However, a high-order design is also required to simultaneously ensure a flat response in the passband and a good out-of-band attenuation. Most conventional approaches are Butterworth or Chebyshev types, but they require a high-order design to ensure a good selectivity near the passband since they have no attenuation poles.Įlliptic-function filters have attenuation poles near their passbands, making them very attractive for high-selectivity applications. Planar microstrip filter designs are very challenging. They may be realized in various transmission line structures, such as waveguide, coaxial line, and microstrip line. ĭepending on the requirements and specifications, RF/microwave filters may be designed as lumped element or distributed element circuits. Emerging applications such as wireless communications continue to challenge RF/microwave filters with ever more stringent requirements-higher performance, smaller size, lighter weight, and lower cost. Filters are used to select or confine the RF/microwave signals within assigned spectral limits. The electromagnetic spectrum is limited and has to be shared.

These filters have been fabricated on a FR4 substrate and perform a very low cost solution for RF applications. The composite low pass filter in microstrip line with T and π network is a success with sharper cut off and less ripples in the passband.

T pi filters design