Compact transmission‐type negative group delay circuit with low attenuation

Abstract

A novel circuit is presented for the design of transmission‐type negative group delay circuit (NGDC) with low signal attenuation. By loading a lumped resistor at a specific point on the loose‐coupling microstrip (MS) resonator, a lossy coupled‐line resonator is proposed, the size of which is effectively reduced by employing an open radial patch. A cascaded two‐stage NGDC scheme is presented to realise an enhanced negative group delay (NGD) value and better reflection coefficients. The layout of the two‐stage NGDC is designed in an anti‐symmetrical back‐to‐back manner. To validate the performance of the proposed circuit scheme, a prototype of the two‐stage NGDC has been designed, the working bandwidth of which is 35 MHz with a centre frequency of 1.79 GHz. This circuit is fabricated on Rogers RO4350B substrate with a thickness of 20 mil. A measured maximum NGD of −7.7 ns and a corresponding signal attenuation of as low as 8.6 dB have been obtained. Reflection coefficients are better than −20 dB. This NGDC occupies a compact size of 0.3 λ g × 0.18 λ g , which is much smaller compared to the previously reported NGDCs with distributed elements.