U.S. patent application number 11/749644 was filed with the patent office on 2008-08-14 for integrated circuit including packet network transceivers and fm receiver with fm antenna control.
This patent application is currently assigned to BROADCOM CORPORATION. Invention is credited to Seema B. Anand, Jesus Alfonso Castaneda, Ahmadreza (Reza) Rofougaran, Maryam Rofougaran.
Application Number | 20080194288 11/749644 |
Document ID | / |
Family ID | 39685783 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080194288 |
Kind Code |
A1 |
Castaneda; Jesus Alfonso ;
et al. |
August 14, 2008 |
INTEGRATED CIRCUIT INCLUDING PACKET NETWORK TRANSCEIVERS AND FM
RECEIVER WITH FM ANTENNA CONTROL
Abstract
An integrated circuit and/or device is provided that supports
wireless communications. The integrated circuit includes wireless
communication circuitry, frequency modulated (FM) receiver
circuitry, and FM antenna control circuitry. The communication
circuitry is coupled to convert an inbound radio frequency (RF)
signal into an inbound data signal and to convert an outbound data
signal into an outbound RF signal. The integrated circuit also
includes FM receiver circuitry that is coupled to convert an
inbound continuous wavelength signal into an inbound FM data
signal. FM antenna control circuitry is coupled to the FM receiver
circuitry for producing control signals to control a center
frequency of a gain profile of an FM antenna.
Inventors: |
Castaneda; Jesus Alfonso;
(Los Angeles, CA) ; Anand; Seema B.; (Rancho Palos
Verdes, CA) ; Rofougaran; Maryam; (Rancho Palos
Verdes, CA) ; Rofougaran; Ahmadreza (Reza); (Newport
Coast, CA) |
Correspondence
Address: |
GARLICK HARRISON & MARKISON
P.O. BOX 160727
AUSTIN
TX
78716-0727
US
|
Assignee: |
BROADCOM CORPORATION
Irvine
CA
|
Family ID: |
39685783 |
Appl. No.: |
11/749644 |
Filed: |
May 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60889528 |
Feb 12, 2007 |
|
|
|
Current U.S.
Class: |
455/553.1 |
Current CPC
Class: |
H03J 2200/10 20130101;
H03D 3/002 20130101; H03J 2200/06 20130101 |
Class at
Publication: |
455/553.1 |
International
Class: |
H04M 1/00 20060101
H04M001/00 |
Claims
1. An integrated circuit that supports wireless communications
comprises: wireless communication circuitry coupled to convert an
inbound RF signal into an inbound data signal and to convert an
outbound data signal into an outbound RF signal; FM receiver
circuitry coupled to convert an inbound continuous wavelength
signal into an inbound FM data signal; and FM antenna control
circuitry coupled to the FM receiver circuitry, the FM antenna
control circuitry producing control signals to control a center
frequency of a gain profile of an FM antenna.
2. The integrated circuit of claim 1, wherein the control signals
control switches of an external lumped element tuning array.
3. The integrated circuit of claim 1, wherein the FM antenna
control circuitry comprises: a plurality of switches to produce the
control signals, wherein the plurality of switches change an
impedance of external lumped tuning elements based upon the control
signals.
4. The integrated circuit of claim 1 further comprises: lumped
tuning elements coupled to the control signals, wherein the control
signals change an impedance of the lumped tuning elements.
5. The integrated circuit of claim 1 further comprises: a cellular
interface coupled to the wireless communication circuitry that
supports wireless data transmission.
6. The integrated circuit of claim 1 further comprises: FM
transmitter circuitry coupled to convert an outbound FM data signal
to an outbound continuous wavelength signal for broadcast.
7. The integrated circuit of claim 1 wherein the inbound data
signal is at least one of a low intermediate frequency (IF) signal
and a baseband signal based upon a local oscillation.
8. The integrated circuit of claim 1 wherein the wireless
communication circuitry accommodates at least one of: an IEEE
802.11 wireless standards specification; a Bluetooth wireless
standards specification; an advanced mobile phone services (AMPS)
wireless standards specification; a digital AMPS wireless standards
specification; a global system for mobile communications (GSM)
wireless standards specification; a code division multiple access
(CDMA) wireless standards specification; a local multi-point
distribution systems (LMDS) standards specification; and a
multi-channel multi-point distribution systems (MMDS) standards
specification.
9. A portable device that supports wireless communications
comprising: processing circuitry; a cellular network interface
coupled to the processing circuitry that supports wireless data
transmission with a base transceiver station; a user interface
coupled to the processing circuitry that supports user
input/output; memory coupled to the processing circuitry, wherein
the memory stores operational instructions that cause the
processing circuitry to: convert an inbound RF signal into an
inbound data signal and convert an outbound data signal into an
outbound RF signal; convert an inbound continuous wavelength signal
into an inbound FM data signal; and generate control signals to
control a center frequency of a gain profile of an FM antenna.
10. The portable device of claim 9, wherein the control signals
control switches of an external lumped element tuning array.
11. The portable device of claim 9, wherein the control signals
change an impedance of external lumped tuning elements.
12. The portable device of claim 9, wherein the memory further
stores operational instructions that cause the processing circuitry
to: convert an outbound FM data signal to an outbound continuous
wavelength signal for broadcast.
13. The portable device of claim 9 wherein the inbound data signal
is at least one of a low intermediate frequency (IF) signal and a
baseband signal based upon a local oscillation.
14. The portable device of claim 9 wherein the wireless data
transmission accommodates at least one of: an IEEE 802.11 wireless
standards specification; a Bluetooth wireless standards
specification; an advanced mobile phone services (AMPS) wireless
standards specification; a digital AMPS wireless standards
specification; a global system for mobile communications (GSM)
wireless standards specification; a code division multiple access
(CDMA) wireless standards specification; a local multi-point
distribution systems (LMDS) standards specification; and a
multi-channel-multi-point distribution systems (MMDS) standards
specification.
15. A wireless handheld device comprising: a case; an FM antenna; a
conductive layer providing a ground plane to the FM antenna, the
conductive layer adjacent the FM antenna in an electrostatic field
relation; a battery, the battery positioned adjacent an opposite
side of the conductive layer, wherein the FM antenna and the
battery are substantially parallel to each other in a spaced-apart
relation improving performance of the FM antenna; wireless
communication circuitry disposed within the case and coupled to
convert an inbound RF signal into an inbound data signal and to
convert an outbound data signal into an outbound RF signal; FM
receiver circuitry coupled to convert an inbound continuous
wavelength signal into an inbound FM data signal; and FM antenna
control circuitry coupled to the FM receiver circuitry, the FM
antenna control circuitry having control signals to control a
center frequency of a gain profile of the FM antenna.
