Dr Jonas Urbonas

In this paper, through-plastic vector E-field measurements of an LDMOS transistor in an over-molded plastic package are presented. The measurement system uses a commercially-available electro-optic system connected to an NVNA with a comb generator to non-invasively measure the phase-coherent multi-harmonic E-fields. The device is measured in a load-pull measurement system, which is used to present optimal source and load impedances to the transistor during the multi-harmonic E-field measurements. All three E-field components are measured at the fundamental (2.2 GHz) and two harmonics at P1dB = 53.2 dBm.

In this paper, a new combined electro-optic and pulsed nonlinear vector network analyser-based load-pull measurement system for distributed multi-harmonic electric field measurements is presented. The system uses an external electrooptic probe to measure cross-frequency phase-coherent multiharmonic vector E-fields with an 8 µm spatial resolution and 20 MHz ? 20 GHz bandwidth. We demonstrate the performance of the distributed phase-coherent E-field measurements of Ex, Ey and Ez components with 3 harmonics above a commercially available large periphery, packaged, laterally diffused metaloxide-semiconductor (LDMOS) transistor. The transistor was measured at 2.2 GHz under pulsed conditions with 10 µs pulse and 10 % duty cycle, while outputting 55.1 dBm of power. The measured electric fields of the operating transistor are animated for the first time and reveal complex non-uniform operation at harmonic frequencies

We present for the first time a measurement system that is capable of directly detecting and identifying the physical location of an oscillation within RF and microwave power amplifiers. The method uses a combined external electrooptic, non-linear vector network analyzer, and vector load-pull measurement system, which allows the measurement of crossfrequency phase-coherent multi-harmonic vector electric fields above the transistor with an 8 ¼m spatial resolution and 20 MHz ? 40 GHz bandwidth. Raster scans above the amplifier allow the time-domain electric fields to be animated and superimposed on top of the amplifier image enabling immediate identification of any oscillations by direct inspection. The method is first demonstrated on a low power amplifier composed of two parallel 0.1-W pHEMT transistors that is intentionally designed to have an odd-mode oscillation. The applicability of the method is further demonstrated by measuring and animating in-package parametric odd-mode oscillations within a 260-W laterally diffused metal-oxide-semiconductor (LDMOS) transistor operating at 2.2 GHz under pulsed RF conditions with 10 ¼s pulses and 10% duty cycle. The measurement and identification technique is applicable to all semiconductor devices as the external electric field is non-invasively measured above the amplifier.

Fifth generation communication networks promise extremely high data throughputs, low latencies, and ultra-high reliability by employing small cells in high density networks. This will increase the use of highly ine?cient microwave power ampli?ers, that exhibit e?ciencies sometimes as low as 10% for advanced multi-carrier waveforms. To overcome these ine?ciencies and enable next generation technology development, the internal distributed behaviour of the packaged microwave power transistor has to be fully characterised, which is impossible using conventional port-based measurements. In this dissertation, the development of a set of multiphysics measurement techniques that capture the distributed electrical, electromagnetic, and thermal device behaviour is described. These new multiphysics measurement techniques enable the characterisation and direct visualisation of the ine?cient device performance, providing a basis for future design optimisation. The techniques combine a non-linear vector network analyser, electro-optic, load-pull and thermore?ectance measurement systems that enable large signal time-domain electrical, distributed multi-harmonic vector electric ?eld (E-?eld), and transient and steady-state thermal measurements. The multiphysics measurement set-up was used to characterise various transistors and PAs including 260 W silicon (Si) laterally di?used metal oxide semiconductor (LDMOS) ?eld e?ect transistors in both air-cavity ceramic and plastic packages, 25 W gallium nitride (GaN) on silicon carbide high electron mobility transistors (HEMTs), 250 W GaN HEMT and 360 W Si LDMOS Doherty power ampli?ers. The E-?eld measurements enabled the ?rst ever imaging of parametric odd-mode oscillations within multi-die packaged high-power microwave transistors. Additionally, the measurement system was used to verify the e?ectiveness of in-package oscillation suppression circuits. As high-resolution E-?eld measurements can be slow, a surrogate modelling-based measurement algorithm was implemented to accelerate measurements 10-fold. Transient thermal measurements helped to identify abnormal transistor ?nger-to-?nger heating in GaN HEMTs and revealed thermal di?erences along the gate width in GaN-based asymmetric transistors for Doherty power ampli?er applications.