of a field distribution
over a plurality of selected areas of the DUT during the operation
of the DUT, with each of the selected areas being smaller than an
overall lateral area of the DUT.
[0014] In some embodiments, the operating system can include a
radio-frequency (RF) source configured to provide an RF signal to
the DUT. The field distribution can be a result of the operation of
the DUT with the RF signal. The operating system can further
include a power source configured to provide power to the DUT. The
operating system can further include a controller configured to
provide control signals to the DUT.
[0015] In some embodiments, the fixture system can include a
printed circuit board (PCB) configured to hold the DUT and provide
the electrical connections. The fixture system can further include
a movable chuck table configured to facilitate the measurement of
the field strength at each of the plurality of selected areas. The
movable chuck table can be configured to move the PCB along lateral
directions X and Y in increments .DELTA.X and .DELTA.Y.
[0016] In some embodiments, the measurement system can include a
magnetic field probe configured to sense a magnetic field strength.
The magnetic field probe can include a loop having a first end
connected to a distal end of an inner conductor and a second end
connected to a distal end of an outer conductive shield. The inner
conductor and the outer conductive shield can be arranged in a
coaxial configuration, with the loop being configured so that a
change in magnetic field flux through the loop induces a detectable
common mode current. The loop can have a circular shape with a
diameter that is 1 mm or less. The coaxial configuration can have a
characteristic impedance of approximately 50 ohms.
[0017] In some embodiments, the measurement system can further
include a pre-amplifier configured to amplify a signal
representative of the common mode current. The measurement system
can further include a spectrum analyzer configured to process the
amplified signal. The measurement system can further include a
processor configured to control the measurement system.
[0018] In some embodiments, the field distribution can include a
near-field strength distribution associated with the field strength
measurements obtained at a separation distance from a surface of
the RF device. The separation distance can be approximately 1 mm or
less.
[0019] In a number of implementations, the present disclosure
relates to a method for scanning for electromagnetic (EM) emission.
The method includes holding a device under test (DUT). The method
further includes performing an operation associated with the DUT.
The method further includes obtaining field strength measurements
representative of a field distribution over a plurality of selected
areas of the DUT during the operation of the DUT, with each of the
selected areas being smaller than an overall lateral area of the
DUT.
[0020] In some embodiments, at least the measuring of the field
strength can be performed automatically under control of a
processor. In some embodiments, each of the selected areas can be
smaller than the overall area of the DUT by a factor of at least
10.
[0021] In some embodiments, the DUT can be a power amplifier
module. The power amplifier module can include an electromagnetic
shield. Dimensions of each of the selected areas can be selected so
that removal of a single unit of the electromagnetic shield is
detectable by the measured field strength. The single unit can
include a shielding wirebond.
[0022] For purposes of summarizing the disclosure, certain aspects,
advantages and novel features of the inventions have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the invention may be embodied or
carried out in a manner that achieves or optimizes one advantage or
group of advantages as taught herein without necessarily achieving
other advantages as may be taught or suggested herein.
[0023] The present disclosure relates to U.S. patent application
Ser. No. 14/020,797, titled "SYSTEMS AND METHODS RELATED TO
NEAR-FIELD ELECTROMAGNETIC SCANNERS," filed on even date herewith
and hereby incorporated by reference herein in its entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 schematically depicts a radio-frequency (RF) module,
where electromagnetic (EM) field into and/or out of the module can
be characterized as described herein.
[0025] FIG. 2 shows an example of an RF shield that can be included
in the module of FIG. 1.
[0026] FIG. 3 shows that in some implementations, the module of
FIG. 1 can be configured to provide functionalities associated with
two or more operating modes.
[0027] FIG. 4 shows an example of how magnetic field can be
detected by an inductive magnetic probe having a current-inducing
loop.
[0028] FIG. 5 shows that if a current-inducing loop of a magnetic
probe is too large relative an RF module being tested, localized EM
field characterization of the RF module is difficult or
impossible.
[0029] FIG. 6 shows that in some implementations, a probe having
one or more features described herein can be configured to allow
localized characterization of an RF module being tested.
[0030] FIG. 7 schematically depicts an electric probe that can
function as the probe of FIG. 6.
[0031] FIG. 8 schematically depicts a magnetic probe that can
function as the probe of FIG. 6.
[0032] FIG. 9 shows examples of the magnetic probe of FIG. 8.
[0033] FIGS. 10A and 10B show an example near-field measurement
configuration that can facilitate the localized field
characterization of FIG. 6.
[0034] FIG. 11 shows an example measurement apparatus that can
facilitate the near-field measurement configuration of FIGS. 10A
and 10B.