16. The wireless handheld device of claim 15, wherein the control
signals control switches of an external lumped element tuning
array.
17. The wireless handheld device of claim 15, wherein the FM
antenna control circuitry comprises: a plurality of switches to
produce the control signals, wherein the plurality of switches
change an impedance of external lumped tuning elements through the
control signals.
18. The wireless handheld device of claim 15 further comprises:
lumped tuning elements coupled to the control signals, wherein the
control signals change an impedance of the lumped tuning
elements.
19. The wireless handheld device of claim 15 further comprises: FM
transmitter circuitry coupled to convert an outbound FM data signal
to an outbound continuous wavelength signal for broadcast through
the FM antenna.
20. The wireless handheld device of claim 15, wherein the FM
antenna further comprises: an input/output connection coupled to
the transceiver circuitry.
21. The wireless handheld device of claim 20 wherein the
input/output connection comprises at least one of: a coaxial probe,
a printed microstrip, a waveguide, and a coplanar transmission
line.
22. The wireless handheld device of claim 15 wherein the FM antenna
comprises at least one of a monopole, a dipole, an eccentric spiral
and a fractal antenna.
23. The wireless handheld device of claim 15 wherein the wireless
communication circuitry accommodates at least one of: an IEEE
802.11 wireless standards specification; a Bluetooth wireless
standards specification; an advanced mobile phone services (AMPS)
wireless standards specification; a digital AMPS wireless standards
specification; a global system for mobile communications (GSM)
wireless standards specification; a code division multiple access
(CDMA) wireless standards specification; a local multi-point
distribution systems (LMDS) standards specification; and a
multi-channel multi-point distribution systems (MMDS) standards
specification.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. ______, (Attorney Docket BP6124), filed May
16, 2007, which claims priority to U.S. Provisional Application
Ser. No. 60/889,528 entitled "Mobile Phone with an Antenna
Structure having Improved Performance," filed Feb. 12, 2007, all of
which are hereby incorporated herein by reference in their entirety
for all purposes.
SPECIFICATION
[0002] 1. Technical Field
[0003] The present invention relates to wireless communications
and, more particularly, signal reception and transmission in mobile
wireless communication systems.
[0004] 2. Related Art
[0005] Communication systems are known to support wireless and wire
lined communications between wireless and/or wire lined
communication devices. Such communication systems range from
national and/or international cellular telephone systems to the
Internet to point-to-point in-home wireless networks. Each type of
communication system is constructed, and hence operates, in
accordance with one or more communication standards. For instance,
wireless communication systems may operate in accordance with one
or more standards, including, but not limited to, IEEE 802.11,
Bluetooth, advanced mobile phone services (AMPS), digital AMPS,
global system for mobile communications (GSM), code division
multiple access (CDMA), local multi-point distribution systems
(LMDS), multi-channel-multi-point distribution systems (MMDS),
and/or variations thereof.
[0006] Depending on the type of wireless communication system, a
wireless communication device, such as a mobile telephone, two-way
radio, personal digital assistant (PDA), personal computer (PC),
laptop computer, home entertainment equipment, et cetera,
communicates directly or indirectly with other wireless
communication devices. For direct communications (also known as
point-to-point communications), the participating wireless
communication devices tune their receivers and transmitters to the
same channel or channels (for example, one of a plurality of radio
frequency (RF) carriers of the wireless communication system) and
communicate over that channel(s). For indirect wireless
communications, each wireless communication device communicates
directly with an associated base station (for example, for cellular
services) and/or an associated access point (for example, for an
in-home or in-building wireless network) via an assigned channel.
To complete a communication connection between the wireless
communication devices, the associated base stations and/or
associated access points communicate with each other directly, via
a system controller, via a public switch telephone network (PSTN),
via the Internet, and/or via some other wide area network.
[0007] Each wireless communication device includes a built-in radio
transceiver (that is, a receiver and a transmitter) or is coupled
to an associated radio transceiver (for example, a station for
in-home and/or in-building wireless communication networks, radio
frequency (RF) modem, et cetera). As is known, the transmitter
includes a data modulation stage, one or more intermediate
frequency stages, and a power amplifier stage. The data modulation
stage converts raw data into baseband signals in accordance with
the particular wireless communication standard. The one or more
intermediate frequency stages mix the baseband signals with one or
more local oscillations to produce RF signals. The power amplifier
stage amplifies the RF signals prior to transmission via an
antenna.
[0008] An antenna is an essential element for a wireless
communication device. The antenna provides a wireless interface for
the wireless communication device, which may be a radio, mobile
phone, pager, station (for wireless local area network, wireless
internet, et cetera). The particular type of wireless communication
system, which prescribes the transmission frequencies, reception
frequencies and power levels, dictates the performance requirements
for the antenna.
[0009] Because most wireless communication devices are handheld or
portable devices, each component including these devices must be
small, efficient, economical and lightweight--generally, provided
in forms of systems on chips or other integrated circuits. The
antenna is no exception--it too must be small, efficient,
economical and lightweight. To achieve these requirements, many
antennas have been developed having various structures including
monopole, dipole, et cetera.
[0010] The diminutive size of the antennas, however, leave them
more susceptible to environmental changes that correspondingly
affect the ability of an antenna to reliably receive and/or
transmit signals. For example, mobile phones can be readily held
within the grasp of a user, or placed within a pocket, et cetera.
When environmental conditions change, the impedance and
consequently the ability of the antenna are adversely affected,
reducing the signal-to-noise performance of the antenna.
[0011] Although favorable environmental conditions may return, a
user becomes frustrated by the inconsistency of the service for
their mobile phone or device. Also, the compactness of mobile
wireless devices can cause E-M interference between other device
components, further degrading antenna performance. Accordingly,
various types of antennas and corresponding shapes provide adequate
antenna performance. Nevertheless, they become becoming
increasingly sensitive to environmental changes and interference
from other device components. Therefore, a need exists for
miniaturized integrated circuit systems to be able to control
antenna impedances to improve the performance of increasingly
sensitive antennae.
