Contents
- 1 What is the effect of noise signal in the comparator?
- 2 Why is a square wave so much louder than a sine wave of the same amplitude and frequency?
- 3 Why is a comparator adversely affected by a noisy input signal?
- 4 Why does a square wave have phase noise?
- 5 How is phase noise related to frequency stability?
- 6 How can I reduce the noise in my comparator?
What is the effect of noise signal in the comparator?
A comparator normally changes its output state when the voltage between its inputs crosses through approximately zero volts. Small voltage fluctuations due to noise, always present on the inputs, can cause undesirable rapid changes between the two output states when the input voltage difference is near zero volts.
Why is a square wave so much louder than a sine wave of the same amplitude and frequency?
Square waves contain more energy because not only do you have the fundamental frequency, but you have all the odd harmonics. The fundamental would have the same amplitude as a sine wave and will be the highest amplitude of all the harmonics, so it should travel farther per se.
What is the best way to manage excessive noise levels?
The exposure to noise can be reduced by eliminating the source of noise (if possible), substituting the source with a quieter one, applying engineering modifications, using administrative controls, and by using protective equipment. The best way to reduce exposure to noise is to engineer it out at the design stage.
Why is a comparator adversely affected by a noisy input signal?
voltage may cause a comparator to erratically switch output state. Fig. 3 shows the output of a com- parator when a noise signal (of the variance of only one promile of sine wave amplitude at the input of the comparator) is super- imposed on the zero reference voltage.
Why does a square wave have phase noise?
The comparator is supposed to be ideal and has a hysteresis which is much larger than the noise signal, thus there is no ringing at the zero crossings of the sine wave. Yet due to the noise on the input signal, the comparator switches slightly earlier or later as it would for a clean sine wave, hence the produced square wave has some phase noise.
Why does the comparator switch early on a sine wave?
Yet due to the noise on the input signal, the comparator switches slightly earlier or later as it would for a clean sine wave, hence the produced square wave has some phase noise. The plot below illustrates this behavior: the blue curve is the noisy input sine wave and the yellow curve is the square wave generated by the comparator.
It is implicit in this general definition of frequency stability that the stability of a given frequency decreases if anything except a perfect sine function is the signal wave shape. Phase noise is the term most widely used to describe the characteristic randomness of frequency stability.
How can I reduce the noise in my comparator?
As an advice, you could reduce the noise by adding a low-pass filter to your design before going into the comparator. This would cut-off the higher frequencies of your signal which is the noise in this case. To calculate the frequency of the phase noise, you can use FFT or perform a spectrum analysis of the signal.