Apparatus, method and article of manufacture providing for auxiliary battery conservation in adapters

An apparatus, method and article of manufacture are disclosed which provides for auxiliary battery conservation in adapters requiring auxiliary batteries. A power controller selects from one of two or more power sources to provide variable power components with DC power. For instance, power consumption of the transmitter (more specifically the transmit power amplifier) varies with the desired transmit power level. The transmitter can be supplied with DC power from the host device or the auxiliary source or both. The power controller can select the source of DC power (i.e., the host device or the auxiliary battery) or may combine the two power sources to provide necessary power to the transmit power amplifier.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to conservation of auxiliary battery power in 
adapters. More particularly, it relates to an apparatus and method for 
conserving auxiliary battery power in a wireless device that is connected 
to a host device. 
2. Description of the Prior Art 
Wireless devices enable computers to communicate with other computer 
devices without requiring physical access to a land line communication 
port. One type of wireless device is a wireless modem which is similar to 
a wired modem in that it permits a computer or other device to send and 
receive data from external sources. A wireless modem may be installed as 
an adapter card or in an adapter slot such as a Personal Computer Memory 
Card International Association PCMCIA slot. A wireless modem typically 
consists of two major portions: a radio portion and a baseband portion. 
The radio portion consists of a transmitter and a receiver. The transmitter 
and receiver may share a common antenna via a duplexer. The transmitter is 
responsible for generating RF signals using a baseband signal to modulate 
a carrier signal. The receiver is responsible for producing a baseband 
signal from RF signals by demodulating an RF signal received at the 
antenna to produce a demodulated baseband signal. The radio provides 
physical access to a network or connection (i.e., the wireless network). 
An antenna is used for transmitting and receiving the electromagnetic 
communications signals from the air interface. 
The baseband portion provides a baseband signal to the transmitter and 
accepts baseband signals from the radio receiver. The baseband portion 
decodes the baseband signals to provide data (i.e., receiving data) and 
encodes data to provide a baseband signal for transmission by the 
transmitter (i.e., sending data). 
As is typical of wireless modems, a portion of the wireless modem fits into 
a PCMCIA adapter slot. The adapter may consist of an integrated package or 
several separate components that can be attached via appropriate cabling. 
The radio portion of the wireless adapter contains the transmitter, 
receiver and associated circuitry to provide for RF communications. The 
ability of the radio to transmit at certain ranges is limited by the 
transmit power it can radiate via the antenna. The radio transmitter can 
require substantial amounts of current (as much as 1 amp) to operate. Most 
wireless systems require that the transmitter radiate power at levels up 
to 3 watts. The transmitted power levels in some wireless systems are 
controlled by the base station transmitter. The radiated power level can 
thus require that approximately 1 amp of current be supplied to the radio 
transmitter of the wireless modem when the wireless modem is radiating at 
higher power levels. Typically transmit power levels for Advanced Mobile 
Phone Service (AMPS) cellular and Cellular Digital Packet Data (CDPD) 
transmissions are 600 mW. For Advanced Radio Data Information Service 
(ARDIS), transmission levels of 1 W are typical. 
The PCMCIA architecture can typically only supply a PCMCIA slot with a 1/2 
amp (500 mA) of current. This limitation is due to the nature of the 
PCMCIA interface and the PCMCIA standard itself. Therefore, with wireless 
adapters the PCMCIA bus of the host computer can supply less than half the 
required current when the radio transmitter is operating at higher power 
levels. In order to provide the required power, prior art systems have 
supplemented the power supplied to the radio with an auxiliary battery or 
batteries. These prior art systems have directly coupled the auxiliary 
power source to the transmit amplifier. 
