Saturday, November 21, 2015

BGA Package Simulation


BGA Package Design and Simulation

BGA Package Design and Simulation

A BGA package is very popular package style for high speed digital applications due to high density, low thermal resistance, and low inductance leads. In a BGA package, the electrical connections are made of solder balls stuck to the bottom of the package. However as the operating frequency and data rate go up, it is critically important for IC designers to understand the package’s electrical performance because of the parasitics that can come from the package.

A package is the second most expensive part next to the silicon and can add 6 to 8 weeks to the cycle time. Given the very tight opportunity window for the majority of digital products, a failure to produce a successful package design can significantly reduce the profit margin or even kill the entire project. Designers are challenged to get the desired package performance right the first time. It requires fast and accurate analysis of BGA packages with EM simulators. A 45 mm package is simulated for high speed traces and simulated performance is compared
against measured data.

Wednesday, September 16, 2015

Designing Multilayer Printed Antennas with wide bandwidth

Multi-layer Microstrip Antenna

Multi-layer Microstrip Antenna

Generally impedance bandwidth of patch antennas varies from 2-3% for single layer direct coupling or probe coupling  and can be further enhanced by coupling the power from the strip line through an aperture (slot) in the ground plane and/or printing patch effectively on the foam material whose dielectric constant is nearly equal to that of air [. In such case the feed network is isolated from the radiating element by a ground plane, which prevents spurious radiation. The resonant or non-resonant slot couples energy from the stripline to the patch. If slot is resonant, it provides another resonance in addition to the patch resonance, resulting in an antenna with 10-15% impedance bandwidth. However, the resonant slot has strong backlobe, which substantially reduces the gain of the antenna. Non-resonant slot has better front to back ratio, which results in improvement in efficiency with narrow bandwidth. Hence multilayer microstrip antennas are difficult to optimize when maximum efficiency is required in limited allowable available space with weight as low as possible.
The proposed configuration is shown in Fig. 1, where patch and feed lines are printed on the same substrate and foam layer is sandwiched between the patch and the ground plane to improve radiation efficiency and bandwidth performance by reducing the effective dielectric constant of the combined sandwich layer. Terminating the patch with high impedance line can control spurious radiation from the feed line network and cross-polar performance is improved by employing proper phase cancellation technique.

Design


Design of the antenna begins with proper selection of material, its dielectric constant and height of the substrate, which plays a crucial role when weight and gain has to be optimized simultaneously. Low dielectric constant, which enhances the radiation efficiency for the patch, can give rise to spurious radiation from the feed line network where generally high dielectric constant is generally preferred to confine the electromagnetic field. Foam material would be the best candidate for patch but it cannot be directly printed on foam material. A compromise is to be arrived so as to increase the dielectric constant by introducing a layer of RT Duroid with dielectric constant 2.2 and height 0.79 mm both for mechanical rigidity and electrical requirement of feed line. The single patch is optimized using IE3D CAD software in terms of bandwidth and cross polarization and it is terminated by 240  to reduce probable spurious radiation from a junction formed by patch and feed line. Optimized dimensions of single patch are shown in Fig. 2 with material properties in Table 1.