Equivalent-time sampling is a well-known technique to capture repetitive signals at finer time intervals than a sampling clock cycle time and it is widely used to implement waveform measurement with high time resolution. There are three techniques for implementing its time base (i.e., sequential sampling, random sampling and coherent sampling), and they have their respective advantages and disadvantages. In this paper we propose a new coherent sampling system which incorporates a pretrigger and time jitter reduction function for a fluctuating input signal which a random sampling system has, while maintaining the waveform recording efficiency of a conventional coherent sampling system. We also report on a technique for measuring a reference trigger time period accurately which is necessary to implement the proposed sampling system, and show its effectiveness through numerical calculations of its data recording time.

This paper proposes a quasi-coherent equivalent-time sampling method to acquire repetitive wideband waveform signals with high throughput. We have already proposed a new sampling system which incorporates the pre-trigger ability and the time jitter reduction function for a fluctuated input signal while maintaining the waveform recording efficiency. The quasi-coherent sampling method proposed in this paper can be adopted to it in order to improve its data acquisition throughput significantly. Numerical simulation results show effectiveness of our proposed method.

A time-interleaved ADC system is an effective way to implement a high-sampling-rate ADC with relatively slow circuits. In the system, several channel ADCs operate at interleaved sampling times as if they were effectively a single ADC operating at a much higher sampling rate. Mismatches among channel ADCs degrade SNR and SFDR of the ADC system as a whole, and the effects of offset, gain and bandwidth mismatches as well as timing skew of the clocks distributed to the channels have been well investigated. This paper investigates the channel linearity mismatch effects in the time-interleaved ADC system, which are very important in practice but had not been investigated previously. We consider two cases: differential nonlinearity mismatch and integral nonlinearity mismatch cases. Our numerical simulation shows distinct features of such mismatch especially in frequency domain. The derived results can be useful for deriving calibration algorithms to compensate for the channel mismatch effects.

This paper presents an explicit analysis of the output error power in wideband sampling systems with finite aperture time in the presence of sampling jitter. Sampling jitter and finite aperture time affect the ability of wideband sampling systems to capture high-frequency signals with high precision. Sampling jitter skews data acquisition timing points, which causes large errors in high-frequency (large slew rate) signal acquisition. Finite sampling-window aperture works as a low pass filter, and hence it degrades the high-frequency performance of sampling systems. In this paper, we discuss these effects explicitly not only in the case that either sampling jitter or finite aperture time exists but also the case that they exist together, for any aperture window function (whose Fourier transform exists) and sampling jitter of Gaussian distribution. These would be useful for the designer of wideband sampling data acquisition systems to know how much sampling jitter and aperture time are tolerable for a specified SNR. Some experimental measurement results as well as simulation results are provided as validation of the analytical results.