Transmitter architecture for generating 4
Methods, systems, and apparatuses provide a transmitter architecture that directly generates 4 N -QAM constellation using a raw bit stream as input and that does not require a digital-to-analog converter (DAC) in the signal path.
1. A wireless transmitter, comprising:
a plurality of PRBS streams, wherein each PRBS stream of the plurality of PRBS streams drives a different QPSK modulator branch of a plurality of QPSK modulator branches of the wireless transmitter;
a differential power combiner electrically coupled to outputs of each QPSK modulator branch of the plurality of QPSK modulator branches; and
a power amplifier electrically coupled to an output of the differential power combiner.
2. The wireless transmitter of claim 1 , wherein each QPSK modulator branch comprises a direct conversion IQ mixer.
3. The wireless transmitter of claim 1 , wherein each QPSK modulator branch is configured to create desired symbol spacing by employing internal gain control.
4. The wireless transmitter of claim 3 , wherein the desired symbol spacing comprises one or more of 2d or 4d.
5. The wireless transmitter of claim 1 , wherein the power amplifier is configured to produce an N-QAM signal by combining weighted output signals from the plurality of QPSK modulator branches.
6. The wireless transmitter of claim 5 , wherein the power amplifier is configured to produce a 4 N -QAM signal by combining weighted output signals from the plurality of QPSK modulator branches.
7. The wireless transmitter of claim 1 , wherein the power amplifier is configured to deliver a power signal to an antenna to establish a wireless communication link.
8. The wireless transmitter of claim 1 , wherein the differential power combiner is configured to provide port-to-port isolation.
9. The wireless transmitter of claim 8 , wherein the port-to-port isolation is configured to minimize interaction between paths of the QPSK modulators.
10. The wireless transmitter of claim 8 , wherein the port-to-port isolation is configured to minimize error-vector-magnitude (EVM) cross-talk.
11. A method of producing a 4 N -QAM signal, comprising:
driving each QPSK modulator branch of a plurality of QPSK modulator branches using a different PRBS stream of a plurality of PRBS streams;
electrically coupling a differential power combiner to outputs of each QPSK modulator branch of the plurality of QPSK modulator branches; and
electrically coupling a power amplifier to an output of the differential power combiner, wherein the power amplifier combines weighted output signals from the plurality of QPSK modulator branches to produce a 4 N -QAM signal.
12. The method of claim 11 , wherein each QPSK modulator branch comprises a direct conversion IQ mixer.
13. The method of claim 11 , further comprising:
creating desired symbol spacing by employing, in each QPSK modulator branch, internal gain control.
14. The method of claim 13 , wherein the desired symbol spacing comprises one or more of 2d or 4d.
15. The method claim 11 , further comprising:
establishing a wireless communication link with an antenna by delivering, using the power amplifier, a power signal to an antenna.
16. The method of claim 11 , wherein the differential power combiner is configured to provide port-to-port isolation.
17. The method of claim 16 , wherein the port-to-port isolation is configured to minimize interaction between paths of the QPSK modulators.
18. The method of claim 16 , wherein the port-to-port isolation is configured to minimize error-vector-magnitude (EVM) cross-talk.