Low Level RF Circulator 500 MHz

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andre_pblima

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Hello everybody,

I'm trying to find a RF circulator surface mount for 500 MHz and that works in low level (more less 5 dBm)
Someone knows a supplier where I can find this kind of circulator.

Thank you
 

andre_pblima said:
Hello everybody,

I'm trying to find a RF circulator surface mount for 500 MHz and that works in low level (more less 5 dBm)
Someone knows a supplier where I can find this kind of circulator.

Thank you
Click to expand...

Raditek San Jose, California
Fairview Microwave
 
A ferrite circulator for this low frequency is large and expensive as the ferrite magnetization is low and requires a thick steel screen. If you wish, you can make an electronic isolator from a MMIC amplifier and attenuator. BY connecting three such devices in a ring you can make a circulator. It can work with up to +10 dBm, has better isolation and bandwidth than the ferrite device, and can be made smaller.
 
Jiripolivka : Could u refer us any material for electronic isolator..??
 

SpaceDust said:
Jiripolivka : Could u refer us any material for electronic isolator..??
Click to expand...

I have built a number of "active" isolators for 400-1800 MHz band, and described one version compared with a ferrite isolator in High Frequency Electronics, Dec.2006. Design Notes, pp. 70-72.

In principle you can use any suitable MMIC covering the frequency band needed, and add before or after it a fixed attenuator to bring the gain down to 0..-1 dB. Check MMIC specification for the best S11 and S22; both can be improved by the attenuator.

As an adjustable 50-Ohm attenuator I used at 500 MHz and up to 4 GHz SMD trimmers, 100-200 Ohms.

- - - Updated - - -

The paper can be viewed for free (only a registration required) at www.highfrequencyelectronics.com.
 
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A passive isolator has a very low insertion loss and noise figure of <0.5dB with a high IP2 and IP3. This allows it to provide a good broadband match with almost no loss of signal or dynamic range. Also it consumes zero DC power. It's isolation will be about 20dB.

With the combination of a amplifier and attenuators of a active isolator you can achieve good isolation and match but with a reduction in dynamic range due to the attenuators, noise contribution of the amplifier and increased intermodulation product levels.

Both approaches have their advantages so which approach to use depends on the application.
 
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