Pergamon

J. Franklin Inst. Vol. 335B, No. |, pp. 13 21, 1998 Copyright © 1997 The Franklin Institute

P I I : S0016--0032(96)00112-3 Published by Elsevier Science Ltd Printed in Great Britain

0016-0032/98 $19.00+0.00

Microwave and MiUimeterwave Applications in Automotive Electronics-- Trends

by R A H U L D I X I T

T R W - A E N , Farmington Hills, MI, U.S.A.

ABSTRACT : Over the next decade, there will be a significant increase in the electronic content of automobiles. The continuing emphasis on vehicle and occupant safety, on driver convenience and ergonomic interfaces will provide many challenges and opportunities for the engineering community. Advanced products like automotive radar and the introduction of ITS (Intelligent Transportation Systems) products, will also require the development of cost effective products. This article will survey the issues and concepts related to microwave and millimeterwave product applications.for ITS. As the article will show, there is significant worldwide opportunity and activity in improving transportation infrastructure, by using capacity and safety enhancing products. Additionally, the article also provides an overview of the advances in developing a mmw radar sensor for automotive applications. While the promise of large business opportunities still exists, there are significant challenges to developing a commercially viable radar based system for the automotive consumer. These include issues related from systems configurations, and FCC licensing, and developing the various components in the radar unit itself. In summary, the article will also touch on the cost, manufacturability and human factors topics. © 1997 The Franklin Institute. Published by Elsevier Science Ltd

I. Introduction

Commercial media presents an image of idealized driving that only a few of us actually realize. Usually we find ourselves jammed in traffic, creeping along with many fellow drivers in similar conditions. The car of our dreams travelling along winding country roads of our imagination just is not coincident with today's reality. With a worldwide car park approaching 500 M vehicles, and increasing at the rate of 50 M vehicles annually, something must be done. Modern electronics now promises some help. Within the next decade, cars and other vehicles will be equipped with a bristling array of devices aimed at helping dodge other vehicles, see obstacles at night and in fog, and avoid getting lost. Technologies like microwave radar, infrared and magnetic sensors, and satellite navigation are being adapted for use on the road. The roadways are also being upgraded to utilize the capabilities provided by enabling electronics.

This article is a survey of transport telematics--specifically the microwave building blocks for in-vehicle and infrastructure [Intelligent Transportation Systems (ITS)]. For

13

14 R. Dixit

ITS Architecture Overview

Ma ̧ ation

Anti-Th

Roadside information

Information Kiosk

)nvenlences

. . . \

3ellular Phone

ALocatio ~ (G.P.S.)

Toll Collection Emissions monitoring Road condition beacon Road congestion information Service facilities Flow/Rate monitoring Commercial vehicle systems Regulartory services (police) Communications gateway

FIG. 1. ITS architecture overview.

ITS, there are experimental deployments in virtually every major North American city and in most developed countries of the world--simply because use of this technology provides greater public safety and convenience, and for lower cost than building more roads! Regarding in-vehicle millimeterwave applications, there is considerable interest in developing a radar based situation sensing product to enhance driver safety and convenience. However, the wide spread deployment of such products has been awaiting progress on several fronts. This includes finalization of the systems configurations for specific applications and the FCC licensing status. Also there are issues and choices related to antennas, RF head, VCOs, and subsequent signal processing. Finally, there are larger issues of manufacturability and factory alignment as well as opinions about cost and human factors.

II. Intelligent Transportation Systems

With the finalization of the National Architecture definition phase, a consensus on the scope of ITS is emerging. This is illustrated in Fig. 1 and summarized in Table I, which partitions the major ITS sub-components. These include:

1. Travel and Traffic Management 2. Advanced Vehicle Safety Systems 3. Electronic Payment 4. Emergency Management 5. Commercial Vehicle Operation and 6. Public Transportation Management

Much of what is associated with ITS in the U.S.A., is contained within these broad

