US Patent No. 6,538,586 - Prepared by Attorney David Tran for Intel Corporation and filed by Intel Corporation

Brief Description:  Frequency spectrums are determined for all possible codes given a predetermined number of bits in a code. A subset of these codes is formed based on spectral properties of codes in a desired frequency band. This subset of code is then used to encode data prior to transmission over a high-speed data bus to reduce undesirable emissions on targeted frequency bands.  Due to the complexity of isolating noise along different signal paths, it may be necessary to reduce targeted frequency components in the data stream itself. Reduction of spectral emissions is typically achieved by filtering the time-domain data waveform using band-rejection filters. However, these filters, whether digital signal processing (DSP) based or analog based, distort the transition edges of the original waveform resulting in a decreased eye and varying clock skew. This may not be acceptable in a high-speed serial I/O bus with an embedded clock. Another technique to reduce spectral emissions involves setting the data bus to a low speed mode. For example, in the low speed mode, the data bus runs at one-quarter-clock speed when a wireless device attempts to receive data. This low speed mode technique, however, reduces throughput significantly.