Author Topic: Diode RF limiters  (Read 1549 times)

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Offline ironcurtainTopic starter

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Diode RF limiters
« on: May 25, 2024, 07:50:06 pm »
Anyone around has PCB designs in Kicad and part numbers suitable for building RF diode limiters? Preferably for 10MHz-1GHz.

 

Offline ironcurtainTopic starter

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Re: Diode RF limiters
« Reply #1 on: May 26, 2024, 11:48:56 am »
A good reference so far:

https://www.skyworksinc.com/-/media/SkyWorks/Documents/Products/1-100/200480C.pdf

I'm interested in the 2 stage detector limiter design in page 11. Trying to select parts for decent performance 0-2GHz, for 0dBm and 5dBm.
« Last Edit: May 26, 2024, 11:56:43 am by ironcurtain »
 

Offline RoV

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Re: Diode RF limiters
« Reply #2 on: May 26, 2024, 04:57:50 pm »
Did you give a look at https://www.minicircuits.com/WebStore/Limiters.html?
They are not very costly and they may save you some headache  :palm:
Example https://www.minicircuits.com/WebStore/dashboard.html?model=RLM-33H%2B

Offline ironcurtainTopic starter

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Re: Diode RF limiters
« Reply #3 on: May 27, 2024, 09:47:01 am »
Hola :-)

A more suitable model:
https://www.minicircuits.com/pdfs/CLM-83-2W+.pdf

Or:

The ones with ESD protection explicitly mentioned could also help removing the BAV99 in some front-ends, which I think is likely a worse performer than their solution.

The one you linked has a rated output power (leakage power) of +18 dBm, which will positively destroy most front-ends in many SDR receivers (HackRF being infamously weak/prone to damage at anything near or above 5 dBm).

I would like to come up with my own design (or "our" design). I don't think opening the "can" of the Mini-Circuits parts will reveal much, as they are likely integrated silicon/don't have discrete parts from other manufacturers.

I also looked at Macom parts (MADL-011021-14150T, https://www.mouser.es/datasheet/2/249/MADL_011021_14150T-1316677.pdf) but again the output power is too much (15dBm). They are much cheaper than Marki's or Mini-Circuits.

If I can find a suitable part with 0-5dBm output or a 0 dBm threshold, that would be great.
« Last Edit: May 27, 2024, 09:58:25 am by ironcurtain »
 

Offline kleiner Rainer

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Re: Diode RF limiters
« Reply #4 on: May 27, 2024, 11:13:48 am »
Hello all,

the BAV99-based limiter is not so bad - a comparable circuit is the core of the hp 11947A Transient Limiter that is specified from 9kHz to 200MHz, schematic on page 11:

https://xdevs.com/doc/HP_Agilent_Keysight/HP%2011947%20Operations%20&%20Service.pdf

The one in my lab states: "Max input: +-12VDC / 10kW for 10us"

A homebrew project, complete with measurements is available here:

https://www.w0qe.com/Projects/rf_clipper_2016.html

Both are useful to protect equipment from bursts of power and ESD, especially sensitive spectrum analyzer inputs.

Greetings,

Rainer DG1SMD

 
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Offline ironcurtainTopic starter

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Re: Diode RF limiters
« Reply #5 on: May 27, 2024, 11:19:54 am »
I'm interested in a two stage limiter, not a "clipper". They are very different animals (check my linked app. note "PIN Limiter Diodes in Receiver Protectors" by Skyworks). The clipper design is nice and simple for the one you linked, though, but it does not offer the same protection (we want to divert all RF input above the threshold to ground, more or less).

