For demodulation In general: 1. Synchronous (coherent) demodulation Receiver generates a local carrier/oscillator . It combines/multiplies the received signal with that carrier. Then a filter extracts the message. Received signal ↓ × Local oscillator ↓ Low-pass filter ↓ Message So yes, carrier multiplication is a common implementation of synchronous demodulation . 2. Asynchronous (non-coherent) demodulation Receiver doesn't need a phase-synchronized local carrier . It uses properties of the received signal itself to recover the information. For ASK , an envelope detector is the classic example: ASK signal ↓ Diode + RC ↓ Envelope ↓ Comparator ↓ Data Modulation Synchronous demodulation Non-coherent/asynchronous demodulation ASK/OOK Local carrier + multiplier Envelope detector AM Product detector Envelope detector FSK Coherent correlator/mixer Frequency discriminator, filters, etc. PSK Local synchronized carrier + multiplier Differential/n...

PSK Demodulation Instructions for Phase Shift Keying Modulation (PSK) Step 1: Click on 'Generate Message' button to generate input message signal Step 2: Then click on 'Generate Carrier' button to generate carrier signal Step 3: You can change the carrier signal frequency from the input fields Step 4: Click on 'Simulate PSK' button to generate Phase Shift Keying Signal Carrier Frequency in Hz: π π/2 Sampling Frequency in Hz: ...

  A VCO (Voltage-Controlled Oscillator) does not inherently produce only FM signals. However, it can be used as a direct FM generator when the message signal is applied to its control input. How a VCO Produces FM A VCO has a control-voltage-to-frequency relationship given by: \[ f_i(t) = f_c + k_f v(t) \] where: f c = carrier or center frequency v(t) = input/control voltage k f = frequency sensitivity of the VCO (Hz/V) f i (t) = instantaneous frequency Suppose the message signal is: \[ m(t) = A_m \cos(2\pi f_m t) \] If the message signal is applied directly to the VCO control input, then: \[ v(t) = m(t) \] Therefore, the instantaneous frequency becomes: \[ f_i(t) = f_c + k_f A_m \cos(2\pi f_m t) \] This means that the instantaneous frequency continuously moves above and below the center frequency f c according to the ...

Feeding Baseband Signal to VLC IM/DD Transmitter *VLC IM/DD = Intensity Modulation / Direct Detection If you feed a baseband amplitude signal (like your raw voltage/time waveform) directly into a VLC transmitter (LED), will the system automatically handle it, or do you need extra steps. Let’s go carefully. 1. VLC with IM/DD works in intensity VLC using IM/DD only cares about the light intensity (optical power), not the phase or frequency. Your signal must modulate the LED’s intensity . If your signal is already baseband , that’s fine — it can directly drive the LED as long as : The signal is unipolar (LED can only emit positive light intensity). Most baseband signals are bipolar (positive and negative). LEDs cannot handle negative current. You’ll need to add a DC bias so the entire signal is positive. x_LED(t) = x_signal(t) + I_bias (ensure x_LED(t) > 0) The signal amplitude is withi...

PSK Waveform Generator Standard: Phase Shift Keying (PSK) Messsage Bits Carrier Frequency (Hz) 500 Hz Sampling Frequency (Hz) 500 Hz num_bits: 500 Hz Bit Rate in bps: 500 Hz π π/2 Step 1: messagePlot Step 2: carrierPlot $c(t) = A_m\cos(2\pi f_c1 t)$ Step 3: Super...

FSK Demodulation Instructions for Frequency Shift Keying Modulation (FSK) Step 1: Click on 'Generate Message' button to generate input message signal Step 2: Then click on 'Generate Carrier' button to generate carrier signal Step 3: You can change the carrier signal frequencies from the input fields Step 4: Click on 'Simulate FSK' button to generate Frequency Shift Keying Signal Carrier Frequency 1 in Hz: Carrier Frequency 2 in Hz: ...

FSK Waveform Generator Standard: Frequency Shift Keying (FSK) Messsage Bits Carrier Frequency (Hz) 500 Hz Carrier Frequency (Hz) 500 Hz Sampling Frequency (Hz) 500 Hz Bit Rate in bps: 500 Hz Step 1: messagePlot Step 2: carrierPlot $c(t) = A_m\cos(2\pi f_c1 t)$ Step 2: carrierPlot $c(t) = A_m\cos(2\pi f_c2 t)$ Step 3: Superimposed Signal $x(t) = [c(t) + Binary Message Bits]$ ...