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 0.3λg × 0.18λg, which is much smaller compared to the previously reported NGDCs with distributed elements.