Impedance of PCB track at 433Mhz

[[email protected]]

Hi to all.
How can one determine the impedance of a pcb track.
The track is about 5cm long , 1.7mm wide , grounded on one end. There
is
no ground plane.All the searches I've done come up with microstrip
calculations which don't seem
to cater for this geometry.
The track acts as an antenna , so I would like to know it's impedance
to design a matching network.
This RF stuff is not my strong point , so any pointers would be great.
I hope I've given enough info for you boffins out there !!

Cheers
Rob

 

[Leon]

Hi to all.
How can one determine the impedance of a pcb track.
The track is about 5cm long , 1.7mm wide , grounded on one end. There
is
no ground plane.All the searches I've done come up with microstrip
calculations which don't seem
to cater for this geometry.
The track acts as an antenna , so I would like to know it's impedance
to design a matching network.
This RF stuff is not my strong point , so any pointers would be great.
I hope I've given enough info for you boffins out there !!

Cheers
Rob

You'll have to use antenna modeling software on it. Try MMANA, it's
free.

Leon

 

[Leon]

Hi to all.
How can one determine the impedance of a pcb track.
The track is about 5cm long , 1.7mm wide , grounded on one end. There
is
no ground plane.All the searches I've done come up with microstrip
calculations which don't seem
to cater for this geometry.
The track acts as an antenna , so I would like to know it's impedance
to design a matching network.
This RF stuff is not my strong point , so any pointers would be great.
I hope I've given enough info for you boffins out there !!

Cheers
Rob

Further to my previous post, if it is a 1/4 wavelength long at 433
MHz, you could just assume that the impedance is 50 ohms.

Leon

 

[[email protected]]

Further to my previous post, if it is a 1/4 wavelength long at 433
MHz, you could just assume that the impedance is 50 ohms.

Leon

Thanks , I'll have a look.
It's not 1/4 wavelength. That would be closer to 17.3cm

Cheers
Rob

 

[Wimpie]

Hi to all.
How can one determine the impedance of a pcb track.
The track is about 5cm long , 1.7mm wide , grounded on one end. There
is
no ground plane.All the searches I've done come up with microstrip
calculations which don't seem
to cater for this geometry.
The track acts as an antenna , so I would like to know it's impedance
to design a matching network.
This RF stuff is not my strong point , so any pointers would be great.
I hope I've given enough info for you boffins out there !!

Cheers
Rob

Hello Rob,

I assume that there is a return path (as one end is connected to
ground). The impedance (in particular the real part of it) depends
heavily on the return path and path of trace.

Maybe you can describe the geometry so that someone can do a ball park
calculation or EM simulation.

Best regards,

Wim
PA3DJS
www.tetech.nl
without abc the address is correct.

 

[[email protected]]

Hello Rob,

I assume that there is a return path (as one end is connected to
ground).  The impedance (in particular the real part of it) depends
heavily on the return path and path of trace.

Maybe you can describe the geometry so that someone can do a ball park
calculation or EM simulation.

Best regards,

Wim
PA3DJSwww.tetech.nl
without abc the address is correct.

One side of the track is connected to gnd(ground plane) , the other
side is where the "drive " would come from.

 

[TT_Man]

Hi to all.
How can one determine the impedance of a pcb track.
The track is about 5cm long , 1.7mm wide , grounded on one end. There
is
no ground plane.All the searches I've done come up with microstrip
calculations which don't seem
to cater for this geometry.
The track acts as an antenna , so I would like to know it's impedance
to design a matching network.
This RF stuff is not my strong point , so any pointers would be great.
I hope I've given enough info for you boffins out there !!

Cheers
Rob

I thought the antenna trace comes direct from the RF output and is open
ended. On mine, there is a gound plane under the first part of the track (
curved) then it goes straight.( for 1/4 length). Works fine at 868 Mhz.

 

[Tom Bruhns]

I think you need to post a picture.  What it's connected to is
important, of course, but what it's close to is also quite important.

5cm long to ground is going to look like an inductor, but you've also
got whatever your ground return trace is, too.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says..
See details athttp://www.wescottdesign.com/actfes/actfes.html

I'll second the "we need a picture," or even better, an accurately
dimensioned drawing. It's not the impedance of "a PCB track," it's
the impedance of an antenna which consists of a PCB trace, "ground"
plane, dielectrics, and perhaps a bunch of other stuff.

Can't you just measure it? But of course, even there you'll find
pitfalls: you need to make sure your connections between the antenna
and the network analyzer don't add significantly to the antenna
structure.

Cheers,
Tom

 

[[email protected]]

I'll second the "we need a picture," or even better, an accurately
dimensioned drawing.  It's not the impedance of "a PCB track," it's
the impedance of an antenna which consists of a PCB trace, "ground"
plane, dielectrics, and perhaps a bunch of other stuff.

Can't you just measure it?  But of course, even there you'll find
pitfalls:  you need to make sure your connections between the antenna
and the network analyzer don't add significantly to the antenna
structure.

Cheers,
Tom

I don't have any equipment that can measure it. 60Mhz scope and 1G
spectrum analyser.
I'll try and get a picture.