Bradley Natarian

Advisor: Prof. Rick Blum

Implementation of Passive Radar with a

Software Defined Radio Platform

Acknowledgement(s):

Jacob A. Gilbert and Jack L. Burbank – Johns Hopkins Applied Physics Laboratory

John W. Franklin – University of North Texas

Mark A. Richards – Georgia Tech

David and Lorraine Freed Undergraduate Research Symposium, Lehigh University

Electrical and Computer Engineering

Lehigh University, Bethlehem, PA

Passive radar:

• Uses the reflected energy of electromagnetic

waves from third-party sources (illuminators of

opportunity) to detect and track targets

• Does not require a transmitter

• Advantages compared to traditional radar systems

• Cost effective

• Can be used for covert operations

• Difficult to jam

Definitions

Software Defined Radio (SDR):

A radio system comprised of:

• Wideband, software independent

hardware

• Signal processing executed on a general

purpose processor

• Can be used to explore a wide band of

frequencies

Approach

A single SDR passive radar receiver will be

simulated and implemented to prove that it can

detect the time of flight from an illuminator to a

target to the receiver.

• Electromagnetic waves are transmitted from an illuminator of opportunity

• These transmissions are received via two paths

• A direct path from the illuminator to the direct path receiver with known distance, 𝐷• A reflected path from the illuminator to the target to the reflected path receiver with unknown

distance, 𝑅𝐼 + 𝑅𝑅• The transmitted signal can be recovered by subtracting the delay, 𝑡𝐷,from the received signal,

𝑆𝐷 𝑡 − 𝑡𝐷 , to obtain the transmitted signal, 𝑆𝐷(𝑡)• The time of flight of the reflected path, (𝑡𝐼 + 𝑡𝑅), can be calculated with a matched filter

• Time of flight can then be used to calculate the total distance from the illuminator to the target to

the receivers, 𝑅𝐼 + 𝑅𝑅

Principles of Operation

• Use three receivers to triangulate the

position of the target relative to the

illuminator and receivers

• Build a working prototype of the

concepts described in this work

using software (e.g. GNURadio,

MATLAB) and SDR hardware (e.g.

RTL-SDR, USRP)

Future Implementations

Block diagram of the SDR hardware

𝑡𝐷 =𝐷

𝑐

𝑡𝐼 - time delay from illuminator to target

𝑡𝑅 - time delay from target to receiver

𝑡𝐷 - time delay of direct path

𝑅𝐼 - distance between illuminator and

target

𝑅𝑅 - distance between target and

receivers

𝐷 - distance between illuminator and

receivers

𝑐 - velocity of the transmitted wave

Objective

To demonstrate radar capabilities with a

software defined radio platform

Flow chart of passive radar signal processing

Full System Implementation Matched Filter Simulation

Matched Filter Theory

Single Path Prototype

𝑀 𝑡 = 0

𝑇

𝑆𝐷 𝑡 𝑆𝑅 𝑡 − 𝑡𝑑 𝑑𝑡

max 𝑀 𝑡 = 𝑀(𝑡𝐼 + 𝑡𝑅)

𝑅𝐼 + 𝑅𝑅 = 𝑐(𝑡𝐼 + 𝑡𝑅)

𝑀 𝑡 - output of the matched filter

𝑆𝐷 𝑡 - direct path received signal

corrected for 𝑡𝐷𝑆𝑅 𝑡 − 𝑡𝑑 - reflected path received signal

The matched filter peaks when the signals

are most correlated.

𝑆𝐷 𝑡 = 1 Vp-p frequency sweep from 1 – 10 kHz

𝑆𝑅 𝑡 = 1

5𝑆𝐷 𝑡 − 1396 𝑚𝑠 + 𝑛

𝑛 = 10 𝑑𝐵 𝑜𝑓 𝐴𝑊𝐺𝑁

This material is based upon work

supported by the National Science

Foundation under Grant No. ECCS-

1405579.

Any opinions, findings, and conclusions or

recommendations expressed in this

material are those of the author(s) and do

not necessarily reflect the views of the

National Science Foundation.