Development and Integration of 60 GHz LTCC RF Front-End Key Circuits

This project develops 60 GHz RF front-end circuits and integration method with LTCC fabrication process and substrate-integrated waveguide (SIW) structures, which has advantages of high gain, wideband, high selectivity, high isolation, and easy integration. This two-year research project consists of the designs of LTCC 60 GHz filters, antennas, duplexers, and the RF frond-end integration. In the 60 GHz filter design, SIW and cross-coupled structures are adopted to achieve superior frequency selectivity. Two antisymmetric U-shaped slots connected by a via is proposed to construct the negative coupling structure, which is simple and especially useful for 60 GHz applications. Moreover, the U-slot structure possesses a wide range of realizable coupling coefficients from -0.008 to -0.075. The simulation results achieve a bandwidth of 12% at 59.6 GHz with superior frequency selectivity. In the design of 60 GHz antennas, this project is the first to introduce the design of 60-GHz substrate-integrated cavity-backed slot (SICBS) antenna arrays with parasitic patches achieving high gain and wide bandwidth. A 2×2 antenna array is designed to further enhance the gain and bandwidth. The simulated results show a bandwidth of 22% and a gain of 9.6 dBi. The 16×16 antenna array is further proposed to achieve BW = 20 %, gain＞28 dB, and area ＜ 8 cm×8 cm. A novel experimental setup for on-chip radiation pattern measurement is also proposed to overcome the difficulty due to the mechanical alignment of tiny antenna size and the space required for probe stations in conventional anechoic chambers. The task for the second year is to develop LTCC 60 GHz duplexers and integration of RF front-end circuits with LTCC as a carry board. Substrate integrated waveguide cavity and frequency selective surface (SIWC-FSS) structure is applied together to design high/low-band bandpass filters with large attenuation rate in single edge of the passband. Duplexers constructed with the proposed filters have advantages of high isolation and a compact size. The simulation results achieves insertion loss less than 3.5 dB and isolation large than 30 dB. System in package (SiP) method is utilized for the RF front-end integration, which is simple and cheap. Firstly, the duplexer and antenna are embedded together within LTCC layer. The equivalent circuit model of flip-chip BGA structure is developed. Flip-chip BGA technology is then applied to connect duplexer, power amplifier, low noise amplifier, and bias circuits with LTCC substrate as a carry board. Superior design of the EM shielding and heat dissipation is considered. Detailed test items are planed for validating the function of transmitting and receiving channels. This project will fabricate and measure several circuits to demonstrate the capability of the proposed circuit structures. According to the aforementioned, this project is helpful for development of 60-GHz circuits, RF front-end integration, and promotion of LTCC technology at high frequency, especially in Taiwan.

Project ID:PB10207-1902
External Project ID:NSC102-2221-E182-012