Active Harmonic Load–Pull for On-Wafer Out-of-Band Device Linearity Optimization

Abstract

In this paper, we present an active harmonic load-pull system especially developed for the on-wafer linearity characterization/optimization of active devices with wideband modulated signals using the out-of-band linearization technique. Our setup provides independent control of the impedances at the baseband, fundamental, and second-harmonic frequencies presented to the input and output of the device under test. Furthermore, to enable realistic test conditions with wideband-modulated signals, the electrical delays in the load-pull system are kept as small as possible by implementing a novel loop architecture with in-phase quadrature modulators. We have achieved a phase variation of the reflection coefficient of only 5 MHz for both the fundamental and second-harmonic frequencies.We demonstrate the high potential of the system for the on-wafer evaluation of new technology generations by applying out-of-band linearization to heterojunction bipolar transistor (HBT) and laterally diffused metal-oxide-semiconductor (LDMOS) devices. For the HBT, we outline a game plan to obtain the optimum efficiency-linearity tradeoff. Finally, a record-high efficiency-linearity tradeoff was achieved (without digital predistortion) for an inverse class-AB operated Philips Gen 6 LDMOS device, yielding 44% efficiency at an adjacent channel power level of 45 dBc at 2.14 GHz for an IS-95 signal.

Improved RF Devices for Future Adaptive Wireless Systems Using Two-Sided Contacting and AlN Cooling

“…10. It is noteworthy that the level of the devices below a tonespacing of 30 MHz basically cannot be measured since it requires an even higher dynamic range than offered by the dedicated test bench [32]. Conservatively speaking, the measured is larger than 67 dBm up to 10 MHz bandwidth, which is GHz) linearity as function of output power [21].…”

Enhanced RF power amplifiers and device characterization setups using coherent mixed-signal techniques

“…Note that this kind of functionality is simply not present or not possible in mechanical tuner systems , or active closed-loop load-pull systems . Consequently, with such an approach, realistic in-band reflection coefficients versus frequency at baseband, fundamental and harmonics can be offered to the active device under test, a feature that is very important when optimizing device performance for linearity [17]. The basic operation principle of mixed-signal based device characterization is explained in Fig.…”

“…10). In these experiments the importance of eliminating the electrical delay in the measurement setup was demonstrated by first applying a comparable delay as currently is present in state-of-the-art load-pull setups [17] and then perform the same measurement when the electrical delay in the setup is canceled. As one can see from Fig.…”

Enabling Low-Distortion Varactors for Adaptive Transmitters

“…12 was performed using a two-tone signal ( GHz) with varying tone spacing. For the calibrated power measurements, we have used the system of [22]. Fig.…”