Three-Order Band Pass Filter with flat group delay using U-shaped Negative Group Delay Circuits

In order to achieve the full-passband linear-phase characteristic, the negative group delay circuit (NGDC) is applied to suppress the noticeable group delay at the edge of the passband of the traditional band-pass filter. This paper introduces the fundamental principle of the U-shaped negative group delay circuit, and configures them into a traditional band-pass filter for observation. From the simulation results, the GD fluctuation of the filter is reduced by 0.54ns, from 0.69ns to 0.17ns, and the insertion loss change is less than 3dB within the frequency range from 2.17GHz to 2.85GHz. It enables the traditional BPF to achieve a flat group delay in the entire passband, and realizes the full-passband linear-phase characteristic, which is suitable for applications.