[0035] FIG. 12 shows an example measurement system having the
measurement apparatus of FIG. 11.
[0036] FIG. 13 schematically depicts the measurement system of FIG.
12.
[0037] FIG. 14 schematically depicts a more specific example of the
system of FIG. 13.
[0038] FIGS. 15A-15G show an example RF module and field
measurements associated with various operating conditions, such
that the RF module can be characterized in a localized manner.
[0039] FIGS. 16A-16F show another example RF module and field
measurements associated with various operating conditions, such
that the RF module can be characterized in a localized manner.
[0040] FIG. 17 shows an example process that can be performed by
one or more components of the measurement system of FIG. 13.
[0041] FIG. 18 shows another example process that can be performed
by one or more components of the measurement system of FIG. 13.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0042] The headings provided herein, if any, are for convenience
only and do not necessarily affect the scope or meaning of the
claimed invention.
[0043] FIGS. 1-3 show examples of radio-frequency (RF) modules that
can be characterized effectively by devices, systems, and/or method
as described herein. In some embodiments, such RF modules can be
packaged modules. Although described in the context of such RF
modules, it will be understood that one or more features described
herein can also be utilized in other non-modular RF applications,
including, for example, RF circuits that are not packaged.
[0044] FIG. 1 shows that an RF module 75 can include an RF
component 99. As described herein, such a component can include,
for example, a die having one or more integrated circuits, a
passive component (such as a surface-mount device (SMD)), a
connection feature, or some combination thereof. Such a component
can emit an electromagnetic (EM) field (depicted as an arrow 102)
during operation, and/or can be susceptible to an EM field 104
generated elsewhere. In some situations, it is desirable to keep
the RF component 99 isolated to prevent the EM field 102 from
leaving the module 75 and/or to prevent the EM field 104 from
entering the module 75.
[0045] FIG. 1 further shows that in some embodiments, a module 75
can include an RF shield configured to provide the foregoing
isolating functionality. Non-limiting examples of such an RF shield
are described in International Publication No. WO 2010/014103
(International Application No. PCT/US2008/071832, filed on Jul. 31,
2008, titled "SEMICONDUCTOR PACKAGE WITH INTEGRATED INTERFERENCE
SHIELDING AND METHOD OF MANUFACTURE THEREOF") and U.S. Publication
No. US 2007/0241440 (U.S. application Ser. No. 11/499,285, filed on
Aug. 4, 2006, titled "OVERMOLDED SEMICONDUCTOR PACKAGE WITH A
WIREBOND CAGE FOR EMI SHIELDING"), each of which is incorporated
herein by reference in its entirety. Although various modules are
described herein in the context of shielding-wirebonds, it will be
understood that one or more features of the present disclosure can
also be utilized in other types of shielding configurations.
[0046] In the example context of shielding-wirebond configuration,
FIG. 2 shows a sectional side view of a module 75 having a
plurality of shielding-wirebonds 51 disposed near the periphery of
the module 75 (e.g., see FIG. 3). Such shielding-wirebonds 51 are
shown to be formed on a packaging substrate 20 (e.g., a laminate
substrate) and encapsulated by an overmold structure 59. Upper
portions of the shielding-wirebonds 51 are shown to be exposed on
an upper surface of the overmold structure 59, so as to be in
electrical contact with a conductive layer 71 (e.g., a layer of
sprayed-on metallic paint). Lower portions of the
shielding-wirebonds 51 are shown to be electrically connected to a
ground plane 30, so that a combination of the ground plane 30, the
shielding wirebonds 51, and the conductive layer 71 forms an
RF-isolated volume on the packaging substrate 20.
[0047] Such an RF-isolated volume can provide RF-isolation for one
or more RF components such as a die 36 and an SMD 43. The example
die 36 is depicted as being connected to other parts of the module
75 by connection-wirebonds 49. Such connections can facilitate
passage of power and signals to and/or from the die 36 through, for
example, I/O connection pads 28. External grounding of the ground
plane 30 (and other grounds in the module 75) can be facilitated by
the grounding pads 29.
[0048] FIG. 3 shows that in some implementations, the foregoing
examples of RF components can include circuits configured to
provide RF functionalities associated with wireless devices. For
example, a power amplifier (PA) circuitry can be implemented in a
module 75 having shielding-wirebonds 51. In some embodiments, such
a PA circuitry can be configured to operate at different bands
and/or modes. For example, a circuit associated with a high-band
can reside generally in one area, and a circuit associated with a
low-band can reside generally in another area. Although described
in the example context of PA circuits, it will be understood that
one or more features of the present disclosure can also be applied
to other types RF circuits.
