QUESTION

Question

We have designed a circuit using the SR4L034 using the values specified in the datasheet. Looking at the antenna using a VNA though it looks like the entire bandwidth is shifted up by ~1GHz looking at the shape of the graphs.

What components would need to be adjusted to shift the frequency?

Answer 1

Hi James,

Are there any metallic components near the antenna that could detune the antenna? what is the ground plane size on the PCB?

Best regards,

Yu Kai Yeung

Comments

There is a modem on the PCB but is outside the range specified in the data sheet (8 degrees)

The PCB is circular and the ground plane is ~60mm in diameter

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Hi James,

The Inversa antenna wouldn't work on this ground plane size, I would suggest our Pharaoh antenna for this. I also see theres a screw hole near the antenna. Did you test the antenna with the screws in place? that will detune the antenna as is it very close.

Best regards,

Yu Kai Yeung

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I tested it with the screws/covers in place. Is there no components that can be changed to get better response from the antenna in the current setup?

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Hi James,

What bands do you need? Do you need certification? Even if the return loss looks good, the efficiency will be poor on a 60mm PCB.

Would you consider a flex antenna like Moseni or Mitis antenna?

Best regards,

Yu Kai Yeung

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We're looking at 3 bands in particular 800MHz, 1.8GHz and 2.6GHz.

Previously we used an antenna very similar to the Mitis and were looking towards a PCB solution instead for ease of manufacture, we still have the capability to use a flex antenna but would only use this as a last resort

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For a PCB solution Pharaoh would be the best for that ground plane size. Do you need certification?

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Apologies I made a mistake earlier, the 60mm is actually the radius of the PCB so full diameter is 120mm which should be sufficient for the Inversa I believe. The only difference from the datasheet recommendation is that the antenna is not on a corner of the board, but the slight bit of PCB overhang has no copper in it.

We've taken some measurements with better equipment and it looks like the higher bands don't have as much of a problem. It's mainly the 900MHz bands where we're struggling. We don't need certification for this PCB

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Hi James,

Would you be able to send me the Gerbers and 3D files so I can review your device and see whats the best way to approach this.

My email is yukai.yeung@antenova.com

Best regards,

Yu Kai Yeung