High-efficiency mm-wave transceivers with multi-functional on-chip spherical dielectric resonators for simultaneous use as antenna and high-Q resonator

• Applicants: Professor Dr.-Ing. Frank Ellinger; Professor Dr. Jan Hesselbarth
• Subject Area: Communication Technology and Networks, High-Frequency Technology and Photonic Systems, Signal Processing and Machine Learning for Information Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544642611

Millimeter-wave (mmW) transceivers are key for future communication and sensing applications. Transistors benefit from scaling. However, the losses of passives such as resonators and connections limit the possible performances. External dielectric resonators provide a promising solution as they enable very high Q-factors (> 1000), enable further functionalities, e.g. as antenna, as well as efficient on-chip coupling. In the previous project SPHERE, we demonstrated that a low-loss dielectric sphere antenna can be coupled directly on-chip to a BiCMOS integrated power amplifier (PA) while providing very efficient 4-to-1 power combining leading to a measured record power added efficiency of 14.2 % at 100 GHz and 20 dBm output power. By on-chip coupling to a BiCMOS oscillator, we showed the feasibility of leading-edge phase noise down to -115 dBc/Hz at 10 MHz. Typical transceivers would require 4 spheres: one for antenna and power addition, and one for oscillator, in both the transmitter (TX) and the receiver (RX). In this follow-up project SPHERE 2, we have the following novel objectives: 1. Analysis, simulations and experimental demonstration, that the radiating mode for antenna operation (incl. power combining) and resonance mode for low noise oscillators can coexist in same single sphere component at the same time thereby reducing the required number of dielectric spheres and thus, chip size. This needs novel design strategies, e.g. to make sure that the resonator mode is not affected by the antenna mode. Unwanted couplings must be minimized to about -40 dB. We conducted first promising feasibility simulations to verify this novel project idea. 2. Based on (1) we design BiCMOS TX and RX circuits considering and exploiting the specific properties (e.g. Q, interfaces, impedances, coupling, etc.) of the multifunctional dielectric sphere enabling both antenna and resonator functionality. The ICs benefit as follows: PA through low-loss antenna connection and power combination; low-noise amplifier path, thanks to low-loss antenna connection and higher linearity due to power sharing; and oscillator, by high-quality resonator. Down- and up-mixers are designed for (3). 3. Building upon (2), a transceiver frontend (incl. antennas) with multifunctional spheres in TX and RX is implemented demonstrating data transmission benefiting from the accumulated advantages of the spheres. SPHERE 2 is associated with many research questions, e.g.: Which circuit architectures can optimally exploit advantages of high-Q sphere while taking into account its multi-mode characteristics and boundaries? How weak/strong is unwanted cross-talk between resonator and radiating antenna modes? What is impact? How can it be minimized? SPHERE 2 combines the complementary competences of Hesselbarth´s team in terms of RF system design, packaging and passives (such as dielectric spheres) with the knowledge of Ellinger´s group in terms of millimeter-wave BiCMOS IC design.

• DFG Programme: Research Grants