RF delay line for 1.5 GHz to 4 GHz - Page 1
Forum section: electronics / rf-microwave

author: p.francks
author_rank: Newbie
timestamp: March 09, 2023, 08:07:20 pm
content: Dear all,I am looking for a "true time delay" line for microwave pulses from 1.5 GHz to 4 GHz. I am looking for something that is programmable via TTL with switching times < 2 us and a max delay of around 1 ns and a step size < 150 ps. Can you recommend me any module that can do that?Thanks!Peter

author: f4eru
author_rank: Super Contributor
timestamp: March 09, 2023, 09:44:20 pm
content: that spec looks more like a phase shift.What do you try to achieve on which signals ?

author: TimFox
author_rank: Super Contributor
timestamp: March 09, 2023, 10:44:05 pm
content: Here is a survey of programmable delay lines.https://www.everythingrf.com/search/delay-lines/filters?page=1&country=global&stype=;Programmable;

author: p.francks
author_rank: Newbie
timestamp: March 09, 2023, 11:50:57 pm
content: I have (square) pulses at a carrier frequency typically ~2-3 GHz that are ~10 ns long that I want to delay with respect to a second signal issued from the same pulse generator. I want to control the relative timing of these two signals in steps up to 1 ns. The application is for some magnetic resonance experiment.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: March 10, 2023, 12:22:00 am
content: I have made a switchable delay line of 3 ranks of( 1:6 SMA relay, variable lengths of semi rigid coax, 6:1 SMA relay).It has 3 rotary switches and can bring everything between 4 and >100 MHzinto phase quadrature with the help of a power splitter, for measuringphase noise. When the delay line was done, I bought a commercialphase noise analyzer.I also have two motor-driven "Arra, Inc" 9228A-28 delay lines for microwaves.The switching speed of all that is some decades slower than whatyou need.Cheers, Gerhard

author: p.francks
author_rank: Newbie
timestamp: March 10, 2023, 12:24:43 am
content: Thank you very much! Yes, fast switching is really necessary. After some more research, in principle something like this would be idealhttp://www.gigabaudics.com/PADL6/padl6.htmlHowever, this company seems to be inactive by now :'(Therefore I am asking? Do you know any other vendor for such a device?

author: Chat GPT
author_rank: Contributor
timestamp: March 10, 2023, 10:32:02 am
content: One option for a "true time delay" line for microwave pulses in that frequency range could be a digitally programmable delay line (DPDL). These modules are designed to provide precise, programmable delays to microwave signals and are commonly used in radar and communications systems.One example of a DPDL that meets your specifications is the Hittite HMC649LP6. This module operates from 1.5 GHz to 4 GHz and provides a programmable delay range of 0 ns to 7.5 ns with a step size of 150 ps. It has a switching time of 1.5 us and is programmable via TTL.Other manufacturers, such as Mini-Circuits, Analog Devices, and Peregrine Semiconductor, also offer DPDLs that may meet your requirements. It's worth researching and comparing different options to find the best fit for your application.

author: p.francks
author_rank: Newbie
timestamp: March 10, 2023, 05:47:02 pm
content: Thank you very much for the reply. The HMC649LP6 seems to be a phase shifter for 3-6 GHz or did I pick the wrong device?https://www.analog.com/media/en/technical-documentation/data-sheets/hmc649.pdfA more general question: Would a phase shifter also work? From a pure physics point of view a phase shift is a delay but I don’t know how these devices behave for pulses that have a spectral width of here 500 MHz.Thanks for your help again!Peter

author: Marco
author_rank: Super Contributor
timestamp: March 10, 2023, 05:57:04 pm
content: Quote from: llanosperezluis41 on March 10, 2023, 10:32:02 amThis answer feels a bit GPT.

author: gf
author_rank: Super Contributor
timestamp: March 10, 2023, 08:50:55 pm
content: Quote from: p.francks on March 10, 2023, 05:47:02 pmDelay corresponds to a freqency dependent phase shift, i.e. phase(f) = 2*pi*f*delay.

author: p.francks
author_rank: Newbie
timestamp: March 10, 2023, 10:48:33 pm
content: Yes, I get that. Maybe I should have posed the question more specifically: How is a phase shifter actually working? Is it really a delay (then it would be fine) or does it adjust the phase otherwise? Because if it is constant phase regardless of the frequency, then I will run into a problem for a pulse as this consists out of multiple frequencies. Multiple spectral components will then have different delays... Next problem is that a 360° phase shifter is only 500 ns at 2 GHz. So one would need to daisy chain.Nonetheless, I am still on the hunt for something suitable for my delay. I find a lot of research articles but not so many products.

author: Marco
author_rank: Super Contributor
timestamp: March 11, 2023, 09:01:04 pm
content: This Russian pagehas a nice list of products.

author: TimFox
author_rank: Super Contributor
timestamp: March 11, 2023, 09:12:55 pm
content: Quote from: p.francks on March 10, 2023, 10:48:33 pmA delay line has a constant time delay from input to output, and the phase shift for a sine wave will follow the equations given above.A simple example of a constant 1.5 ns delay is approximately 30 cm of RG-58/U coaxial cable, properly terminated.There are other ways to get a phase shift, which will have a different relationship between frequency and phase, such as a filter of various kinds.