6 channel multiplexer
When form these to a 6 channel multiplexer,how to design the input
coupling of common port?
You have several choices. If the filter input impedances go to high values at the frequencies of the other filters, you can put them in parallel. One variation on this is for when the impedance does not go high at the adjacent filter frequency but does at then next frequency over. is to have two groups of three filters that are every other frequency. Then you can use one amplifier each to drive the two groups of filters. Use a splitter to feed the main signal path to each of the two amplifiers.
I have measured the smith chart of the S11.the two neighbouring filters are too close.Each is 7MHz Wide and only 1MHz Frequeny gap between them.The impedance at the frequency gap is not high. only after a certain distance,the impedance go high.so how about the very closed bands multiplexer?
In this case you will have to put the entire circuit of the six filters in an analysis program that has an optimizer and see if the program can change the element values to make it work properly. You may have to add one or more extra elements to the six filters so that the optimizer has more degrees of freedom to work with.
perhpas this method will be quite time-consuming,and not precise.no better than doing many experiments to get one.
Ah, the multiplexer question. You just don't take 6 filters and stick them together! The filter's input reactances have to complement each other. If they are contiguous lowpass/highpass structures, for example, you have to start off using a special lowpass prototype called a "singly terminated" prototype.
I think it is a very difficult thing.if the loss is't the question ,then ,you can sue circulator
Added after 44 minutes:
sorry,IT is useful only for duplexer.
How about this solution?
use a circulator to connect two 3 channel multiplexer.each submultiplexer composes three channel filters connected parallelly.the channels are seperated with a frequency distance of a channel,so that they can act complementary in
one submultiplexer.
so the first multiplexer composes the 1st,3rd,5th channel,and the
second multiplexer composes the 2nd,4th,6th channel. the loss of the second multiplexer equal to the sum of that of the first and that of the circulator.
how do you think about it?