[0049] As described herein, being able to characterize EM emissions
in a localized manner can be important for a number of
applications. For example, locations of such field emissions can be
identified. Based on such locations, modifications such as the
circuit itself, position of the circuit within the module, and/or
position of the module relative to other components (e.g., on a
circuit board of a wireless device) can be effectuated. In another
example, a shielding configuration can be modified or designed
based on knowledge of such localized characterization of EM
emissions.
[0050] FIG. 4 shows an example of how EM emissions can be detected
by sensing magnetic fields associated with such EM emissions. Based
on Faraday's law of induction applied to a conductive loop 110,
oscillation of magnetic field 106 flux through the loop 110 induces
a current 108 in the loop 110. If two ends of the loop 110 are
electrically connected to their respective terminals, an induced
voltage amplitude Vg between the two terminals can be represented
as
V.sub.g=Bn.omega.A cos .theta., (1)
where B is the magnetic field amplitude, n is the number of loop
turns, co is the angular frequency associated with the oscillation,
A is the loop area, and 0 is the angle between the magnetic field
and the normal direction of the loop area (assuming a generally
uniform magnetic field direction).
[0051] FIG. 5 shows that if an EM sensing element 110 (such as the
loop of FIG. 4) is too large relative a device under test (DUT) 75,
then localized characterization of the DUT by the sensing element
110 can become difficult or impossible. In a given position of the
sensing element 110 relative to the DUT 75, one generally cannot
determine where on the DUT an EM field is emitted due to the
sensing element being too large.
[0052] It is possible to move either or both of the DUT 75 and the
sensing element 110 so that relative displacements are smaller than
a dimension of the DUT 75. Even with such configurations,
measurements will generally yield only average values that likely
do not provide localized information.
[0053] Disclosed herein are examples of devices and measurements
related to a miniature near-field probe capable of very fine
resolution that allows high precision localized measurement of EM
field emission from a small DUT such as an RF module. In some
situations, such localized measurements can allow EM emission
detection even on a single pin of an RF module. Although such
near-field probes are described herein in the example context of
characterizing of RF modules, it will be understood that one or
more features described herein can also be utilized in other
applications. For example, near-field probes having one or more
features described herein can also be used to sniff emissions from
anywhere on a circuit board (e.g., a phone board) level. Also,
although various examples are described in the context of emissions
from a given location, it will be understood that one or more
features of the present disclosure can also be utilized for
localized characterization of EM fields entering a given location,
whether or not such a location includes an EM field emitter. In
such a situation, an RF component at such a location may not emit
significant amount of EM field, but it may be susceptible to EM
fields that are generated elsewhere.
[0054] In the context of an RF module, FIG. 6 shows an example
measurement configuration 120, where a near-field sensing element
130 is dimensioned to allow localized EM emission characterization
of a module 75. The example sensing element 130 (e.g., a circular
loop) is shown to have a representative dimension "d" (e.g.,
diameter of the circular loop) that allows characterization of
localize regions (e.g., squares) 122 having dimensions
"a".times."b." In some embodiments, dimensions associated with such
localized regions can be sufficiently small so as to be capable of
measurements that are affected by one shielding wirebond 51 (having
a lateral dimension of "c"). Such effects associated with a single
shielding wirebond can include, for example, presence or absence of
the shielding wirebond.
[0055] In some implementations, the localized EM emission
characterization can be sufficiently sensitive to measure effects
resulting from modification of shielding configurations associated
with one or more shielding wirebonds. Other measurement situations
can also benefit from near-field EM measurement techniques
described herein.
[0056] In some implementations, a miniature near-field probe that
can facilitate the foregoing measurement capability and having
features as described herein can be one or combination of two
types. The first type can be configured to include a shaped
magnetic loop (e.g., circular or rectangular) having a dimension
(e.g., diameter or side-dimension of a rectangle) that is, for
example, 1 mm or less. Other dimensions that are larger than the
example 1 mm dimension can also be utilized. Such a loop can be
configured to provide high sensitivity to magnetic fields.
[0057] The second type can include an electric field probe (also
referred to herein as an E-probe) having an exposed conductive tip
or needle at the end. As described herein, such a probe can be
configured for detection of electric fields.
[0058] FIGS. 7 and 8 show examples of an electric field probe 140
and a magnetic field probe 150 that can be configured to achieve
the foregoing near-field measurements for localized
characterization of RF modules. In some embodiments, each of the
electric and magnetic field probes 140 and 150 can include a length
of coaxial portion (e.g., a hard coaxial cable) having an inner
conductor surrounded by an outer conducting shield. An inner
insulator (e.g., a dielectric material) can be disposed between the
inner conductor and the outer conducting shield. An outer
insulating sheath (e.g., plastic sheath) can be provided to cover
the conducting shield.
