1. Applications of radar systems in collision avoidance
Presented By:
Aishwarya Bhatnagar

2. Why collision avoidance is a necessity?
According to road safety facts provided by W.H.O[1(b)]:
Globally, nearly 1.3 million people die in road crashes each year, on average 3,287 deaths a day.
Additionally, million are injured or disabled.
Road traffic crashes rank as the 9th leading cause of death and account for 2.2% of all deaths globally.
Road crashes cost USD $518 billion globally, costing individual countries from 1-2% of their annual GDP.
Unless action is taken, road traffic injuries are predicted to become the fifth leading cause of death by 2030.

3. Introduction to FMCW radar systems
FMCW(Frequency Modulated Continuous Wave) radar.
Electromagnetic(RF) signal from these radars is continuously transmitted(differ from pulsed radar systems).
As a result ,the time of flight to a reflecting object cannot be measured directly by these systems.
RF signal transmitted by these radars is swept linearly in frequency.
Range = c T / 2
How can we determine range when there is no starting point(t₀)?

4. Working principle of FMCW radars
The frequency of the RF signal changes over time in a sweep across a set bandwidth.
The difference in frequency between the transmitted and received(reflected) signal is determined by mixing the two signals.
The new signal can be measured to determine the range and velocity of the target.
Fig 1(a) Block diagram of FMCW radar[2a]
Fig 1(b) Extracting beat frequency and converting it into range[2b]

5. Advantages of FMCW radar for short range detection
Zero blind range(Can detect targets at all ranges within maximum specified range) due to separate Tx and Rx antennas.
The sampling frequency needs to be greater than twice the maximum beat frequency(fs > 2fb) which relaxes the capacity of A/D converter.
Consume less power, since the radar is transmitting continuously, peak transmit power is equal to the average transmit power.

6. Simulating a forward collision mitigating FWCW radar
Project Objectives:
Applying FMCW radar concepts to simulate an artificial scenario wherein the radar accurately measures the range and velocity of two point targets:
Pedestrian
Vehicle
Radar distinguishes the two targets on the basis of their RCS.
Fig 2(a) radar detecting an on road pedestrian[3]
Fig 2(b) radar detecting a nearby vehicle[3]

7. Overview of the simulation scenario
The FMCW signal(Chirp) is generated by the waveform generator.
The transmitting antenna amplifies the signal and radiates it to free space.
Signal propagates into free space towards the target ,gets reflected and travels back to the radar.
Reflected signal is collected by the receiving antenna.
Received signal is mixed with the transmitted signal(dechirping) and saved in a buffer
Once the required number of sweeps fill the buffer ,FFT is performed to extract Range and Doppler corresponding to the target.

8. Project design considerations
Radar Centre Frequency:77GHz
Propagation: Free space
Maximum range monitored:150m
Range resolution ∆R:1 m
Operating Bandwidth B=c/2 ∆R :150MHz
RCS of the 2 targets:
Targets
RCS(m2)
RCS(dB)
Pedestrian 1
Vehicle
100 20
[4]

9. Project design considerations
Generating a sample chirp(transmitted signal).
Simulating two received chirp signals delayed by 1 and 0.2 micro seconds.
Calculating received powers for two targets(Radar range equation)
Adding receiver noise(kT0BF) and background noise to the received superimposed signal
Calculating range from this time delay: we should  get 30 m and 150 m by extracting it from beat frequency. 9

10. Signal processing :FMCW radar
Fig 3. A 2-Dimensional FFT performed to extract Range and Doppler frequency of the two targets[5]

11. Simulation results
Transmitted chirp signal

12. Simulation results
fb1: (pedestrian)
fb2:(vehicle)​ 12

13. Range calculation simulation results
Range:30m
Range 150m

14. References
[1a]
[1b]
[2a]
[2b]
[3]
[4]
[5]
Eugin Hyun , Jonghun Lee, Moving Target Range Detection Algorithm for FMCW Radar, Radar Symposium (IRS), th International, Issue Date: June 2013.
Florian Fölster, Hermann Rohling, Urs Lübbert, An automotive radar network based on 77 GHz FMCW sensors, Radar Conference, 2005 IEEE International