Microwave and Millimeterwave Applications

Intelligent Transportation System

15

M a i n S e r v i c e

• T r a v e l a n d Traf f ic M a n a g e m e n t

- Route guidance, flow monitoring, incident management

• A d v a n c e d V e h i c l e Sa fe ty S y s t e m s

- Coll ision warning/avoidance, injury reduction, automated vehicle

• E l e c t r o n i c P a y m e n t

- Smart cards

• E m e r g e n c y M a n a g e m e n t

- Mayday

• C o m m e r c i a l V e h i c l e O p e r a t i o n

- Fleet monitoring, hazard and mayday

• P u b l i c T r a n s p o r t a t i o n M a n a g e m e n t

- Trip planning/scheduling, demand based flexibility

FIG. 2. Intelligent transportation system.

topics (1). Furthermore, there are world-varying acronyms that describe the current efforts underway in experimental sites around the globe. However there still seems to be a general scepticism about the question of deployment. The ITS effort thus now turns towards communication, buy-in and lobbying. Competing with microwave and millimeterwave products, which provide rugged all weather operation, are optics and ultra-sonic phenomenology products. The choice dependent on suitability for the task and cost.

Product opportunities for microwave and millimeterwave products can be grouped into a few major categories. Those which provide driver navigation and congestion information, those which aid in driver safety and occupant comfort, those which aid in vehicle location and security, and those which improve traffic capacity and flow. Typically these are microwave and radiowave roadside beacons for monitoring pollution, congestion, traffic flow, cross-section management, traffic density, and road hazard. Also for communication, these include cellular and pager systems, DSRC (Direct short range communications) transponders for automatic toll collection and MayDay-type emergency dispatch transponders. Additionally, using GPS (Global Positioning Satellite) signals, and detailed cartological information, communications interfaces for navigation support. Finally, millimeterwave radar systems for ICC (Intel- ligent Cruise Control), lane change aid and back-up warning products for HOV (High Occupancy Vehicle) platooning. This is summarized in Table II for Infrastructure products and Table III for in-vehicle products (2, 3).

IlL Radar Sensors

Many radar based automotive products are possible (4). They range from using forward looking narrow beam radars for autonomous cruise control, and collision

16 R. Dixit

Opportunities in Microwave and Millimeterwave for Infrastructure Products

• T r a f f i c F l o w M o n i t o r i n g

- Flow rate

- Volume, speed, type

• R o a d C o n d i t i o n B e a c o n s

- Water/Ice on road

• I n t e r s e c t i o n / A c c e s s C o n t r o l

- Lights

- On-ramp gating

• V e h i c l e B e h a v i o r

- Speed

• S c h e d u l i n g

- Buses

- Fleet management

• T o l l C o l l e c t i o n

- Public

- Commercial

• HOV Lanes

- Platooning

• L o c a t i o n / N a v i g a t i o n / C o m m u n i c a t i o n

• I n f o r m a t i o n

FI6. 3. Opportunities in microwave and millimeterwave for infrastructure products.

warning, to side looking broader beam radars for lane change aid and side impact warning, to rear facing wide beam radar for back-up warning. A sampling of possible vehicle based radar products is presented in Table IV. Figure 3 provides this author's view of near and long term deployment schedules for radar based in-vehicle products.

Opportunities in Microwave and Millimeterwave for In Vehicle Products

• R a d a r • I n f o r m a t i o n

- F o r w a r d look ing - Roadside

- Rear looking - Emergency

- Side looking - Traff ic

- Downward looking • P e r f o r m a n c e

• C o m m u n i c a t i o n s - Emissions

• G e o g r a p h i c L o c a t i o n - Tire pressure

- Navigation - SteeringlLane keeping

- Anti-theft/stolen vehicle • To l l P a y m e n t recovery • Speed

• R e m o t e K e y - Moni tor

- Entry - Local cast - Start/Immobil ize

• A c c e s s • E n t e r t a i n m e n t - Into vehicle

- AC-HAP

- Industrial/Mil i tary sites

FIG. 4. Opportunities in microwave and millimeterwave for in-vehicle products.

