FIELD OF INVENTION

The present invention relates to the development of a single microstrip antenna that can serve the purpose of a radiator as well as a reflector.

BACKGROUND OF THE INVENTION
Rapid advancements in the communication technology demand miniaturization, multiple bands at fundamental modes for developing the associated systems.
JP2008035461 entitled "MICROSTRIP REFLECTION ARRAY ANTENNA" discloses a microstrip reflect-array antenna with low cross-polarization level. The antenna consists of a ground plate, a reflecting plate with an upper surface, a plurality of microstrip antenna units located on the upper surface, each of the microstrip antenna units consisting of an inner ring and an outer ring, a plurality of support units for supporting the reflecting plate above the ground plate and a signal transmitting unit located above the reflecting plate.
CN209104369 entitled "METASURFACE ANTENNA FOR REMOTE MICROWAVE WIRELESS CHARGING" discloses a metasurface antenna that can be used for remote microwave wireless charging, which comprises of a metasurface microstrip antenna plate and a microstrip source antenna plate. The metasurface microstrip antenna plate comprises a metasurface antenna cover layer and a first dielectric layer, the microstrip source antenna plate includes a metal microstrip patch, a second dielectric layer and a metal ground layer; the second dielectric layer is arranged between the metal microstrip patch and the metal ground layer; wherein the metasurface microstrip antenna plate and the microstrip source antenna plate are fixed together through a fixing frame, the metasurface microstrip antenna plate and the microstrip source antenna plate are parallel to each other, and a gap is formed between the metasurface microstrip antenna plate and the microstrip source antenna plate; the metasurface microstrip antenna system adopts coaxial feeding, and a feeding interface is arranged on the bottom surface of the microstrip source antenna plate.
KR101381863 entitled "MULTI-POLARIZED MICROSTRIP PATCH ARRAY ANTENNA" discloses a multi-polarized microstrip patch antenna includes a first substrate having a ground at a lower surface, a second substrate disposed on the first substrate, a feed line provided between the first substrate and the second substrate; and a 2x2 or 4x4 S-band microstrip patch formed on the second substrate.
US5896107 entitled "DUAL POLARIZED APERTURE COUPLED MICROSTRIP PATCH ANTENNA SYSTEM" discloses a dual-polarized aperture coupled patch antenna system having a back plate, a ground plane and a patch plane. The patch plane has a conductive patch layer forming a plurality of conductive patches on one side. This design provides dual polarization with effective cross-polarization port-to-port isolation using only one microstrip feed network layer and without the use of jumpers of crossovers.
CN109742550 entitled "LOW BACKWARD RADIATION ANTENNA SYSTEM LOADED WITH DOUBLE CROSS-SHAPED ARTIFICIAL MAGNETIC CONDUCTOR" discloses a low backward radiation antenna system loaded with a double cross-shaped artificial magnetic conductor.
In the geometries described in the existing antennae, the antenna is either used as a reflector or as a radiator. This consumes an additional space to place the complementary module, which affects the communication system miniaturization. Besides the need for another module also require extra power and increases the cost of production. Therefore, there is a demand in the development of an antenna that can serve the purpose of both radiator as well as a reflector.

