PSPL 100GHz Sampler Module with 1.0mm Connectors

As outlined in US Patent No 6,900,710, the GaAs sampler die penetrates a coaxial 1-mm airline cavity. The center conductor of the coaxial airline contacts the GaAs sampler die through a gold bump formed on the sampler die. This creates a "through" sampler, in which the coaxial signal line is passed through the sampler to be re-used or terminated externally. This feature was also exploited in a prototype 100 GHz sampler module specifically designed to ride atop 1mm wafer probes to facilitate on-wafer measurements.

Measured Falltime of 100GHz PSPL Sampler

A typical fall time measurement of one of the PSPL 100GHz samplers is illustrated in the plot shown above. The time difference between the 90% and 10% points is 4.3ps (assumes a 10% overshoot in the measured signal). This fall-time measurement includes the effects of the stimulus, the sampler and the total system jitter. Estimating an equal contribution to the fall time from the stimulus and sampler, and assuming that the jitter contribution of is negligible, a fall time of 3ps is estimated for the sampler.

Higher Sampling Rates
The sampling rate of an equivalent time sampler traditionally must be traded off against the noise introduced by IF charge amplifier bandwidth. In Picosecond’s design of the LeCroy sampling modules, the maximum sampling rate was set at 10MHz, more than 20 times greater than competing products. This required drastic changes to the architecture of the IF charge amp that use a "pulse resolved IF" technique, where, instead of integrating the charge of the sample in a low bandwidth high impedance op-amp, the IF sample pulse is amplified in a bandpass transimpedance amplifier and re-sampled at the peak of the amplified pulse. This peak sampling architecture eliminates the traditional tradeoff between bandwidth and noise since the signal-to-noise ratio improves with increasing the bandwidth of the IF chain.

This architecture has allowed PSPL to raise the sampling rate to several Gs/sec, enabling "real-time" sampling of microwave signals without increasing the input referred noise. Higher sampling rates are of great interest in both real-time and equivalent time sampling applications such as ATE since they decrease measurement time and raise throughput. This is especially important for the case of measuring eye diagrams.

Better Linearity and Dynamic Range
Since the NLTL provides very energetic sampling strobes, they allow a large input signal range while maintaining excellent linearity.