Aliasing enhanced OFDM communications
View Patent ↗A system comprises an analog front end (AFE), an analog-to-digital converter (ADC), and alias detection circuitry. The AFE may be operable to receive an analog signal via a communication medium, wherein a first frequency band of the analog signal is occupied by an OFDM symbol and a second frequency band of the analog signal is occupied by first aliases generated during digital-to-analog conversion of the OFDM symbol. The ADC is operable to digitize the particular band of the analog signal to generate a digital signal, wherein, during the digitization, aliasing of the first aliases results in second aliases which fall into the first frequency band. The alias detection circuitry is operable to detect the second aliases in the first frequency band of the digital signal, and process the digital signal based on the detected second aliases to generate an output signal.
1. A system comprising:
an analog front end (AFE) configured to receive an analog signal via a communication medium, wherein a first frequency band of the analog signal is occupied by an Orthogonal Frequency Division Multiplexing (OFDM) symbol and a second frequency band of the analog signal is occupied by first aliases generated during digital-to-analog conversion of the OFDM symbol;
an analog-to-digital converter (ADC) configured to digitize a particular band of the analog signal to generate a digital signal, wherein, during the digitization, aliasing of the first aliases results in second aliases which fall into the first frequency band; and
alias detection circuitry configured to:
detect the second aliases in the first frequency band of the digital signal; and
process the digital signal based on the detected second aliases to generate an output signal.
2. The system of claim 1 , wherein the processing of the digital signal comprises removal of the detected second aliases from the first frequency band of the digital signal.
3. The system of claim 1 , wherein the processing of the digital signal comprises:
removal of the detected second aliases from the first frequency band of the digital signal;
phase adjustment of the detected second aliases to generate phase-adjusted aliases; and
addition of the phase-adjusted aliases to the first frequency band of the digital signal.
4. The system of claim 3 , further comprising a demodulator configured to demodulate the output signal.
5. The system of claim 1 , further comprising discrete Fourier transform (DFT) circuitry, wherein an output of the ADC is coupled to an input of the DFT circuitry.
6. The system of claim 5 , wherein an antialiasing filter operates on signals communicated from the output of the ADC to the input of the DFT circuitry.
7. The system of claim 1 , wherein:
the OFDM symbol occupies a bandwidth that is equal to a bandwidth of the first frequency band and a bandwidth of the second frequency band.
8. A method comprising:
receiving, in an analog front end (AFE) via a communication medium, an analog signal wherein a first frequency band of the analog signal is occupied by an Orthogonal Frequency Division Multiplexing (OFDM) symbol and a second frequency band of the analog signal is occupied by first aliases generated during digital-to-analog conversion of the OFDM symbol;
digitizing, by an analog-to-digital converter (ADC), a particular band of the received signal to generate a digital signal, wherein, during the digitizing, aliasing of the first aliases results in second aliases which fall into the first frequency band;
detecting, by alias detection circuitry, the second aliases in the first frequency band of the digital signal; and
processing, by the alias detection circuitry, the digital signal based on the detected second aliases, wherein the processing results in an output signal.
9. The method of claim 8 , wherein the processing of the digital signal comprises removing the detected second aliases from the first frequency band of the digital signal.
10. The method of claim 8 , wherein the processing of the digital signal comprises:
removing the detected second aliases from the first frequency band of the digital signal;
phase adjusting the detected second aliases to generate phase-adjusted aliases; and
adding the phase-adjusted aliases to the first frequency band of the digital signal.
11. The method of claim 10 , further comprising demodulating, by a demodulator, the output signal.
12. The method of claim 8 , wherein an output of the ADC is coupled to an input of discrete Fourier transform (DFT) circuitry.
13. The method of claim 12 , wherein anti-aliasing filtering is performed on signals communicated from the output of the ADC to the input of the DFT circuitry.
14. The method of claim 8 , wherein:
the OFDM symbol occupies a bandwidth that is equal to a bandwidth of the first frequency band and a bandwidth of the second frequency band.
15. A system comprising:
a digital-to-analog converter (DAC) configured to convert a digital signal that comprises a digital representation of an Orthogonal Frequency Division Multiplexing (OFDM) symbol to an analog signal that comprises an analog representation of the OFDM symbol and aliases generated during the conversion, wherein:
the digital representation of the OFDM symbol spans from fs−B hertz to fs hertz of the digital signal, wherein
B is a bandwidth of the OFDM symbol, and
fs is a sampling frequency of the DAC; and
an analog front-end (AFE) configured to process the analog signal to generate an output signal comprising the analog representation of the OFDM symbol and the aliases.
16. The system of claim 15 , wherein the aliases occupy B hertz of the output signal.
17. The system of claim 15 , wherein:
an input of the AFE is coupled to an output of the DAC.
18. The system of claim 15 , wherein the analog representation of the OFDM symbol and the aliases occupy a band of the output signal that ranges from fs−B to fs+B.
19. The system of claim 15 , wherein the AFE is configured to upconvert the analog signal to a frequency band centered at f RF hertz, wherein f RF is a transmission frequency.
20. The system of claim 15 , wherein the analog representation of the OFDM symbol and the aliases occupy a band of the output signal that ranges from f RF −B to f RF +B, wherein f RF is a transmission frequency.