SUMMARY AND OBJECT OF THE INVENTION
It is an object of the present invention to provide an antenna that can serve the purpose of both radiator and reflector.
It is another object of the invention to provide a low-cost, low-power and miniaturized antenna design accompanying both radiating and reflecting modules.
The antenna of the present invention consists of three planes the upper plane having a complementary split ring geometry; the dielectric plane made of FR4 material; and the bottom plane having an optimized cross-slot and a flat plate, which can be switched through the sliding channel.
The upper plane serves the purpose of a radiator when the bottom plane is augmented with the flat plate.
The optimized cross-slot on the bottom plane, when formed, serves the purpose of reflector even without using an extra reflector. As a result, the primary radiation pattern takes 180º phase difference.
The cross-slot decreases quality factor and increase surface current path length, hence a compact (?/3) with respect to 0.62GHz along with high gain, triple frequency antenna is realized. The antenna size with a cross-slot on the bottom plane is reduced by 17% compared to the flat plate.
The antenna of the present inventions also provides adjustment to the input impedance using quality factor to produce multiple narrow bandwidths.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1(a) depicts the perspective view of the microstrip antenna according to the present invention.
Figure 1(b) depicts the cross-sectional view of the microstrip antenna according to the present invention.
Figure 1(c) depicts the bottom perspective view of the microstrip antenna according to the present invention.
Figure 2(a) illustrates the bottom plane augmented with the flat plate of the present invention.
Figure 2(b) illustrates the bottom plane consisting of the optimized cross-slot of the present invention.
Figure 3(a) depicts the equivalent circuit diagram of the coaxial fed microstrip patch antenna of the present invention.
Figure 3(b) depicts the equivalent circuit diagram of the radiating patch of the present invention.
Figure 3(c) depicts the equivalent circuit diagram of the antenna of the present invention.
Figure 3(d) depicts the equivalent circuit diagram of the circuit fitted with the antenna of the present invention.
Figure 4 shows the experimental results of the evaluated quality factor for bottom plane augmented with the flat plate (solid line) and bottom plane consisting of the optimized cross-slot (dotted line)of the present invention.
Figure 5(a) shows the experimental results of the return loss parameter S11 for bottom plane augmented with the flat plate in the present invention.
Figure 5(b) shows the experimental results of the return loss parameter S11 bottom plane consisting of the optimized cross-slot of the present invention.
Figure 5(c) shows the experimental results of electric field E–Plane (solid line) and magnetic field H–plane (dotted line) of the bottom plane augmented with the flat plate of the present invention.
Figure 5(d) shows the experimental results of E–Plane (solid line) and H–plane (dotted line) of the bottom plane consisting of the optimized cross-slot of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a microstrip antenna is developed, which can serve as radiator as well as reflector. Figure 1(a) schematically shows the antenna consists of three layers, an upper plane 100, a dielectric plane 200 and a bottom plane 300. On the upper plane 100 a Stub1 102 and a Stub2 103 is designed as shown in figure 1(a) to make a square patch 130 surrounded by two concentric square annular rings 110 and 120 together forming a complementary split ring geometry. The outer edge of the annular ring 110 is 14 cm, the outer edge of the annular ring 120 is 8cm and the outer edge of square patch 130 4cm. The gap between annular ring 110 to annular ring 120 is 1cm and annular ring 120 to square patch 130 is 1cm. The width of the annular ring 110 is 2cm and the width of the annular ring 120 is 1cm. The upper plane 100 has the feed point 101 for the annular ring 110; the Stub1 102 behave like a feeder to annular ring 120 and Stub2 103 act as a feeder to the square patch 130.
Figure 1(b) depicts the cross-sectional view of the microstrip antenna showing the dielectric plane 200. The dielectric plane 200 is made of FR4 substrate of thickness 1.6mm and permittivity of 4.3 and loss tangent is 0.025. The bottom plane 300 consists of the sliding channel 301 and 302, which holds the flat plate 303 that switches between the cross-slot 310 and the flat plate 303 as shown in figure 1(c). The coaxial feed cable is input to the microstrip antenna through a pin 320. The ground terminal 321 of the pin 320 is connected to the bottom plane 300 and the RF terminal 322 is connected to the upper plane 100 through the dielectric plane 200. The dimension of the bottom plane 300 is 17cm x 17cm and cross-slot 310 is 14.88cm and 12.32cm respectively, with the slot width of 0.8cm shown in figure 1(c).
Figure 2(a) illustrates the view of the bottom plane 300 with the flat plate 303. The upper plane 100 serves the purpose of a radiator when the bottom plane 300 is augmented with the flat plate 303. The optimized cross-slot 310 on the bottom plate 300 when introduced, serves the purpose of reflector even without using an extra reflector as shown in figure 2(b). As a result, the primary radiation pattern takes 180º phase difference. This result as the electric lines of force for coaxial fed complementary split ring antenna without cross-slot is similar to microstrip slot patch antenna at their resonant frequencies. The electric lines of force for coaxial fed complementary split ring 110 and 120 antenna with a cross-slot 310 on the bottom plane 300 itself lead to radiation at their resonant frequencies.
The coaxial feed 320 produces a radial electric field on the coaxial aperture and the equivalent current produced by a magnetic current on the ground plane by Transverse electromagnetic mode with the presence of probe. The inner conductor passes through the parallel plate region and attached to the upper plane 100. The radial transmission line mode and all higher-order mode in parallel plate region are determined from the excitation and is attached to the upper conducting plane excited through complex power of magnetic current by TMmn mode. An excitation field corresponding to Transverse electromagnetic mode field distribution in the annular ring about the probe but so long as the dielectric plane 200 is electrically thin, the electric field will be along the vertical direction and the interior modes will form TMmn towards radiating patch 110, 120 and 130 and the lines of force.
Figure 3(a) indicates the equivalent circuit of the microstrip patch antenna and figure 3(b) show the equivalent circuit of complementary split ring patch 110, 120 and 130. The equivalent circuit could be modelled as per the geometry of the present invention that tunes the impedance externally while the whole peripheral device loaded with the antenna. The changes in quality factor for the cross-slot, lead to changes in input impedance so that the resonance occurs at 611MHz, 940MHz, 1435MHz and 2150MHz. The values of distributed elements evaluated at 0.62GHz for L1 is 0.0177nH, C1 is 52nF, L2 is 0.16288nH and C2 is 18.62pF. As per geometry of the antenna with the flat plate on the bottom plane as radiator 100–200–300–303 and cross-slot on the bottom plane as reflector 100–200–300; the extracted electrical parameters L1, C1, L2 and C2 is same. However, the quality factor is different, which is depicted in figure 4. The Q-factor values are the very crucial stage for the synthesis of the circuit's component for matching the S-parameter of the antenna at respective resonant frequencies. The equivalent circuit load evaluation setup quality factor is 52 at 0.744 GHz for the flat plate on bottom plane as radiator 100–200–300–303 and 50 at 0.62GHz for the cross-slot on the bottom plane as reflector 100–200–300.
The experimentally measured S-parameter of the return loss of the flat plate on the bottom plane as radiator 100–200–300–303 and the cross-slot on the bottom plane as reflector 100–200–300 is presented in figure 5(a) and figure 5(b) respectively. The electric field (E–plane) and magnetic field (H–plane) radiation patterns are shown in figure 5(c) and figure 5(d) for radiator 100–200–300–303 and reflector 100–200–300 respectively.

