COMPACT INTEGRATED SWITCHABLE FILTERS BASED ON SILICON STACKED SIP TECHNOLOGY

LI Yu-Hang1,* , ZHANG De-Hai1 , SHI Jun1 , MENG Jin¹

¹Key Lab. of Microwave Remote Sensing, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China

The switchable filters device is one of the core components in broadband communication systems. In a broadband communication system, the performance of the switchable filters device directly affects key indicators of the system such as noise figure, sensitivity, dynamic range, and linearity. As wireless communication systems and integration technologies continue to advance, broadband communication systems are increasingly oriented toward high integration, enhanced performance, miniaturization, and operation at higher frequency bands. However, conventional switchable filters devices exhibit several limitations, such as large physical dimensions, high micro-assembly costs, complex calibration processes, low maturity, and challenges in achieving mass production.

Simultaneously, three-dimensional integrated ultra-wideband Transmit/Receive (T/R) modules are gaining recognition for their practical application potential and represent a natural progression in phased array development. By transitioning from the planar circuit models and chip layouts of traditional radio frequency (RF) circuits to a stacked configuration, multiple chips can be integrated within a confined space, effectively reducing the vertical dimensions of the T/R module.

Aligned with the development objectives of broadband communication systems, the four-channel switchable filters was designed using a two-pole Single-Pole Double-Throw (SPDT) Monolithic Microwave Integrated Circuit (MMIC) switch. Although this configuration increases channel insertion loss and the physical area of the switchable filters, it significantly enhances channel isolation.

Through-Silicon Via (TSV) technology facilitates vertical interconnection between layers and chips. Functional chips are interconnected via a silicon-based interposer and subsequently connected to the package substrate. The application of Stacked System-in-Package (SiP) technology maximizes three-dimensional chip stacking density, reduces the printed circuit board area required for inter-chip interconnections, and thereby minimizes the overall package size while enhancing integration levels. Given that the length of the filter resonant structure influences the total area, and to mitigate parasitic passbands at high frequencies, the filter employs a high-resistance silicon-based LC structure and a Step-Impedance Resonator (SIR) interdigital structure.

Considering that filter calibration techniques constrain both production costs and development cycles—particularly in the mass production of commercial communication equipment—it is imperative to develop a method capable of enabling rapid filter calibration to shorten the production timeline. Leveraging Vector Fitting (VF) and Progressive Space Mapping (PSM) algorithms in conjunction with electromagnetic simulation software, this study achieves rapid microwave filter calibration by accurately extracting the equivalent circuit model. Using this approach, the filter response can closely approximate the ideal value within only 3–5 iterations, demonstrating the accuracy and effectiveness of the proposed method while overcoming limitations such as slow convergence rates associated with previous techniques.

Simulation results of the switchable filters device indicate that each channel circuit exhibits an insertion loss of 1.5–2 dB (including the loss from two switches), a passband standing wave ratio better than 16 dB, and a sideband suppression level exceeding 50 dB at 1 GHz.

Furthermore, the device demonstrates strong adaptability in its process architecture, enabling the internal integration of additional chips such as amplifiers and attenuators to support expanded functionalities. With its compact size, superior performance, and high integration level, this device holds broad application potential across various transceiver modules and is poised to drive emerging trends in RF front-end system development.

Keywords: Switchable filters, Miniaturization, Through-Silicon Via, Stacked System-in-Package technology, Rapid calibration