Digital Attenuators - your experiences , suggestions and comments

[noreply]

For the forum members who are involved with testing medium to moderate signal levels - its mandatory to have some form of attenuation between the signal and your 'expensive' test equipment 

I would like to share some experiences, suggestions and comments here

To kick-off

I am awaiting delivery of this device ...

Digital Attenuator Module, OLED Display 6G Digital Programmable Attenuator 30DB Step 0.25DB RF Module

It costs £36 on Amazon.co.uk

When I receive the actual device I will put it through its paces and publish my findings here


Please share any digital attenuator experiences you may have had 

[Bassman59]

For the forum members who are involved with testing medium to moderate signal levels - its mandatory to have some form of attenuation between the signal and your 'expensive' test equipment 

I would like to share some experiences, suggestions and comments here

To kick-off

I am awaiting delivery of this device ...

Digital Attenuator Module, OLED Display 6G Digital Programmable Attenuator 30DB Step 0.25DB RF Module

It costs £36 on Amazon.co.uk

When I receive the actual device I will put it through its paces and publish my findings here

Please share any digital attenuator experiences you may have had 

Wow, I remember when I worked with L-band microwave stuff, you couldn't buy a simple directional couple for £36.

I wonder how this will measure for flatness, accuracy of attention, all of it.

[joeqsmith]

I wasn't able to sort out if you can program it from the USB or using the TX/RX pins.   Looking forward to seeing your review.   There appears to be some data here:

https://www.aliexpress.com/item/32818703642.html

[noreply]

I wasn't able to sort out if you can program it from the USB or using the TX/RX pins.   

Not sure myself at this moment in time - but I suspect with all the test gear I have already accumulated - I will be able to debug any comms with this device 

I suspect the 'attenuator' IC is an Analog Devices Peregrine Semiconductor Corporation component - so should be able to get detailed data on it 


Here is something you could try ...


The communication baud rate is 115200bps.

The command is limited to lowercase letters a ~ z, numbers 0 ~ 9, and the end symbol of each command is a newline character (hex represents "0x0a "Or '/ n')

Communication commands include three types of commands: w command
wv0 Command: Set output attenuation.
The format is: wv0xxxx + 0x0a, a total of 8 bytes;
where "xxxx" is the attenuation value represented by 4 numbers, for example: wv01150 n: indicates that the write attenuation is: 11.5DB (the maximum attenuation is: 0-6350 , With a step of 25). Converted to hexadecimal: 0X77 0X76 0X30 0X31 0X31 0X35 0X30 0X0a

Versions after 2019 with a return value: "ok r n" text format value returned after receiving the correct data.

[joeqsmith]

Sounds great. 

Do you have access to a VNA that you can use to measure it?   

[noreply]

Sounds great. 

Do you have access to a VNA that you can use to measure it?

Something better a Siglent SVA1032X - which started life as a SSA3021x Plus originally 

So will be able to do some accurate attenuation tests - but unfortunately only to 3.2GHz 

But for doing comms debug will use the Rigol MSO5000 - can directly decode the data.

Lets hope that the Peregrine Semiconductor Corporation datasheet will give you more details on how to communicate with the device 

[noreply]

I just did some digging - its NOT an AD semiconductor ...

Its most likely a device made by Peregrine Semiconductor Corporation - like this one ;-

https://www.psemi.com/pdf/datasheets/pe43711ds.pdf

In Summary ..

The PE43711 is a 50Ω, HaRP™ technology-enhanced, 7-bit RF digital step attenuator (DSA) that supports a
broad frequency range from 9 kHz to 6 GHz. It features glitch-less attenuation state transitions and supports
1.8V control voltage and an extended operating temperature range to +105 °C, making this device ideal for
many broadband wireless applications.
The PE43711 is a pin-compatible upgraded version of the PE43502, PE43503, PE43602 and PE43702. An
integrated digital control interface supports both Serial and Parallel programming of the attenuation, including
the capability to program an initial attenuation state at power-up.
The PE43711 covers a 31.75 dB attenuation range in 0.25 dB, 0.5 dB and 1 dB steps. It is capable of
maintaining 0.25 dB monotonicity through 4 GHz, 0.5 dB monotonicity through 5 GHz and 1 dB monotonicity
through 6 GHz. In addition, no external blocking capacitors are required if 0 VDC is present on the RF ports.
The PE43711 is manufactured on pSemi’s UltraCMOS® process, a patented variation of silicon-on-insulator
(SOI) technology on a sapphire substrate

[joeqsmith]

From the datasheet, seems like the TX/RX tie to the micro, then that controls the attenuator.   If it does and they release details on the protocol, that would make it more useful.  Even better if you can run control it right from the USB port.     

I saw that Psemi and thought Pericom Semiconductor.  I've never heard of Peregrine.   

