對IEEE 802.11a 無線網路電路中諧波幅射產生原因及降低其干擾之研究

PRACTICAL TECHNIQUES TO SUPPRESS HARMONIC EMISSION IN AN IEEE 802.11A WLAN CIRCUIT

廖俊淵(Chun-Yuan Liaw)

指導教授 ： 張知難

大同大學/電機資訊學院/通訊工程研究所/碩士(2006年)

摘要

摘要
本論文為一個案例研究，應用一些電路區塊驗證法及近場掃描定位法來找出電磁干擾源，再依照問題的現象分析予以有效的對策，再加以驗証是否為有效對策；最後再以遠場量測確認。
首先了解產品的特性及用途，再了解問題發生點及現象後而做特性評估，此案例是在3倍諧波超出法規限制值1.65dB。
電路區塊驗證法：了解各個區塊的電路特性、再依問題的現象做依據，再將這些特性歸納整理後，找出可能發生的原因。依序的可能發生的問題點以測量及記錄的方式做為驗證的依據。
近場掃描定位法：以近場掃描量測找出雜訊源的所在位置，以鐵罩焊接的方式將雜訊源隔離後，原本3倍諧波最差的部分都已經改善。最後再以遠場量測的驗証部分，在原本3倍諧波最差的部分已經改善，而且低於限制值5.05dB，改善了6.7dB。

關鍵字

15GHz ； 無線網路 ； IEEE 802.11a ； 電磁扞擾

並列摘要

Abstract— In this thesis, a case study relating to the third order harmonic emission from an IEEE 802.11a WLAN card is investigated. The WLAN card contains many circuit subsystems. Among them, the transceiver block, the filter block, the power amplifier block and the diplexer block are the main block under study. We carefully investigate electric performances of each block to understand if the harmonic emission may come from these blocks. In this test, each block is detached from the mainboard. We found that harmonic emission exists even through each block is individually well functioned.
In addition to the block test, we also use the near field scan method to locate the nearest possible spots which may cause the harmonic emission. We found that this method is an efficient way. In our case, the emission is determined to come from the PA block as it contributes the highest radiation intensity by way of this near field test. After locating the source of emission, we can prevent them by way of shielding.

並列關鍵字

EMI ； 3rd Harmonic ； Harmonic ； Pre-amplifire ； PA ； amplifier ； 15GHz ； EMI ； WLAN ； Hyper LAN ； IEEE 802.11a ； near field ； far field ； probe

參考文獻

[1] IEEE STD 802.11 -1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications.

[6] Atheros Regulatory Compliance Guide, Revision March 2003.

REFERENCE

[2] IEEE STD 802.11a -1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band.

[3] IEEE STD 802.11b -1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band.