A Lumped-Element Directional Coupler for Bandwidth Enhancement, Impedance Matching, and Harmonic Suppressions

Table 3

Measured performance comparison with previous works.

Refs.	(GHz)	FBW (dB)	PD.	AI.	Harmonic suppression area	Electrical size ()	Technology
[1]^1	1	~50/–15	4 : 1	No	(–40 dB)
[3]	1	9/–20	1 : 1	No	(–15 dB)		Microstrip
[2]	3	30.5/–15	2.5 : 1-10 : 1	No	(–15 dB)		Microstrip
[7]^2	1	4/–15	1 : 1	Yes	X		SMD
[11]	0.83	38.5/-10	1 : 1	No	(–20 dB)		Microstrip
[14]	3.5	61.1/–15	31.6 : 1	No	X		Microstrip
[12]	1.63/2.73	7.5/5.1^3	1 : 1	No	(-19.5)		Microstrip
This work	0.48	46/–14.3	1 : 1	Yes	(–30 dB)		SMD

¹Prototype II; ²Case B; ³3 dB bandwidth. PD.: power division ratio; AI.: arbitrary impedance matching; : the guided wavelength at the center frequency.