In microwave frequencies, do you use a circulator when you need a (near) perfect diode?





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I am confused with the "diode concept" in microwave frequencies. As far as I could read, I found that even small signal Schottky diodes have a non negligible capacitance, that may perturb the signal from 1GHz and more (well I've seen a few that work up to 20GHz but they require special mounting etc.).
On the other hand, there are circulators with operating frequencies from 1GHz to 40GHz, and I think they can be used as a diode since a signal entering at port 1 output at port 2 but the inverse path is blocked. Hence my question: is it what microwave engineers use?










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    3












    $begingroup$


    I am confused with the "diode concept" in microwave frequencies. As far as I could read, I found that even small signal Schottky diodes have a non negligible capacitance, that may perturb the signal from 1GHz and more (well I've seen a few that work up to 20GHz but they require special mounting etc.).
    On the other hand, there are circulators with operating frequencies from 1GHz to 40GHz, and I think they can be used as a diode since a signal entering at port 1 output at port 2 but the inverse path is blocked. Hence my question: is it what microwave engineers use?










    share|improve this question









    $endgroup$















      3












      3








      3





      $begingroup$


      I am confused with the "diode concept" in microwave frequencies. As far as I could read, I found that even small signal Schottky diodes have a non negligible capacitance, that may perturb the signal from 1GHz and more (well I've seen a few that work up to 20GHz but they require special mounting etc.).
      On the other hand, there are circulators with operating frequencies from 1GHz to 40GHz, and I think they can be used as a diode since a signal entering at port 1 output at port 2 but the inverse path is blocked. Hence my question: is it what microwave engineers use?










      share|improve this question









      $endgroup$




      I am confused with the "diode concept" in microwave frequencies. As far as I could read, I found that even small signal Schottky diodes have a non negligible capacitance, that may perturb the signal from 1GHz and more (well I've seen a few that work up to 20GHz but they require special mounting etc.).
      On the other hand, there are circulators with operating frequencies from 1GHz to 40GHz, and I think they can be used as a diode since a signal entering at port 1 output at port 2 but the inverse path is blocked. Hence my question: is it what microwave engineers use?







      diodes microwave






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      share|improve this question




      share|improve this question










      asked 2 days ago









      MikeTeXMikeTeX

      657416




      657416






















          3 Answers
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          6












          $begingroup$

          Diodes and circulators are totally different components.



          Microwave engineers use one when they want one, the other when they want the other. They use diodes when they want to rectify signals, and circulators when they want to isolate ports.






          share|improve this answer









          $endgroup$













          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            2 days ago






          • 1




            $begingroup$
            @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
            $endgroup$
            – The Photon
            2 days ago












          • $begingroup$
            OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
            $endgroup$
            – MikeTeX
            2 days ago



















          3












          $begingroup$

          In short, no, one would not use a circulator when one needs a diode.



          A circulator can't perform the same functions diodes can. For example, diodes can be used as an RF switch (pass RF when supplied with a DC bias, block RF and leave a high-impedance output when no bias is applied), which a circulator cannot do.






          share|improve this answer









          $endgroup$













          • $begingroup$
            This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
            $endgroup$
            – MikeTeX
            2 days ago












          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            yesterday



















          3












          $begingroup$

          At microwave frequencies one might use a biased pin diode in a duplex port to protect (Block) the Rx LNA input while Tx out on the same coax to the antenna.



          However, using a Circulator is somewhat like a Directional coupler except it is undirectional ( in only one direction of the circle ) or "non-reciprocal" feeding only to the next port.



          They are made in 3 port and 4 port version.





          • To achieve isolation and amplification one might choose tunnel diodes or Gunn diodes which due to their avalanche effects have a Negative Differential Resistance




            • Then the diode can block the Rx during Tx mode and amplify during Rx mode with proper bias on the diode in a circulator. This is a half-duplex Rx/Tx microwave method used for higher bands of microwave.




          enter image description here[Ref]2



          enter image description hereRef



          enter image description hereRef






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            2 days ago












          Your Answer





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          3 Answers
          3






          active

          oldest

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          3 Answers
          3






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          6












          $begingroup$

          Diodes and circulators are totally different components.



