DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 151 of 242
7.2.40.11
Sub-Register 0x27:28
– DRX_CAR_INT
ID
Length
(octets)
Type
Mnemonic
Description
27:28
2
RO
DRX_CAR_INT
Carrier Recovery Integrator Register
Register file: 0x27 – Digital receiver configuration
, sub-register 0x28 is a read-only 21 bit register.
The DW1000 receiver needs to compensate for frequency offsets between the timing references at the
transmitting device and itself to successfully receive a packet. Therefore, when a packet is successfully
received, the DW1000 has a sufficiently accurate estimate of the frequency offset.
This information is available in the carrier recovery integrator register, at address 0x27, offset 0x28. This is a
21 bit number with the lower 17 bits, the fractional part, and the upper 4 bits as the integer portion of the
number.
When a packet is successfully received, this register can be read and converted to the frequency error (in Hz)
using
F
offset
is the absolute frequency error in Hz. It can be converted to a clock offset (in ppm) by scaling by the
carrier frequency as follows
The minus sign is produced by the process of measuring the clock offset.
For a particular channel, the formulas reduce to multiplying the content of the carrier integrator register
with the appropriate constant from the table below:
Table 35: Constants for frequency offset calculation
Data Rate
Channel 2
Channel 3
Channel 5
850 kb/s, 6.81 Mb/s
-0.9313e-3
-0.8278e-3
-0.5731e-3
110 kb/s
-0.1164e-3
-0.1035e-3
-0.0716e-3