Introduction:
Microwave communication refers to the transmission of information or signals using electromagnetic waves with frequencies ranging from 1 GHz to 300 GHz. These waves have shorter wavelengths compared to radio waves and are used for various applications such as satellite communication, radar systems, wireless networks, and more. In microwave communication, various modulation techniques are employed to transmit and receive signals effectively.

Pulse Modulation:
Pulse modulation is a technique where the amplitude, duration, or position of a pulse is varied to represent the information being transmitted. It includes various modulation techniques such as pulse amplitude modulation (PAM), pulse width modulation (PWM), and pulse position modulation (PPM). However, pulse modulation is not commonly used in the microwave band due to various factors such as limited bandwidth and susceptibility to noise.

Amplitude Modulation:
Amplitude modulation (AM) is a technique where the amplitude of the carrier wave is varied in proportion to the message signal being transmitted. It is commonly used in radio broadcasting but is not suitable for microwave communication. This is because the microwave band requires a larger bandwidth for efficient transmission, and AM modulation results in a wide bandwidth occupancy.

Frequency Modulation:
Frequency modulation (FM) is a technique where the frequency of the carrier wave is varied in accordance with the message signal. FM modulation is commonly used in FM radio broadcasting, but it is not the preferred choice for microwave communication. FM modulation requires a larger bandwidth and may suffer from noise and interference issues at higher frequencies.

Phase Modulation:
Phase modulation (PM) is a technique where the phase of the carrier wave is varied based on the message signal. PM is widely used in microwave communication due to its advantages over other modulation techniques. It provides better noise immunity, efficient bandwidth utilization, and resistance to multipath fading. Phase modulation is commonly used in microwave links, satellite communication, radar systems, and more.

Conclusion:
In the microwave band, pulse modulation, amplitude modulation, and frequency modulation are not commonly used due to their limitations in bandwidth occupancy and susceptibility to noise. Phase modulation, on the other hand, is widely used in microwave communication due to its superior performance and advantages over other modulation techniques.