[0059] During operation, the outer conducting shield can be
connected to a ground. In some implementations, such a ground can
be connected to a DUT ground or an equipment (e.g., spectrum
analyzer) ground. For the various examples described herein, the
ground of the outer conducting shield is connected to the equipment
ground.
[0060] In some embodiments, the coaxial probe can have a
characteristic impedance (e.g., 50 ohms) generally compatible with
an impedance characteristic of an RF circuit associated with the
DUT. For connectivity, a connector such as an SMA connector can be
provided on one end of the coaxial portion. The other end of the
coaxial portion can be the sensing end, and can be configured as
follows, depending on whether the coaxial probe is used as an
electric or magnetic field probe.
[0061] As shown in FIG. 7, the sensing end 142 of the coaxial probe
140 can be configured so that the distal end of the inner connector
is exposed and not shielded by the outer conducting shield. The
exposed distal end of the inner connector may or may not extend
beyond the distal end of the outer conducting shield. In some
embodiments, the distal end of the exposed inner conductor can be
left unconnected. Such a configuration of the sensing end 142 can
allow sensing of electric fields while being generally insensitive
to magnetic fields. An electric field sensed by the foregoing
example configuration can result in a differential-mode current
flowing in one direction along the inner conductor (e.g., away from
the distal end of the probe 140), and a balanced current flowing in
the opposite direction along the outer conducting shield (e.g.,
towards the distal end of the probe 140).
[0062] As shown in FIG. 8, the sensing end 152 of the coaxial probe
150 can be formed by exposing a length of the inner conductor and
forming a loop with the exposed inner conductor. The end of the
exposed inner conductor can be connected (e.g., soldered) to the
outer conducting shield. In some embodiments, such a loop formed by
the exposed inner conductor can have a selected size and/or shape.
For example, a generally circular shaped loop having a diameter can
be formed. Such a diameter can be selected to be, for example,
approximately 1 mm to facilitate magnetic field measurements
associated with EM emissions at an example range of approximately
0.8 to 3.0 GHz. At other frequencies and/or measurement settings,
other loop dimensions larger or smaller than 1 mm can be utilized.
For example, at a higher frequency, a smaller loop diameter can be
utilized to increase the sensitivity of the sensing end 152 and
provide finer resolution. As described herein, variations in
magnetic field flux can induce an unbalanced flow of a common-mode
current in the loop, and such a current can be detected through the
inner conductor.
[0063] As described in reference to FIG. 7, the example electric
field probe 140 demonstrates a differential mode current phenomenon
where, for example, a current flows from node W to node X (depicted
as a solid-line arrow), and a balanced current having generally the
same magnitude but opposite direction flows from node Z to node Y
(depicted as a dashed-line arrow). Therefore, the two
opposite-direction currents substantially cancel out, thereby not
being sensitive or suitable for magnetic field measurements.
However, an electrical potential exists between the inner conductor
at the tip and the outer conducting shield. Such an electric
potential can be relatively small in some EM measurement
situations. Accordingly, such a probe can be used for electric
field measurements, but with less sensitivity due to the foregoing
low measurable potential value.
[0064] As described in reference to FIG. 8, the loop configuration
of the sensing end 152 can yield sensitivities to both electric and
magnetic fields. However, the magnetic field can dominate because
the loop creates an unbalanced current flow (also referred to
herein as a common mode current). Such a current resulting from
sensing of magnetic fields and flowing around the loop generally
does not get canceled. Accordingly, such a probe can be utilized
for magnetic field measurements.
[0065] FIG. 9 shows two examples of the magnetic field probe 150 as
described in reference to FIG. 8. As shown, the probe can be
configured with different design parameters. For example, different
coaxial dimensions (length and/or sectional dimensions) can be
implemented. In another example, the sensing end loop size and/or
shape can be selected for different measurement applications.
[0066] FIGS. 10A and 10B schematically depict side and plan view of
a near-field scanning configuration 200 that utilizes a magnetic
probe 150 described in reference to FIGS. 8 and 9. In the example,
a sensing end 152 of the magnetic probe 150 is shown to be
positioned over a DUT (e.g., an RF module) 75 at a coordinate (X,
Y, Z), with X and Y defining lateral directions on the DUT 75, and
Z defining a vertical direction relative to the DUT 75. In some
implementations, the value of Z (height above the DUT 75) can be
held substantially uniform (e.g., at approximately 1 mm) as
measurements are made at different X and Y locations.
