正交分頻多工器主要是利用所有的子載波正交特性進行調變，而多載波濾波器組(Filter Bank Multicarrier, FBMC)只需要維持和相鄰子載波之間的正交特性即可。因此，為了保持多載波濾波器組系統正交特性和提高頻寬使用率，將會使用偏移正交振幅調變(Offset Quadrature Amplitude Modulation, OQAM)。有鑒於採樣濾波器的良好振幅響應和微小的旁瓣干擾，本論文將使用頻率採樣濾波器。將偏移正交振幅調變和頻率採樣濾波器組結合我們將不再需要使用循環字首進而可以得到更好的頻寬使用率。
偏移正交振幅調變(Offset Quadrature Amplitude Modulation, OQAM)會將輸入的正交振幅調變(Quadrature Amplitude Modulation, QAM)做實部和虛部分離，形成兩個新符元。分離過程中做2倍升採樣讓兩個符元錯開，之後在一個符元週期內分別以前半週期和後半週期完成傳輸。
合成濾波器組(Synthesis filter bank)和分析濾波器組(Analysis filter bank)重點在於所使用的濾波器，因為所有濾波器組都是原型濾波器(prototype filter)的平移。本論文使用頻率採樣濾波器做為原型濾波器的設計，重疊因子(overlap factor)選擇為4使得原型濾波器的長度為反離散傅立葉轉換 (Inverse Discrete Fourier Transform, IDFT)、離散傅立葉轉換 ( Discrete Fourier Transform, DFT)的4倍。論文裡使用1024點IDFT，長度為4*1024的原型濾波器做為設計規格，為了降低運算複雜度和維持IDFT/DFT大小，這裡使用多相網路完成原型濾波器的設計。

In OFDM, orthogonality must be ensured for all subchannels, while FBMC only requires orthogonality with adjacent subchannels. In order to fully exploit channel bandwidth, modulations in the subchannels must adapt to the neighbor orthogonality constraint, so Offset Quadrature Amplitude Modulation (OQAM) is used for this purpose. Frequency selective filter is accomplished by using longer and spectrally well-shaped prototype filters, and because of frequency selective filter, the sidelobe levels are lower comparing to OFDM. Combination of filter banks and OQAM modulation result in no need for guard time or cyclic prefix like OFDM, leading to higher bandwidth efficiency. In general, this technique is called Filter Bank Multicarrier (FBMC) technique.
Offset Quadrature Amplitude Modulation (OQAM) is a complex-to-real conversion, where real and imaginary part of complex-valued symbol is separated to form two new symbols. Complex-to-real conversion increases the sampling rate by a factor of 2 which causes the two new symbol to stagger. The two new symbols will be transmitted separately in one symbol period.
Frequency selective filter is a key element in complex modulated filter banks, because all synthesis and analysis filters are frequency shifted version of the prototype filter. Here we set the overlap factor of the prototype filter as 4, leading to filter length 4 times longer than DFT/IDFT. An IDFT of size 1024 is used, which leads to a 4*1024 filter length. In order to remain the size of DFT/IDFT and reduce computational complexity the polyphase network is used.

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