TABLE OF CONTENTS The most common network measurement is characterizing the transmission through a device. In many electronic systems, the response at the output of a system block due to a signal at the input is a critical parameter. For distortionless transmission through a device, the output signal must be identical to the input signal, perhaps delayed in time and scaled in amplitude. This implies the device must have a flat amplitude response and a linear phase response. These criteria are not usually completely met, but can be approached in practice.
Measurement error is introduced into transmission measurements via a variety of mechanisms. These error mechanisms can be quantified so that the quality of the measurement is known.
A system or network is called distortionless if its output is an exact replica of its input, except for amplitude scaling and time delay. Put mathematically,
| (15-1) |  |
where
| y( t) | = | output signal |
| x( t) | = | input signal |
| k | = | amplitude scale factor |
| t 0 | = | time delay in the system |
Note that k and t 0 are constants and are not allowed to be a function of frequency. Figure 15-1 shows an example of input and output signals of a linear system. The input pulse has an amplitude of 1 and a pulse width of T. The output is the same shape as the input but is delayed by t 0 and the amplitude of the output has been changed by the amplitude...
