An approach to accurate measurements of the electrical characteristics of SAW RF filters using neutral test environments

Abstract

-The paper discusses and classifies typical measurement setups used for the precise electrical characterization of surface acoustic wave (SAW) radio frequency (RF) components, such as, e.g., SAW filters and duplexers, in the context of nowadays demand for increased accuracy of measured filter data. The measurement setups are divided into test environments and application environments. By means of a couple of case studies the paper exemplifies the impact of printed circuit boards (PCBs) on the measured electrical filter characteristics. The effects observed are investigated by measurements and simulation. Simulation models established and analyzed take both relevant electromagnetic and acoustic effects into account. Comparisons of measurements and simulations indicate excellent agreement. The paper points out the necessity for measurement setups that provide a neutral environment to the filter. Here, the notion neutral environment implies minimal reflections, minimal feed-through or cross-talk, and minimal losses. It concludes with the proposal of a neutral environment, which has been successfully implemented in a couple of use cases. Performing the measurement using a neutral environment allows the determination of the filter characteristics without effects caused by the PCB, which is considered an essential prerequisite for an engineering approach to a modular design of a complex system, such as, e.g., the RF section of a mobile terminal.

Characterization of SAW Duplexer Inserts for LTCC RF Front-End Modules by Simulation and Measurement

“…Its reference planes are typically set on the borders of the package. Thus, it can be usually characterized soldered on a neutral test PCB by measurement or modeled in an appropriate electromagnetic simulator on an ideal PCB by simulation [2].…”

“…The layout of test PCBs can influence the performance of the DUT, especially of SAW filters [2]. In order to determine the performance of the SAW duplexer insert, we followed the proposal for the design of neutral test PCBs in order to minimize the losses, reflections, and crosstalk [2], [3].…”

“…In order to determine the performance of the SAW duplexer insert, we followed the proposal for the design of neutral test PCBs in order to minimize the losses, reflections, and crosstalk [2], [3]. The main facts of the test PCBs are listed in Table I.…”

A New Modular Design for Test and Application PCBs of SAW RF Filters to Ensure Precisely Predictable Filter Characteristics

“…Otherwise, an additional microstrip line with high characteristic impedance will be formed unintentionally by cutting away the original ground plane of the microstrip Another important point during optimization is the provision for an undisturbed current path. Hereto, a sufficient number of vias has to be positioned in the ground structures on top of the PCB in the vicinity of the microstrip lines, as shown in [3].…”

“…Taking into account all relevant effects related to the package and measurement environment in the simulation models is tedious. Up to now, it is still a problem that the measurement environment, in particular, the printed circuit board (PCB) on which the component is soldered for operation, can significantly influence the measured electrical characteristics [3]. All its relevant effects and influences have to be implemented or sufficiently taken into account in the simulation for the filter design.…”