Dr. P. Nageswara Rao received B. Tech degree from Nagarjuna University, Guntur, India, in Electronics and Communications Engineering and Master‟s degree from Coimbatore Institute of Technology, Coimbatore, India, in 1990 and 1995, respectively. Worked as faculty in ECE department at NBKRIST, Nellore and SreeVidyanikethan Engineering College, Tirupati for 20 years. Currently working as Principal at G. Pullaiah College of Engineering &Technology, Kurnool, A.P, and India. Areas of interest are Numerical Electromagnetic and microstripantennas.
substrate as single layer to provide planner structure. But disadvantage is we must use transformer to match impedance and it excites cross polarization. Coaxial probe: Probe location is used for impedance matching. Ease of insetting and low radiations is advantages of probe feeding. Proximity coupling: Proximity coupling offers some opportunity to reduce feed line radiation while maintaining a relatively thick substrate for the radiating patch [9-11]. The input impedance of antenna is affected by the overlap of the patch and the feed line, and by the substrates. However due to multilayer fabrication the antenna thickness increases. Aperture coupling: No spurious radiation escapes to corrupt the side lobes or polarization of the antenna. However due to multilayer fabrication antenna, thickness increases [12-13]. Among this coaxial probe is used for impedance matching, as it is ease of insetting and low radiation and also used with plated for multi layer circuits. Microstripantennas are versatile in the sense that they can be designed to produce a wide variety of patterns and polarizations, depending on the mode excited and the particular shape of the patch used . The required design is shown below in Figure1.
Rectangular and circular patch antennas are the most commonly used microstrip patch antennas. Dual characteristics, circular polarization, dual frequency operation, frequency agility, broad band width, feed line flexibility, beam scanning and triple band frequencies can be easily obtained from these patch antennas. Microstripantennas are widely used in the microwave frequency region because of their simplicity and compatibility with printed circuit technology, making them easy to manufacture. Generally a microstrip antenna or a patch antenna consists of a patch of metal on top of the grounded substrate. The substrate is made of a dielectric material.
N.P Yadav and J.A Ansari  investigated that antennas dual nature is realized by deploying shortening pin with U- slot loaded patch. Lower and upper frequency band are achieved as 443 and 287MHz and also noted that antenna shows frequency ratio of 1.4. Chai Wenwen and Zhang Xiaojuan . Had studied U-slot patch antennas with ∏- shaped feed slot and concluded that the U-slot patch antenna can be designed to achieve 50% impedance bandwidth as well as 30–40% gain bandwidth. By changing the sizes of U-slot and feed slot, the wideband characteristic can be altered into a dual-frequency characteristic. Sukhbir Kumar and Hitendar Gupta  concluded that microstrip patch antenna with U-slot is used to achieve wideband application with less return loss. In this paper they constructed and fabricated microstripantennas suitable for Wi-Max application that is centered at frequency 5.25GHz. So, now we will compare and carefully examine the slot patch and U-slot patch antenna loaded on rectangular microstrip patch antenna U-slot in this paper.
The application of this type of antennas started in early 1970’s when conformal antennas were required for missiles. Rectangular and circular microstrip resonant patches have been used extensively in a variety of array configurations. A major contributing factor for recent advances of microstrip antennas is the current revolution in electronic circuit miniaturization brought about by developments in large scale integration. As conventional antennas are often bulky and costly part of an electronic system, microstripantennas based on photolithographic technology are seen as an engineering breakthrough.
Microstripantennas, also referred to as patch antennas, are low profile, comfortable to planar and non-planar surfaces mechanically robust when mounted on rigid surfaces, compatible with MMIC (Monolithic Microwave Integrated Circuits) designs. Microstripantennas have a number of advantages over other antennas; they are inexpensive, lightweight and easy to integrate with accompanying electronics. In the wireless communication area, microstripantennas are of interest for implantable applications because of their flexibility in design, conformability and shapes.
