Summary
International Symposium on Antennas and Propagation
2010
Session Number:4FD4
Session:
Number:4FD4-1
M-shaped dielectric phase shifter for a base station antenna
Kengo Nishimoto, Takeshi Oshima, Toru Fukasawa, Hiroaki Miyashita, Yoshihiko Konishi, Manabu Kurihara, Yoshiyuki Chatani,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
In a base station antenna for cellular mobile radios, the beam direction needs to be tilted from a horizontal plane because it communicates with mobile terminals below. To control the tilt angle electrically, the phase shifter which changes the excitation phase of each antenna element is used. Since PIM ( Passive Intermodulation ) has to be suppressed in a base station antenna, it is desirable that a phase shifter has no contact structure between metallic components. Also, the electrically-controlled phase shifter using semiconductor chips is inappropriate owing to low power handling capability and high cost. There are some reports on mechanically-controlled phase shifters. The trombone line phase shifter with coupled lines can control the phase shift by changing the length of the coupled lines[1]. In [2], the phase shift is controlled by using a revolving structure. In [3], the phase shift is controlled by moving a dielectric plate over meander lines, and impedance matching is realized by connecting a triplate line to a microstrip line. Since these phase shifters have no metallic rubbing parts, PIM characteristics are good. However, the phase shifter in [1] needs high precision about the distance between the coupled lines. Also, the size of the phase shifter in [2] is large, and the configuration in [3] is a little complicated. In this paper, a novel, simple and small phase shifter is proposed. This phase shifter has no contact structure between metallic components, and the phase shift can be controlled by inserting a M-shaped dielectric plate into a stripline. A design equation is derived from the condition that the reflection coefficient = 0 at a center frequency. Also, the relationship between the phase shift and the moving distance of the dielectric plate is linear. These characteristics are verified by simulations and measurements.