System for generating accurate reference signals for time-of-arrival based time synchronization

1. A system for generating a self-receive signal comprising:

a signal generator;

a first signal processor;

a second signal processor;

an antenna;

a first passive coupling device:

comprising a first input port electromagnetically coupled to the signal generator;

comprising a first transmitted port;

comprising a first coupled port electromagnetically coupled to the first signal processor; and

characterized by a first phase balance between the first transmitted port and the first coupled port; and

a second passive coupling device:

comprising a second input port electromagnetically coupled to the antenna;

comprising a second transmitted port electromagnetically coupled to the first transmitted port;

comprising a second coupled port electromagnetically coupled to the second signal processor; and

characterized by a second phase balance between the second transmitted port and the second coupled port substantially similar to the first phase balance.

2. The system of claim 1 :

further comprising a self-receive chain:

electromagnetically coupling the signal generator to the first signal processor via the first passive coupling device; and

configured to back-couple a transmitted signal from the signal generator for reception at the first signal processor as a self-receive signal; and

further comprising a receive chain:

electromagnetically coupling the antenna to the second signal processor via the second passive coupling device; and

configured to couple a signal received at the antenna for reception at the second signal processor.

3. The system of claim 2 :

further comprising a clock; and

wherein the first signal processor is further configured to, subsequent to reception of the self-receive signal, calculate a time-of-arrival of the self-receive signal based on the clock, the time-of-arrival approximating a time-of-departure for the transmitted signal according to the clock.

4. The system of claim 2 :

wherein the self-receive chain is further configured to back-couple the transmitted signal from the signal generator for reception at the first signal processor with a first group delay; and

wherein the receive chain is further configured to couple the signal received at the antenna for reception at the second signal processor with a second group delay substantially similar to the first group delay.

5. The system of claim 1 :

further comprising a self-receive chain:

electromagnetically coupling the signal generator to the first signal processor via the first passive coupling device; and

characterized by a self-receive signal path length; and

further comprising a receive chain:

electromagnetically coupling the antenna to the second signal processor via the second passive coupling device; and

characterized by a receive signal path length substantially equal to the self-receive signal path length.

6. The system of claim 1 :

wherein the first signal processor comprises a first analog-to-digital converter configured to generate digital samples according to a timestamp counter; and

wherein the second signal processor comprises a second analog-to-digital converter configured to generate digital samples according to the timestamp counter.

7. The system of claim 1 :

a further comprising a power amplifier electromagnetically interposed between the signal generator and the first input port and characterized by a first group delay;

further comprising a self-receive chain:

electromagnetically coupling the signal generator to the first signal processor via the power amplifier and the first passive coupling device; and

configured to back-couple a transmitted signal from the signal generator for reception at the first signal processor effected by the first group delay; and

further comprising a transmit chain:

electromagnetically coupling the signal generator to the antenna via the first passive coupling device and the second passive coupling device; and

configured to couple the transmitted signal generated at the signal generator for transmission at the antenna effected by the first group delay.

8. The system of claim 1 :

further comprising an attenuator:

a electromagnetically interposed between the first coupled port and the first signal processor; and

characterized by a first group delay; and

further comprising a low-noise amplifier:

electromagnetically interposed between the second coupled port and the second signal processor; and

characterized by a second group delay substantially similar to the first group delay.

9. A system for generating a self-receive signal comprising:

a signal generator;

a signal processor;

an antenna;

a multiplexer comprising:

a self-receive signal port;

a receive signal port; and

an output port electromagnetically coupled to the signal processor;

a first passive coupling device:

comprising a first input port electromagnetically coupled to the signal generator;

comprising a first transmitted port;

comprising a first coupled port electromagnetically coupled to the self-receive signal port; and

characterized by a first phase balance between the first transmitted port and the first coupled port; and

a second passive coupling device:

comprising a second input port electromagnetically coupled to the antenna;

comprising a second transmitted port electromagnetically coupled to the first transmitted port;

comprising a second coupled port electromagnetically coupled to the receive signal port; and

characterized by a second phase balance between the second transmitted port and the second coupled port substantially similar to the first phase balance.

10. The system of claim 9 , further comprising a digital controller electromagnetically coupled to the multiplexer and configured to:

select the self-receive signal port during a transmit slot in a time-division multiple access frame; and

select the receive signal port during a receive slot in the time-division multiple access frame.

11. The system of claim 10 :

further comprising a self-receive chain:

electromagnetically coupling the signal generator to the signal processor via the first passive coupling device and the multiplexer; and

configured to back-couple a transmitted signal from the signal generator for reception at the signal processor as a self-receive signal during the transmit slot in the time-division multiple access frame; and

further comprising a receive chain:

electromagnetically coupling the antenna to the signal processor via the second passive coupling device and the multiplexer; and

configured to couple a signal received at the antenna for reception at the signal processor during the receive slot in the time-division multiple access frame.

