Reconfigurable hybrid beamforming MIMO receiver with inter-band carrier aggregation and RF-domain LMS weight adaptation
A reconfigurable, multi-band hybrid beamforming architecture is introduced. The present invention is related to a Cartesian-Combining architecture to efficiently implement RF beamforming for a single downconversion chain employing direct downconversion in which the Cartesian-Combining architecture is extended to hybrid beamforming and to heterodyne downconversion.
1. A fully-connected hybrid beamforming receiver wherein N R inputs are received from N R antennas, each of the N R inputs comprising N O streams, the receiver comprising:
circuitry, for applying complex weighting to each of the N O streams from each of the N R inputs;
circuitry implementing a multi-stage combiner, for combining one stream from each of the N R inputs to produce N O weighted, combined streams; and
circuitry implementing N O image-reject downconverters, one per weighted, combined stream;
wherein N R >2 and N O >2.
2. The receiver of claim 1 wherein each of the N O streams from each of the N R inputs is received in a different frequency band.
3. The receiver of claim 2 further comprising:
circuitry implementing N R low-noise amplifiers, each amplifier coupled to one of the N R inputs.
4. The receiver of claim 2 wherein the N O image-reject downconverters output N O downconverted streams.
5. The receiver of claim 2 wherein the circuitry for applying complex weighting to each of the N O streams comprises a cascade of a phase shifter and a variable gain amplifier.
6. The receiver of claim 2 wherein the circuitry for applying complex weighting to each of the N O streams comprises a vector modulator.
7. The receiver of claim 2 wherein the circuitry for applying complex weighting to each of the N O streams comprises a pair of programmable gain amplifiers for each of the N O streams.
8. The receiver of claim 2 wherein the image-reject downconverters comprise:
circuitry implementing a two-stage mixer.
9. The receiver of claim 8 :
wherein a first stage of the two-stage mixer performs a heterodyne downconversion of the weighted, combined stream to an intermediate frequency using a signal having a first frequency; and
wherein a second stage of the two-stage mixer performs a heterodyne downconversion of the weighted, combined stream at the intermediate frequency to a baseband frequency using a signal having a second frequency.
10. The receiver of claim 9 wherein the signal having the first frequency is generated by a local oscillator and further wherein the signal having the second frequency is derived from the signal having the first frequency.
11. The receiver of claim 10 wherein the local oscillator frequency is chosen such that the frequency bands of the combined streams are located at mutual image frequency locations.
12. The receiver of claim 10 wherein each stage of the two-stage mixers can be configured to reject either the low-side or high-side band for each combined stream with the same local oscillator frequency.
13. The receiver of claim 8 :
wherein a first stage of the two-stage mixer performs quadrature downconversion of the weighted, combined stream to the intermediate frequency and combines the real and imaginary components of the weighted, combined stream into a combined signal; and
wherein the second stage of the two-stage mixer performs quadrature downconversion of the combined signal to the baseband frequency.
14. A method for extracting N O downconverted streams from N R inputs are received from N R antennas, each of the N R inputs comprising N O streams, the method comprising:
applying complex weighting to each of the N O streams from each of the N R inputs;
for combining one stream from each of the N R inputs to produce a N O weighted, combined streams; and
applying an image-reject downconverter to each of the N O weighted, combined streams to produce the N O downconverted streams;
wherein N R >2 and N O >2.
15. The method of claim 14 wherein each of the N O streams from each of the N R inputs is received in a different frequency band.
16. The method of claim 14 further comprising:
amplifying each of the N R inputs prior to applying the complex weighting to each of the N R inputs.
17. The method of claim 16 wherein each of the N R inputs is amplified using a low-noise amplifier.
18. The method of claim 14 wherein applying an image-reject downconverter to each of the N O weighted, combined streams further comprises:
performing a heterodyne downconversion of the weighted, combined stream to an intermediate frequency using a signal having a first frequency generated by a local oscillator; and
performing a heterodyne downconversion of the weighted, combined stream at the intermediate frequency to a baseband frequency using a signal having a second frequency, derived from the first frequency.
19. The method of claim 18 wherein the local oscillator frequency is chosen such that the frequency bands of the weighted, combined streams are located at mutual image frequency locations.
20. The method of claim 14 wherein applying an image-reject downconverter to each of the N O weighted, combined streams further comprises:
performing quadrature downconversion of the weighted, combined stream to the intermediate frequency and combining real and imaginary components of the weighted, combined stream into a combined signal; and
performing quadrature downconversion of the combined signal to the baseband frequency.