Balanced Microstrip Circuit with Differential Negative Group Delay Characteristics

A balanced microstrip circuit with differential negative group delay (DNGD) characteristics is proposed. The proposed balanced circuit is based on coupled lines with transmission lines stubs connecting resistors. Common mode suppression and the differential negative group delay characteristics are integrated into one circuit. Analytical equations are derived for design. To verify the proposed structure, a balanced microstrip circuit operating at 1.0 GHz is designed, fabricated, and measured. The measured DNGD bandwidth is 8.8% from 0.962 to 1.050 GHz, with the DNGD value of -0.22 ns at 1.0 GHz, and the 10-dB differential return loss bandwidth covers from 0.95-1.05 GHz. The common-mode suppression is measured as -18 dB at 1.0 GHz.