Power delivered to antennae - RF Cafe Forums
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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.
The figure 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
%THE CALCULATED RF2175
OUTPUT IMPEDANCE (THE CONJUGATE OF THE LOAD)
rf2175_z=1.83712875712576 + 7.16437870763534i
THE THEVENIN VOLTAGE, P=v^2/r, pout=v^2/(2*real(rf2175_z))
IMPEDANCES OF COMPONENTS AT 380MHZ
%CALCULATE THE BRANCH CURRENTS
sprintf('CURRENT RATING FOR L6')
RATING FOR C9')
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
1.83712875712576 + 7.16437870763534i
CURRENT RATING FOR L6
VOLTAGE RATING FOR
CURRENT RATING FOR L1
VOLTAGE RATING FOR C10
VOLTAGE RATING FOR C11
POWER DELIVERED TO 50 OHM ANTENNAE
understand that the current rating for L6 would be determined by the dc bias current it supplies.
other calculations look correct?
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
Tue Feb 27, 2007 6:16 am
Not sure why your image isn't appearing. Let's try this: