Доброе время суток doomer#gp!
Цитата(doomer#gp @ Aug 29 2005, 05:48)
"Фотонные кристаллы - материалы с упорядоченной структурой, характеризующейся строго переодическим изменением коэффициента преломления в масштабах сопостовимых с длинами волн видимом и ближнем инфракрасном диапазонах. Будучи прозрачными для широкого спектра электромагнитного излучения, фотонные кристаллы не пропускают свет с длиной волны, сравнимой с периодом структуры кристалла ..... "
То что у вас на втором рис. первого поста и есть эти периодические элементы (pbg) и их характеристические размеры имеют порядок длины волны (СВЧ).
Цитата(doomer#gp @ Aug 29 2005, 05:48)
Я так понимаю, что аналогичная PBG в миллимитровом диапазоне дает переодическое изменение импеданса.
В общем да, это практически аналогично планарным устройствам где используются всякие извращения с шириной и формой краев линии передач.
Всего наилучшего!
PS. Спасибо за рисунок, народ как видно таким образом избавляется от второй и третей гармоник, которые присутствуют в фильтре с обычным граундом.
PSS. А это практическое (для меня более понятное) определение PBG
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 49, NO. 1, JANUARY 2001
A Design of the Low-Pass Filter Using the Novel Microstrip Defected Ground Structure
The PBG research was done in the optical fields originally,
but the PBG structures can be applied to wide frequency
ranges, including the microwave frequency band by properly
scaled dimension. Recently, there has been an increasing
interest in microwave and millimeter-wave applications of
PBG circuits. [1]–[3] The only PBG structures, which have
a periodic structure, have been known as providing rejection
of certain frequency bands, i.e., bandgap effect. [4]–[8] Many
passive and active microwave and millimeter devices have been
developed to suppress the harmonics and realize the compact
physical dimensions of circuits. Several efforts have been made
to realize such devices on a various PBG circuits—e.g., a power
amplifier with PBG circuits [9], [10], the PBG structure for
slow-wave circuits [11], and realization of a magnetic wall in
waveguide [12], [13]; their experimental results are sufficient
to show the validity of PBG circuit applications. However, it is
difficult to use a PBG structure for the design of the microwave
or millimeter-wave components due to the difficulties of the
modeling. There are too many design parameters, which havean
affect on the bandgap property, such as the number of lattice,
lattice shapes, lattice spacing, and relative volume fraction. Another
difficulty in using this PBG circuit is caused by the radiation
from the periodic etched defects.
[1] T. J. Ellis and G. M. Rebeiz, “MM-wave tapered slot antennas on micromachined
photonic bandgap dielectrics,” in IEEE MTT-S Int. Microwave
Symp. Dig., June 1996, pp. 1157–1160.
[2] M. M. Sigalas, R. Biswas, and K. M. Ho, “Theoretical study of dipole
antennas on photonic–crystal substrate,” Microwave Opt. Technol. Lett.,
vol. 13, pp. 205–209, Nov. 1996.
[3] M. P. Kesler, J. G. Maloney, and B. L. Shirley, “Antenna design with
the use of photonic bandgap material as all dielectric planar reflectors,”
Microwave Opt. Technol. Lett., vol. 11, no. 4, pp. 169–174, Mar. 1996.
[4] V. Radisic, Y. Qian, R. Coccioli, and T. Itoh, “Novel 2-D photonic
bandgap structure for microstrip lines,” IEEE Microwave Guide Wave
Lett., vol. 8, pp. 69–71, Feb. 1998.
[5] E. Yablonovitch, “Photonic band-gap structures,” J. Opt. Soc. Amer. B,
Opt. Phys., vol. 10, pp. 283–295, Feb. 1993.
[6] Y. Qian, F. R. Yang, and T. Itoh, “Characteristics of microstrip lines on
a uniplanar compact PBG ground plane,” in Asia–Pacific Microwave
Conf. Dig., Dec. 1998, pp. 589–592.
[7] Y. Qian and T. Itoh, “Planar periodic structures for microwave and millimeterwave
circuit applications,” in IEEE MTT-S Int. Microwave Symp.
Dig., June 1999, pp. 1533–1536.
[8] Y. Qian, V. Radisic, and T. Itoh, “Simulation and experiment of photonic
bandgap structures for microstrip circuits,” in Proc. APMC’97, pp.
585–588.
[9] V. Radisic, Y. Qian, and T. Itoh, “Broadband power amplifier using
dielectric photonic bandgap structure,” IEEE Microwave Guide Wave
Lett., vol. 8, pp. 13–14, Jan. 1998.
[10] , “Broad-band power amplifier integrated with slot antenna and
novel harmonic tuning structure,” in IEEE MTT-S Int. Microwave Symp.
Dig., June 1998, pp. 1895–1898.
[12] K. P. Ma, K. Hirose, F. R. Yang, Y. Qian, and T. Itoh, “Realization of
magnetic conducting surface using novel photonic bandgap structure,”
Electron. Lett., vol. 34, pp. 2041–2042, Nov. 1998.
[13] F. R. Yang, K. P. Ma, Y. Qian, and T. Itoh, “A novel TEM waveguide
using uniplanar compact photonic-bandgap (UC-PBG) structure,” IEEE
Trans. Microwave Theory Tech., vol. 47, pp. 2092–2098, Nov. 1999.
Что такое photonic bandgap (PBG) ?
Aug 28 2005, 17:38
