Compact semilumped elliptic-function low-pass filter using microstrip meander line

For the size reduction and sharp attenuation of the low-pass filter in lower RF frequency range, a semilumped ellipticfunction low-pass filter was proposed using microstrip meander line, chip capacitor, and radial stubs. To estimate more accurate inductance of microstrip meander line, it was modeled in an inhomogeneous dielectric environment, and then the calculated inductance was compared with the conventional case. To provide an additional attenuation pole in stop-band, radial stubs were added to the proposed structure. The 3-order low-pass filter has a cutoff frequency of 1GHz and dimension of 14.6 × 16.3 mm² on the substrate with a relative dielectric constant of 3.38.