Microstrip line slot‐array antenna with reduced beam‐tilt

Abstract

Microstrip line slot‐array antennas consisting of slots placed on the ground plane on both sides of the microstrip line may be classified into resonant‐ and nonresonant‐types. Both types exhibit a beamtilt—namely, the main beam direction shifts as the operating frequency is changed away from the center frequency. This beam‐tilt causes the gain in the specified direction to degrade rapidly, which is a serious drawback in a system for receiving a signal with a given bandwidth from a fixed direction. To overcome this deficiency, a method available for waveguide slot‐array antennas is used and a design procedure is developed. Further, it is shown experimentally that beam‐tilt is almost nonexistent over a relatively broad frequency range and constant gain is obtained. The gain is higher than that of conventional antennas. Sidelobes are suppressed, especially for nonresonant arrays. The usefulness of the microstrip line slot‐array antenna with a reduced beam‐tilt is demonstrated.

Slot array antenna for wireless LANs with backward excitation

“…Hence, if mutual coupling between the slots is neglected, the equivalent circuit of the N-element slot array is as shown in Fig. 3 [10,11]. Z n is the impedance of the n-th slot, Z c and b are the characteristic impedance and phase constant of the transmission line, and jX is the reactance of the open stub.…”

“…(3) while the slot has resonant length and width. Further, the offset length O sn is set in such a way that the resonant resistance r n = Z n / Z c becomes [10] Here, n = N 1, N 2, . .…”

“…1, it has been reported that a design method neglecting the mutual coupling between the slots is effective if the main beam is oriented to the broadside or if the tilt angle is small [10,11]. However, no design method has been studied that includes the effects of mutual coupling when the beam is substantially tilted toward the endfire direction.…”

“…Antenna elements satisfying these conditions include a patch array antenna [8], a crank line antenna [9], and a microstrip line slot array antenna [10,11].…”

Cavity‐backed slot array antenna with backward excitation

“…(2) The slot spacing is determined such that the main beam is in the desired direction. (3) The offset length between the slots and the transmission line is determined such that the desired input characteristic is met [17].…”