High resolution MIMO radar system
An automotive radar system includes multiple radar antennas and a radar front end chip. The front end chip includes a plurality of phase rotators coupled to a local oscillator, wherein each phase rotator of the plurality of phase rotators is coupled to multiple digital phase modulators; a plurality of switches that couple selectable ones of the multiple digital phase modulators to respective amplifiers, each amplifier coupled to a respective antenna output; and a controller which provides digital control signals to the plurality of phase rotators, the multiple digital phase modulators, and the plurality of switches to synthesize transmit signals for each of the multiple radar antennas.
1. A method for operating a radar chip, comprising:
selectively coupling digital phase modulators in the radar chip to corresponding amplifiers in an array of amplifiers in the radar chip, wherein a given phase rotator of phase rotators in the radar chip is coupled to the digital phase modulators, and wherein a given amplifier in the array of amplifiers is coupled to a corresponding antenna output; and
using the phase rotators and the digital phase modulators, synthesizing individual transmit signals for the antenna outputs.
2. The method of claim 1 , wherein the digital phase modulators comprise bi-phase shift key (BPSK) modulators.
3. The method of claim 2 , wherein a given BPSK modulator in the BPSK modulators is coupled to the given phase rotator by a power splitter.
4. The method of claim 1 , wherein the method comprises, using envelope modulators, windowing or shaping bursts in the transmit signals.
5. The method of claim 4 , wherein the envelope modulators are coupled to the amplifiers.
6. The method of claim 4 , wherein the method comprises, using a controller, controlling the envelope modulators.
7. The method of claim 1 , wherein the selective coupling of the digital phase modulators is performed using switches.
8. The method of claim 7 , wherein the method comprises, using a controller, controlling the phase rotators, the digital phase modulators and the switches.
9. The method of claim 7 , wherein the switches selectively implement time division multiplexing (TDM) of the transmit signals.
10. The method of claim 1 , wherein the digital phase modulators selectively implement code division modulation (CDM) of the transmit signals based at least in part on phase code waveforms.
11. The method of claim 1 , wherein the phase rotators selectively provide Doppler division multiplexing (DDM) of the transmit signals based at least in part on frequency shift waveforms.
12. The method of claim 1 , wherein the individual transmit signals are the same.
13. The method of claim 1 , wherein the method comprises off-chip power combining to cause the amplifiers to supply the same transmit signal to: a given antenna in the antennas; different elements of the given antenna; or different antennas.
14. The method of claim 1 , wherein the method comprises off-chip power combining to cause two of the amplifiers to supply the same transmit signal with opposite signs to elements of the given antenna of the antennas; and
wherein the given antenna comprises a differential antenna.
15. The method of claim 1 , wherein the method comprises performing, using the phase rotators, beam steering.
16. The method of claim 1 , wherein the method comprises providing a local oscillator to the phase rotators.
17. The method of claim 16 , wherein the method comprises generating the local oscillator using a fractional N phase lock loop or a direct synthesis generator.
18. The method of claim 1 , wherein the transmit signals provide multi-mode multiple-input multiple-output (MIMO) signal generation.
19. The method of claim 1 , wherein the transmit signals are output non-concurrently with an overlap less than a predefined amount or no overlap.
20. The method of claim 1 , wherein the radar chip uses time division multiplexing, code division modulation (CDM) or Doppler division multiplexing (DDM) of the transmit signals based at least in part on detected environmental conditions.