Dual frequency ranging with calculated integer wavelength and phase difference
The embodiments described herein provide ranging capabilities in RF-opaque environments, such as a jungle, utilizing transponders located on a property line. In particular, the embodiments described herein provide for determining a distance to a property line from a ranging device. The transponders are located on the property line and are separated from each other by a known distance. The ranging device transmits RF signals to the transponders, and receives RF signals returned by the transponders on a different frequency. The ranging device uses information about the transmitted and received RF signals and the known distance to calculate a distance from the ranging device to the property line.
1 . A ranging system, comprising:
a range detector comprising:
circuitry configured to transmit a first Radio Frequency (RF) signal at a first frequency, and to receive a second RF signal at a second frequency from a transponder in response to the first RF signal; and
circuitry configured to calculate a distance to the transponder based on the first RF signal and the second RF signal by:
calculating an estimated distance based on an integer number of wavelengths between the transponder and the range detector;
calculating a sub-wavelength distance based on a phase difference between the first RF signal and the second RF signal; and
calculating the distance to the transponder based on a sum of the estimated distance and the sub-wavelength distance.
2 . The ranging system of claim 1 , wherein:
the second frequency is lower than the first frequency.
3 . The ranging system of claim 2 , further comprising:
the transponder configured to down-convert the first RF signal received from the range detector to the second frequency.
4 . The ranging system of claim 1 , wherein:
the circuitry is configured to modulate a code on the first RF signal.
5 . The ranging system of claim 1 , wherein:
the circuitry is configured to include an address of the transponder on the first RF signal.
6 . The ranging system of claim 1 , wherein:
the circuitry is configured to broadcast the first RF signal at the first frequency.
7 . The ranging system of claim 1 , wherein:
the first frequency and the second frequency are within a 70 centimeter band.
8 . The ranging system of claim 1 , wherein:
the range detector further comprises:
a user interface configured to provide information to a user regarding the distance.
9 . The ranging system of claim 8 , wherein:
the user interface comprises a visual display.
10 . The ranging system of claim 8 , wherein:
the user interface comprises a sound generating device.
11 . The ranging system of claim 8 , wherein:
the user interface comprises a vibration generating device.
12 . A method of operating a ranging system, the method comprising:
transmitting, from a range detector, a first Radio Frequency (RF) signal at a first frequency;
receiving, at the range detector, a second RF signal at a second frequency from a transponder in response to the first RF signal; and
calculating a distance from the range detector to the transponder based on the first RF signal and the second RF signal by:
calculating an estimated distance based on an integer number of wavelengths between the transponder and the range detector;
calculating a sub-wavelength distance based on a phase difference between the first RF signal and the second RF signal; and
calculating the distance to the transponder based on a sum of the estimated distance and the sub-wavelength distance.
13 . The method of claim 12 , wherein:
the second frequency is lower than the first frequency.
14 . The method of claim 13 , further comprising:
down-converting, at the transponder, the first RF signal received from the range detector to the second frequency.
15 . The method of claim 12 , further comprising:
modulating a code on the first RF signal.
16 . The method of claim 12 , further comprising:
including an address of the transponder on the first RF signal.
17 . The method of claim 12 , wherein:
the transmitting comprises broadcasting the first RF signal at the first frequency.
18 . The method of claim 12 , wherein:
the first frequency and the second frequency are within a 70 centimeter band.
19 . The method of claim 12 , further comprising:
providing, at the range detector, a visual display of the distance.
20 . A non-transitory computer readable medium embodying programmed instructions which, when executed by a processor of a range detector, are operable for performing a method comprising:
transmitting, from the range detector, a first Radio Frequency (RF) signal at a first frequency;
receiving, at the range detector, a second RF signal at a second frequency from a transponder in response to the first RF signal; and
calculating a distance from the range detector to the transponder based on the first RF signal and the second RF signal by:
calculating an estimated distance based on an integer number of wavelengths between the transponder and the range detector;
calculating a sub-wavelength distance based on a phase difference between the first RF signal and the second RF signal; and
calculating the distance to the transponder based on a sum of the estimated distance and the sub-wavelength distance.