GPS modules with Active Antenna and without Active Antenna

Dear All,

After so much research, i've found out that GPS modules have so many factors that depend their performance on.

But I was initially under the impression that GPS devices with active antennas are always much better at receiving in harsh environments. But there are some companies that do not make GPS devices to support active antennas yet! have sensitivity levels higher than the ones with Active Antennas.

Im truly confused.

Here is one such GPS receiver that has the highest sensitivity i've seen so far.

https://www.telit.com/products/prod...-service-selector/show/product/jupiter-se880/
its data sheet:
https://www.telit.com/index.php?eID...5ee0b2655061a32e77&file=downloadZone/5455.pdf

My SIM908 even with an Active Antenna has lower accuission sensitivity. even the UBlox and my other Linx has less efficiency than this. Does this mean I can dump all these active antenna devices and start using this passive Antenna device (linked above) and expect higher performance? it even has inbuilt jamming protection and many other important features including A-GPS, online ephemeris download, client generated ephemeris down etc.

If you can shred some light, it would be so much helpful.

It really depends upon you application.

Most GPS receivers for portable application may include an additional LNA for use with a passive antenna or alternatively an external LNA will need to be included as part of your design if the GPS receiver module does not include one.

A GPS receiver module I have used successfully with embedded passive GPS antennae (chip and fractal types) is the MC-1010-2R from Locosys.

https://www.locosystech.com/product.php?zln=en&id=116

As a rule all GPS receivers will work with active (amplified) antennae, however if the GPS module contains an additional LNA then do not use it with an active antenna as overload of the receiver will result.

Perhaps if you can elaborate more on your application then perhaps a better answer can be provided.

Cheers.

Dear batang, Thank you for your reply. I learnt things from what you mentioned.

well my device will be working in hash environments. Derivatives of the design might be installed on vehicles, containers etc. Power is not a problem because when the GPS is in use, I want it to be extremely sensitive and give me a location as soon as possible. Which is why I am thinking of using GPS device that has SGEE, CGEE. Since I am anyway using a GSM module to update the location in a server I can simply use SGEE at not much additional cost. And I also don't mind the additional cost I will have to pay every time to download data for the SGEE function.

The point being, I really need a good sensitive GPS. But size is a concern of mine. But I am flexible there as well. lets say within the space of 5cm X 5cm and thickness of 1 Inch? I hope I gave you at least a slight idea of my application. the device will be accompanied by a LiPo. so I would prefer if the voltage range of the location device matches the voltage range of the LiPo (3.0 - 4.2)

Do you know any military standard GPS/GLONASS device vendors?


My second question

lets say I have GPS device which is 143dBi sensitive. How is it possible to say that fixing an active antenna to that device will have only a bit difference?

In the case of an Active antenna, lets say the chip has a sensitivity of 143dBi acquisition,. how should I chose the gain of the Active Antenna?

I would suggest based on you information another Locosys GPS module that would save you a lot of design time i.e. the LS2003C-2R combined GSP module and patch antenna.

https://www.locosystech.com/product.php?zln=en&id=99

I would recommend that this module is mounted in the middle of a ground plane that is ideally 40mm square, however there is some trade off in ground plane size and performance you can play with.

This module like the previous one I mentioned can be powered directly from a 3.7 volt LIPO battery.

I hope that helps, and also have a good look at the Locosys website as they have a range of products that may be of interest to you.

Cheers.

So whats the difference between other vendors such as Linx, SIM, Telit and Ublox? Could you please explain to me why this vendor is a better option to my application?

- - - Updated - - -

Dear batang,

Iam trying to take a look at this module you directed me to.

http://www.locosystech.com/product.php?zln=en&id=93#

I cannot seem to find any guidance how I can implement SGEE on this device even though it is supported. Do you have an idea? Do you have a design guide? I went through its datasheet provided by its page but was not able to find how I can implement SGEE. Do I have to manually download the data from a server and insert into the module?

For the SGEE usage I would suggest that you contact the GPS manufacturer for implementation.

However I question the need for it as once a GPS receiver has achieved a cold start and as long as the battery backup has power the receiver will have maintain ephemeris information even if the receiver is turned off etc. If I recall your application is some type of GPS tracking system.

I manufacture personal tracking devices and and use time/date fetched from a time server to set the initial GPS time/date to reduce first fix time and also use cell location as a fallback when inside buildings etc.

If the application is a mobile phone for example where the GPS is not used all of the time then the use of SGEE will allow faster position fixes assuming you have a data connection.

Cheers.