Large Group Delay in Microstrip Circuit Using Coupled Open Stubs and Collocated Ground Slots

This letter proposes a large group delay microstrip circuit using a quarter wavelength symmetric coupled open stub (SCOS) and collocated double slot at 2.4 GHz. A design approach based on matching the quality factor (Q) of SCOSs and slot loaded line is proposed to arrive at the physical parameters of these resonators. It has been shown that coupled lines with collocated double ground slots have significantly higher group delay compared to the geometry with single open stub and slot in the ground. Electromagnetic susceptibility (EMS) of circuit has been analyzed using simulations. A design with peak group delay (PGD) value of more than 4.3 ns is fabricated and characterized to validate the design approach. In addition to the large PGD the realized circuit possesses wideband impedance matching characteristics similar to an all-pass network.