Depending how many people are making it, once you have it you may want to post a link for the one you purchased.   I would imagine the board will make a fair bit of difference.  Once you know what part it is, it may be interesting order the manufactures eval board to compare its performance.   
 

[noreply]

... its a trademarks of pSemi Corporation

I just cut / pasted the name from the datasheet 

.. yes micro has its 'own' command language & controls the simple interface to the attenuator IC's internal register

.. you should be able to issue commands (see datasheet) to the command register on the chip - so be able to control the attenuation settings - the truth tables for attenuation levels are shown in the data sheet

[noreply]

.. just got notification - my device arrives today 

[jjoonathan]

2 years ago these were pretty rough.

https://photos.app.goo.gl/fdysAuMYQ8JX3yY86

Here's hoping they've improved!

[edigi]

https://www.psemi.com/pdf/datasheets/pe43711ds.pdf

Another (more likely) option is this:
https://www.psemi.com/pdf/datasheets/pe43703ds.pdf

I have a probably older/less capable variant (PE43702 based, without OLED but with micro switches) and I wouldn't say it's bad. I've tested it with the 1.5GHz NanoVNA (the older design, I've still not received the new 3GHz variant so I cannot retest and I'm too lazy to check it with the SSA).
Attenuation is roughly between 2-3dB when no attenuation is set, reflected power is roughly -20dB.
With max attenuation set it's roughly 32dB more (within spec) and reflected power is roughly -30dB.
(All of the above with NanoVNA, calibration including the wires.)
Naturally a decent VNA would allow more precise measurements, but I didn't need that.

If I remember correctly from Dave's review of the Siglent SSA (too lazy to search it now), Siglent is also using some PE variant in their SSA...

I still would be afraid to use it before some expensive equipment. Although the datasheet states that it powers up with max attenuation my variant without power is 10dB less than max (OK it's not the same as with power but still).

I've thought that only the more expensive OLED variants can take commands from the USB side (as I didn't see this advertised for the cheaper variants) but if this is not the case it's pretty good. But then it's another issue still how commands can be given without USB unless a separate chip is used for the conversion and the micro has serial input for that which makes it very easy.

[noreply]

Today, my Digital Attenuator finally arrived 


I was eager to start to put it through its paces – BUT this was unfortunately not possible 


My device was a DOA 


First, a visual inspection, after opening the package – see attached photos – showed some ‘crushing’ due to poor packaging.

Fortunately this was ‘fixable’ – I managed to straighten the microUSB connector and the interconnecting header top pins, in essence enough to at least check-out the device and power it up.

After connecting the microUSB cable – and flicking the ON/OFF switch to ‘ON’ the power LED illuminated – BUT the OLED display was dead. 

Despite the above – I was still keen to see if there was ‘functionality’ without the display – so connected to signal generator and set at 1GHz at 0dBm – the output connected to the SVA and we get the attenuation ‘stuck’ at -12dB – despite button presses – nothing working. 


Next step was to check the ‘insides’ just in case there was something obvious that could be fixed.

Again – nothing to see here – I checked the voltages – got the 3.3V all ok

Well – I guess I could start to debug with the MSO – but , nah.. what’s the point of paying top $ (bought via Amazon for speedy delivery and peace of mind if return necessary) and then spending half a day trying to fix something which should be working in the first place 


I guess you have to expect hit and miss for items shipped from China – especially these cheap devices which are made without any QA


Not sure if I’m going to get a replacement unit – not keen to wait another 6 weeks 


So my contribution on a full review of this digital attenuator has just ended – before it even started 


Hope your experiences had more mileage than my short lived one just now 

[noreply]

2 years ago these were pretty rough.

https://photos.app.goo.gl/fdysAuMYQ8JX3yY86

Here's hoping they've improved!

WOW ... that's not very good at all 

From the photos - it looks like the identical device

AND

Looking at the IC data (if indeed it used the psemi device) - it should definitely have better performance

Not sure if the 'soldering' or PCB tracks (dirt or any other debris) might have anything to do with your poor response 

Its a pity , I could not do some testing myself - I guess DOA means DEAD

BUT

Having said this, part of me thinks if I would get similar or worse results - perhaps getting a DOA and returning it immediately might have spared me having an ineffective device, when wanting to use it for precision attenuation(s) 

[edigi]

I remembered wrong in my earlier post, it's not the Siglent SSA but the lowest frequency SVA that uses these PE attenuators.
https://youtu.be/HxBcQDooAYs?t=1491

These OLEDs are bad combination with the heavy stuff from shipping perspective. It's too bad that you can't make the review now.

[joeqsmith]

That's too bad.   If they send you another and allow you to keep the bad one, maybe you could control the attenuator directly.   At least it would let you try it out.

[noreply]

That's too bad.   If they send you another and allow you to keep the bad one, maybe you could control the attenuator directly.   At least it would let you try it out.