Microwave and Millimeterwave Applications

In Vehicle Radar Applications

17

• Back Up Warning (BUW) - rear facing - Alerts the driver i f an obstacle is in the way when backing the

vehicle

• I n te l l i gen t Cru ise C o n t r o l (ICC) - f o rwa rd l o o k i n g

- Maintains a safe distance from the preceding vehicle by providing information to the cruise control and braking systems

• Co l l i s i on Warn ing S e n s o r (CWS) - f o rwa rd l ook ing

- Detects and warns the driver of potentially dangerous obstacles in the roadway whi le in forward motion

° L a n e C h a n g e A id (LCA) - s ide l o o k i n g

- Detects the obstacle and alerts the driver to a potential col l is ion prior to a lane change

• V i s i o n E n h a n c e m e n t Sys tem (VES) - f o rwa rd l ook ing

- Aid in night driving and in inclement weather condit ions (rain, fog, snow)

FIG. 5. In-vehicle radar applications.

There are many competing electromagnetic phenomologies, including microwave and optical, however millimeterwave has been selected for its small size and all-weather performance. The FCC frequency allocations for vehicular radio has identified 4 bands for consideration, and has initially approved 47.247.4 and 76.0-77.0 GHz as radar bands. This is summarized in Table V. Similarly, FMCW has generally been chosen

F r e q u e n c y A l l o c a t i o n s

US - FCC (Docket #89-116, Part 15 rules)

Section 15.245 Field Disturbance Sensors Frequency (GHz) Field Strength (MVlm @ 3m)

Fundamental Harmonic . 9 0 2 - .928 5 0 0 1.6

2 . 4 3 5 - 2 . 4 6 5 5 0 0 1.6

5 . 7 8 5 - 5 .815" 5 0 0 1.6

1 0 . 5 0 0 - 1 0 . 6 5 0 2 5 0 0 25 2 4 . 0 7 5 - 2 4 . 1 7 5 2 5 0 0 26

Proposed US - FCC allocation for Vehicular Radio Systems Frequency (GHz) Max. Power 47.2 - 47.4 30 MWlcm ~ @ 3m 76.0 - 77.0 30 94.7 - 95.7 30

139 .0 - 1 4 0 . 0 30

• Japan -60 GHz

• Europe - 76 GHz 94 GHz

* Also proposed European Dedicated Short Range Communication (DSRC) frequency

FIG. 6. Frequency allocations.

18 R. Dixit

Sensor Block Diagram

Antenna

Sensor RF head

vco 9 Mixer

Signal Processor

V . . . . . . . . . z l e Comm Bus l i P - vehicle speed, yaw rate

OIP - target distance, speed, trajectory

FIG. 7. Sensor block diagram.

over traditional pulse or time of flight approaches. The FMCW waveform system offers easy modulation, high average power, large bandwidths, permitting very good resolution and Doppler processing, with good performance at close range yielding high, accurate information on range and closing rate (5).

IV. Sensor Components

Regardless of the vehicular application identified in Table IV, a modern ranging sensor consists of three major subassemblies, the antenna, the transmit/receive subsy- stem, and the signal processing module. This is shown in Fig. 2. A typical trans- mit/receive RF-head consists of a linearized VCO modulator, a RF power stage, and a balanced mixer stage preceded by a high dynamic range low noise amplifier. For forward looking applications, in order to correctly identify the lead-vehicle target, and accurately report its distance and relative speed high resolution spatial selectivity is required. To cover all vehicle types and weather conditions on U.S. interstate-type highways, general consensus is that 3 degree elevation and 9 degree azimuth field of view is desired. However, VCO phase noise can limit the range accuracy by widening the spectra of the transmitted signals, causing spreading of the beat IF frequency. This error can be reduced by inclusion of a closed loop frequency sweep linearizer. Recent advances in digital technology have resulted in the development of new methods for phase noise reduction (6). Table VI provides a reference for typical specifications for forward looking radar as used in Intelligent Cruise Control applications.

V. Manufacturability

Little has been published in this matter, largely because this is yet to be demonstrated. The problem with making a low cost, but very high performance radar sensor requires

Microwave and Millimeterwave Applications

Automotive Radar Deployment Time Table

19

Near Term: Ku, W bands

Forward collision warning

Rear obstacle detection

Lane change aid

Intelligent cruise control

Long Term: Ku, W, D bands

Predictive crash sensing

Forward collision avoidance

Vision enhancement

Automatic lane keeping

FIG. 8, Automotive radar deployment time table.

that the RF-head be generally wire-bond-free. This is not practical, both due to current stage of technology (VCO phase noise, and the need to launch the energy into an antenna) and due to the complex multi-beam configurations required. This means, that to accurately place mmw interconnections, manufacturing technologies need to be developed which allow high accuracy/high repeatability wire-bond placement.

