Tunable quasilumped element quadrature hybrid

The tuning characteristics of a hybrid circuit consisting of two eight guide wavelength sections of uniform transmission line shunt coupled with ganged capacitors and exhibiting quadrature hybrid performance are described. Theoretical predictions and experimental results are presented for coupling at a design centre frequency of 1 GHz. The results show that 3dB coupling can be maintained to within 1.0 dB worst case over the frequency range 0.6–1.9 GHz. Phase quadrature is also maintained over this frequency range to within 5° degrees worst case at band extremes. The compact nature of this quasilumped coupler and its excellent tuning characteristics imply its usefulness as an MIC or MMIC component, with potential applicability in a broad variety of RF and microwave applications.