Electronic signal concept

[eeh]

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?

 

On 27 Aug 2005 22:01:06 -0700, "eeh" <eehobbyist@yahoo.com.hk> wroth:

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?

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

 

[John Fields]

On 27 Aug 2005 22:01:06 -0700, "eeh" <eehobbyist@yahoo.com.hk>
wrote:

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?

---
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

 

[Ken Smith]

In article <fql3h1538rdf7at7o7pgjpp366r757b6f2@4ax.com>, <the.hand> wrote:

On 27 Aug 2005 22:01:06 -0700, "eeh" <eehobbyist@yahoo.com.hk> wroth:

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.
[...]
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).

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

 

[Mac]

On Sat, 27 Aug 2005 22:01:06 -0700, eeh wrote:

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?

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