QUESTION

Question

Hello,

I am planning on using the SR42W001 with a u-blox EMMY-W161 module and had some questions about the design.

1. Matching circuit

a) As of now, I have the values from the reference board (1pF / 15nH / not fitted). Are there better values for my application? The u-blox eval board uses a different configuration with an inductor in series, and a cap and inductor in parallel to create the filter. How do I determine the type and value of these components?

b) How critical is the placement of the matching circuit components? I typically see them arranged so the feed trace is a straight line, but I do not have the space for that. Is my configuration ok?

2. antenna placement
 a) Due to some mechanical constraints, I need to place the antenna in the top right corner of my board. Is there a minimum distance from the antenna to the edge of the board?
 b) How far from the top edge of the board should the antenna be?

3. How much clearance is needed from the bottom of the chip to ground copper?

4. How critical is it to have a coplanar microstrip for the feed trace? I already have an impedance controlled stackup with a standard 50Ω microstrip profile, but can ask for coplanar if it is necessary.

Best,

Anthony

Answer 1

Hi Anthony,

Thank you integrating our antenna into your device. Let's get started:

1a: Your matching values are going to be reliant on the size of your PCB and the housing that surrounds the antenna as well as the whether you go with coplanar waveguide or micro strip line. We do offer services to tune your antenna for you. I always recommend you use the lowest loss matching components possible like Murata GJM for capacitors and LQW for inductors.

1b: The routing of your feed trace looks suitable and I have seen twists and turns on feed traces before that work well.  Typically you want to place the matching circuit close to the antenna like you have it.
2a: The placement of the antenna looks good as well.  The lower yellow line from the edge of the board to the antenna should be now less than 5mm.
2b: The antenna to the top edge of the board can be as small as 0.25mm.

3: The clearance between the antenna and the copper layer should be close to 1mm.

4: The feed trace can be a microstrip line and you have done the right thing by specifying with your PCB manufacturer that it should be a 50 ohm trace.  The only concern would be the connection to ground on pin 2. Passing it through a via adds loss to the system whenever you pass an RF trace through a via but I don't think it will have a significant impact on the antenna performance.

Best regards,

Geoff S.

Comments

Geoff,
Thank you very much for the great answers.

1a) Can you please provide more information on the tuning service you offer? Also, I currently have LQG15HN15NJ02D and GJM1555C1H1R0BB01J for the components
1b) Great, I will not change it

2a) As of now, it is ~4.8mm from the edge of the board, with 4.3mm of ground copper. I will move it left to try to achieve 5mm of ground copper (5.5mm from the board edge)
2b) I have 0.5mm clearance now and will leave it like that

3) Great, I already have 1mm clearance

4) Thank you for the feedback. I have requested that the PCB manufacturer provides me with data for a 50Ω coplanar microstrip so that there aren't any concerns.

Best,
Anthony

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Hi Anthony,

Please contact sales@antenova.com to discuss our tuning services.

Happy to help!!

Best regards,

Geoff S.