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



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)When (not) to use diode/wired logicWhen/why would you use a Zener diode as a flywheel diode (on the coil of a relay)?How do you determine graded versus abrupt diode junction types?Why we need waveguide in Microwave?Determining which diode I needWhy does microwave test equipment use N connectors?Use diode in parallel to increase currentNeed equivalent for diodeDoes this diode need to be replaced with a higher current rating diode?Use zener diode as regular diode



.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








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












    $begingroup$


    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






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Apr 9 at 17:47









      MikeTeXMikeTeX

      709416




      709416




















          3 Answers
          3






          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
            Apr 9 at 17:55






          • 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
            Apr 9 at 17:56











          • $begingroup$
            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
            Apr 9 at 18:47


















          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
            Apr 9 at 18:50











          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            Apr 10 at 12:30


















          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
            Apr 9 at 18:49











          Your Answer






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          3 Answers
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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
            Apr 9 at 17:55






          • 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
            Apr 9 at 17:56











          • $begingroup$
            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
            Apr 9 at 18:47















          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
            Apr 9 at 17:55






          • 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
            Apr 9 at 17:56











          • $begingroup$
            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
            Apr 9 at 18:47













          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 Apr 9 at 17:52









          Neil_UKNeil_UK

          79.2k285182




          79.2k285182











          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            Apr 9 at 17:55






          • 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
            Apr 9 at 17:56











          • $begingroup$
            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
            Apr 9 at 18:47
















          • $begingroup$
            So, what do you do if you need to rectify signals at 40GHz?
            $endgroup$
            – MikeTeX
            Apr 9 at 17:55






          • 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
            Apr 9 at 17:56











          • $begingroup$
            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
            Apr 9 at 18:47















          $begingroup$
          So, what do you do if you need to rectify signals at 40GHz?
          $endgroup$
          – MikeTeX
          Apr 9 at 17:55




          $begingroup$
          So, what do you do if you need to rectify signals at 40GHz?
          $endgroup$
          – MikeTeX
          Apr 9 at 17:55




          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
          Apr 9 at 17:56





          $begingroup$
          @MikeTeX you can use a very tiny diode. It would be more likely called a "power detector" than a "rectifier".
          $endgroup$
          – The Photon
          Apr 9 at 17:56













          $begingroup$
          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
          Apr 9 at 18:47




          $begingroup$
          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
          Apr 9 at 18:47













          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
            Apr 9 at 18:50











          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            Apr 10 at 12:30















          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
            Apr 9 at 18:50











          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            Apr 10 at 12:30













          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 Apr 9 at 17:53









          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
            Apr 9 at 18:50











          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            Apr 10 at 12:30
















          • $begingroup$
            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
            Apr 9 at 18:50











          • $begingroup$
            @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
            $endgroup$
            – Shamtam
            Apr 10 at 12:30















          $begingroup$
          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
          Apr 9 at 18:50





          $begingroup$
          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
          Apr 9 at 18:50













          $begingroup$
          @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
          $endgroup$
          – Shamtam
          Apr 10 at 12:30




          $begingroup$
          @MikeTeX Cost, control circuitry (two terminal device instead of 3-terminal), switch performance, power handling, etc.
          $endgroup$
          – Shamtam
          Apr 10 at 12:30











          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
            Apr 9 at 18:49















          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
            Apr 9 at 18:49













          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 Apr 9 at 18:16









          Sunnyskyguy EE75Sunnyskyguy EE75

          71.8k227103




          71.8k227103







          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            Apr 9 at 18:49












          • 1




            $begingroup$
            Thank you for this nice answer, full of side information.
            $endgroup$
            – MikeTeX
            Apr 9 at 18:49







          1




          1




          $begingroup$
          Thank you for this nice answer, full of side information.
          $endgroup$
          – MikeTeX
          Apr 9 at 18:49




          $begingroup$
          Thank you for this nice answer, full of side information.
          $endgroup$
          – MikeTeX
          Apr 9 at 18:49

















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