Final Design

Description of Final Design Solution

In order to best understand the final design solution of the MEMS test module, it is necessary to gain familiarity with the overall approach adopted in order to complete the design. The test sequence begins with the tester selecting the desired test signal. This signal (typically a sinusoid with a sweep of frequencies) has relatively low voltage amplitude, and must be amplified in order to drive the main acoustic stimulus. For the purposes of this project, the acoustic stimulus comes from a piezo speaker. An amplifier is used to boost up the signal voltage to a level which is capable of driving the speaker. The sound from the speaker is channeled through an orifice plate with multiple orifices, which deliver the sound directly to the MEMS microphones’ acoustic ports. Once the MEMS microphones detect the pressure waves from the speaker, the microphones create output voltages which can be captured by a data acquisition device (oscilloscope, PC DAQ board, etc.). The overall method of MEMS testing can be simplified to a single sequence of steps, illustrated below

Figure 1: This shows a flow schematic of the system behavior, and the signal route from start to finish during testing.

Figure 2: The image above is an exploded CAD model of the acoustic stimulus module. This shows specifically where each component lives with respect to the others. It also serves as an accurate portrayal of how the device is put together, with all the components present.

This image should help provide a visual understanding of the test module, and the locations of the components within it. Not shown in this image are the signal generator which provides the test signal, the amplifier required to boost the voltage of the test signal up to drive the speaker, and the data acquisition system used observe the MEMS output signals. Since this project scope only requires the design of the test module itself, the other test peripherals will be selected by the actual user.