aps023_transmit_power_calibration_management.pdf

1 INTRODUCTION ........................................................................................................................................ 4

2 HOW TRANSMIT POWER IS MEASURED FOR REGULATORY COMPLIANCE ................................................ 6

5 MANUAL MODE ..................................................................................................................................... 13

5.3.1 Introduction .................................................................................................................................. 14

5.3.2 Frames always longer than one millisecond ................................................................................. 15

5.3.3 More than 1 frame transmitted per millisecond ........................................................................... 16

7 CALIBRATING A DW1000 TRANSMITTER WITH BOOST ........................................................................... 20

8 MANAGING TRANSMIT POWER DURING NORMAL OPERATION ............................................................. 23

8.3.1 Is it necessary? .............................................................................................................................. 23

8.3.2 How do I implement it? ................................................................................................................. 24

9 REFERENCES ........................................................................................................................................... 27

LIST OF TABLES

TABLE 1: TYPICAL USE CASE EXAMPLES ........................................................................................................................... 23

TABLE 2: APPROXIMATE RATES OF CHANGE OF TX POWER WITH TEMPERATURE AND VOLTAGE .................................................. 24

TABLE 3: TABLE OF REFERENCES .................................................................................................................................. 27

TABLE 4: DOCUMENT HISTORY ..................................................................................................................................... 27

LIST OF FIGURES

FIGURE 6: OPERATION OF THE PRINCIPLE .......................................................................................................................... 8

FIGURE 7: CALIBRATION WITH FRAMES SHORTER THAN 1 MS ................................................................................................ 9

FIGURE 8: RELATIONSHIP BETWEEN FRAME DURATION AND ADDITIONAL TRANSMIT POWER........................................................ 9

FIGURE 9: TRANSMITTER POWER CONTROL REGISTER ........................................................................................................ 11

FIGURE 10: STRUCTURE OF THE 8-BIT TRANSMIT POWER CONTROL BYTE .............................................................................. 12

FIGURE 11: TRANSMIT POWER CONTROL REGISTER IN MANUAL MODE OF OPERATION ............................................................. 13

FIGURE 12: TIME DOMAIN PLOT OF FRAME SHOWING INCREASED POWER IN PREAMBLE AND PAYLOAD PORTIONS OF THE FRAME ..... 14

FIGURE 13: DECISION TREE FOR TRANSMIT POWER CALIBRATION IN MANUAL MODE ............................................................ 15

FIGURE 14: THE FOUR FRAME-DURATION “BINS” ............................................................................................................. 17

FIGURE 15: TRANSMIT POWER CONTROL REGISTER FOR FRAMES WITH DURATION > 500µS ...................................................... 18

FIGURE 21: SPECTRUM OF CORRECTLY CALIBRATED TRANSMITTER AT 6.8 MB/S DATA RATE WITH PRF16 AND 7 DB BOOST APPLIED 21

FIGURE 22: VARIATION OF TRANSMIT POWER OVER VOLTAGE AND TEMPERATURE .................................................................. 23

FIGURE 23: TRANSMIT POWER COMPENSATION SCHEME OVER TEMPERATURE & VOLTAGE ....................................................... 26

FIGURE 24: EXAMPLE OF PEAK POWER MARGIN WHEN PHR MEAN LIMIT SET TO -41.3 DBM / MHZ ......................................... 29

1 INTRODUCTION

1.1 Overview

This application note deals with the whole area of the power of the RF signal transmitted by the

DW1000 / DWM1000: -

1.2 What do we mean by transmit power?

It is important that we understand and define “transmit power” before we go any further.

Transmit power is generally used to refer to the signal power radiated from an antenna into the

surrounding environment. It can also refer to the signal power output from the DW1000 or at any

point in the chain between the DW1000 and the product’s antenna.

You should pay particular attention to the definition of transmit power in data sheets / manuals / test

specifications so that you understand exactly what is being referred to.

Transmit power is generally measured in dBm; i.e. power expressed in dB relative to 1 mW. The

equivalent to -14.3 dBm / 500 MHz. You should pay careful attention to the measurement bandwidth

to understand exactly what is being referred to.

This note uses the terms transmit power and transmitted power interchangeably throughout and

1.3 The importance of transmit power to link budget

The signal power that arrives at a receiver depends on a number of factors as seen by examining