ECE 6130 -- Microstripline Filter Implementation
Portfolio Question:
How do you implement a filter design using stubs? Include information on applying the
Richardson Transformation and Kuroda identities.
Richardson Transformations:
Filter designs are developed as "ladders" of inductors and capacitors. These can be
implemented in microstripline as open or short circuited stubs.
The equivalent circuits are:
To verify these, see Smith Chart examples.
Use this to implement a filter:
Example:
Design a LP filter for fabrication using microstriplines. The specs are: cutoff frequency
of 2 GHz, attenuation of at least 30 dB at 4 GHz, impedance of 50 ohms, 3 dB equal-
ripple characteristic.
Step 1: Find the order of the filter.
See Figure 8.27b. |ω/ ωc| -1 = |4 GHz / 2 GHz| - 1 = 1.0 The attenuation of 30 dB
requires a fourth order filter N=4.
Step 2: Find the filter coefficients and draw the LC filter.
See Table 8.4b for 3dB equal-ripple.
