QUESTION

Question

I am using Quectel L-70 GPS module with M20057-1 part. My RF path in tuned to 50 ohm Impedance and working very fine with external antenna. We are unable to receive any data ( like HDOP,PDOP,3D Index etc) with this antenna. I have connected 0 ohm res. to AT1 & AT2 pins and followed same layout guidelines as mentioned in datasheet.
https://drive.google.com/drive/folders/11qm0c86zWnheqJYQzjyg3AhMalWw9MmD?usp=sharing

What could be potential issue with this antenna that am not able to receive any data ?

Answer 1

Hello Viral Vasa,

It sounds like your M20057 module is not tuned properly to the GPS frequency. AT2 should start at 1.8nH not a 0 ohm resistor AT1 can stay at 0 ohm and then continue to adjust AT2 until the signal gets better.  There is also a capacitor across pin 4 and pin 6 that can be adjusted up or down a couple of values to see if this improve the TTFF.
If you are still having problems please contact me at techsupport@antenova.com and we can discuss your design further.

Best regards,

Geoff S.

Comments

Hi Geoff S.

Thanks for you response.

we have tried following things:

- Connected L=1.8nH/2.2nH/1.3nH on AT2 pin  and connected 0 ohm on AT1 but same results

- We have u.fl connector also on same RF path and checked with external antenna it worked well.
- I even tried removing series DC blocking cap on RF path and replaced with 0 ohm res. but it has also not helped.
I am now 99.99% sure that my design is good and have no issues. I now only have query regarding this part.
Below are my following queries:

- How could end customer know that this antenna are pre-tested before going to the market ?

- Any test report can antenova share with us ?

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Geoff, I am a satisfied customer of Antenova antennas and use the cellular and GNSS antennas without LNA. My team is now consulting for a customer on the antenna M20057-1. I have looked at the datasheet. At the entrance of the antenna module is an LNA. Then comes a SAW then alignment network and then the antenna. There is no point where I can measure the resonance with the VNA and measure the cable. I could measure the resonance inductively with a loop antenna and then change the two passive components left and right of the antenna module. But that would be Try and Error and not S1P and then determine components by Smith Chart.
How should we now measure the M20057-1 and determine the components? Hoping for a better GNSS signal does not sound very professional. How to measure the resonant frequency of the M20057-1 or other chip loop antennas inductively is described in my IoT M2M Cookbook: http://www.gsm-modem.de/M2M/m2m_iot_cookbook/
The measurement procedure described in the book is used for Antenova Sinica Chip Loop Antenna at my customer's production site. Each board is briefly measured for GNSS centre frequency during the test.