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Journal ArticleDOI

Resonant frequency of circular microstrip antennas with and without air gaps

01 Jan 2001-IEEE Transactions on Antennas and Propagation (IEEE)-Vol. 49, Iss: 1, pp 55-59
TL;DR: In this article, an improved analytical model is presented for calculating the resonant frequency of circular microstrip antennas with and without air gaps, which is widely applicable to all patch diameters-from very large to very small compared to the height of the dielectric medium below the patch.
Abstract: An improved analytical model is presented for calculating the resonant frequency of circular microstrip antennas with and without air gaps. Unlike the previous models, the present one is widely applicable to all patch diameters-from very large to very small compared to the height of the dielectric medium below the patch and also to the substrates covering the entire range of dielectric constants. The computed results for different antenna dimensions and modes of resonance are compared with the experimental values.
Citations
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Journal ArticleDOI
TL;DR: In this article, a defected ground structure (DGS) pattern is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna, which is simple and easy to etch on a commercial microstrip substrate.
Abstract: A defected ground structure (DGS) is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna. The proposed DGS pattern is simple and easy to etch on a commercial microstrip substrate. This will only reduce the XP radiation field without affecting the dominant mode input impedance and co-polarized radiation patterns of a conventional antenna. The new concept has been examined and verified experimentally for a particular DGS pattern employing a circular patch as the radiator. Both simulation and experimental results are presented.

275 citations


Cites methods from "Resonant frequency of circular micr..."

  • ...6 GHz using formulas in [12] and the optimum dimension of...

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  • ...Other techniques investigated ground planes with modified shapes like “ ” as in [12]....

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Journal ArticleDOI
TL;DR: In this article, a novel decoupling technique for closely packed patch antennas using near-field resonator (NFR) above each antenna element is proposed, which can be easily applied to multiple-input multiple-output (MIMO) antennas having multiple patch elements.
Abstract: In this paper, a novel decoupling technique for closely packed patch antennas using near-field resonator (NFR) above each antenna element is proposed. The decoupling mechanism is illustrated by investigating the electric-field (E-field) and magnetic-field (H-field) distributions. The E-field distributions indicate that the NFRs above the patches serve as coupling-mode transducers to produce an orthogonal coupling mode at the desired resonance, leading to high port isolation between the patches. The H-field distributions demonstrate that the H-fields in the substrate are confined within the excited element, leading to the effective suppression of antenna mutual coupling. The NFR can be easily applied to multiple-input multiple-output (MIMO) antennas having multiple patch elements. Three practical decoupling examples are demonstrated and the simulation and measurement results show that impedance matching for each antenna port and isolation of better than 20 dB are achieved for all these examples using the NFRs. Moreover, for the H-plane and E-plane decoupling of wideband two-port MIMO antennas, wide decoupled impedance bandwidths of 6.1% and 5.8% are obtained, respectively. More results of radiation patterns reveal that good radiation performance is reserved with no reduction in realized gain or front-to-back ratio.

123 citations


Cites background from "Resonant frequency of circular micr..."

  • ...It can be seen that the E-fields of the excited patch (Patch 1) nearly point to the same direction (the +y-direction) along the E1-edge, but demonstrate a direction reversal along the E2-edge, indicating that the excited Patch 1 operates in the normal TM01 mode [16], [17], [21]....

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  • ...22 GHz, indicating that the cavity operates in the normal TM01 mode [16], [17]....

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Journal ArticleDOI
TL;DR: In this article, an empirical formula for resonant frequency of a circular cavity-enclosed circular patch antenna is tested with measured results, and the patch miniaturization in the presence of the cavity is proved.
Abstract: An empirical formula for resonant frequency of a circular cavity-enclosed circular-patch antenna is tested with measured results. The patch miniaturization in the presence of the cavity is proved. Different design curves in terms of resonant frequencies and bandwidth are derived to facilitate antenna design without a priori knowledge of complex numerical techniques. A simple gain formula for a circular-patch antenna is derived and tested against the measured gain data. The results agree very well. The beamwidth, axial ratio, and mutual coupling in the presence of the cavity are investigated.

114 citations


Cites methods from "Resonant frequency of circular micr..."

  • ...More accurate results could have been achieved if dynamic was used in the new formula [ 35 ]....

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Journal ArticleDOI
TL;DR: In this paper, a defected ground structure (DGS) consisting of concentric circular rings in different configurations is experimentally studied to examine the stopband characteristics, and a metallic shielding is introduced at the back of the DGS to suppress any leakage or radiation.
Abstract: A new defected ground structure (DGS) consisting of concentric circular rings in different configurations is experimentally studied to examine the stopband characteristics. Unlike previous DGS designs, a metallic shielding is introduced at the back of the DGS to suppress any leakage or radiation, and this would be advantageous for microwave circuit applications. A wide stopband is demonstrated with a set of prototypes designed for X-band. Its application to suppressing mutual coupling in microstrip patch arrays is demonstrated

110 citations


Cites methods from "Resonant frequency of circular micr..."

  • ...9(a) shows a two element probe-fed array with a single ring CR-DGS and the patch is designed to resonate around 10 GHz using the CAD formulas in [19] and [20]....

