DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 201 of 242
8
DW1000 Calibration
The operating characteristics and performance of the DW1000 is dependent on the IC itself and on its
external circuitry and on its operating environment. To give optimum performance it is necessary to
calibrate the IC to account for factors which affect its operation.
Some calibration parameters are dependent solely on natural variations that occur within the silicon of the
IC during its manufacture. These are typically measured during IC production test and the required
calibration parameters are written to the OTP memory of the DW1000. The host system software can then
use these values during DW1000 configuration to optimise the DW1000 performance.
Some calibration parameters are dependent on circuit elements external to the IC. These can only be
determined during the manufacture of the product module into which the DW1000 is soldered. These
parameters are typically measured during module production test and the required calibration parameters
are stored somewhere in the module. An area of the DW1000’s OTP memory has been set for module test
calibration parameters. The host system software will use this calibration data during DW1000
configuration to optimise the DW1000 performance.
Some calibration parameters may vary according to the operational environment of the DW1000. For
example some parameters may need to be changed if there are large variations in the ambient temperature
(e.g. moving from a warm area into a cold store) or if there are significant changes in battery voltage supply.
In such circumstances in order to optimise the DW1000 performance the host system software can monitor
the voltage and temperature using DW1000 and adjust configuration accordingly.
Elements of the DW1000 that may be subject to calibration are:
Crystal trimming – the DW1000 contains trimming capacitors that can fine tune the operating
frequency of its crystal oscillator
Transmitter output power and spectrum – the DW1000 output spectrum is tuneable to meet
regional spectral regulations and maximise the output power to achieve the greatest operating
range.
Antenna delay – the DW1000 antenna delay may be fine-tuned to give best possible ranging or
location
accuracy.
The sub-sections below detail the calibration of these DW1000 parameters.
8.1 IC Calibration
– Crystal Oscillator Trim
DW1000 is specified to operate with clock offsets between the transmitting and receiving nodes of up to ±20
ppm. The receiver sensitivity of DW1000 can be improved by reducing the relative offset in clocks between
the transmitting and receiving nodes. One way to reduce the offset is to use temperature compensated
crystal oscillators (TCXO) in both transmitting and receiving nodes or just in one side of the link. Using TCXOs
increases system cost and current consumption so generally they are only used in fixed anchor scenarios.
Where crystals are used as the clock reference, DW1000 provides a facility to trim the oscillator frequency