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How do I delay and phase match a cable with a VVM - RF Cafe Forums
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| Buzzard
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Post subject: How do I delay and phase match a cable with a VVM
Posted: Wed Jun 16, 2010 7:19 am
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Joined: Wed Jun 16, 2010
7:04 am
Posts: 2 |
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I need to delay and phase match a new cable to a
reference cable at a frequency of approximately
900MHz. The reference cable is about 90 feet long
and I need to ensure the VVM 'phase' measurement
of the cable under test is for the same wave/cycle.
Is it a matter of starting at a low frequency (say
4Mhz) and gradually trimming, measuring and increasing
the frequency in small steps...this could take a
while to get to 900Mhz, so i'm sure someone out
there has a better method.
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karthik |
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Post subject: Re: How do I delay and phase match a cable with a VVM
Posted: Sun Jun 20, 2010 12:29 am
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Joined: Tue Apr 11, 2006
8:13 pm
Posts: 39 |
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Hi Buzzard,
Do you need an equivalent time
delay, or the same phase?
Karthik
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Buzzard |
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Post subject: Re: How do I delay and phase match a cable with a VVM
Posted: Mon Jun 21, 2010 5:49 am
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Joined: Wed Jun 16, 2010
7:04 am
Posts: 2 |
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I need to match the delay of the reference cable,
it has an 1-5/8" EIA flange on one end and a 1-5/8"
to N-type connector on the other.
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karthik |
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Post subject: Re: How do I delay and phase match a cable with a VVM
Posted: Sun Jul 11, 2010 8:49 pm
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Joined: Tue Apr 11, 2006
8:13 pm
Posts: 39 |
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Hi Buzzard,
In order to phase match the cables,
you would need to know the characteristics of the
two cables. If you know the dielectric being used
in each cable, then you can compute the 'guide'
wavelength in each cable, given by, lambda_g = 300/(f*sqrt(e_r)
), where, f is in MHz and lambda_g is in meters
and e_r is the relative dielectric constant of the
cable. Based on this, you can compute the total
phase for a given length of cable (at that frequency)
since 1 lambda_g = 360 degrees. Based on this, you
can phase match the two cables.
I hope I
have understood your question right and that this
helps...
Karthik
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Posted 11/12/2012
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