Investigation On The Compact GNSS Antenna Arrays

The signals from Global Navigation Satellite System (GNSS) satellites are so weak that theyare easy to be disturbed. Adaptive nulling antenna is one of the most important anti-jammingtechnologies. Using conventional antenna arrangement, the array element number is difficult to beincreased on such small platforms as aircraft, missiles and others. Therefore, it constrains theimprovement of the anti-jamming ability. Smaller element spacing than half-wavelength canreduce the size of array greatly. But the strong mutual coupling between antenna elements incompact array degrades system performance seriously. Consequently, the investigation on compactarray has important theoretical and practical meaning.Focusing on the adaptive antenna and miniaturization technology, the research works in thispaper are presented as follows:1. The amplitude and phase imbalance of radiation pattern in two different antennaarrangements is investigated. A7-element array is designed and fabricated for a GPS/GLONASSadaptive nulling system. The experimental results show that the antenna system suppressesinterference obviously as expected.2. Three correction methods of adaptive weights based on the mutual coupling compensationtechnology in minimized array are studied. When the element spacing is reduced, the strongmutual coupling effect changes the position and depth of nulls. It is necessary to compensate forthe mutual coupling in digital signal processing. Open-circuit voltage method, receiving mutualimpedance method and active radiation pattern method are studied and compared. The simulationresults show that the precision of receiving mutual impedance method is more accurate thanopen-circuit voltage method while active radiation pattern method is suitable for more situations.3. The decoupling network technologies in compact array are discussed. Based on theorthogonal eigen-modes, the equivalent receiving circuit model is introduced and the reason whyweight-correction can’t improve the SNR is analyzed. Two kinds of decoupling networks arestudied respectively by the impedance and scattering matrix respectively. The simulation resultsshow that the isolation of feeding ports is improved greatly by introducing the decoupling network4. The array antenna design method loaded by dielectric lens is studied. The phase relation indielectric lens is analyzed. A compact array with low mutual coupling characteristics is designed.