900 Mhz signal amplifier (Repeater)

[yagizhanugur]

Hi everyone,

i have problems about my cell phone signal quality in my home. i thinked that i can use cell phone signal booster or a basic signal repeater. As you know it is hard to work with RF signal level. I want to amplify only 900 Mhz signal level.

Do you have any suggestions about antenna or circuit diagram. Which transistor amplifier topolgy do i need to use ?

 

[chuckey]

The amplifier is the easy bit. The problem is that you have a receiving aerial and a transmitting aerial connected to the input and output of an amplifier. If any of the amplified and transmitted signal is picked up by the receiver aerial the amplifier will oscillate. So you need aerials with very directional abilities pointing away from each other. Also you need the same but pointing in the other direction!!!
Broadcast repeaters receive a signal on one channel and re-transmit it on a different channel, this allows for a 2mV input and 100 KW ERP output on the other.
Frank

 

[yagizhanugur]

The amplifier is the easy bit. The problem is that you have a receiving aerial and a transmitting aerial connected to the input and output of an amplifier. If any of the amplified and transmitted signal is picked up by the receiver aerial the amplifier will oscillate. So you need aerials with very directional abilities pointing away from each other. Also you need the same but pointing in the other direction!!!
Broadcast repeaters receive a signal on one channel and re-transmit it on a different channel, this allows for a 2mV input and 100 KW ERP output on the other.
Frank

Thanks for your reply. I know , i have to be carefull about oscilatting. Can you make simple ERP ? I cant understand what you mean ---2mV input and 100KW ERP---

 

[chuckey]

2mV would be the input from the receiving aerial and 100KW ERP (effective radiated power) would be the output from a 20 KW transmitter multiplied by the gain of the transmitting aerial.
Frank

 

[FvM]

what you mean ---2mV input and 100KW ERP---

Just an illustrative example, I think.

Did you review the "similar threads" displayed on the bottom of this page, particularly this one? https://www.edaboard.com/threads/122624/

It gives a meaningful estimation of the parameters of an analog GSM repeater. You'll notice that the design involves high performance band filters. A purely passive repeater may be a solution in some situation.

 

[Borber]

Simplest solution is to connect log-periodic antenna with gain 10dB to your GSM if it has antenna connector. Antenna covers RX and TX frequency bands.

 

[yagizhanugur]

2mV would be the input from the receiving aerial and 100KW ERP (effective radiated power) would be the output from a 20 KW transmitter multiplied by the gain of the transmitting aerial.
Frank

Thanks Frank. I am really thankfully for your help.

According to your words what i understand is

1-) Using directional aerial for receiving and position it signal strength.
2-) Seperate receiver and transmitter part for oscilatting.
3-) A faraday cage for amplifer part.
4-) omni directional aerial for transmitter part.

There is a missing point in my mind. I have to make amplifyng process bi-directional and also my aerials has to be work bi-directional (uplink and downlink on same aerial). Is that could be a problem for oscilatting or anythink else ?

Just an illustrative example, I think.

Did you review the "similar threads" displayed on the bottom of this page, particularly this one? https://www.edaboard.com/threads/122624/

It gives a meaningful estimation of the parameters of an analog GSM repeater. You'll notice that the design involves high performance band filters. A purely passive repeater may be a solution in some situation.

You are right about band filters performances. I have to design it very effectively. I new at RF. I dont design any amplifier for theese frequency levels.

Simplest solution is to connect log-periodic antenna with gain 10dB to your GSM if it has antenna connector. Antenna covers RX and TX frequency bands.

I am staying alone but i want to amplify the signal