GSM900 and UMTS900 system combining question?

[cell_nokia]

Hi All,

Currently, I'm doing IBC system design but our design is based on existing system between GSM900 and UMTS900.
When I'm looking to the current design, they use Diplexer (Kathrein-78210279) to combine GSM900 and UMTS900 system.

Based on my knowledge, Diplexer is designed to combine difference frequency band as there are band pass filter there.

Then my questions are,
1) System seem working well based on walk test. I'm curious that is it possible?
2) If we can use Diplexer to combine "Difference system, same band", and then is it possible to use Triplexer to combine GSM900, UMTS900 and UMTS2100?

Thank you for your support.

[khurrambilal01]

Hi All,

Currently, I'm doing IBC system design but our design is based on existing system between GSM900 and UMTS900.
When I'm looking to the current design, they use Diplexer (Kathrein-78210279) to combine GSM900 and UMTS900 system.

Based on my knowledge, Diplexer is designed to combine difference frequency band as there are band pass filter there.

Then my questions are,
1) System seem working well based on walk test. I'm curious that is it possible?
2) If we can use Diplexer to combine "Difference system, same band", and then is it possible to use Triplexer to combine GSM900, UMTS900 and UMTS2100?

Thank you for your support.

We can use diplexer to perform combiner function for different technologies on different frequecnies;
But combiner is not intelligent so it can't distinguish b/w different frequencies on same band so you can't use diplexer for GSM 900 & UMTS 900 at the same time. Because diplexer just performs band pass function to separate all bands and combine all bands.

[indoor]

If you have UMTS2100 on the IBC system then power for the UMTS900 and GSM900 shouldn't be a problem. I would recommend using a power combiner (Hybrid 4 port combiner with a big termination load on one output port). Will give you a 3dB drop in power but hopefully not enough to cause coverage problems.

The Kathrein combiner you mentioned is for combining 900/1800 and 2100 systems so can't be used to combine 900 and 900 systems.

If you need the GSM900 and UMTS900 combined with as low loss as possible you will most likely need a special filter system made, which will cost lots.

[haq_enam]

Hi All,

Currently, I'm doing IBC system design but our design is based on existing system between GSM900 and UMTS900.
When I'm looking to the current design, they use Diplexer (Kathrein-78210279) to combine GSM900 and UMTS900 system.

Based on my knowledge, Diplexer is designed to combine difference frequency band as there are band pass filter there.

Then my questions are,
1) System seem working well based on walk test. I'm curious that is it possible?
2) If we can use Diplexer to combine "Difference system, same band", and then is it possible to use Triplexer to combine GSM900, UMTS900 and UMTS2100?

Thank you for your support.

Here are answers

1. Diplexer is to separate two band. It is okey using diplexer.
2. You can use combiner as well but combiner has 3 dB losses for combine whereas diplexer has just 0.5 dB... In order to get low losses diplexer is best option to use.
Another issue is isolation... diplexer has good isolation that combiner....

[cell_nokia]

Hi All,

Thank you for your answer. I got the answer that previous design is not correct and Diplexer can't do that as our understanding.
Then I plan to re-design it again and use HC to combine GSM900 and UMTS900. After that I'll use Diplexer to combine this path with UMTS2100. :)

[khurrambilal01]

Hi All,

Thank you for your answer. I got the answer that previous design is not correct and Diplexer can't do that as our understanding.
Then I plan to re-design it again and use HC to combine GSM900 and UMTS900. After that I'll use Diplexer to combine this path with UMTS2100. :)

Which means 3dB + 0.5 dB losses!

[indoor]

Which means 3dB + 0.5 dB losses!

If your system won't work with the extra 3.5dB loss at 900MHz then it will very likely not work for the UMTS2100. That said I wouldn't worry, most inbuilding systems are designed for the UMTS2100 and the lower cable losses and 6dB difference in FSPL (from 2100MHz to 900MHz) will work in your favour.

[dekili]

Which means 3dB + 0.5 dB losses!

3.5dB shouldn't be a problem on 900MHz. It would require to check power in order to avoid interference to macro layer than worring about in-building link budget.