Author Topic: Duplexer for maximum isolation (Read 445 times)

roltex_rohit123 · « **on:** May 20, 2012, 07:57:40 PM »

I need your help for designin a duplexer for a maximum isolation of incoming and outgoing signal. the frequency is 900MHz band. signal gain is about 50db.

Philippine Electronics Forum · « **on:** May 20, 2012, 07:57:40 PM »

roltex_rohit123 · « **Reply #1 on:** May 22, 2012, 08:44:51 PM »

I searched the internet for the duplexer and found out that ceramic duplexers are the best for use due to their small size and high isolation. does anybody have any other information about their availability, prices, part numbers? i need for 900Mhz and 1800 Mhz bands

Philippine Electronics Forum · « **Reply #1 on:** May 22, 2012, 08:44:51 PM »

ditchie · « **Reply #2 on:** May 22, 2012, 08:54:06 PM »

this one might help you a little. from a nokia 3310 unit, but it uses a diplexer. fequency 900 & 1800

link to the file http://www.4shared.com/office/tIS9KhZN/nhm-5_schematics.html?

Philippine Electronics Forum · « **Reply #2 on:** May 22, 2012, 08:54:06 PM »

roltex_rohit123 · « **Reply #3 on:** May 22, 2012, 09:23:12 PM »

the diplexer was used because the mobile is a dual band and they seperated the frequencies in the mobile unit. but i am using a narrow gap (broadly same frequency for transmission and receiving) both to be used in a same antenna system at the same time isolate the incoming and outgoing one from each other inside. otherwise it would be a simple oscillator. the duplexer is very much needed here.

Philippine Electronics Forum · « **Reply #3 on:** May 22, 2012, 09:23:12 PM »

rdpzycho · « **Reply #4 on:** May 22, 2012, 10:23:52 PM »

they are still diplexers as you are separating bands, albeit narrow, of frequencies. you can buy FBAR diplexers from Mouser. though, it's much more common from Chinese distributors. cavity diplexers are also available for high power use.

Philippine Electronics Forum · « **Reply #4 on:** May 22, 2012, 10:23:52 PM »

roltex_rohit123 · « **Reply #5 on:** May 23, 2012, 12:25:57 AM »

diplexer on one side is ok how about other? I think i certainly need a duplexer

rdpzycho · « **Reply #6 on:** May 23, 2012, 12:33:19 AM »

uplink and downlink (rx and tx) bands are separated significantly that duplexers are not needed. if you'll be needing duplexers then you should have already seen it in every mobile phone.

I've already posted the block diagram and actual circuit, it's up to you if you want to add a duplexer. but diplexers certainly works weel for us and every repeater that got through me.

roltex_rohit123 · « **Reply #7 on:** May 23, 2012, 11:13:44 AM »

can you tell me the part number for the diplexer you mentioned?

roltex_rohit123 · « **Reply #8 on:** May 25, 2012, 01:45:30 AM »

can you tell me any software to simulate the whole repeater?

Philippine Electronics Forum · « **Reply #8 on:** May 25, 2012, 01:45:30 AM »

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