[0067] In the example shown in FIG. 10A, the DUT 75 is depicted as
being positioned on a platform 202 such as a printed circuit board
(PCB) during the near-field scan. FIG. 11 shows an example of a
test fixture 204 that includes a PCB 202 that can act as the
foregoing testing scanning platform. The PCB 202 is shown to be
configured to receive a DUT 75 and provide connections for
operation of the DUT during a scan with a near-field probe such as
a magnetic field probe 150.
[0068] In some implementations, the foregoing test fixture 204 can
be part of a test system 300, examples of which are shown in FIGS.
12-14. In FIG. 12, the test fixture 204 is shown to be mounted on a
movable chuck table 302 configured to provide lateral motion of the
DUT relative to the probe 150. The probe 150 is shown to be mounted
to a probe-holding apparatus that allows, for example, adjustment
of the height of the probe 150 and independent lateral motion of
the probe 150.
[0069] FIG. 12 further shows that the test system 300 can include a
plurality of test equipment 304 configured to, for example, operate
the DUT and process measured signals from the probe 150. For
example, FIG. 13 schematically shows that the DUT 75 can be
operated by being provided with RF signals from a signal generator
314. The signal generator 314 (e.g., Agilent 8648C) can be under
the control of, and/or be monitored by a controller 316. In the
example shown, the controller 316 can be based on a computing
device having a processor. During operation of the DUT (e.g., the
PA modules described in reference to FIGS. 15 and 16) and EM
measurements, the output of the PA can be terminated by 50 ohms and
be attenuated by 30 dB.
[0070] In some implementations, and as shown in FIGS. 13 and 14,
signals obtained from the probe 150 can be amplified by a
pre-amplifier 310 (e.g., approximately 20 dB gain), and be
processed further by a spectrum analyzer 312. Signals processed in
the foregoing example can be provided to the controller 316 for
further analysis and/or storage.
[0071] In some implementations, and as shown in FIGS. 13 and 14,
the DUT 75 can be moved during the scan under the control of the
controller 316. Such controlled motion of the DUT 75 can be
facilitated by a moving chuck 324 of a chuck table 322 (e.g.,
Cascade model 10000). Such a chuck table can be configured to
provide different sized steps in lateral movements of the DUT 75,
including those associated with example scans as described
herein.
[0072] In some implementations, and as shown in FIG. 14, various
signals associated with controls and measurements can be
facilitated by an interface such as a general purpose interface bus
(GPIB) depicted as 330. Further, the controller 316 can be
configured to be in communication with a computer-readable medium
(CRM) 332 for storing, for example, measured data and/or various
computer-executable instructions for performing and/or inducing
various functionalities associated with the controller 316. In some
implementations, such computer-executable instructions can be
stored in a non-transitory manner.
[0073] FIGS. 15 and 16 show examples of magnetic field measurements
that show localized EM emissions for two example RF modules. FIG.
15A shows an example PA module configured to operate in GSM bands
of 824 MHz ("lowband" or "LB") and 1710 MHz ("highband" or "HB").
The example packaged module has a 6.times.8 mm form factor, and the
localized characterization capability of near-field scanning as
described herein allows the module's area to be divided into, for
example, 1 mm squares.
[0074] To perform example magnetic field measurements shown in
FIGS. 15B and 15C for such 1 mm squares, a fine resolution magnetic
loop sensor having an approximately 1 mm diameter was positioned
approximately 1 mm (Z direction) above the PA module. The PA module
was moved (by the moving chuck 324 in FIG. 14) in approximately 0.5
mm steps in X and Y directions; and a total of 221 data points were
collected for each band operation.
[0075] For the measurements shown in FIGS. 15B and 15C, the PA
module is not shielded. Thus, during the lowband operation (FIG.
15B), the region at or near the lowband circuit is shown to have
high magnetic field values expressed in power unit (e.g., a peak at
a -2 dBm level). Similarly, during the highband operation (FIG.
15C), the region at or near the highband circuit is shown to have
even higher magnetic field values expressed in power unit (e.g., a
peak at a 0 dBm level). If at least -20 dBm suppression of EM
emission is desired (as measured by magnetic field strength), then
one can see that the unshielded configuration shown in FIGS. 15B
and 15C fails such a requirement.