SUMMARY
[0012] The present invention is directed to apparatus and methods
of operation that are further described in the following Brief
Description of the Drawings, the Detailed Description of the
Drawings, and the claims. Other features and advantages of the
present invention will become apparent from the following detailed
description of the drawings made with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A better understanding of the present invention can be
obtained when the following detailed description of the preferred
embodiment is considered with the following drawings, in which:
[0014] FIG. 1 is a functional block diagram illustrating a
communication system that includes a plurality of base stations or
access points (APs), a plurality of wireless communication devices
and a network hardware component;
[0015] FIG. 2 is a schematic block diagram illustrating a wireless
communication device architecture including an FM transceiver and
an FM antenna tuning module according to an embodiment of the
present invention;
[0016] FIG. 3 is an illustration for a center frequency of a gain
profile of an FM antenna;
[0017] FIG. 4 is a schematic block diagram illustrating a wireless
communication device architecture including an FM transceiver an FM
antenna tuning module coupled with a tuning circuit according to an
embodiment of the present invention;
[0018] FIG. 5 is a schematic block diagram further illustrating an
integrated circuit that supports wireless communications according
to an embodiment of the present invention;
[0019] FIG. 6 is a schematic block diagram of another integrated
circuit that supports wireless communications according to an
embodiment of the present invention;
[0020] FIG. 7 is an exploded view of a mobile phone with a brick
configuration that includes an antenna structure according to an
embodiment of the present invention;
[0021] FIG. 8 is an exploded view of a mobile phone with a
clamshell configuration that includes an antenna structure
according to an embodiment of the present invention;
[0022] FIG. 9 is a cross-sectional diagram of an antenna structure
including a printed FM antenna in a first orientation according to
an embodiment of the present invention;
[0023] FIG. 10 is a cross-sectional diagram of an antenna structure
including a printed FM antenna in a second orientation according to
another embodiment of the invention;
[0024] FIG. 11 is an exploded view of another antenna structure
including a dielectric spacer according to a further embodiment of
the present invention; and
[0025] FIG. 12 is a cross-sectional diagram of the antenna
structure of FIG. 11.
DETAILED DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a functional block diagram illustrating a
communication system that includes circuit devices and network
elements and operation thereof. More specifically, a plurality of
network service areas 04, 06 and 08 are a part of a network 10.
Network 10 includes a plurality of base stations or access points
(APs) 12-16, a plurality of wireless communication devices 18-32
and a network hardware component 34. The wireless communication
devices 18-32 may be laptop computers 18 and 26, personal digital
assistants 20 and 30, personal computers 24 and 32 and/or mobile
telephones 22 and 28.
[0027] The base stations or APs 12-16 are operably coupled to the
network hardware component 34 via local area network (LAN)
connections 36, 38 and 40. The network hardware component 34, which
may be a router, switch, bridge, modem, system controller, et
cetera, provides a wide area network connection 42 for the
communication system 10 to an external network element. Each of the
base stations or access points 12-16 has an associated antenna or
antenna array to communicate with the wireless communication
devices in its area. Typically, the wireless communication devices
18-32 register with the particular base station or access points
12-16 to receive services from the communication system 10. For
direct connections (that is, point-to-point communications),
wireless communication devices communicate directly via an
allocated channel.
[0028] Some or all of the wireless communication devices 18-32 may
include a FM transceiver to receive and/or transmit continuous
waveform signals in the FM frequency broadcast band, which in the
United States is 87.9 to 107.9 MHz. It can be appreciated, however,
that FM may be transmitted on any frequency. In the present
example, wireless communication devices 22, 24, 28, 30, and 32
include FM transceivers 23, 25, 31, 33, and 35, respectively. In
this manner, the wireless communication devices may receive and/or
transmit media content via FM frequency transmission
techniques.
[0029] In addition to media content (such as audio, video, et
cetera), a wireless communication device may receive and/or
transmit additional information such as Radio Data System ("RDS")
information, which provides digital information regarding FM radio
broadcasts. This information can include items such as time,
track/artist information, station identification, et cetera.
[0030] FM broadcast stations 54 and 56 transmit media content over
continuous waveforms in the FM band, in which the FM transceivers
23-33 receive via their respective FM antennas. The FM transceivers
then process the signals for playback of the media content to a
user device. Also, the wireless communication devices may transmit
FM signals as a local broadcast to nearby audio devices having FM
receivers, such as personal stereos, automobile FM radios, et
cetera.
[0031] The small wireless devices include correspondingly-sized FM
antennas having an antenna structure, which improves the antenna
performance across non-ideal environmental conditions for the small
wireless device. In general, a human body proximate to an FM
antenna affects the impedance of the FM antenna (such as the
wireless device being clasped in a user's hand, stored in a pocket,
notebook, et cetera). As a person moves either closer to or further
away from an antenna, the change in the relative position of the
person proximate to the antenna causes the impedance of the antenna
to change. A human body also absorbs the radio frequency waves,
affecting the electric field and the magnetic field of the RF wave.
Because the FM antennas are reduced to fit within a smaller
wireless device, the antenna impedances become more sensitive to
these varying environmental conditions.
[0032] As a result, the varying antenna impedances resulting from
the non-ideal environmental conditions affect the signal processing
and media content playback to a user. For example, when reception
conditions are less than ideal (that is, the signal-to-noise ratio
worsens), a stereo FM broadcast playback is in mono, or the FM
signal may be dropped altogether. With ever varying environmental
conditions, the varying and/or inconsistent playback frustrates
users. FM antenna control circuitry and antenna structure are
discussed in greater detail with reference to FIGS. 2 through
12.
[0033] FIG. 2 is a schematic block diagram illustrating a wireless
communication device 22-32. As illustrated, wireless communication
device 22-32 includes a digital processing module 54, a memory 56,
user interface(s) 52, transceivers 58-66, an FM antenna control
circuitry 68, a FM antenna 70, and antenna switch 72. The digital
processing module 54 and memory 56 execute instructions and perform
corresponding communication functions in accordance with a
particular mobile and/or cellular phone standard.
[0034] User interface(s) 52 allows data to be received from and
provides connectivity to an output device such as a display,
monitor, speakers, microphone, et cetera, such that the received
data may be displayed and/or presented. The digital processing
module 54 may also receive the outbound data from an input device
such as a keyboard, keypad, microphone, et cetera, via the user
interface(s) 52 or generate the data itself. The user interface
provides outbound data 76 to the digital processing module 54 for
transmission via one of the transceivers 58-66. The user interface
also receives inbound data 74 destined for a user.