Use of the auxiliary battery creates several problems, especially for 
laptops or mobile computing devices. First, the auxiliary battery is 
inconvenient for mobile computer users to carry (i.e., 4AA NiCAD 
batteries). This inconvenience is caused by the bulk and weight of the 
auxiliary battery. The bulk of the auxiliary battery also makes the mobile 
device unwieldy to place and utilize. Secondly, the auxiliary battery 
needs to be periodically recharged. Auxiliary battery re-charging, in 
addition to any host battery recharging, is an inconvenience for user. The 
wireless adapter's recharging unit may be incompatible with the recharging 
system for the laptop thus forcing the user to carry two different 
recharging mechanisms: one for the mobile unit's battery and one for the 
adapter's auxiliary battery. Thirdly, prior art systems directly coupled 
the auxiliary battery to the transmitter's power amplifier. This caused 
the wireless adapter to be inoperable under any operating conditions when 
the auxiliary battery needed recharging. Thus, there is an unsatisfied 
need in the prior art to reduce the size of the auxiliary battery and/or 
increase the time periods between recharging. There is also a need to 
permit wireless adapters to operate in certain circumstances with a dead 
or defective auxiliary battery. 
These unresolved problems and deficiencies are clearly felt in the art and 
are solved by the invention in the manner described below. 
SUMMARY OF THE INVENTION 
The above-mentioned needs have been met in accordance with the present 
invention by providing for an apparatus that satisfies these needs. 
Accordingly, it is an object of the present invention to provide an 
adapter that uses a smaller auxiliary battery. 
It is an object of the invention to provide power to the adapter solely 
from a host computer when the host computer can supply the power 
requirements of the adapter. 
It is another object of the invention to provide for operating the adapter 
in a low power mode when the auxiliary power source is unavailable or 
unable to supply power. 
It is an object of the invention to supplement the power provided to the 
adapter by a host computer with an auxiliary battery only when the host 
computer cannot supply the required power to the wireless adapter. 
It is another object of the invention to provide a lightweight wireless 
adapter. 
It is a further object of the invention to provide a wireless adapter that 
has a sleek slimline appearance. 
It is yet another object of the invention to provide a wireless adapter 
that is very portable. 
It is still a further object of the invention to reduce the need for 
recharging the auxiliary battery. 
It is still a yet another feature of the invention to conserve auxiliary 
battery power. 
Accordingly, an adapter card for use in a host device is provided, the 
adapter having an auxiliary power interface for receiving power from an 
auxiliary source; a host power interface for receiving host power signals; 
a power bus for distributing power on the adapter card, the power bus 
coupled to the host power interface; a switch for electrically coupling 
the host power interface or the auxiliary power interface to a variable 
power component; and, a controller for causing the switch to supply the 
variable power component with power from the auxiliary power interface 
when the power required by the variable power component exceeds a 
threshold, else causing the switch to supply the variable power component 
with received host power signals. 
Also provided is a method of conserving auxiliary batter power in an 
adapter, the method having the steps of: determining a transmit power 
level and an associated power required by a power amplifier to yield a 
desired transmit power level; comparing the associated power required by 
the power amplifier with available power from a host interface; and 
supplying the power amplifier with power from an auxiliary source if the 
available power from a host interface is insufficient to meet the 
associated power required by the power amplifier. 
An adapter card for use in a host device, the adapter card having an 
auxiliary power interface for receiving power from an auxiliary source; a 
host power interface for receiving host power signals; a power bus for 
distributing power on the adapter card, the power bus coupled to the host 
power interface; and a power augmentation device for electrically coupling 
the host power interface to a variable power component and for augmenting 
power supplied to the variable power component from the host power 
interface with power supplied from the auxiliary power interface; and, a 
controller for causing the power augmentation device to augment power 
supplied to the variable power component with power from the auxiliary 
power interface when the power required by the variable power component 
exceeds the power that can be allocated to the variable power component 
from the host power interface. 
A method of conserving auxiliary battery power is provided having the 
following steps: determining a transmit power level and an associated 
power required by a power amplifier to yield a desired transmit power 
level; comparing the associated power required by the power amplifier with 
available power from a host power interface; and supplementing the power 
amplifier with power from an auxiliary source if the available power from 
the host power interface is insufficient to meet the associated power 
required by the power amplifier.

