DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 206 of 242
In DW1000 applications using transmit power calibration, the calibrated TX_POWER value should be read by
the application from OTP memory as part of setup and programmed into
Register file: 0x1E – Transmit
. This register is preserved in the AON memory as long as the IC is powered. This facilitates the
use of this value when the IC wakes up from
8.2.1.2
Calibration
– Smart TX Power Control
With Smart TX Power Control enabled the calibration is similar to the method used for Manual TX Power
Control except that we do not transmit repeated back to back frames. For this calibration, we configure the
transmitter to transmit 1 frame per millisecond. To do this, configure the Transmit Power Spectrum Test
Mode, see the TX_PSTM field description of
Sub-Register 0x2F:24 – Digital Diagnostics Test Mode
.The repeat frame interval must be set in DX_TIME register, for a repeat interval of 1 ms, a value of
0x0001E780 should be written to DX_TIME, as described in the TX_PSTM field description.
Depending on the length of the frames to be used, see
7.2.31.2 – Smart Transmit Power Control
,the
TX_POWER setting should be adjusted until the transmit level is just below the required spectral density limit
(usually -41.3dBm/MHz). This register value should then be stored in the OTP memory, see section
6.3.2 –
Programming a value into OTP memory
for details of how to program OTP memory and recommended
memory locations.
In DW1000 applications using transmit power calibration, the calibrated TX_POWER value should be read by
the application from OTP memory as part of setup and programmed into
Register file: 0x1E – Transmit
. This register is preserved in the AON memory as long as the IC is powered. This facilitates
the use of this value when the IC wakes up from
or
8.2.2 Other TX adjustments to consider
DW1000 recommended transmitter analog/RF settings will not need adjustment for most
designs/applications, however the following registers can be adjusted to tune the transmit spectrum
bandwidth or passband flatness:
Sub-Register 0x28:0C– RF_TXCTRL
, used to tune the transmit mixer.
Sub-Register 0x28:0C– RF_TXCTRL
, used to tune the transmit mixer Q-factor.
Sub-Register 0x2A:0B – TC_PGDELAY
, used to tune the width of pulses and hence the spectrum
bandwidth.
To tune any of these values, start with the default value (as given in the register descriptions
Sub-Register 0x2A:0B – TC_PGDELAY
), and adjust the value iteratively observing
the effect on a spectrum analyser until the PSD occupies as much of the applicable spectral mask as possible.
8.3 IC Calibration
– Antenna Delay
In order to measure range accurately, precise calculation of timestamps is required. To do this, a delay called
the antenna delay must be known. The DW1000 allows this delay to be calibrated and provides the facility to
compensate for delays introduced by PCB, external components, antenna and internal DW1000 delays.
