Design delay circuit

[Pazzeo]

Hi all i have a problem. In my circuit i have intoduced a delay time with a
coaxial cable, the delay time is approximately 30 ns. My question is: Is
there a solution without a coaxial cable??
Please help me I'm deprived of hope!!
Thanks very much!
Bye Bye
Pazzeo

 

[Andrew Holme]

Pazzeo wrote:

Hi all i have a problem. In my circuit i have intoduced a delay time
with a coaxial cable, the delay time is approximately 30 ns. My
question is: Is there a solution without a coaxial cable??
Please help me I'm deprived of hope!!
Thanks very much!
Bye Bye
Pazzeo

You can get passive LC delay lines in 8 pin DIL packages.

http://www.google.co.uk/search?q=passive+delay+line

 

[Joerg]

Bongiorno Pazzeo,

Passive delay lines are one solution but they tend to be a bit costly. Another solution is a simple LC delay. It depends what you want to delay. If it's digital then an LC followed by a Schmitt trigger would be what I would do.

If it is high frequency analog stuff then you would have to crack out the Williams Filter Design Handbook to design it with discrete parts. Or, as Andrew suggested, use delay lines. Keep in mind that delay lines need to be carefully matched for their characteristic impedance. Otherwise their frequency response looks like a pretzel. I usually drive them with a current source and terminate the end of the line with whatever the data sheet says it wants.

Just don't expect a 30nsec delay line to give you hundreds of MHz of bandwidth. If you need large bandwidth the coax is the ticket. You could use a small one and curl it up if space is a problem.

Regards, Joerg

http://www.analogconsultants.com

 

[Jim Thompson]

On Wed, 12 Jan 2005 00:50:03 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Bongiorno Pazzeo,

Passive delay lines are one solution but they tend to be a bit costly. Another solution is a simple LC delay. It depends what you want to delay. If it's digital then an LC followed by a Schmitt trigger would be what I would do.

If it is high frequency analog stuff then you would have to crack out the Williams Filter Design Handbook to design it with discrete parts. Or, as Andrew suggested, use delay lines. Keep in mind that delay lines need to be carefully matched for their characteristic impedance. Otherwise their frequency response looks like a pretzel. I usually drive them with a current source and terminate the end of the line with whatever the data sheet says it wants.

Just don't expect a 30nsec delay line to give you hundreds of MHz of bandwidth. If you need large bandwidth the coax is the ticket. You could use a small one and curl it up if space is a problem.

Regards, Joerg

http://www.analogconsultants.com

Of course, it's only about 20' of coax ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Joerg]

Hi Jim,

Of course, it's only about 20' of coax ;-)

Yes, but I have seen longer delay lines than that. If you take the good
stuff (mil) it can be a tiny coax and then the rolled up package isn't
so bad. Some lowpass effect can be compensated so even lossier stuff can
suffice if $$$ is an issue.

Once I did that the poor man's way. I cracked out the old Motorola MECL
book to calculate the Z and meandered the line between VCC and GND
planes. Worked great and cost next to nothing. It just looked odd, but
only on the plotted layout.

Regards, Joerg

http://www.analogconsultants.com

 

[Joerg]

Hi Jim,

Can you just roll it up on a cylindrical form, or are there coupling
issues to watch for?

I meandered it and used ground fingers plus vias in between. That scheme
should be doable as a coil as well.

Regards, Joerg

http://www.analogconsultants.com

 

Jim Thompson wrote:

Just don't expect a 30nsec delay line to give you hundreds of MHz of


Of course, it's only about 20' of coax ;-)

Where I work we have several rooms (one in QA, at least one in
engineering) wired for testing our protocols over very long cable runs,
to flush out timing issues like this. The larger of these rooms has I
think 10,000' of cable with taps every 150 feet. It looks very
impressive because it lives in a huge cable run on the ceiling - it
looks like the data feed to some massive supercomputer on the other
side of the wall. Only this computer is always the OTHER side of the
wall, no matter which side you're on - because this cable goes nowhere
and does nothing

The smaller room has only 5,000' of cable. It's wrapped in a neat
spiral around the walls of the room (which is small and square).

 

[Pazzeo]

I thank you very much for your help. I need large bandwith but i don't work
with coax because the space is small and i search a method to reduce the
line of delay in microstrip . Another problem is that I want a variable
delay time and with coax i don't do it because i don't do cut and paste the
cable every time. The delay time must be around 30ns!
Bye
Pazzeo





"Joerg" <notthisjoergsch@removethispacbell.net> ha scritto nel messaggio
news:%u_Ed.9576$wZ2.7535@newssvr13.news.prodigy.com...

Bongiorno Pazzeo,

Passive delay lines are one solution but they tend to be a bit costly.
Another solution is a simple LC delay. It depends what you want to delay.
If it's digital then an LC followed by a Schmitt trigger would be what I
would do.

If it is high frequency analog stuff then you would have to crack out the
Williams Filter Design Handbook to design it with discrete parts. Or, as
Andrew suggested, use delay lines. Keep in mind that delay lines need to
be carefully matched for their characteristic impedance. Otherwise their
frequency response looks like a pretzel. I usually drive them with a
current source and terminate the end of the line with whatever the data
sheet says it wants.

Just don't expect a 30nsec delay line to give you hundreds of MHz of
bandwidth. If you need large bandwidth the coax is the ticket. You could
use a small one and curl it up if space is a problem.

Regards, Joerg

http://www.analogconsultants.com

 

[Pazzeo]

Thank you for you help. I will use spirals, but now i have a problem. I
simulate the circuit with ansoft designer. In this software i 'don't know
how insert spirals. Do you know about this? Have you a help for Ansoft??

Bye
Pazzeo