DETAILED DESCRIPTION 
Although the present invention will be described with respect to a wireless 
radio adapter it is applicable to any adapter which supplements power from 
a host device with an auxiliary battery during normal operations. The 
present invention receives power from at least two sources: a host device 
and an auxiliary power source. The host device may be a laptop computer, 
such as an IBM Thinkpad computer, having one or more PCMCIA slots. For the 
purposes of this specification, "Host Device" is a generic term used to 
describe a machine, which is usually a computer or terminal or lap top or 
palm top or hand held or personal digital assistant or other device. The 
host device provides slots for accepting adapter cards. In the preferred 
embodiment these adapter cards and slots conform to Personal Computer 
Memory Card International Association (PCMCIA) standards. 
The present invention will be described with respect to a constant or near 
constant voltage level, which for PCMCIA systems is +5 volts. Using the 
assumption of constant or near constant voltage level, power which is 
typically measured in watts can be represented by the current (amps) that 
a particular device or component is drawing. Therefore, current can be 
used to represent power. For instance, the PCMCIA slot can deliver 500 
milliamps of current. This can be used to represent power or compute power 
in watts (2500 mwatts=500 milliamps*5 Volts). The present invention is in 
no way limited to constant or near constant voltage systems. 
One embodiment of the present invention is shown in FIG. 1. As shown the 
wireless modem consists of a PCMCIA adapter card 107 containing the 
baseband portion of the modem, a cable 105 for connecting the PCMCIA card 
to the radio module 101. The radio module 101 is shown with antenna 111. 
Note that the radio module can be mounted on the host device such as the 
back of the display or integrated into the host device. The radio module 
101 is supplied power from the PCMCIA card via cable 105 and the auxiliary 
batteries contained within the housing 103. A 22 pin ITT connector is used 
to connect the base band portion to the radio portion, although any 
suitable cable or electrical coupling may be utilized. The PCMCIA card 107 
contains a 68 pin PCMCIA standard connector that enables the card to be 
inserted into any PCMCIA adapter slot. 
In an alternative embodiment the baseband adapter card and radio module can 
be integrated into a single card that can be inserted into a PCMCIA slot. 
The single integrated card may have a section that protrudes externally 
from the PCMCIA slot when the integrated card is inserted into the slot. 
In the embodiment shown in FIG. 1, cable 105 carries signals between the 
radio module 101 and the baseband card 107. These signals provide the 
radio module 101 with power, control information, baseband signals for 
transmission and provides the baseband portion with status information and 
received baseband signals. 
FIG. 2 depicts a functional block diagram of a wireless modem adapter 
according to the present invention. The wireless modem adapter interfaces 
with the host device via the standard 68 pin PCMCIA connector and PCMCIA 
interface logic 203. The PCMCIA architecture permits information to be 
written and read from the wireless modem adapter card. The PCMCIA 
interface is described in detail in the PCMCIA Specification (i.e., 
Personal Computer Memory Card International Association--PCMCIA Standard 
Release 2.1) which is hereby incorporated by reference. The PCMCIA 
interface logic 203 may be combined with micro-controller 205 which may 
also be combined with DSP 207 into a single integrated circuit package. 
The adapter card looks to the PCMCIA bus as an I/O card type. The adapter 
card receives DC power from the PCMCIA interface and an auxiliary battery 
209. The auxiliary battery 209 may be mounted on the wireless modem 
adapter or may be external to the wireless modem adapter and coupled by a 
cable or other suitable connection or may be detachably mounted to the 
adapter card. DC power is distributed throughout the adapter using 
standard DC power distribution lines and techniques. 
In the preferred embodiment a DC variable power controller 211 can select 
one of two or more sources to provide variable power components with DC 
power. For instance, power consumption of the transmitter 217 (more 
specifically the transmit power amplifier) varies with the desired 
transmit power level. The transmitter can be supplied with DC power from 
the host device or the auxiliary source or both. The micro-controller can 
signal or instruct the DC variable power controller 211 to provide the 
variable power component(s) with power from one of the power sources. This 
can be accomplished, for instance, by writing to a register or memory 
location assigned to the DC variable power controller 211. The DC variable 
power controller 211 can select the source of DC power (i.e., the host 
device or the auxiliary battery) or may combine the two power sources to 
provide necessary power to the transmit power amplifier. 
