QUESTION

Question

Dear Antenova Expert,

I am trying to tune SR4C033-R antenna. It is placed in the corner of the PCB, with no copper on any layers below it. See the picture below.

Antenna placement. At the moment, I have mounted just the antenna and the matching circuit. No other components were soldered.

Unfortunately, values from the paragraph 13.1 of its Product Specification does not provide any matching. See Smith chart below.

Smith chart with L1=33nH, C1 n.c., C2 = 0.5pF, L2 n.c., L3=6.8nH.

The measurement was performed using miniVNA Tiny after proper calibration for the RL measurement. RL and SWR graph below.

As you can see the antenna matching does not get even close.

I have tried to simulate a matching circuit with SimNEC, but real life measurements differ significantly from the simulation results.

I attach S11 measurements of the antenna with just the 6.8 nH B.SEL coil (LQG15HN) and all series shorted L1=C3=0R.

S11 file for the antenna with BSEL L=6.8nH.

I have measurements for other values of the matching circuit components if you want me to share.

How to tune the matching circuit to achieve at least decent antenna performance?

Answer 1

Hi,

I think there might be some design issues based on the image you have attached.

At C1 location there are 2 components which splits the signal going into the connector and into the module. The antenna should either only be connected to connector or module not both.

On the transmission line to the connector it seems you have placed another pi matching network, which are not required. The only pi matching network you need are the ones directly below the antenna.

If you have gerbers available I can help take a look at it.

Best regards,

Yu Kai Yeung

Answer 2

Hi,

thank you for your reply.

It is not an issue, it is a variant placement. See the picture below. At C1 location there is a footprint for a 0R resistor, which shares one pin with C1. The resistor is soldered when the SR4C033 antenna is not used, but an external one is used. In the case, C1 and remaining components of the matching circuit are also not soldered. And vice versa - when SR4C033 antenna is used only components of its matching circuit are soldered. In the case the 0R resistor and all the other components of the external antenna output are not soldered.

I will drop the Gerbers on your e-mail: yukai.yeung@antenova.com.