Miniaturization of mmWave sensors enabled by CMOS technology

Most commercial radar systems, specifically those in advanced driver assistance systems (ADAS), are based on silicon-germanium (SiGe) technology. Today’s high-end vehicles feature a multichip SiGe radar system. While SiGe radar systems meet the high speeds demanded by 77GHz automotive radar for adaptive cruise control, they are big and bulky, taking up a lot of board space.

As the number of radar sensors in vehicles climbs to at least ten (front, rear and corners), space constraints dictate that each sensor be smaller, lower power and more cost-effective. Some current radar systems under development will push the integration of the transmitter, receiver, clock and baseband functionality into a single chip, which will reduce the number of front-end chips from four to one. But that is just for the radar front end.

TI has taken integration to the next level, leveraging complementary metal-oxide semiconductor (CMOS) technology to integrate intelligent radar front ends with embedded microcontrollers (MCUs) and digital signal processing (DSP) capabilities. Processing is co-located with the front end to minimize radar system size, power, form factor and cost, further enabling the mounting of multiple radar systems in vehicles.

Figure 1: Single chip integration enabled by CMOS

Classical advantages of CMOS technology include higher transistor density and lower power. Digital scaling in CMOS decreases the power and size and increases performance at every node. Driven by these digital transistor improvements, the speed of CMOS continues to increase and is now sufficient for 79GHz ADAS applications. The 79GHz band offers the 4GHz bandwidth essential for higher-range resolution. Future radar systems will also need support for short range, with better angular resolution translating to more antennas in the radar systems. TI’s sensors in CMOS technology can support this scalability to high-volume mass production.

CMOS technology has further enabled TI to embed the digital within the analog, leading to new system configurations and topologies for radar system deployment. For example, embedded MCUs in TI’s single-chip millimeter-wave (mmWave) sensor enable semiautonomous control of radio frequency (RF) and analog subsystems. TI’s CMOS sensors provide digital assistance to the analog, for adaptation, flexibility and robustness over environmental and manufacturing variations. Digital assistance extends to real-time control of flexible chirp generation and advanced self-monitoring capabilities.

The dynamic range of a radar system depends on receiver noise floor and tolerances to self-jamming caused by bumper reflection. These heavily depend on architecture and system capabilities such that a CMOS system – with wider intermediate frequency (IF) bandwidths, more channels and precise low-noise linear closed-loop chirp generation – can have superior system-level performance for certain radar applications.

CMOS technology changes the design of mmWave sensors, embedding increased intelligence and capabilities. CMOS technology has enabled TI to deliver a high-performance, low-power mmWave sensor portfolio, scaling from a high-performance radar front end to single-chip radar.

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