 

Offline kleiner Rainer

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Re: Diode RF limiters
« Reply #6 on: May 27, 2024, 12:42:47 pm »
Since you did at first not specify your requirements, I assumed you wanted to protect a sensitive RF input - in this case, the clipper is the better option. As stated in the paper, the limiter has a widely varying return loss when active - it depends on your application whether you can live with that. My application is EMC work, and there you want a controlled impedance, otherwise your measurements are not acceptable. The other advantage of the clipper in my application is that it does not suffer from "spike leakage" (figure 12) and is not frequency sensitive (PIN diode carrier lifetime!). Especially when measuring the EMC behaviour of mains circuits or SMPS, you want something that limits the maximum input voltage to your input regardless of frequency or source impedance. The spikes you encounter there are nasty...

Greetings,

Rainer DG1SMD






 

Offline ironcurtainTopic starter

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Re: Diode RF limiters
« Reply #7 on: May 27, 2024, 12:50:48 pm »
Hi,

I did mention the two stage limiter:

Quote
"I'm interested in the 2 stage detector limiter design in page 11. Trying to select parts for decent performance 0-2GHz, for 0dBm and 5dBm."

:-)

The use case is not EMC for me, it is indeed to protect a sensitive RF front-end for a SDR receiver (not hamradio equipment also, so it is not designed to tolerate inputs higher than 5-10dBm, 5dBm seems to be the sweet spot for most of the hobbyist-accessible SDR devices around, including the ubiquitous HackRF).

We can talk EMC later in a separate thread, I intend to build two LISNs, one for DC and another for AC, for some future work. I did some volunteer work for the local "ARRL" analyzing some light fixtures sold at scale (they function as fantastic wideband jammers especially at HF) years ago.

Controlled impedance is not necessarily crucial for my use case, obviously you don't want to completely mismatch the entire setup since that will cause loss. I need fast action/clamping as soon as the threshold is reached. Low part count is also ideal. I might design afterwards a combined PCB with a LNA immediately behind the limiter, and perhaps an adjustable attenuator). For now I want to keep it simple. People are being charged quite a bit, even from Aliexpress, with limiters that have dubious design and components.

 

Offline MartinL

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Re: Diode RF limiters
« Reply #8 on: May 27, 2024, 09:09:48 pm »
Mike Ossmann has done some work in this area as part of our URTI project. Specifically he was evaluating limiters with a Schottky diode anti-parallel to a PIN diode. This is a topology with several advantages, explored in a number of publications by Chin-Leong Lim.

Notes and references on this work can be found in this section of the 2023-06-02 URTI project report.

VNA test results can be seen in this lab report, and the KiCad designs associated with this work are here.
 
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Offline RoV

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Re: Diode RF limiters
« Reply #9 on: May 28, 2024, 07:43:41 pm »
+5 dBm are only 0.56 V peak on 50 ohm, it's difficult to have an hard limit at this level with diodes. I think a schottky+PIN design would just kick-in, its hard limit would be higher. Perhaps you can use two anti-parallel schottkies as a clipper, but be prepared to have plenty of distortion, because their knee is very gradual and they will distort even much weaker signals, producing mostly odd harmonics.
You could perhaps try to slightly forward-bias the PIN in the schottky+PIN design. Bias should be low impedance, otherwise strong signals would change it by rectification.
 
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Offline glenenglish

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Re: Diode RF limiters
« Reply #10 on: June 06, 2024, 08:13:04 pm »
Suggest planning for a limit of around +10dBm. That is more practical
the CLA4605-***  devices from skyworks have a useful package, also, read the app notes. Understand the operation, exactly how they work.
I design the input stage (transformers, termination) of my SDRs for around +13 peak (0dBfs) , so the limiter has a chance of doing something.
In order for high IP3 to be able to be realised , any amplifiers ahead will need P1 of around +16 to +20, which means you certainly need a limiter. I see this error in lots of designs.    If using  MMICs , some are much better than others like ADF5535 beats the hell out of MCL for IP3. But at low freqs, transformer feedback discrete push pull amps are far superior in IP3, IP2,
Do the sims and measure what happens when the amplifier proceeding the limiter sees limiter diode action. It might not like it.
If narrowband, a 90 deg network between the amplifier device and the limiter may assist stability.



 
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