This paper presents a compact quadrature coupler with tunable frequency and power-dividing ratio. Wide ratio are achieved by using the novel unit instead of transmission line sections in traditional varactor-based coupler. Closed-form equations derived for design parameters. For verification, is designed based on given parameters, which demonstrate 2.0 GHz to 6.0 -20 dB 7.2 at 3 GHz. Finally, m...