BY RICHARD COMERFORD, Senior Technical Editor, Electronic Products

If European Microwave Week 2016 (EUMW 2016,
held in London the first week of October), was any indication, in the next
decade the expression “driving the car” may become as archaic as “dialing the
phone.” The industry is in the process of developing new sensor technology for
automobiles that will eventually allow a car to take over all the navigation
and control functions needed to get from one place to another. Referred to as Advanced
Driver Assistance Systems (ADAS), these systems will initially be introduced to
help motorists drive more safely. The functions ADAS can provide, such as
automatic braking, collision avoidance, and lane-keeping assistance, are
expected to serve as the foundation for future self-driving vehicles.

The sensors
that designers are now testing for such applications fall into four broad
categories: optical (cameras), sonar, radar, and lidar. The last of these,
lidar, is similar to radar, but instead or bouncing radio waves off an object
to detect it, lidar uses coherent light from a laser. Hence, “lidar” — “light
radar”, or “light detection and ranging.”

There has
recently been a lot of activity as companies jockey to become the next great
automotive technology suppliers. For instance, at EUMW 2016 Fujitsu Laboratories Ltd. announced development
of millimeter-wave radar technology aimed at helping realize autonomous driving
amongst objects — cars, pedestrians, bicycles, and such — moving at different
speeds; detection at relative speeds up to 200 km/h is possible (Fig. 1).

 

Low_FujitsuCMOSFig1

Fig. 1: Fujitsu’s millimeter wave radar would
allow detection of both slow and fast moving objects in a vehicle’s vicinity.

 

Fujitsu expects
millimeter-wave radar to serve as the “eyes” of ADAS, as it can make
up for the weaknesses of optical cameras in adverse environments, such as at
night, during rain, fog and backlighting. More than just the conventional use
of the narrow 77-GHz band for monitoring in front of and behind vehicles, in
recent years there has been increasing interest in peripheral monitoring radar
that uses a broader band of 79 GHz.

The new technique
avoids a major disadvantage of frequency modulated, continuous wave (FMCW) millimeter-wave
automotive radar: as FMCW radar approaches objects moving at different speeds—such
as a vehicle and a pedestrian—it tends to overlook one of them. Fujitsu’s fast-chirp
modulation (FCM) overcomes the problem by using higher-speed modulation to enable
detection with better distance resolution and a broader range of target-objects
speeds.

To implement
such a system, Fujitsu’s researchers created a CMOS-based millimeter-wave
signal generator capable of modulating its frequencies across a 76 to 81-GHz band
(Fig.2). Combining this circuit with a concurrently developed four-channel CMOS
transmitter circuit to measure and control millimeter-wave beams with a phase
precision within 1 degree, the user can scan their surroundings with a high
level of precision, for example, with resolution at a 5-cm interval anywhere
within a 10-m radius. The signal-generator circuit, which controls the
frequency of the millimeter-wave signal, continuously reads in and counts the
millimeter-wave signal pulses, applies a voltage to the frequency controller
based on that count, and modulates the frequency.

 

Low_FujitsuCMOSFig2

Fig. 2: Fujitsu’s
millimeter wave CMOS signal-generator circuit (a) and 4-channel CMOS
transmitter circuit (b) promise higher precision ADAS radar.

 

Circuits used in
automotive radar are expected to perform normally at ambient temperatures as
hot as 150°C, but with conventional CMOS signal generators, the internal
signals slow down and the counts become inaccurate. Without being able to
increase their modulation speed, the relative speed where detection is possible
is limited to about 50 km/h.

The new
technology makes use of existing millimeter-wave CMOS design technologies, and
focuses on the block in the signal generator that has the most effect on the
counting operation. By adding a function to the block that compensates for
delays caused by temperature changes, Fujitsu Laboratories was able to develop
a new time-compensating pulse counter that operates accurately, even at
temperatures of 150°C (Fig. 3). This circuit enables the world’s fastest
modulation frequency of 2 GHz for every 1 µs at the 80 GHz band, and achieves
the maximum relative speed detection (200 km/h) that is expected of radar.

 

Low_FujitsuCMOSFig3

Fig. 3: Fujitsu
adds circuitry to its radar circuitry to correct pulse readable timing error
due to rising temperature.

 

Fujitsu
Laboratories says it is working on developing a radar chip that integrates a
high-performance processor and other elements, and further advancing high-end
functionality, with the goal of making these technologies practical from 2020.

Also at EUMW
2016, National Instruments gave a
technology demonstration of a new ADAS Test Solution for radar in the 76–81 GHz
range, based on NI’s mm-wave front-end technology and the recently released
PXIe-5840 second-generation vector signal transceiver (VST). Stefano Concezzi,
vice president of the global automotive initiative at NI, noted that, “With regulatory
requirements still evolving, the flexibility of this solution allows engineers
to quickly adapt their test systems to address the challenges of new radar
scenarios.”

Because it combines
the VST with banded, frequency-specific upconverters and downconverters
designed to test the 76–81 GHz radar band with 1 GHz of real-time bandwidth, the
system can function as a mm-wave vector signal generator and vector signal
analyzer. Engineers can program the VST’s FPGA with LabVIEW to use the ADAS
Test Solution for radar target emulation, a technique in which test equipment
emulates the radar cross section, range, radial velocity and angle of arrival
of a particular object. This is essential for testing a radar system’s software
and hardware.

Right after
EUMW 2016, Infineon Technologies

announced its acquisition of the Dutch fabless semiconductor company Innoluce
to develop chip components for high-performance lidar systems. The company
believes lidar, radar, and camera will be the three key sensor technologies for
semi-automated and fully automated cars, so with the acquisition of Innoluce it
plans to deliver expertise in all three complementary sensor systems which
provide the redundancy required for autonomous driving.

Infineon says
that the first lidar systems introduced in premium cars within the next couple
of years will be based on mechanical scanning mirrors and, thus, be bulky and
rather expensive. To become a standard feature in all car classes, lidar
systems need to be semiconductor-based, thus getting more compact,
cost-effective, and robust.

Over
the horizon

Since standard
sensors such as radar, optical, ultrasonic, and lidar are all line-of-sight,
they can only detect risks within view of the vehicle. The Australian firm,
Cohda
Wireless
is working on a system that can detect hidden-from-view threats, so it can extend
the horizon of awareness beyond what the driver can see, such as when two cars
are approaching each other around blind corners, over the crests of hills, or
when there are trucks between them.

Cohda recently
introduced vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) — or V2X
— equipment that it sees as an essential technology for the next generation of
Advanced Driver Assistance Systems (ADAS) as well as autonomous vehicles. V2X
is a wireless sensor system that allows vehicles to share their sensor data
with other vehicles and highway equipment around them. Cohda’s V2X technology
is a non-line-of-sight sensor with 360-degree awareness that uses accurate satellite positioning with embedded dead reckoning
technology

provided by u-blox
. Based V2X, Cohda’s Dedicated Short‑Range Communications (DSRC) system enables,
for example, early warning of an imminent collision, oncoming traffic, presence
of road workers, and unsafe speed based on vehicles in the vicinity.