Two important indicators of oscilloscopes: trigger technology and ENOB

At the end of the year and the beginning of the next year, following the launch of the WaveMaster8 Zi series oscilloscope by LeCroy, Tektronix announced the launch of the industry's fastest oscilloscope and probe system. Both parties emphasize that their products are the fastest oscilloscopes in the world, which makes us very confused and inevitably question the "fastest". Who is the "fastest"?
In fact, when selling products, we all understand a truth, that is, Wang Po sells melons and brags about himself. Maybe they use different measurement standards and different angles. Even if the product has the same function, from the sales side's sales perspective, it makes sense to say "fastest". As we all know, under normal circumstances, the measurement indicators of oscilloscopes are mainly bandwidth, sampling rate and storage depth. When selling and purchasing oscilloscopes, most people will consider these parameters. When Tektronix released the DPO/DSA70000B series oscilloscopes, in addition to the above high indicators, it also took the trigger function as the product's promotion focus, and also extracted the less familiar digital indicator of effective bit position (ENOB). Here, we will briefly look at two concepts that are critical but often overlooked in oscilloscope metrics - trigger technology and ENOB.
Highly innovative trigger system easily copes with 5Gb/s serial protocol design challenges
In a typical design cycle (as shown in the figure), a key to efficiently completing the entire design process is to minimize the time spent on debugging and diagnosis. Engineers who use oscilloscopes to process fast and complex serial data streams know that inspection and verification tasks require not only high enough bandwidth, but also complete trigger functions that can locate specific information combinations to speed up debugging and diagnosis. Recognizing this, Tektronix's latest DPO/DSA70000B series oscilloscopes, with 5Gb/s hardware-based real-time serial pattern trigger and serial protocol decoding software plus powerful advanced search and mark functions, push the Pinpoint trigger system to a higher level of performance.

It is reported that some high-speed serial analysis systems only provide software triggering for high-speed serial data streams. They acquire each waveform and search for the code pattern of interest. If it is not found, another waveform will be acquired, and the process will continue, and so on, until the required bit sequence is found. Therefore, the software trigger may take a very long time to find the code pattern of interest. In contrast, Tektronix hardware serial trigger can monitor data in real time to ensure that the acquisition is triggered when the specified code pattern appears for the first time, minimizing the debugging time.
ENOB, a crucial role in high-frequency low-margin measurement
As the data rate of computers, telecommunications and video equipment increases, engineers are likely to need to use a high-performance oscilloscope to complete their work and may need to observe signals or code streams of several GHz and several Gb/s. At these extreme speeds, the daily measurement indicators of oscilloscopes (such as resolution and accuracy) are still applicable, but as the design operating frequency increases, the effective bit position (ENOB) is playing a vital role and directly affecting the measurement results.
ENOB can be said to be a synonym for the original "effective bit". This is an extremely comprehensive indicator that covers a variety of errors that all digital oscilloscopes have to a certain extent, such as offset error, gain error, nonlinearity, noise, etc. ENOB is a practical metric that represents how these errors change as a function of frequency.
Most oscilloscopes are specified in their specifications for DC operation. Depending on the frequency at which the digital system is running, the actual number of bits the oscilloscope is operating at may be less than the number of bits reflected in its specifications. ENOB represents this dynamic performance metric. When making system measurements, the errors caused by the less significant bits are added to the errors inherent in the device under test. If the oscilloscope is compared to a scale, then a low ENOB is like putting a certain amount of weight on the scale before weighing. Today's fast digital designs with increasingly smaller operating margins are more susceptible to this added "weight". Therefore, it is critical to maintain the highest ENOB possible across the frequency range of the instrument.
As with any product, different criteria will lead to different conclusions. As for how consumers view it, it depends on their own usage preferences.