[0035] The wireless communication device 22-32 includes several
transceivers (that is, receiver and transmitter) for accommodating
different communication and/or data sessions. The wireless
communication device 22-32 includes a cellular transceiver 58 (for
example, Personal Communication System (PCS), Global System for
Mobile Communications (GSM), Wideband CDMA, et cetera), a Wireless
Wide Area Network (WWAN) transceiver 60 (for example, WiMAX, HSDPA,
et cetera), a Wireless LAN (WLAN) transceiver 62 (for example, IEEE
802.11), a Wireless Personal Area Network (WPAN) transceiver 64
(for example, Bluetooth, IEEE 802.15, et cetera), and a FM
transceiver 66.
[0036] The transmitter portion of a transceiver generally includes
a data modulation stage, one or more intermediate frequency stages,
and a power amplifier stage. The data modulation stage converts raw
data into baseband signals in accordance with the particular
wireless communication standards specification. The one or more
intermediate frequency stages mix the baseband signals with one or
more local oscillations to produce RF signals. The power amplifier
stage amplifies the RF signals prior to transmission via an
antenna.
[0037] A transceiver's receiver portion generally includes a low
noise amplifier (LNA) stage, one or more intermediate frequency
stages, and a data demodulation stage. The LNA stage amplifies the
received RF signals for providing a stronger signal for subsequent
processing. The one or more intermediate frequency stages mix the
RF signals with one or more local oscillations to produce baseband
signals, in accordance with the particular wireless communication
standards specification. In other transceiver configurations, a
received FM signal may be converted directly to baseband signals.
The data demodulation stage operates to convert the baseband
signals into raw data.
[0038] The transceivers 58-64 receive and transmit RF signals via
the antenna switch 72, which operates to couple the receivers to
the antenna 86 in a receive mode, and to couple the transmitters in
a transmit mode. The antenna switch 72 provides a many-to-one
access to the antenna 86 for providing efficient use of antenna
resources. Examples of antenna switches are discussed in further
detail in U.S. Pat. No. 7,079,816, entitled "On Chip Diversity
Antenna Switch," issued Jul. 18, 2006, which is hereby incorporated
herein by reference.
[0039] The FM transceiver 66 receives continuous waveform signals
89 from an FM transmitter, such as FM broadcast stations 54 and 56
(see FIG. 1), via the FM antenna 70. Also, the FM transceiver 66
may transmit a continuous waveform signal 89 in the FM band to a
local receiver (such as a personal stereo, automobile FM radio, et
cetera).
[0040] An FM antenna tuning module 68, including lumped tuning
elements 69, operates to adjust the impedance match with the FM
antenna 70 with an impedance adjustment value 71. In general, the
smaller the "footprint" of an FM antenna, the more vulnerable its
performance is due to its positioning within a wireless
communication device with respect to other components, and the more
sensitive it is to changes in its operational environment that
adversely affect the tuning of the antenna 70 (such as by the
varying proximity of a user to the wireless communication
device).
[0041] The FM antenna 70 may be provided under a variety of
configurations, such as a monopole antenna, a dipole antenna (for
example, such as the dipole antenna depicted in U.S. Pat. No.
7,034,770, entitled "Printed Dipole Antenna," issued Apr. 25, 2006,
which is hereby incorporated herein by reference), an eccentric
spiral antenna (for example, such as the eccentric spiral antenna
depicted in U.S. Pat. No. 6,947,010, entitled "Eccentric Spiral
Antenna," issued Apr. 4, 2000, which is hereby incorporated herein
by reference), a fractal element antenna, et cetera. Each
configuration may have different design considerations.
[0042] As an example, a monopole antenna may have improved
performance over a dipole antenna structure due to the lower ohmic
loss of the antenna traces (that is, less antenna traces can be
used with a monopole structure). In general, a lower ohmic loss
provides the FM antenna 70 with higher antenna efficiency.
[0043] The monopole structure relies on the existing ground of the
mobile phone 22 to generate an image of the "missing" portion (that
is, the "dipole" portion for the monopole antenna). Because the
wireless device may not have a perfect ground available for
attachment of a monopole antenna structure, the impedance matching
may be unpredictable. The overall performance of a monopole
antenna, however, may improve due to the lower ohmic loss of the
antenna trace 218 with respect to small antenna "footprints".
[0044] Lower ohmic loss for an antenna may also be recognized by
operating an antenna at a higher resonant frequency, f.sub.C. For
example, the FM antenna 70 has a higher resonant frequency (such as
two-to-three times higher) than the intended operational frequency
(in the present example, the FM frequency band). The higher
resonant frequency permits the electrical length of the antenna to
be reduced, and correspondingly, the amount of space allocated for
the antenna trace. That is, a shorter electrical length has fewer
trace windings that can have larger trace surfaces in a given
antenna area--the result is a lower ohmic loss. In operation with
the FM transceiver 66, the receiver reduces the resonant frequency
of the FM antenna 70 to the intended frequency resonance using
discrete (or lumped) low-loss antenna matching components, such as
the lumped tuning elements 69.
[0045] A trade off, however, exists between the highest resonant
frequency to which the antenna is tuned versus the amount of
impedance matching (via the FM antenna control circuitry 68) to
bring the resonant frequency within the desired operational
frequency. For instance, when the antenna resonates at a very high
frequency, the required amount of impedance matching can be
excessive, consequently producing excessive antenna loss. In other
words, the advantage of having a lower ohmic loss and higher
antenna efficiency is lost. On the other hand, when the antenna
resonates substantially close to the desired resonant frequency,
fewer matching components would be needed; however, the resulting
ohmic loss of the resulting FM antenna trace would be comparable or
larger than the radiation resistance for the FM antenna 70
[0046] Regardless of the antenna configuration deployed, the FM
antenna 70 has a center frequency and a gain profile. The FM
antenna control circuitry 68 operates to center the FM antenna 70
within the desired operational frequency. The FM antenna control
circuitry 68, based upon a signal strength indication of a received
continuous wavelength signal 89, provides an adjustment control
signal to the lumped tuning elements 69. The lumped tuning elements
69 correspondingly varies the impedance (and the resonance
frequency) of the FM antenna 70 via an impedance adjustment value
71.
