Monojit Mitra

Measurement of noise and efficiency of 4H-SiC IMPATT diode at Ka-band

In this paper, different DC parameters such as the efficiency, voltage drop along the diode, quality factor, resistance and the noise measurement on a one dimensional n+npp+ DDR structure of 4H-SiC-based IMPATT diode have been studied using advanced computer simulation programme. The efficiency and noise measure vary with the operating frequency of the IMPATT diode. The efficiency as well as the noise measurement plays an important role in the choice of operating frequency. So, throughout the Ka band these parameters of the 4H-SiC IMPATT Diode are measured and compared and will be well suited for the optimum design in the Ka-band.

Hybrid technology for next generation broad band mobile radio communications

Multi-carrier system has been fuelled by large demand on frequency allocation, resulting in a crowded spectrum as well as large number of users requiring simultaneous access. Existing wireless systems may be utilized single frequency, single antenna and pulse for carrier transmission and reception. Problems of such system is that in case of failure the total system will become non operational. So we established a distributed system in terms of multi-carrier, multiantenna and coded pulse can provide a more suitable communication and sensor gives rise to DSSS-OFDM-MIMO based hybrid technology is the ultimate solution. This paper deals with the performance analysis of hybrid system to efficiently improve the link reliability/spectral efficiency of very high data rate communication systems. In this approach we interface DSSS to OFDM. Then we integrate this DSSS-OFDM to MIMO. This proposal is originally given for the operation in the 60 GHz band but without MIMO, if sufficient bandwidth is available. If the bandwidth is not available, we achieve the high throughput using MIMO) techniques. In particular, we apply MIMO detection methods based on Vertical Bell Labs Layered Space Time (V-BLAST) ordering techniques to hybrid systems with padding and without padding for different modulation techniques. Simulation results show that the proposed MIMO-OFDM-DSSS provides both frequency diversity and spectral efficiency to yield a powerful solution to the ever-increasing requirement of high throughput cell phones and ITS.

Space Charge Effect of IMPATT Diode Using Si, Ge, GaAs, InP, WzGaN and 4H-SiC at Ka-Band

ABSTRACT Extra space charges are generated in the drift region due to the avalanche multiplication process and space charge effect of IMPATT (impact ionization and avalanche transit time) diode reduces the efficiency of the devices. The disturbances in electric field, drift voltage, and space charge resistance represent the space charge effect. In this paper, a comparative study of these disturbances has been presented for silicon, germanium, gallium arsenide, indium phosphide, WzGaN (wurtzite gallium nitride), 4H-SiC (silicon carbide) semiconductor materials-based double drift region (DDR) IMPATT diode at Ka-band as well as the cause of poor efficiency in the diode highlighted. This will be helpful for the selection of the suitable material for optimum design of DDR IMPATT diode as well as to improve the DC to radio frequency (RF) power conversion efficiency.

Design of a miniaturized dual-band textile antenna using characteristic modal analysis for on-body applications

ABSTRACT A novel dual band textile antenna for ON body communication in the 2.45 and 5.8 GHz ISM bands is presented. The overall size of the antenna is 60 × 30 × 3.75 mm3 and the merit of the antenna lies in its design simplicity. To realize a small antenna size, the lower resonant frequency is generated by the ground plane which is larger than the radiator normally. The ground plane has been miniaturized with the addition of two alternate quarter wavelength slots placed parallel to each other. Through characteristic modal analysis, the ground plane of the antenna is optimized for radiating field parallel to the body which could facilitate ON body communication. The patch at the top has been folded in opposite directions to resonant at higher frequency. An equivalent circuit showing the working mechanism of the ground and the patch is shown. Simulation results were verified by measurement for the given antenna.

Ka band noise comparison for Si, Ge, GaAs, InP, WzGaN, 4H-SiC-based IMPATT diode

ABSTRACT A comparative study of small signal noise has been presented for n+-n-p-p+ double drift region (DDR) impact avalanche and transit time (IMPATT) diode. The comparison is made by taking different semiconductor materials such as silicon, germanium, gallium arsenide, indium phosphide, wurtzite gallium nitride and 4H-silicon carbide, as doping element throughout the Ka band frequency of 26.5–40 GHz. Also, a generalised idea for performing the small signal noise analysis for the IMPATT diode is presented, by taking a one-dimensional mathematical model of DDR IMPATT diode. The 4H-SiC material-based IMPATT diode is proven to be less noisy with noise measure (NM) variation of 17–29 dB in the Ka band, whereas Ge-based IMPATT diode is noisier with the NM value of 34–44 dB. This paper has studied the small signal noise behaviour and is helpful in selecting the proper semiconducting material for the optimum design of the IMPATT diode in the Ka band.

