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In a ceramic patch antenna for GPS if we remove the double sided adhesive tape completely from the bottom we get a metal layer on bottom. What is the purpose of this metal layer ?

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If we mount ceramic patch on a double sided PCB (top layer having ground plane for patch antenna and bottom layer having feed line) feed point goes through the PCB to the bottom layer and soldered there. Bottom of the ceramic patch is fixed to ground plane on the top of PCB through adhesive. So there is not contact of metal layer (which is there at the bottom of ceramic patch) to ground plane on PCB. So what is the purpose of that metal layer ?

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So what is the purpose of that metal layer ?

The metal layer is fundamental to the operation of a patch antenna. Patch antennas use a ground plane and that is what it is.

Bottom of the ceramic patch is fixed to ground plane on the top of PCB through adhesive. So there is not contact of metal layer (which is there at the bottom of ceramic patch) to ground plane on PCB.

Read the data sheet for the patch antenna and follow the instructions contained in that data sheet. It's quite possible that the data sheet will tell you to either provide insulation to the PCB, not route tracks in that area or have exposed copper that can make a contact. This can only be determined by reading the data sheet.

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  • \$\begingroup\$ Thanks for your response. I did not find much information in the datasheet about this. there are total four layers involved 1. At the top of ceramic patch antenna through which feed point starts 2. bottom of ceramic patch antenna on which double sided adhesive tape is fixed 3. top layer (copper) of pcb on which ceramic patch antenna is fixed through adhesive tape 4. bottom layer (copper) of pcb on which feed point is soldered and feed line starts. ceramic dielectric is between layer 1 and 2 adhesive tape is between layer 2 and 3 \$\endgroup\$
    – Rishit
    Jul 3, 2019 at 16:03
  • \$\begingroup\$ I know ground plane is required for patch antenna operation and here in my board layer 3 (top layer of pcb) is the electrical ground of my board and also serving as ground plane for patch antenna. Please help me understand if layer 3 is providing ground plane for patch antenna then what is role of layer 2 which is again not connected to anything (i.e. isolated) \$\endgroup\$
    – Rishit
    Jul 3, 2019 at 16:03
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    \$\begingroup\$ I notice that many antenna data sheets are poor at delivering vital information to a prospective designer and my advice is generally to find an antenna product that has good support documents. \$\endgroup\$
    – Andy aka
    Jul 3, 2019 at 16:19

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