Method and system for image rejection by using post mixer I/Q equalization
The invention provides a system and method for tuning broadband signals by using post mixer I/Q equalization. An Image Rejection Mixer (IRM) is used for mixing Radio Frequency (RF) signals and rejecting image signals from the desired RF signals. The IRM includes an I/Q mixer and a filter. The I and Q paths resulting from the mixing operation in the I/Q mixer are equalized in amplitude and phase by an I/Q equalizer. Thereafter, the image signals are rejected from the desired RF signals using the filter.
1. A broadband tuner comprising:
an I/Q mixer, the I/Q mixer mixing input broadband signals;
at least one amplitude equalizer, the at least one amplitude equalizer equalizing amplitudes of I and Q paths generated by the I/Q mixer;
a phase aligner, the phase aligner aligning phases of the I and Q paths with equalized amplitudes to generate an output RF signal, wherein the phases are aligned in quadrature; and
a polyphase filter, the polyphase filter filtering an image signal from the output RF signal.
2. The broadband tuner according to claim 1 , wherein the at least one amplitude equalizer comprises a plurality of Variable Gain amplifiers (VGA), the plurality of VARs amplifying the I and Q paths.
3. The broadband tuner according to claim 1 , wherein the at least one amplitude equalizer comprises a level detect circuit, the level detect circuit sensing difference in amplitudes of the I and Q paths.
4. The broadband tuner according to claim 1 , wherein the phase aligner comprises at least four adders, the at least four adders adding differential signals of the I and Q paths.
5. The broadband tuner according to claim 1 , wherein at least one of the I/Q mixer, the at least one amplitude equalizer, the phase aligner and the polyphase filter are designed using analog design techniques.
6. The broadband tuner according to claim 1 , wherein at least one of the I/Q mixer, the at least one amplitude equalizer, the phase aligner and the polyphase filter are designed using digital design techniques.
7. The broadband tuner according to claim 1 , wherein at least one of the I/Q mixer, the at least one amplitude equalizer, the phase aligner and the polyphase filter are designed using complementary metal oxide semiconductor (CMOS) technology.
8. The broadband tuner according to claim 1 , wherein the input broadband signals are supplied through a Community Access Television (CATV) infrastructure.
9. A broadband digital data system utilizing the broadband tuner of claim 1 .
10. A broadband analog system utilizing the broadband tuner of claim 1 .
11. A method for tuning broadband signals, the method comprising the steps of:
mixing input broadband signals, wherein the mixing is performed by an I/Q mixer;
equalizing amplitudes of I and Q paths generated by the I/Q mixer;
aligning phases of the I and Q paths with equalized amplitudes to generate phase-aligned I and Q paths, wherein the phases are aligned in quadrature;
equalizing amplitudes of the phase-aligned I and Q paths to generate an output RF signal; and
filtering an image signal from the output RF signal.
12. The method according to claim 11 , wherein the step of equalizing amplitudes of I and Q paths comprises the step of sensing difference in amplitude of the I and Q paths.
13. The method according to claim 11 , wherein the step of aligning phases of the I and Q paths comprises the step of adding differential signals of the I and Q paths with equalized amplitudes.
14. The method according to claim 11 , wherein the input broadband signals are supplied through a Community Access Television (CATV) infrastructure.