Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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Power delivered to antennae - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
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: