DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 106 of 242
The transmitter output power can be adjusted using this
Register file: 0x1E – Transmit Power Control
. This
contains four octets each of which specifies a separate transmit power setting. These separate settings are
applied by the IC in one of two ways. These two alternatives are described in section
7.2.31.3 – Manual Transmit Power Control
these two alternatives is selected by the setting of the DIS_STXP bit in
7.2.31.1
Units of TX Power Control
Register file: 0x1E – Transmit Power Control
, specifies the power as a
combination of a coarse gain parameter and a fine
gain parameter.
The gain control range is 33.5 dB consisting of 32 fine
(mixer gain) control steps of 0.5 dB and 7 coarse (DA
gain) steps of 3 dB, see Figure 26. For the best
spectral shape the coarse gain should be adjusted
first.
For optimum performance, (as noted in section
7.2.31), manufacturers have to calibrate the TX power
of each unit to account for IC to IC variations and
different IC to antenna losses. Usually the TX power is
set to the maximum allowed by spectral emission
regulations (-41.3 dBm/MHz) and such that no other
out-of-band limits are exceeded.
It should be noted that if you plan to use DA setting 000
you must ensure good isolation between pins VDDPA1
and VDDPA2 otherwise this setting may result in
compression of the TX signal. ( Good isolation requires seperate PCB tracks to each of these pins. )
7.2.31.2
Smart Transmit Power Control
This functionality applies when the
Disable Smart TX Power Control
bit DIS_STXP in
The power output regulations typically specify a transmit power limit of -41.3 dBm in each 1 MHz
bandwidth, and generally measure this using a 1 ms dwell time in each 1 MHz segment. When sending short
frames at 6.8 Mbps it is possible for a single frame to be sent in a fraction of a millisecond. Provided the
transmitter does not transmit again within that same millisecond, the power of that transmission can be
increased above the -41.3 dBm limit while remaining in compliance with the regulations. This transmit
power increase will increase the link budget and communication range. To make use of this the DW1000
includes functionality called Smart Transmit Power Control which automatically boosts the TX power for a
transmission when the frame is short.
Smart TX power control acts at the 6.8 Mbps data rate. When sending short data frames at this rate (and
providing that the frame transmission rate is < 1 frame per millisecond) it is possible to increase the transmit
Figure 26: Transmit power control octet
7
6
5
4
3
2
1
0
Coarse (DA)
setting
Fine (Mixer) setting
Bit number:
Meaning:
00000 = 0.0 dB gain
00001 = 0.5 dB gain
00010 = 1.0 dB gain
00011 = 1.5 dB gain
00100 = 2.0 dB gain
00101 = 2.5 dB gain
......
11010 = 13.0 dB gain
11011 = 13.5 dB gain
11100 = 14.0 dB gain
11101 = 14.5 dB gain
11110 = 15.0 dB gain
11111 = 15.5 dB gain
000 = 18 dB gain
001 = 15 dB gain
010 = 12 dB gain
011 = 9 dB gain
100 = 6 dB gain
101 = 3 dB gain
110 = 0 dB gain
111 = OFF – No output
