Signal processing for driving antennas for a spacecraft or terrestrial vehicle
An antenna and receiver design is described herein that allows a spacecraft to safely and accurately perform an autonomous flight safety system, an ascent, an entry, a re-entry, a landing, and/or an orbit determination. For example, a spacecraft can be equipped with 180-degree dual-opposed antennas and two receivers. A signal captured by a first antenna can be routed to a secondary radio frequency (RF) of the first receiver and to a combiner. A signal captured by a second antenna can be routed to a secondary RF of the second receiver and to the combiner. The mixer can perform the phase combination operation on the signals captured by the first receiver and the second receiver to produce a phase combined signal, and can route the phase combined signal to the primary RF of the first receiver and to the primary RF of the second receiver.
1 . A navigation system comprising:
a first antenna positioned in a first direction;
a second antenna positioned in a second direction that is about 180 degrees from the first direction;
a combiner coupled to the first antenna and the second antenna, the combiner configured to combine a first signal received from the first antenna with a second signal received from the second antenna to form a combined signal;
a first receiver coupled to the first antenna and the combiner, the first receiver having a first port configured to receive the combined signal from the combiner and a second port configured to receive the first signal from the first antenna;
a second receiver coupled to the second antenna and the combiner, the second receiver having a first port configured to receive the combined signal from the combiner and a second port configured to receive the second signal from the second antenna; and
a processing unit coupled to the first receiver and the second receiver, the processing unit configured to:
estimate a clock difference between the first receiver and the second receiver using the combined signal,
time-synchronize the first signal with the second signal using the estimated clock difference, and
determine a navigation parameter for a spacecraft using the time-synchronized first and second signals.
2 . The navigation system of claim 1 , wherein the processing unit is further configured to:
single-difference a phase-combined pseudorange of the second receiver from a phase-combined pseudorange of the first receiver to form a single-difference phase-combined pseudorange; and
remove one or more outliers from the single-difference phase-combined pseudorange to form a modified single-difference phase-combined pseudorange.
3 . The navigation system of claim 2 , wherein the processing unit is further configured to:
double-difference a phase-combined carrier phase of the second receiver from a phase-combined carrier phase of the first receiver to form a double-difference phase-combined carrier phase; and
remove one or more outliers from the double-difference phase-combined carrier phase to form a modified double-difference phase-combined carrier phase.
4 . The navigation system of claim 3 , wherein the processing unit is further configured to combine the modified single-difference phase-combined pseudorange with the modified double-difference phase-combined carrier phase to estimate the clock difference.
5 . The navigation system of claim 1 , wherein the processing unit is further configured to determine one of position, velocity, or timing of the spacecraft for a landing maneuver using the combined signal.
6 . The navigation system of claim 1 , wherein the combiner comprises one of a Wilkinson, a resistive, or a hybrid combiner.
7 . The navigation system of claim 1 , wherein the combined signal comprises a phase combined signal.
8 . The navigation system of claim 1 , wherein the navigation parameter comprises one of position, velocity, or timing of the spacecraft.
9 . A method comprising:
combining a first signal received from a first antenna with a second signal received from a second antenna to form a combined signal, wherein the first antenna is positioned in a first direction, wherein the second antenna is positioned in a second direction that is about 180 degrees from the first direction, wherein a first receiver is coupled to the first antenna, wherein the first receiver has a first port configured to receive the combined signal and a second port configured to receive the first signal from the first antenna, wherein a second receiver is coupled to the second antenna, wherein the second receiver has a first port configured to receive the combined signal and a second port configured to receive the second signal from the second antenna;
estimating a clock difference between the first receiver and the second receiver using the combined signal;
time-synchronizing the first signal with the second signal using the estimated clock difference; and
determining a navigation parameter for a spacecraft using the time-synchronized first and second signals.
10 . The method of claim 9 , wherein estimating a clock difference further comprises:
single-differencing a phase-combined pseudorange of the second receiver from a phase-combined pseudorange of the first receiver to form a single-difference phase-combined pseudorange; and
removing one or more outliers from the single-difference phase-combined pseudorange to form a modified single-difference phase-combined pseudorange.
11 . The method of claim 10 , wherein estimating a clock difference further comprises:
double-differencing a phase-combined carrier phase of the second receiver from a phase-combined carrier phase of the first receiver to form a double-difference phase-combined carrier phase; and
removing one or more outliers from the double-difference phase-combined carrier phase to form a modified double-difference phase-combined carrier phase.
12 . The method of claim 11 , wherein estimating a clock difference further comprises combining the modified single-difference phase-combined pseudorange with the modified double-difference phase-combined carrier phase to estimate the clock difference.
13 . The method of claim 9 , further comprising determining one of position, velocity, or timing of the spacecraft for a landing maneuver using the combined signal.
14 . The method of claim 9 , wherein the combined signal comprises a phase combined signal.
15 . The method of claim 9 , wherein the navigation parameter comprises one of position, velocity, or timing of the spacecraft.
16 . A non-transitory, computer-readable medium comprising computer-executable instructions for controlling a spacecraft, wherein the computer-executable instructions, when executed by a computer system, cause the computer system to:
estimate a clock difference between a first receiver and a second receiver using a combined signal, wherein the combined signal is a combination of a first signal received from a first antenna and a second signal received from a second antenna, wherein the first antenna is positioned in a first direction, wherein the second antenna is positioned in a second direction that is about 180 degrees from the first direction, wherein the first receiver is coupled to the first antenna, wherein the first receiver has a first port configured to receive the combined signal and a second port configured to receive the first signal from the first antenna, wherein the second receiver is coupled to the second antenna, wherein the second receiver has a first port configured to receive the second signal from the second antenna and a second port configured to receive the combined signal;
time-synchronize the first signal with the second signal using the estimated clock difference; and
determine a navigation parameter for a spacecraft using the time-synchronized first and second signals.
17 . The non-transitory, computer-readable medium of claim 16 , wherein the computer-executable instructions, when executed, further cause the computer system to:
single-difference a phase-combined pseudorange of the second receiver from a phase-combined pseudorange of the first receiver to form a single-difference phase-combined pseudorange; and
remove one or more outliers from the single-difference phase-combined pseudorange to form a modified single-difference phase-combined pseudorange.
18 . The non-transitory, computer-readable medium of claim 17 , wherein the computer-executable instructions, when executed, further cause the computer system to:
double-difference a phase-combined carrier phase of the second receiver from a phase-combined carrier phase of the first receiver to form a double-difference phase-combined carrier phase; and
remove one or more outliers from the double-difference phase-combined carrier phase to form a modified double-difference phase-combined carrier phase.
19 . The non-transitory, computer-readable medium of claim 18 , wherein the computer-executable instructions, when executed, further cause the computer system to combine the modified single-difference phase-combined pseudorange with the modified double-difference phase-combined carrier phase to estimate the clock difference.
20 . The non-transitory, computer-readable medium of claim 16 , wherein the computer-executable instructions, when executed, further cause the computer system to determine one of position, velocity, or timing of the spacecraft for a landing maneuver using the combined signal.