New dielectric ceramics with formula BaTi3Nb4, O„ and Ba6Til4Nbz039 have been prepared and characterized. BaTi3Nba017 was densified to 92% of TD after firing at 1310 oC for 4 h. However, Ba6Ti 1 4Nb2O39 fired under optimized conditions (1260 ` C for 4 h) showed only 85% TD together with secondary phase. The crystal system of both of the compositions is orthorhombic
Stephen,D S; Mathew,T; Jose,K A; Aanandan,C K; Mohanan,P; K G Nair(Department of Electronics, February , 1993)
[+]
[-]
Abstract:
Simultaneous elimination of specular reflection and backscattered
power from a plane metallic surface by simulated
corrugated surfaces of constant period and variable strip
width for TM polarisation is reported. This new configuration
offers almost a ten-fold frequency bandwidth compared
with a regularly spaced strip grating of the same size.
Dielectric resonator ceramics with composition formula Ba[(D3+0.3 Bi0.2)Nb0.5]O3,where D3+=Y,Pr,Sm,Gd,Dy and Er,were prepared by the conventional ceramic preparation route
Mathew,T; Stephen,D S; Aanandan,C K; Mohanan,P; K G Nair(Department of Electronics, 1994)
[+]
[-]
Abstract:
A trapezoidal strip grating surface that eliminates specular
reflections almost over the entire X-band frequency range for TM
polarisation is reported. This new grating structure ovemmes the
bandwidth limitation of conventional rectangular strip grating
surfaces.
The dielectric ceramics BaNd2Ti3Oto, BaNd2Ti4O12 and BaNd2Ti5O14 have been prepared by
Conventional solid state ceramic route. The sintered ceramic samples have been characterized by
X-ray diffraction and Scanning Electron Microscopy (SEM). The dielectric properties in the
microwave frequency range have been measured using conventional microwave dielectric
resonator methods. The BaNd2Ti1O10, BaN2Ti4O12 and BaNd2Ti5O14 have dielectric constants
(Er) ~ 60, 84 and 77 respectively. They have relatively high quality factors
Aanandan,C K; Mohanan,P; K G Nair(IEEE Journals/ Transactions (USA), 1990)
[+]
[-]
Abstract:
A microstrip antenna with large bandwidth is developed
using a parasitic technique . Compared to the available
wide-baud antennas,the proposed antenna structure is very
compact and gives a lessdistorted radiation pattern with frequency .
An impedance bandwidth,eight times that of a conventional patch
antenna of the same size, Isachieved. The concept of coupled microstrip
line model Is extended fortheoretical interpretation of the impedance loci
Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate ,
periodicallyloaded with thin conducting strips . The antenna
is found to be simulating the radiation characteristics of metallic
Corrugated horns . This can be an ideal substitute for metallic
Corrugated horns with added advantages like light -weight and low
production cost
George,J; Deepukumar,M; Aanandan,C K; Mohanan,P; K G Nair(Department of Electronics, March , 1996)
[+]
[-]
Abstract:
A new microstrip antenna geometry with considerable reduction
in size, with similar radiation characteristics to those of an
equivalent rectangular patch antenna is proposed. A relationship
has been suggested for fmding out the resonant frequency of the
new geometry, and its validity has been established by the
experimental results. Without increasing the aperture area, this
geometry also offers a facility for considerably reducing the
resonant frequency compared to conventional patches.
Jacob,George; Aanandan,C K; Mohanan,P; K G Nair; Sreemoolanathan,H; Sebastian,M T(Microwave and Optical Technology Letters, February 20, 1998)
[+]
[-]
Abstract:
A new method for enhancing the 2.1 VSWR impedance
bandwidth of microstrip antennas is presented. Bandwidth enhancement
is achieved by loading the microstrip antenna by a ceramic microwave
dielectric resonator (DR). The validity of this technique has been established
using rectangular and circular radiating geometries. This method
improves the bandwidth of a rectangular microstrip antenna to more
than 10% (= 5 times that of a conventional rectangular microstrip
antenna) with an enhanced gain of I dB