[0076] The measurement results shown in FIGS. 15D and 15E are for
the same PA module of FIGS. 15B and 15C, but with a generally
ineffective shielding configuration. During the lowband operation
(FIG. 15D), a region at the upper right corner is shown to have a
magnetic field value (expressed in power unit) of -18 dBm that is
higher than the example desired -20 dBm threshold. Similarly,
during the highband operation (FIG. 15E), various locations about
the highband circuit are shown to have magnetic field values
(expressed in power unit) of -14 dBm, -18 dBm, and -18 dBm that are
also higher than the desired -20 dBm threshold. Thus, a shielding
configuration that allows such EM emissions can be considered to be
ineffective if compared to the example -20 dBm threshold
standard.
[0077] The measurement results shown in FIGS. 15F and 15G are for
the same PA module of FIGS. 15B and 15C, but with a more effective
shielding configuration. During the lowband operation (FIG. 15F), a
region at the upper right corner is shown to have a magnetic field
value (expressed in power unit) of -23 dBm that is lower than the
example desired -20 dBm threshold. Similarly, during the highband
operation (FIG. 15E), various locations about the highband circuit
are shown to have magnetic field values (expressed in power unit)
of -24 dBm, -22 dBm, and -25 dBm that are also lower than the
desired -20 dBm threshold. Thus, a shielding configuration that
allows such EM emissions can be considered to be effective if
compared to the example -20 dBm threshold standard.
[0078] FIGS. 16A-16F show magnetic field measurement results using
another example PA module. The example PA module is configured to
operate in GMSK bands of 824 MHz ("lowband" or "LB") and 1710 MHz
("highband" or "HB"). During operation, the example PA is provided
with a 5 dBm input to yield an output power of approximately 34
dBm. The example PA module has a 6.times.8 mm form factor, and the
measurement configuration is similar to that described in reference
to FIG. 15.
[0079] FIG. 16A shows the example GMSK PA module with its lowband
operating through a lowband PA die and a corresponding matching
circuit. The RF input and output for the lowband amplifier are also
shown. FIG. 16B shows measurement results for the unshielded PA
module operating in the lowband configuration of FIG. 16A. FIG. 16C
shows the same measurement results in a 3-dimensional contour plot.
One can see that the contour includes a peak region generally above
the lowband PA/matching area with a magnetic field strength
(expressed in power unit) of about 3 dBm. One can see that without
shielding, the EM emission is generally spread over a relatively
wide area about the lowband PA/matching area.
[0080] FIG. 16D shows the example GMSK PA module with its highband
operating through a highband PA die and a corresponding matching
circuit. The RF input and output for the highband amplifier are
also shown. FIG. 16E shows measurement results for the unshielded
PA module operating in the highband configuration of FIG. 16D. FIG.
16F shows the same measurement results in a 3-dimensional contour
plot. One can see that the contour includes a peak region generally
above the highband PA/matching area with a magnetic field strength
(expressed in power unit) of about 0 dBm. One can see that without
shielding, the EM emission is generally spread over a relatively
wide area about the highband PA/matching area.
[0081] Similar to the examples described in reference to FIGS.
15A-15G, one or more shielding designs can be implemented and
tested by a test system (e.g., 300 in FIGS. 12-14) having one or
more features as described herein. Such testing can reveal how
effective a given shielding design is relative to some selected
threshold (e.g., -20 dBm threshold). Further, one can see that the
localized field-characterization capability as described herein can
allow development of RF shielding configurations that are location
dependent on a given RF module. For example, some location of the
RF module can be provided with more shielding, and/or another
location can be provided with less shielding.
[0082] FIGS. 17 and 18 show examples of processes that can be
implemented to perform measurements as described herein. FIG. 17
shows a process 400 that can be implemented to configure a DUT for
such measurements. FIG. 18 shows a process 410 that can be
implemented to obtain near-field measurements so as to allow
localized characterization of the DUT.
[0083] In FIG. 17, the example process 400 can include a block 402
where power and control signals are provided to allow operation of
a DUT. In block 404, an RF signal can be provided to the DUT. In
some implementations, an output (e.g., an amplified RF signal from
a PA) of the DUT can be configured so as to provide a more
realistic operating condition. For example, appropriate matching
network for an output of a PA can allow the DUT to behave closer to
an actual operating condition.
[0084] In FIG. 18, the example process 410 can include a block 412
where one or more movements can be performed to position a
near-field probe at a desired location relative to a DUT. Such
movements can be achieved by moving the probe, moving the DUT, or
some combination thereof. In block 414, one or more field
measurements can be obtained at the desired location. Such
measurements can include magnetic field measurement, electric field
measurement, or some combination thereof. In block 416, signals
obtained from the one or more measurements can be processed. Such
processing of signals can include, for example, pre-amplification
and spectrum analysis.
