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Héctor Carrasco E.2
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2
RESUMEN
En este trabajo se presentan resultados experimentales de medición de canal y evaluación de capacidad MIMO (Multiple Input Multiple Output) de arrays de antenas PIFA (Planar Inverted "F" Antenna) compactos en la banda de frecuencia de 2.45 GHz, en entornos interiores ricos en multitrayecto. Se evalúan dos configuraciones básicas de arrays, Lineal y Cuadrada de cuatro antenas PIFA, cuyas características de bajo perfil y grados de libertad de construcción y configuración constituyen ventajas comparativas para aplicaciones con terminales compactos potables. Las mediciones de la matriz de canal MIMO se hacen utilizando un VNA (Vector Network Analyzer) controlado vía estándar GPIB (General Purpose Interface Bus). La capacidad MIMO se evalúa estadísticamente para un gran número de medidas del canal, en espacio y frecuencia, con separación de antenas en cada array de 0,1 a 0,8 longitudes de onda, con el objetivo principal de estudiar el efecto del acoplamiento mutuo en la capacidad MIMO. Los resultados de capacidad medida muestran que las configuraciones propuestas más eficientes pueden operar como mínimo hasta separaciones de antenas en el rango de 0,3 a 0,4 longitudes de onda, sin producir gran degradación de capacidad debido al acoplamiento y bloqueo de señal. Este resultado implica separaciones cercanas a 4 cm y, en consecuencia, arrays significativamente compactos.
Palabras clave: Medición de matriz de canal MIMO, capacidad de canal MIMO, antenas PIFA, acoplamiento mutuo, arrays de antenas.
ABSTRACT
This paper presents experimental results of indoor MIMO wireless channel and channel capacity evaluation for compact PIFA (Planar Inverted "F" Antenna) antenna arrays at the 2.45 GHz frequency band. Linear and square array configurations are evaluated using PIFA antenna elements because of its advantages of low profile and flexible configuration design for compact and portable mobile terminals. Measurements are performed using a VNA with GPIB standard for automatic data acquisition. MIMO channel capacity results are calculated from a large amount of data combining uncorrelated space and frequency measurements, obtaining results that are statistically representative. Antenna array size from 0.1 to 0.8 wavelengths are tested to evaluate the effect of mutual coupling. Results show that the most efficient configurations can provide high capacity for array size as small as 0.3 to 0.4 wavelengths, which is a significant compact array size for portable wireless terminals (about 4 centimeters for the tested frequency).
Keywords: MIMO channel matrix measurement, MIMO channel capacity, PIFA antennas, mutual coupling, antenna arrays.
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