Transistor and Other Nonlinear Device Measurement R&D Topics

NIST CTL’s transistor and other nonlinear device measurement R&D work, led by the High Speed Electronics Project is dedicated to characterizing transistors and communications circuits operating at extreme speeds and in highly powered, highly nonlinear states. We focus our efforts in three areas.

1) On-wafer small-signal measurements to 1 terahertz
The transistors behind next-generation 5G wireless systems will be capable of operating at hundreds of gigahertz and beyond. To build reliable wireless systems capable of exploiting the high-frequency spectrum bands, we must first understand the behavior of the transistors generating the signals.

Small-signal behavior is of interest in this work because we can make these measurements at frequencies as high as a terahertz. We use NIST-calibrated commercial vector network analyzers, and on-wafer probes, because doing so is the only way to test signal-generating transistors on dense integrated circuits.

2) Development of transistor models with associated uncertainties
Theoretical models do not yet predict the performance of millimeter-wave circuits, and existing test instruments such as vector network analyzers (VNAs) can’t measure nonlinear devices at these frequencies. VNAs excite and measure at just one frequency; nonlinear devices generate additional frequency components such as second and third harmonics. VNAs also fail to measure the absolute magnitude and phase of the waves incident on and reflected from the device being tested. All these factors are vital to understanding the distortion arising from millimeter-wave nonlinear devices.

This work focuses on lower-frequency, higher-power transistors, starting at microwave frequencies and extending into the millimeter-wavelengths. Understanding their nonlinear behavior will be indispensable to ensuring a combination of signal quality and battery life for mobile devices operating in millimeter-wave spectrum. As with on-wafer small-signal measurements, our work here will provide the metrological basis for the technologies upon which the next-generation 5G wireless vision depends.

3) LSNA development for high-power devices operating up to 300 GHz
In addition to CTL’s theoretical and modeling work with high-speed nonlinear devices, CTL is developing a large-signal network analyzer (LSNA) with 200 GHz to 300 GHz of measurement bandwidth, capable of capturing the magnitude and relative phase of harmonics of devices operating at millimeter-wave frequencies. The process is unfolding in three phases:

• Prototype development of an LSNA system assembly using electo-optic sampling that captures harmonics at more than 100 GHz.
• Circuit design for and testing of an InP HBT transistor capable of testing fundamental nonlinear signals and harmonics up to 270 GHz.
• The application of CTL’s mmWave LSNA to industrial problems and the dissemination of instrument design to industry.