Negative Group Delay Medium for Millimeter-Wave Applications

In this paper, a novel structure with negative group delay (NGD) in the millimetre-wave frequency band is proposed. The frequency band covered by this structure is equal to 26.5–28.5 GHz. In the proposed NGD structure (NGDS), using two different parts (Part 1 and Part 2), a transmission-zero (TZ) and a transmission-pole (TP) are created near the centre frequency of 27.5 GHz. By doing this, in the frequency range of 26.5–28.5 GHz, the group delay characteristic is less than −1 ns for both simulated and measured results. The dimensions of the proposed NGD medium are equal to 27.2 mm³ or 0.041 λ_g³ at the central frequency of 27.5 GHz.