Analysis and Design of Gap-Coupled Annular Ring Microstrip Antenna

Table 2

Peak value of input impedance, resonance frequency for upper and lower band for different feed locations.

Gap length ↓	S  =  0.095 cm				S  =  0.100 cm				S  =  0.110 cm
Feed point 𝑃lower^∗	𝑃upper^∗∗ (ohms)	𝐹lower^# (ohms)	𝐹upper^## (GHz)	𝑃lower (GHz)	𝑃upper (ohms)	𝐹lower (ohms)	𝐹upper (GHz)	𝑃lower (GHz)	𝑃upper (ohms)	𝐹lower (ohms)	𝐹upper (GHz)	𝑃lower (GHz)
c  =  3.001 cm	39.40	74.08	1.727	1.899	43.58	73.93	1.744	1.899	53.05	73.30	1.778	1.900
c  =  3.101 cm	37.55	72.15	1.754	1.934	43.62	72.06	1.771	1.934	55.90	71.75	1.806	1.934
c  =  3.201 cm	36.50	65.02	1.788	1.977	42.35	64.16	1.806	1.977	53.20	65.50	1.842	1.977

* 𝑃_upper: The peak value of input impedance for lower band.
^**𝐹_lower: The peak value of input impedance for lower band.
^#𝐹_upper: The resonance frequency for lower band.
^##→: The resonance frequency for upper band.