A Compact Frequency- and Power-Dividing Ratio-Tunable Quadrature Coupler

Table 2

Comparisons of measured results for reported quadrature couplers.

Ref.	Configuration	Tuning elements	Tuning elements number	Range (GHz)	Power-dividing ratio	Phase imbalance	Size ()
[2]	Single layer	RF MEMS	4	1.5-2.2 (38%) (RL >14 dB)	Fixed	< 1°
[8]	0.13μm SiGe	Varactor	2	Fixed at 28 GHz (RL > 20 dB)	0 dB–6.5 dB	< 2.5°
[11]	Single layer	Varactor	6	1.8-4.36 (83%) (RL > 20 dB)	-16 dB–5 dB at 3 GHz	< 5°
[12]	Single layer	Varactor	8	1.2-2.4 (67%) (RL > 15 dB)	0 dB–12 dB at 1.5 GHz	< 5°
This work	Single layer	Varactor	6	2.0-4.7 (81%) (RL > 15 dB)	-14 dB–6 dB at 3 GHz	< 5°

λg is the guided wavelength at the lowest tuning frequency. RL represents the return loss. MEMS represents the micro-electro-mechanical system.