G. S. Tyagi

Radiation Performance of Switchable Ferrite Microstrip Array Antenna

This letter reports radiation performance of switchable microstrip planar array of 6

Magnetic tuning of three-pole microstrip bandpass filter

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Full-wave analysis microstrip resonator using magnetized ferrite

6 element circular patch antenna printed on Ni¿Al ferrite substrate with a normal magnetic bias field. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics including switchable and tunable radiation from a microstrip antenna with a single feed point. Under certain bias conditions, most of the power is converted into magnetostatic waves and little radiates into air. Under such circumstances, the antennas are highly inefficient, in the sense that they are effectively absent as radiators. The bias dependent properties of a switchable antenna in S band (3.5 GHz) are investigated.

Effect of anisotropy on microstrip linear resonator circuit

Lot of work on frequency tuning in resonators and filters with magnetic biasing fields have been reported. Normally the frequency shifts are due to variation of ferrimagnetic resonance of substrate material. In the present paper we have reported the frequency tuning of three-pole microstrip bandpass filter by varying the relative permeability of the substrate material with the externally applied dc biasing magnetic field. For this a three-pole microstrip bandpass filter with a center frequency 2.8 GHz was fabricated using a thick silver film deposited on LiZnTi polycrystalline ferrite substrate. A tunability of 17 MHz in the moderate range of applied magnetic field was observed at room temperature. Fabricated device shows the negligible variation in its transmission loss in the presence of biasing field.

Magnetically tunable microstrip resonator based on polycrystalline ferrite

The studies on the magnetic tunability of microstrip linear resonator using bulk polycrystalline ferrite substrate have been experimentally and theoretically (full-wave analysis) demonstrated. To study magnetic tunability we have chosen the half-wavelength microstrip linear resonator designed at 2 GHz resonant frequency. A tunability of 370 MHz for above and below cutoff has been achieved for direction normal to substrate magnetization (field from 0 to 5000 Gauss). For the theoretical analysis of fabricated microstrip resonator spectral domain approach used from dispersion curves resonant frequencies have been computed for different values of applied field. Comparisons of experimental and theoretical results show good agreement. Approach used for analysis is general and can be extended to different classes of resonators.

A low cost magnetically tunable microstrip ring resonator

An L band half wavelength linear resonator has been fabricated on ferrite substrate by conventional photolithographic technique. Design parameters were estimated by using relations of Bahl and Hammerstad. The response of the device has been studied by using HP 8714 ES Vector Network Analyzer and the resonance frequency has been found to be 1.660 GHz which agrees with the design frequency estimated by Kai Chang formulae. When linear resonator placed in magnetic field the resonant peak in general shifts with increase of magnetic field to higher frequencies. Highly anisotropic behaviour is observed with the direction of magnetic field. This can be exploited for fast change of resonance frequency for device applications.