12. The system of claim 11 :

further comprising a clock; and

wherein the first signal processor is further configured to, upon reception of the self-receive signal, calculate a time-of-arrival of the self-receive signal based on the clock, the time-of-arrival approximating a time-of-departure for the transmitted signal according to the clock.

13. The system of claim 9 :

further comprising a self-receive chain:

electromagnetically coupling the signal generator to the signal processor via the first passive coupling device and the multiplexer; and

defining a self-receive signal path length; and

further comprising a receive chain:

electromagnetically coupling the antenna to the signal processor via the second passive coupling device and the multiplexer; and

defining a receive signal path length substantially equal to the self-receive signal path length.

14. The system of claim 9 , further comprising a power amplifier electromagnetically interposed between the first transmitted port and the second transmitted port.

15. The system of claim 9 :

further comprising an attenuator:

electromagnetically interposed between the first coupled port and the self-receive signal port; and

defining a first group delay; and

further comprising a low-noise amplifier:

electromagnetically interposed between the second coupled port and the receive signal port; and

defining a second group delay substantially similar to the first group delay.

16. A system for generating a self-receive signal comprising:

a first signal generator;

a first antenna;

a first set of signal processors;

a first passive coupling device:

comprising a first input port electromagnetically coupled to the first signal generator;

comprising a first transmitted port;

comprising a first coupled port electromagnetically coupled to the first set of signal processors; and

characterized by a first phase balance between the first transmitted port and the first coupled port; and

a second passive coupling device:

comprising a second input port electromagnetically coupled to the first antenna;

comprising a second transmitted port electromagnetically coupled to the first transmitted port;

comprising a second coupled port electromagnetically coupled to the first set of signal processors; and

characterized by a second phase balance between the second transmitted port and the second coupled port substantially similar to the first phase balance.

17. The system of claim 16 :

further comprising a first node comprising:

the first signal generator;

the first antenna;

the first set of signal processors;

the first passive coupling device; and

the second passive coupling device;

further comprising a second node comprising:

a second signal generator;

a second antenna;

a second set of signal processors;

a third passive coupling device:

comprising a third input port electromagnetically coupled to the second signal generator;

comprising a third transmitted port;

comprising a third coupled port electromagnetically coupled to the second set of signal processors; and

characterized by a third phase balance between the third transmitted port and the third coupled port substantially similar to the first phase balance; and

a fourth passive coupling device:

comprising a fourth input port electromagnetically coupled to the second antenna;

comprising a fourth transmitted port electromagnetically coupled to the third transmitted port;

comprising a fourth coupled port electromagnetically coupled to the second set of signal processors; and

characterized by a fourth phase balance between the fourth transmitted port and the fourth coupled port substantially similar to the first phase balance; and

wherein the first node and the second node are configured to execute a two-way time synchronization protocol by:

at the first node:

transmitting a first synchronization signal; and

generating a first self-receive signal based on the first synchronization signal;

at the second node:

transmitting a second synchronization signal; and

generating a second self-receive signal based on the second synchronization signal;

at the first node:

calculating a first time-of-arrival of the first self-receive signal; and

calculating a second time-of-arrival of the second synchronization signal;

at the second node:

calculating a third time-of-arrival of the second self-receive signal; and

calculating a fourth time-of-arrival of the first synchronization signal; and

calculating a time bias and a propagation delay between the first node and the second node based on the first time-of-arrival, the second time-of-arrival, the third time-of-arrival, and the fourth time-of-arrival.

18. The system of claim 16 :

wherein the first set of signal processors comprises a first signal processor;

further comprising a multiplexer comprising:

a self-receive signal port;

a receive signal port; and

an output port electromagnetically coupled to the first signal processor;

wherein the first passive coupling device comprises the first coupled port electromagnetically coupled to the self-receive signal port;

wherein the second passive coupling device comprises the second coupled port electromagnetically coupled to the receive signal port; and

further comprising a digital controller electromagnetically coupled to the multiplexer and configured to:

select the self-receive signal port during a transmit slot in a time-division multiple access frame; and

select the receive signal port during a receive slot in the time-division multiple access frame.

19. The system of claim 16 :

wherein the first set of signal processors comprises a first signal processor;

further comprising a power combiner comprising:

a self-receive signal port;

a receive signal port; and

an output port electromagnetically coupled to the first signal processor;

wherein the first passive coupling device comprises the first coupled port electromagnetically coupled to the self-receive signal port; and

wherein the second passive coupling device comprises the second coupled port electromagnetically coupled to the receive signal port.

20. The system of claim 16 :

wherein the first set of signal processors comprises:

a first signal processor; and

a second signal processor;

wherein the first passive coupling device comprises the first coupled port electromagnetically coupled to the first signal processor in the first set of signal processors; and

wherein the second passive coupling device comprises the second coupled port electromagnetically coupled to the second signal processor in the first set of signal processors.