Today's wireless systems requires the antennas of higher performance with small dimensions. To fulfil these requirements researchers are looking for more advanced antenna designs. Antennas which are used for these applications should be of low profile, light weight, low volume. All these requirements are overcome by using Microstripantennas. Fractal is new class of geometry. The concept of fractal antenna came from fractals existing in nature. Antennas can be simulated by using different software's like IE3D, CST, HFSS. Antennas can be designed at different frequencies for different applications.
Microstrip patch antenna was designed by using an optimization algorithm where the goal was to minimize the difference between the simulated far-field radiation pattern and the theoretical pattern with e = 0.4,CST STUDIO. The resulting optimized dimensions of the microstrip antenna was as follows: Wsub = _=2 = 148:0 mm, Lsub = _=2 = 148:0 mm, W = 106:8 mm, L = 96:5 mm,W50 = 9:8 mm, Wslot = 2:4 mm, Lslot = 21:7 mm,t = 3:175 mm, _r = 2:2 (duroid 5880 substrate).The design used a relatively small substrate in order to realize arrays with radii as low as e =0.4. The use of an inset feed (Wslot _ Lslot) is a common technique to improve the input impedance match of microstripantennas. The radiation pattern of the theoretical directional element with e = 0.4 is compared to the gain pattern of a microstrip patch obtained from EM simulation. in Fig. 3. Also evident from the gain pattern is the backside radiation which is present since the ground plane is not infinite in extent. The difference in peak gain between the theoretical pattern and the microstrip patch is approximately 0.7 dB. Frequency of operation is 2.69GHz,Main lobe magnitude is 3.99dB,Main lobe direction315.0deg,beam width 57.4deg, Design of antenna is illustrated by Figs1,2.
Indoor wireless links have intrinsic characteristics that affect the system performance, such as the multipath effect that causes signal fading, and interference effect from adjacent cells that degrades the bit error rate. From the physical layer perspective, one solution to combat these impairments is the use of directional antennas rather than the traditional omnidirectional ones . They have the ability to confine the power in certain directions instead of scattering the power everywhere. As a result of less power loss toward unwanted directions, the multi-path and interference effects are reduced. Directional antennas can be single or dual/multi- beam. Dual/multi-beam antennas are antennas that have more than one directive beam from a single aperture. These antennas are useful for indoor wireless systems which require coverage of multiple areas , as they reduce the required number of antennas and are found to improve the link quality , resulting in easier net-work deployment. Micro-stripantennas have been widely used in many modern communication systems, because of its robustness, planar profile, and low cost. Most of these antennas operate at their fundamental mode, which gives a broadside beam . Micro-strip antenna operating at the higher order mode has dual symmetric radiation beams, with each beam directed at respectively –. It is well known that the major drawback of a micro-strip antenna is its narrow bandwidth (3%). One of the popular techniques for broadening the patch antenna bandwidth is to incorporate a U-slot on its surface as proposed in  and . However, the U-slot technique was studied only at the Fundamental mode of the patch . To the best of authors’ knowledge, there is no published report on the study of the U-slot patch Antenna excited at the higher order mode.
Since the declaration of ultra-wideband (UWB) frequencies (from 3.1 GHz to 10.6 GHz) by the federal communications commission (FCC) in 2002 , antenna design for this new communications standard has attracted increasing interest. Commercial UWB systems require small low-cost antennas with Omni directional radiation patterns, large bandwidth and non-dispersive behaviour . These requirements make UWB antenna design more complicated than traditional narrow-band designs. An antenna is a key element for wireless communication as it transmits and/or receives electromagnetic waves . Several antenna designs have been developed during a decade, for their application depends on the physical parameters of its output. Due to recent trends of the communication system requirements in portable devices, it is necessary to design a light, compact, portable and an efficient antenna . Many researchers are still developing optimum designs to reduce the size and weight of multi band antennas while keeping good performances [5-7]. An integrated antenna is among the one that is being preferred due to several practical applications, because of its light weight, small size, easy to fabrication and cheap realization. A small integrated antenna called as microstrip antenna has significant applications in the area of wireless communication and is used for several microwave applications. The construction of microstrip antenna is easy as it requires a thin patch on one side of a dielectric substrate. The other side of substrate has a plane to the ground . The patch is generally made of conducting material like Copper or Gold and may be in any arbitrary shapes like rectangular, circular, triangular and elliptical or some other shape . For practical applications, the most common used microstrip patches are rectangular and
Circularly polarized (CP) antennas are widely used in wireless communication applications such as navigational systems, radar tracking and radio frequency identification (RFID) readers [1–4] because they allow more flexible orientation between the transmitter and receiver antennas. Circular polarization can be realized by exciting two orthogonal modes of equal amplitude and 90 ◦ phase difference.
