A Low-profile Active Phased Array Antenna System for Mobile Direct Broadcasting Satellite Reception

1. Introduction A direct broadcasting satellite(DBS) service via Koreasat 3 is currently provided and there are many subscribes for a residential house. In addition, many people want to watch the DBS TV even at vehicles because it has advantages over terrestrial TV broadcasting with high quality, simultaneity, wide coverage, and so on. Several antenna systems for mobile DBS reception have been developed on the basis of various flat antennas mounted on vehicle's roofs[1,2,3]. The most attractive of these is an active phased array antenna technology. However, the conventional technology is very expensive, restricting its use in commercial products. To solve this, a modification in the phased array antenna is introduced using twelve active array elements for cost-effectiveness[4,5]. The system shows a high performance for receiving DBS, but is still expensive, large and tall to be installed on a car due to low element gain and the connection loss between the radiator subarray and the active channel block (ACB). Therefore, we have made a great effort to develop high efficiency radiator subarray[6], and have realized a small and low-profile active phased array antenna system mountable on a small car[7]. This paper describes the design of the active array antenna system and also presents experimental results. Section 2 describes the design of the 3x4 circularly polarized subarray with the corner-truncated square patch fed by a microstrip line and the stacked patch. Section 3 describes the design of the ACB using the low cost-packaged monolithic microwave integrated circuit (MMIC) phase shifter and presents the performance of the active array module, in which the antenna elements and the active circuitry are integrated on the same substrate. Section 4 describes satellite tracking algorithm for mobile DBS reception and presents test results.