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Electronic signal concept

I want to make clear my electronic concept in my mind.

Suppose there is a 1GHz sin wave source signal coming from signal generator and is connected to an IC chip which is placed at 15cm away.

By the equation v=f*wavelength, the signal wavelength will be

v/f=3*10^8/10^9=30cm

Will the signal picking up at the IC chip have a phase change of 180 deg relative to the source signal at the signal generator?

Reply to
eeh
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--- No.

V will be less than C because of the delay caused by the medium through which the signal is travelling. For coax, v will be typically 0.6C, so you wind up with:

0.6C 1.8E8 lambda = ------ = ------- = 1.8E-1m = 18cm f 1.0E9

So, if one cycle of 18cm corresponds to 360°, 15cm would be result in a phase difference of:

15cm * 360° delta phi = ------------- = 300° 18cm

-- John Fields Professional Circuit Designer

Reply to
John Fields

On 27 Aug 2005 22:01:06 -0700, "eeh" wroth:

No. Unless the connection is through the air or a vacuum. Most cables have propogation speed of around sixty percent of the speed of light (through a vacuum).

Jim

Reply to
jmeyer

[...]

This is basically right but:

I think the average is closer to 70% for cables that one is likely to run

1GHz through. 
--
--
kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

You are basically right, except for one technical detail. The wavelength of RF (or any other EM) radiation depends on the medium it travels through. As others have noted, a 1 GHz signal travels at something like

0.6 C in typical cables. (C is the "speed of light.") In fiberglass circuit board material, the signal will travel at around 0.5 C, if the trace is on an internal layer, and faster if it is on a layer near the surface.

If you either change your example so that you use the actual speed of light in the medium, or if you get rid of the implied cable or circuit board you are using to convey the RF and instead just use transmit and receive antennas, then you will be right.

--Mac

Reply to
Mac

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