A decade ago, it was tough to imagine that self-driving cars were something feasible in the near future. We owe many autonomous driving advancements to technologies such as radar, which are creating a revolution in the automotive industry.

But radar is a versatile technology with use cases beyond the automotive industry. For instance, advancements in radar systems can actively monitor the health of patients without embedding devices into the human body. These devices also abate privacy concerns while ensuring a fast response in case of an emergency. 

What Is a Radar-on-Chip? 

Traditionally, the use of radars was limited to military purposes. However, with advances in the fabrication of semiconductor technologies (CMOS, BiCMOS), it has become possible to manufacture radar-on-chip.

Nowadays, radar-on-chip is abundantly present in the consumer market. The radar signals can both “see” objects behind walls kilometers away and create images of the inside of the human body.

The first generation of radar-on-chip included a low-noise amplifier (LNA), a double-balanced resistive mixer, a voltage-controlled oscillator (VCO), and an active balun buffer amplifier. In the figure below, the chipset uses a quadrature receiver architecture.

One of Bell Lab's early continuous-wave radar sensor chips

One of Bell Lab’s early continuous-wave radar sensor chips. Image used courtesy of Changzhi Li et. al

Since then, various architectures have been proposed, developed, and commercialized to create fully-integrated radar sensor chips.


Radar Systems

A radar system typically consists of a radar transceiver, antenna, and circuitry to process/extract information from radar signals. The radar transceiver includes the signal synthesizer, power amplifier (PA), low-noise amplifier (LNA), mixer, and baseband circuitry.

A modern radar has all the key circuitry integrated onto a single chip or PCB. Due to the small feature size, various consumer applications can be deployed on a single chip using sophisticated embedded signal processing and control circuits.

Compared to camera-based technologies, radar systems can easily obtain a target’s range, speed, and angle without being affected by weather extremes. This has altogether enabled the mass use of radars in autonomous cars, healthcare monitoring devices, and IoT applications.

60-GHz micro-radar system-in-package

60-GHz micro-radar system-in-package. Image used courtesy of Te-Yu Kao

Radar systems can be classified into two categories, depending on the type of transmitted signals: continuous-wave (CW) radar and pulse radar.

Both types of radar have various sub-categories. For example, single-tone CW radar, FMCW radar, and FSK radar are types of CW radar. At higher frequencies of transmitted signals, a radar’s detection sensitivity and resolution improve; this is why FMCW radar chips in the millimeter-wave range have become quite popular for road safety

Radar Chips in Automotive Applications

The capabilities of the radar system are continuously expanded by phased array, digital beamforming, and multiple-input multiple-output (MIMO) techniques.

Radar and Beamforming

For example, the Tesla Model 3 uses one radar (Continental ARS4-A) and has digital beamforming capability, scanning for short- and far-range distances. This is used for forwarding collision warning, emergency brake assist, collision mitigation, or adaptive cruise control (ACC).

Two companies, RFISee and Vayyar, offer promising products that use phased array and MIMO techniques, respectively, in tandem with radar systems.

Radar and Phased-Array Technology

RFISee has released the industry’s first phased-array 4D imaging radar-on-a-chip.  The high-resolution, low-cost radar sensor can generate a real-time 3D location and velocity map of a car’s surrounding objects.

Because phased array is a costly technology, its adoption in the automotive industry has been a concern, which is why radar use was initially limited to advanced military systems such as F-35 fighter jets. With RFISee’s radar-on-chip solution, the receivers ensure a much-improved radar image, a better signal-to-noise ratio, and a detection range of obstacles such as cars and pedestrians that Vayyar says is six times broader compared to existing radars.

Prototypes of RFISee’s radar are under evaluation by top automotive OEMs and Tier-1s, the company says.

The VYYR2401A1 IC

The VYYR2401A1 IC. Image used courtesy of Vayyar

Radar and MIMO Technology

Another startup from Israel, Vayyar, has recently developed automotive-grade radar chips based on MIMO technology. The chip covers imaging and radar bands from 3 GHz-81 GHz with 72 transmitters and 72 receivers. Enhanced by an integrated, high-performance DSP with large internal memory, Vayyar’s sensor executes complex imaging algorithms without any need for an external CPU.

Vayyar also produces radar-based imaging solutions for applications such as smart homes and robotics. In comparison, the phased array-based radar system from RFISee is targeted specifically at automotive applications. 

Radar Chips for Biomedical Devices 

In medical applications, radars can detect small dielectric discontinuities inside the human body and small organ movements. This allows radar systems to identify many health conditions, including tumors and cardiorespiratory conditions.

One promising alternative to breast-cancer detection is UWB radar instead of X-rays, which are widely used. Another important application of radar in biomedical devices is contactless health monitoring. The radar is used to transmit an RF signal to a person and receives the reflected echo, which detects the person’s speed and absolute distance.

This application is useful when a person falls and is unable to call for emergency assistance or press a call button. In these situations, a device that can detect the fall and call for medical care can be lifesaving. 

Imec’s low-power 60 GHz radar module

Imec’s 60 GHz radar module. Image used courtesy of Imec

Last week at IEEE RFIC, researchers from Imec presented a compact and energy-efficient 60 GHz radar system that can be integrated in smart health devices such as smartphones, health monitoring systems, or wearables.

“The radar enables such devices to sense their surroundings, which will shape the way in which we control and use these devices,” says Barend van Liempd, program manager of radar technology at IMEC. “For instance, a phone with integrated radar on your bedside table can monitor sleep quality by contactless tracking of breathing rate and heart rate variability.”

What’s in the Future for Radar Chips? 

Radar chips have definitely found solid ground in the automotive industry and are available in a host of consumer devices at low costs. Various auto-manufacturers are employing radars in their own ADAS technology. The ultimate benefit here is public safety on roads.

The boom of radar chips in biomedical devices, by contrast, remains distant. Certain organizations have found good use of radar sensors to monitor building occupancy during COVID-19. The radar systems in these smart buildings can measure room occupancy for social distancing and even monitor the heartbeats and temperature of individuals for infection.

Considering the outbreak of COVID-19 where the world did not have appropriate infrastructure to effectively control the spread of disease, pursuing the use of technologies such as radar systems in biomedical devices may yield immense benefits in the future.

Source: All About Circuits