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: zero biased schottky detector problem Posted: Fri Aug 05, 2005 1:10 pm
I am sorry for the newbie question. RF is not my expertise and I need a few concepts to set up a small test
I have designed a detector using zero biased schottky diode in voltage doubler configuration using
Agilents HSMS 2852 package. I have mounted the SOT23 package along with relevant matching components on a 31 mils
FR-4 board. I provide RF input throught a signal generator at 900 MHz using end launch SMA connectors. The output
is measured using a Volt meter.
My problem, is that the measured performance is nowhere close to what is
mentioned in the data sheet (which I also get on simulation). The output DC voltage is much lower that mentioned
in data sheet at the input power levels. How can I go about "debugging" this problem?
Post subject: Zero-bias Schottky detectorPosted: Sat Aug 06, 2005 11:12 am
tell us a bit more about the operating conditions - like what is the RF voltage?
Voltage doubler circuits
don't work too well in the square-law region, so you have to have enough voltage to get above it into the
exponential region. In the case of Schottky diodes, one reason simulations sometimes are inaccurate is poor
modeling of the diode capacitance.
Post subject: Posted: Sat
Aug 06, 2005 7:06 pm
In the actual system, the detector will be working with power levels of 0dBm to -25 dBm.
However, right now, I am trying to test the performance of the detector circuit alone. I am varying the input
power level and trying to reproduce the charecteristic shown in the data sheets and application notes.
instance, application note 1089, shows that the DC output produced using the voltage doubler, at -30dBm, 900MHz
input is about 30mV. On measurement for my detector i get output of only about 1 -2mV.
I am just unsure
about where the problem might lie and to go about finding it.
subject: Voltage DoublerPosted: Sun Aug 07, 2005 7:44 pm
How does your circuit differ from the one in
AN-1089, both schematically and physically?