RF Limiter design or suggestion

[SagSag]

Hey All

I need a very wideband limiter 80-4500MHz.
does anyone have an idea of a commercial limiter I can use? (not connectorized)
on the other hand, can anyone refer me to a good design note?
the simple design I know is of a shunt PIN diode and a shunt inductor as an RF choke but
how can I use a inductor if I have such a big BW?

many thanks,

 

[biff44]

https://www.minicircuits.com/pdfs/RLM-33+.pdf

 

[jiripolivka]

There are several types of limiters: one uses a diode or a pair of diodes in a circuit in which they detect the incoming signal and as they open and saturate, the passing signal is reduced.
Another uses a PIN diode (or two) for the same purpose; PIN diodes allow a higher-level signal to be processed.
Still another type combines a detector and a PIN attenuator to achieve limiting from low to high power levels.

Limiters must be specified not only by input/output power ratio and bandwidth; also their response speed is important. See "www.herotek.com" for more details.

 

[SagSag]

Hey

thank you both, the minicircuits one is not covering the entire band I need but Herotek have some interesting products.
do one of you know about a good design guide if I want to design my own limiter using PIN diodes?

thanks

 

[biff44]

I have never done one that low in frequency before. I suspect there are some tricks to getting the limiter diode to respond the same at microwaves as at 10 MHz. At microwave frequencies, the sine wave is changing so fast that the electrons have trouble going from one side of the I region to the other in that half-cycle. At 10 MHz, they have all the time in the world. That would cause a change in the limiting threshold power, is suspect.

You might try a limiter that has a diode that is biased by a schottky diode...that way the biasing is controlled by the schottky instead of relying on the I region thickness. Just an idea.

The design is simple. Series DC blocking cap at RF input port, shunt PIN diode (with a thin I region), inductor/capacitor bias line, quarterwave transmission line, series blocking cap, schottky rectifying diode feeding the rectified current back thru the bias line to the PIN diode, series blocking cap at RF output port.

 

[SagSag]

I saw a similar design by AVAGO they have a shottky enhanced PIN didoe limiter but it has -5dB VSWR at 4GHz, I was thinking of simulating a PIN diode with a shottky one or with a RF choke like the minicirciuts one, I will probably do that but I though if there is an application note it will make my life easier

 

[jiripolivka]

I am sorry I never designed a limiter as they are commercially available to good specifications.
Your problem may be the wide bandwidth; try to look in Agilent catalog of microwave instrumentation. Also you failed to indicate any power levels you need to process, and response time. All such parameters are important if you want to design a real thing.
PIN diodes are good from > 20 MHz upwards but it will be difficult to design a "flat" limiter over your frequency range.