Key Technical Requirements ICC

Inputs Vehicle speed Y a w

Ou tpu t s

E n g a g e m e n t

Targets

Range - accuracy

Range Rate ( re lat ive) -accuracy

Field of V iew

Elevat ion Az imu th t r ack ing

Update rate latency l i fe* size weight DC Power

Range Range Rate

• 15 mph

Al l l i censed veh ic les

100m _+ 1.5% or_+ 1 m

Up to 100 mph + 10% or + .25 mlsec

2m for < 10m + 5.7 ° for 10 - 100m nla for • lOOm

1.5 to 2m su f f i c ien t fo r t ra jec tory

60 meec <100 msec 10 years and 120 K mi les 120 cu in 5 Ibs. 40 wa t t s

FIG. 9. Key technical requirements.

20 R. Dixit

Automated factory assembly, using self aligning techniques has been proposed, and now needs to be demonstrated for automotive assembly tolerances. Sensor diagnostics and alignment during the vehicle life also need to be addressed, before such products can be commercially viable. Ultimately, to be successful products they must provide robust performance in a complex roadway environment. Inconveniences caused by dropped tracks and nuisance alarms will not be tolerated by consumers, and would likely result in the rejection of these new technologies in the market place.

VI. Cost and Human Factors

Automotive radars face a very daunting cost target, given the requirement to provide robust performance in a complex roadway (Interstate highway) environment. Typi- cally, for large volume applications a price significantly less than $100-$300 for the sensor has been discussed, but till there is an award for standard product vehicle applications, likely initial product offerings as options on luxury platforms, will not enjoy economies of scale. Companies which are able to credibly meet the automotive industry requirements, teamed with technology leaders will best be able to succeed.

VII. Summary

There is general consensus that actual large scale deployment of ITS and of in-vehicle products will not happen till there is mass market appeal and standardization. The National ITS architecture efforts are aimed at developing such constituencies and protocols. However, to meet today's requirements of reduced government spending and minimal direct involvement, means that new approaches will be required for public-private partnerships, like pay-per-use etc. The actual size of the market can be safely estimated to be in the 'billions' worldwide, but timing and deployment is depen- dent on commonality and compatible incremental add-ons. Stand alone and unique format products will have very limited or niche deployments. Consumer awareness and cost effective benefits will fuel demand for deployment and compatible protocols will allow economies of scale for manufacturers.

But the most challenging issue will be consumer acceptance of such convenience and safety features. The products thus must work robustly and do so for the life of the vehicle. The era of smart vehicles and smart roads is coming. They are called 'smart' because they have communications, navigation, computer, and/or sensors/actators systems that can provide information or assistance to operators, as well as passengers. In addition smart vehicle technologies can provide a significant increase in driver and passenger safety, as well as reduction in the number and severity of accidents.

References

(1) L. Yoshida, "ITS integration to maximize funding and technology', Traffic Technology International, Feb. 1996.

(2) K. Prynne, "Design of visual, audio and tactile interfaces for new vehicle control systems", lEE Colloquium (Diyest), E.1. Conference, Vol. 007, 1995.

Microwave and Millimeterwave Applications 21

(3) Caltrans, "Advanced Transportation Systems Program Plan", Program Plan Digest, Oct. 1995.

(4) D. M. Grimes and T. O. Jones, "Automotive radar: a brief review", Proc. IEEE. Vol. 62, No. 6, June 1974.

(5) P. Ganci, S. Potts and F. Okurowski, "A forward looking automotive radar sensor", "Proc. of the Intelligent Vehicles 1995 Symposium" Sep. 1995.

(6) S. German and R. Isermann, "Nonlinear distance and cruise control for passenger cars ~', "Proc. of the American Control Conference", Vol 5, 1995.