[0047] The lumped tuning elements 69 include voltage-controlled
variable impedance devices (such as varactors or varicap diodes) to
produce the impedance adjustment value 71. That is, by adjusting
the impedance value through the lumped tuning elements 69, the FM
antenna control circuitry 68 tunes the FM antenna 70 to the
operational conditions of the wireless communication device
22-32.
[0048] The FM antenna control circuitry 68 and the lumped tuning
elements 69 may be on a single integrated circuit or a plurality of
integrated circuits. Also, the FM antenna tuning module and the
lumped tuning elements 69 may be implemented as part of a system on
a chip. Examples of other implementations are discussed in detail
with reference to FIGS. 4 through 6. Also, antenna structures are
discussed in further detail with reference to FIGS. 7 through
12.
[0049] The digital processing module 54, in combination with
operational instructions stored in memory 56, executes digital
receiver and digital transmitter functions. The digital processing
module 54 may be implemented using a shared processing device,
individual processing devices, or a plurality of processing
devices. Such a processing device may be a microprocessor,
micro-controller, digital signal processor, microcomputer, central
processing unit, field programmable gate array, programmable logic
device, state machine, logic circuitry, analog circuitry, digital
circuitry, and/or any device that manipulates signals (analog
and/or digital) based on operational instructions.
[0050] Memory 56 may be a single memory device or a plurality of
memory devices. Such a memory device may be a read-only memory,
random access memory, volatile memory, non-volatile memory, static
memory, dynamic memory, flash memory, and/or any device that stores
digital information. Note that when digital processing module 54
implements one or more of its functions via a state machine, analog
circuitry, digital circuitry, and/or logic circuitry, the memory
storing the corresponding operational instructions is embedded with
the circuitry comprising the state machine, analog circuitry,
digital circuitry, and/or logic circuitry. Memory 56 stores, and
digital processing module 54 executes, operational instructions
corresponding to at least some of the functions illustrated and/or
described herein.
[0051] In operation, the digital processing module 54 processes
outbound data 76 in accordance with a particular wireless
communication standard (for example, IEEE 802.11a, IEEE 802.11b,
Bluetooth, IEEE 802.16, et cetera) to produce the appropriate
digital transmission formatted data for a present communication
session, which includes cellular data 59, WLAN data 61, WWAN data
65, and/or FM signal data 67. This data will be a digital baseband
signal or a digital low IF signal, where the low IF typically will
be in the frequency range of one hundred kilohertz to a few
megahertz.
[0052] Each respective transceiver 58-66 converts the digital data
from the digital domain to the analog domain. Though the antenna 86
is schematically depicted as external to the body of the radio,
commercial versions of the wireless communication device generally
incorporate the antenna element and structures within the body of
the device. Also, the wireless communication device may also
include additional antennas for standards specific applications,
such as those for Bluetooth applications, et cetera.
[0053] As one of average skill in the art will appreciate, the
wireless communication device of FIG. 2 may be implemented using
one or more integrated circuits. For example, the digital
processing module 54 and memory 56 may be implemented on a second
integrated circuit, and the remaining components of the wireless
communication device 22-32, less antenna 86, may be implemented on
a third integrated circuit. As an alternate example, the wireless
communication device 22-32 may be implemented on a single
integrated circuit.
[0054] FIG. 3 is an illustration for a center, or resonant,
frequency f.sub.C of a gain profile of an FM antenna with respect
to FM signal reception, which is represented as a received signal
strength 93. In this example, the center frequency f.sub.C is
"off-tuned" by a value "x." That is, the antenna is not centered
with respect to the local peak of the FM signal. Unless the antenna
tuning is corrected, the signal data may be distorted when
processed for playback to a user (such as with static, mono
playback, et cetera), or additional power resources may be needed
to correct the distortion.
[0055] The magnitude in which the center frequency is "off-tuned"
corresponds, in part, to the changing operational environment. That
is, the impedance changes affect the antenna center f.sub.C, such
as impedance changes the varying proximity of a user to the
wireless communication device). The FM antenna control circuitry
provides control signals to produce an impedance adjustment value
71 to correct the tuning for the antenna. The control signals are
discussed in detail with reference to FIGS. 4 through 6.
[0056] Although the impedance adjustment value 71 is shown to
center the antenna center frequency f.sub.C with the received
signal strength, the FM antenna control circuitry 68 may also
provide control signals that provide a tuning offset as discussed
to take advantage of smoother amplifier characteristics across a
greater bandwidth.
[0057] FIG. 4 is a schematic block diagram illustrating a wireless
communication device 22-32 that includes a distributed embodiment
of the FM antenna control circuitry 68 and the lumped tuning
elements 69,
[0058] As illustrated, the wireless communication device 22-32
includes a digital processing module 54 and a memory 56. The
digital processing module 54 and memory 56 execute instructions and
perform corresponding communication functions in accordance with a
particular mobile and/or cellular phone standard. To the extent
that like components and/or elements have been earlier described of
the wireless communication device 22-32, the description will not
be repeated here with respect to FIG. 3.
[0059] The wireless communication device 22-32 includes antenna
switch 75 and antenna switch 77. Antenna switch 75 services the
cellular Tx/Rx signal 81 and the WWAN Tx/Rx signal 83 for
transmission and/or reception modes over the antenna 86. Antenna
switch 77 services the WLAN Tx/Rx signal 85 and WPAN Tx/Rx signal
87 for transmission and/or reception modes over the antenna 86. The
FM transceiver 66 receives and/or transmits a continuous wavelength
signal 89 via the FM antenna 70.
[0060] Multiple antenna switches 75 and 77 permit each of the
antenna switches to accommodate the characteristics of similar
communications modes. Examples of characteristics may include
similar frequency bands, similar data rates, et cetera. For
example, an antenna switch may service cellular frequency bands
(such as for AMPS, IS-95 (CDMA), IS-136 (D-AMPS), GSM, operating in
the 824-849 MHz, 869-894 MHz, 896-901 MHz, and 935-940 MHz
frequency bands), and another antenna switch may service Personal
Communication Service ("PCS") frequency bands (such as for GSM,
IS-95 (CDMA), IS-136 (D-AMPS), operating in the 1850-1910 MHz and
1930-1990 MHz frequency bands). A further antenna switch may
service high-data rate communications (such as 2.4 GHz).
