Need help for design of Bi-Directional amplification for 900MHz band

[the_paradox]

Please refer https://in.element14.com/broadcom-limited/aba-31563-blkg/ic-amp-rf-si-31563-sot-363-6/dp/7820526

Assume that I am using this in my circuit. Now that being said, I want to design a bi-directional amplifier.

My idea is to put two of these chips, one for downlink and one for uplink. The design is for cellular communication bosster by the way.(900MHz band and 2100MHz band).

First let's focus on only 900MHz band. My requirement is to have only one input antenna(Communicating with BS) and one output antenna(Indoor). These are to be connected through Co-Ax(RG-6 50Ohm). In between two antennas, comes this booster circuit.

My questions are:

1) Do you think the above Chip can be used as I am planning to use(one for uplink and one for downlink?) Will at least the concept work?
2) Is there anything I am missing?(Don't worry about the legality etc as I will make sure they will be met).

You can assume that I have a good antenna set-up. Just give me inputs for only amplifier circuitary.

Thank You
Regards
Prasad Bhat

 

[Romansh]

1. This chip will work if you will follow the application notes
2. Calculate the loss of you coax cables, make sure the gain is higher then the loss. Make sure you have a good isolation between uplink and downlink in full duplex application, use a good duplexer.

 

[BigBoss]

You can use this IC but you have to pay too much attention to split the bands.If this is not very well implemented, you'll lot of trouble.
In order to split the bands, a well designed ( or purchased Diplexer is a must).

 

[the_paradox]

I got your point. Thank you Romansh.

I got one more concern. As I have two amplifiers working simultaniously, Can some thing like this happen? Like, The signal that is transmitted by downlink channel be picked up by the same antenna (may be due to reflectrions) and amplified by uplink amplifier and transmitted back in outdoor antenna?

 

[FvM]

I got one more concern. As I have two amplifiers working simultaniously, Can some thing like this happen? Like, The signal that is transmitted by downlink channel be picked up by the same antenna (may be due to reflectrions) and amplified by uplink amplifier and transmitted back in outdoor antenna?

This doesn't happen if you have suitable diplexers with sufficient suppression of the other channel, as stated by BigBoss. Your question suggests that you didn't understood the diplexer point at all.

Study the scheme of GSM uplink and downlink channels to see how the pass band of both amplifiers must be constraint.

 

[the_paradox]

This doesn't happen if you have suitable diplexers with sufficient suppression of the other channel, as stated by BigBoss. Your question suggests that you didn't understood the diplexer point at all.

Study the scheme of GSM uplink and downlink channels to see how the pass band of both amplifiers must be constraint.

Sorry for being so ignorant FvM. I have studied the GSM scheme of channel allocation following your advice. Even though I had some idea about all these, some revision on my engineering syllabus helped to clarify many things. And also got your and Roamansh's point. Thanks for that. I am really making some progress here. I will update once I get some quantifyable results.
Thanks a lot for your inputs guys.

Regards
Prasad Bhat

 

[the_paradox]

Hello Guys!

Quite some time I took! I have come up with a design block diagram. According to that, I have a Duplexer at the entry point. i.e Outdoor antenna. From there, for the downlink, I will place an amplifier, then an isolator, from there,if necessary, another amplifier and an isolator connected to another duplexer which is connected to indoor antenna. The same design repeats for the uplink, but starts from the indoor antenna. I have taken care of bandwidth and frequency range concerns.

Now Would like to get some PCB design inputs from you guys. If you have any suggestions for the layout design for this product please provide. Ground plane requirements, signal shielding etc.

I am thinking to migrate my operating band to 2100MHz as this is the 3G band used by my provider and it is more relevent at present conditions as I will be able to get a 3g data conection to work. There are areas where it is not possible to get wired broadband, and my solutions will help them.

Regards
Prasad Bhat