RE: Fwd: Re: [SI-LIST] : Re: Methods to introduce noise in power planes

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From: jeremy_webb@agilent.com
Date: Thu Apr 19 2001 - 12:38:50 PDT


Farrokh,

After reading Mr. Anderson's first response about using a bias tee to
introduce noise into the power
planes, I built my own bias tee as I did not have one readily available to
me. I built it to inject
frequencies down to 3kHz using a 5uF(50VDC) capacitor and a 1000uH inductor.
It worked quite well.

                 L = 1000uH
    DC ____n_n_n_______ AC + DC
                        |
                        - C = 4.7uF ~= 5uF
                        -
                        |
                        AC

When checking to see if it worked I had to add a 10ohm(20 Watt) resistor
from "AC + DC" to ground.
Hope this helps.

Sincerely,

Jeremy Webb

-----Original Message-----
From: Ray Anderson [mailto:Raymond.Anderson@Sun.COM]
Sent: Thursday, April 19, 2001 1:57 PM
To: si-list@silab.eng.sun.com; farrokh@cisco.com
Subject: Re: Fwd: Re: [SI-LIST] : Re: Methods to introduce noise in
power planes

We were using the tee for tests just on the PLL section of a system
so 500 mA capability worked OK.

For a whole system board you will need to either search further
or build your own with a beefier inductor.
(the devil's in the details....)

-Ray

>
>A follow up question please:
>
>Ray Anderson wrote: "Feed the DC power to your system through the tee's RF
>choke." The bias tees are capable of passing 500 ma at the most, my board
>under test requires over 10 amps. How is raw DC power connected to the
board?
>
>Thanks,
>
>Farrokh Mottahedin
>
>

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