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Tham khảo tài liệu 'oscilloscopes episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 168 Oscilloscopes Oscilloscopes and optoelectronics Optoelectronics is currently one of the most rapidly advancing areas of electrotechnology. Light is an electromagnetic form of energy like radio frequency energy it can similarly propagate either in free space or in a guided form. At low frequencies electromagnetic energy can be conveyed guided by twin wire circuits while at higher frequencies - roughly 1 to 1000 MHz -coaxial cables are commonly used. In either FM-FDM-analogue or digital form a coaxial cable can carry dozens or even hundreds of simultaneous telephone channels. At microwave frequencies even more telephone channels or many TV channels can be carried transmission being via waveguides guided or narrow beams in free space thanks to the focusing effect of parabolic dish antennas. Figure 8.15 The large display with multiple resizable windows on the HP 16600A and 16700A allows you to see at a glance more of your target system s operation. You can quickly isolate the root cause of system problems by examining target operation across a wide analysis domain from signals to source code courtesy Agilent Technologies a subsidiary of Hewlett-Packard Company Oscilloscopes for special purposes 169 Figure 8.16 The HM5014 spectrum analyser for EMC measurements features a built-in tracking generator and covers 0.15-1050MHz reproduced by courtesy of Hameg Ltd The frequency of lightwaves is thousands of times higher than that of the microwaves currently in common use and consequently even a 1 per cent optical bandwidth represents more channel capacity than is available in the whole of the radio frequency spectrum from d.c. to the highest frequency microwaves. While the terrestrial propagation of lightwaves is heavily constrained by atmospheric attenuation due to molecular absorption dust rain etc. improved optical fibres or Tight pipes have been developed permitting the guided transmission of optical signals over tens of kilometres between repeaters. Such systems are .