Reconfigurable, bi-directional, multi-band front end for a hybrid beamforming transceiver
Designs and techniques to enhance power-efficiency and incorporate new features in millimeter-wave MIMO transceivers are described. A new mechanism for built-in dual-band, per-element self-interference cancellation (SIC) is introduced to enable multi-antenna frequency-division duplex (FDD) and full-duplex (FD) operation. Additionally, several innovative circuit concepts are introduced, including low-loss wideband antenna interface design, dual-band power combining PA, dual-band RF-SIC design, and bi-directional MIMO signal path design.
1. A bi-directional, transmit/receive module suitable for use as a front-end interface between radio electronics and an antenna array in a beamforming transceiver, comprising:
a shared antenna interface network;
a transmit path power amplifier coupled to the shared antenna interface network;
a receive path low noise amplifier coupled to the shared antenna interface network;
a splitter/combiner circuit coupled to transmit and receive paths;
a bi-directional complex-valued weighting circuit for each multiple-input-multiple-output stream, coupled to the splitter/combiner circuit; and
self-interference cancelling circuitry for:
controlling amplitude and phase of a transmitted signal to produce a cancellation signal; and
injecting the cancellation signal into the receive path prior to the splitter/combiner.
2. The transmit/receive module of claim 1 further comprising, for each multiple-input-multiple-output stream:
a fine gain control; and
a fine phase control.
3. The transmit/receive module of claim 1 , the shared antenna interface network acting as a two-way transformer power combiner when operated in transmit mode and as a matching network to a low noise amplifier in receive mode.
4. The transmit/receive module of claim 3 , the antenna interface network having a high-power transmit mode in which dual power amplifier slices are used and a low power mode in which a single power amplifier slice is used.
5. The transmit/receive module of claim 3 wherein the power amplifier slices are turned on or off using switches.
6. The transmit/receive module of claim 3 wherein both power slices are turned off when the transmit/receive module is in receive mode.
7. The transmit/receive module of claim 4 , each power amplifier slice comprising one or more driver stages to drive the splitter/combiner circuit.
8. The transmit/receive module of claim 5 , each output stage comprising a dual-band 2nd harmonic shorting network.
9. The transmit/receive module of claim 1 wherein the received signal and the cancellation signal have similar frequency responses at the resonant frequencies at bands of interest.
10. The transmit/receive module of claim 1 in which the transmit/receive module is operated either in transmit or receive mode, and further wherein other transmit/receive modules in accordance with claim 1 are operated in either transmit or receive mode simultaneously.
11. The transmit/receive module of claim 10 wherein each antenna element in the antenna array is shared between the transmit and receive paths.
12. The transmit/receive module of claim 10 wherein the transmit and receive paths use separate antenna arrays.
13. The transmit/receive module of claim 12 wherein a radio frequency domain cancellation signal is generated for each element in the receive antenna array.
14. The transmit/receive module of claim 12 wherein each radio frequency domain cancellation signal is generated using a separate upconverter and a digital-to-analog converter.
15. The transmit/receive module of claim 13 wherein any residual interference is cancelled in digital domain in the receive array.
16. A bi-directional fully-connected hybrid beamforming transceiver for simultaneously transmitting a transmit signal and receiving a receive signal comprising:
a transmit/receive module of claim 1 configured for transmitting; and
a transmit/receive module of claim 1 configured for receiving;
wherein self-interference having a large group delay is cancelled by directing a spatial-null towards reflection paths in both the transmitting transmit/receive module and the receiving transmit/receive module.
17. The bi-directional fully-connected hybrid beamforming transceiver of claim 16 wherein the transmit/receive module configured for receiving uses the receive path to receive and the transmit path to upconvert a copy of a baseband transmit signal, wherein the upconverted copy of the baseband transmit signal is independently complex weighted to cancel an incoming transmit signal in each receive antenna element.