In the preferred embodiment the power received from the host device is 
distributed to all components of the wireless adapter with exception of 
one or more of the variable power consumption components such as the 
transmit power amplifier. Other components that have variable power 
characteristics may also be supplied power from the DC variable power 
controller on separate lines or share the same lines. Power management 
with multiple power components could provide none, one, or all of the 
variable power components with auxiliary power as power demand changed. 
The variable power components are supplied power via the DC variable power 
controller. 
In a wireless modem, the component that has the potential to draw the most 
current and use the most power is the transmitter, specifically the 
transmit power amplifier. In most wireless systems the transmitted power 
of each adapter can be controlled by the base station. Transmitter power 
control by the base station allows the base station to better control the 
energy transmitted in the operating portion of the RF spectrum. Thus, when 
the wireless adapter is close to the base station's antenna, the adapter's 
transmit power can be lower than when the wireless adapter is operating in 
a fringe area or farther away from the base station. When the adapter's 
transmit power output is reduced, the current required by the RF power 
amplifier is reduced, often dramatically. As is often the case, for 
certain periods of time the power required by the wireless adapter is less 
than the maximum power that the host device can supply. For instance, a 
PCMCIA slot can supply 500 ma of current. The wireless adapter can take 
advantage of these time periods to conserve its auxiliary batteries by 
switching the auxiliary batteries off-line. 
The present invention makes use of the variable power consumption 
requirements of the wireless radio transmitter. When the transmitter 
requirements are such that the host device can supply the wireless adapter 
with all necessary power then the micro-controller 205 instructs or causes 
the DC variable power controller 211 to provide the transmitter with power 
solely from the host device. When the transmitter requires more power than 
the host device can supply, the micro-controller 205 instructs or causes 
the DC variable power controller 211 to supply the transmitter with power 
from the auxiliary source. 
One embodiment of the DC variable power controller 211 is a single pole, 
double throw switch that is located between the auxiliary battery and the 
transmit power amplifier, so that the power amplifier can be powered 
alternatively by either the auxiliary battery or the host device through 
the PCMCIA interface. The switch is controlled by either a hardware or 
software threshold mechanism responding to a signal or determination that 
sets the transmit power output of the wireless adapter's transmitter. When 
the total expected power consumption for the wireless adapter exceeds the 
threshold then the auxiliary power is used to supply the transmitter's 
power amplifier else the host device supplies the power amp. The threshold 
may be computed in watts or amps. After determining the desired transmit 
power level, the current draw for the power amplifier can be determined 
based on known characteristics of the power amplifier. An algorithm or 
table may used to provide transmitter current draw versus output power 
level. The threshold is based on the maximum power/current that the host 
device can supply. When the adapter is transmitting at a power level that 
can be completely supplied by the host device, the host device supplies 
the power to the entire wireless adapter including the variable power 
components. If the host device can supply 500 ma, of which 300 ma is used 
to power components other then the power amplifier, then 200 ma is 
available for the power amplifier. Thus, whenever the transmit power level 
requires the power amplifier to draw less or equal to 200 ma the auxiliary 
battery is not needed. Assuming an amplifier having a 50% efficiency 
rating operating at 5 volts, a PCMCIA slot can supply a transmit level up 
to 500 mw (200ma*5v*0.50). If the host device cannot supply all necessary 
power then the auxiliary battery is used to supply or supplement the power 
supplied to the transmit power amplifier. The relatively few periods of 
time that the host device cannot supply the transmit power amplifier with 
the required power it is supplied by the auxiliary battery, greatly 
reducing the draw on the auxiliary battery. 
