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Dielectric Sensing based on Energy Tunneling in Wire-loaded Microstrip Cavities

Dielectric Sensing based on Energy Tunneling in Wire-loaded Microstrip Cavities. Abdullah Nauroze 1 , Omar Sidiqui 2 , Rashad Ramzan 3 and Omar Ramahi 4 1 National University of Computer & Emerging Sciences, Islamabad, Pakistan 2 Taibah University, Madinah, Saudi Arabia

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Dielectric Sensing based on Energy Tunneling in Wire-loaded Microstrip Cavities

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  1. Dielectric Sensing based on Energy Tunneling in Wire-loaded Microstrip Cavities Abdullah Nauroze1, Omar Sidiqui2, RashadRamzan3and Omar Ramahi4 1National University of Computer & Emerging Sciences, Islamabad, Pakistan 2Taibah University, Madinah, Saudi Arabia 3UAE University, Al Ain, UAE 4University of Waterloo, Waterloo, Canada E-mail: abdullah.nauroze@nu.edu.pk

  2. Energy Tunneling The energy propagates only in prescribed directions determined by the relationships between the phase and group (energy) velocities Isotropic energy propagation Tunneling vg vg vp Air vg vg vp Photonic crystal vg Flat Dispersion Surface Spherical Dispersion Surface

  3. 2 fp er= 1- f 2 Types of Dispersion-Based Tunneling • Epsilon-near-zero: Observed in plasmas having anisotropic permittivity • Resonance-type: Observed in periodic structures at band-edges • Length of the wire should be comparable to λ/2 vg vg vg vg vp vg vp Air vg vp Hyperbolic dispersion Periodic structure (wire medium) vg + Plasma f fp + + + + Free Space Epsilon Near Zero Resonance +

  4. Energy Squeezing in Narrow Channels Tunneling allows transmission in narrow channels or ‘energy squeezing’ Narrow Channel Eout Narrow Channel Eout Pout Pout 2 Waveguide 2 Pin 2 Pin Waveguide 2 1 Plasma Waveguide 1 Ein 1 Waveguide 1 Ein • Tunneling properties from port 1 to 2 - Pin  Pout - Phase E1- Phase E2 0 - Frequency-dependent transmission response Pout / Pin (sensing) • Wires should be parallel to the E-field for energy tunneling Example:Two Waveguides connected by a narrow channel filled with wires Pout Pin WG2 WG1 Narrow Channel

  5. Waveguide loaded with wire 2-port Simulations Without wire Power (dB) Pout  0 2 Standing Waves !!! S21 1 Frequency (GHz) S21 Pout With wire Power (dB) Pout  Pin Pin Propagating Waves !!! 2 1 Frequency (GHz)

  6. 12 mm z y x Microstrip implementation Aperture 9 mm Rogers 6002(εr=2.95) 45mm 32mm 80µm Pout 10 mm Conductor Backing z Pin x • More practical – low cost, easier to fabricate, planar • Easier to excite and smaller in size as compared to waveguides • Sample is placed in the aperture • Input impedance 75 Ω

  7. Microstrip implementation • Resonance frequency shifts by 1.335 GHz • 3dB loss due to strip edges

  8. Sensor working • Air vias (that house the sample) are placed at a distance ‘d’ from the wire • By decreasing ‘d’ larger resonant frequency shift is observed due to stronger E-field perturbation • Very sensitive !!! • volume of the via is 0.0031% of the overall volume of the cavity 9 mm 12 mm d • 240µm z x 7.5 mm

  9. Parametric analysis: varying permittivity • Increasing the number of vias increases the resonant frequency shift • Operational bandwidth does not change

  10. Parametric analysis: multiple wires • Uniformly spaced wires with equal length • Bandwidth increases!! • Power is distributed in multiple wires • Multiple resonances • Non-uniform field distribution in microstip lines (Quasi-TEM mode) • Mutual coupling between wires

  11. Parametric analysis: multiple wires • Uniformly spaced wires with different lengths • Multiple resonances • First resonance due to longer wire • Second resonance due to shorter wires • Can be used for multiple frequency sensing 7.5 mm

  12. Conclusion • Various mechanisms of energy tunneling • Energy tunneling in wire-loaded microstrip cavities • Dielectric sensing – by perturbing wire E-field • Parametric study of the sensor

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