microstripe RF choke (lambda/4) design
i'm looking to know how can I design a microstrip RF choke in frequency range of 2.8 to 3.2 Ghz with center frequency of 3 Ghz using microwave office.
actually I have some problem to specify the exact value for lambda/4
as we know lambda for this center frequency is 10 cm and so lamda/4 is equal to 25 mm
when I'm going to simulate my design in microwave office I dont know ho can I specify the number 25(mm) or some number in the region of that to my MLIN
would you please help me using your knowlege in microwave office
thanks in advance
25mm is the 1/4 wavelength in air. In the substrate, the value will be smaller.
If you would have field only in the substrate, and no field in air, then the wavelength would be smaller by a factor SQRT(epsilon_r) exactly. In microstrip, depending on the line width, most field is in the substrate but some field is in the air, so that the effective epsilon_r is smaller than the substrate value.
AWR have a transmission line calculator called "TXLine" that will calculate the effective epsilon and the required physical length for 90° at 3GHz, for your specific substrate data and line width. Alternative: You could also use a schematic model and just simulate the phase of a microstrip line segment.
thanks alot
it was helpful and finally i designd my favorite RF choke