dowjones said:hi,
maybe I'm wrong, but a wilkinson requires 70ohms lines which are lambda/4 in length to work properly. In the frequency bandwidth that you indicate (6GHz more or less), the deviation from the theoretical lengths will be very large, affecting the device behaviour.
I see that you simulate with momentum. probably you are also affected by some line-to-line coupling. some drawing of the circuit could be of help to analyse the problem.
regards
biff44 said:Ok, lets take this a step at a time.
If you cascade the 3 two-way splitters directly together they work well. If you then space out the splitters with 50 ohm lines with bends in them, they do not work well.
The conclusion is that the bends in your lines, or the width of the strip, or something else, is causing the two 50 ohm lines to not look like 50 ohms. So, use an analysis program to simulate the bends, and and microstrip line, and adjust the parameters until they are a good 50 ohm match to well above your operating frequency. For instance, you might have to chamfer the bends if they are right angle ones. You might want to make more gradual circular bends if you have the room.
xxargs said:dowjones said:hi,
maybe I'm wrong, but a wilkinson requires 70ohms lines which are lambda/4 in length to work properly. In the frequency bandwidth that you indicate (6GHz more or less), the deviation from the theoretical lengths will be very large, affecting the device behaviour.
I see that you simulate with momentum. probably you are also affected by some line-to-line coupling. some drawing of the circuit could be of help to analyse the problem.
regards
For 2 port wilkinson needs using 70.7 Ohm line quarter wave trafo for transform between 100 input to 50 Ohm output (each leg, 100//100 Ohm give 50 Ohm on input) - and for wideband i think you must using some kind of multi section or tapered shape of quarter wave line. Shunt resistor between output port shall be 100 Ohm
for 4-port wilkinson you must make 200 Ohm - to 50 Ohm quarter wave trafo - 100 Ohm line quarterwave (each leg), and for wideband, same here, you possibly need some multi section or tapered shape of quarterwave line. Shunt resistor between output is a output impedance (50 Ohm) coupled in star together
Single stage quarter wave line in 2-port wilkinson have only around 1/3 octave bandwidth if you want return loss and isolation better than 20 dB on all ports.
single stage quarter wave line in 4-port wilkinson have 20 dB return loss limit on common input only to 1/6 octave, but return loss and isolation on output is now >= 1/2 octave
(bigger step quarter wave transform make bigger Q-value and smaller bandwidth)
If use 3 * 2-port single stage quarter wave line wilkinson to make 4-port give better bandwidth, worst is isolation between out port have 1/3 octave for 20 dB isolation limit.
biff44 said:Well, that is a big bandwidth (200%). I have done 160% with a 3 section.
The question is, what parameter are you interested in. If you only want to split the power equally, then 3 sections are all you need. IF you need good isolation betwenn the two output ports, then that might be the justification for so many sections.
Still, Try reducing it to 4 sections and see how it does.
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