The micro-strip antenna filter design of wireless sensor network nodes is usually used to improve the out-of-band suppression and frequency selectivity by increasing the order of the filters, but the filters are usually single band, not only the size is large, but also the in-band characteristics of the filters are not ideal. This paper proposes a method to design a micro-strip symmetric dual-band filter in wireless sensor network nodes. Firstly, the coupling matrix of single- passband filter is obtained by using the synthesis method of generalized Chebyshev filter function. Then, the coupling matrix of the dual-passband filter is generated according to the reflection zeros and the transmission zeros. Finally, the S parameters response curve is drawn by mapping the normalized frequency domain of the dual-passband to the actual frequency domain. According to the data analysis and experimental results, the method is feasible and effective to design a micro-strip symmetrical dual-band filter. It can not only provide a more guiding design method for the joint design of antenna and RF front-end circuit, but also realize the spread of single-passband filter to multi-frequency for a wireless sensor network node antenna.
In this work, a precise and effective approach is applied to calculate important parameters of circular patch an- tenna. Microstrip patch antennas of all shapes are widely used in communication systems where their small size, conformal geometry and low cost can be used to advan- tage. Due to the recent availability of low loss, commer- cial microwave ferrites there is an increasing interest in the performance of the patch antennas printed on ferrite substrates. Although some work [1-6] have been per- formed for microstrip antenna with GA approach for the patch antennas without magnetic biasing but analysis of almost all important parameters for ferrite substrate under magnetic biasing for circular patch antenna is new one. Present analysis also incorporate the dispersion effects due to magnetic field biasing in the form of effective propagation constant (k) which is not discussed in the referenced articles. Some similar referenced works [7-11] also have done mathematically or by conventional me- thods for optimization but this technique is rather precise, accurate and sensitive to optimize parameters of patch antenna as well as other type of antenna also.
S11 gives us the reflection coefficient of antennas. Reflection coefficient is proportional to the ratio of reflected to the input power of the antenna. Antennas usually radiate efficiently for particular range of frequencies. At these frequencies the give out power should be almost equal to input power, i.e., reflected power must very small.
Fig. 1b illustrates a schematic representation of a dipole antenna with two parasitic elements on each side with equal lengths on a FR-4 substrate with a thickness of 1.6mm which is designed to operate at 1.8GHz. This can be related to the well know Yagi-Uda antenna topology which is an endfire radiating antenna consisting a radi- ating element, reflector and directors. An increased length of a parasitic strip relative to the radiating element have an induc- tive behaviour which is used as a reflector and a shorter strip is capacitive directing the beam towards the intended direction . At the proposed design the parasitic elements are chosen to be resonant in order to have maximum impact on the radiation pat- tern. The parasitic elements are placed a distance L p either side of
There exist several wireless band standards such as IEEE 802.16 Worldwide Interoperability for Microwave Access (Wi-MAX) system around 3.3–3.7 GHz and IEEE 802.11a wireless local area network (WLAN) in the frequency band of 5.15–5.35GHz and 5.725–5.825 GHz, which have found wide applications in wireless communication systems. Thus, a broadband CP antenna that can operate at Wi MAX and WLAN bands is highly required  .Micro-strip antenna is a simple antenna that consists of radiated patch component, dielectric substrate, and ground plane. The radiated patch and ground plane is a thin layer of copper or gold which is a good conductor. Each dielectric substrate has their own dielectric permittivity values. This permittivity will influence the size of the antenna. Choose of substrate is also important, we have to consider the temperature, humanity, and other environmental ranges of operating. Thickness of the substrate h has a big effect on the resonant frequency and bandwidth BW of the antenna. Bandwidth of the microstrip antenna will increase with increasing of substrate thickness h but with limits, otherwise the antenna will stop resonating.  .Micro-strip antenna is a low profile antenna.
