QAM is a combination of phase modulation & amplitude modulation.
The most commonly used quadrature amplitude modulation (QAM) is 16-QAM. It combines amplitude and phase modulation to transmit data efficiently by encoding four bits per symbol, represented by 16 different signal points on a constellation diagram. This modulation scheme balances bandwidth efficiency and robustness against noise, making it widely used in digital communication systems, including Wi-Fi and digital television.
The aim is to increase capacity of the system as the signal can be represented using different phase angles as well as amplitude. F.Mmbaga
Quadrature Amplitude Modulation (QAM) is a modulation technique that combines both amplitude modulation and phase modulation to transmit data by varying the amplitude of two carrier waves, thus allowing multiple bits of data to be sent simultaneously. Quadrature Phase Shift Keying (QPSK) is a specific type of phase modulation that encodes data by changing the phase of the carrier signal, allowing for four distinct phase shifts, each representing two bits of information. Both techniques are widely used in digital communication systems, but QAM can transmit more bits per symbol compared to QPSK, making it more efficient in bandwidth utilization.
the maximum amplitude of carrier wave varied with respect to instantaneous values of message signal is called amplitude modulation
In Frequency Modulation (FM), if the modulation frequency is doubled, the modulation index does not necessarily double; it depends on the amplitude of the modulating signal. In Amplitude Modulation (AM), the modulation index is defined as the ratio of the peak amplitude of the modulating signal to the carrier amplitude, so it remains unchanged with varying modulation frequency. For Phase Modulation (PM), similar to FM, the modulation index is influenced by the amplitude of the modulating signal and does not inherently double with the modulation frequency. Thus, modulation frequency and modulation index are not directly linked in this way for FM, PM, or AM.
by maximizing the measurable differences between shifts in phase and amplitude
Differential Phase shift key (DPSK) Quadrature amplitude modulation (QAM)
The most commonly used quadrature amplitude modulation (QAM) is 16-QAM. It combines amplitude and phase modulation to transmit data efficiently by encoding four bits per symbol, represented by 16 different signal points on a constellation diagram. This modulation scheme balances bandwidth efficiency and robustness against noise, making it widely used in digital communication systems, including Wi-Fi and digital television.
Differential Phase shift key (DPSK) Quadrature amplitude modulation (QAM)
The aim is to increase capacity of the system as the signal can be represented using different phase angles as well as amplitude. F.Mmbaga
Without modulation, there's be no way to get any information onto a carrier signal. There are several different types of modulation schemes for radio carriers and almost as many different types demodulators to decode the information so that it can be converted into a usable form. For instance, AM (amplitude modulation), FM (frequency modulation), digital modulation, quadrature amplitude, etc.
Quadrature Amplitude Modulation (QAM) is a modulation technique that combines both amplitude modulation and phase modulation to transmit data by varying the amplitude of two carrier waves, thus allowing multiple bits of data to be sent simultaneously. Quadrature Phase Shift Keying (QPSK) is a specific type of phase modulation that encodes data by changing the phase of the carrier signal, allowing for four distinct phase shifts, each representing two bits of information. Both techniques are widely used in digital communication systems, but QAM can transmit more bits per symbol compared to QPSK, making it more efficient in bandwidth utilization.
AM - Amplitude Modulation FM - Frequency Modulation
In amplitude modulation, modulation depth refers to the ratio of the unmodulated carrier amplitude to the amplitude deviation for which the modulated carrier wave reaches its minimum value. If this minimum value is zero, the modulation depth is 100%.For amplitude modulation,modulation depth = (a-b)/(a+b),wherea is the unmodulated carrier amplitude, andb is the minimum amplitude deviation.The modulation depth ratio is also referred to as the modulation index.
amplitude modulation is where we modulate our signal with a carrier signal amplitude changes but frequency remains constant in amplitude modulation
Frequency modulation have some advantages over amplitude modulation, FM is not sensitive to the amplitude noise, and have high efficient use of transmitted power
Normal frequency range for amplitude modulation is 550kHz to 1610kHz