Noise Power

Noise power is the power contained in the noise signal. In communication systems, it is desirable to minimize the noise power to improve the overall system performance and reduce the impact of noise on the received signal.

Filter

A filter is an electronic circuit that allows certain frequencies to pass through while attenuating others. It is commonly used in communication systems to shape the frequency spectrum of the signals.

Modulator

A modulator is a device or circuit that converts the information signal into a carrier signal suitable for transmission. It combines the information signal with the carrier signal to produce a modulated signal.

Demodulator

A demodulator is a device or circuit that extracts the information signal from the modulated carrier signal at the receiving end.

Minimizing Noise Power

To minimize the noise power, a filter is introduced before demodulator. This is because:

1. Noise Filtering: By introducing a filter before demodulation, the undesired noise components in the received signal can be attenuated. The filter can selectively remove the noise frequencies, allowing only the desired signal to pass through.

2. Signal-to-Noise Ratio Improvement: Filtering the signal before demodulation can improve the signal-to-noise ratio (SNR). By removing the noise components, the signal power is relatively enhanced compared to the noise power, resulting in a higher SNR. A higher SNR leads to better signal quality and improved system performance.

3. Interference Rejection: Filters can also aid in rejecting interference signals that may be present in the received signal. These interference signals can be from other sources or adjacent channels. By attenuating the interference frequencies, the filter helps in reducing the impact of interference on the demodulated signal.

4. Preventing Noise Amplification: If the filter is introduced after demodulation, it will not be able to remove the noise components that have already been amplified during the demodulation process. Filtering the signal before demodulation prevents the amplification of the noise, minimizing its power.

Therefore, to minimize the noise power and improve the overall system performance, it is necessary to introduce a filter before demodulator.