Multi-band crest factor reduction
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorsLeonard Rexberg, Håkan Malmqvist
Life of this patent
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Abstract
Clipping a widely-separated, multi-carrier signal is effectively performed without having to use a high sampling speed. Clipping is performed in a first stage at a combined signal level, but with a predetermined carrier separation of at least twice the channel bandwidth (2CBW), followed by repositioning the carriers at baseband zero frequency. After clipping, carriers are placed at their respective center frequencies with full carrier separation reintroduced in a second stage. Iterative clipping stages smooth out signal reshaping and re-settled amplitudes for combined carriers.
Claims18
A method for crest factor reduction (CFR) of a multi-carrier signal, each carrier of the multi-carrier signal having a respective center frequency and a channel bandwidth (CBW), the method comprising:
- positioning a baseband version of each of the carriers to a frequency separation between adjacent carriers of at least 2 CBW,
- thereafter, combining the positioned carriers into a composite signal,
- clipping the composite signal,
- repositioning each carrier of the clipped composite signal back into a baseband version centered at zero frequency, and
- positioning each carrier at their respective center frequency.
An apparatus for crest factor reduction (CFR) of a multi-carrier signal, each carrier of the multi-carrier signal having a respective center frequency and a channel bandwidth (CBW), the apparatus comprising processing circuitry configured to:
- position a baseband version of each of the carriers to a frequency separation between adjacent carriers of at least 2 CBW,
- thereafter, combine the positioned carriers into a composite signal,
- clip the composite signal,
- reposition each carrier of the clipped composite signal back into a baseband version centered at zero frequency, and
- position each carrier of the crest factor reduced multi-carrier signal at their respective center frequency.
An transmitter for crest factor reduction (CFR) of a multi-carrier signal, each carrier of the multi-carrier signal having a respective center frequency and a channel bandwidth (CBW), the transmitter comprising processing circuitry configured to:
- position a baseband version of each of the carriers to a frequency separation between adjacent carriers of at least 2 CBW,
- combine the positioned carriers into a composite signal,
- clip the composite signal,
- reposition each carrier of the clipped composite signal back into a baseband version centered at zero frequency, and
- filter clipping distortion outside each carrier's channel bandwidth, and
- reposition each carrier of the clipped composite signal to their respective center frequencies.
Dependencies are inferred from the claim text.