Dual-mode tunable filter with simple bandwidth control scheme

In this paper, we present the realization of a constant bandwidth two pole tunable filter by means of dual mode resonance. The proposed filter has a simple bandwidth control scheme, making numerical optimization of the bandwidth variation across the tuning range possible. A prototype having tuning range of 0.85∼1.4GHz using lumped inductors as input/output coupling elements has been realized. The bandwidth varies between 51∼59MHz across the tuning range and good matching is achieved within the whole tuning range.