In this letter, a microstrip negative-group-delay (NGD) admittance inverter (J-inverter) is proposed to implement a self-equalized linear-phase absorptive bandpass filter (ABPF). It is revealed that this NGD J-inverter, being composed of a coupled-line loaded with a lumped resistor and an open-circuited stub, has an NGD pit in its frequency response. The superposition of the NGD pits associated with a specific number of the NGD J-inverters is utilized to counterbalance the group delay (GD) peaks at the lower and upper edge of the ABPF passband. A three-order ABPF prototype with a passband of 1.5–2.5 GHz is designed using six NGD J-inverters. Measured GD fluctuation within the 3-dB bandwidth is reduced to 0.18 from 0.59 ns compared with the ABPF using the conventional λ\lambda /4 J-inverter. The sharpness of the out-band roll-off has been retained. The measured input–output return loss is better than 12 dB over 0.6–3.5 GHz.

中文翻译：

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使用负群延迟导纳反相器的自均衡线性相位吸收带通滤波器


在这封信中，提出了一种微带负群延迟（NGD）导纳逆变器（J-逆变器）来实现自均衡线性相位吸收带通滤波器（ABPF）。据透露，该 NGD J 逆变器由负载集总电阻的耦合线和开路短截线组成，其频率响应中存在 NGD 凹坑。与特定数量的 NGD J 反相器相关的 NGD 凹坑的叠加用于平衡 ABPF 通带下沿和上沿的群延迟 (GD) 峰值。使用六个 NGD J 逆变器设计了通带为 1.5–2.5 GHz 的三阶 ABPF 原型。与使用传统 λ\lambda /4 J 逆变器的 ABPF 相比，在 3 dB 带宽内测得的 GD 波动从 0.59 ns 减少到 0.18。带外滚降的锐度得以保留。在 0.6–3.5 GHz 范围内测得的输入输出回波损耗优于 12 dB。