The printed monopole antenna (PMA) is one of the most suitable antennas to achieve high bandwidth and omnidirectional radiation pattern. However, very few theoretical works are available on the analysis of printed monopole antennas.
Introduction to Printed Antennas
The above disadvantage of having narrow bandwidth of microstrip antenna can be avoided by using a printed monopole antenna (PMA). Structurally, a PMA is slightly different from a microstrip antenna, which is discussed in detail in the next section.
Printed Monopole Antenna
The printed circuit monopole antenna version or printed monopole antenna is practically realized with a finite size ground plate. To achieve a large bandwidth for a printed monopole antenna, the strip arm only needs to be extended beyond the edge of the ground plate to form a rectangular printed monopole antenna.
Analytical Modeling of PMAs: Related Issues
Therefore, the dimension of the ground plane plays a key role in overall characteristics of PMAs. In Green's function evaluation for microstrip antennas, the boundary conditions are applied at the patch-dielectric interface and at the ground plane at the backside of the dielectric.
Motivation of the Present Work: Thesis Objective
Thesis Contributions
Thesis Organization
The substrate is modeled as a transmission line and the line length is equal to the thickness of the substrate. Further, the far-field radiation pattern of the antenna of the given geometry is calculated.
Full Wave Analysis
Spectral Domain MoM Approach
- Spectral Domain Immittance Approach
In the following literature, spectral domain technique is available for the analysis of rectangular patch [43], circular [44], elliptical [45], ring [46], printed dipole [41], arbitrary shape patch [47]. Dealing with different feeding mechanisms in the case of printed antennas is possible in the spectral domain approach, [48] focusing on the proximity-coupled microstrip antenna and [49–52] the aperture-coupled antenna.
Mixed Potential Integral Equation (MPIE) - MoM Approach
- Singularity Issues with MPIE Approach
The Green's function for the multilayer geometry can be estimated from the decoupled TM and TE field components. In [21], the integration is performed using the weighted average algorithm to overcome the pole-related problem.
Method of Moment
Effect of Substrate Material on the Performance of Printed Antennas
Magneto-dielectric Substrate
Uniaxial Substrate
Summary
An analytical model of PMA using transmission line analogy provides useful information about the dependence of antenna parameters on its dimensions and substrate material. Transmission line analogy is therefore an effective way to derive the closed form expressions for the input impedance and reflection coefficient of PMA. Dependence of impedance bandwidth on substrate material and dimensions of the antenna is also discussed in the results section.
Theory
Transmission Line Equivalent of PMA
The above expression for the input admittance of an HED to an ungrounded substrate for the case of TE polarization can be derived using [20] in which the characteristic impedance of air (Zc0 and Zc2) is η0sec(θ), while the characteristic impedance of of the substrate (Zc1) isη0/n1(θ), n1(θ) is the effective refractive index of the dielectric which depends on the angle θ, equal to qεr−sin2(θ). Using the value of R, L, C can estimate the value of Q for the RLC shunt circuit, so the bandwidth of the structure is shown in Fig. 3.1, it can be observed that the value of the second term in (3.4) is very small compared to the first term, so the second term can be neglected.
Results
Discussions
Equivalent surface-area model of square and circular patch discussed in [85] is used to calculate reflection coefficient of printed circular printed monopole antenna and the theoretical results are validated by HFSS. 3.6, the theoretical and HFSS results are compared with the results of circular PMA available in [79]. It is interesting to note that bandwidth is affected by widening the width of the rectangular printed monopole antenna as shown in Fig.
Summary
The current chapter is based on the derivation of the potential (scalar and vector) Green's function for a horizontal electric dipole (HED) on an ungrounded dielectric plate for the analysis of printed monopole antennas (PMAs), using mixed potential integral equation. and method of moments (MPIE-MoM). The exact Green's function formulation in different dielectric media required for full wave analysis of microstrip antennas (MSA) is available in. It may be mentioned here that the scalar and vector potential Green's function expressions derived here are important contributions to this chapter.
Potential Green’s functions of a HED over Ungrounded Dielectric Slab
Potential Green’s Functions in Spectral Domain
The relationship needed to derive Green's vector potential functions using magnetic field components can be expressed as: 4.18). The above expressions in equations (4.17) and (4.19) are Green's function in the spectral domain for an ungrounded dielectric plate. Using equation (4.20), the spatial domain vector and scalar potential Green's function can be expressed as.
Numerical Evaluation of Spatial Domain Vector and Scalar Potential Green
Approximation of Vector and Scalar Potential Green’s Function for a
4.3, it can be noted that the term DT E has a root between k0 and 1.5k0, i.e., there is a pole in the integrand of the Green's function GxxA of the magnetic vector potential of the space domain. Then using the integral in equation (4.21), the expression for the Green's potential function of the space domain vector can be given as It can be noted that for the case of the thin substrate, the magnetic vector potential GxxA is free space.
Evaluation of Numerical Integration for Spatial Domain Potential Green’s
4.4 shows the plot of the integrand of the scalar potential green function GV of a HED on an ungrounded dielectric plate at two different frequencies. Now to evaluate the scalar potential of the spatial domain, Green's function GV is used, the branch is cut off at k0 and the pole singularity is set at 1.01k0. The magnitude and phase variation of the scalar potential of the spatial domain, Green's function GV with distance, is shown in Fig.
Effect of Substrate Thickness and Dielectric Constant on Scalar Poten-
The transition from the near-field to the far-field region is indicated by the rapid phase change in the phase diagram of Fig.
Full Wave Analysis of Printed Monopole Antenna Using MPIE MoM
Results and Discussion
The calculated MPIE-MoM results for the input impedance and reflection coefficient of the printed rectangular monopole antenna are compared with the HFSS results, showing agreement as shown in Figure 4.7 (a) Graph of the input impedance (real) inΩ of a simple rectangular PMA (b) Graph of the input impedance (imaginary) inΩ of a simple rectangular PMA.
