The NanoVNA V2 is a low-cost Vector Network Analyser that can characterize antennas and their performance using Smith charts. We use the NanoVNA V2 to fine-tune the antenna matching circuits in order to attain the maximum gain out of the Radio modules used. This time we give it a try to find the best GPS antenna available with us. For maintaining the same test setup, we used connected all the antennas discussed below to our new IRNSS GPS board - UTRAQ L100 ( https://www.elementzonline.com/u-traq-l100-irnss-navic-gagan-gnss-gps-receiver-module )
Best antennas have lower VSWR and better S11. VSWR of less than 1.5 is a must-have tuning parameter for a good antenna. Also, the lower VSWR means the less reflection power and most of the power is radiated by the antenna if we think of the antenna is a transmitter. This same thing happens when the antenna is used as receiver where most of the radiation in the frequency can be picked up by a well-tuned antenna.
Test equipment used
NanoVNA V2 (S-A-A-2) is a low-cost 3GHz T/R vector network analyzer developed by HCXQS in collaboration with OwOComm. The V2 hardware is a new from-scratch design and is not based on the original NanoVNA by edy555. Compared to the original NanoVNA, V2 does not use harmonics for measurements and achieves a higher dynamic range.
Software used
There are two PC programs compatible with the S-A-A-2. NanoVNA-QT is the native V2 software and allows adjustable sweep points and firmware updating. NanoVNA-Saver was originally developed for the V1 NanoVNA but now also has support for V2.
Visit the following link for more details
https://nanorfe.com/nanovna-v2-software.html
NanoVNA-QT
PC GUI software for NanoVNA V2, based on the software for the xaVNA.
We used the NanoVNA-QT to check the broader range of frequency performance of the Antenna. 1525 MHz to 1650 MHz with continuous frequency sweep mode enabled.
NanoVNA Saver
A multiplatform tool to save Touchstone files from the NanoVNA, sweep frequency spans in segments to gain more than 101 data points, and generally display and analyze the resulting data.
We used the NanoVNA Saver software to analyse the performance in a smaller frequency range between 1570 to 1580 MHz frequency with the single frequency sweep enabled.
Today we are comparing 3 GPS antennas that work with the standard GPS L1 frequency which is 1575.42 Mhz.
Some antennas which we use have a broader tuning range, but we will be focusing on analyzing the performance around L1 frequency only.
1. Antenna from TE Connectivity
A multiplatform tool to save Touchstone files from the NanoVNA, sweep frequency spans in segments to gain more than 101 data points, and generally display and analyze the resulting data.
We used the NanoVNA Saver software to analyse the performance in a smaller frequency range between 1570 to 1580 MHz frequency with the single frequency sweep enabled.
Today we are comparing 3 GPS antennas that work with the standard GPS L1 frequency which is 1575.42 Mhz.
Some antennas which we use have a broader tuning range, but we will be focusing on analyzing the performance around L1 frequency only.
1. Antenna from TE Connectivity
- TE Part Number: 2195774-1
- TE Internal Description: Ext Antenna has a broader tuned range 1558-1615MHz.
Product Link: https://www.te.com/usa-en/product-2195774-1.html
The following screenshot shows the output from the NanoVNA QT application
The following screenshot shows the output from the NanoVNA Saver application
TE Connectivity antenna showed a low VSWR of 1.25 which is near ideal for a GPS antenna to have. And in our real-world testing as well, the Time for First Fix was very low ( less than 20 seconds ) even on a cold start.
2. Antenna from Eteily Technologies
Eteily Technologies India Pvt Ltd is a company located in Madhya Pradesh, who are pioneers in Antenna design and related product manufacturing. They also offer custom Antenna design service.
Part Number: ET-GP28M-1L5-SMS
Description: GPS/GLONASS/IRNSS Magnetic Antenna
Product Link: http://www.eteily.com/gps-gnss-antenna/1270-gpsglonassirnss-magnetic-antenna-with-rg-174-cable-sma-male-connector.html
The following screenshot shows the output from the NanoVNA QT application
The following screenshot shows the output from the NanoVNA Saver application
With the Eteily, we obtained a VSWR close to 1.209 at the frequency of 1575.42 Mhz. The antenna from Eteily seems to be slightly better than the TE Connectivity type and we obtained a TTFF of less than 20 seconds.
3. Generic Antenna
- Generic GPS Antenna is purchase from Robu.in
- It has a central frequency specified at 1575.42 MHz
Product Link: https://robu.in/product/1575-mhz-gps-glonass-gnss-antenna-for-gps-gsm-module-with-3-meter-cable-good-quality/
The following screenshot shows the output from the NanoVNA QT application
The following screenshot shows the output from the NanoVNA Saver application
The VSWR at 1575.42 Mhz was greater than 1.5, and no wonder it took more than 2 minutes to get a GPS Fix in the same test setup.
Conclusion
So among the GPS Antennas we have tested following is the order in which the Antenna performance was good ( Best one at the top )
Eteily Antenna
TE Connectivity Antenna
Generic Antenna
Links:
TE Connectivity antenna datasheet: https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FDS_2195774-1%7F1%7Fpdf%7FEnglish%7FENG_DS_DS_2195774-1_1.pdf%7F2195774-1
NanoVNA V2 Software download: https://nanorfe.com/nanovna-v2-software.html
Eteily Technologies home page: http://www.eteily.com/
