Is Your Testbench Mixed-Signal Ready?

Figure 1: A representative block diagram of
a mixed-signal embedded system

Mixed-signal design is ubiquitous these days, with hybrids of digital and analog circuitry turning up everywhere. A typical mixed-signal designer may be a hardware or software engineer with specific needs. They may be working with 4-bit, 8-bit, 16-bit, and 32-bit microcontrollers in a single embedded controller or across several embedded systems. They need to capture a host of different signal types and serial-data protocols and understand timing relationships between them. Then there's all the different sensor signals, power-supply signals, and PWM control signals to guarantee embedded system performance and reliability.

Applying Multi-Stage, Multi-Rate Digital Filtering

Figure 1: The input signal shows both the desired 63-kHz signal
along with a 60-Hz component. Zoom trace Z1 shows the
60-Hz component in detail.

A while back, we posted some basics on how to apply digital filters to sort out signals with undesirable elements riding on top of them, i.e. a square wave that's being corrupted by a sinusoidal signal creeping in from somewhere in your system design. Now, let's look at how to extend the range of cutoff frequencies for digital filters, allowing them to be used even more effectively.

Understanding Probe Calibration Methods (Part II)

Figure 1: Experimental setup for comparing a
source-referred signal to an unloaded signal

As many engineers and techs know, there's ample room for confusion when it comes to a proper understanding of oscilloscope probe loading. In an earlier post, we covered probe calibration methods and tried to sort out terms such as calibration, correction, compensation, and de-embedding.