Low-power highly-accurate passive multiphase clock generation scheme by using polyphase filters
Exemplary embodiments of the present invention relate to a low-power highly-accurate passive multiphase clock generation scheme by using polyphase filters. An exemplary embodiment of the present invention may be low power phase-rotator-based 25 GB/s CDR architecture in case that half-rate reference clock is provided. It may be suitable for multi-lane scheme and incorporate phase interpolator with improved phase accuracy to make Nyquist-sampling clock phase. To improve the phase accuracy, poly phase filter may be used for converting 4-phase to 8-phase and interpolate adjacent 45 degree different phases. The linearity of phase rotator may be improved by proposed harmonic rejection poly phase filter (HRPPF) using the characteristic of notch filter response.
1. A CDR (Clock-and-Data Recovery) apparatus for low-power highly accurate multiphase clock generation by using polyphase filter, the CDR apparatus comprising:
phase rotators configured to output arbitrary phases by taking a weighted average current dynamically wherein the phase rotators requiring multiphase clock signals;
phase interpolators configured to output arbitrary phases by weighted average for current wherein a ratio of the weighted average for current is fixed;
a 1st polyphase filter being connected to the phase rotators for making the multiphase clock signals to be sinusoidal; and
a 2nd polyphase filter being connected between the phase rotators and the phase interpolators for delaying the multiphase clock signals,
wherein the 2nd polyphase filter separates adjacent clock phases to be interpolated with identical weights.
2. The CDR apparatus of claim 1 , wherein the 1st polyphase filter eliminates a dominant harmonic distortion.
3. The CDR apparatus of claim 2 , wherein the dominant harmonic distortion is a third harmonic distortion.
4. The CDR apparatus of claim 1 , wherein the 1st polyphase filter is HRPPF (Harmonic Rejection Polyphase Filter).
5. The CDR apparatus of claim 4 , wherein the HRPPF rejects high order harmonics of the clock signals by using a characteristic of notch filter response.
6. The CDR apparatus of claim 1 , wherein the 2nd polyphase filter creates Nyquist rate sampling clock signals.
7. The CDR apparatus of claim 1 , wherein the multiphase clock signals are at least four phase clock signals.
8. The CDR apparatus of claim 7 , wherein the 2nd polyphase filter is 8-phase polyphase filter used for converting 4-phase to 8-phase.