I can't get a transmission line to accept an expression for the delay
Td={expr} Z0=50
Either I'm doing it wrong, or there is a fundamental causality violation or something that doesn't allow it.
Seems like a variable delay line is physically OK, but messy. You can certainly build one in real life.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Td={expr} Z0=50 will only work where "expr" is a fixed amount during the simulation.
If you're trying this inside of a loop, I'm sure it won't work. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Doesn't seem to. I have to build variable delays other ways.
I'm simulating a system that has to run for almost a second, and I'd like the max time step to be 5 ps, something like that. It does crazy things in auto mode, or at 50 ps max step size. At 5 ps, I might learn something useful in a year or two.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
In real life causality is imposed consistently, though, and charge is conserved. With a general expression for the delay, you could do all sorts of acausal things that would cause the simulation to diverge.
Also, in real life changing the delay rapidly will cause a large change in signal amplitude, e.g. if you reduce the capacitance per unit length, the voltage will go up to keep CV constant.
Probably a more physicsy approach would work.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
You might try an all-pass with a multiplier... works, at least for a single-tone sinusoid.
Digital, make an ideal one-shot.
Sometimes a breadboard is faster ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
"physicsy" ?>:-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Yes, like an N-section variable LC, or possibly a big mux and binary-weighted tx lines.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I'm using a simple analog ramp (diode, cap, current source) and a tanh() comparator.
Looks that way. Roughly 1e9 faster. I'm laying out a test board.
I can't post the Top Secret overall circuit, but I'll try to isolate one of the weird-behaving sections, for general amusement.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
The HP8133A pulse generator did that. It's full of inductor-varicap delay lines.
You can buy adjustable delay lines, sort of like wirewound pots with a slider wiper thing. The speed of moving the slider is of course well under the speed of light.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I've used trombone lines a fair amount, back in me yoot.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
That works.
OK ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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