[0061] The FM transceiver 66 receives from the FM antenna 70 the
continuous wavelength signal 89 via the printed FM antenna 70. The
FM antenna control circuitry 68 receives a signal strength
indication (SSI) from the FM transceiver 66. Also, the FM
transceiver 66 may provide the received FM signal to the FM antenna
control circuitry 68, in which signal strength or other signal
characteristics may be evaluated to generate the control signals
73. When the SSI falls outside a permissible signal strength level,
the lumped tuning elements 69 provide an impedance adjustment value
71 to the printed FM antenna based upon the control signals 73 from
the FM antenna control circuitry 68.
[0062] The lumped tuning elements 69 are illustrated as provided on
a separate IC with respect to the FM transceiver 66 and the FM
antenna control circuitry 68. In this manner, differing fabrication
processes may be used to implement the voltage-controlled variable
impedance devices of the lumped tuning elements 69 and with
processes to implement other components of the wireless
communication device 22-32. That is, in some instances, a reduction
in fabrication cost and complexity may be realized. Also, wireless
communication devices may have an impedance bank accessible to
other components within the device to permit shared access to those
components (for example, for clock adjustment, et cetera). By
adjusting the impedance value of the lumped tuning elements 69, the
FM antenna control circuitry 68 tunes the FM antenna 70 to an
impedance of the communications device 22-32.
[0063] FIG. 5 is a schematic block diagram of an integrated circuit
270 that supports wireless communications and includes FM receiver
capability. The integrated circuit 270 includes FM receiver
circuitry 66 and FM antenna control circuitry 68. For support of
wireless communications, the integrated circuit 270 also includes
wireless communication circuitry 57 with transceivers 58 through 64
(see, e.g., FIG. 3).
[0064] The FM antenna control circuit 68 produces control signals
73 to control a center frequency of a gain profile of an FM
antenna, such as FM antenna 70 (see FIG. 3). The external lumped
element tuning array 69 includes a switch module 326 and lumped
tuning elements 28. The switch module 326 includes a plurality of
switches S.sub.0 through S.sub.Z that are coupled to the lumped
tuning elements 328 that includes a plurality of tuning elements
C.sub.0 through C.sub.Z, which may be voltage-controlled variable
impedance devices (such as varactors, varicap diodes, et cetera).
The plurality of switches S.sub.0 through S.sub.Z operate to alter
the impedance adjustment value 71 via the lumped tuning elements
328.
[0065] The FM receiver circuitry receives the continuous wavelength
signal 89 and provides a signal value 90 to the FM antenna control
circuitry 68. The FM receiver circuitry 66 also provides a FM data
signal 67 to the digital processing module 54.
[0066] The FM antenna control circuitry 68, based upon
characteristics of the signal value 90 (such as a received signal
strength indication), produces control signals 73 to control a
center frequency of a gain profile of an FM antenna. In operation,
the control signals 73 control the plurality of switches S.sub.0
through S.sub.Z of the external lumped element tuning array 69. In
turn, the switch module 326 controls the lumped elements C.sub.0
through C.sub.Z of the lumped tuning elements 328 to produce an
impedance adjustment value 71. In this manner, the control signals
73 serve to change an impedance of the external lumped element
tuning array 69.
[0067] Notably, the FM antenna control circuitry 68 provides for
rapid adjustment of the impedance adjustment value 71 and
correspondingly, rapid tuning of an FM antenna to accommodate
changing operational conditions to the wireless communication
device 22-32 (see FIG. 1).
[0068] FIG. 6 is a schematic block diagram of another integrated
circuit 280 that supports wireless communications and includes FM
receiver capability. The integrated circuit 270 includes FM
receiver circuitry 66 and FM antenna control circuitry 68. The FM
antenna control circuitry 68 further includes a switch module 346
with a plurality of switches S.sub.0 through S.sub.Z. For support
of wireless communications, the integrated circuit 270 also
includes wireless communication circuitry 57 with transceivers 58
through 64 (see, e.g., FIG. 3).
[0069] The FM receiver circuitry receives the continuous wavelength
signal 89 and provides a signal value 90 to the FM antenna control
circuitry 68. The FM receiver circuitry 66 also provides a FM data
signal 67 to the digital processing module 54 (FIG. 3).
[0070] The FM antenna control circuit 68, via the plurality of
switches S.sub.0 through S.sub.Z of the switch module 346, produces
control signals 73 to the external lumped tuning elements 348. The
external lumped tuning elements 348 include a plurality of tuning
elements C.sub.0 through C.sub.Z, which may be voltage-controlled
variable impedance devices (such as varactors, varicap diodes, et
cetera).
[0071] The FM antenna control circuitry 68, based upon
characteristics of the signal value 90 (such as a received signal
strength indication), produces control signals 73 to control a
center frequency of a gain profile of an FM antenna. In operation,
the FM antenna control circuitry 68 produces the control signals 73
from the plurality of switches S.sub.0 through S.sub.Z to the
external lumped tuning elements 348, to "pull" the resonant
frequency f.sub.C of FM antenna 70, by changing the impedance value
provided by the impedance adjustment value 71 with the lumped
elements C.sub.0 through C.sub.Z. The impedance adjustment value 71
provided to an FM antenna then pulls the center frequency of the
gain profile of the antenna to improve reception of an FM
signal.
[0072] Notably, the FM antenna control circuitry 68 provides for
rapid adjustment of the impedance adjustment value 71 and
correspondingly, rapid tuning of an FM antenna to accommodate
changing operational conditions to the wireless communication
device 22-32 (see FIG. 1).
[0073] FIG. 7 is an exploded view of a mobile phone 22 having an
antenna structure 200. The mobile phone 22 has a structure
sometimes referred to as a "brick." The mobile phone 22 includes a
case face cover 202, a case back cover 222, and a battery cover
228. The case face cover 202 includes a display 204, a function
keypad 206, and a numeric keypad 208. The case face cover 202
receives a printed circuit board 210 having integrated circuits
212, which include transceivers 58-66 (such as that discussed with
reference to FIGS. 2 and 3) that is coupled to a FM antenna 70 of
the antenna structure 200.
[0074] Further, the printed circuit board 210 may include lumped
tuning components to initially match the impedance of the mobile
phone 22 with the FM antenna 70. The case back cover 222 includes a
first side 219 and a second side 221. The second side 221 defines a
sloped portion 223 to receive the battery cover 228.
