Basic FFT, OFDM Transmitter

To generate OFDM successfully the relationship between all the carriers must be

carefully controlled to maintain the orthogonality of the carriers. For this reason, OFDM

is generated by firstly choosing the spectrum required, based on the input data, and

modulation scheme used. Each carrier to be produced is assigned some data to

transmit. The required amplitude and phase of the carrier is then calculated based on

the modulation scheme (typically differential BPSK, QPSK, or QAM). The required

spectrum is then converted back to its time domain signal using an Inverse Fourier

Transform. In most applications, an Inverse Fast Fourier Transform (IFFT) is used. The

IFFT performs the transformation very efficiently, and provides a simple way of ensuring

the carrier signals produced are orthogonal.

前一張投影片

下一張投影片

回到第一張投影片

檢視圖形版本