By means of substrate thickness more than 0. When the antenna is get excited at a certain resonance frequency, a strong electric field produced on the surface of the patch that is basically z directed and independent of the z coordinate. Each mode radiates, but it necessitates more and more stored energy as the mode number enlarges.
The patch cavity modes are described by a double index say n, p. The cut off frequencies of TE modes of circular waveguides give the resonant frequencies of. The term Aeff is an effective radius of the patch. Using the effective radius gives the resonant frequency within 2.
We combine equations as written in above to determine radius to give a particular resonant frequency:. The radial line alongside which the feed is placed determines the direction of the linear polarization. The non uniform radiation along its edge offers larger edge impedance than the square patch.
It is kept as optional slot as it is used in literature for similar dimensions. Wherever inset term is used it is due to famous structure of micro strip line feed by inset method.
The inset feed here is named only due to geometrical symmetry from the view point if seen from the top towards z direction. The patch is energized electromagnetically using 50 ohm micro strip feed line. The patch is proximity fed by a L-shaped micro strip line, and it is excited in the TMmode and have the centre operation frequency, 3. The reflection coefficient of an antenna shows how well antenna port is matched by source. A good reflection coefficient or VSWR alone is not all measure of a good antenna as it does not tell how fine the radiation is taking place in the required directions and conditions.
The results for the reflection coefficient variation and SWR due to different amendment on patch of the antenna are shown in Figure 3 and Fig. The value of S11 is resulted 3. The Smith Chart is designed on the complex reflection coefficient plane in two dimensions and is extended in normalized impedance used for problems involving any characteristic impedance or system impedance, while by far the most commonly used is 50 ohms.
By this it can be inferred that the antenna is perfectly matched and the power loss is least. The L-feed horizontal length incorporated below the patch introduces a capacitance repressing some of the inductance commenced by the vertical feed length due to thick substrate, and another resonance near the resonance of the patch antenna can be created.
The measured and computed results for the input impedance are shown in Figure 6. Exploration of radiation efficiency is performed. Radiation efficiency of an antenna is defined as ratio of power radiated to power given to antenna without return loss at antenna port.
However, the antenna efficiency is said as ratio of radiated power to actual power fed to antenna includes return loss at port. The above simulation based measurements are better in terms of radiation pattern, to result obtained in literature for the circular similar micro strip antenna [14]. As in the simulation results pragmatic that by increasing the di-electric constant the BW has been further improved, but it leads to thin substrate material which disturbs dimensions of L feed vertical length and so the inductance and series resistance formed by it.
It can be seen that when the thin dielectric is used for higher dielectric constant it reduces the patch radiation efficiency as it improves radiation from antenna which is further added in broadside total radiation as can be seen by other properties. Total antenna efficiency and radiation efficiency is shown in fig. In this work we studied the characteristics and equivalent circuit of different feed structure that can be used to connect a patch antenna to its source.
As a result, the input impedance plot in Fig 3. In addition, one needs to match the resonant resistance with the characteristic impedance of the feed line. A small antenna can be tuned to resonate with an appropriate addition of reactance, or it can be made to self-resonate so that the reactance cancellation at resonance happens naturally in the antenna structure. Since adding external reactance for this purpose increases the power loss and it also requires extra space, it is advisable to follow the second alternative.
The fringing field modes may have been channelized for good electromagnetic coupling, which is established by varying dielectric constant of lower layers. Thus for many applications, this geometry eliminates the need for the parasitic elements and thin dielectric constant substrate necessary to support them.
Amit A. Pues and A. Guo,1,2 K. Luk,2 and K. Mak, K. Luk, K. Lee, and Y. Luk, Y. Guo, and K. Huynh and K. Archevapanich, J. Nakasuwan, B. Purahong, N. Anantrasirichai, O. Deshmukh and G. Chew and J. AP, pp. Gautam and Surendra K. Stuart A. Long, Liang C. Shen, Mark D. Walton and Martin R.
Create Alert Alert. Share This Paper. Background Citations. Methods Citations. Citation Type. Has PDF. Publication Type. More Filters. Experimental results for an L-probe-fed shorted triangular patch antenna are presented. Experimental results for an L-probe-fed shorted semicircular patch antenna are presented.
A broadband T-probe proximity-fed short-circuited quarter-wavelength rectangular patch antenna is proposed as one possible candidate for mobile communication applications. Using a foam layer of … Expand. L-probe proximity-fed annular ring microstrip antennas. A broadband single-layer annular ring microstrip antenna fed by an L-shaped probe is studied.
A dual-band shorted patch antenna proximity-fed by a combined L- and Tprobe feed structure. Meeting Cat. Measured results of a dual-band shorted patch antenna excited by a combined L- and T- probe feed structure are presented. Guo, K. Luk and K. Lee [11] is taken as reference for comparison. In the present analysis L-shaped micro-strip feed is used. The proposed structure is shown in fig.
The antenna structure contains a thick substrate of thickness H. An L-shaped strip line is designed to couple the power to patch electromagnetically. This L-shaped feed is connected to a standard microstrip feed which in turn is connected to source. The fig. The capacitance thus introduced is suppressed by the inductance arising from vertical part of L-strip.
Apart from these, a series resistance arises due to finite conductivity of copper used. The expressions of series resistance R s and series inductance L s as given by R. Huffman [12] are. All antenna metallization is taken as perfect except vertical portion. There is a capacitance C s1 arising due to vertical electric fields between horizontal part of L-strip and ground plane in series with above L s and R s and is calculated as. There is a fringing capacitance between open end of L-strip and ground plane C f1 , between open end of L-strip and patch C f2 and between radiating edge of patch and horizontal part of L-strip C f2.
These capacitances are calculated by evaluating extended effective length of L-strip. The expression of extension in the length of an open ended microstrip line is given by T. Edward [13] and is given as. From T. Edward [13] the associated fringing capacitance is calculated as. Fringing capacitance between patch and L-strip is calculated using equations 4 and 5 , ignoring curvature of patch.
The capacitance due to vertical electric field between horizontal part of L-strip and patch is calculated as. The equivalent circuit of L-strip fed circular microstrip antenna is shown in fig. The parallel RLC circuit is equivalent of circular microstrip antenna. The resonance resistance R p of patch, antenna capacitance C p and inductance L p are calculated by Stuart A.
Long, Liang C. Shen, Mark D. Walton and Martin R. Allerding [14] and is given as. Where Q T is total quality factor, G T is total conductance of patch of radius a incorporating radiation loss, conduction loss and dielectric loss [15] and f res is resonant frequency of patch [16].
The basic design parameters of the proposed antenna are same as taken by Y. Lee [11] for comparison purpose. The radius of patch a is 17 mm, total height H of substrate is 11mm, and dielectric constant is 1.
The width and length of L-strip are 5mm and 9. The design frequency of the antenna is 3. A 50 ohms microstrip line on 1. Lee [11]. The variation of input impedance with frequency for different horizontal length of L-strip of proposed structure is shown in fig. The capacitive nature of antenna increases with horizontal length of L-strip.
The resonance resistance decreases as open end of L-strip moves towards center of patch. This indicates that open end is working as feed point. At the same time, bandwidth decreases due to increased quality factor of the structure. The bandwidth for different y 0 is given in Table I.
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