Answer:

• Analysis of the waveform means determination of the values of amplitude, frequency and sometime phase angle of the harmonic components.
• A wave analyzer, in fact, is an instrument designed to measure relative amplitudes of single frequency components in a complex waveform. Basically, the instrument acts as a frequency selective voltmeter which is used to the frequency of one signal while rejecting all other signal components. The desired frequency is selected by a frequency calibrated dial to the point of maximum amplitude. The amplitude is indicated either by a suitable voltmeter or CRO.
• This instrument is used in the MHz range. The input signal to be analysed is heterodyned to a higher IF by an internal local oscillator. Tuning the local oscillator shifts various signal frequency components into the pass band of the IF amplifier. The output of the IF amplifier is rectified and is applied to the metering circuit. The instrument using the heterodyning principle is called a heterodyning tuned voltmeter.

• The block schematic of the wave analyser using the heterodyning principle is shown in fig. below. The operating frequency range of this instrument is from 10 kHz to 18 MHz in 18 overlapping bands selected by the frequency range control of the local oscillator. The bandwidth is controlled by an active filter and can be selected at 200, 1000, and 3000 Hz.

   

• The input signal is given to the instrument with the help of a probe connector which contains a unity-gain isolation amplifier.
• The input signal is Heterodyned in the mixer stage with the signal from a local oscillator after appropriate attenuation.
• Output of the mixer makes an intermediate frequency which is uniformly amplified by the 30-MHz IF amplifier.
• Then,this amplified IF signal is mixed again with a 30-MHz crystal oscillator signal,that causes information centered on a zero frequency.
• Then,an active filter with controlled bandwidth and symmetrical slopes of 72dB per octave passes the chosen components to the meter amplifier and detector circuit.
• The output from the meter detector can be read off a decibel calibrated scale or can be given to a recording device.