Dual Frequency Ring Antennas With Coplanar Capacitive Feed

Abstract

Abstract-In this paper, design of a coplanar capacitive coupled probe fed microstrip ring antenna for dual frequency operation is presented. The proposed antenna is excited by a single probe feed connected to a capacitive feed strip placed along one of the radiating edges of the ring antenna. The coplanar capacitive feed strip is modified to obtain the best possible match with the antenna input impedance and to tune out the excessive capacitive reactance due to feed strip. It is also demonstrated that the modified feed strip can be placed either inside or outside the ring and similar radiation characteristics can be obtained at both the resonant frequencies. Ring dimensions decide the resonant frequencies values and their separation. Measured data fairly agree with the simulated characteristics.

Dual Band Coplanar Capacitive Coupled Microstrip Antennas With and Without Air Gap for Wireless Applications

“…It may be noted from Figures 8(a) and (b) that the shift in the resonant frequency in the second case is due to the use of different substrate (dielectric constant) and absence of air gap. However, it may be redesigned to any frequency of interest as suggested in [9][10][11][12][13][14][15]. All measured results fairly agree with the simulated values.…”

“…It is well known that considerable bandwidth enhancement can be achieved by increasing the overall height of the composite airdielectric medium [9][10][11][12][13][14]. However, the use of air gap increases the height/volume of the antenna which is undesired in several (compact) applications [15].…”

“…However, the use of air gap increases the height/volume of the antenna which is undesired in several (compact) applications [15]. Therefore, a design that uses small air gap for the similar antenna design is reported earlier [13] There are several microstrip patch antennas available in literature, which operate at dual resonant frequencies [14,[18][19][20][21][22][23][24][25][26][27][28][29][30]. For example antenna reported in [18] uses stacked configuration [18], whereas geometry presented in [19] uses suspended configuration (with air gap) [19].…”

New microstrip radiator feeding by electromagnetic coupling for circular polarization

“…In [12], a small capacitive feeding is proposed for ultra wide-band operation, but a multilayered configuration is also necessary. Other designs where the coupling takes place continuously along the edge of the patch rather than on a narrow portion of it, using different patch geometries, have also been reported [13]. The advantage of this feed system is the possibility to feed several microstrip radiators from the same distribution line in the case of linear arrays.…”

Design of Small Dual Band Microstrip Antenna for Broadband Applications

“…Antenna in [12] offers for circular polarization with axial ratio (AR) below 2dB. Antenna proposed in [13,14] have a slot along the patch to enhance for dual band operation. In the proposed antenna an air gap with dual band frequency with good bandwidth is being proposed…”