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Active-Load-Pull Measurement System Fully Characterizes PAs

Often, designers of power amplifiers (PAs) and other active devices do not define performance outside of the fundamental frequency that's being used. In addition, they seldom provide any information about optimum harmonic source and load impedances. With the Mesuro active-load-pull measurement systems, however, applications in development can be tested over wider harmonics to arrive at reference designs with better impedance-matching efficiencies. In addition, on-wafer measurements enable the device manufacturer to efficiently characterize RF power devices before sorting and packing begins.

The Mesuro active-load-pull product, which is called the MB series, lets device and PA manufacturers fully characterize their devices within an accelerated amplifier design cycle. The MB 20 tests devices and power amplifiers to 20 W continuous wave (W) while the MB 150 extends the power level to 150 W CW. Both products are capable of measuring RF waveforms, power spectrum, S-parameters, and direct-current current-voltage (DCIV) data by utilizing a new measurement architecture that offers unconditional stability with no wideband artifacts. The system utilizes a Tektronix sampling scope to enable simultaneous wideband measurements with a coherent alignment of all spectral components including the fundamental and multiple higher-order harmonics. It also measures the DC and baseband response, which are essential in capturing often-seen memory effects in devices.

The secret sauce in the MB series is the firm's "waveform engineering," which was pioneered at Cardiff University. It enables the replication of S-parameter concepts within the nonlinear domain. By simultaneously measuring the actual current and voltage at the device, this technology allows designers to view and engineer their waveforms to match theory. The new open-loop, active-load-pull technique replaces passive tuners with an RF source that adjusts the amplitude, phase, and power level to vary the effective impedance at the device-under-test (DUT) interfaces. The waveform engineering system allows absolute control of all in-band and out-of-band impedances. As a result, the designer can control the harmonic source/load impedance over the entire Smith chart. A comprehensive software user interface facilitates measurement automation and an intuitive introduction of waveform engineering.

Mesuro Ltd., 8th Floor, Eastgate House, 3543 Newport Rd., Cardiff UK, CF24 0AB; +44 (0)7730 289 459, FAX: +44 (0) 2920 491 275, Internet:

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