A Method for Fine Tuning of Resonance Frequency of Patch Antenna
Rajeswar Lal Dua1, Anjali Nigam2, Pooja Yadav3
1Prof. Rajeswar Lal Dua, head and Professor in the Department of Electronics and Communication Engineering at JNU, Jaipur, Rajasthan.
2Mrs. Anjali Nigam, working as research scholar in Department of Electronics & Communication, Jaipur national university, Jaipur, Rajasthan.
3Pooja Yadav, Research scholar in Department of Electronics & Communication, Jaipur national university, Jaipur, Rajasthan.
Manuscript received on May 17, 2012. | Revised Manuscript received on June 25, 2012. | Manuscript published on June 30, 2012. | PP: 381-384 | Volume-1 Issue-5, June 2012. | Retrieval Number: E0550061512/2012©BEIESP

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Abstract: When a patch antenna is fabricated, size of the as-fabricated resonant patch may be slightly different from its designed value due to tolerances in the fabrication operations. This will alter the resonance frequency. To overcome this problem this paper presents a new method for fine tuning the resonance frequency by dielectric engineering. This approach is especially suited to LTCC and similar processes where the antenna dielectric is composed of several layers. Composite dielectric constant of this multilayer structure is altered in such away that the resonant frequency is set back to the designed value. A cavity is cut below the patch in one or more dielectric layers. This paper investigates the effect of cavity size on shift in resonance frequency. HFSS software has been used for simulations. Three different dielectric materials were investigated for several resonant frequencies. f/f0 was plotted against Area Ratio (AR) to generalize the findings. Area Ratio is the ratio of area of cavity to the area of the patch, f is the resonance frequency for a given cavity area and f0 is its value without any cavity. Depth of the cavity may be equal to either one or two dielectric layer thickness in a four layered dielectric structure. Very interesting results have been obtained. For all ε and all f/f0 the curve can be described by the equation of the form f/f0 = R 2 +R+1 where R is the area ratio. This mathematical model is true up to R=1.27. After this saturation effects set in and the curve changes to a straight line f/f0 = mR+. Further work is being carried out. 
Keywords: LTCC ,Composite Dielectric Constant, area ratio, multilayer structure.