Enabling RX signal path synchronization and alignment signals in a highly integrated TX RFIC
A transmit (TX) signal path circuit in a multiple-input, multiple-output (MIMO) transceiver responsive to a digital front end (DFE) for generating receive (RX) path phase alignment signals is disclosed. A digital up-conversion block uses a first numerically-controlled oscillator (NCO) for generating digital intermediate frequency (IF) signals for ordinary TX signal generation, and a different, second NCO for generating digital IF signals for RX phase alignment signal generation. An RF up-conversion block uses a TX local oscillator (LO) for generating analog RF signals for ordinary TX signal generation, and a different feedback (FB) LO for generating analog RF signals for RX phase alignment signal generation. Thus, phase alignment of the circuitry used for ordinary TX signal generation is left undisturbed by RX phase alignment signal generation.
1. A multiple-input, multiple-output (MIMO) transceiver, the MIMO transceiver comprising:
a digital up-converter comprising:
a first numerically-controlled oscillator (NCO) configured to modulate a digital baseband signal to generate a digital intermediate frequency (IF) signal in a transmit mode, and
a second NCO configured to modulate the digital baseband signal to generate the digital IF signal in a receive phase alignment mode;
a digital-to-analog converter (DAC) configured to receive the digital IF signal and generate an analog IF signal; and
a radio frequency (RF) up-converter comprising:
a first divide-by-2 in-phase quadrature-phase (IQ-DIV2) generator configured to use a transmit local oscillator (LO) to modulate the analog IF signal to generate a transmit signal in the transmit mode, and
a second IQ-DIV2 generator configured to use a feedback LO to modulate the analog IF signal to generate a receive phase alignment signal in the receive phase alignment mode.
2. The MIMO transceiver of claim 1 , wherein the RF up-converter comprises a first analog frequency mixer operably coupled to the first IQ-DIV2 generator and a second analog frequency mixer operably coupled to the second IQ-DIV2 generator.
3. The MIMO transceiver of claim 2 , wherein the RF up-converter comprises a first multiplexer coupled to the first analog frequency mixer and the first IQ-DIV2 generator, and wherein the RF up-converter comprises a second multiplexer coupled to the second analog frequency mixer and the second IQ-DIV2 generator.
4. The MIMO transceiver of claim 3 , wherein the first multiplexer decouples the first analog frequency mixer from the first IQ-DIV2 generator in the receive phase alignment mode.
5. The MIMO transceiver of claim 3 , wherein the second multiplexer decouples the second analog frequency mixer from the second IQ-DIV2 generator in the transmit mode.
6. The MIMO transceiver of claim 1 , wherein the digital up-converter comprises a first digital frequency mixer operably coupled to the first NCO and a second digital frequency mixer operably coupled the second NCO.
7. The MIMO transceiver of claim 6 , wherein the digital up-converter comprises a first multiplexer coupled to the first NCO and the first digital frequency mixer, and wherein the digital up-converter comprises a second multiplexer coupled to the second NCO and the second digital frequency mixer.
8. The MIMO transceiver of claim 7 , wherein the first multiplexer decouples the first NCO from the first digital frequency mixer in the receive phase alignment mode.
9. The MIMO transceiver of claim 7 , wherein the second multiplexer decouples the second NCO from the second digital frequency mixer in the transmit mode.
10. The MIMO transceiver of claim 1 , wherein the MIMO transceiver comprises a feedback circuit configured to monitor an RF output signal based on the transmit signal in the transmit mode, or based on the receive phase alignment signal in the receive phase alignment mode, the feedback circuit being configured to down-convert the RF output signal using the feedback LO.
11. The MIMO transceiver of claim 1 , wherein the MIMO transceiver is mounted on a printed circuit board.
12. The MIMO transceiver of claim 1 , wherein the MIMO transceiver is a radio frequency integrated circuit (RFIC).
13. A method for operating a multiple-input, multiple-output (MIMO) transceiver, the method comprising:
digitally up-converting a digital baseband signal to generate a digital intermediate frequency (IF) signal using:
a first numerically-controlled oscillator (NCO) in a transmit mode, and
a second NCO in a receive phase alignment mode;
generating an analog IF signal from the digital IF signal using a digital-to-analog converter (DAC); and
modulating the analog IF signal comprises:
generating a transmit signal in the transmit mode using a first divide-by-2 in-phase quadrature-phase (IQ-DIV2) generator and a transmit local oscillator (LO), and
generating a receive phase alignment signal in the receive phase alignment mode using a second IQ-DIV2 generator and a feedback LO.
14. The method of claim 13 , wherein modulating the analog IF signal comprises:
using a first analog frequency mixer in the transmit mode, and
using a second analog frequency mixer in the receive phase alignment mode.
15. The method of claim 14 , wherein the method comprises:
coupling the first analog frequency mixer to the first IQ-DIV2 generator in the transmit mode, and
coupling the second analog frequency mixer to the second IQ-DIV2 generator in the receive phase alignment mode.
16. The MIMO transceiver of claim 14 , wherein the method comprises decoupling the first analog frequency mixer from the first IQ-DIV2 generator in the receive phase alignment mode.
17. The MIMO transceiver of claim 14 , wherein the method comprises decoupling the second analog frequency mixer from the second IQ-DIV2 generator in the transmit mode.
18. The method of claim 13 , wherein the method comprises decoupling the first NCO from a first digital frequency mixer in the receive phase alignment mode.
19. The method of claim 13 , wherein the method comprises decoupling the second NCO from a second digital frequency mixer in the transmit mode.
20. The method of claim 13 , wherein the method comprises:
down-converting an RF output signal using the feedback LO; and
monitoring the RF output signal based on:
the transmit signal in the transmit mode, and
the receive phase alignment signal in the receive phase alignment mode.