          Microwave engineers use one when they want one, the other when they want the other. They use diodes when they want to rectify signals, and circulators when they want to isolate ports.






          share|improve this answer









          $endgroup$













          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            2 days ago






          • 1




            $begingroup$
            @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
            $endgroup$
            – The Photon
            2 days ago












          • $begingroup$
            OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
            $endgroup$
            – MikeTeX
            2 days ago
















          6












          $begingroup$

          Diodes and circulators are totally different components.



          Microwave engineers use one when they want one, the other when they want the other. They use diodes when they want to rectify signals, and circulators when they want to isolate ports.






          share|improve this answer









          $endgroup$













          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            2 days ago






          • 1




            $begingroup$
            @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
            $endgroup$
            – The Photon
            2 days ago












          • $begingroup$
            OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
            $endgroup$
            – MikeTeX
            2 days ago














          6












          6








          6





          $begingroup$

          Diodes and circulators are totally different components.



          Microwave engineers use one when they want one, the other when they want the other. They use diodes when they want to rectify signals, and circulators when they want to isolate ports.






          share|improve this answer









          $endgroup$



          Diodes and circulators are totally different components.



          Microwave engineers use one when they want one, the other when they want the other. They use diodes when they want to rectify signals, and circulators when they want to isolate ports.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 2 days ago









          Neil_UKNeil_UK

          79k285182




          79k285182












          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            2 days ago






          • 1




            $begingroup$
            @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
            $endgroup$
            – The Photon
            2 days ago












          • $begingroup$
            OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
            $endgroup$
            – MikeTeX
            2 days ago


















          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            2 days ago






          • 1




            $begingroup$
            @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
            $endgroup$
            – The Photon
            2 days ago












          • $begingroup$
            OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
            $endgroup$
            – MikeTeX
            2 days ago
















          $begingroup$
          So, what do you do if you need to rectify signals at 40GHz?
          $endgroup$
          – MikeTeX
          2 days ago




          $begingroup$
          So, what do you do if you need to rectify signals at 40GHz?
          $endgroup$
          – MikeTeX
          2 days ago




          1




          1




          $begingroup$
          @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
          $endgroup$
          – The Photon
          2 days ago






          $begingroup$
          @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
          $endgroup$
          – The Photon
          2 days ago














          $begingroup$
          OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
          $endgroup$
          – MikeTeX
          2 days ago




          $begingroup$
          OK. Just the answer to the question. This helped me to understand what a circulator really is. The other answers give complements though.
          $endgroup$
          – MikeTeX
          2 days ago













          3












          $begingroup$

          In short, no, one would not use a circulator when one needs a diode.



          A circulator can't perform the same functions diodes can. For example, diodes can be used as an RF switch (pass RF when supplied with a DC bias, block RF and leave a high-impedance output when no bias is applied), which a circulator cannot do.






          share|improve this answer









          $endgroup$













          • $begingroup$
            This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
            $endgroup$
            – MikeTeX
            2 days ago












          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            yesterday
















          3












          $begingroup$

          In short, no, one would not use a circulator when one needs a diode.



          A circulator can't perform the same functions diodes can. For example, diodes can be used as an RF switch (pass RF when supplied with a DC bias, block RF and leave a high-impedance output when no bias is applied), which a circulator cannot do.






          share|improve this answer









          $endgroup$













          • $begingroup$
            This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
            $endgroup$
            – MikeTeX
            2 days ago












          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            yesterday














          3












          3








          3





          $begingroup$

          In short, no, one would not use a circulator when one needs a diode.



          A circulator can't perform the same functions diodes can. For example, diodes can be used as an RF switch (pass RF when supplied with a DC bias, block RF and leave a high-impedance output when no bias is applied), which a circulator cannot do.






          share|improve this answer









          $endgroup$



          In short, no, one would not use a circulator when one needs a diode.



