QUESTION

asked by
M20047-1 antenna matching
Hi,

I built a project that uses Quectel BG96 for GPS and LTE communication. For GPS I use M20047-1 antenna but it looks like something is unmatched while I "see" 11 satellites but can't get a fix. Can you provide information on how to properly test the antenna using a VNA? I found for M20057 here:
https://ask.antenova.com/746/what-im-measuring-when-the-active-antenna-20047-is-powered-on?show=746#q746
so I suppose the procedure is similar, but R1 is on some other place... Thanks

Gabrijel

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3 Answers

answered by
Hi Gabrijel,

What are the C/N values you are seeing from the satellites? If the BG96 module has a LNA it could be a case of the receiver being over saturated as the M20047 has a LNA already.

The process to connect the M0047/57 to the VNA is the same.

Best regards,

Yu Kai Yeung
answered by

Hi Yu Kai Yeung,

As noted in the Quectel BG96 HW design (v1.3, p.54), there’s no integrated LNA.

Initially, I didn’t focus on satellite SNR during testing, assuming a matching issue due to my custom PCB. I’ll retest and monitor SNR more closely.

I powered the antenna using M20047 and Quectel documentation. The only variation was the DC blocking capacitor—100pF (Quectel) vs. 22pF (M20047), for which I followed the M20047 datasheet.

I found VNA connection guidance for the M20057 (linked in my first message), but I’d appreciate help on how to connect a VNA to the M20047.

Kind regards,
Gabrijel

answered by
Hi,

I have tested the device in open sky and got this SNR values:
sat. num/snr: 33/36
sat. num/snr: 38/35
sat. num/snr: 39/34
sat. num/snr: 40/36
sat. num/snr: 42/35
sat. num/snr: 46/34
sat. num/snr: 48/34
sat. num/snr: 51/34

This should be enough to get a clear 3D fix but I waited for half an hour and nothing. Can it be the interference from LTE modem on the same PCB? I have been reading here that, if LTE and GNSS are on the same PCB, better to use M20057-1.

Gabrijel

Meet the moderators

Yu Kai Yeung

Antenna Engineer at Antenova Yu Kai is an antenna expert with over 10 years of experience in the design and testing of antennas. He has experience helping customers with certification testing, combined with his knowledge of RF measurement procedures.

Raymond Lee

Senior Antenna Engineer at Antenova Raymond has a wealth of experience in RF and antennas across many industry sectors. He has over 20 years of experience in electronics design and manufacturing.

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