Design of a Two-Element Antenna Array Using Substrate Integrated Waveguide Technique

The design of a two-element antenna array using the substrate integrated waveguide (SIW) technique and operating at 10？GHz is presented. The proposed antenna array consists of two SIW phase shifter sections with two SIW slot antennas. The phase shifting is achieved by changing the position of two inductive posts inserted inside each element of the array. Numerical simulations and experimental measurements have been carried out for three differential phases between the two antenna array elements, namely, 0°, 22.5°, and 67.5°. A prototype for each differential phase has been fabricated and measured. Results have shown a fairly good agreement between theory and experiments. In fact, a reflection coefficient of better than 20？dB has been achieved around 10？GHZ. The E-plane radiation pattern has shown a beam scan between 5° and 18° and demonstrated the feasibility of designing an SIW antenna phased array. 1. Introduction The radiation patterns of many antennas such as the dipole, loop, and microstrip patch have a fairly wide beam width (low gain), making them suitable candidates for applications requiring a broad coverage area. In many applications, however, there is a need for a more focused radiation patterns (high gain), such as in point-to-point terrestrial links, satellite communications, and air-traffic radar. A more focused radiation pattern will also extend the communication range [1]. To create a more directive radiation pattern, the size of the antenna must be increased. This can be done with simple resonant antennas like the dipole and the loop, but it is usually difficult to control the side lobe levels of these antennas. Traveling-wave antennas (helical antenna, etc.) can produce higher directivity by increasing the length and number of turns of the helix. Moderate gains (10–15？dB) can be achieved by long helical antennas, but they cannot achieve very high gains, due to the impractical length required. Another antenna which can produce relatively high gain is the waveguide horn, which is an extension of an open waveguide with flared walls at the open end. Waveguide horns are particularly useful at higher frequencies (>5？GHz) where their size and weight become manageable [1]. Some aspects of the radiation pattern can be controlled by designing horns with the proper flare angle and length or by adding corrugations to the inner walls. Another choice for achieving higher gain is to use a reflector (parabolic dish, etc.) to focus the energy of a low gain antenna. Reflector antennas offer very good electrical performance, but require careful