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Journal ArticleDOI
TL;DR: In this article, a broadband circularly-polarized (CP) slot antenna is described and its key parameters are investigated to show how to couple the two CP modes and achieve impedance matching, and the effects of the distance between the parasitic patch and wide slot on the CP bandwidth and antenna gain are also discussed.
Abstract: A design is described of a broadband circularly-polarized (CP) slot antenna. A conventional annular-ring slot antenna is first analyzed, and it is found that two adjacent CP modes can be simultaneously excited through the proximity coupling of an L-shaped feed line. By tuning the dimensions of this L-shaped feed line, the two CP modes can be coupled together and a broad CP bandwidth is thus formed. The design method is also valid when the inner circular patch of the annular-ring slot antenna is vertically raised from the ground plane. In this case, the original band-limited ring slot antenna is converted into a wide-band structure that is composed of a circular wide slot and a parasitic patch, and consequently the CP bandwidth is further enhanced. For the patch-loaded wide slot antenna, its key parameters are investigated to show how to couple the two CP modes and achieve impedance matching. The effects of the distance between the parasitic patch and wide slot on the CP bandwidth and antenna gain are also presented and discussed in details.

99 citations


Cites background from "Resonant frequency of circular micr..."

  • ...articles [13], [19], the resonant frequencies of the two CP modes can be expressed as...

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References
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Journal ArticleDOI
TL;DR: In this paper, a simple method is described to calculate the capacitances of rectangular and circular microstrip disk capacitors, and the influence of the fringing field on the resonance frequencies of microstrip disks resonators is calculated.
Abstract: A simple method is described to calculate the capacitances of rectangular and circular microstrip disk capacitors. From the edge capacitances of the capacitors the influence of the fringing field on the resonance frequencies of microstrip disk resonators is calculated. A theory to compute the resonance frequencies of microstrip resonators with high accuracy is presented. The resonance frequencies are calculated from a resonator model employing an effective width and length or radius, respectively, filled with a medium of a "dynamic dielectric constant." Theoretical and experimental results are compared and found to be in agreement within 1 percent.

296 citations


"Resonant frequency of circular micr..." refers background or methods or result in this paper

  • ...much improved over the earlier ones [ 11 ], [12], [15], [16] and is widely applicable to the entire range of dielectric constants and to all values of the antenna....

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  • ...Watkins [13] was modified by Wolff and Knoppik [ 11 ] incorporating the effect of the fringing fields in a disk capacitor and by introducing dynamic dielectric constant defined through (4)‐(7)....

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  • ...The evaluation of is straightforward, as given by (1), and that of is a function of the static main and static fringing capacitances and the mode of resonance as given by [ 11 ]...

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  • ...The formulation, though incorporating the improved results of some earlier works [ 11 ], [12], is valid for the antenna parameters and . Thus the model [10] is not applicable to small values of , particularly when an air gap increases the value of ( in Fig. 1). Moreover, the calculation of the resonant frequency in [10] involves an erroneous equation, as discussed in the following sections....

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  • ...Following the analytical model by Wolff and Knoppik [ 11 ], an improved formulation is presented by introducing a new effective dielectric constant in place of the dynamic dielectric constant [11, eq. 18] of the medium below the patch to calculate the resonant frequency of a circular microstrip antenna as...

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Journal ArticleDOI
TL;DR: In this article, the resonant frequency of a planar, circular disc antenna was obtained in analytical form for a printed-circuit board, where the low profile antenna is separated from the ground plane only by a thin layer of dielectric material.
Abstract: The resonant frequency is obtained in analytical form for a planar, circular disc antenna which is etched on a printed-circuit board so that the low-profile antenna is separated from the ground plane only by a thin layer of dielectric material. The formula is found to have an error of less than 2.5 percent when compared with experimental data.

229 citations


"Resonant frequency of circular micr..." refers background in this paper

  • ...much improved over the earlier ones [11], [12], [ 15 ], [16] and is widely applicable to the entire range of dielectric constants and to all values of the antenna....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the effects of fringing fields on the capacitance of a circular microstrip disk are studied with the dual integral equation formalism for practical microstrip circuits when the substrate thickness is small.
Abstract: The effects of fringing fields on the capacitance of a circular microstrip disk are studied with the dual integral equation formalism for practical microstrip circuits when the substrate thickness is small. Approximations as well as exact numerical evaluations are made in the calculation of the capacitance. With a seminumerical approach, an approximate formula for the capacitance is obtained and shown to yield accurate results with the simple use of a calculator. Asymptotic lower bound and exact numerical computations are also carried out. The various techniques are illustred and compared with numerical results.

169 citations

Journal ArticleDOI
TL;DR: In this paper, the mode patterns of circular disc resonant sections are analyzed and the radiation losses are expected to be small for the dominant mode, which would therefore have the highest Q value.
Abstract: Mode patterns of circular disc resonant sections are analysed. Radiation losses are expected to be small for the dominant mode, which would therefore have the highest Q value.

155 citations


"Resonant frequency of circular micr..." refers methods in this paper

  • ...Watkins [ 13 ] was modified by Wolff and Knoppik [11] incorporating the effect of the fringing fields in a disk capacitor and by introducing dynamic dielectric constant defined through (4)‐(7)....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the cavity-model theory was applied to a 5 cm circular-disk microstrip antenna with an air gap between the substrate and the ground plane, and a simple formula for the resonant frequencies was obtained.
Abstract: The circular-disk microstrip antenna with an air gap between the substrate and the ground plane is analyzed using the cavity-model theory. A simple formula for the resonant frequencies is obtained. The internal fields, the radiation fields, the effective loss tangent, and the input impedance are derived when the antenna is provided with a coaxial feed. The theory predicts that the air gap does not alter the relative field patterns significantly but it provides a simple parameter by which the resonant frequencies of the antenna can be tuned. Measurements have been performed on a 5 cm circular-disk microstrip antenna with an air gap and good agreement between theory and experiment is obtained.

121 citations