Skip to main content

Comparing Baseband and Passband Implementations of ASK, FSK, and PSK


 

Baseband modulation techniques are methods used to encode information signals onto a baseband signal (a signal with frequencies close to zero). Passband techniques shift these signals to higher carrier frequencies for transmission. Here are the common implementations:

Amplitude Shift Keying (ASK) [↗] :

In ASK, the amplitude of the signal is varied to represent different symbols.
Binary ASK (BASK) is a common implementation where two different amplitudes represent binary values (0 and 1).
ASK is simple but susceptible to noise.

ASK Baseband (Digital Bits)


ASK Passband (Modulated Carrier)

 
 
Fig 1:  ASK Passband Modulation (Get MATLAB Code)

In Figure 1 above, you can see binary information bits are used to switch a high-frequency carrier signal on and off. That's why this result is called a passband signal.


Frequency Shift Keying (FSK) [↗] :

FSK modulates the frequency of a carrier to represent digital data.
In binary FSK (BFSK), two different frequencies represent binary values.
FSK is less susceptible to noise compared to ASK but requires more bandwidth.


FSK Baseband (Mapping)


FSK Passband

For passband FSK modulation, we modulate bit '0' with a lower frequency carrier signal and bit '1' with a higher frequency carrier signal to prepare it for wireless transmission.

 

 
Fig 2: Frequency Modulation (Passband) (Get MATLAB Code from here)

In Figure 2 above, you can see binary information bits '1's and '0's are represented by high-frequency carrier oscillations. This is the passband signal.

Phase Shift Keying (PSK) [↗] :

PSK varies the phase of a carrier signal to represent symbols. For example, we can map binary bit '0' to '-1' and bit '1' to '+1' in baseband before shifting to a carrier.
Binary PSK (BPSK) uses two different phase shifts (usually 180 degrees apart) to represent binary values.
PSK is robust against noise and more bandwidth-efficient than ASK and FSK.

PSK Baseband


PSK Passband 

Fig 3: BPSK Modulation (Passband) 

In Figure 3 above, the binary information bits '1's and '0's are represented by phase shifts of a high-frequency carrier signal. A '0' might correspond to a carrier with 0° phase, while a '1' corresponds to a carrier with 180° phase. This results in the passband BPSK signal, where the amplitude remains constant but the phase flips according to the input bits.


Baseband vs. Passband QAM

Quadrature Amplitude Modulation (QAM) [↗] :

QAM combines ASK and PSK by varying both amplitude and phase of a carrier signal.
In QAM, each symbol represents a combination of amplitude and phase, allowing for higher data rates.
Higher-order QAM (e.g., 16-QAM, 64-QAM) increases the number of symbols and data rates but requires more complex receiver designs.

Pulse Amplitude Modulation (PAM) [↗] :

PAM encodes information in the amplitude of pulses in the baseband signal.
PAM is often used in digital communication systems where digital data is encoded into pulse amplitudes.

Orthogonal Frequency Division Multiplexing (OFDM) [↗] :

OFDM divides the baseband data into multiple narrowband subcarriers, each modulated using PSK or QAM.


OFDM is widely used in modern communication systems such as Wi-Fi, LTE, and digital television (DVB, ATSC) due to its robustness against frequency-selective fading and ability to mitigate intersymbol interference.

These modulation techniques play crucial roles in various communication systems, each with its advantages and limitations depending on the specific application requirements such as bandwidth efficiency, spectral efficiency, robustness against noise, and complexity of implementation. 

 

Further Reading

  1.  Comparing Baseband and Passband Implementations of m-ary QAM
📊 MATLAB & ONLINE SIMULATIONS (Web-Based)
🎓 GATE & UGC - NET SOLUTIONS
📡 WIRELESS & SIGNAL PROCESSING


Contact Us

Name

Email *

Message *

Popular Posts

Hybrid Beamforming | Page 1

Beamforming Techniques Hybrid Beamforming... Page 1 | Page 2 | Hybrid Beamforming: Hybrid beam formation was developed to address some of the limitations of digital pre-coding approaches. Every antenna element is connected to an RF chain in digital pre-coding (beam forming) method. We also know that each RF chain is in charge of providing a separate data stream between the transmitter and the receiver. We know that a larger number of independent data streams leads to higher data rates. It has a spatial multiplexing feature for MIMO. As a result, we may assume that switching from MIMO to massive MIMO will benefit us more in terms of spatial multiplexing in massive MIMO, where each antenna is coupled to a single RF chain. We'll proceed with a definition of hybrid beam forming. Overview of hybrid beam forming with example: Unlike digital beam forming, more than one antenna element is connected to a single RF chain in hybr...
Read more

