How to give power to SIM908 Antenna

[Amalinda]

I have an active GSM and GPS antenna of gain 9 and 2.5 respectively.
I want to connect these to the SIM908 as I am now in the PCB designing stage in Eagle.
How do I connect these two to the SIM908? I understand that I need to connect pin 59,79 the GSM and GPS antenna pins to the respective middle pin. But then, Since both my antennas require power Can you explain as to how I can provide power?

thank you so much.

 

[amitjagtap]

If am not wrong then..you have to provide some external Dc voltage on antenna input pin...

 

[Amalinda]

doesn't the SIM908 has a GPS vant out and GPS Vant In? Im wondering whts the perpose of those two pins. If you know kindly let me know.

 

[qwertycoolguy]

is it okay to power up the GPS antenna like that, externally? Wont it hard the SIM908 Module?

 

[FvM]

Can it be that you posted the question without even reviewing the SIM908 hardware design manual?

5.3 GPS-VANT-OUT and GPS-VANT-IN

GPS-VANT-OUT is a 2.8V output for active external antenna, if the active external antenna works at 2.8V voltage supply domain, user can connect the GPS-VANT-OUT and GPS-VANT-IN directly. If the antenna’s power is not 2.8V, a proper voltage should be provided to the pin GPS-VANT-IN depending on the active antenna, and the pin GPS-VANT-OUT should be kept open. For passive antennas, both the pin GPS-VANT-OUT and the pin GPS-VANT-IN should be kept open.

 

[qwertycoolguy]

truly sorry. I need to reconstruct this question. I knew this fact for the SIM908. But there are some other GPS Modules such as Linx that do not allow such GPS VANT IN option.

So could you please tell me in a situ like that, how can I power up the GPS? Can Mix a DC with the GPS antenna Input to the module? I think it can hard the mod, would it?

 

[FvM]

I don't understand why you asking about SIM908 if you are actually using a different module.

If the module has no provisions for active antenna supply (most modules have), then you need an external bias tee.

 

[Batang]

If you want to provide a voltage supply to an external amplified antenna and the GPS receiver module does not have an input for this then you can use a ferrite bead as in the included picture. The following part from Element14 can be used as a specification reference:

https://my.element14.com/tdk/mmz1608s301a/ferrite-bead-0-3ohm-500ma-0603/dp/1669704RL?Ntt=1669704RL



Cheers.

 

[FvM]

I don't believe that the suggested part is particularly suited for a GPS bias tee, please look at the impedance curve

Instead you would want to use a GHz or "High-GHz" ferrite bead like this

You should also check, if the antenna input uses AC coupling, otherwise a series capacitor has to complete the bias tee.

 

[qwertycoolguy]

Thank you all for your replies!

 

[Batang]

Hi FvM, good catch I posted the wrong link.

Cheers.