Tham khảo tài liệu 'advanced microwave circuits and systems part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Remote Characterization of Microwave Networks - Principles and Applications 449 corresponding microstrip implementation - amenable to printing technique - in Fig. 9 b . The scattering antenna - not shown in Fig. 9 b - need to possess properties outlined in Section . The narrow lines Fig. 9 b represent the series inductors and the stubs work as shunt capacitors. By changing the values of these elements the poles and zeros can be controlled as in Section to generate RFID information bits. Stacked Microstrip Patches as Scattering Structure While the previous discussions premised on the separation of the scattering antenna and the one-port we now present an example where the scattering structure does not require a distinguishable one-port. Fig. 10. depicts a set of three there could be more stacked rectangular patches as a scattering structure where the upper patch resonates at a frequency higher than the middle patch. When the upper patch is resonant the middle patch acts as a ground plane. Similarly when the middle patch is resonant the bottom patch acts as a ground plane Bancroft 2004 . Fig. 10 a Fig. 10 b Fig. 10. a Stacked Rectangular Patches as Scattering Structure - Isometric Fig. 10. b Stacked Rectangular Patches as Scattering Structure - Elevation If the patches are perfectly conducting and the dielectric material is lossless the magnitude of the RCS of the above structure could stay nominally fixed over a significant frequency range. As the frequency is swept between resonances the structural scattering tends to maintain the RCS relatively constant over frequency - and therefore is not a reliable parameter for coding information. However the phase and therefore delay undergoes significant changes at resonances. Fig. 11 a and 11 b illustrates this from simulation on the structure of b . The simulation assumed patches to be of copper with conductivity 450 Advanced Microwave Circuits and Systems . 107 S m and the intervening medium had a .
