[Paper Review] Processing of Communication Signal Using Operational Transconductance Amplifier

Arabinda Roy, Kasturi Ghosh+2 more|arXiv (Cornell University)|Feb 25, 2010

Analog and Mixed-Signal Circuit Design6 references3 citations

TL;DR

This paper proposes a signal processing methodology for communication systems using operational transconductance amplifiers (OTAs), demonstrating implementations of a delta modulator and a compander circuit for pulse code modulation and data compression. The circuits, operating at 3.5V, were validated via SPICE simulation, showing effective analog-to-digital conversion and dynamic range compression in digital communication systems.

ABSTRACT

This paper proposes a signal processing methodology of communication system and realized that circuits using operational transconductance amplifier (OTA). Two important classes of communication circuit, delta modulator and compander have been designed using that procedure. In the first implementation coded pulse modulation system is demonstrated which employ sampling, quantizing and coding to convert analog waveforms to digital signals while the second gives data compression and expansion in digital communication system. The proposed compander circuit is realized with operational transconductance amplifier and diode. Required power supply to operate the circuit is 3.5V. Performance of the circuits realized with OTAs has been demonstrated through SPICE simulation.

Motivation & Objective

• To develop a low-voltage, low-power signal processing methodology for communication systems using operational transconductance amplifiers (OTAs).
• To design and implement a delta modulator for analog-to-digital conversion in pulse code modulation systems.
• To realize a compander circuit for dynamic range compression and expansion in digital communication systems.
• To validate circuit performance using SPICE simulation under a 3.5V power supply.
• To demonstrate the feasibility of OTA-based analog signal processing for efficient communication system design.

Proposed method

• The delta modulator was implemented using an OTA and a feedback loop to encode analog input into a 1-bit digital stream based on incremental changes.
• The compander circuit was realized using an OTA and a diode to provide logarithmic compression of input signal amplitude.
• A 3.5V power supply was used to operate both circuits, ensuring low-voltage operation suitable for portable communication devices.
• The signal processing chain included sampling, quantization, and coding for the delta modulator, while the compander handled signal compression and expansion.
• SPICE simulation was employed to evaluate the performance of both circuits under standard operating conditions.
• The OTA-based design enabled high transconductance gain and improved linearity for accurate signal representation.

Experimental results

Research questions

• RQ1 Can OTA-based circuits effectively implement delta modulation for analog-to-digital conversion in communication systems?
• RQ2 How well does an OTA and diode-based compander circuit perform in compressing and expanding dynamic range?
• RQ3 What is the performance of OTA-based signal processing circuits at a low 3.5V supply voltage?
• RQ4 To what extent can SPICE simulation validate the functionality and stability of OTA-based communication circuits?
• RQ5 Can OTA-based designs achieve sufficient linearity and accuracy for practical digital communication applications?

Key findings

• The delta modulator successfully converted analog waveforms into a 1-bit digital stream using incremental encoding, suitable for bandwidth-efficient transmission.
• The compander circuit achieved effective dynamic range compression using the OTA and diode, enabling efficient data compression in digital systems.
• Both circuits operated reliably at a 3.5V power supply, demonstrating low-voltage compatibility for portable communication devices.
• SPICE simulation confirmed stable operation and accurate signal processing for both the delta modulator and compander circuits.
• The OTA-based design provided sufficient transconductance and linearity for practical implementation in communication signal processing.
• The results support the feasibility of using OTAs as core building blocks for low-power, high-efficiency communication signal processing circuits.