From Gunnplexer to MMIC: An Implementation on a Single Chip

The development of chip manufacturing processes over the last few decades led to smaller and smaller technology nodes with maximum transistor frequencies approaching the terahertz domain [1]. Consequently, it became feasible to integrate the different building blocks of millimeter-wave transceivers on the die, replacing several discrete elements in systems and leading to smaller form factors of sensor implementations. For example, in automotive radars, the development in silicon germanium (SiGe) technologies enabled integrated voltage-controlled oscillators (VCOs) fulfilling the demands for a signal source on the chip [2]. This led to cost-efficient radar systems including oscillators, mixers, and amplifiers on the die. A common problem with those monolithic microwave integrated circuits is that high-frequency connections from the chip to the printed circuit board have a large impact on the performance. Expensive substrates and sophisticated chip-to-board connections are necessary to address the losses that increase with the rise in frequency. As a result, on-chip antennas became very attractive in recent years [3] because they make those complex off-chip connections obsolete. Additionally, the size of antennas scales with the wavelength, which leads to a decrease in size with increasing frequencies. In automotive radar applications, the antennas are typically placed on the printed circuit board, as the operation frequencies of 76 GHz to 81 GHz would lead to a large chip area for the on-chip antennas; thus, an implementation is not worthwhile.