NAME : ARAVIND C

REG NO : 715523106014
DEPT : B.E ECE(A)- II
COURSE : EC3491 – COMMUNICATION SYSTEMS
DATE : 06.06.2025

Comparison of Radiations in Analog and Digital

Modulation or Demodulation Techniques

Introduction
In wireless communication systems, modulation is a core process where
information signals are superimposed on a carrier wave for transmission. Based
on the nature of the information and system requirements, modulation can be
analog or digital. Each of these techniques results in electromagnetic radiation,
which is emitted into the environment as part of the transmission process.
The characteristics of radiation—such as intensity, coverage, and energy
efficiency—vary significantly between analog and digital systems. This
assignment investigates the differences in radiation between the two techniques
and presents real-world examples to show how technology evolution, especially
in mobile communication, has led to more efficient and safer systems.

Radiation in Communication Systems

Electromagnetic radiation occurs whenever electrical energy is transmitted
through space. In communication systems, this radiation carries the modulated
signals between transmitters and receivers.
Key Radiation Parameters:
 Carrier frequency (f): Determines how far signals can travel and how they
interact with the environment.
 Transmitter Power (P): The amount of power applied to the antenna for
broadcasting the signal.
  Effective Isotropic Radiated Power (EIRP): A standardized way to
compare output by including antenna gain.
 Specific Absorption Rate (SAR): A measure of how much radiation the
human body absorbs from a device (measured in W/kg).
Radiation Regulations:
 FCC (USA) SAR Limit: ≤ 1.6 W/kg
 ICNIRP (International) SAR Limit: ≤ 2.0 W/kg
 Base stations typically must keep public exposure below 10 W/m²

Analog Modulation Techniques and Radiation Characteristics

Techniques:
 Amplitude Modulation (AM): Modifies the amplitude of the carrier.
 Frequency Modulation (FM): Changes the frequency based on signal
input.
 Phase Modulation (PM): Alters the phase to carry data.
Radiation Characteristics:
 Continuous Radiation: Analog systems transmit even in silence (e.g., idle
FM broadcast).
 High Power Output: Common analog transmitters operate at 0.6–2 W
(phones) and up to 100 kW (broadcast towers).
 Wide Bandwidth Use: FM requires ~200 kHz per channel.
 Low Spectral and Energy Efficiency: Analog systems have a spectral
efficiency of ~0.1 bps/Hz and high energy use per bit (> 100 µJ/bit).
 Poor Interference Handling: Analog lacks error correction and directional
control.

Digital Modulation Techniques and Radiation Characteristics

Techniques:
 Binary schemes: ASK, FSK, PSK
 Higher-order schemes: QAM (used in 3G, 4G, 5G)
  OFDM: Used in LTE, Wi-Fi, 5G
 MIMO and Beamforming: Used in 4G/5G to enhance signal
directionality
Radiation Characteristics:
 Bursty Emission: Radiation occurs only when data is sent.
 Lower Average Power: 4G/5G handsets operate at 0.2 – 1.25 W.
 Adaptive Radiation: Power is adjusted dynamically, reducing average
exposure.
 Directional Transmission: Beamforming reduces ambient exposure by up
to 50%.
 Spectral Efficiency: Ranges from 4–30 bps/Hz, depending on the
modulation type and technology.
 Energy Efficiency: Digital systems often consume < 10 µJ/bit.

5. Comparison Table: Radiation in Analog vs. Digital Modulation

Aspect Analog Modulation Digital Modulation
Bursty (ON only during
Carrier Signal Always ON
transmission)
Power Output 0.6–2 W 0.2–1.25 W (adaptive)
(Mobile)
Base Station Up to 100 kW
10–40 W (cell towers)
Radiation (broadcast)
Often near safety
SAR (for users) Typically < 1.0 W/kg
limits
Radiation
Omnidirectional Directional (via beamforming)
Directionality
Spectral Efficiency ~0.1 bps/Hz 4–30 bps/Hz
Energy per Bit >100 µJ/bit ~1–10 µJ/bit
Bandwidth Use 100–200 kHz (FM) 20 MHz (LTE), more efficient
Interference Weak Strong (error correction +
Aspect Analog Modulation Digital Modulation
Handling adaptive coding)
High (encryption + power
Security & Control None
control)

Case Studies: Radiation Comparison with Real-World Examples

Case 1: FM Radio (Analog Modulation)
 Modulation Type: Frequency Modulation (FM)
 Carrier Frequency: ~100 MHz
 Bandwidth per Channel: 200 kHz
 Transmitter Power:
o City FM Station: 5–10 kW
o Large broadcast towers: Up to 100 kW ERP
 Radiation Characteristics:
o Radiates continuously, even in silence
o Omnidirectional antennas radiate in all directions
o Public exclusion zones often enforced near towers
o Spectral Efficiency: ~0.1 bps/Hz
o High interference susceptibility and energy use
o No user power control or encryption

Case 2: 4G LTE Network (Digital Modulation)

 Modulation Type: OFDM with 64-QAM
 Carrier Frequency: 1800 MHz
 Bandwidth per Channel: 20 MHz
 Transmitter Power:
o Handset: 0.2–1.25 W (adaptive)
o Base station: 10–40 W per sector
  Radiation Characteristics:
o Uses dynamic power control, reducing SAR
o Beamforming focuses radiation only where needed
o Idle devices do not transmit
o Spectral Efficiency: ~6 bps/Hz
o Energy per bit: ~5–10 µJ/bit
o Complies with SAR standards: typically <1.0 W/kg

Case 3: 5G mmWave (Digital Modulation - Future Focused)

 Modulation Type: OFDM with 256-QAM
 Carrier Frequency: 26 GHz (mmWave band)
 Bandwidth per Channel: Up to 400 MHz
 Transmitter Power:
o Small cells: 1–5 W
o Handsets: ~0.5 W, highly directional
 Radiation Characteristics:
o Highly directional via massive MIMO
o Lowest exposure per bit of any generation
o Spectral Efficiency: > 20 bps/Hz
o Energy per bit: < 1 µJ/bit

Conclusion
The comparison between analog and digital modulation techniques clearly
shows that digital systems are vastly superior in terms of radiation efficiency,
safety, and signal management.
Analog systems like FM and AM, while foundational in communication history,
are inefficient, high in continuous radiation, and lack power control. Modern
digital systems—from 2G to 5G—have progressively reduced transmitter
power, improved spectral efficiency, and introduced targeted radiation via
beamforming.
As we transition to future 6G networks, we expect radiation to become even
more optimized through AI-driven power control, intelligent surfaces, and ultra-
low latency communication — ensuring both technological advancement and
public health safety.

References
1. Haykin, S. (2001). Communication Systems. Wiley.
2. Rappaport, T. S. (2014). Wireless Communications: Principles and
Practice. Pearson.
3. FCC (2023). Radio Frequency Safety. https://www.fcc.gov/general/radio-
frequency-safety-0
4. ICNIRP (2020). Guidelines for Limiting Exposure to Electromagnetic
Fields (100 kHz to 300 GHz).
5. Proakis, J. & Salehi, M. (2008). Digital Communications. McGraw-Hill.
6. GSMA Intelligence (2024). The Mobile Economy Report.
7. ITU (2022). Radio Regulations & Spectrum Allocation.