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IWRL6432: Inquiries about PCB Antenna Patterns

Jack
Mastermind 9075 points
Part Number: IWRL6432

Hi Radar Chams

We have an inquiry from a customer regarding the antenna pattern.


They checked the size of the Tx/Rx antenna in the Reference Design provided by Altium Designer.

It consists of 2 Patch antennas per antenna, and the upper and lower patch sizes were determined to be 1.65(W) x 1.281(L) mm / 1.55(W) x 1.281(L) mm each.

Antenna length of 1.281mm is calculated as resonant frequency of 62GHz and dielectric constant of 3.3.
If the PCB process error is ±0.02mm, the resonance frequency is expected to vary by about 1GHz.

(The followings are obtained as calculation,

Resonance Frequency / Antenna Length
60 / 1.326
61 / 1.303
62 / 1.281
63 / 1.259
64 / 1.238

(approximately) 1 GHz resonance frequency error per 20 um)

When they asked their partner PCB company, they said that the general PCB process error is about 20um...
Is it okay to make it in a general process?

If there is a guide related to this in TI, please share it.

  • 0
    TI__Expert 4448 points

    Hi Jack,

    We are looking into this. We will get back to you early next week.

    -Luke

  • 0 in reply to Luke Rouleau
    TI__Mastermind 25835 points

    Jack,

       This is a very good question, Yes, Antenna design is sensitive to etching tolerance. Tighter the PCB etching tolerance, it's better for the antenna to operate desired frequency. This risk is present for narrow band designs. Antenna would not stop working abruptly at the edge of the band it gradually degrades with lower output power, depending upon the mismatch it would see w.r.t to Antenna ports.

    In this case design is developed such that It would support for wideband approximately ~4GHz. Hence due to etching tolerance if its shifts resonant frequency It still would be within the bandwidth of antenna. 

    You could refer to below appnote on PCB Design, Manufacturing. 

    TI mmWave Radar sensor RF PCB Design, Manufacturing and Validation Guide. 

    https://www.ti.com/lit/an/spracg5/spracg5.pdf

    Thanks and regards,

    CHETHAN KUMAR Y.B.