Reccomendations for a digitally controlled variable gain attenuator (1-6GHz)  - Page 1
Forum section: electronics / rf-microwave

author: tem_alThor
author_rank: Newbie
timestamp: March 09, 2025, 08:46:19 am
content: hi! I'm looking for an attenuator whose levels I can control over a communication protocol from a computer. (UART, SPI, ...)Ideally, I'd like it to have a very wide range of attenuations (0-30 dB or more if possible). Any step size below 2 dB would be perfectly fine. Any suggestions?Thanks!

author: joeqsmith
author_rank: Super Contributor
timestamp: March 09, 2025, 04:16:46 pm
content: You do not provide enough detail but a quick search shows:https://www.ebay.com/itm/186064017065https://www.ebay.com/itm/115890985976https://www.ebay.com/itm/326271323912

author: edpalmer42
author_rank: Super Contributor
timestamp: March 09, 2025, 05:04:47 pm
content: Quote from: joeqsmith on March 09, 2025, 04:16:46 pmAnd, if you're willing to create your own driver, options increase and price drops.https://www.ebay.com/itm/156184069676https://www.ebay.com/itm/272857540944https://www.ebay.com/itm/226611421221

author: A.Z.
author_rank: Super Contributor
timestamp: March 09, 2025, 05:44:48 pm
content: what about attenuation pads switched in/out using pin diodes

author: joeqsmith
author_rank: Super Contributor
timestamp: March 09, 2025, 06:21:51 pm
content: Quote from: edpalmer42 on March 09, 2025, 05:04:47 pmKeep in mind, they are asking for 6GHz and the last one you show is only 3GHz. Not sure about the first one you linked.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 09, 2025, 06:34:00 pm
content: Quote from: joeqsmith on March 09, 2025, 06:21:51 pmThose were just examples to illustrate the concept.

author: rfclown
author_rank: Frequent Contributor
timestamp: March 09, 2025, 07:48:05 pm
content: We use pSemi (Peregrine) attenuators on some boards at work for up to 6 GHz. The ones we use are 0.25 dB steps, range 0-31.75 dB. SPI controlled. DFN package.

author: TimFox
author_rank: Super Contributor
timestamp: March 09, 2025, 09:13:06 pm
content: MCL (Mini-Circuits Lab) has a wide range of programmable attenuators:https://www.minicircuits.com/WebStore/Attenuators.html#product_detail_one

author: joeqsmith
author_rank: Super Contributor
timestamp: March 09, 2025, 11:06:34 pm
content: Quote from: edpalmer42 on March 09, 2025, 06:34:00 pmShown is a similar part that was included with some junk I bought. Wired up a few high side drivers to it control it using my LabJack.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: March 10, 2025, 05:14:34 am
content: https://www.mouser.com/c/semiconductors/wireless-rf-integrated-circuits/attenuators/?maximum%20frequency=6%20GHz~~65%20GHz&number%20of%20bits=5%20bit~~7%20bit&rp=semiconductors%2Fwireless-rf-integrated-circuits%2Fattenuators%7C~Number%20of%20Bits%7C~Maximum%20Frequency&sort=pricingAlso generally the step attenuators with feedthroughs are low frequency (about 3 GHz). They have small signal relays inside which switch between SMT resistors.Quote from: joeqsmith on March 09, 2025, 06:21:51 pmI have the first one at home, and it is 3 GHz only I think.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 10, 2025, 01:31:04 pm
content: Quote from: EggertEnjoyer123 on March 10, 2025, 05:14:34 amThe one I have is rated to 2GHz 0-127dB 1dB step.HP has similar with relays that are spec'ed much higher (10s of GHz). HP also offered a controller for these. The O-rings on these fail over time which may need replacing. OP didn't mention GPIB as a possible interface. My guess is they were a one post wonder.https://www.ebay.com/itm/302439496795***To test that old Weinschel part, I just used the Labjack's example digital IO program. Bits 6 and 7 are tied together to get the 64 dB step.Shown with it attached to the LiteVNA64 with attenuator set to 50,70 & 90dB. VNA was not calibrated but normalized at 0dB. While the attenator is rated to 127dB, that's a bit too low for the low cost LiteVNA to measure.

author: TimFox
author_rank: Super Contributor
timestamp: March 10, 2025, 02:12:51 pm
content: Again, the MCL catalog has many items up to 6 GHz, with different steps and maximum values. Not cheap.