VII Microstrip Antennas feed Microstrip antenna Advantages Printed

VII. Microstrip Antennas feed

Microstrip antenna Advantages • Printed circuit fabrication: simple and inexpensive to manufacture using modern printed-circuit technology • On same plane, feed, radiator, and networks including matching, amp, and filter can be realized • Low profile, conformable to planar and nonplanar surface • Versatile in terms of frequency, polarization, pattern, and impedance • Adaptive elements with variable resonant frequency, impedance, polarization and pattern can be designed Disadvantages • Low efficiency, low power • high Q(narrow bandwidth) • Pure polarization purity, pure scan performance

Microstrip antenna Aperture field

2 -slot model for rectangular microstrip antenna

Various shapes of microstrip antenna square patch circular patch annular ring triangular patch rectangular patch elliptical patch ring sector strip patch: dipole disc sector

Various feeding method of microstrip antenna probe feed microstrip line feed: direct feed Proximity coupled feed Aperture coupled feed

Microstrip antenna Broad side array dual

Rectangular patch 1. Transmission line model: 2 narrow radiating slots of Width W and height h, seperated by microstripline of width W and length of L fringing field

Transmission line model

cavity model Magnetic wall

Equivalent Current Solution field distribution of cavity model

Equivalent current distribution 2 current elements of the equal amplitude and phase arrayed, separated by a distance L along the y-direction All current elements on slots are odd symmetric-> radiating field from each current element is negligibly small->non-radiating slot

Radiated field

Field pattern

Circular patch cavity model

Equivalent current distribution

Radiated field: source point and field point

Radiated field

Conductance & Directivity

Quality Factor Bandwidth

Circular polarization double feeding Microstrip feed coaxial feed

Circular polarization Single feeding Microstrip feed coaxial feed

Circular polarization Single feeding Square patch with thin slot Square patch with trimmed corners elliptical patch with tab

Arrays Conformal array 10 X 10 Array for space to space communication

Arrays series array for broadside main beam S: scanning control Width of element: radiation control

Arrays 4 X 4 rectangular patch array