TAILIEUCHUNG - Development and Implementation of RFID Technology Part 2

Tham khảo tài liệu 'development and implementation of rfid technology part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Design of Antennas for RFID Application 21 be the antenna impedance normalized to the real part of the chip impedance then 2 Za - 1 2 or s Za - 1 Za 1 Za 1 21 On the basis of the transformation the traditional Smith Chart can be used to describe the impedance match between the antenna and the chip. Za can be marked according to its real part and imaginary part on Smith Chart like the traditional normalized impedance. The distance between the point of each Za and the centre point of Smith Chart expresses the magnitude of the complex power reflection coefficient s while the trace of impedance points which have a constant distance to the centre point forms the concentric circle which is called as the equivalent power reflection circle. The centre point of Smith Chart is the perfect impedance match point while the most outer circle denotes the complete mismatch case . s 1 . The power transmission coefficient Rao Nikitin Lam 2005b can also be defined as T and Pc PaT where Pa stands for the power from reader caught by tag antenna Pc the power transmitted from the tag antenna to the tag chip. It follows from Fig. 3 that 4R R __ T 2 0 T 1 22 Z z T s 2 1 - a Q C then equation of the circle with constant Rc Rc 23 X Let Xa R transmission coefficient is expressed as follows. power r a 2 4 r - 2 - 1 2 Xa Qc 2 Ặ 1 -T T T 24 From equation 24 the impedance chart with the constant power transmission coefficient is draw as shown in Fig. 4. In Fig. 4 the x axis expresses the normalized real part ra Ra Rc and y axis the normalized imaginary part Xa Xa Rc . The circles with constant power transmission coefficients T 1 are draw in Fig. 4. The x axis is called as the resonant line with Xa - Xc while the y axis is called as the complete mismatch line. When T s decrease the radius of the circles with constant power transmission coefficient increase. While T 0 the circle with constant power transmission coefficient approaches to its tangent that is the y axis on

TÀI LIỆU LIÊN QUAN
69    272    11
TỪ KHÓA LIÊN QUAN
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.