Design of Planar Microstrip Ultrawideband Circularly Polarized Antenna Loaded by Annular-Ring Slot

Table 2

Comparison of reference CP UWB microstrip slot antennas.

Ref.	Antenna type	IBW (S11<−10 dB) GHz	3 dB ARBW GHz (fractional band)	Dielectric	Antenna area (mm × mm)	Peak gain (dBi)
[12]	Meander square ring slot	3.15–3.9	−(9%)	RO4003 and FR4	21 × 21	8
[6]	Square ring slot	2.45–3.1	−(6.3%)	FR4	54 × 54	3.3
[13]	Annular-ring slot	2.4–3.034	−(10.5%)	εr = 4.4	<90 × 90	4.4
[14]	Annular slot and cross slot	4.7–7.2	0.148 (5.92%)	εr = 4.2	39 × 62	4.1
		2.2–2.6	0.160 (2.46%)			5.8
[15]	Slot antenna	1.01–3.33	0.55 (32.35%)	εr = 3.2	70 × 70	2.5
			0.25 (5.6%)			2.5
[16]	Annular slot with linear slot	1.265–1.654	0.092 (6.1%)	εr = 4.2	80 × 80	5.2
		2.446–2.738	0.155 (6%)			6.3
[17]	Spiral slot	1.437–1.724	0.072 (4.45%)	εr = 3.5	100 × 100	4.4
		2.418–2.907	0.093 (3.5%)			3.8
[18]	Square slot	2.674–13.124	2 (32.2%)	εr = 4.4	60 × 60	4.2
[21]	Square ring slot	1.347–1.533	0.065 (3.4%)	εr = 4.4	80 × 80	4.3
[22]	Moon-shaped	2.08–3.75	1.48 (49.3%)	εr = 4.2	46.6 × 70	1.6
[23]	Trapezoidal	2.84–4.58	1.4 (36%)	FR4	38 × 40	2
This paper	Annular-ring slot	4.52–8.06	1.4 (21.25%)	FR4	25 × 24	4.59

IBW: impedance bandwidth.