No abstract

No abstract

<p class="Default">In this paper, a novel design for single-layer half width microstrip leakywave antenna (HW-MLWA) is demonstrated. This model can be digitally control its radiation pattern at operation frequency and uses only two values of the bias voltage, with better impedance matching and insignificant gain variation. The scanning and controlling the radiation pattern of leaky-wave antennas (LWA) in steps at an operation frequency, by using switches PIN diodes, is investigated and a novel HW-MLWA is introduced. A control cell reconfigurable, that can be switched between two states, is the basic element of the antenna. The periodic LWA is molded by identical control cells where as a control radiation pattern is developed by combining numerous reconfigurable control cells. A gap capacitor is independently connected or disconnected in every unit cell by using a PIN diode switch to achieve fixedfrequency control radiation pattern scanning. The profile reactance at the free edge of (HW-MLWA) and thus the main lobe direction is altered by changing the states of the control cell. The antenna presented in this paper, can scan main beam between 18o to 44o at fixed frequency of 4.2 GHz with measured peak gain of 12.29 dBi.</p>

An important issue in wireless communication systems, which is related to the antenna gain degradation in case of changing the main direction of the antenna radiation pattern, this variation is not approval in many communications systems. In order to improve antenna radiation performances, Electromagnetic band gap (EBG) - antenna with radiation pattern control capability is presented. Mushroom-like EBG structure for suppressing surface waves has been combined, with the switching diode to produce the radiation pattern control with improving antenna characteristics of gain, directivity and efficiency. EBG of several cells are surrounded the patch antenna and placed symmetrically for the two opposite sides, generating different radiation patterns control ability in both the elevation (E) (-20° &lt; φ &lt; 20°) and azimuth (Z) planes (−18° &lt; θ &lt; 18°). At the ground plane of antenna the diodes have been switched ON and OFF states, the EBG sector properties in stop band (connecting vias) and pass band (disconnecting vias) are altered. Using CST Microwave Studio (CST MWS) the results show the flexibility in radiation pattern control for the Z and E planes using only four diodes. Antenna directivity of 10 dBi, gain 9.86 dB and efficiency 96.5% at the operating frequency of 6 GHz, more results for all direction has been stated in Table1. Significantly, unlike a conventional beam steering, this method does not suffering from gain degradation and the main lobe gain is approximately constant for all steerig angles.

This paper presents a new technique to enhance impedance bandwidth of single layer half width microstrip leaky wave antenna (HW-MLWA) with continuous main beam scanning. The enhancement is realized by etching four circular slots on the radiation element. Two of the circular slots are placed close to the feed port, and the others are close to the matching load. The wide main beam scanning is between +12 • and +70 • when operation frequency sweeps between 4.3 GHz and 6.5 GHz. A comparison between the Uniform HW-MLWA (reference) and the proposed HW-MLWA with circular slots is provided to study the effectiveness of the added circular slots. The proposed HW-MLWA is fabricated and tested. The measured impedance bandwidth is 49.9% (4.28 GHz to 7.13 GHz) with peak gain 10.31 dBi at 5 GHz, hence the proposed antenna can be considered as a suitable candidate for C-band applications.