[0075] The mobile phone 22 supports different forms of
communication and information and/or media content. For example, in
addition to supporting voice calls, the mobile phone 22 can also
send and receive data, send text messages via a Short Messaging
Service ("SMS"), access Wireless Application Protocol ("WAP")
services, provide Internet access through data technologies such as
General Packet Radio Service ("GPRS"), sending and receiving
pictures with built-in digital cameras, video and sound recording,
et cetera. Additionally, local features may be available with the
mobile phone 22 such as alarms, volume control, user defined and
downloadable ring tones and logos, interchangeable covers, et
cetera.
[0076] The antenna structure 200 includes the FM antenna 70, a
conductive material forming a ground plane 224, and the battery
226. The FM antenna 70 includes an antenna trace 218, and an
input/output connection 216. The FM antenna 70 has a planar
structure that is less than a planar area of the battery cover 228,
and is positioned adjacent the inside of the battery cover 228. The
FM antenna 70 may have a variety of configurations that are
designed according to varying criteria, as discussed with respect
to FIG. 2.
[0077] Also, the FM antenna 70 may be implemented on one or more
printed circuit board layers and/or one or more integrated circuit
layers. The coupling of the transceiver circuitry of the integrated
circuits 212 with the FM antenna 70 may be direct or indirect and
positioned on the FM antenna 70 to achieve a desired load
impedance. For example, the input/output connection 216 may be a
coaxial probe, a printed microstrip, a waveguide, and a coplanar
transmission line, et cetera.
[0078] A battery 226 has a planar structure and is positioned
adjacent a second side of the ground plane 224, such that the
planar structure of the antenna 70 and of the battery 226 are
substantially parallel. The ground plane 224, which is positioned
between the battery 226 and the FM antenna 70, operates to improve
a signal-to-noise performance of the FM antenna 70. The battery 226
may have a conductive outer layer that provides the ground plane
224 to the FM antenna 70. The battery cover 228, case back cover
222, and the case face cover 202 couple to provide the electrical
and physical connectivity for operation of the mobile phone 22.
[0079] FIG. 8 is an exploded view of a mobile phone 28 having an
antenna structure 200. The mobile phone 28 has a structure
sometimes referred to as a "clamshell" structure. The mobile phone
28 supports different forms of communication and media information
content. For example, in addition to supporting voice calls, the
mobile phone 28 can also send and receive data, send text messages
via a Short Messaging Service ("SMS"), access Wireless Application
Protocol ("WAP") services, provide Internet access through data
technologies such as General Packet Radio Service ("GPRS"), sending
and receiving pictures with built-in digital cameras, video and
sound recording, et cetera. Additionally, local features may be
available with the mobile phone 28 such as alarms, volume control,
user defined and downloadable ring tones and logos, interchangeable
covers, et cetera.
[0080] The mobile phone 28 includes a first portion 242 and a
second portion 250. The first portion 242 includes a keypad 244, a
function keypad 246, and a case face cover 254. The first portion
242 also receives a FM antenna 70, and a battery 226, each of which
being separated by a ground plane 224. The battery 226, ground
plane 224, and the FM antenna 70 may be formed as a unit with the
back cover 229. The second portion 250 of the mobile phone 28
includes a display 248 for relaying call status and other
information that may be retrieved and presented to the user. The
first portion 242 and the second portion 250 fold along a hinge
portion 251 to a substantially parallel position when placed in a
closed position.
[0081] The mobile phone 28, via the first portion 242, receives a
printed circuit board 210 having integrated circuits 212, which
include transceiver circuitry 58-66 (such as that discussed with
reference to FIGS. 2 and 3). The FM transceiver 66 (see FIGS. 2 and
3) is coupled to the FM antenna 70.
[0082] The first portion 242 of the clamshell structure provides a
smaller footprint space and/or area for the FM antenna 70.
Accordingly, the performance of the printed FM antenna is more
readily influenced by changes in its operational environment by
impedance changes caused by a user and/or other objects. In this
regard, the ground plane 224 serves to mitigate these influences
and to further improve the performance of the printed FM antenna
with respect to signal reception. Also, the printed circuit board
may include lumped tuning components, which compensate for
impedances introduced by the mobile phone components, initially
tuning the FM antenna 70 to the wireless communication device
22-32.
[0083] The FM antenna 70 includes an antenna trace 252, and an
input/output connection 258. The FM antenna 70 has a planar
structure that is less than a planar area of the first portion 242
of the phone 28, and is positioned adjacent the ground plane 224.
The FM antenna 70 may be implemented on one or more printed circuit
board layers and/or one or more integrated circuit layers. The
coupling of the transceiver circuitry of the integrated circuits
with the FM antenna 70 may be direct or indirect, and positioned on
the FM antenna 70 to achieve a desired load impedance. For example,
the input/output connection 216 may be a coaxial probe, a printed
microstrip, a waveguide, and a coplanar transmission line, et
cetera.
[0084] The FM antenna 70 may be provided under a variety of
configurations depending upon the desired operational
characteristics. Examples of the varying configurations are
discussed in detail with respect to FIG. 2.
[0085] The battery 226 has a planar structure that is positioned
adjacent a second side of the ground plane 224, such that the
planar structure of the FM antenna 70 and of the battery 226 are
substantially parallel to each other in a spaced apart relation to
improve the performance of the FM antenna 70. The battery 226,
ground plane 224, FM antenna 70, and back cover 229 may be
integrated into a module that detachably couples with the first
portion 242 to provide the electrical and physical connectivity for
operation of the mobile phone 28. Further, the ground plane 224 may
be formed as a conductive layer to the battery 226.
[0086] FIG. 9 is a cross-sectional diagram of the antenna structure
200. The antenna structure 200 includes the FM antenna 70 and the
battery 226 with the ground plane 224 in a layered relation. The
antenna trace 218 is electrically insulated from the ground plane
224 by a protective layer 225. The FM antenna 70 has a planar
structure that is less than a planar area defined by the outer
periphery of the mobile phone battery cover 228, and is positioned
such that the antenna substrate 219 is adjacent the inner side of
the battery cover 228. The antenna trace 218 is oriented towards
the ground plane 224.
