Monopulse tracker is a system that uses the sum and difference radiation patterns to track. If there is a target in the beam, the tracker receives an echo from it following each transmitted pulse. The target range or distance is readily determined by multiplying half the time delay between the transmitted and received pulses by the speed of light. Typically, the sum and difference patterns are obtained by adding and subtracting individual beam patterns electronically or using RF components, such as: hybrid junctions, directional couplers. However, RF components are frequency dependent. Once they are used to realize the sum pattern at one frequency, they cannot be used to realize the difference pattern at another frequency. Hence, the objective of this work is to create a dual-band phased-array antenna with Composite Right/Left-Handed (CRLH) transmission lines to obtain the sum and difference patterns directly and passively.
In order to realize the sum and difference patterns directly on a single physical board, the amplitude distribution of an 8 isotropic linear antenna array is designed using the Dolph-Tchebycheff antenna synthesis technique. By exciting all the antenna elements in-phase, the sum pattern is generated; exciting one half of the antenna array out-of-phase (180o phase difference) with respect to the other half, the difference pattern is released. For hardware implementation, a dual-band Wilkinson power divider has been designed for in-phase output at 2.5 GHz and a phase difference of 180o at 1.8 GHz by injecting a CRLH unit cell in one of the output arms. In addition, microstrip power dividers are designed to implement the amplitude distribution. These are incorporated with dual-band microstrip antennas to obtain the sum and difference patterns.
While the amplitude distribution of an 8 isotropic linear array are computed using MATLAB, hardware design optimization and simulation have been done using ANSYS HFSS. A CRLH unit cell, inspired by available research in the literature, has been designed and implemented in one of the output arms of a conventional Wilkinson power divider resulting an output of 180o phase difference at 1.8 GHz and 0o phase difference at 2.6 GHz. This Dual-Band CRLH Wilkinson power divider has been fabricated and validated using Network Analyzer. The difference pattern has been designed with a side lobe level (SLL) of -30 dB. This results a SLL of -12 dB for the sum pattern. In addition, the sum and difference patterns are theoretically generated with MATLAB to verify the designed SLL. Furthermore, four different microstrip power dividers have been designed to split the power properly between antenna elements based on the computed amplitude distribution. Dual-band microstrip antennas operating at 1.8 GHz and 2.6 GHz are designed and equally spaced out at a distance d = λ/2 to avoid the mutual coupling. The design is modeled and simulated in HFSS and for the Rogers RT/duroid substrate with a dielectric constant of 2.2 and the thickness of 31 mil. All the necessary measurements to validate the design can be done using the Network Analyzer and anechoic chamber.
Library of Congress Subject Headings
Antenna arrays--Design and construction; Monopulse radar; Passive components
Electrical Engineering (MS)
Department, Program, or Center
Electrical Engineering (KGCOE)
Gill R Tsouri
Le, Vu James, "All-Passive Composite Right/Left-Handed (CRLH) Antenna Array for Sum and Difference Patterns" (2020). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus