DBBC Power Measurement

Testing of DBBC power measurement device reveals that it has a logarithmic output response!! This is for the “dbbcifa” command as it has to cover -3dBm to -48dBm (Gino on site at Warkworth 1/4/2012).

Update:13/6/2011: Logarithmic response verified, 37 mV/dB according to data sheet hmc610lp4-datasheet.pdf

Presumably the DC output from this chip is sampled by an ADC. Would not think it likely that this (ADC) has significantly non linear behaviour. Conclude that the numbers provided by DBBC are proportional to power in dB

See attached spreadsheet and notes below:

linearity-test-jun-2011.xls linearity-test-jun-2011-1.xls

We have used this to modify antcn in the Field System so that the DBBC can be used to provide power measurements for “fivept”, “onoff” and “acquire”. We have thus used for pointing which can be used by the Field System pointing model.

I'll attach the FS s/w for this in due course.

The “dbbc01” commnad gives power readings in a linear scale. But only for the sub-band of the total band set. (Gino on site at Warkworth 1/4/2012). If you have set dbbc01 to have a freq of 750MHz and a bandwidth of 16MHz, then you only get a linear power reading for the 16MHz part of the full 512MHz band centered on 750MHz.