Design of a millimeter wave active antenna module using benzocyclobutene and silicon micromachining
A highly integrated millimeter wave active antenna array is implemented using a novel multichip packaging technique. The goal of the new packaging scheme is to allow the implementation of very compact hybrid multi-chip modules using a low cost micro-machined silicon motherboard and benzocyclobutene (BCB) films. The excellent planarity of BCB allows interlayer connections to be formed using bumps fabricated prior to BCB application. This approach eliminates the need for laser drilling, plasma etching, and plated holes.
The effects of the packaging on the electrical performance of active devices and passive structures are studied. Several representative GaAs pHEMTs are packaged using this technique. Measurements show minimal performance degradation from 1 GHz to 48 GHz. Passive MMIC structures are also studied and small but significant degradation is reported. The interconnection discontinuities formed by the package are studied in detail and lumped circuit models are generated. The performance of these discontinuities as a function of variations in the fabrication process is analyzed. Relatively small changes are noted. This is a major advantage when compared to other interconnection techniques such as bond wires.
The design and measurements of an LNA and mixer MMIC for LMDS applications are presented. The LNA consists of four cascaded stages and the mixer designed is a second harmonic anti-parallel diode configuration. The MMIC is packaged and its performance is characterized.
An antenna architecture compatible with the developed package is proposed. The implementation of active antenna arrays with the presented package scheme is difficult due to the size of the active circuitry. This creates array radiation patterns with large side lobes. Several configurations that reduce this problem are investigated. One array has been fabricated and its measured performance analyzed.
Finally, a highly integrated active antenna array module is presented. The module consists of a 1 x 4 antenna sub-array and a MMIC with an integrated LNA and mixer. This module is extremely compact with a size of only 1.4 x 1.1cm. Its performance is characterized and a loss budget presented.