 K. C. Pan, 1 D. Brown, 1 G. Subramanyam, 1 R. Penno, 1 H. Jiang, 1 C. H. Zhang, 1 M. Patterson, 1 D. Kuhl, 2 K. Leedy, 2 and C. Cerny2, “Reconfigurable Coplanar Waveguide Bowtie Antenna Using an Integrated Ferroelectric Thin-Film Varactor”, Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2012 Article ID 249019, 6 pages doi:10.1155/2012/249019 June 2012.  F. H.Wee,1 F. Malek,2 Farid Ghani,1 S. Sreekantan,3 and A. U. Al-Amani “High Gain and High Directive of Antenna Arrays Utilizing Dielectric Layer on Bismuth Titanate Ceramics”, Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2012, Article ID 375751, 8 pages doi:10.1155/2012/375751. April 2012.
Microstrip antennas are characterized by a largernumber of physical parameters than conventional microwave antennas. They can be designed to have many geometrical shapes and dimensions but rectangular and circular Microstripresonant patches have been used extensively in many applications. In this paper, the design of strip line feed rectangular microstrip patch antenna is for wireless applications is presented and is expected upto 3GHz frequency span.Its performance characteristics which include Return Loss, VSWR, Gain and current density are obtained from the simulation.
ABSTRACT: Due to fast advancement in wireless communication technology, use of small size antenna has rapidly improved. Not only the size of the antenna its cost, performance, ease of installation everything have been taken care while designing the antenna. To meet this entire requirement micro-strip antenna is proposed. Nowadays microstrip antennas are used in many places such as aircrafts, spacecraft’s, satellite and missile applications. In this paper, we discuss the microstrip antenna, types of microstrip antenna, a variety of substrates used for designing the antenna and the literature survey which we have done.
In this paper, we demonstrate a low-proﬁle, conjoined two-monopole antenna system capable of operating in the 2.4/5 GHz WLAN band with isolation better than 19 and 16 dB over the 2.4 and 5 GHz bands and showing a compact size of 5 mm × 40 mm (about 0.04 λ × 0 . 32 λ at 2.4 GHz). The design comprises two symmetrically identical monopoles, formed by one 5 GHz driven coupling strip and one 2.4 GHz parasitic grounded strip. The parasitic strips are further conjoined, becoming a central, grounded T monopole. By loading a chip capacitor between the T monopole and the antenna ground, the mutual coupling in the 2.4 GHz band can be reduced by about 12 dB (from 7 to 19 dB). Moreover, the two 5 GHz driven strips are inherently decoupled owing to larger distance between them. The capacitor in this study neither function as a band-pass resonant structure as reported in  nor is considered as one of the two discrete auxiliary ports in the impedance matrix as calculated in . Substantially diﬀerent, the capacitor allows the conjoined strips (T monopole) to generate two diﬀerent resonant modes very close to each other with similar magnitude but out-of-phase surface currents on the parasitic strip of one antenna (Ant2) when the other antenna (Ant1) is excited. Good decoupling between the antennas is thereby attained. A comparison table for the previous work in [4–12] is provided. From Table 1, it can be seen that the proposed design shows a low proﬁle of 5 mm with no separation between antennas and yet oﬀers minimum isolation > 16 dB for every band. Details of the design are described, and the results thereof are discussed in the article.