The auxiliary power savings of the present invention can be illustrated 
using an example. FIG. 3 illustrates a depiction of a prior art system for 
supplying DC power to a prior art wireless adapter. The wireless adapter 
components, other than the transmit power amplifier typically draw about 
300 ma of current which is supplied by the PCMCIA adapter port. The 
auxiliary batteries are directly coupled to the power amplifier and supply 
between 50 ma-450 ma of current. Note that the power amplifier is always 
drawing some current from the auxiliary batteries when the wireless 
adapter is powered up. Assuming operating characteristics as described in 
table I, 
TABLE I 
______________________________________ 
Transmit Power 
Auxiliary Battery Supplied 
Time Usage (%) 
Amps 
______________________________________ 
15% 600 mw 450 ma 
70% 200 ma 
15% 100 ma 
______________________________________ 
the hourly time average current draw from the auxiliary battery is as 
follows: 
Time Average ma=0.15*450+0.70*200+0.15*100=222.5 ma. 
Therefore, a 1 hour transmit interval requires a battery with a 223 ma per 
hour capacity. 
FIG. 4 illustrates the present invention wherein the DC variable power 
controller 405 is programmed or instructed to supply DC power to the 
transmit power amplifier when the transmit power level is greater than 250 
mw and to use power from the host device when the transmit power is 250 mw 
or less. Adapter components, other than the transmit power amplifier 
typically draw about 300 ma of current which is supplied by the PCMCIA 
adapter slot. The auxiliary batteries supply 450 ma of current to the 
transmit power amplifier only when the output power level is 600 mw. Note 
that the power amplifier is not drawing any current from the auxiliary 
batteries when the transmit power levels are at the 250 mw and 100 mw 
levels. This situation is illustrated 
TABLE II 
______________________________________ 
Transmit Power 
Auxiliary Battery Supplied 
Time Usage (%) 
Level 
Amps 
______________________________________ 
15% 600 mw 450 ma 
70% 0 ma 
15% 0 ma 
______________________________________ 
in Table II where the hourly time average current draw from the auxiliary 
battery is as follows: 
Time Average ma=0.15*450+0.70*0+0.15*0=67.5 ma. 
Therefore, a 1 hour transmit interval requires a battery with only a 68 ma 
per hour capacity. 
As the above example demonstrates, the present invention permits the use of 
a smaller auxiliary battery or a greater time between re-charging or a 
combination of both. Also the present invention still permits the adapter 
to operate in low power mode when the auxiliary battery is unavailable. By 
reducing the auxiliary power consumed by the adapter card, a longer 
lasting power supply or smaller sized power supply can be utilized. Also 
with the present invention, the wireless adapter card can still function 
in low power mode when the auxiliary battery is dead or needs recharging 
or is in the process of recharging. 
FIG. 5 depicts the method of the present invention. In step 501, the 
adapter determines the required transmit power level. In the preferred 
embodiment this is accomplished by the micro-controller carrying out an 
appropriate software routine. The required transmit power level may be 
received from the base station in a message or it may be calculated by the 
micro-controller using a protocol or it may be read from storage or some 
other means. Even though some wireless systems fix the transmit power 
level, most wireless modems can support various wireless systems so that 
although auxiliary power cannot be conserved for all wireless systems, the 
present invention can conserve power with respect to some. From the 
required transmit power level, and known characteristics of the power 
amplifier and wireless adapter card the required current for the power 
amplifier can be calculated. Alternatively a table can used to relate 
transmit power level to the controller state. This is shown as step 503. 
In step 505 a check is made to determine whether the required current 
level for the power amplifier exceeds the power level that host device can 
supply. For example, if the adapter card is a PCMCIA adapter card and 
requires 300 ma of current, excluding the power amplifier then if the 
power amplifier requires a current of 200 ma or less the PCMCIA host 
device can supply the current necessary to power the amplifier without the 
auxiliary battery as shown in step 509. If the power amplifier requires 
more than 200 ma then the auxiliary power source is needed to supply the 
requested power as shown in step 507. 
