DSP
Uploaded June 29th, 2022 by Yashique Chalil
Signal Processing Labs
VHF Communication
This project outlined the implementation of VHF communication for avionics using Analog Devices’ RF transceivers, focusing on the ADRV9361-ZC7035 system-on-module (SOM) and associated hardware. The ADRV9361-ZC7035, equipped with an AD9361 RF Agile Transceiver and a Xilinx Zynq SoC, is designed for low-power, rugged applications and is compatible with tools like GNU Radio and MATLAB Simulins for Software Defined Radio (SDR) development.
Key components include:
ADRV9361-ZC7035:
A robust, industrial-grade SOM that supports RF data streaming and Zynq targeting, conforming to military standards.
ADRV1CRR-FMC:
A carrier board for SDR SOMs, housing an ADAU1761 codec to convert digital signals from the ADRV9361 into analog audio outputs.
ADALM-PLUTO:
A portable, cost-effective RF learning module based on the AD9363 transceiver and Zynq FPGA, used for experimentation and signal transmission. The project demonstrated VHF communication through a test setup where audio signals are transmitted using ADALM-PLUTO and received and played back by the ADRV9361, showcasing the system’s ability to handle real-time audio transmission in avionics communication scenarios.
Audio Wearables Testing
This project involves testing and evaluating audio wearables, to ensure premium sound quality. The challenge was to conduct these tests outside of traditional acoustically controlled environments, which are often inaccessible in modern mobile workstations and home office setups.
Key Points:
Need for Isolation: Accurate audio testing requires isolating the sound from external noise, which can affect test results. In open environments, ambient noise leads to inconsistent results.
Acoustic Chamber:
To address these challenges, an acoustic chamber was built using layers of acoustic plywood, mineral wool, and pyramid foam. The chamber effectively reduces external noise and ensures a controlled testing environment. Tests show that the chamber effectively brings the noise floor to around -95dB, making it suitable for accurate audio measurements.
The mic is placed outside the box and exposed to minimal ambient noise. (Fan noise, Slight traffic and small background conversations).
Here an average of -85dB is observed.
When the mic is enclosed in the chamber almost all the ambient noise is cancelled showing an average of only -95dB of noise remaining.
Testing Setup:
Speaker Recording:
The audio device under test (headphones/earphones) is paired with a mobile device playing a specially designed 20-minute audio vector. The output from the device’s speakers is recorded using a MiniDSP EARS setup inside the chamber. These recordings are analyzed in MATLAB for various parameters.
Microphone Recording:
The microphone quality is tested by pairing the device with a PC via Bluetooth, using a mono speaker to play the test signals. The setup is similar to the speaker test, with recordings analyzed for performance metrics.
Tests Conducted:
Objective Tests:
Frequency Response
Dynamic Range
Chirp Spectral Purity
Tone
PEAQ test
Mic Directionality
Mic Noise Reduction Test
Total Harmonic Distortion
Test Delay
Subjective Tests:
Speaker Bass listening
Speaker Audio Quality Listening
Mic Call Quality
Latency
This project provides a robust framework for testing audio wearables in a controlled environment, ensuring reliable and accurate results despite the challenges of non-traditional testing spaces.