Summary
Introduction
In our proposed analysis method for PMA, which is described in detail in the next section, the field components are determined in the spectral domain. The field components of the spectral domain are then used to calculate far-field radiation patterns and gain for PMAs. The theoretical results of radiation patterns for rectangular and circular PMAs fed by a 50 Ω microstrip line are compared with experimental data given in [95] and [79], and simulation results obtained using HFSS.
Theory
Derivation of Expressions for Radiated Fields of PMA
Thus, the total radiation pattern for a rectangular printed monopole antenna, including the effect of a partial ground plane, is as shown in the figure. Closed-form expressions for the far-field radiation patterns of the circular printed monopole antenna shown in Fig. Similar to the rectangular PMA, the gain of the circular printed monopole antenna can be found using equation (5.11).
Results
Summary
As already mentioned, printed monopole antennas are suitable choices for ultra wideband (UWB) operation and for obtaining omnidirectional radiation characteristic. In order to achieve UWB operation in the 8 GHz to 18 GHz band, simple rectangular printed monopole antenna (RPMA) with a coating of magneto-dielectric material is proposed here. Finally, theoretical results derived here for the radiation pattern of a rectangular PMA with magneto-dielectric coating passing through a 50Ω microstrip line on a dielectric substrate are compared with Ansoft High Frequency Structure Simulator (HFSS) results.
Theory
In addition, return loss performance of the proposed antenna is compared with that of PMA with and without dielectric coverage to demonstrate bandwidth improvement for the proposed antenna.
Results
6.3 (b) are the radiation graphs in both planes for rectangular PMA with magneto-dielectric cover while Fig. 6.4, shows the reflection coefficient of the same with dielectric cover, magneto-dielectric cover and without any cover, in which a large bandwidth of 8.1 GHz is achieved with magneto-dielectric cover compared to dielectric cover and no cover.
Summary
However, in the case of PMA, the ground plane under the feed line is also part of the radiator to form an asymmetric dipole antenna. In previous cases, research on PMA is mainly done using a dielectric substrate but here its performance is carried out using a uniaxial substrate and similarly the PMA is also analyzed using the immittance approach which was earlier mainly used for the analysis of microstrip antennas. . In the following sections of this chapter, the theoretical analysis of rectangular PMA on a uniaxial substrate using the immittance approach is presented and the validation of the analytical results using HFSS is performed in the results section.
Theory
They, ˜Zhare identified as the inverse of the wave entrance observed from HED, located at the interface of free space and ungrounded dielectric. The far field radiation pattern of a HED on an ungrounded uniaxial dielectric layer in air (z>h) can be written as [53].
Results
But within the same frequency range, the efficiency of uniaxial substrate and negative dielectric degrades. 7.8, it can be concluded that PMA with uniaxial positive substrate provides greater directivity compared to negative uniaxial one. In other words, the PMA gain with positive uniaxial substrate is greater than negative uniaxial substrate since the direction is directly proportional to the gain.
Summary
In the case of printed antennas, especially for a microstrip antenna, the series capacitance is the static capacitance due to the patch and the ground plate, and the inductance represents the contribution of the various higher-order modes caused by the termination of the step impedance at the junction of the feed line and the patch. , the parallel circuit R, L, C represents only the particular mode(s) of radiation. But both previous literatures did not present flat values of resistance, inductance elements. In addition, all the values of various elements such as resistance, inductance and capacitance for different PMA cases are presented in tabular form.
Analysis of Antenna
- Case I: Printed Strip Monopole Antenna
- Case II: Rectangular Printed Monopole Antenna
- Case III: Bend Strip Printed Monopole Antenna
- Case IV: Bend Strip Printed Monopole Antenna with Protruding Stub
In [105], simulated and measured results are produced for flex strip printed monopole antenna with protruding stub in the ground plane. Here the circuit representation with corresponding values of lumped elements of printed monopole antenna with protruding stub in the ground is presented. The input impedance both real and imaginary for the present case is shown in Fig.
Summary
Mosig, “The analysis of arbitrarily shaped aperture-coupled patch antennas via a mixed-potential integral equation,” IEEE Trans. Parini, “Study of printed circular disk monopole antenna for UWB system,” IEEE Transactions on Antennas and Propagation, vol. Bhattacharyya, “Long rectangular patch antenna with a single feed,” IEEE Transactions on Antennas and Propagation, vol.
Theory (—) and simulation using HFSS (– –) for the radiation patterns of
Theory (—) and simulation using HFSS (– –) for the radiation patterns of
Plot of directivity of a simple rectangular printed monopole antenna on positive
Plot of directivity of a simple rectangular printed monopole antenna on negative
Equivalent circuit of multiple resonant antenna in first canonical form of Foster 72
Circuit representation of strip printed monopole antenna
Return loss of printed strip monopole antenna
Real part of input impedance of printed strip monopole antenna
Imaginary part of input impedance of strip printed monopole antenna
Geometry of rectangular printed monopole antenna on substrate having dielec-
Return loss of rectangular printed monopole antenna
Real part of input impedance of rectangular printed monopole antenna
Imaginary part of input impedance of rectangular printed monopole antenna
Various models for printed antenna analysis
Summary of the available work for printed antennas using transmission line
Summary of the available work for printed antennas using full wave technique . 19
Bandwidth calculation
Detail dimensions of rectangular PMA
Lumped element values of strip printed monopole antenna
Lumped element values of rectangular printed monopole antenna
Lumped element values of bend strip printed monopole antenna
Lumped element values of bend strip printed monopole antenna with protruding
