Deepak Sood

Design of compact reconfigurable switched line microstrip phase shifters for phased array antenna

Wireless communication systems are evolving toward multifunctionality. This multi functionality and reconfigurability provides users with options of connecting to different kinds of wireless services for many purposes at different times by providing additional degrees of freedom in the system e.g. cognitive radio, MIMO systems and high performance phased arrays. Although Phase shifters are important component in many RF microwave subsystems e.g. radar, phased array antennas, beam forming networks, frequency translators yet the reconfigurable phase shifter provides additional degree of freedom in these systems by reconfiguring the phase shift at a given frequency. In this paper design and simulation of reconfigurable switched line phase shifter for phased array antenna using Ansoft HFSS 14 is presented. The reconfigurability is achieved by loading phase shifter using high frequency PIN diodes which acts as microwave switches. A compact reconfigurable phase shifter has been designed which gives a very low insertion loss ≈ -1 dB and wide range of linear reconfigurable phase shift over frequency from 1 to 5 GHz. The designed phase shifter gives reconfigurable phase shift for different application i.e. at 1.8 GHz (GSM), 2.4GHz (Wi-Fi), 3GHz (traffic control and collision avoidance radars), 3.6GHz (WLAN) by appropriate settings of the 8 switch positions. As designed phase shifter can be used for 3600 beam steering in phased array antenna.

A Wideband Wide-Angle Ultra-Thin Metamaterial Microwave Absorber

A novel design of wideband, ultra-thin, wide-angle metamaterial microwave absorber has been presented. The unit cell of the proposed structure is designed by using parametric optimization in such a way that absorption frequencies come closer and give wideband response. For normal incidence, the simulated FWHM bandwidth of the proposed structure is 1.94 GHz, i.e., from 5.05 GHz to 6.99 GHz and �10 dB absorption bandwidth is 1.3 GHz from 5.27 GHz to 6.57 GHz. The proposed structure has been analyzed for different angles of polarization, and it gives high absorption (more than 50%) for oblique angles of incidence up to 60 ◦ . The designed absorber is in low profile with a unit cell size of λ0/6 and ultrathin with a thickness of λ0/32 at the center frequency of 5.92 GHz corresponding to 10dB absorption bandwidth. The current and electromagnetic field distributions have been analyzed to understand the absorption mechanism of the absorber. An array of the proposed absorber has been fabricated and experimentally tested for various polarization angles and oblique incidences of electromagnetic wave. The proposed absorber is well suited for surveillance and other defense applications.

A polarization insensitive compact ultrathin wide-angle penta-band metamaterial absorber

Abstract In this paper, the design, fabrication, and measurements of a compact ultrathin five-band metamaterial absorber with wide-angle stability have been presented. The unit cell of the absorber consists of five concentric metallic circular rings printed as the top layer of a grounded dielectric substrate of thickness 1 mm. The radii and the intermediate gap between the rings are optimized such that the proposed absorber exhibits five distinct absorption peaks at frequencies of 5.28, 7.36, 9.52, 12.64, and 16.32 GHz with absorptivities of 92.03, 90.46, 95.10, 91.65, and 91.10%, respectively. The proposed absorber is polarization insensitive for both TE and TM incident wave and results high absorption for wide incidence angle up to 60°. The proposed structure is compact with its unit cell size of 0.54 λ0 and ultrathin with thickness of ~λ0/19 corresponding to the highest frequency of absorption. Surface current and field distributions are studied to understand the absorption mechanism. A prototype of the proposed absorber is fabricated and experimentally tested for different polarization and incident angles. The measured results are observed to be in agreement with the simulated ones. The proposed absorber is suitable for potential applications due to its multi-band absorption.

REPLY TO “COMMENT ON 'A WIDEBAND WIDE-ANGLE ULTRA-THIN METAMATERIAL MICROWAVE ABSORBER'”

The cross polarization analysis of the proposed design done in “Comment on ‘A Wideband Wide-angle Ultra-thin Metamaterial Microwave Absorber” is similar to studies already conducted in [1, 2]. However, this analysis reveals that the design provides quite low absorption due to its diagonally symmetric geometry, but such various design configurations reported by different researchers [3-9] create the path to understand the importance of the requirement of polarization insensitive wideband/broadband metamaterial absorbers. Further, this importance enhances the in depth analysis of polarization sensitive multiband and wideband absorbers (so called) that are designed based on the studies and findings done at that time. Moreover, the very first perfect metamaterial absorber design reported in [7] is polarization sensitive, but it spawned great interest of researchers at the time due to its potential applications, and therefore, it becomes the motivation for today’s absorbers. Similarly, the dual-band designs reported in [8, 9] are also polarization sensitive, but they give an idea to design multiband and wideband metamaterial absorbers. Hence, there is a requirement to develop new techniques for the design of polarization insensitive multiband and broadband absorbers which is observed missing in this study of comment on the proposed design. Moreover, it also proves that the proposed design is a good metamaterial based wideband rotator which makes it useful for other potential applications such as spatial filters [10, 11] and radomes [12]. Thus, it is concluded that the design of monolayer polarization insensitive metamaterial based multiband and wideband microwave absorbers is still a challenge, and the readers should take this as an opportunity to improve the existing polarization sensitive designs or develop some techniques to reduce cross polarization effects as reported in [13] rather than simply proving that which one is an absorber or not as reported in [1, 2, 14].

Development of compact inductive coupled meander line RFID tag for near-field applications

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of 865–867 MHz. The size of the proposed tag antenna is 43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of 20.55 − j191.45 Ω at centre frequency 866 MHz. The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from 87.5 to 35 cms depending on mounting on non-metal and metal packages, respectively.