Young Scientist Speakers
We present four Young Scientist Speakers.
Studies on Multi-band / Wide-band MIMO Antennas:
Implementation and Characterization in Far-field / Near-field
Royal Military College of Canada, Kingston, Canada
Multiple-input multiple-output (MIMO) antennas have emerged as the key enabling technology in the present day 4G-LTE and upcoming 5G “Gigabit wireless” revolution, and are extensively deployed in both in the transmitter (TX)-end (eg. mobile base-stations) and receiver (RX)-end (eg, hand-held user-terminals, wireless access points). By utilizing the spatial / pattern / polarization diversity, MIMO technology boosts the Ergodic channel capacity bound compared to conventional single-input single-output (SISO) systems, within limited spectrum bandwidth and signal-to-noise ratio (SNR). The motivations of the present thesis-work are two-fold: (i) provide optimal design-strategies for compact multi-band / wide-band integrated 4G-LTE / 5G MIMO antennas and (ii) efficiently characterize metrics like envelope correlation coefficient (ECC) and mutual coupling from electromagnetic perspective.
A number of four-element multi-band / wide-band printed monopole based pattern / polarization diversity MIMO antennas are designed for 4G-LTE and sub-6 GHz 5G RX systems. Initially, elements like resonator loaded quad-band CPW-fed monopole or CSRR-loaded dual-band microstrip-fed inverted-L shared monopole antennas (ILAs) are utilized for footprint reduction of multi-band MIMO antennas. Later on, additional lower frequency resonance generated by inter-connected ground plane facilitates the design of a wide-band ILA-based sub-6 GHz MIMO antennas having electrical foot-print <0.15λ2, impedance bandwidth (IBW) > 58% and peak-gain > 4 dBi. Furthermore, resonator-loading is used to reduce the MIMO antenna area to 0.1λ2 and enable coverage of 2.5 / 3.5 / 5.5 GHz application bands.
Since ECC reduction plays a crucial role in maximizing the wireless throughput of MIMO systems, the second part of this work focuses on wide-band computation of ECC for MIMO antennas working in arbitrary propagation scenarios. Conventionally ECC is calculated by post-processing of complex 3D far-fields at discrete working frequencies, which becomes extremely tedious for multi-band / wide-band MIMO antennas. Also, this pattern-based approach does not assist efficient synthesis of optimum current distributions, targeting best diversity performance. On the other hand, the popular fast ECC calculation using the port-based S-parameters is seriously flawed and fails for MIMO antennas deployed in real-life indoor / outdoor propagation scenario. To address these glaring “research-gaps”, the recently introduced Cross-correlation Green’s functions (CGF) are judiciously integrated with the well-known finite-difference time-domain (FDTD) technique, to determine wide-band ECC directly from the time-domain radiating currents on the MIMO antenna. The proposed FDTD-CGF algorithms are first employed for MIMO antennas in uniform propagation environment. Later on FDTD-CGF method is extended to generalized non-uniform propagation scenarios, incorporating the effects of angular probability distributions of incoming signals in the modified CGF tensor, thereby paving the way for a combined electromagnetic / statistical wide-band ECC-analysis strategy. The proposed FDTD-CGF technique is shown to accurately predict ECC values for several MIMO antennas involving thin-wire dipoles as well as printed slot-antennas. Finally, analytical approximation of the generalized time-domain CGF tensor is attempted, to potentially reduce the computational cost.
Design, Development and Realization of Ground Station Antennas for Tracking of LEO Satellites
Sandip Sankar Roy
National Remote Sensing Centre, ISRO
LEO satellites orbit very fast with respect to ground. Tracking of these satellites are extremely critical in for error free data reception. Different tracking techniques are applied from early days of satellite communication. Out of these different tracking methods, Monopulse tracking is most sophisticated mode of tracking.
Reflector antenna, due to its high gain, is widely used for satellite data reception. Different variation of reflector antennas, such as, prime focal, Cassegrain, Gregorian , different offset geometries, Axially displaced ellipse are used for satellite ground station antennas. Shaped cassegrain reflector is most popular because of its high efficiency and less sensitivity to noise.
Tracking ground station antennas have Sum and difference modes, with different optimization goal which have to considered separately . Maximum efficiency along with low side lobe level is desired parameter for Sum mode while for difference mode sensitivity or tracking slope and maximum lock angle is the optimization goal. Several researches have been carried out to find out optimum feed for the monopulse. Four element, five element configuration, multi mode feeds are interchangeably used depending on stringent system specification, complexity and cost effectiveness. Complexity in design increases when a single antenna aperture has to be used for different frequency band and design criticality mainly imposes in design of multi band/composite feed. Frequency selective surfaces ( FSS) are often used to achieve multiband operation in reflector antennas.
Broadband Monopulse microstrip antenna array for X-Band Monopulse Tracking
VJTI Mumbai, India
In this talk, a broadband planar multilayer monopulse antenna at the X-band for monopulse tracking applications is presented. Different configurations of monopulse comparators have been discussed. A monopulse comparator using four hybrid rat-race for feeding the radiating elements of the antenna has been used. Each radiating part of the monopulse antenna consists of 4 × 4 electromagnetically coupled microstrip antenna array. To achieve circular geometry as well as better side-lobe level (SLL), a hybrid feeding technique is used in radiating antenna array by adding a few elements in series at the end elements of the parasitic layer of a 4 × 4 corporate fed array. The prototype has been fabricated, tested and measured results are compared with simulated results. The simulated impedance bandwidth for |S11| ≤ -10 dB is 21% (8.6–10.6 GHz). A measured peak sum beam gain of 24.4 dBi has been obtained. Measured SLL of < -15dB has been achieved in both elevation and azimuth planes along with a null depth of < -35 dB for difference patterns in both the planes. The radiation pattern is symmetrical in both the planes with half-power beam-width nearly equal to 9.0°.
Dual frequency Dual polarized Microstrip Antennas at S and X bands
VJTI Mumbai, India
Microstrip Antennas (MSA) are widely used antennas in the microwave frequency region because of their design simplicity, low cost, light weight, compatibility with printed-circuit technology and ease of manufacturing etc. In this talk I will discuss about dual-frequency dual-polarized MSA Array which have many applications like satellite communications, mobile communications, space borne synthetic aperture radar (SAR), radio frequency identification (RFID) systems etc. Dual-frequency dual-polarized MSA with common aperture should operate at two bands simultaneously to replace the requirement of multiple antennas, increase the channel capacity for increased data rate and also overcome the effects of fading using polarization diversity.
This talk will discuss new configurations of dual-frequency MSA to operate at S and X-bands which are then extended to arrays. The problem encountered in this configuration is that the higher order mode of first frequency band interferes with the second frequency band which will be addressed.
Design of MSA array for another application of monopulse tracking radar at millimeter-wave (mmw) frequencies will also be discussed. The challenges associated with antennas at mmw frequencies include low fabrication tolerances, losses from feed network and low efficiency. High gain antennas are required at these frequencies to overcome atmospheric attenuation due to absorption of microwave energy by water vapor or molecular oxygen. Slotted-waveguide fed microstrip antenna array will be discussed which combines the advantages of both the microstrip and the waveguide to give light weight, thin profile, high gain waveguide fed MSAA with low losses for monopulse tracking.
In the end, I will discuss the future scope of work in this area.
Know your deadline
- Registration of IEEE INAE 2018 have been started
- Early Registration Deadline:
Oct 31, 2018. Please read the details here
- Notification of acceptance:
Oct 01, 2018
- Final paper submissions:
Oct 15, 2018
- Travel support award notification:
Oct 15, 2018