Yeah that would be nice - but bought it through Amazon - so they want you to return the item - you don't deal with the supplier in China directly.

The good thing was that Amazon had stock in their local warehouse - so my delivery was only a few days - hence my purchase.

Now there is no more stock - so must ship from china and the 6 weeks shipping.

Good thing about Amazon - there is no arguing - if not happy / DOA - you get free return and full refund

[Bud]

I will sooner believe I am the Pope than that gizmo has a genuine Peregrine chip in it.

[noreply]

I will sooner believe I am the Pope than that gizmo has a genuine Peregrine chip in it.

Well, we could do some 'critical analysis'

These devices 'retail' for as little as $25, so it the genuine 'chip' retails for >$25 alone - then these guys are busted and you are DEFINATELY not the pope.

At least wen looking at the 'pinouts' on the genuine datasheet - thy are the SAME as used on the physical board / chip (see previous photos) - but since they also scratched off the markings on the chip - most likely a clone chip if they do have clones of this device?

the post from jjoonathan - with his poor results for this device - which are worse than the genuine spec sheet - also confirms your theory of not genuine peregrine chip

[tv84]

First, a visual inspection, after opening the package – see attached photos – showed some ‘crushing’ due to poor packaging.

Many of your photos are f... up by the forum!    They have nothing to do with the thumbnails!

I don't understand what is happening recently in the forum regarding the attachments...

[noreply]

First, a visual inspection, after opening the package – see attached photos – showed some ‘crushing’ due to poor packaging.

Many of your photos are f... up by the forum!    They have nothing to do with the thumbnails!

I don't understand what is happening recently in the forum regarding the attachments...

Yeah .. seen your comments on this before - BUT It obviously happened above - so thanks for the heads - up.

Hope Dave is doing something about it!

[Nanoman]

I used the PE4312 from PSemi in a project some years back. Nice and cheap and works down to DC if you keep the signal small* ( less than +/-700mV at the switch) but not the best RF match.

*Psemi don't condone using it in this mode but if the input power is limited they work well

[Kean]

I've got an older/cheaper version of this attenuator module that I bought on ebay a few years back from seller elecdesign2015.
It is adjustable in 0.5dB steps 0-31.5dB at 3GHz, but otherwise looks exactly the same.
This one https://www.ebay.com.au/itm/172382353163

Another one to look at is from SV1AFN, which uses the pSemi PE4306 for 0-31dB in 1dB steps.  He sells an SPI attenuator module and OLED/rotary encoder controller separately.
https://www.sv1afn.com/en/products/rf-step-attenuator-spi-module.html

I just received my new nanoVNA V2, but have already broken the screen on it... so I can't play till I get a replacement display module.
If you'd like me to measure anything on either of the above modules, I do also have an xavna unit somewhere, and several SA's with TG (Rigol DSA815 and Signalhound SA44B).

While I've got some gear, I am an really just an RF noob because I've just never had the time to focus and learn more than doing simple measurements.

[noreply]

While I've got some gear, I am an really just an RF noob because I've just never had the time to focus and learn more than doing simple measurements.

Join the club

Its nice to finally be able to do the things you wanted but were unable due to various factors in earlier life timeline.

Hopefully, if lucky, what starts as a hobby can be a source of some $$, if you apply some creative skills and knowhow 

[noreply]

I thought I should make an update post

Guess what?

I was monitoring the 'buy it again' on my Amazon account - and noticed that the ...

Digital Attenuator Module, OLED Display 6G Digital Programmable Attenuator 30DB Step 0.25DB RF Module

was once again available - for next day delivery - from Amazon.

So, since I don't have to wait another 6 week for snail mail from China - I took the plunge to get another module - to complete my testing.

(The original DOA module - is being sent back to Amazon - for refund)

So, I receive the 'new' module - and this time its working - but the 'on off' switch is broken (I still managed to turn it on despite this)

Initial test results will be posted soon.

Unhappy with the broken switch - I decided to yet buy another  (next day delivery) module - hoping it will be fine & I can return the broken switch module.

Today the module arrives (3rd) - I inspect - the swith is OK, I power-up , display is working, settings work - all ok 

So I leave the module 'on' and start writing this post update - then GUESS WHAT??

The display goes blank - module LED still on 

I check and power-on again - just in case - still no display (same as original DOA module) - so I guess its another dead module - but I think the OLED display is what died in the original module and just now in the 3rd replacement module.

So - these modules have bad batch of OLED displays - they keep dying 

I will perform some tests on the working module with broken switch today - and post results.

Unless the performance results are exceptional for this class of device - this module is also going back for a full refund.

I guess its really hit and miss with this devices.

The good thing is that I did not have to wait 6 weeks x 3 - timewise - to come to the same conclusion.

+1 for Amazon return policy and 'prime' shipping