Electrical – Ai Thinker A7 module does not lock GPS

All four pins are Ground, and all four pins should be connected to your circuit ground.

It may work if you leave some of the ground connections floating, but you may have reliability issues.

That GPS module does not have separate ground domains. Basically, to reduce the impedance of the ground connection, and possibly for reliability issues, they are using multiple connections from the same ground.

It is in-fact likely that if you use an ohmmeter to measure the resistance between she separate ground connections, you will find they are coupled together within the GPS module as well. You should still ground them all, however.

You'll just need to tell your board house that the antenna trace needs to be 50 ohms @ 1575.42GHz (I assume you're using L1). +/- 10% on the trace impedance should be fine.

You may run into problems with antenna detuning and radiation pattern. These problems can occur due to the case (plastics, screws, etc), board layout (ground plane, stitching vias, antenna placement), and board components (battery clips for example), and anything near the case wherever it's installed/used.

You can assess radiation pattern by putting the unit in an open area for 24 hours and collecting data on altitude, azimuth, and C/No. However, to measure detuning (and check performance of a correcting pi network) you'll need a network analyzer.

I'd recommend working closely with an engineer from both your antenna manufacturer and your GPS receiver manufacturer. For example, they may be able to correct detuning for you on a service basis for a lower cost than buying a network analyzer.

I'm not sure what level of accuracy / acquisition time you'll need, or what environment you'll be in, but I can tell you I know for a fact some $7k+ GNSS-aided INS units use a uBlox MAX7 or MAX8 (which run roughly $10 at quantity).