Equivalent-time Oscilloscope Research Articles

A 0.2–7.1-Gb/s Low-Jitter Full-Rate Reference-Less CDR for Communication Signal Analyzers

For the measurement of high-speed communication signals, whether it is to check the signal’s bit error rate with a bit error rate tester or to record the signal’s eye diagram with an equivalent-time oscilloscope, a clock and data recovery (CDR) circuit is required to generate a trigger signal properly aligned to the input data signal. For the system under test where multiple communication protocols coexist, a wide operation frequency range and low jitter CDR circuit can undoubtedly improve the measurement efficiency and reduce the cost. However, obtaining broad frequency coverage and minimal recovery clock jitter simultaneously has always been a challenge in the design of CDR circuits. This paper proposes a CDR circuit combining a multi-band LC-VCO and a configurable frequency divider, which effectively expands the operating frequency range of the CDR while maintaining the low jitter of the recovered clock. A 0.2-7.1-Gb/s CDR circuits with a 1.9-ps RMS jitter of the recovered clock under a 7.1-Gb/s input PRBS signal is implemented in 65 nm CMOS. Compared with other LC-VCO based CDRs, the proposed CDR achieves better energy efficiency and lower jitter performance.

An Adaptive Bitrate Clock and Data Recovery Circuit for Communication Signal Analyzers

Many measurement instruments require an external timing reference to perform an accurate measurement. In equivalent-time oscilloscopes, for example, a trigger signal properly aligned to the data is essential, since they base their operation on a very accurate delay of the trigger, which is obtained by a clock and data recovery (CDR) circuit. In this paper, an adaptive bitrate CDR circuit for instrumentation applications is presented. It is designed in a standard 0.18- $\mu \text{m}$ CMOS technology with a single supply voltage of 1.8 V and operates from 312.5 Mb/s to 2.5 Gb/s with a maximum power consumption of 140 mW and occupies an area of 1.5 mm $\times $ 0.6 mm.

New Multilevel Bang-Bang Phase Detector

Equivalent time oscilloscopes are widely used as an alternative to real-time oscilloscopes when high timing resolution is needed. For their correct operation, they need the trigger signal to be accurately aligned to the incoming data, which is achieved by the use of a clock and data recovery circuit (CDR). In this paper, a new multilevel bang-bang phase detector (BBPD) for CDRs is presented; the proposed phase detection scheme disregards samples taken close to the data transitions for the calculation of the phase difference between the inputs, thus eliminating metastability, one of the main issues hindering the performance of BBPDs.

Enhanced on-wafer time-domain waveform measurement through removal of interconnect dispersion and measurement instrument jitter

We have measured the output waveshape and rise time of two high-speed digital circuits on a wafer using a 50-GHz prototype of a new instrument. The instrument uses vector error correction to de-embed the component under test like a network analyzer, but reads out in the time domain after the fashion of an equivalent-time oscilloscope. With the calibration plane of the instrument set at the tips of the wafer probes, errors arising from dispersion in the connection hardware are removed. We show that the random jitter in the measurement system is removed without the convolution penalty usually incurred by averaging so that anomalies such as pattern-dependent jitter are exposed. The system rise time is 7 ps, compared to a system rise time of 12-13 ps for a conventional equivalent-time oscilloscope of the same bandwidth in the presence of wafer probes, bias networks, and cables.

Comparison of time base nonlinearity measurement techniques

Distortions in the time bases of equivalent-time oscilloscopes and digitizers cause distortions of waveforms sampled by them. This paper reports on a comparison of two methods of characterizing time base distortion, using pure sine-wave inputs of known frequency: the "sinefit" and the "analytic signal" methods. Simulations are used to compare the performance of the two methods versus different types of time base distortion, different sine-wave frequencies, number of different sine-wave phases, levels of random noise, and levels of random jitter. The performance of the two methods varies considerably, dependent upon the input signal frequency and type of time base distortion. Each method does much better than the other for certain cases.