AN EFFECTIVE SAR REDUCTION TECHNIQUE OF A COMPACT MEANDER LINE ANTENNA FOR WEARABLE APPLICATIONS

In this paper, a symmetrically structured meander line antenna placed around a T-shaped junction with truncated ground planes is proposed for wearable applications. The designed antenna has a percentage bandwidth of 69.04% covering the GSM 1800 band industrial scientific and medical (ISM) 2.4–2.5 GHz band, 4G LTE band 7 (2.5–2.69 GHz). The antenna is compact in nature with a size of 30×40×1.6 mm3. SAR reduction is achieved without the attachment of any additional unit. It is found that the application of designed truncated ground planes around positions of high electric field (E-field) region is an effective solution for reduction of Specific Absorption Rate (SAR) significantly through field cancellation technique. Maximum temperature elevation due to electromagnetic wave absorption has also been computed. The antenna is simulated over a homogenous human dry skin model as well as over a head model. The proposed design is fabricated and measured, and it is found to be compatible for real world applications while considering its miniaturization, radiation patterns and SAR limitations.

Super high speed Hybrid technology challenges for smart solution in spectral-efficient high data-rate wireless networks

The realization of wireless communication providing high speed, high capacity and high quality information exchange between two portable terminals that might be located anywhere in the world is still the communication challenge. For the development of future wireless communication systems, an extremely spectrum-efficient transmission technology is required. In this paper, we interface OFDM with CDMA and then integrate this CDMA-OFDM to MIMO to generate a system which is functionally superior to other multicarrier systems. We investigate the effect of multipath signal propagation on the capacity, under both single and multi user channel on the conventional MIMO, MIMO-OFDM and spread MIMO-OFDM. The obtained results show that the multipath signal propagation has more influence on the capacity of MIMO than MIMO-OFDM and spread MIMO-OFDM. In addition, the capacity of spread MIMO-OFDM is higher under the condition of the multi user channel scenario. Finally we implement the CDMA-OFDM-MIMO technology as an integrated system taking all the desirable qualities of these system architectures, thus yielding a very robust and strong system. Therefore, Hybrid technology can offer a very powerful and affordable solution for real life wideband multimedia system targeting Giga-bit speed wireless transmission and ITS applications.

IMPLEMENTATION OF DIGITAL RADAR TECHNOLOGY FOR IMAGING AND REMOTE SENSING IN INTELLIGENT TRANSPORT SYSTEM

With the growth of broadband wireless technology like code division multiple access (CDMA) and ultra-wideband (UWB), lots of development and efiorts towards wireless communication system and imaging radar system are well justifled. Efiorts are also being imparted towards a convergence technology involving both communication and radar technology which will result in intelligent transport system (ITS) and other applications. The authors have tried to converge the communication technologies towards radar and to achieve the interference free and clutter free quality remote images of

HYBRID TECHNOLOGY PROVIDING CONCURRENT VEHICULAR SAFETY AND COMMUNICATION

Multi-carrier system has been fuelled by large demand on frequency allocation, resulting in a crowded spectrum as well as large number of users requiring simultaneous access. Existing wireless systems may be utilized single frequency, single antenna and pulse for carrier transmission and reception. Problems of such system is that in case of failure the total system will become non operational. So we established a distributed system in terms of multi-carrier, multiantenna and coded pulse can provide a more suitable communication and sensor gives rise to DSSS-OFDM-MIMO based hybrid technology is the ultimate solution. This technology is a promising technique for high-data-rate broadband wireless communications and radar because it can reduce interference, multipath effect, jamming and higher target resolution as compared to conventional communication & radar etc. The proposed techniques improve the performance of OFDM, DSSS and MIMO based wireless communications and sensing for ITS and Corresponding author: N. B. Sinha (nbsinha@yahoo.co.in). 54 Sinha, Bera, and Mitra other applications. Finally this system can be implemented using Software defined Radio to get continuous connectivity of the system.