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TEMPERATURE COMPENSATED HIGH RESOLUTION POWER SET FOR WIDE DYNAMIC RANGE RF POWER AMPLIFIER

IP.com Disclosure Number: IPCOM000009143D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-09
Document File: 5 page(s) / 219K

Publishing Venue

Motorola

Related People

Sayed Merzaban: AUTHOR [+3]

Abstract

A method is presented to improve the resolu- Frequently these needs and expectations deter- tion of a power amplifier used in a wireless commu- mine the minimum required power that will be nication system by dynamically summing two out- necessary to meet the product specification. The puts of a DAC to produce one larger DAC which is minimum power required also determines the appro- the square of the capacity of the original one. Addi- priate PA module that may be used. It is understood tionally, a second method is presented which uses that this factor can not be compromised and it is a temperature to compensate the power amplifier. constraint on all other design factors.

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MOlOROLA Technical Developments

TEMPERATURE COMPENSATED HIGH RESOLUTION POWER SET FOR WIDE DYNAMIC RANGE RF POWER AMPLIFIER

by Sayed Merzaban, Bruce Barlow and Robert Proffitt

  A method is presented to improve the resolu- Frequently these needs and expectations deter- tion of a power amplifier used in a wireless commu- mine the minimum required power that will be nication system by dynamically summing two out- necessary to meet the product specification. The puts of a DAC to produce one larger DAC which is minimum power required also determines the appro- the square of the capacity of the original one. Addi- priate PA module that may be used. It is understood tionally, a second method is presented which uses that this factor can not be compromised and it is a temperature to compensate the power amplifier. constraint on all other design factors.

INTRODUCTION POWER CONTROL

  A power amplifier operated in communication device such as base station, mobile radio etc., typi- cally utilizes power control hardware to achieve the required output power. Typically this hardware sets the required voltage at power amplifier (PA) con- trol using digital-to-analog converter (DAC) and automatic loop control (ALC) circuitry. The resolu- tion of power setting depends on the DAC size.

  This paper presents a method for increasing the DAC size to improve resolution. Additionally, the hardware that controls the PA will be optimized to minimize variation of output power over temperture.

DESIGN CONSIDERATIONS

  Several factors need to be considered when designing the control circuit of a power amplifier used in a transceiver, namely:

  Determining the power control requirements is a thieved by matching the customer needs and expec- tations with the possible control circuitry available to provide it. In simplest case this means design- ing control circuitry to meet the worst possible case or in other words, the ability to set power amplifier to a precise setting. While this may be appropriate in some instances it usually requires a very large DAC. Large DACs add cost to the product and may make the product less attractive due to excess size.

POWER SElTlNG

A DAC is a significant factor when designing the control circuit as the resolution and accuracy

of the DAC determines the resolution and accura- cy of the output power. The larger the DAC, the better the resolution.

POWER VARIATION OVER TEMPERATURE

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Power output The temperature profile of the output power

Power control determines practical methods of controlling any

Power setting temperature variations. The simplest method of

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Power variation over temperature controlling those variations is by measuring the tem- perature of the device and adjusting the power for POWER OUTPUT each temperature. While this may seem appropri- ate in some instances it usually results in a diffi- After all the technical constraints have been cult and expensive design.
considered, the main contributing factor that often
determi...