INDUSTRIAL APPLICATIONS
The object disclosed in the present invention is a single microstrip antenna that can serve the purpose of a radiator as well as a reflector. This antenna can be used for radar communication, duplicity management in object detection for aircraft communication. Figure 5(a) and figure 5(b) shows peak gain at multiple narrow band frequencies ranging between 0.62GHz to 1.44GHz. Therefore, the antenna can be efficiently utilized for resonance frequency shifting. Besides the antenna disclosed in the present invention reduces the overall cost of the communication system as one additional module, either radiator or reflector is not required. It is a low-power and miniaturized antenna design accompanying both radiating and reflecting modules.

Claims:

1.A single microstrip antenna comprising:
an upper plane (100), a dielectric plane (200), and a bottom plane 300;
a stub1 (102), and a stub2 (103) is mounted on the upper plane (100) to form a square patch (130) surrounded by two concentric square annular rings (110, 120); wherein the stub1 (102) behaves as a feeder to the annular ring (120), and stub2 (103) act as a feeder to the square patch (130);
an input pin coaxial connector (320) for providing RF input signal to the microstrip antenna; a ground terminal (321) is connected to the bottom plane (300), and the RF terminal (322) is connected to to the upper plane (100) through the dielectric plane (200);
wherein the bottom plane (300) consists of at least one sliding channels ( 301, 302) for holding the flat plate (303) that switches between a cross-slot (310) and the flat plate (303).
2. The single microstrip antenna as claimed in claim 1, wherein
the upper plane (100) behaves like a radiator (100–200–300–303) when the bottom plane (300) is augmented with the flat plate (303); and
the bottom plane (300) acts like a reflector (100–200–300) even without using an extra reflector when the cross-slot (310) formed on the bottom plate (300).
3. The single microstrip antenna as claimed in claim 1, wherein the upper plane (100) having a complementary split ring geometry.
4. The single microstrip antenna as claimed in claim 1, wherein the cross-slot (310) decreases quality factor and increase surface current path length to realize a compact antenna (?/3) with respect to 0.62GHz frequency.
5. The single microstrip antenna as claimed in claim 1, wherein due to the complementary split ring geometry of the antenna with the flat plate on the bottom plane as a radiator (100–200–300–303), and cross-slot on the bottom plane as a reflector (100–200–300) the extracted electrical parameters L1, C1, L2 and C2 are same, and the quality factor is different.
6. The single microstrip antenna as claimed in claim 1, wherein the antenna demonstrates multiple narrow band frequencies ranging between 0.62GHz to 1.44GHz.
7. The single microstrip antenna as claimed in claim 1, wherein the antenna is used for resonance frequency shifting.
8. The single microstrip antenna as claimed in claim 1, wherein the extraction of equivalent circuit tunes the input impedance for further frequency shifting.