The Fundamentals of Coherent Signals

Figure 1: These two coherent light waves have
a constant phase offset

Optical communications have come a long way from the simple direct detection of amplitude-modulated transmissions. Today's long-haul optical networks make use of coherent detection, and for good reason. Using coherent detection, receivers can track the phase of the incoming signal and thereby extract any information conveyed using phase and/or frequency modulation. Thus, coherent detection facilitates much higher capacity without using more bandwidth.

USB Type-C Cable Detection

Figure 1: The four possible states of
connection for a USB Type-C cable

Having examined some of the basics regarding the USB Type-C connector and the Power Delivery 2.0 specification that complements the Type-C spec itself, we'll turn our attention to the topic of cable detection. The Type-C connector is reversible, which is to say there are four ways a cable can be connected between upstream- and downstream-facing ports (Figure 1). Not only that, but there are different types of Type-C cables. So how do the devices discern what's between them?

A Look at USB Type-C and Power Delivery

Figure 1: The USB Type-C
connector alongside its
Micro-B counterpart

With USB 3.1, the latest iteration of the serial-data protocol, comes a new smaller and universal connector: USB Type-C, the USB-IF's answer to Apple's Lightning connector (Figure 1). Even Apple itself has adopted USB Type-C for its latest MacBooks, a rare show of support from Cupertino for an open standard. Like Lightning, USB Type-C is reversible, but it offers other interesting features, such as the ability to handle other protocols using "alternate modes." It also incorporates the new USB Power Delivery specification for improved power-supply capabilities over USB.

Using Your Oscilloscope's X-Y Display

Figure 1: Shown are some common
Lissajous patterns in an X-Y display

If you're fortunate enough to own an oscilloscope with X-Y display capabilities, you have a valuable tool at your disposal. From classic Lissajous patterns to state transition diagrams for today's quadrature communication systems, X-Y plots give us a window of the functional relationships between two waveforms.

Follow The Bouncing Signal

Figure 1: Trend plotting is a handy tool
for discerning frequency-hopping
patterns

Signal jamming, noise generation/interference, signal interception, and other malicious RF-related activities have long been part and parcel of the electronic warfare arena. One countermeasure that is widely deployed is frequency hopping spread-spectrum (FHSS) transmission, or rapid and pseudo-random jumps of the carrier frequency in an effort to confound would-be jammers. FHSS transmission poses test and measurement challenges that we'll outline below.

Analyzing RADAR Signals with Demodulation

Figure 1: An example of a radar
signal with 1-GHz RF carrier

In the electronic warfare milieu, one of the most common RF applications is that of radar systems. Radar, which uses RF energy to determine the range, angle, and/or velocity of objects, can be used for detection of aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain, among other things. An oscilloscope's demodulation math function is very helpful in analysis of radar signals, so let's look at a couple of examples of how to approach such measurements.

Video: The Many Varieties of Oscilloscope Probes

Got a minute (OK, a minute and a half)? Take a look at this quick tutorial video that takes you through the four basic types of probes and what they're used for:

If this little thumbnail sketch whetted your appetite for more info on oscilloscope probes, we've got you covered with a series of popular blog posts on the topic:

The Realities of Oscilloscope Probes

Back to Basics: Probes (Part I)

Back to Basics: Probes (Part II)

Back to Basics: Probes (Part III)

Back to Basics: Probes (Part IV)

Understanding Probe Calibration Methods

Understanding Probe Calibration Methods (Part II)

The Effects of Passive Probe Ground Leads