Cheng-Hua Tsai

A mobile WiMAX RF front-end module with integrated passive components and novel material

System in package (SiP) plays an important role in the mobile communication market, while it can efficiently improve the size shrinkage, cost-effectiveness and available time of the products. Good achievements have been realized by other works in the past years, such as VCO, PA, BPF, Balun, Bluetooth module, and Wi-Fi systems with embedded passives [1-4]. Nowadays, the current trend is towards personal multi-media applications requiring high transmission data rate and mobility. Therefore, worldwide interoperability for microwave access (WiMAX) communication system is developed to meet the requirements. In this system, the operation of the wide channel bandwidth and the linearity of signals are the critical issue, especially in the circuit designs. This paper describes the design methodology of a RF front-end module with the modelling of embedded passive components that integrates with the power amplifier (PA), RF switch, BPF, and LPF circuit and operates over 2.3 - 2.7 GHz mobile WiMAX system. Additionally, the novel high-permittivity organic material with DK~20.8 at 2.4 GHz was also been developed. It minimizes circuit areas, greatly increases the quality factor of passive components and can be compatible with traditional PCB lamination process to reduce the production cost. By this material and multi-layers substrates realized by PCB process, the embedded passives largely replace SMDs including the inductors, capacitors, and filter components. The final designed embedded RF front-end produces 23 dB gain, better than 10 dB return loss in the TX path; and 2.5 dB noise figure with greater than 11 dB return loss in the RX path. Through the embedded technologies, 10 capacitors, 5 inductors, and 2 filters were embedded into the substrate, occupying almost 70.8 % of the total passive components, and the size of embedded front-end is less than 600 times 600 mil2. These technical results not only promote the technology of SiP but provide the solutions for the broadband mobile communication applications.

A high isolation dual strip monopole antenna

A dual strip monopole antenna for 2×2 MIMO application is designed using an open strip stub and a parasitic strip, which are respectively employed for band stop filter and pattern diversity. The antenna satisfies the bandwidth requirement of 200 MHz (2.5 to 2.7 GHz) in IEEE 802.16 WiMAX standards, and the in-band isolation between the two monopoles is higher than 20 dB. The proposed design is successfully integrated with SiP (System in Package) and embedded passive components. After system verification, the measured EVM of the WiMAX system is below -30 dB at a 3m distance.

Design and implementation of ultra-thin SiP modules

In recent years, SiP (System-in-Package) or SOP (System on Package) technology has become an attractive solution for size reduction of mobile devices. Passive components such as inductors or capacitors can be integrated into the substrate. The dimension of embedded capacitors can be further reduced by using high dielectric constant material. Thus, size miniaturization and cost reduction can be easily achieved through the replacements of surface-mounted devices (SMDs) on the substrate.chip can be reduced. Wafer-level packaging technology, wafer thinning technology, buried ultra-thin chips technology, and embedded passive components technology are both integrated in this paper to achieve a miniaturized ultra-thin SiP module. The feasibility of the ultra-thin SiP technology was verified by using a GPS module. For high integration and flexible design, an eight-layered organic substrate process is used in this project.

The database of Embedded Passives for RF-SiP design

Embedded Passives (EPs) are considered an attractive option to design RF-SiP (System in Package) modules. EPs are benefit by the shortened interconnections between active or passive components, which can make better RF-SiP modules. In this paper, we propose the database of EPs for RF-SiP design. The database provides the corresponding parameters of EPs, such as electrical characteristics, structures and material properties. The well-arranged database can help users to make the optimal design of EPs. Then the database of EPs was implemented to design the matching circuit of a power amplifier. The feasibility of the database has been proved via this case.