為提升便利性，現代行動裝置通常須搭載數種無線通訊系統，例如蜂巢通訊、無線區域網路 (WLAN或Wi-Fi)、藍芽 (Bluetooth；BT) 系統等，然而，當這些共存系統同時運作時，可能造成相互干擾以及頻帶外（out-of-band；OOB）干擾的問題。在本論文中，我們探討BT暨Wi-Fi共存系統中，BT傳送端訊號洩漏至Wi-Fi傳送端所造成的OOB干擾問題，以及對應的抑制方法。首先，我們分析OOB干擾訊號的產生過程，並利用適應性正規化最小均方（normalized least-mean-squared; NLMS）演算法加以抑制；此方法雖可達到不錯的OOB干擾抑制效果，但亦會衰減Wi-Fi傳送訊號。為降低此一Wi-Fi訊號衰減效應，我們接著發展一種修正式NLMS演算法，再加上一個Wi-Fi回授訊號估測器以提升OOB干擾抑制效能。另外，我們進一步修正上述適應性演算法結構，以在I/Q不平衡的情況下，能夠有效抑制OOB干擾，但不致於對Wi-Fi傳送訊號有明顯的影響；為了降低演算法的複雜度，我們更發展了一種基於修正式NLMS演算法的抗I/Q不平衡方法。電腦模擬結果顯示，我們所提出之OOB干擾抑制方法在完美I/Q平衡的情況下可達到36.39 dB的效能增益，而在10%振幅不匹配及10度相位不匹配之I/Q不平衡的情況下，則可達到36.19 dB的效能增益。

To increase convenience for users, modern mobile devices often are equipped with multiple wireless communication systems, such as cellular, Wi-Fi, and Bluetooth (BT) systems. One major problem associated with such in-device coexistence is that out-of-band (OOB) interference can occur when two coexistent systems operate simultaneously. In this dissertation, we investigate the OOB interference issue in coexistent Wi-Fi and BT systems, especially the interference caused by leakage of the signal from the BT transmitter (Tx) to the Wi-Fi Tx, and the methods used to suppress the OOB interference. First, we analyze how the OOB interference signal is generated and then apply an adaptive normalized least-mean-squared (NLMS) algorithm to suppress it. This scheme can provide good performance in suppressing the OOB interference, but it can also degrade the Wi-Fi transmit signal concurrently. To alleviate degradation of the Wi-Fi signal, we develop a modified-NLMS algorithm and combine it with a Wi-Fi feedback signal estimator to form an improved OOB interference suppression scheme. Also, we modify the above adaptive scheme so that it can effectively suppress the OOB interference without significantly degrading the Wi-Fi transmit signal under in-phase and quadrature (I/Q) imbalance. We also propose an alternative anti-I/Q imbalance scheme based on the modified-NLMS algorithm to reduce complexity. Computer simulation results demonstrate that the proposed adaptive OOB interference suppression schemes can provide performance gains up to 36.39 dB under perfect I/Q balance, and up to 36.19 dB under I/Q imbalance with 10% amplitude mismatch and 10-degree phase mismatch.

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