[0085] In a decision block 418, the process 410 can determine
whether the scan of the DUT is complete. If the answer is "No," the
process 410 can loop back to block 412 for further positioning and
measurements. If the answer is "Yes," the process 410 in block 420
can generate measurement results to facilitate, for example,
identification of shielding flaws, shielding design changes, new
shielding designs, etc.
[0086] One or more features associated with near-field probes and
related measurement systems and methods as described herein can be
utilized to address a number of challenges in RF applications. For
example, as RF device count increases with circuit board sizes
becoming smaller, EM emissions and/or interferences can have
negative impact on performance at a component level, as well as at
a system level. In another example, radiated emission can be more
severe as frequency goes higher; thus, accurate detection of such
emissions can provide important design guidelines. In yet another
example, localized field measurements can troubleshoot crosstalk
and/or undesired interference among parts of or between RF
circuits. In yet another example, localized near-field
characterization of a DUT can significantly save time and resources
when compared to far-field techniques where time and resource
consuming iterations (and in some situations, trial-and-error) may
be required.
[0087] As described herein, one or more features described herein
can allow designers to readily identify potential coupling and/or
EM interference issues at an early stage. Further, design process
can be guided by principles and concepts obtained from such EM
characterization.
[0088] In some implementations, an EM probe having one or more
features as described herein can be an effective tool for obtaining
accurate EM-related diagnosis to identify or narrow down the
possible sources of EM interference at a very specific location of
a DUT. In some implementations, such a specific location can allow
identification of an individual pin of an IC as the offending EM
interference source. Based on such identification, the underlying
problem can be solved, or if such a solution is not practical,
appropriate shielding can be provided.
[0089] A miniaturized probe having one or more features described
herein can be suitable, and in some situations crucial, for
characterizing EM emissions associated with smaller modules or even
some die-level devices. As described herein, such a probe can be
configured as a magnetic field probe with a small sensing loop
dimension. Aside from the spatial resolution, such a small probe
can provide improved response for higher frequency emissions. By
way of an example, EM emissions in a range of approximately 3 to 12
GHz can be sensed effectively by such a small probe.
[0090] In the context of the magnetic field probes as described
herein, such probes can be configured to be highly sensitive to
magnetic fields. Such probes can also be configured to deliver
highly repeatable performance.
[0091] Although various probes (e.g., electric field probe and
magnetic field probe) are described herein in the context of
sensing fields, it will be understood that such devices can be
utilized in reverse. For example, such probes can be driven
(instead of sensing) by appropriate signals to generate desirable
fields to very localized areas or volumes. Such a field can be
injected to a localized area or volume to, for example, analyze
effects of the field on specific components without subjecting
other components with the same field.
[0092] For the purpose of description, it will be understood that
"near-field" can include, for example, a region that extends from
an EM emission source by a length less than or equal to a
wavelength associated with the EM emission. Near-field as described
herein can also include such a length that is less than or equal
to, for example, 1 m, 30 cm, 10 cm, 1 cm, 3 mm, 1 mm, 500 .mu.m,
100 .mu.m, 50 .mu.m, or 10 .mu.m. For the purpose of description,
it will be understood that a "localized region" can have an area
that is less than the overall lateral area of a DUT by a factor of
at least 2, 5, 10, 16, or 48.
[0093] The present disclosure describes various features, no single
one of which is solely responsible for the benefits described
herein. It will be understood that various features described
herein may be combined, modified, or omitted, as would be apparent
to one of ordinary skill. Other combinations and sub-combinations
than those specifically described herein will be apparent to one of
ordinary skill, and are intended to form a part of this disclosure.
Various methods are described herein in connection with various
flowchart steps and/or phases. It will be understood that in many
cases, certain steps and/or phases may be combined together such
that multiple steps and/or phases shown in the flowcharts can be
performed as a single step and/or phase. Also, certain steps and/or
phases can be broken into additional sub-components to be performed
separately. In some instances, the order of the steps and/or phases
can be rearranged and certain steps and/or phases may be omitted
entirely. Also, the methods described herein are to be understood
to be open-ended, such that additional steps and/or phases to those
shown and described herein can also be performed.
[0094] Some aspects of the systems and methods described herein can
advantageously be implemented using, for example, computer
software, hardware, firmware, or any combination of computer
software, hardware, and firmware. Computer software can comprise
computer executable code stored in a computer readable medium
(e.g., non-transitory computer readable medium) that, when
executed, performs the functions described herein. In some
embodiments, computer-executable code is executed by one or more
general purpose computer processors. A skilled artisan will
appreciate, in light of this disclosure, that any feature or
function that can be implemented using software to be executed on a
general purpose computer can also be implemented using a different
combination of hardware, software, or firmware. For example, such a
module can be implemented completely in hardware using a
combination of integrated circuits. Alternatively or additionally,
such a feature or function can be implemented completely or
partially using specialized computers designed to perform the
particular functions described herein rather than by general
purpose computers.
