A new compact Reconfigurable Frequency Measurement (RFM) device, based on interferometry is presented in this paper. The device combines the advantages of reconfigurability and fractal geometry. The interferometer uses a Wilkinson power divider connected to two microstrip delay lines; one of these corresponds to the second iteration of the Hilbert fractal curve. PIN diode switches are properly placed in the fractal delay line to achieve a 3-bit circuit, which operates in the 2.7-4.5 GHz range. The design and simulations presented are done using a full wave EM simulator, and the frequency responses of the circuit are then shown and compared to measured results.
A planar sensor designed using the fourth Hilbert fractal curve iteration for solid material characterization at multiple frequencies is reported in this paper. The fractal curve is self-similar with space filling properties. The Hilbert fractal geometry is used to form a compact resonator, with a multiband frequency response where miniaturization is achieved, since a large transmission line length is effectively confined in a limited area. The sensor provides five resonances in the frequency range from 0 to 5 GHz. The resonant frequencies are 0.56, 1.68, 2.72, 3.69 and 4.72 GHz, all used to measure the real permittivity of known samples with a sensitivity of 7, 20, 27, 43 and 50 MHz/permittivity, respectively. The sensor is used to measure dielectric samples with 20 x 20 mm 2 areas with several thicknesses. Simulations and measurements demonstrate that the Hilbert fractal geometry can be used to design a multiband planar sensor for solid dielectric material characterization.
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