The block diagram illustrates the process of synchronous (coherent) demodulation , a method used to recover the original message signal from an Amplitude Modulated (AM) waveform.    Modulated AM Signal Input: The input signal is given by: \( s(t) = A_c \left[1 + K_a m(t)\right] \cos(2\pi f_c t) \) Where: \( A_c \): Carrier amplitude \( f_c \): Carrier frequency \( m(t) \): Message (modulating) signal \( K_a \): Amplitude sensitivity constant The Product Modulator (Multiplier) The core of synchronous demodulation is multiplying the incoming AM signal \( s(t) \) with a locally generated carrier signal \( c(t) \). For ideal demodulation, this local carrier must be a perfect replica of the original transmitter's carrier in both **frequency and phase**: \( c(t) = \cos(2\pi f_c t + \phi) \) Here, for perfect synchronization, the phase offset \( \phi \) must ideally be zero. Any deviation from th...

    The diagram shows a Phase-Locked Loop (PLL) based PM demodulator . Here's how each component functions together to retrieve the original message signal: Input signal \( a(t) \): This is the received PM signal \( S(t) \), typically in the form: \( S(t) = A_c \cos\left[ 2\pi f_c t + K_p m(t) \right] \) PD (Phase Detector): Compares the phase of the received PM signal with the phase of the signal from the VCO (Voltage Controlled Oscillator). Outputs a voltage proportional to the phase difference, which directly relates to the modulating signal \( m(t) \). The primary function of the PLL in this context is to continuously track the instantaneous phase variations of the input signal. F(s): The loop filter smooths the phase detector output, improving the dynamic response and reducing high-frequency noise. For PM demodulation, a high-pass or differentiating filter may not be needed, unlike in FM, because the phase detector directly provides the demodu...

The diagram illustrates a Phase-Locked Loop (PLL) used for demodulating Frequency Modulated (FM) signals. The working of each block is described below:   Input signal: This is the received FM signal, typically denoted as s(t) , which carries the frequency variations corresponding to the original message m(t) .   PD (Phase Detector): Compares the phase of the input signal with that of the feedback signal generated by the VCO . The output is a signal proportional to the phase difference or error. F(s) (Loop Filter): Processes the phase error signal from the PD. It smooths the signal to eliminate high-frequency components and to ensure loop stability. This filter also helps determine the **capture range** (the frequency range over which the PLL can acquire lock) and the **lock range** (the frequency range over which the PLL can maintain lock). VCO (Voltage Controlled Oscillat...

APPARATUS : 1. TIMS-301 Modelling System 2. C.R.O (20MHz) 3. Spectrum Analyzer 4. Connecting chords & probes. AM Signal, S(t) = E(1 + m·cos(μt)) · cos(ωt) Where, E is the amplitude of the AM signal μ is the frequency of the message signal (in rad/s) ω is the frequency of the carrier signal (in rad/s) m is the modulation index (varies from 0 to 1) = {A(1 + m·cos(μt))} × {B·cos(ωt)} = {low frequency term a(t)} × {high frequency term c(t)} The low frequency term can be considered as: a(t) = DC + m(t) Using an adder, we try to keep the modulation index or modulation depth exactly 100%. Figure: AM, with m = 1 For example, if we set DC voltage to A volts and the amplitude of the AC part as A·m, then the ratio is 1 at the adder output, indicating 100% amplitude modulation. Circuit Diagram Figure: AM Circuit PROCEDURE : 1. Generate a message signal from the AUDIO OSCILLATOR module. The oscillator ...

Power Distribution In practice, the AM wave s(t) is a voltage or current signal. In either case, the average power delivered to a 1-ohm load resistor by s(t) is comprised of three components: Carrier power = (1/2) A c 2 Upper side-frequency power = (1/8)μ 2 A c 2 Lower side-frequency power = (1/8)μ 2 A c 2 The ratio of the total sideband power to the total power in the modulated wave is therefore equal to μ 2 / (2 + μ 2 ), which depends only on the modulation factor μ. If μ = 1, that is, 100% modulation is used, the total power in the two side-frequencies of the resulting AM wave is only one-third of the total power in the modulated wave. A major topic in Amplitude Modula...

