Programmable code generation for radar sensing systems
A radar sensing system for a vehicle has multiple transmitters and receivers on a vehicle. The transmitters are configured to transmit radio signals which are reflected off of objects in the environment. There are one or more receivers that receive the reflected radio signals. Each receiver has an antenna, a radio frequency front end, an analog-to-digital converter (ADC), and a digital signal processor. The transmitted signals are based on spreading codes generated by a programmable code generation unit. The receiver also makes use of the spreading codes generated by the programmable code generation unit. The programmable code generation unit is configured to selectively generate particular spreading codes that have desired properties.
1. A radar sensing system comprising:
a plurality of transmitters configured to transmit radio signals; and
a plurality of receivers configured to receive radio signals that include the transmitted radio signals transmitted by the transmitters and reflected from objects in an environment;
wherein each transmitter of the plurality of transmitters is configured to receive a respective spreading code chip sequence of a plurality of spreading code chip sequences, and wherein each transmitter of the plurality of transmitters is configured to generate radio signals as defined by their respective spreading code chip sequences; and
wherein each receiver of the plurality of receivers is configured to receive spreading code chip sequences corresponding to each of the respective spreading code chip sequences received by the plurality of transmitters, and wherein each receiver of the plurality of receivers is configured to process received radio signals as defined by the spreading code chip sequences.
2. The radar sensing system of claim 1 further comprising a code chip generator, wherein the spreading code chip sequences received by both the plurality of transmitters and the plurality of receivers are generated by the code chip generator.
3. The radar sensing system of claim 2 , wherein the code chip generator comprises a controller, a plurality of feedback shift registers, a logic device, and a memory.
4. The radar sensing system of claim 3 , wherein the controller is operable to configure the plurality of feedback shift registers with any set of feedback connections.
5. The radar sensing system of claim 3 , wherein the logic device is configured to alter the output of the feedback shift registers in order to alter properties of sequences produced by the feedback shift registers, and wherein altering output of the feedback shift registers includes balancing the DC properties of the sequences, such that a sum of code chip values of 1 and 0 is below a DC threshold value.
6. The radar sensing system of claim 3 , wherein the memory is configured to store spreading code chip sequences, and wherein the controller is operable to select a corresponding spreading code chip sequence of the stored spreading code chip sequences for each transmitter of the plurality of transmitters.
7. The radar sensing system of claim 6 , wherein the memory is configured to store a first spreading code chip sequence, and wherein the code chip generator is configured to output the first spreading code chip sequence for a first transmitter of the plurality of transmitters, and further configured to output delayed versions of the first spreading code chip sequence for each of the other transmitters of the plurality of transmitters.
8. A method for controlling a radar sensing system comprising a plurality of transmitters and a plurality of receivers, the method comprising:
generating a plurality of spreading code chip sequences;
transmitting, with the transmitters, radio signals;
receiving, with the receivers, radio signals that include the transmitted radio signals transmitted by the transmitters and reflected from objects in an environment;
processing, with a first receiver of the plurality of receivers, the received radio signals and outputting processed radio signals;
wherein each transmitter of the plurality of transmitters receives a respective spreading code chip sequence of a plurality of spreading code chip sequences, and wherein each transmitter of the plurality of transmitters generates a modulated radio signal defined by their respective spreading code chip sequences; and
wherein each receiver of the plurality of receivers receives spreading code chip sequences corresponding to each of the respective spreading code chip sequences received by the plurality of transmitters, and wherein each receiver of the plurality of receivers processes received radio signals as defined by the spreading code chip sequences.
9. The method of claim 8 , wherein the spreading code chip sequences comprise at least one of Hadamard sequences, Golay sequences, Frank-Zadoff-Chu sequences, and APAS sequences.
10. The method of claim 8 , further comprising balancing a DC balance of the spreading codes, such that a sum of code chip values of 1 and 0 is below a DC threshold value.
11. The method of claim 8 further comprising selecting from a memory spreading code chip sequences from a plurality of spreading code chip sequences stored in the memory, such that a corresponding spreading code chip sequence is selected for each transmitter of the plurality of transmitters.
12. The method of claim 8 further comprising selecting from a memory a first spreading code chip sequence for outputting to a first transmitter of the plurality of transmitters, and outputting delayed versions of the first spreading code chip sequence to each of the other transmitters of the plurality of transmitters.
13. A radar sensing system comprising:
a plurality of transmitters configured to transmit radio signals; and
a plurality of receivers configured to receive radio signals that include the transmitted radio signals transmitted by the transmitters and reflected from objects in an environment;
wherein a first transmitter of the plurality of transmitters is configured to generate modulated radio signals as defined by a first spreading code chip sequence of a plurality of spreading code chip sequences;
wherein a second transmitter of the plurality of transmitters is configured to generate modulated radio signals as defined by a second spreading code chip sequence of the plurality of spreading code chip sequences; and
wherein a first receiver of the plurality of receivers is configured to process received radio signals as defined by at least the first and second spreading code chip sequences of the plurality of spreading code chip sequences.
14. The radar sensing system of claim 13 , wherein both the plurality of transmitters and the plurality of receivers are configured to receive the spreading code chip sequences from a same source.
15. The radar sensing system of claim 14 further comprising a programmable code generation unit configured to generate the spreading code chip sequences received by both the plurality of transmitters and the plurality of receivers.
16. The radar sensing system of claim 14 , wherein the source is configured to generate a plurality of different spreading code chip sequences.
17. The radar sensing system of claim 14 , wherein the programmable code generation unit comprises a control processor and a plurality of feedback shift registers, and wherein the control processor is operable to configure the plurality of feedback shift registers with any set of feedback connections.
18. The radar sensing system of claim 17 , wherein the programmable code generation unit also comprises logic configured to alter the output of the feedback shift registers in order to alter properties of spreading code chip sequences produced by the feedback shift registers, and wherein the logic is further configured to alter the output of the feedback shift registers to balance the DC properties of the spreading code chip sequences, such that a sum of code chip values of 1 and 0 is below a DC threshold value.
19. The radar sensing system of claim 17 , wherein the programmable code generation unit further comprises a memory configured to store spreading code chip sequences, such that the control processor is configured to select corresponding spreading code chip sequences from the memory for each transmitter of the plurality of transmitters.
20. The radar sensing system of claim 19 , wherein the memory is configured to store a first spreading code chip sequence, and wherein the programmable code generation unit is configured to output the first spreading code chip sequence for a first transmitter of the plurality of transmitters, and further configured to output delayed versions of the first spreading code chip sequence for each of the other transmitters of the plurality of transmitters.