Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Power delivered to antennae Posted:
Fri Mar 09, 2007 11:32 pm
Joined: Tue Feb
27, 2007 6:16 am
Hello. I am designing a UHF transmitter.
I wish to be able to determine the requirements of components on the
output stage, after the amplifier and the power delivered to the antennae.
To begin with I am analyzing the application note designed for 380MHz.
My final design will be for 450MHz
The RF2175 datasheet claims
that the amp delivers 31.8dBm Linear Output Power.
below shows the output stage and where I have attempted to calculate
the current in the branches.
BELOW IS THE MATLAB
CODE I USED TO CALCULATE THE CURRENTS IN THE BRANCHES, COMPONENT RATINGS
AND THE MAXIMUM POWER DELIVERED TO THE ANTENNAE.
%DETERMINE THE RF2175
AMP'S OUTPUT POWER IN WATTS
CALCULATED RF2175 OUTPUT IMPEDANCE (THE CONJUGATE OF THE LOAD)
%CALCULATE THE THEVENIN VOLTAGE, P=v^2/r,
%CALCULATE THE IMPEDANCES OF COMPONENTS AT 380MHZ
%CALCULATE THE BRANCH CURRENTS
sprintf('VOLTAGE RATING FOR C9')
sprintf('CURRENT RATING FOR L1')
sprintf('VOLTAGE RATING FOR C10')
sprintf('VOLTAGE RATING FOR C11')
sprintf('POWER DELIVERED TO 50 OHM ANTENNAE')
BELOW IS THE RESULTS PRODUCED
CURRENT RATING FOR L6
VOLTAGE RATING FOR C9
CURRENT RATING FOR
VOLTAGE RATING FOR C10
VOLTAGE RATING FOR C11
TO 50 OHM ANTENNAE
I understand that the current rating for L6 would be determined
by the dc bias current it supplies.
Do these other calculations
When the data sheet states that the amp has 31.8dBm
output power, does this mean that if the load is a conjugate of the
output impedance, 31.8dbm will be delieverd to the load? Or is half
of this value disspiated in the output impedance of the amp?
Post subject: Posted: Mon Mar 12, 2007 11:19 pm
Joined: Tue Feb 27, 2007 6:16 am
sure why your image isn't appearing. Let's try this: