Three GHz frequency modulated continuous wave and doppler radar with switched beam

In this project our main aim was to design and implement the FMCW and Doppler compact radar. As name depicts that this project has operating mode FMCW is used for distance measurement and Doppler radar is used to measure the velocity of an object. This FMCW radar is designed for 3GHz with 100MHz ban

Project Title

Three GHz frequency modulated continuous wave and doppler radar with switched beam

Project Area of Specialization

Internet of Things

Project Summary

In this project our main aim was to design and implement the FMCW and Doppler compact radar. As name depicts that this project has operating mode FMCW is used for distance measurement and Doppler radar is used to measure the velocity of an object. This FMCW radar is designed for 3GHz with 100MHz bandwidth. Range resolution has also improved i.e. smaller objects up to 1.5m can be detected. Phased array antenna is used to switch the beam at different angle in elevation plane. It has a wide application in the era of autonomous vehicle system, range and velocity measurement and aviation safety etc. To complete our system design we divide our project in two subcategories. Simulations tool used for this project is High Frequency Structural Simulator (HFSS), Advanced Design System (ADS) and MATLAB. HFSS software is one of the most advanced 3D EM software that is used for PCB Design of Antenna. ADS is used for co-simulation of RF circuit of radar and antenna. MATLAB is used for the comparison in simulated results and graphics. For the sake of compactness, we emphasized to select the SMD components and complete RF circuit for our project was implemented on PCB Sheet named Rogers RO4350B. For testing and measurements are under processed.

Project Objectives

The main goal of our project that we wish to design and implement of FMCW and Doppler radar. It has a wide application in the era of autonomous vehicle system, range and velocity measurement and aviation safety etc. To complete our system design we divide our project in two subcategories.

• Design and implementation of RF circuit for Radar
• Design and implementation of Antenna Array for transmission and reception

Design and implementation of RF circuit for radar

There are two modes in our implemented design i.e. FMCW mode and Doppler mode. Doppler Radar or Continuous Wave (CW) radar transmitting an unmodulated power can measure the speed only by using the Doppler-effect. It cannot measure a range. So for range measurement FMCW radar is used in which frequency modulated signal is transmitted continuously and differences in frequency between the actually transmitted and the received signal is measured which gives the information of range of object from the radar. The RF circuit for both modes is same but only difference is type of input voltage need to feed the voltage controlled oscillator (VCO). RF circuit was designed in Advanced Design System (ADS) and implemented on PCB Sheet material Rogers RO4350B using SMD components for the sake of compactness.   

Design and implementation of antenna array for transmission and reception

Polarization of echo signal should be same as the polarization of receiving antenna but due to reflection, scattering and multipath effect polarization of echo signal may be changed so to cope with this problem a dual circular polarized antenna array has been designed in software HFSS and implemented on PCB sheet material Rogers RO4350B. Phased array antenna was suggested to switch the beam in different direction so there is no need to physically move the radar. Providing the progressing phase shift with the help of phase shifter between the elements of antenna array we can steer the beam in different direction.

Project Implementation Method

RF circuit for proposed radar is designed in Advanced Design System (ADS) and has been fabricated on PCB sheet material Roger RC430B using LPKF CNC machine. In our prototype "SMD RF components" are used for the sake of compactness. All components are shipped form manufacture named mini circuits USA. In the process of fabrication, precautions are adopted during soldering of SMD components as they are very sensitive due to static charges. For transmission and reception 2x2 patch antenna array is designed in High-Frequency Structure Simulator (HFSS) and has been fabricated on the same sheet i.e. Roger RC 430B using LPKF CNC machine. Testing and measurements are under process. We have university collaboration with “Research Center for Microwave and Millimeter Wave Studies” (RIMMS) at NUST Islamabad. Vector Network Analyzer is used to measure and analyze signal behavior of S-parameters. The signal behavior can be observed return loss, VSWR, reflection coefficient etc. Antenna gain, directivity and polarization measurement are performed in anechoic chamber. Both transmitting and receiving antenna are kept at some distance so that there should be no leakage of signal from transmitter to receiver directly. Digital Spectrum Analyzer is used for testing and measurement of range and velocity for different targets.

Benefits of the Project

This project has wide applications in the era of communications. From the Microwave RF Antenna point of view a novel idea has been implemented for the polarization diversity. In our implemented radar there is no need to physically move the radar as beam will move or switch in different direction with the help of phase shifters. Focus on polarization diversity for good reception of echo signal by implementing dual polarized antenna array. Proposed radar is compact as SMD components were used and power efficient as it requires only 0.6W input power to measure range up to 70 meters. This project has wide applications such as

• in automobile
• for level detection in storage tank
• in defense industries for target detection
• in speed locking on motorways
• for object detection in NO GO AREA.
• ground penetrating radar for mines detection
• radar speed gun for speed measurement on motorways
• short range radar in IOT and Embedded design 

Technical Details of Final Deliverable

Proposed radar configuration has capability to measure the range and velocity of target in two operating modes i.e. FMCW and Doppler mode. Block diagram of our project is shown in figure below. RF circuit is same for both modes except the type of input voltage which is different for both modes. In FMCW mode an input voltage is ramp function (Vmax = 3volts and Time Period = 100 usec) whereas a constant voltage (Voltage = 4 volts) is provided in Doppler mode. In both modes this input voltage is fed to the Voltage Controlled Oscillator (Model # ZX95-3250-S+, Pout = 3dBm, Frequency Range = 2.8 -3.2 GHz and Tuning Sensitivity (MHz/V) = 50 MHz) which generates the oscillation depending upon the input voltage. In case of Doppler radar mode, a signal of single frequency will generate and a linearly increasing frequency signal having a certain bandwidth. This signal is fed to the power amplifier (Model # PSA4-5043+, Gain = 10dB and Frequency Range = 0.05-4 GHz 1dB Compression Point =18.8 dBm) to amplify the signal. Amplified signal is then divided using 3dB-power divider (Model # SCN-2-35+, Frequency Range = 2.8-3.7 GHz and Isolation 22dB) for two paths one for frequency mixer as a reference signal and other for transmission in free space through antenna. On the receiver side, receiving antenna is connected with the Band Pass Filter (Model # BFCN-3085A+, Pass Band = 2.8-3.4 GHz) in order to reject the unwanted frequency signal. Low Noise Amplifier (Model # PSA4-5043+, Gain = 10dB and Frequency Range = 0.05-4 GHz and NF = 0.75dB) is added in RF circuit to amplify the echo signal which suffers the attenuation due to free space path losses. To take difference between the reference signal and echo signal frequency mixer (Model # ADE-R30WLH+, LO level = 10dBm, 1dB Compression Point =5dBm) is used and latterly Low Pass Filter (Model # LFCN-95, Pass Band DC-95 MHz) is added to reject the sum of two signal which also appear on the IF port of mixer. Frequency difference in case of FMCW mode is termed as beat frequency fb.                                                                            

fb= kf × {(2×R) ÷2}                                              (1)

where kf is called modulation constant (Kf = 1000 M) it is clear by (1) that Range directly relates with the fb. In case of Doppler mode difference in frequency is called Doppler shift in transmitted frequency ft i.e. (ft ± fd) due to moving object which relates as                                   

fd = (2 × Vr) ÷ ?                                                    (2)

On antenna side a novel idea has been implemented for the polarization diversity. Phased array antenna is used to move or switch the beam in different direction with the help of phase shifter so there is no need to physically move the radar. Providing the progressing phase shift with the help of phase shifter between the elements of antenna array we can steer the beam using (3).       

? = -?d × cos?                                                    (3)

Block Diagram:

Transmitted Power

28 dBm

Operating Frequency

3-GHz

System (Antenna) Bandwidth

80 MHz

Input Ramp Voltage Time Period (for FMCW)

100 usec

Max Range

70 meters

Receiver Sensitivity

 -91 dBm

Antenna Gain

 8.5 dBi

Axial Ratio Beam width

 40 Degree

Final Deliverable of the Project

Hardware System

Type of Industry

Telecommunication

Technologies

Others

Sustainable Development Goals

Industry, Innovation and Infrastructure

Required Resources

If you need this project, please contact me on contact@adikhanofficial.com