Combined Low-Pass and Bandpass Filter Response Using Microstrip Dual-Mode Resonators

A novel type of dual band low-pass/bandpass filter LPBPF using microstrip dual-mode resonator is proposed. The proposed filter combines the attractive features of dual-mode filters, such as the small size and the elliptical bandpass response, and provides a fair low-pass response. A parametric study of such a filter is presented in this contribution. A modified version of the LPBPF is proposed for better control of the reject-band. The designed and fabricated filters have very compact size with a very sharp transition and sufficient rejection between the low-pass response and the bandpass response