tailieunhanh - Electromagnetic Waves Propagation in Complex Matter Part 15

Tham khảo tài liệu 'electromagnetic waves propagation in complex matter part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Propagation in Lossy Rectangular Waveguides 267 Results and discussion As shown in Fig. 9 a comparison among the attenuation of the TE10 mode near cutoff as computed by the new method the conventional power-loss method and the measured S21 result was performed. Clearly the attenuation constant az computed from the power-loss method diverges sharply to infinity as the frequency approaches fc and is very different to the simulated results which show clearly that the loss at frequencies below fc is high but finite. The attenuation computed using the new boundary-matching method on the other hand matches very closely with the S21 curve measured using from the VNA. As shown in Table 2 the loss between GHz and GHz computed by the boundarymatching method agrees with measurement to within 5 which is comparable to the error in the measurement. The inaccuracy in the power-loss method is due to the fact that the fields expressions are assumed to be lossless - . kx and ky are taken as real variables. Analyzing the dispersion relation in 23 it could be seen that in order to obtain az kx and or ky must be complex given that the wavenumber in free space is purely real. Although the initial guesses for kx and ky applied in the new boundary-matching method are assumed to be identical with the lossless case the final results actually converge to complex values when the characteristic equations are solved numerically. Fig. 9. Attenuation of TE10 mode at the vicinity of cutoff. matching method. power loss method. the new boundary S21 measurement. Fig. 10 shows the attenuation curve when the frequency is extended to higher values. Here the loss due to TE10 alone could no longer be measured alone since higher-order modes such as TE11 and TM11 etc. start to propagate. Close inspection shows that the loss 268 Electromagnetic Waves Propagation in Complex Matter predicted by the two methods at higher frequencies is in very close agreement. It is therefore sufficed .