System and method for anticipatory receiver switching based on signal quality estimation
View Patent ↗In various embodiments, a first and second complex multiplier may be configured to receive an input signal and provide a baseband I component signal and a baseband Q component signal, respectively. A first and second filter may be configured to filter the baseband I component signal and the baseband Q component signal, respectively. An equalizer may be configured to equalize the filtered baseband I component signal and the filtered baseband Q component signal. A carrier recovery portion may be configured to generate a reference signal based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal. A first and second multilevel comparator may be configured to receive the equalized filtered baseband I component signal from the carrier recovery portion and provide an output I and receive the equalized filtered baseband Q component signal and provide an output Q signal for further modulation.
1. A system comprising:
a first complex multiplier and a second complex multiplier, the first complex multiplier configured to receive an input signal and provide a baseband I component signal, the second complex multiplier configured to receive the input signal and provide a baseband Q component signal; a first filter configured to filter the baseband I component signal;
a second filter configured to filter the baseband Q component signal; an equalizer configured to equalize the filtered baseband I component signal and to equalize the filtered baseband Q component signal;
a carrier recovery portion configured to generate a reference signal based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
a first multilevel comparator configured to receive the equalized filtered baseband I component signal from the carrier recovery portion and provide an output I signal for further demodulation;
a second multilevel comparator configured to receive the equalized filtered baseband Q component signal from the carrier recovery portion and provide an output Q signal for further demodulation; and
a signal quality estimation circuit configured to estimate a signal quality based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal, the signal quality estimation circuit comprising:
a distance calculator configured to determine a distance between an ideal symbol and a received symbol of the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
an average calculator configured to determine an average distance based on the distance from the distance calculator; the average distance being between successive received symbols and corresponding ideal symbols; and
a comparator configured to compare the average distance to a predetermined threshold.
2. The system of claim 1 , further comprising a lookup table (LUT) wherein the LUT provides a sine signal to the first complex multiplier and a cosine signal to the second complex multiplier.
3. The system of claim 2 , wherein the sine signal and the cosine signal are based on the reference signal from the carrier recovery portion.
4. The system of claim 2 , wherein the sine signal is substantially the same carrier frequency and is in phase with the input signal.
5. The system of claim 2 , wherein the cosine signal is substantially the same carrier frequency and is in quadrature phase with the input signal.
6. The system of claim 1 , wherein the signal quality estimation circuit is configured to receive the equalized filter baseband I component signal from the carrier recovery portion and receive the equalized filtered baseband Q component signal from the carrier recovery portion.
7. The system of claim 1 , wherein the signal quality estimation circuit is further configured to generate an alert signal when a quality is low based on the comparison of the average distance to the predetermined threshold.
8. A method comprising:
multiplying an input signal with a sine signal to provide a baseband I component signal; multiplying the input signal with a cosine signal to provide a baseband Q
filtering the baseband I component signal;
filtering the baseband Q component signal; equalizing the filtered baseband I component signal;
equalizing the filtered baseband Q component signal;
generating a reference signal based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
comparing the equalized filtered baseband I component signal to provide an output I signal for further demodulation; and
comparing the equalized filtered baseband Q component signal to provide an output Q signal for further demodulation; and
estimating a signal quality based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
wherein estimating the signal quality comprises:
calculating a distance between an ideal symbol and a received symbol of the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
calculating an average distance based on the distance from the distance calculator; and the average distance being between successive received symbols and corresponding ideal symbols;
comparing the average distance to a predetermined threshold.
9. The method of claim 8 , further comprising generating the sine signal and the cosine signal with a lookup table (LUT).
10. The method of claim 9 , wherein the sine signal and the cosine signal is based on the reference signal from the carrier recovery portion.
11. The method of claim 9 , wherein the sine signal is substantially the same carrier frequency and is in phase with the input signal.
12. The method of claim 9 , wherein the cosine signal is substantially the same carrier frequency and is in quadrature phase with the input signal.
13. The method of claim 8 , wherein the signal quality estimation circuit is further configured to generate an alert signal when a quality is low based on the comparison of the average distance to the predetermined threshold.
14. A system comprising:
a means for multiplying an input signal with a sine signal to provide a baseband I component signal;
a means for multiplying the input signal with a cosine signal to provide a baseband Q component signal;
a means for filtering the baseband I component signal; a means for filtering the baseband Q component signal;
a means for equalizing the filtered baseband I component signal;
a means for equalizing the filtered baseband Q component signal; a means for generating a reference signal based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
a means for comparing the equalized filtered baseband I component signal to provide an output I signal for further demodulation; and
a means for comparing the equalized filtered baseband Q component signal to provide an output Q signal for further demodulation I and a means for estimating a signal quality based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal;
wherein estimating the signal quality comprises:
calculating a distance between an ideal symbol and a received symbol of the equalized filtered baseband I component signal and the equalized filtered baseband Q
component signal;
calculating an average distance based on the distance from the distance calculator; the average distance being between successive received symbols and corresponding ideal symbols; and
comparing the average distance to a predetermined threshold.