Series-Fed Monopulse Microstrip Array Antenna With Stripline Quadrature Hybrid Comparator Network

Le Zou,Xuetian Wang,Jiawei Zang

doi:10.1109/access.2021.3138698

Abstract

Microstrip series-fed weighted arrays have widespread applications in millimeter wave (MMW) radar due to their low profile and light weight. Our study proposes a novel Ka-band compact monopulse radar antenna design with a highly directional 2D series-fed microstrip array antenna. The structure is composed of a symmetrical four quadrant radiation array and an innovative stripline monopulse comparator with two segments. Our novel design applies the stripline in the back-end which considerably reduces the antenna’s backward radiation. The shaped patterns in the E and H planes are achieved by tapering patch widths and adjusting the impedance transformer of each subarray. Four half power quadrature hybrids are combined to form 2D monopulse feeding in the back-end. Both parts adopt a simple symmetrical layout that simplifies the design process. The measured reflection coefficients of each port are lower than -10 dB across 34.5 GHz to 35.5 GHz working band meanwhile isolation between these ports are better than 25 dB. Furthermore, the first side lobe level (FSLL) in the sum beam, which is remarkably suppressed by Taylor synthesis design method, achieves about -24 dB both in E and H planes. The measured gain of the sum pattern achieves 25.3 dBi at 35 GHz center frequency, while the nulling depth of the difference patterns in both planes are lower than -30 dB.

Highlights

The millimeter wave (MMW) band has many intrinsic advantages in developing small-scale or portable radar equipment
Array antenna structures based on printed circuit boards (PCB) have the special characteristics of a low profile and light weight, which makes them more suitable in MMW scenarios than earlier metal designs such as four quadrant horn arrays with reflectors, and waveguide slot arrays [7], [8]
TAYLOR SYNTHESIS This antenna is designed for application as a ground-based monopulse radar for airspace detection purpose, where the abilities of anti-interference in the near ground clutter environments and distinguishing the false targets are strongly needed

Summary

INTRODUCTION

The millimeter wave (MMW) band has many intrinsic advantages in developing small-scale or portable radar equipment. In [19], six series-fed microstrip linear subarrays with tapered patch width distribution and a single-end connecting SIW parallel feed network were used to form shaped patterns in azimuth and elevation cut planes. The compact stripline feeding layout in our design has the four series feed planar arrays located at four quadrants in xoy plane that are fed through four metallized vias close to the center of board This realizes the specific excitation distributions with a maximum amplitude at the center of the four-quadrant array. The design’s ideal FSLL, front to back ratio (FBR), and null depth in its E/H plane sum and difference patterns are obtained across 34.5 GHz to 35.5 GHz working band This design performance was verified by highly consistent simulated and measured results. Since the cosθ factor is included in H plane patterns as exhibited in (2) and (4), the amplitude in H plane decays more rapidly along with the deviation from the increasing 0° direction compared with the E plane and obtains null at the end-fire direction

ANTENNA SIMULATION DESIGN

ANTENNA FABRICATION AND MEASUREMENT

MEASUREMENT RESULT AND DISCUSSION

CONCLUSION