Module expands channel count for PDM measurement

5th November 2019

Mick Elliott

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Audio Precision has the PDM 16 module for the APx500 Series audio analysers. The new module offers simultaneous acquisition and measurement of up to 16 channels of PDM signals, making it the highest channel-count solution available for MEMS microphone and MEMS mic array testing.

PDM 16 is an optional interface module for the APx555, APx52x Series or APx58x Series audio analysers. Comprised of the input module installed in the analyser, a remote interface pod and an extension cable, the module provides sample-accurate inter-channel phase information, critical data for the creation of MEMS mic arrays.

Developers of systems using beamforming microphone arrays and other DSP-based multichannel audio acquisition applications depend on a true representation of phase alignment of the input channels to validate their algorithms and designs.

The module utilises synchronous sampling based on a common clock, thereby assuring a clear picture of the phase relationship between channels.

With its acoustically-silent remote pod and extension cable preserving PDM signal integrity for up to 10 meters, the module readily supports microphone measurements in anechoic chambers.

As an added feature, the module can provide up to 50mA Vdd power supply to the device, or devices, under test.

MEMS (micro-electromechanical system) microphones are extremely small microphones that are used in a wide range of applications and, most commonly, use a PDM (pulse density modulation) stream as their digital output. MEMS mics, either individually or in an array, are integral components in smartphones, hearing aids, mobile computing, automotive systems, smart speakers and other IOT systems.

As an APx module, PDM 16 is part of an integrated audio test solution, leveraging the combined power and flexibility of the APx500 audio measurement software and market-leading test hardware for signal generation and acquisition.

Along with PDM 16, APx500 Series analysers can include modules for testing components or systems that also use interfaces ranging from analogue to chip-level I²S and TDM protocols, Bluetooth or HDMI.

A PDM 16-equipped analyser can even be equipped with the existing APx PDM module to add two channels of PDM output, as well as power supply rejection (PSR) and jitter measurements.