Portable communications device with demodulation correction and related methods
View Patent ↗A portable communications device communicates based upon constant envelope orthogonal frequency-division multiplexing (CE-OFDM). The portable communications device may include an antenna for receiving a CE-OFDM signal, and a receiver coupled to the antenna. The receiver may include a frequency domain equalizer (FDE) operating based upon a channel estimate of the received CE-OFDM signal, a non-linear function block coupled to and downstream from the FDE, and a demodulation correction block coupled to and downstream from the non-linear function block for correcting an output of the non-linear function block.
1. A portable communications device communicating based upon constant envelope orthogonal frequency-division multiplexing (CE-OFDM) and comprising:
an antenna for receiving a CE-OFDM signal; and
a receiver coupled to said antenna and comprising
a frequency domain equalizer (FDE) operating based upon a channel estimate of the received CE-OFDM signal,
at least one non-linear function block coupled to and downstream from said FDE, and
a demodulation correction block coupled to and downstream from said at least one non-linear function block for correcting an output thereof.
2. The portable communications device according to claim 1 wherein said receiver further comprises a forward error correction (FEC) block coupled to and downstream from said demodulation correction block and cooperating therewith.
3. The portable communications device according to claim 1 wherein said demodulation correction block comprises a plurality of look-up tables for corresponding values of non-linearity from said at least one non-linear function block.
4. The portable communications device according to claim 1 wherein the channel estimate is based upon a test chirp signal.
5. The portable communications device according to claim 2 wherein said demodulation correction block and said FEC block correct non-linearity of the output of said at least one non-linear function block by at least:
processing a test CE-OFDM frame; and
weighting CE-OFDM tones based upon the processed test CE-OFDM frame.
6. The portable communications device according to claim 5 wherein the test CE-OFDM frame has symbols set to known amplitudes.
7. The portable communications device according to claim 1 wherein said at least one non-linear function block comprises an arctangent function block.
8. The portable communications device according to claim 1 wherein said receiver further comprises a matched filter block coupled between said at least one non-linear function block and said demodulation correction block; and wherein said demodulation correction block further corrects for distortions from said matched filter block.
9. A portable communications device communicating based upon constant envelope orthogonal frequency-division multiplexing (CE-OFDM) and comprising:
an antenna for receiving a CE-OFDM signal; and
a receiver coupled to said antenna and comprising
a frequency domain equalizer (FDE) operating based upon a channel estimate of the received CE-OFDM signal from a test chirp signal,
at least one non-linear function block downstream from said FDE, and
a demodulation correction block being downstream from said at least one non-linear function block and using a test CE-OFDM frame to correct an output thereof.
10. The portable communications device according to claim 9 wherein said receiver further comprises a forward error correction (FEC) block downstream from said demodulation correction block and cooperating therewith.
11. The portable communications device according to claim 10 wherein said demodulation correction block and said FEC block correct non-linearity of the output of said at least one non-linear function block by at least:
processing the test CE-OFDM frame; and
weighting CE-OFDM tones based upon the processed test CE-OFDM frame.
12. The portable communications device according to claim 11 wherein the test CE-OFDM frame has symbols set to known amplitudes.
13. The portable communications device according to claim 9 wherein said at least one non-linear function block comprises an arctangent function block.
14. The portable communications device according to claim 9 wherein said receiver further comprises a matched filter block between said at least one non-linear function block and said demodulation correction block; and wherein said demodulation correction block further corrects for distortions from said matched filter block.
15. A method of operating a portable communications device communicating based upon constant envelope orthogonal frequency-division multiplexing (CE-OFDM) and comprising a frequency domain equalizer (FDE), a demodulation correction block downstream from the FDE, and at least one non-linear function block therebetween, the method comprising:
receiving a CE-OFDM signal;
operating the FDE based upon a channel estimate of the received CE-OFDM signal; and
using the demodulation correction block for correcting the output of the at least one non-linear function block.
16. The method according to claim 15 further comprising performing forward error correction (FEC) downstream from the demodulation correction block and cooperating therewith.
17. The method according to claim 15 wherein the demodulation correction block uses a plurality of look-up tables for corresponding values of non-linearity from the at least one non-linear function block.
18. The method according to claim 15 wherein the channel estimate is based upon a test chirp signal.
19. The method according to claim 15 wherein correcting the output of the FDE comprises:
processing a test CE-OFDM frame; and
weighting CE-OFDM tones based upon the processed test CE-OFDM frame.
20. The method according to claim 19 wherein the test CE-OFDM frame has symbols set to known amplitudes.