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RF POWER CONFIGURATION METHOD FOR BATTERY EQUIPPED PORTABLE RADIOS

IP.com Disclosure Number: IPCOM000007372D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-20
Document File: 3 page(s) / 158K

Publishing Venue

Motorola

Related People

Richard E. Pratt: AUTHOR [+2]

Abstract

Therefore, an alkaline cell pack operating at a higher nominal battery voltage can only be used on a low transmit power radio to guarantee radio relia- bility and maximum battery utilization.

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MOTOROLA Technical Developments Volume 24 March 1995

RF POWER CONFIGURATION METHOD FOR BATTERY EQUIPPED PORTABLE RADIOS

by Richard E. Pratt and Thomas Fitzgibbons

  Therefore, an alkaline cell pack operating at a higher nominal battery voltage can only be used on a low transmit power radio to guarantee radio relia- bility and maximum battery utilization.

BACKGROUND

  Portable 2-way handheld radios typically use a nickel cadmium (NiCad) battery power source. These batteries are low impedance and can supply several amperes of current with very little voltage drop. In standby or receive operation, the radio will draw around fifty to a few hundred milliamps, but in trans- mit it may draw a few amps. Because of the low impedance, the voltage delta between standby and transmit will only be a few hundred millivolts. Refer to Figures below for more detail.

  In some applications, a primary alkaline battery pack may be desirable because of extended shelf life, no charge time requirements, and multiple days of use. Alkaline cells have a higher internal resistance that will cause a much larger battery voltage delta between high current (transmit) and low current (standby, receive) loads. This large voltage drop in transmit will prematurely shorten the battery life by allowing the voltage to fall below minimum radio operating levels even though there is considerable capacity available if the battery was used at a lower current drain.

SOLUTION

  To ensure that the radio is never operated at high transmit power while the alkaline cell pack is used, and to allow the same radio to use high power when a normal NiCad battery is attached, the radio must be able to sense which battery is attached and dynamically reconfigure the radio transmit power depending on the attached battery type. Ifthe NiCad cell is detected, the radio would allow both High and Low Power transmitter operation, If the Pri- mary Alkaline cell is detected, the radio will only allow Low Power transmit even if high power was currently selected.

IMPLEMENTATION DETAILS

THE PROBLEM

  To hrlly utilize the alkaline cells, the cell pack nominal voltage may be raised in order to offset the voltage dropout caused by high current from trans- mitting. By raising the nominal voltage, the battery will no longer prematurely fall below the minimum operating level during transmit.

  Raising the cell pack nominal voltage causes a problem. The RF Power Amplifier cannot tolerate the higher supply voltage if transmitting at a high power setting. Also, when transmitting at high out- put power, the voltage drop will become so great that the delta cannot be overcome by increasing the cell pack nominal voltage, and again the cell pack will not be fully utilized.

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  Ideally, the battery could be internally coded in some way (i.e. using a k...