GSM 900 Repeater design

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zac79x

Joined: 15 Jan 2007
Posts: 4

07 Apr 2008 1:36 GSM 900 Repeater design

First hello to all, it should be my first post here...
I'm "trying" to design a GSM 900 repeater with this scheme:
directive antenna --> LNA --> AMP+AGC --> PA --> omni antenna
directive antenna <-- AMP <-- AMP+AGC <-- omni antenna
The antennas are the same, i'm using diplexers on every side.
So the questions:
How much total gain for the upper side (and bottom side) amps, if i want a functioning repeater for a weak outside signal ?
What power outputs should i use on the PAs ?
Some papers or links to informations ?

zac79x

Joined: 15 Jan 2007
Posts: 4

23 Apr 2008 16:16 GSM 900 Repeater design

Nobody ?? Any suggestions ?

DDavid

Joined: 06 Apr 2006
Posts: 232
Helped: 22

23 Apr 2008 16:44 Re: GSM 900 Repeater design

Hi,

U question is to general!
u rest a lot of parameters

when u say weak signal how much do u mean

In general (i will put some parameters of my system) :
u will receive from BS to Repeater between -60dBm ÷ -90dBm.
Your PA suppose to be about 30dBm (again all numbers depend on distance and of course mobile channel parameters like do u transmit LOS etc...)
One of the most important parameters is DL total + UL total Gain suppose to be less then isolations of the both diplexers (from tx to rx) by factor of 12dB at least.

David

Added after 1 minutes:

In my system:

DL gain was Glna=60dB, G_PA=30dB
UL gain was Glna=45dB, G_PA=30dB

David

zac79x

Joined: 15 Jan 2007
Posts: 4

26 Apr 2008 13:45 GSM 900 Repeater design

Sorry for the missing parameters, but it's a new field for me. Some data:
Uplink 890-915 MHz, Downlink 935-960MHz
I'm thinking about a class B or hybrid broadband repeater. The service antenna should be capable of a near field coverage of about 20m*20m. This should be a BDA for home or office use in GSM band only.
I have problems finding suitable SAW filters, so i'm not able to obtain high TX-RX isolation...
For the PA stage i'm trying to use RF2104, for the LNA the AVAGO'S ATF33143. Interstage amps use broadband MMIC or BJT transistors.
Admitting I receive -90dBm at the donor antenna, and I want a near field coverage of about 20m+20m, are -10dBm at the service antenna enough ?

DDavid

Joined: 06 Apr 2006
Posts: 232
Helped: 22

27 Apr 2008 8:11 Re: GSM 900 Repeater design

Hi,

Please expain: I want a near field coverage of about 20m+20m.

David

Added after 6 minutes:

Hi,

About the saw filters
try to look for them at: EPCOS and Sawtec (triquint) (may be that i made a mistake with the names but they PRETTY SURE THEY WILL HAVE IT!)

David

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zac79x

Joined: 15 Jan 2007
Posts: 4

27 Apr 2008 14:17 GSM 900 Repeater design

I made a mistype, i meant 20m*20m field coverage near the service antenna (supposing an omnidirectanional antenna). The donor antenna has to placed with a sufficient distance from the service antenna.Your answers and suggestions are appreciated!