Case Study – Miniaturized 60 GHz FMCW Radar Sensor For Short-Range Applications
The Problem
Markets that rely on sensors, such as industrial, automotive, and consumer electronics, are heavily competitive. Sensor cost, size, and performance are the key deciding factors that dictate the overall price and quality of the end product. mmWave radar technology allows contactless measurement of close-proximity objects while significantly reducing module size and price. This project aimed to develop a 60 GHz FMCW radar sensor that would operate under heavy space restraints and synthesize extremely steep, wide-band, and highly accurate frequency chirps, which are indispensable in modern high-resolution short-range applications.
Challenges
The development of the 60 GHz FMCW radar sensor faced multiple design constraints:
Compact design
The sensor needed to operate in a very small form factor (32 mm × 22 mm × 7 mm), limiting the space available for antennas, electronics, and the enclosure.
High Precision Requirements
The radar system had to detect objects with sub-2 cm spatial resolution and support very steep frequency slopes to detect objects at a close proximity, less than 20 cm away.
Power Efficiency
The radar module was required to deliver over +17.5 dBm effective isotropic radiated power while maintaining low power consumption, dissipating only 690 mW.
Wide chirp bandwidth
The design demanded chirp bandwidths of up to 10 GHz to enhance spatial resolution while minimizing flicker noise, pushing the radar’s modulation rate to over 200 MHz/µs.
The Solution
Fig. 2. (a) Presented radar sensor module (32 mm x 22 mm 7 mm) (b) Bonded FMCW transceiver chip photomicrograph (2.17 mm x 2.22 mm).
High-performance radar transceiver
At the core of the radar sensor is a fully integrated FMCW transceiver chip developed using SiGe BiCMOS technology. This technology enabled the incorporation of a frequency synthesizer and analog baseband circuitry in a compact chip, allowing high integration in a small package.
Fig. 1. (a) Simplified schematic of the RX chain. (b) 3D Layout preview. (c) Comparison of measured and simulated RX conversion gain.
High spatial resolution with steep frequency slopes
The radar transceiver supports chirp bandwidths up to 10 GHz, enabling sub-2 cm spatial resolution for precise detection. To detect objects at close ranges, the module achieved high modulation rates exceeding 200 MHz/µs, creating steep frequency slopes essential for accurate measurement in short-range applications.
Low power consumption and heat management
Despite its high performance, the radar sensor consumes just 690 mW, which is crucial for maintaining low heat output and efficient operation. The module is encased in a small aluminum housing to help manage heat and protect sensitive components.
Precise signal processing
The baseband processor provides programmable gain and filtering, enabling flexible operation. The system features a programmable gain amplifier (PGA) and active-RC filters, allowing the radar sensor to handle a wide range of radar beat frequencies with adjustable filtering capabilities. The overall gain is programmable up to 60 dB.
Experimental results
| Reference | JSSC [4] | JSEN [5] | TMTT [6] | This work |
|---|---|---|---|---|
| Chip Technology | SiGe Bipolar | SiGe Bipolar | 0.13-μm SiGe | 0.13-μm SiGe |
| Integration Technology | eWLB Package | eWLB Package | Wire Bonding | Wire Bonding |
| Function | VCO+TRX | VCO+TRX | VCO+TRX | FMCW TRX |
| Freq. (GHz) | 57 ~ 64 | 55 ~ 70 | 58.3 ~ 63.9 | 54.5 ~ 64.5 |
| Gant. (dBi) | 6 | 8 | 12.4a | 11 ~ 13 |
| PTX (dBm) | 2 ~ 5 | 10.2 ~ 10.7 | 5.2 ~ 6.4 | 6 ~ 7.5 |
| P1dB (dBm)b | -9.5 | -21 | -18.2a | 0.2 ~ 1.6 |
| GRX (dB) | 18.5 ~ 19.5 | 18 ~ 22 | 14.8a | 38 ~ 43c |
| NFSSB (dB) | 9 ~ 10 | 11 ~ 13a | 13.6a | 15 ~ 17a |
| Chip area (mm2) | 20.25 | 6.72 | 1.02 | 4.84 |
| PDC (mW) | 990 | 924 | 515 | 690 |
The developed radar sensor was tested with corner reflectors placed at distances of 20 cm and 22 cm. The radar system successfully measured these targets using 10 GHz bandwidth chirps with a modulation rate of 240 MHz/µs. The results demonstrated sub-2 cm spatial resolution, as predicted by simulations.
Additionally, the effective isotropic radiated power (EIRP) was measured using a horn antenna, and the module’s output power was consistent with expectations across the full frequency range. The system’s linearity surpassed that of comparable radar sensors in the 60 GHz band, ensuring reliable performance for short-range applications.
Conclusion
The team had created a prototype 60 GHz sensor that integrates mmWave FMCW radar capabilities. The design leverages an advanced frequency generation system with a circuit board featuring embedded antenna arrays. What made this development notable is its compact form factor and cost-effective manufacturing potential, achieved through careful design choices and affordable materials. The performance remains competitive, featuring industry-leading 10-GHz sweep ranges and 240-MHz/μs modulation capabilities. This positioned the device as a promising candidate for widespread adoption in short-range radar applications.
Compact and Miniaturized Radar module
High Spatial Resolution
Integrated Antenna System
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