A new class of miniature quadrature couplers suitable for
microwave integrated circuits (MICs) and monolithic microwave integrated
circuits (MMICs) are presented. The proposed couplers have
some advantages compared to conventional types, such as smaller size,
no harmonic response, and wide stop-band characteristics. Two 3-dB
quadrature couplers at two different frequencies, 0.9 and 10 GHz have
been designed and simulated. The coupler designed at 900 MHz has
been fabricated on Duroid substrate with microstrip technology.
Compared to the standard quadrature coupler more than 65% area
savings, has been achieved, and the first higher-order response appears
at 5.8 GHz. The measured results show good agreement with theoretical
prediction.