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Nicole Mun New Member Offline Posts: 3	Frequency Response using a TDR Jan 22^nd, 2010, 4:31pm Hi folks, I need to measure VSWR and insertion loss at 500Mhz. But I dont have signal generator and power meter. Yet i can get a cable testing TDR with adjustable pulse. Would it be possible to measure insertion loss by adjusting pulse so that it has fundamental frequency near 500Mhz. Thanks for your advice....
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pancho_hideboo

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Re: Frequency Response using a TDR
Reply #1 - Jan 22^nd, 2010, 7:13pm

Nicole Mun wrote on Jan 22^nd, 2010, 4:31pm:

I need to measure VSWR and insertion loss at 500Mhz.
But I dont have signal generator and power meter.

You need a directional coupler in addition to signal generator and power meter to measure VSWR.

VSWR is equivalent to |S11|.
Insertion Loss is |S21|².

Nicole Mun wrote on Jan 22^nd, 2010, 4:31pm:

Yet i can get a cable testing TDR with adjustable pulse.
Would it be possible to measure insertion loss by adjusting pulse so that it has fundamental frequency near 500Mhz.

What do you mean by "adusting pulse" ?

If you have oscilloscope having TDR function, you can measure VSWR by TDR.
Insertion Loss can be measured by TDT.
Even if your oscilloscope doesn't have TDR function, you can do TDR by using pulse generator and power divider with oscilloscope.

http://en.wikipedia.org/wiki/Time-domain_reflectometer
http://en.wikipedia.org/wiki/Time-domain_reflectometry

What instruments do you have ?
Show me list of all instruments you have.

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« Last Edit: Jan 22^nd, 2010, 10:50pm by pancho_hideboo »

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Nicole Mun

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Re: Frequency Response using a TDR
Reply #2 - Jan 27^th, 2010, 9:09am

pancho_hideboo, thanks for your response.
I am sorry I did not realize i posted in the wrong area and it was removed to RF measurements appropriately

Regarding "What do you mean by "adusting pulse" ?"
I have a cable testing TDR riser bond 1205cx
http://www.radiodetection.com/servedoc.asp?filename=1205cxaManual.pdf
It allows to adjust pulse width and shows dBrL
So I was wondering the following....
Since it will be sending a series of pulses, instead of a single pulse.
and pulse width is adjustable, I may be able to create something closer to 500Mhz.
then would i be able to approximate vswr and insertion loss with a tdr.
again thanks for the response.

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1205cxaManual-1.pdf

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pancho_hideboo

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Re: Frequency Response using a TDR
Reply #3 - Feb 4^th, 2010, 3:43am

Nicole Mun wrote on Jan 27^th, 2010, 9:09am:

I have a cable testing TDR riser bond 1205cx
http://www.radiodetection.com/servedoc.asp?filename=1205cxaManual.pdf

I read manual of "cable testing TDR riser bond 1205cx".

Nicole Mun wrote on Jan 27^th, 2010, 9:09am:

Since it will be sending a series of pulses, instead of a single pulse.

I don't think "1205cx" sends a series of pulses.

Nicole Mun wrote on Jan 27^th, 2010, 9:09am:

and pulse width is adjustable, I may be able to create something closer to 500Mhz.

Even if "1205cx" can send a series of pulses, periodical signal of 500MHz have any meaning in TDR ?
Do you understand TDR correctly ?
Generally you can not measure frequency characteristics of impedance by TDR.

If you want to consider frequency characteristics in TDR, rather control rise time of pulse not period of pulse.

Nicole Mun wrote on Jan 27^th, 2010, 9:09am:

then would i be able to approximate vswr and insertion loss with a tdr.

How do you approximate vswr and insertion loss with a TDR ?

Again do you understand TDR correctly ?

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http://www7.plala.or.jp/ungeromeppa/flash/kita.html
http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related

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