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8-2018

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Fachzeitschrift für Hochfrequenz- und Mikrowellentechnik

RF & Wireless Evaluation

RF & Wireless Evaluation of Package Properties for RF BJTs Figure 1: SOT343 package with BFP640 transistor IC from Infineon Technology Figure 2: The SOT343 package partitions This application note demonstrates the extraction procedure for the passive part of a SPICE model for the package and wire bonds of an Infineon Technology SOT343 bipolar junction transistor (BJT) up to 10 GHz and compares the model against measurements. EDA simulation software streamlines the development of digital and analog circuits from definition of concept and estimation of required hardware and software characteristics to the design of system components like printed circuit boards (PCBs), chips, and packages. In particular, simulation technology for high-frequency (HF) and high-speed electronics enables designers to characterize parasitic effects at a wide range of frequencies and accurately predict performance. High-quality models are required and the better the model, the more likely that the functionality of the end product will correlate with simulated performance. system, the digital signal is presented with wide spectra and the model should be characterized at a wide frequency range. In an analog system, often the designer does not know what the working frequency of an analog component will be and must characterize it in a wide frequency range to cover all possible applications. It is also important to have correct DC modeling in order to have the correct biasing for nonlinear devices at the required frequency range if the device will need to go from the frequency domain to the time domain. Another model parameter is impedance range, as the signal shape will be different depending on the impedance of the load ports. In practice, this means the impedances on the integrated circuit (IC) pins that are used in the design, so the model should provide correct work in the required impedance range. National Instruments www.ni.com/awr What Level of Preciseness? A SPICE model is one possible schematic presentation, which is done using a text file. Components in the file show the modeled equivalent schematic of a device. A very important question in the creation of a model is at what level of preciseness should the model be extracted. Compared to digital, HF analog systems are less wideband, as the signal is very often concentrated close to the carrier frequency. In the case of a digital Figure 3: Three main parts of the pin 44 hf-praxis 8/2018

RF & Wireless Figure 4: Example of a high-quality model Extraction Procedure for BJT The SOT343 package is used in many HF devices and its parasitics need to be considered in the performance of a semiconductor chip. Packages are soldered onto PCBs and distribution of current on the board’s leads and bond wires adds inductive impedance and magnetic couplings. Capacitance between leads and to the ground and other metal parts produces couplings between all these parts and must be included in the models. The package was measured in different connection models on a test fixture and parts of the package were modeled with NI AWR Design Environment, specifically Analyst 3D electromagnetic (EM) simulator. The package parts were then converted to lumped elements and a complete SPICE schematic was created, which was compared with measurement values. Figure 5: Example of the equivalent schematic of each part of the pin hf-praxis 8/2018 45

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