الفهرس 
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Abstract
In this thesis, a new stepped impedance resonator (SIR) based chipless RFID tag is introduced for the implementation of compact tags with high spectral efficiency. The proposed tag provides a 12-bits encoded data within a physical dimension of (𝟏9 × 𝟏4.𝟓) 𝒎𝒎𝟐. Thereby, its design provides a bit density of 4.5 bit/𝒄m𝟐. Each encoded data sequence is represented as a unique spectral selection in the frequency domain within the frequency band from 𝟓.𝟒 to 𝟏3.𝟕 𝑮HZ. The resonator components are arranged as two typical sets of nested concentric loops. The proposed peculiar geometry and resonant element orientation would reduce the inter-resonator coupling, allowing higher bit density as well as stable oblique angular output to be achieved. The multi resonators are fabricated on a lossy FR4 substrate having a dielectric constant 𝜺𝒓= 𝟒., loss tangent 𝜹=𝟎.𝟎25, and thickness 𝒉=𝟏.𝟔 𝒎𝒎. The measurement results and simulations of the radar cross section (RCS) response of the tag are highly matched. The last designed tag is fabricated on TaconicTLX-8 (lossy) substrate with thickness h
and loss tangent 𝜹=0.00017). The tag design is performed using CST- Microwave Studio software. The proposed tag introduces 30-bit code word within the frequency range from 4.82 to 8.62 GHz with an overall bandwidth of 3.8 GHz. This design increases the number of bits which increases the number of users. However, it reduces the overall bandwidth and so we increase the spectral efficiency. In order to reduce the coupling effect between resonators and to produce a more robust response, in a multi-resonator design the distances between columns and scaling of each column of resonators is optimized.