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US 8,013,595 B2Granted
AC magnetic tracking system with phase locking
AssigneeALKEN Inc.
InventorsHerbert R. Jones, Robert F. Higgins, Henry E. Himberg
Life of this patent
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Abstract
Plural transmitter coils of a magnetic locating system are driven with widely-separated main frequencies. One of the transmitter coils is also driven with a marker frequency close to the main frequency applied to that coil. The receiver determines a phase relationship with the transmitter based on the main and marker frequencies, so that the receiver does not suffer from phase ambiguity. The main and marker frequencies may interfere with one another, and the receiver may correct for such interference based on known characteristics of the signals at the main and marker frequencies.
Claims31
Magnetic locating apparatus comprising:
- (a) a transmitter including a plurality of co-located orthogonal transmitter coils and a transmitter circuit operative to apply a signal to each transmitter coil including a main sinusoidal component having a frequency fB, where B is an index denoting one of said transmitter coils, fB being different for different transmitter coils, the transmitter circuit also being operative to drive a particular one of the transmitter coils having a particular index B* with a sinusoidal marker component having a known amplitude and phase relationship to the main component transmitted by the same coil, the marker component having a frequency f′B* such that the difference between fB* and f′B* is smaller than the difference between any two of the main frequencies fB;
- (b) a receiver including a plurality of co-located orthogonal sensor coils to yield a plurality of sensor signals responsive to magnetic fields sent by the transmitter, the receiver including a receiver circuit operative to process the sensor signals to derive separate components SAB in each sensor signal at each main frequency fB where A is an index denoting one of the sensor coils and to derive a separate component S′AB* in at least one sensor signal at a marker frequency f′B*, the receiver circuit also being operative to determine the phase of at least one component in at least one sensor signal from sensor signal components SA*B* and S′A*B*, where A* is a particular value of A and to determine the position of the sensor coils relative to the transmitter coils based on the determined phase and on the components SAB.
A method of locating comprising the steps of:
- (a) sending a plurality of magnetic signals from a plurality of co-located orthogonal transmitter coils, each of such signals including a main sinusoidal component having a different frequency fB, where B is an index denoting one of said transmitter coils, the signal from a particular one of the transmitter coils having a particular index B* also including a sinusoidal marker component having a known amplitude and phase relationship to the main component transmitted by the same coil, the marker component having a frequency f′B* such that the difference between fB* and f′B* is smaller than the difference between any two of the main frequencies fB;
- (b) receiving the plurality of magnetic signals using a plurality of co-located orthogonal sensor coils to yield a plurality of sensor signals;
- (c) processing the sensor signals to derive separate components SAB in each sensor signal at each main frequency fB where A is an index denoting one of the sensor coils and to derive a separate component S′AB* in at least one sensor signal at a marker frequency f′B*;
- (d) determining the phase of at least one component in at least one sensor signal from sensor signal components SA*B* and S′A*B*, where A* is a particular value of A;
- and
- (e) determining the position of the sensor coils relative to the transmitter coils based on the determined phase and on the components SAB.
3 more elements
A method of transmitting and receiving a sinusoidal signal including the steps of:
- (a) transmitting a composite signal including first and second sinusoidal components at first and second frequencies, said first and second sinusoidal components having a fixed phase and amplitude relationship;
- (b) receiving the composite signal;
- (c) sampling the received composite signal to provide time-domain data;
- (d) transforming the time-domain data to recover first and second recovered components;
- and
- (e) correcting the first and second recovered components based on the known relationships between the first and second components of said transmitted signal and known characteristics of the transformation to provide first and second corrected components at first and second frequencies.
3 more elements
Dependencies are inferred from the claim text.