          A circulator can't perform the same functions diodes can. For example, diodes can be used as an RF switch (pass RF when supplied with a DC bias, block RF and leave a high-impedance output when no bias is applied), which a circulator cannot do.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 2 days ago









          ShamtamShamtam

          2,6031023




          2,6031023












          • $begingroup$
            This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
            $endgroup$
            – MikeTeX
            2 days ago












          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            yesterday


















          • $begingroup$
            This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
            $endgroup$
            – MikeTeX
            2 days ago












          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            yesterday
















          $begingroup$
          This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
          $endgroup$
          – MikeTeX
          2 days ago






          $begingroup$
          This is interesting. I never thought using a diode with a bias tee as a switch. But why not use simply a microwave transistor for this task?
          $endgroup$
          – MikeTeX
          2 days ago














          $begingroup$
          @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
          $endgroup$
          – Shamtam
          yesterday




          $begingroup$
          @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
          $endgroup$
          – Shamtam
          yesterday











          3












          $begingroup$

          At microwave frequencies one might use a biased pin diode in a duplex port to protect (Block) the Rx LNA input while Tx out on the same coax to the antenna.



          However, using a Circulator is somewhat like a Directional coupler except it is undirectional ( in only one direction of the circle ) or "non-reciprocal" feeding only to the next port.



          They are made in 3 port and 4 port version.





          • To achieve isolation and amplification one might choose tunnel diodes or Gunn diodes which due to their avalanche effects have a Negative Differential Resistance




            • Then the diode can block the Rx during Tx mode and amplify during Rx mode with proper bias on the diode in a circulator. This is a half-duplex Rx/Tx microwave method used for higher bands of microwave.




          enter image description here[Ref]2



          enter image description hereRef



          enter image description hereRef






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            2 days ago
















          3












          $begingroup$

          At microwave frequencies one might use a biased pin diode in a duplex port to protect (Block) the Rx LNA input while Tx out on the same coax to the antenna.



          However, using a Circulator is somewhat like a Directional coupler except it is undirectional ( in only one direction of the circle ) or "non-reciprocal" feeding only to the next port.



          They are made in 3 port and 4 port version.





          • To achieve isolation and amplification one might choose tunnel diodes or Gunn diodes which due to their avalanche effects have a Negative Differential Resistance




            • Then the diode can block the Rx during Tx mode and amplify during Rx mode with proper bias on the diode in a circulator. This is a half-duplex Rx/Tx microwave method used for higher bands of microwave.




          enter image description here[Ref]2



          enter image description hereRef



          enter image description hereRef






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            2 days ago














          3












          3








          3





          $begingroup$

          At microwave frequencies one might use a biased pin diode in a duplex port to protect (Block) the Rx LNA input while Tx out on the same coax to the antenna.



          However, using a Circulator is somewhat like a Directional coupler except it is undirectional ( in only one direction of the circle ) or "non-reciprocal" feeding only to the next port.



          They are made in 3 port and 4 port version.





          • To achieve isolation and amplification one might choose tunnel diodes or Gunn diodes which due to their avalanche effects have a Negative Differential Resistance




            • Then the diode can block the Rx during Tx mode and amplify during Rx mode with proper bias on the diode in a circulator. This is a half-duplex Rx/Tx microwave method used for higher bands of microwave.




          enter image description here[Ref]2



          enter image description hereRef



          enter image description hereRef






          share|improve this answer









          $endgroup$



          At microwave frequencies one might use a biased pin diode in a duplex port to protect (Block) the Rx LNA input while Tx out on the same coax to the antenna.



          However, using a Circulator is somewhat like a Directional coupler except it is undirectional ( in only one direction of the circle ) or "non-reciprocal" feeding only to the next port.



          They are made in 3 port and 4 port version.





          • To achieve isolation and amplification one might choose tunnel diodes or Gunn diodes which due to their avalanche effects have a Negative Differential Resistance




            • Then the diode can block the Rx during Tx mode and amplify during Rx mode with proper bias on the diode in a circulator. This is a half-duplex Rx/Tx microwave method used for higher bands of microwave.




          enter image description here[Ref]2



          enter image description hereRef



          enter image description hereRef







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 2 days ago









          Sunnyskyguy EE75Sunnyskyguy EE75

          71.4k227103




          71.4k227103








          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            2 days ago














          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            2 days ago








          1




          1




          $begingroup$
          Thank you for this nice answer, full of side information.
          $endgroup$
          – MikeTeX
          2 days ago




          $begingroup$
          Thank you for this nice answer, full of side information.
          $endgroup$
          – MikeTeX
          2 days ago


















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