[0095] Multiple distributed computing devices can be substituted
for any one computing device described herein. In such distributed
embodiments, the functions of the one computing device are
distributed (e.g., over a network) such that some functions are
performed on each of the distributed computing devices.
[0096] Some embodiments may be described with reference to
equations, algorithms, and/or flowchart illustrations. These
methods may be implemented using computer program instructions
executable on one or more computers. These methods may also be
implemented as computer program products either separately, or as a
component of an apparatus or system. In this regard, each equation,
algorithm, block, or step of a flowchart, and combinations thereof,
may be implemented by hardware, firmware, and/or software including
one or more computer program instructions embodied in
computer-readable program code logic. As will be appreciated, any
such computer program instructions may be loaded onto one or more
computers, including without limitation a general purpose computer
or special purpose computer, or other programmable processing
apparatus to produce a machine, such that the computer program
instructions which execute on the computer(s) or other programmable
processing device(s) implement the functions specified in the
equations, algorithms, and/or flowcharts. It will also be
understood that each equation, algorithm, and/or block in flowchart
illustrations, and combinations thereof, may be implemented by
special purpose hardware-based computer systems which perform the
specified functions or steps, or combinations of special purpose
hardware and computer-readable program code logic means.
[0097] Furthermore, computer program instructions, such as embodied
in computer-readable program code logic, may also be stored in a
computer readable memory (e.g., a non-transitory computer readable
medium) that can direct one or more computers or other programmable
processing devices to function in a particular manner, such that
the instructions stored in the computer-readable memory implement
the function(s) specified in the block(s) of the flowchart(s). The
computer program instructions may also be loaded onto one or more
computers or other programmable computing devices to cause a series
of operational steps to be performed on the one or more computers
or other programmable computing devices to produce a
computer-implemented process such that the instructions which
execute on the computer or other programmable processing apparatus
provide steps for implementing the functions specified in the
equation(s), algorithm(s), and/or block(s) of the flowchart(s).
[0098] Some or all of the methods and tasks described herein may be
performed and fully automated by a computer system. The computer
system may, in some cases, include multiple distinct computers or
computing devices (e.g., physical servers, workstations, storage
arrays, etc.) that communicate and interoperate over a network to
perform the described functions. Each such computing device
typically includes a processor (or multiple processors) that
executes program instructions or modules stored in a memory or
other non-transitory computer-readable storage medium or device.
The various functions disclosed herein may be embodied in such
program instructions, although some or all of the disclosed
functions may alternatively be implemented in application-specific
circuitry (e.g., ASICs or FPGAs) of the computer system. Where the
computer system includes multiple computing devices, these devices
may, but need not, be co-located. The results of the disclosed
methods and tasks may be persistently stored by transforming
physical storage devices, such as solid state memory chips and/or
magnetic disks, into a different state.
[0099] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense, as opposed
to an exclusive or exhaustive sense; that is to say, in the sense
of "including, but not limited to." The word "coupled", as
generally used herein, refers to two or more elements that may be
either directly connected, or connected by way of one or more
intermediate elements. Additionally, the words "herein," "above,"
"below," and words of similar import, when used in this
application, shall refer to this application as a whole and not to
any particular portions of this application. Where the context
permits, words in the above Detailed Description using the singular
or plural number may also include the plural or singular number
respectively. The word "or" in reference to a list of two or more
items, that word covers all of the following interpretations of the
word: any of the items in the list, all of the items in the list,
and any combination of the items in the list. The word "exemplary"
is used exclusively herein to mean "serving as an example,
instance, or illustration." Any implementation described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other implementations.
[0100] The disclosure is not intended to be limited to the
implementations shown herein. Various modifications to the
implementations described in this disclosure may be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other implementations without
departing from the spirit or scope of this disclosure. The
teachings of the invention provided herein can be applied to other
methods and systems, and are not limited to the methods and systems
described above, and elements and acts of the various embodiments
described above can be combined to provide further embodiments.
Accordingly, the novel methods and systems described herein may be
embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the methods and
systems described herein may be made without departing from the
spirit of the disclosure. The accompanying claims and their
equivalents are intended to cover such forms or modifications as
would fall within the scope and spirit of the disclosure.
* * * * *