A design of Butterworth stepped impedance microstrip low pass filter with DGS is presented in this paper. Two designs are introduced. The first design is a seven order low pass filter with three interdigital slots with different finger lengths inserted under the position of high impedance lines. The maximum insertion loss in the passband is better than 0.97 dB and the maximum group delay variation within the passband is less than 10 ps. The other design is a nine order low pass filter that use different shapes of the DGS (rectangular, square dumbbell and interdigital). The maximum insertion loss is about 0.5 dB and maximum group delay variation is 27 ps. The cutoff frequency of the proposed two designs is 16 GHz. The filter used for LEO satellite application. The filter is analysed using CST Microwave Studio, IE3D zeland and ADS. The filter is fabricated with photolithographic technique and scattering parameters are measured by using Vector Network Analyzer. Measurements and simulations show good agreement. |
