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

IP.com Disclosure Number: IPCOM000009018D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Aug-01
Document File: 4 page(s) / 203K

Publishing Venue

Motorola

Related People

Sayed Merzaban: AUTHOR

Abstract

A method is presented to improve the resolution of a power amplifier used in a wireless communica- tion system by dynamically summing two outputs of a DAC to produce one larger DAC which is the square of the capacity of the original one. Additionally, a second method is presented which uses temperature to compensate the power amplifier.

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MO-LA Technical Developments

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

by Sayed Merzaban

  A method is presented to improve the resolution of a power amplifier used in a wireless communica- tion system by dynamically summing two outputs of a DAC to produce one larger DAC which is the square of the capacity of the original one. Additionally, a second method is presented which uses temperature to compensate the power amplifier.

INTRODUCTION

  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) control using digital-to-analog converter (DAC) and auto- matic loop control (ALC) circuitry. The resolution 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 temperature.

DESIGN CONSIDERATIONS

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

the needs and expectations of the user regarding out- put power.

  Frequently these needs and expectations deter- mine the minimum required power that will be nec- essary to meet the product specification. The mini- mum power required also determines the appropri- ate PA module that may be used. It is understood that this factor can not be compromised and it is a constraint on all other design factors.

POWER CONTROL

  Determining the power control requirements is achieved by matching; the customer needs and expectations with the possible control circuitry available to provide it. In simplest case this means designing control circuitry to meet the worst possi- ble case or in other words, the ability to set power of the 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 accuracy of the output power. The larger the DAC, the better the resolution.

POWER VARIATION OVER TEMPERATURE

  The temperature profile of the output power determines practical methods of controlling any temperature variations.: The simplest method of controlling these variations is by measuring the tem- perature of the device and adjusting the power for each temperature. While this may seem appropriate in some instances it usually results in a difficult and expensive design.

l Power output

l Power control

l Power setting

l Power variation over temperature

POWER OUTPUT

  After all the technical constraints have been considered, the main con...