watchjohn
Electrical
- Mar 28, 2007
- 27
.
This question is related to the previous
( "Wideband antenna in wristwatch 10-6000 mhz" )
I´m looking for a duplex filter circuit (RX only)
I have 2 antennas each for its own frequency-band
a) 1 to 100 Mhz
b) 100 to 6000 Mhz
Ofcourse they overlap...can´t avoid that
I want to connect (couple) both antennas to 1 receiver.
To avoid "nulling out" problems when a certain signal is received at both antennas...(in fact they are all)
i understand that the best would be to have filters in
both antenna lines so a certain frequency will only be received 1 time (and not cause nulling out)
Such filters will also match the impedances to 50 Ohms.
I understand that basically i have to combine 2 filters
1) a low-pass with a cutoff of at 100 mhz
2) a highpass-filter with a cut off at 100 mhz
One side of the filters are connected together at the receiver input.
The other sides go each to there own antenna.
See an example here...for 144 and 430 mhz
the crosspoint (cutoff) is probably somewhere in the
middle...at 280 Mhz or so:
Now i want something like that for 1-100 and 100-6000 Mhz
It´s for receive only...so the C´s and L´s can be much
smaller.
So i downloaded a piece of free software called "diplexer"
by "tonne-software" it´s free and can be downloaded here :
This software lets you design exactly what i want
and allows to make all kinds of adjustments too.
it will also plot a graph.
So i input my values...and i get a nice drawing whit all the values..perfect
So i put in a crosspoint of 100 Mhz...and voila
Problem is it doesn´t show what happens at the end of
both the lower and higher range...actually you only see the crosspoint...the lower and upper ends go on forever !!
wich can´t be correct.
In other words...i get a design for a crosspoint at 100 mhz
but i cant see what happens at 6000 mhz (high end)
and at 1 Mhz (low-end)
It could very well that i have i nice crosspoint at 100 Mhz
but that at for example 5.8 Ghz there is a loss of 30 dB
caused by the circuit
Ofcourse i will use components that have specs up to 6 Ghz
Anyone can tell me what i´m doing wrong...or how the plot
really looks like at the ends of both bands.
I´m afraid that other online filter-calculators will have
the same problem ?
Thanks again !
WatchJohn
This question is related to the previous
( "Wideband antenna in wristwatch 10-6000 mhz" )
I´m looking for a duplex filter circuit (RX only)
I have 2 antennas each for its own frequency-band
a) 1 to 100 Mhz
b) 100 to 6000 Mhz
Ofcourse they overlap...can´t avoid that
I want to connect (couple) both antennas to 1 receiver.
To avoid "nulling out" problems when a certain signal is received at both antennas...(in fact they are all)
i understand that the best would be to have filters in
both antenna lines so a certain frequency will only be received 1 time (and not cause nulling out)
Such filters will also match the impedances to 50 Ohms.
I understand that basically i have to combine 2 filters
1) a low-pass with a cutoff of at 100 mhz
2) a highpass-filter with a cut off at 100 mhz
One side of the filters are connected together at the receiver input.
The other sides go each to there own antenna.
See an example here...for 144 and 430 mhz
the crosspoint (cutoff) is probably somewhere in the
middle...at 280 Mhz or so:
Now i want something like that for 1-100 and 100-6000 Mhz
It´s for receive only...so the C´s and L´s can be much
smaller.
So i downloaded a piece of free software called "diplexer"
by "tonne-software" it´s free and can be downloaded here :
This software lets you design exactly what i want
and allows to make all kinds of adjustments too.
it will also plot a graph.
So i input my values...and i get a nice drawing whit all the values..perfect
So i put in a crosspoint of 100 Mhz...and voila
Problem is it doesn´t show what happens at the end of
both the lower and higher range...actually you only see the crosspoint...the lower and upper ends go on forever !!
wich can´t be correct.
In other words...i get a design for a crosspoint at 100 mhz
but i cant see what happens at 6000 mhz (high end)
and at 1 Mhz (low-end)
It could very well that i have i nice crosspoint at 100 Mhz
but that at for example 5.8 Ghz there is a loss of 30 dB
caused by the circuit
Ofcourse i will use components that have specs up to 6 Ghz
Anyone can tell me what i´m doing wrong...or how the plot
really looks like at the ends of both bands.
I´m afraid that other online filter-calculators will have
the same problem ?
Thanks again !
WatchJohn