You can take the airport shuttle bus line 5 from Pudong airport to Shanghai Long-Distance General Bus Station at 1662, Zhongxing Road, Zhabei District (Shanghai Railway Station North Square). There you can find bus to Yixing.

If you wang to visit Yixing often in a week, I advise you to find a hotel near the bus station, such as East China Hotel which is only about 2-minutes walking distance from the bus station.