UGC NET Electronic Science Previous Year Question Papers with Solutions

Home / Engineering & Other Exams / UGC NET 2026 PYQ ⬇️ Download Papers and Solutions 📋 Exam Pattern 💡 Preparation Tips ❓ FAQs 📊 Exam Highlights: Electronic Science (88) Feature Details Junior Research Fellowship (JRF) ₹37,000 + HRA per month Eligibility M.Sc/M.Tech in Electronics (55%) Validity of Certificate JRF (3 Years) | Lectureship (Lifetime) 📥 Download UGC NET Electronics PDFs Complete collection of previous year question papers, answer keys and explanations for Subject Code 88. Start Downloading 📂 View All Question Papers June 2025 - Question Paper Download PDF June 2025 - Solved Paper + Explanation ...
Read more

MATLAB Code for Rms Delay Spread

RMS delay spread is crucial when you need to know how much the signal is dispersed in time due to multipath propagation, the spread (variance) around the average. In high-data-rate systems like LTE, 5G, or Wi-Fi, even small time dispersions can cause ISI. RMS delay spread is directly related to the amount of ISI in such systems. RMS Delay Spread [↗] Delay Spread Calculator Enter delays (ns) separated by commas: Enter powers (dB) separated by commas: Calculate   The above calculator Converts Power to Linear Scale: It correctly converts the power values from decibels (dB) to a linear scale. Calculates Mean Delay: It accurately computes the mean excess delay, which is the first moment of the power delay profile. Calculates RMS Delay Spread: It correctly calculates the RMS delay spread, defined as the square root of the second central moment of the power delay profile.   MATLAB Code  clc...
Read more

Comparisons among ASK, PSK, and FSK (with MATLAB + Simulator)

Modulation ASK, FSK & PSK Constellation MATLAB Simulink MATLAB Code Comparisons among ASK, PSK, and FSK 📘 Comparisons among ASK, FSK, and PSK 🧮 Online Simulator Bandwidth 🧮 MATLAB Code BER Analysis 📚 Further Reading 📂 View Other Topics on Comparisons among ASK, PSK, and FSK ... 🧮 Comparisons of Noise Sensitivity, Bandwidth, Complexity, etc. 🧮 MATLAB Code for Constellation Diagrams of ASK, FSK, and PSK 🧮 Online Simulator for ASK, FSK, and PSK Generation 🧮 Online Simulator for ASK, FSK, and PSK Constellation 🧮 Some Questions and Answers Comparisons among ASK, PSK, and FSK Comparison among ASK, FSK, and PSK Parameters ASK FSK PSK Variable Characteristics Amplitude ...
Read more

Advanced M-ary Modulation Simulator: Constellation, min dist, Efficiency, SER, EVM (RMS)

Advanced M-ary Communication Lab Analytical & Statistical Performance of Digital Modulation Theoretical Probability of Error (\(P_s\)) \[ P_s = Q\left(\sqrt{\frac{2 E_b}{N_0}}\right) \] Modulation (M-ary) BPSK (M=2) QPSK (M=4) 8-PSK (M=8) 16-QAM (M=16) 64-QAM (M=64) 256-QAM (M=256) SNR (\(E_b/N_0\)): 12 dB Efficiency 2 bps/Hz Min Dist (\(d_{min}\)) 1.41 Symbol Error 1.2e-5 EVM (RMS) 0.0% Constellation Diagram Noise PDF & Decision Tail 1. Geometric Mapping ...
Read more

Channel Impulse Response (CIR) (with MATLAB + Simulator)

📘 Overview & Theory 📘 How CIR Affects the Signal 🧮 Online Channel Impulse Response Simulator 🧮 MATLAB Codes 📚 Further Reading What is the Channel Impulse Response (CIR)? The Channel Impulse Response (CIR) is a concept primarily used in the field of telecommunications and signal processing. It provides information about how a communication channel responds to an impulse signal. It describes the behavior of a communication channel in response to an impulse signal. In signal processing, an impulse signal has zero amplitude at all other times and amplitude ∞ at time 0 for the signal. Using a Dirac Delta function, we can approximate this. Fig: Dirac Delta Function The result of this calculation is that all frequencies are responded to equally by δ(t) . This is crucial since we never know which frequenci...
Read more

Frequency Shift Keying (FSK) Modulation & Demodulation (with Simulation)

Frequency Shift Keying (FSK) Theoretical Foundations: Frequency Shift Keying (FSK) is a discrete frequency modulation scheme wherein the digital information is encoded via instantaneous shifts in the carrier signal's frequency. The fundamental implementation is Binary FSK (BFSK), which maps binary data onto two distinct, discrete spectral states. A binary '1' (the "mark" state) is represented by a carrier frequency \( f_1 \), while a binary '0' (the "space" state) corresponds to frequency \( f_2 \). Each symbol is sustained for a bit interval denoted by \( T_b \). FSK Transmitter Characterization: The mathematical model for the modulated BFSK output \( s(t) \) is defined as: \[ s(t) = \begin{cases} A_c \cos(2\pi f_1 t), & \text{for } m = 1 \\ A_c \cos(2\pi f_2 t), & \text{for } m = 0 \end{cases} \] ...
Read more