Amelie Hagelauer

Industrial mmWave Radar Sensor in Embedded Wafer-Level BGA Packaging Technology

We present highly integrated 60-GHz radar transceivers for industrial sensor applications. The bistatic and monostatic transceivers are implemented in the SiGe bipolar technology and packaged using the embedded wafer-level ball grid array technology that allows for direct embedding of the antennas in the package redistribution layer. In this way, very compact and efficient radar frontends comprising all millimeterwave components can be implemented in an 8 × 8 mm2 package. These frontends were soldered on a standard low-cost printed circuit board based on FR4 material. For verification of the proposed frontends, an frequency-modulated continuous wave (FMCW) radar system was developed and set up within this paper. Theoretical considerations and simulations as well as corresponding measurements were carried out for the evaluation of the designed system. The demonstrator results of these embedded radar sensors show an excellent system performance at a high integration level.

Influence of dissipated power distribution on BAW Resonators' behavior

By taking the spatial distribution of the dissipated power into account the modeling of Bulk Acoustic Wave Resonators at higher power levels could be improved. The simulation results have been verified by measurements of vectorial scattering parameters during high power loads and by measurements of the temperature increase due to the self-heating by infrared thermography.

Polyharmonic Distortion modeling of RF BAW components

For the first time the Polyharmonic Distortion (PHD) model has been used to characterize the nonlinearities of Bulk Acoustic Wave (BAW) components. For that purpose a measurement setup has been developed by extending a nonlinear vector network analyzer with required external components enabling X-parameter measurements at high power levels. By discussion of selected components of the BAW resonators PHD model and performing simulations in an RF design environment the importance of PHD model for improved BAW filter design has been demonstrated.

Influence of temperature distribution on behavior, modeling, and reliability of BAW resonators

The influence of spatial inhomogeneous temperature distribution caused by dissipated power on BAW resonators behavior has been investigated for the first time. A novel modeling approach with an acceptable calculation time taking the temperature distribution into account has been developed allowing an improved modeling of BAW resonator behavior at high power levels. By applying the modeling approach it could be shown that the common way to use a measured TCF to determine the device temperature at high power levels is not generally valid and can lead to inaccuracies in life time predictions. The modeling approach has been verified by infrared temperature measurements of BAW resonators under high power loads.

Improved modeling of bulk acoustic wave resonators and filters

Duplexers and filters for mobile radio are one of the classic field of application for the BAW technology. In recent years the size of the devices has been reduced by about a half and the trend is still toward more compact designs with higher performance at the same time. This translates directly to very demanding requirements on the effective coupling coefficient and on the quality factors of the underlying BAW resonators. Measurements show that the size and the shape of the resonators have a significant influence on the overall performance. Hence, size-relevant effects need to be considered in 1D-simulation, which is the base for fast filter optimization. To evaluate the influence of the resonator size on the filter performance we analyzed several SMR-BAW resonator area and shape variations in combination with different overlap sizes in a series of experiments. Moreover, the influence of the overlap size on different resonator areas is studied with 2D-FEM simulations. In this paper we present the results of our resonator measurements. The results are basis for developing a modified 1D-model for designing BAW filters. Additionally, a new method for the extraction of an ‘equivalent acoustic impedance’ for the description of the acoustics is presented and compared to the modified 1D-model.

Measurement setup for X-Parameter characterization of bulk acoustic wave resonators

In this work a modern measurement method has been utilized in order to characterize nonlinear behavior of bulk acoustic wave (BAW) solidly mounted resonators (SMR). Unlike typical nonlinearity characterization methods, the method which was employed here not only records amplitudes, but also the phase of generated harmonics. Furthermore, the relations between the harmonics of different order are given. The modeling approach being used is the poly harmonic distortion (PHD) modeling approach, realized by the measurement of X-Parameters. For that purpose it was necessary to extend a nonlinear vector network analyzer (NVNA) by external components in order to enable high power measurements. Afterwards, several optimization steps were required to perform phase calibration. This difficulty arose due to the high power incident tones and steep resonator impedance curves on the one hand and the limited power provided by the phase calibration standard on the other hand.

A Method for Accurate Modeling of BAW Filters at High Power Levels

A novel approach for multiphysics modeling of bulk acoustic wave (BAW) filters is presented allowing accurate and at the same time efficient modeling of BAW filters at high power levels. The approach takes the different types of losses and their spatial distribution into account in order to provide the required input for thermal simulation. The temperature distribution determined by thermal simulation is used to modify the geometry and the layer stack of each single resonator of the filter. In this way, the required input for modeling of electromagnetic (EM) and acoustic behavior at high power level is generated. The high accuracy of the modeling approach is verified by the measurements of the S-parameters and the temperature distribution by infrared thermography during high-power loads. Moreover, the influence of the nonlinear behavior on the frequency shift of the resonance frequency is investigated. For this purpose, a parameterized nonlinear Mason model has been combined with a 3-D EM finite-element method and the required nonlinear material parameters were determined by fitting simulation results to the measured polyharmonic distortion model (X-parameters) of a BAW resonator.

Multiphysics Modeling of BAW Filters

A novel approach for multiphysics modeling of BAW filters is presented allowing accurate and at the same time efficient modeling of BAW filters at high power levels. The approach takes the different types of losses and their spatial distribution into account in order to provide the required input for thermal simulation. The temperature distribution determined by thermal simulation is used to modify the geometry and the layer stack of each single resonator of the filter. In this way the required input for modeling of electromagnetic and acoustic behavior at high power level is generated. Moreover, the influence of the nonlinear behavior on the frequency shift of the resonance frequency is investigated. The high accuracy of the modeling approach is verified by measurements of the S-parameters and the temperature distribution by infrared thermography during high power loads.

The impact of embedded wafer level BGA package on the antenna performance

In this article, we present a study about the impact of embedded wafer level ball grid array (eWLB) on characteristics of antenna. The antenna in package is a promising solution for integration of antennas and eWLB technology enables integration of passive components and antennas into the redistribution layer (RDL). The antenna radiates perpendicular to the package in broadside into the package. There are different parameters such as size, shape, and thickness of the eWLB package which affect the radiation pattern significantly. Moreover, the materials properties of package like relative permittivity (εr) and loss tangent (tanδ) impact the impedance bandwidth, gain and efficiency of antenna and have to be taken into account. The other important parameter to design the antenna in package is the distance of antenna to the reflector. We present the feasibility of an antenna with backside metallization as an integrated reflector in an 8 mm × 8 mm eWLB package. The measurement and simulation results show that eWLB is an attractive candidate for mm-wave applications.

Antenna array in eWLB for 61 GHz FMCW radar

In this article we present an antenna array concept in embedded wafer level ball grid array (eWLB) package for mm-wave applications. The eWLB package has a excellent performance for high frequency and the additional fan-out area around the silicon chip enables the realization of passives and antennas. Moreover, integration of the antenna in package increases the efficiency and reduces cost. For some applications a single antenna in package is unable to achieve the required gain and directivity. Combining several antenna elements as an array in a package can be a possible solution. A two elements differential dipole antenna array in an 8 mm × 8 mm eWLB package at IMS (Industrial, Medical and Scientific) band about 61 GHz is analyzed and successfully implemented. A 100 Ω differential feeding system is designed for the array. The measured reflection coefficient is -25 dB and the designed antenna array has a gain of 11 dB and radiates in broadside.