Ceramic patch antenna vs SMD Multilayer Chip Antenna for GPS tracker - Page 1
Forum section: electronics / rf-microwave

author: JulioCalandrin
author_rank: Newbie
timestamp: September 08, 2023, 02:52:10 am
content: Hi!This is my first post, I apologize for asking too many questions in one post.I'm not affiliated with any of the brands mentioned in this post.I'm designing a low-cost GPS tracker/Radiosonde for my electrical engineering course conclusion project. It will be equipped with a LoRa transceiver and different sensors for data collection. The purpose is primarily for stratospheric balloon launches, but I want to be able to play around with tracking other things.I'm on a tight budget, so all of my components will be purchased from LCSC, and the board will be manufactured on JLC PCB.I ended up entering a rabbit hole while deciding which type of antenna to use for the GPS system and need some insight or opinions.The GPS module I'm using is a cheap ATGM336H-5N31 (https://www.lcsc.com/product-detail/Satellite-Positioning-Modules_ZHONGKEWEI-ATGM336H-5N31_C90770.html) with a LNA (which I might reconsider for the sake of lower power consumption); the circuit is attached below. Note: The values for the capacitor and inductor on the antenna matching were not calculated; I just took those from a reference design from the GPS module manufacturer and will be calculating them later. If anyone has any material on that, it would make me really happy.One more thing: the PCB RF front end is not done; I will be adding the necessary ground planes and stitching vias later.I am trying to decide between these two antennas:1) Rainsun Microwave Tech GPS1003:https://www.lcsc.com/product-detail/Antennas_Rainsun-microwave-Tech-GPS1003_C239243.htmlThis one is a Multilayer Chip Antenna, and the reason I'm considering this antenna is because it is similar to the type used on the Vaisala RS41 radiosonde. During my research, I read that these types of antennas can be better for applications where the device can move around and will not have the antenna pointing up at all times since they are basically monopoles with linear polarization. But I also read that these types of antennas have poor performance (I assume the polarization doesn't help much).Also, I am questioning in which orientation I should use the antenna since the manufacturer only provides one example (http://aitendo3.sakura.ne.jp/aitendo_data/product_img/gps/GPS1003/GPS1003.pdf) with dimensions for the ground plane distances that would be impractical in my design. The best I could do with my dimensions would be like in the "option 1" image. From what I can see from other similar antennas with better documentation, they can be positioned horizontally like in the "option 2" image without a problem, but without official documentation, that would be blind guessing.2) Shenzhen Kinghelm Elec KH-GPS080804-WY -https://www.lcsc.com/product-detail/Antennas_Shenzhen-Kinghelm-Elec-KH-GPS080804-WY_C962211.htmlThe second option would be to use a good old ceramic patch antenna (a small one), like the KH-GPS080804-WY. It would look like the "option 3" image. This time I worry that since it would not be pointing up at the sky, its performance would be suboptimal. But again, since the manufacturer doesn't provide any irradiation patterns, that would be speculation.Ideally, I would manufacture test boards with all those options and test them out, but I'm on a tight schedule and budget, so that is not happening, unfortunately.In conclusion:What should I do?Has anyone ever had (good or bad) experience with those chip antennas?Is it a bad idea to use a ceramic patch antenna on its side?Is the LNA helping in these two cases?Thanks in advance!

author: Kean
author_rank: Unknown
timestamp: September 08, 2023, 05:43:05 pm
content: I've done a little testing along these lines as I build trackers for a few clients and on some project I experimented with different GPS modules and small antennas.1. Despite the module having an internal LNA, you will need the additional external LNA with the passive antenna. Otherwise you will want to use an active antenna.2. The ceramic patch antenna will beat the chip antennas even if not oriented upwards. Only use the chip antenna if you have very limited space and don't require a fast, reliable, or precise fix. They work, just not great. Mind you, that is a very small patch antenna... I've used 12x12mm and 6x19mm, but try to stick to 16x16mm or larger.For what it is worth, an anecdote. I sent one client a few modified trackers each with different GPS modules and antenna configurations. I didn't tell him what was in them, just asked him to test them for his application and compare against his RTK reference GPS. I got an interesting comment for the one that had a chip antenna: "Basically, I never want to see the module in 11201 again". And for the one with the most expensive module: "How much is 11203? It was very impressive".If you are limited in time, then I suggest designing your PCB such that it allows for different components to be populated and tested.