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DATA THRU-PUT MAXIMIZATION USING THERMAL TRANSIENT DISSIPATION CONTROL

IP.com Disclosure Number: IPCOM000007573D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-08
Document File: 3 page(s) / 138K

Publishing Venue

Motorola

Related People

Larry Cygan: AUTHOR [+2]

Abstract

Present solutions which regulate the operating temperature of apparatus used in information trans- mission employ mechanisms which decreased the power output level ofthe transmitter. Generally, this is accomplished by sensing the temperature of a crit- ical transmitter element, such as the power ampli- fier heatsink, and decreasing drive to the power ampli- fier using a negative feedback arrangement. In TDMA systems, temperature control is ohen effected by reducing the number ofslots for which the trans- mitter is enabled when the critical element temper- ature is exceeded. This method avoids transmitter power reduction which may be detrimental to the quality ofthe received transmission under marginal signal conditions. A disadvantage of limiting the num- ber of slots used in transmission is the reduction of data thru-put (e.g., the number of bits per second which are transmitted).

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V Technical Developments

DATA THRU-PUT MAXIMIZATION USING THERMAL TRANSIENT DISSIPATION CONTROL

by Larry Cygan and Doug Hamilton

BACKGROUND

  Present solutions which regulate the operating temperature of apparatus used in information trans- mission employ mechanisms which decreased the power output level ofthe transmitter. Generally, this is accomplished by sensing the temperature of a crit- ical transmitter element, such as the power ampli- fier heatsink, and decreasing drive to the power ampli- fier using a negative feedback arrangement. In TDMA systems, temperature control is ohen effected by reducing the number ofslots for which the trans- mitter is enabled when the critical element temper- ature is exceeded. This method avoids transmitter power reduction which may be detrimental to the quality ofthe received transmission under marginal signal conditions. A disadvantage of limiting the num- ber of slots used in transmission is the reduction of data thru-put (e.g., the number of bits per second which are transmitted).

SOLUTION

  This invention monitors the transient thermal response characteristic present in the physical sys- tem and acts to gradually reduce the duty cycle when the critical element temperature is exceeded. The gradual duty cycle reduction replaces a step reduc- tion to a duty cycle whose steady state dissipation causes the transmitter to remain below the critical element temperature. Controlling the duty cycle in this manner retains desired temperature regulation while maximizing the data thru-put.

  A generalized block diagram of the invention is shown in Figure 1. The power amplifier heatsink temperature is monitored using a thermistor or other conventional sensing means to provide an input to the duty cycle controller block. This block acts to enable both the power amplifier and data formatting gate such that it determines when a data slot is trans- mitted, thereby regulating dissipation and subse- quently, the temperature ofthe transmitter. In order

to facilitate understanding of the invention, assume that the transmitter described in Figure 1 is used in a TDMA system, wherein a transmission frame is comprised of 6 equal time length slots. Further, assume that the number ~of slots available for use by the transmitter is under t,he control ofthe duty cycle controller. The slot usage may therefore range from zero slots to six slots per frame.

  Figure 2 depicts the ~heatsink temperature as a function of time for an ambient temperature of60 C under the condition of continuous transmitter oper- ation. This condition is synonymous with the use of all six slots per frame (6:6). Ifthe heatsink tempera- ture were to be maintained at or below 90 C, approxi- mately 75 seconds oftransmit time would be availa- ble. As shown in Figurei3, reducing the duty cycle to 3 slots per hame (3:6) aher 75 seconds, allows the transmitter to be opera...