Can Single Wire Transmission Use a Goubou Wave?

[fisico30]

hello forum,

has anyone heard before about a Goubou wave and single wire transmission?

I always thought that for a circuit to properly work two conductors were needed, the signal conductor and the return conductor, both in DC and AC...

Is that true?
thanks.
fisico30

 

[RocketSci5KN]

A return path is required for any signal. For high speed signals, the return path needs to be very close to the signal path, to minimize inductance (path of least inductance taken). For very low speed signals, even the Earth ground may be a suitable return path (path of least resistance taken).

 

[fisico30]

Hi RocketSci5KN,

thanks for your reply.
i agree with you but that single-wire thing can actually work.
By the way, do you know "why" the return wire is always needed?

thanks
fisico30

 

[Skaperen]

I have never heard of Goubou

Are you looking at this in terms of transmission of power, or transmission of signals?

You can charge a single wire. Repeatedly charging it and discharging it can send signals and perhaps tiny amounts of power. But it will have a substantial amount of inductance against that transmission.

How about a zero-wire transmission line?

 

[dlgoff]

hello forum,

has anyone heard before about a Goubou wave and single wire transmission?

I always thought that for a circuit to properly work two conductors were needed, the signal conductor and the return conductor, both in DC and AC...

Is that true?
thanks.
fisico30

When I first saw your thread title, I thought about http://en.wikipedia.org/wiki/Single-wire_earth_return" used in some rural areas. But while looking around I found this.

A Goubau line, or G-line for short, is a type of single wire transmission line intended for use at UHF and microwave wavelengths. [3] The line itself consists of a single conductor coated with dielectric material. Coupling to and from the G-line is done with conical metal "launchers" or "catchers," with their narrow ends connected for example to the shield of coaxial feed line, and with the transmission line passing through a hole in the conical tips. Planar Goubau Lines with applications at terahertz frequencies have also been demonstrated recently [4].

http://en.wikipedia.org/wiki/Single-wire_transmission_line"

 

[MATLABdude]

hello forum,

has anyone heard before about a Goubou wave and single wire transmission?

I always thought that for a circuit to properly work two conductors were needed, the signal conductor and the return conductor, both in DC and AC...

Is that true?
thanks.
fisico30

A G-line is a type of waveguide, rather than a wire in an electric circuit.

http://en.wikipedia.org/wiki/Goubau_line

A zero-wire transmission line? How about a laser beam or focused microwaved? You'll lose all kinds of power (especially the microwave), but you can still convey some amount of energy to the desired target.

 

[RocketSci5KN]

I read the article on the Wikipedia page and it's a bit beyond me. The comment from Wikipedia stating it's a form a waveguide makes some sense. I think you need some input from microwave experts. The standard electrical transmission theory I've learned says this should not work.

 

[chrisbaird]

A return path is required for any signal. For high speed signals, the return path needs to be very close to the signal path, to minimize inductance (path of least inductance taken). For very low speed signals, even the Earth ground may be a suitable return path (path of least resistance taken).

That's just wrong. What is the return wire of a signal along a fiber optic cable? What is the return wire, or even the send wire, for a signal being sent from my remote control to my TV? No wires at all are needed to send signals. Wires are not used because they make signal transmission possible, rather because they make signal transmission efficient or more controlled.

You may argue that data links without return paths are really waveguides and not electric circuits. But in reality, all signal transmissions, including in simple coax cables, are waveguides. It is the waving electric and magnetic field that carries the signal, even in wire circuits, not the physical movement of an electron from one end of wire to the other.

 

[RocketSci5KN]

Of course I meant 'electrical signal', clearly signals based on photons or throwing rocks do not require a return signal...

 

[chrisbaird]

How exactly is an 'electrical signal' different from a guided wave? See http://en.wikipedia.org/wiki/Coaxial_cable#Signal_propagation" instance.

 

[sophiecentaur]

The Goubou line is a very similar mode of propagation to the well known Ground Wave mode of MF and LF radio propagation. In the case of a groundwave, there is a slight forward tilt of the wave front radiated from the antenna. This means that, instead of dispersing up into space, energy is constantly being angled back downwards to the ground. It means that the shadowing effect of a town full of steel buildings actually recovers some distance beyond the town. A real bit of luck for the Radio Engineers.
In the Goubou line, a dielectric sleeve around a single transmission line keeps a wave that is initially launched (from a horn or other feed arrangement) tilted and directed along the line without dispersing excessively, out into space. It has been used as a light weight feed for getting signals from a transmitter up to an antenna mounted on a balloon, when a coax feeder would be too heavy and a two wire feeder could twist and tangle up.

 

[fisico30]

hello sophiecentaur,

thanks for the reply. You mention that the forward tilt of the wavefront as the cause of the field to stay guided...where I can read more about this process of propagation?

What keywords or topics should i search?

thanks
fisico30

 

[sophiecentaur]

"MF ground wave propagation" would probably show in an extended google search. I managed to find http://www.radio-electronics.com/info/propagation/ground_wave/ground_wave.php" link, after a brief search.


I used to read about this sort of thing in books like Jordan 'Electromagnetic Propagation and Wave theory' (or some such title; it was all a long time ago). All those books still exist in University Libraries but I fear that people seldom actually read them and prefer to Google instead. Only a year or so ago I spent a happy morning in Brighton University LIbrary and found something I needed about EM propagation.