[0087] The antenna substrate 219 may be formed with the battery
cover 288, and further may be coupled to, or form a portion of, the
inner surface of the battery cover 228. The protective layer 225
and the antenna substrate 219 are made of a dielectric material
that provides electrical insulation between mobile phone components
while supporting electrostatic fields. Further, the dielectric
material has a dielectric constant sufficient to concentrate
electrostatic lines of flux while dissipating minimal energy in the
form of heat. Examples of materials include air, polyethylene,
polystyrene, et cetera. The planar structure of the FM antenna 70,
the ground plane 224, and the planar surface of the battery 226 are
substantially parallel to each other. The sandwiched structure
provides improved FM signal reception for the FM antenna 70.
[0088] FIG. 10 is a cross-sectional diagram of the antenna
structure 239. The antenna structure 239 illustrates another
sandwich structure that may be used in the mobile phones 22 and/or
28. The antenna structure 200 includes the FM antenna 70 and the
battery 226 with the ground plane 224 in a layered relation. The
antenna trace 218 is electrically insulated and/or mechanically
protected by a protective layer 225. The FM antenna 70 has a planar
structure that is less than a planar area defined by the outer
periphery of the mobile phone battery cover 228, and is positioned
such that the antenna substrate 219 is adjacent the ground plane
224. The antenna trace 218 is adjacent the inner surface of the
battery cover 228. Accordingly, the planar structure of the FM
antenna 70, the ground plane 224, and the planar surface of the
battery 226 are substantially parallel to each other. The
sandwiched structure provides improved FM signal performance for
the FM antenna 70.
[0089] FIG. 11 is an exploded view of a further antenna structure
230 implementing a dielectric spacer 257. The antenna structure 230
may be used in the brick structure of the mobile phone 28 and/or
the clamshell structure of the mobile phone 28, as well as other
suitable wireless device structures.
[0090] The antenna structure 230 includes the FM antenna 70 and the
battery 226 in a spaced-apart relation via a dielectric spacer 257.
The dielectric spacer 257 includes a first dielectric spacer
portion 260 and a second dielectric spacer portion 262. The
dielectric spacer 257 also includes web portions 261 that space the
first and dielectric spacer portion 260 and 262 in a fixed
relation, providing a first side 263 and a second side 265. The
dielectric spacer 257 provides further separation between the
battery 226 and the FM antenna 70, which services to improve the
E-M flux characteristics of the printed FM antenna, and improves
the performance of the FM antenna 70.
[0091] The dielectric spacer 257 has different dielectric constants
that are attributed to the components of the dielectric spacer 257
and the cavity 259 defined therein, which may be "filled" with air
from the surrounding environment. Also, the dielectric space 257
may be formed of a similar material throughout, or formed with
multiple materials with different dielectric properties.
[0092] In this manner, the dielectric spacer 257 provides
electrical insulation between the FM antenna 70 and mobile phone
components, while also supporting electrostatic fields. In general,
the area of the dielectric spacer 257 substantially corresponds to
the surface area of the FM antenna 70; however, dielectric spacers
with smaller surface areas may also be used while the desired
improvement to the performance of the printed antenna 256 is
realized.
[0093] The FM antenna 70 has a planar structure less than a planar
area defined by the outer periphery of the battery cover 228, and
is positioned adjacent the inner surface of the mobile phone
battery cover 228. The battery 226 has a planar surface positioned
adjacent the ground plane 224, which may be a conductive outer
layer of the battery 226. The conductive outer layer of the battery
226 may partially encase the battery 226 such that the ground plane
224 is positioned between the battery 226 and the FM antenna 70.
The sandwiched antenna structure 230 provides improved FM signal
performance for the FM antenna 70.
[0094] FIG. 12 is a cross-sectional diagram of the antenna
structure 230 of FIG. 8 with the dielectric spacer 257 and a gap
231 between the antenna structure 230 and the battery cover
228.
[0095] The antenna structure 230 includes the FM antenna 70 and the
battery 226 in a spaced-apart relation via the dielectric spacer
257. The FM antenna 70 has a planar structure generally
corresponding to the dielectric spacer 257 and a conductive layer
that provides the ground plane 224. The FM antenna 70 has a
protective layer 225 and an antenna trace 218, which face adjacent
to a first side of the dielectric spacer 257. A conductive layer
forming a ground plane 224 is positioned adjacent a second side of
the dielectric spacer 257, and the battery 226 is in turn adjacent
the ground plane 224.
[0096] In this manner, the planar structure of the FM antenna 70
and the planar surface of the battery 226 are substantially
parallel to each other in a spaced-apart relation, which serves to
improve the FM performance of the FM antenna 70. Further, the gap
231 provides a further dielectric effect with respect to the
antenna structure 230, in that a level of electrical insulation
between the antenna structure 231 and the case covers is provided
while supporting electrostatic fields conducive to FM antenna
operation.
[0097] As one of average skill in the art will appreciate, the term
"substantially" or "approximately", as may be used herein, provides
an industry-accepted tolerance to its corresponding term. Such an
industry-accepted tolerance ranges from less than one percent to
twenty percent and corresponds to, but is not limited to, component
values, integrated circuit process variations, temperature
variations, rise and fall times, and/or thermal noise. As one of
average skill in the art will further appreciate, the term
"coupled", as may be used herein, includes direct coupling and
indirect coupling via another component, element, circuit, or
module where, for indirect coupling, the intervening component,
element, circuit, or module does not modify the information of a
signal but may adjust its current level, voltage level, and/or
power level. As one of average skill in the art will also
appreciate, inferred coupling (that is, where one element is
coupled to another element by inference) includes direct and
indirect coupling between two elements in the same manner as
"coupled". As one of average skill in the art will further
appreciate, the term "compares favorably", as may be used herein,
indicates that a comparison between two or more elements, items,
signals, et cetera, provides a desired relationship. For example,
when the desired relationship is that a first signal has a greater
magnitude than a second signal, a favorable comparison may be
achieved when the magnitude of the first signal is greater than
that of the second signal or when the magnitude of the second
signal is less than that of the first signal. While the transistors
or switches in the above described figure(s) is/are shown as field
effect transistors (FETs), as one of ordinary skill in the art will
appreciate, the transistors may be implemented using any type of
transistor structure including, but not limited to, bipolar, metal
oxide semiconductor field effect transistors (MOSFET), N-well
transistors, P-well transistors, enhancement mode, depletion mode,
and zero voltage threshold (VT) transistors.
* * * * *