tailieunhanh - THE ENGINEERING THE HANDBOOK - SECOND EDITION II (end)

Tham khảo sách 'the engineering the handbook - second edition ii (end)', khoa học tự nhiên, hoá học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 111 Filters Passive Albert J. Rosa University of Denver Fundamentals Applications. Simple RL and RC Filters Simple RLC Filters Compound Filters Constant- Filters m-Derived Filters A filter is a frequency-sensitive two-port circuit that transmits with or without amplification signals in a band of frequencies and rejects or attenuates signals in other bands. The electric filter was invented during the First World War by two engineers working independently of each other the American engineer G. A. Campbell and the German engineer K. W. Wagner. O. Zobel followed in the 1920s. These devices were developed to serve the growing areas of telephone and radio communication. Today filters are found in all types of electrical and electronic applications from power to communications. Filters can be both active and passive. In this section we will confine our discussion to those filters that employ no active devices for their operation. The main advantage of passive filters over active ones is that they require no power other than the signal to operate. The disadvantage is that they often employ inductors that are bulky and expensive. Fundamentals The basis for filter analysis involves the determination of a filter circuit s sinusoidal steady state response from its transfer function T jw . Some references use H jw for the transfer function. The filter s transfer function T jw is a complex function and can be represented through its gain I T jw I and phase T jw characteristics. The gain and phase responses show how the filter alters the amplitude and phase of the input signal to produce the output response. These two characteristics describe the frequency response of the circuit since they depend on the frequency of the input sinusoid. The signal-processing performance of devices circuits and systems is often specified in terms of their frequency response. The gain and phase functions can be expressed mathematically or graphically as frequency-response plots. .