Design of Frequency-Reconfigurable Microstrip Patch Antenna

Background/Objectives: A frequency reconfigurable antenna is presented with operating frequency as 3.35 GHz. This antenna is capable of switching to six different frequencies. Methods/Analysis: A reconfigurable microstrip patch antenna has been designed with slots cut in the ground plane. Three p-i-n diode has been introduced between these slots on the ground plane. The antenna produced six different frequency bands between 4.1818 GHz to 7.2727 GHz at operating frequency 3.35 GHz. The projected antenna has been designed using Taconic35 substrate with a relative dielectric constant of 3.5 and thickness of 1.52 mm. Findings: The proposed antenna exhibits multi-frequency behavior. This antenna is capable of switching to six different frequencies viz. 4.1818 GHz, 4.2424 GHz, 7.3333 GHz, 4.3030 GHz, 7.2727 GHz and 7.2121 GHz. At these frequencies proposed antenna produces six Return loss viz.-19.6476 dBi, -20.8143 dBi, -23.8396 dBi, -22.8885 dBi, -21.5707 dBi and -25.6389 dBi and Gain of 2.5808 dBi, 2.0623 dBi, 2.5694 dBi, 2.2819 dBi, 3.2810 dBi and 3.1969 dBi. Novelty/Improvements: In this paper a compact frequency reconfigurable microstrip patch antenna has been presented with less Return loss and high gain in compare with the conventional one. *Author for correspondence Indian Journal of Science and Technology, Vol 9(22), DOI: 10.17485/ijst/2016/v9i22/92812, June 2016 ISSN (Print) : 0974-6846 ISSN (Online) : 0974-5645 Design of Frequency-Reconfigurable Microstrip Patch Antenna Himanshu Anand* and Anil Kumar Department of Electronics and Communication Engineering, Shepherd School of Engineering and Technology, Shiats-Du, Allahabad 211007, Uttar Pradesh, India; sumant.himanshu4@gmail.com, anil.kumar@shiats.edu.in


Introduction
Patch antennas are assigned different names such as printed antennas, microstrip patch antennas or simply Micro Strip Antennas (MSA). Microstrip antennas are often used where thickness and conformability to the host surface are key requirements. Since the patch antennas can be directly printed onto a circuit board, these are becoming increasingly popular within the mobile phone market. These are low cost, have a low profile and are easily fabricated. In high performance aircraft, spacecraft, satellite, and missile applications, microstrip antennas are widely used. Presently there are many other government and commercial applications such as mobile, radio and wireless communications where microstrip patch antennas are being given preference [1][2][3][4] .
Reconfigurable antenna is an antenna which is capable of reconfiguring its characteristics such as frequency, radiation pattern, bandwidth and polarization to adapt the environment. In recent days the reconfigurable antennas are attaining great attention especially in future wireless communication systems due to its ability to reduce front end system and allow pre-filtering at the receiver. The reconfigurable antennas also contain many other features besides its reconfigurable capability, the features like low cost, multipurpose functions, and size miniaturization. Microstrip antenna has been used as a platform to design reconfigurable antenna 5-11 .

Proposed Antenna
A frequency reconfigurable design is proposed by using slot configuration in microstrip patch antenna with introducing p-i-n diode between slots, which works on the switching technique, i.e., ON-OFF state technique.
Reconfiguration of the antenna might be done in single part as well as multipart antenna. In single part antenna, Keywords: Microstrip Patch Antenna, Reconfigurable Frequency, p-i-n Diode three switches has been explained in Table 1. In Table 1 there are six frequencies corresponding to six different switching strategies of the switches: Where, s1=switch1, s2=switch2 and s3=switch3. The proposed antenna consists of four slots cut in the ground plane. These four slots are perpendicular to the feed line where the feed excites the slots. At the centre of feed line a low resistance radiation is achieved because of off-centre feeding. To achieve frequency reconfigurability, three switches are used in between the slots in order to change the effective length of the slots and thus controllable narrowband frequencies are produced. Here copper strip has been used to represent switching devices. When the copper strip is present, it means switch is ON whereas the absence of copper strip represents the OFF state of the switches. slots are cut in the antenna to distribute the current and reconfigurable components are installed in the slots to achieve reconfiguration while in multipart antenna, to achieve reconfiguration, current is distributed in some parts or all parts. Reconfigurable antenna is mainly used in laptop, circular phone, wireless system, Multiple Input Multiple Output System (MIMO), ultra wide band system and security based system, also it can be used in many other application by changing their functionality 12,13 .

Results and Discussion
In this paper a reconfigurable microstrip patch antenna is proposed with slots cut in ground plane with substrate three p-i-n diode has been introduced between these slots on the ground plane. The antenna produced six different frequency bands between 4.1818 GHz to 7.2727 GHz at operating frequency 3.35 GHz.
The Figure 4 shows the variation of VSWR with frequency.

Conclusion
To achieve frequency reconfigurability three p-i-n diode has been used between the slots which can produce six frequency bands ranges from 4.1818 GHz to 7.2727 GHz. This antenna has relatively good Return loss, Gain, Directivity, VSWR and is compact in size.