  Let's assume your original message signal is: 1, 0, 1, 1, 1, 0, 1, 1, 0, 1. If you want to modulate it using 4-QAM, then your baseband signal will be: 4-QAM Symbols (Real + jImag) Symbol 0: -1.00 + j-1.00 Symbol 1: 1.00 + j-1.00 Symbol 2: -1.00 + j-1.00 Symbol 3: 1.00 + j-1.00 Symbol 4: 1.00 + j1.00   Now, if you want to transmit them through a typical wireless medium, you need to modulate the baseband signal with a carrier frequency (in our case, 50 Hz). The resulting passband signal looks like this               In the above code, the symbol rate is 5 symbols per second.   Detailed explanation 4-QAM Constellation Points In typical normalized 4-QAM, each symbol is mapped to a complex number: Bits Symbol (I + jQ) 00 -1 - 1j 01 -1 + 1j 11 +1 + 1j 10 +1 - 1j Each point lies on a square centered at the origin with I and Q values either +1 or -1. ...

Constellation Diagram of M-ary QAM Bitstream (e.g. 1,0,1,1): Generate Message Modulation Order (M): M must be a power of 2 and square (e.g., 4, 16, 64) Plot Constellation Diagram Explore Signal Processing Simulations   Further Reading   Online Simulator for M-ary PSK Constellation Online Simulator for M-ary QAM Signal Generator  Online Simulator for ASK, FSK, and PSK   Explore DSP Simulations

Constellation Diagram of M-ary PSK Bitstream (e.g. 1,0,1,1): Generate Message Modulation Order (M): M must be a power of 2 (e.g., 2, 4, 8, 16) Plot Constellation Diagram Explore Signal Processing Simulations Further Reading   Online Simulator for M-ary PSK Online Simulator for ASK, FSK, and PSK   Explore DSP Simulations

M-ary QAM Bitstream (e.g. 1,0,1,1): Generate Message Carrier Frequency (Hz): Generate Carrier Modulation Order (M): M must be a power of 2 and square (e.g., 4, 16, 64) Generate Modulated Signal Demodulate Further Reading   Online Simulator for M-ary PSK Online Simulator for ASK, FSK, and PSK   Explore DSP Simulations  

M-ary PSK Bitstream (e.g. 1,0,1,1): Generate Message Carrier Frequency (Hz): Generate Carrier Modulation Order (M): M must be a power of 2 (e.g., 2, 4, 8, 16) Generate Modulated Signal Demodulate Explore Signal Processing Simulations Further Reading   Online Simulator for ASK, FSK, and PSK Amplitude Modulation Simulator Frequency Modulation Simulator  Phase Modulation Simulator  Explore DSP Simulations  

Phase Modulation Message Frequency (Hz): Generate Message Carrier Frequency (Hz): Generate Carrier Message Signal Amplitude: Carrier Signal Amplitude: Generate Modulated Signal Demodulate Further Reading   Amplitude Modulation Simulator Frequency Modulation Simulator  Explore DSP Simulations  

Frequency Modulation Message Frequency (Hz): Generate Message Carrier Frequency (Hz): Generate Carrier Message Signal Amplitude: Carrier Signal Amplitude: Generate Modulated Signal Demodulate Further Reading  Amplitude Modulation Simulator Phase Modulation Simulator  Explore DSP Simulations  

Amplitude Modulation Message Frequency (Hz): Generate Message Carrier Frequency (Hz): Generate Carrier Gain A: Gain B: Generate Modulated Signal Demodulate

Low and High Level Modulation Simulator Message Frequency (Hz): Carrier Frequency (Hz): Amplification Factor: Run Simulation

📘 Overview 🧮 DSB-SC Modulator 🧮 DSB-SC Detector 🧮 Comparisons Between DSB-SC and SSB-SC 📚 Further Reading   Double-sideband suppressed-carrier transmission (DSB-SC) is transmission in which frequencies produced by amplitude modulation (AM) are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed. In the DSB-SC modulation, unlike in AM, the wave carrier is not transmitted; thus, much of the power is distributed between the sidebands, which implies an increase of the cover in DSB-SC, compared to AM, for the same power use. DSB-SC transmission is a special case of double-sideband reduced carrier transmission. It is used for radio data systems. This model is frequently used in Amateur radio voice communications, especially on High-Frequency bands.   ...

📘 Overview 🧮 SSB-SC Modulator using Hilbert Transform 🧮 Other SSB-SC Modulators 🧮 SSB-SC Detector 📚 Further Reading   As we see in case of DSB-SC only sidebands are transmitted as they bear all informations about the signal. On the other hand, the two sidebands are identical and they carry same information. So, why not just send a single sideband and construct the other sideband from that.     SSB-SC Modulator using Hilbert Transform Single-sideband has the mathematical form of quadrature amplitude modulation (QAM) in the special case where one of the baseband waveforms is derived from the other, instead of being independent messages: S ssb (t) = s(t).cos(2πf 0 t) - (t).sin(2πf 0 t) Where s(t) is the message (real valued), (t) is the Hilbert transform, and f 0 is the radio carrier frequency.   To und...