Why are there so many vias on this board?

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I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



Development board on page 8



enter image description here










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    favorite












    I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



    Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



    Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



    Development board on page 8



    enter image description here










    share|improve this question























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



      Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



      Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



      Development board on page 8



      enter image description here










      share|improve this question













      I was looking at the MMZ09312BT1 development board layout and I'm curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as a filter?) ?



      Also it doesn't say explicitly, but is it possible to tell if they have a ground plane on the bottom layer ?



      Datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf



      Development board on page 8



      enter image description here







      rf pcb-design filter






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      share|improve this question










      asked 1 hour ago









      VanGo

      187112




      187112




















          3 Answers
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          3
          down vote













          It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






          share|improve this answer



























            up vote
            3
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            This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



            You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






            share|improve this answer




















            • Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
              – TimWescott
              1 min ago

















            up vote
            2
            down vote













            I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



            What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



            Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



            In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






            share|improve this answer




















              Your Answer





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              3 Answers
              3






              active

              oldest

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              3 Answers
              3






              active

              oldest

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              active

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              active

              oldest

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              up vote
              3
              down vote













              It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






              share|improve this answer
























                up vote
                3
                down vote













                It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






                share|improve this answer






















                  up vote
                  3
                  down vote










                  up vote
                  3
                  down vote









                  It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.






                  share|improve this answer












                  It's a high-frequency RF part. 900MHz = 30cm wavelength. So even a board that's a few cm across is a significant proportion of a wavelength. The vias are to make sure that the top copper is really a ground plane, and not some weird unintended resonator.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered 1 hour ago









                  TimWescott

                  1,23127




                  1,23127






















                      up vote
                      3
                      down vote













                      This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                      You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                      share|improve this answer




















                      • Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                        – TimWescott
                        1 min ago














                      up vote
                      3
                      down vote













                      This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                      You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                      share|improve this answer




















                      • Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                        – TimWescott
                        1 min ago












                      up vote
                      3
                      down vote










                      up vote
                      3
                      down vote









                      This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                      You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.






                      share|improve this answer












                      This is generally referred to as via stitching, and it's generally used to reduce either the high-frequency electrical impedance or the thermal resistance between layers. In this case the reason is certainly RF impedance, however the level of stitching shown is probably overkill even for a 900MHz RF part. However it's easy to do, and doesn't generally hurt anything on a board as sparsely populated as this one.



                      You would need to consult the design documents to determine the stackup details if the layers aren't clearly visible. Often for dev/eval boards the manufacturer will provide a full package of manufacturing documents.







                      share|improve this answer












                      share|improve this answer



                      share|improve this answer










                      answered 32 mins ago









                      ajb

                      2,055516




                      2,055516











                      • Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                        – TimWescott
                        1 min ago
















                      • Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                        – TimWescott
                        1 min ago















                      Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                      – TimWescott
                      1 min ago




                      Easy to do, and for an eval board it's not a bad thing to go overboard on things like that.
                      – TimWescott
                      1 min ago










                      up vote
                      2
                      down vote













                      I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                      What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                      Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                      In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                      share|improve this answer
























                        up vote
                        2
                        down vote













                        I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                        What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                        Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                        In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                        share|improve this answer






















                          up vote
                          2
                          down vote










                          up vote
                          2
                          down vote









                          I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                          What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                          Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                          In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.






                          share|improve this answer












                          I assume there is a copper pour on the top as well, and the bias are stitching the top and bottom planes together. Depending on the frequency of operation, it is possible that the via spacing would help to cancel out emissions. But in this case this effect would not be significant.



                          What I find interesting is the different via spacing and sizes in the input and output sections of the board. These must be significant, probably contributing to impedance coupling or simply filtering. I’d be curious to know the relation between via spacing and wavelength in those sections.



                          Of course, these could also be attachment points to simplify test setups. You might be able to get a straight answer in the manufacturer’s forum.



                          In low frequency boards, you would find prototyping sections that look very similar, but that is clearly not the purpose here.







                          share|improve this answer












                          share|improve this answer



                          share|improve this answer










                          answered 34 mins ago









                          Edgar Brown

                          35211




                          35211



























                               

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