All active devices exhibit nonlinear behaviour to some degree. In general, the higher the operation frequencies, the higher the degree of nonlinear behaviour. The rapidly developing semiconductor chip manufacturing industry has brought RFIC designs into a much higher frequency level over the past decade. This makes large-signal nonlinear behavior modeling and measurements more critical. Unfortunately, making nonlinear measurements is not an easy task. Most currently available tools and models for accomplishing this goal are generally difficult to use and do not provide all the information required. Most importantly, large-signal nonlinear calibration is too complicated to be accomplished, resulting in an inability to accurately measure the nonlinear effects of active RF devices.

A few years ago, Root and Wood at Agilent Technologies Inc. developed the

Simplified configuration of an NVNA and ADS workbench for nonlinearity measurements.

In this paper, Section

Scattering wave transmission.

Two important techniques used in

Phase-normalized quantities are used to simplify the mathematics.

In general, the superposition principle and linear relationships are inapplicable to large-signal nonlinear systems. However, in many practical cases there is only one dominant large-signal input component (

Considering only

The NLTLs discussed here consist of coplanar waveguide (CPW) transmission lines interleaved with NMOS varactors (see Figure

Circuit diagram of the NLTL configuration.

An NLTL has three fundamental and significant characteristics: nonlinearity, dispersion, and dissipation. These define the NLTL’s functions and behavior. Nonlinearity is due to the voltage-dependent varactor capacitance, dispersion to the periodicity of the NLTL, and dissipation to the finite conductivity of the CPW conductors and the series resistance

NLTLs can function as pulse-compression components [

Nonlinearity of the MOS varactors, together with the transmission line parameters, determines the nature of the nonlinear wave propagation along the NLTL. Varactors used in pulse-compression NLTLs require a large cutoff frequency

We realized NLTL pulse-compression circuits on a 1.5 × 2.0 m

Pulse-compression NLTL chip.

Measured NLTL time-domain waveforms for a 13.9 dBm input at 5 GHz.

Measured frequency-domain NLTL spectrum for a 13.9 dBm input at 5 GHz.

The nonlinearity measurements were done at the microwave laboratory of the Communications Research Centre (CRC), Ottawa, Canada. An N5242A-type NVNA was provided by Agilent Technologies on a “demonstrator” basis. The testing setup is shown in Figure

The

To validate the testing results, the simulation was done in ADS. Figure

The simulated NLTL result with a 5 GHz, 1.6 V-amplitude input.

Reconstructed waveform using only 5 lowest output harmonics.

We previously showed that silicon NLTLs can be used in pulse-compression circuitry [