An alternative embodiment of a wireless modem adapter can use a wireless 
telephone to provide for the RF functions. The baseband portion may also 
be included or integrated into the phone. The PCMCIA card would thus 
supply power and data in and data out signals to the baseband function 
within the phone. The cable connector at the phone and the signal mapping 
would depend on the particular type of cellular phone that was utilized. 
The DC variable power controller could be located within the phone along 
with the auxiliary batteries. 
In an alternative embodiment an additional circuit can be added to control 
the charging of the auxiliary battery. Whether being charged from the host 
device or an external charger, a switch is placed between the charger and 
the auxiliary battery. This switch is controlled by the transmit signal, 
such that it is open while transmitting and closed when not transmitting. 
This permits the host supply to be utilized while not exceeding its 
current limits. In this embodiment, the power controller 211 is 
implemented as several discrete switches each of which is controlled by 
microprocessor 205. This is shown in FIG. 6. When the microprocessor 
recognizes that the transmitter power level called for is less than a 
ceratin value, it sends a discrete control signal to close switch 602 and 
open switches 603 and 601. Alternatively, when the microprocessor 
recognizes that the transmitter power level called for is at or above the 
certain value, it sends a discrete control signal to open switch 602 and 
close switch 603. Switch 601 remains open in either case. When the 
microprocessor determines that the auxiliary battery 209 needs to be 
charged, usually by measuring voltage, it sends discrete control signals 
open switches 602 and 603, and close 601. Current can then flow from the 
Host battery to the auxiliary battery and thereby recharge it. The 
resistor 604 has an appropriate value to set the required charging 
circuit. 
Another alternative embodiment of the power controller 211 is shown in FIG. 
7. The switches of FIG. 6 have been replaced by devices whose conductance 
can be controlled by discrete signals from the microprocessor. This can be 
accomplished using digital to analog converters that present the required 
analog signal to the gate of a MOSFET device. In FIG. 7 current sensor 705 
sends a signal to the microprocessor which informs the microprocessor 
about how much current is being drawn from the host battery by the 
transmitter. In this way, the microprocessor can control the conductances 
of devices 702 and 703 such that a maximum amount of current is supplied 
by the host battery and only when that host capacity is going to be 
exceeded that additional current is supplied to the transmitter from the 
auxiliary battery. When recharging the auxiliary battery, devices 702 and 
703 are opened and the microprocessor sends the control to 701 necessary 
to cause the required charging current to go from the Host to the 
auxiliary battery. 
The preferred embodiment of the present invention contains one or more 
software systems or software components or functions. In this context, a 
software system is a collection of one or more executable software 
programs, and one or more storage areas (for example, RAM, ROM, cache, 
disk, flash memory, PCMCIA, CD-ROM, Server's Memory, ftp accessible 
memory, etc.) In general terms, a software system should be understood to 
comprise a fully functional software embodiment of a function or 
collection of functions, which can be added to an existing processing 
system to provide new function to that processing system. Software systems 
generally are constructed in a layered fashion. In a layered system, a 
lowest level software system is usually the operating system which enables 
the hardware to execute software instructions. 
A software system is thus understood to be a software implementation of a 
function which can be carried out in a processor system providing new 
functionality. Also, in general, the interface provided by one software 
system to another software system is well-defined. It should be understood 
in the context of the present invention that delineations between software 
systems are representative of the preferred implementation. However, the 
present invention may be implemented using any combination or separation 
of software or hardware systems. 
The software systems may be distributed on a computer usable medium such as 
floppy disk, diskettes, CD-ROM, PCMCIA cards, flash memory cards and/or 
any other computer usable medium. Note that the software system may also 
be downloaded to a processor via a communications network or from an 
Internet node accessible via a communications adapter. 
While the invention has been described in detail herein in accord with 
certain preferred embodiments thereof, modifications and changes therein 
may be effected by those skilled in the art. Accordingly, it is intended 
by the appended claims to cover all such modifications and changes as fall 
within the true spirit and scope of the invention.