DW1000 Transmit Power Setting

Hi,

dw1000 user manual section 7.2.31.1 is telling about the register configurations that we can set to get particular gains, but how these gains are related to transmit power. We can measure the practical value of transmit power using spectrum analyzer, but how will we cross check this with the actual theoretical power that the device can transmit. What is the theoretical relation between the DA/Mixer gains and the actual transmit power.

Regards,
Shijo Thomas

Hi ,There is a good bit of info also in APS023 Part 1&2 and our production test application note APS012
These are available from our website: https://www.decawave.com/application-notes/

Regards
/Leo

Dear Leo,

I have referred these documents, but I am not getting a relation between the DA/Mixer gains settings and the real output power. For example if I want to transmit a power of -10dB, what value I need to program into these registers. Is there any calculations for this?

Regards,
Shijo Thomas

Hi,

It’s not that straight forward as it all depends on your design
I suggest to connect a spectrum analyser to your design and chick the registers with the bits and bytes described in the User manual and translate the bits /byte of 0x1E to the

Eg if register 1E reads 62626262 then since 0x62 is 01100010 in binary form, the coarse gain setting is 0x03, which is equal to
9dB, and the fine setting is 0x02, which is 1dB (total is 10 dB)

Dear Leo,

According to your example total power setting is 10dB. This means power output from DW1000 RF interface(input to antenna) is 10dB?

Regards,
Shijo Thomas

10 dB is a measure of gain not power and so can’t be the output power.

Going from the datasheet the DW1000 maximum output power will vary unit to unit but is -39 dBm/MHz typically with a maximum of -35 dBm/MHz for some units.

So with all the gains set to maximum and a 0 dB antenna you will normally get -35 dBm/MHz out, 6.3 dB over the maximum for most standards.

This would imply that a typical maximum gain without violating the limits will be 27 dB minus any antenna gain.