US 7,579,839 B2
Metal detector
Bruce Halcro Candy, Basket Range (Australia)
Assigned to Minelab Electronics Pty Limited, Torrensville (Australia)
Appl. No. 11/576,467
PCT Filed Nov. 02, 2005, PCT No. PCT/AU2005/001683
§ 371(c)(1), (2), (4) Date Apr. 01, 2007,
PCT Pub. No. WO2006/047822, PCT Pub. Date May 11, 2006.
Claims priority of application No. 2004906301 (AU), filed on Nov. 03, 2004.
Prior Publication US 2008/0094065 A1, Apr. 24, 2008
Int. Cl. G01V 3/11 (2006.01); G01V 3/08 (2006.01)
U.S. Cl. 324—326  [324/228; 324/337] 4 Claims
OG exemplary drawing
 
1. A metal detector used for detecting a metallic target in a soil including:
a. transmit electronics having a plurality of switches to generate a switched voltage signal, the waveform of the switched voltage signal being one of predetermined repeating multi-period rectangular waveforms;
b. a transmit coil connected to the transmit electronics to receive the switched voltage signal and to generate a transmitted magnetic field for transmission;
c. a receive coil to receive a received magnetic field and to provide a received signal induced by the received magnetic field; and
d. receive electronics connected to the receive coil to process the received signal, the processing including a synchronous demodulation of the received signal using one of predetermined substantially sine-wave weighted synchronous demodulation profiles associated with a corresponding predetermined repeating multi-period rectangular waveform; the profiles being selectable by an operator; and a result of the synchronous demodulation is further processed to provide an indicator output signal in real time, the indicator output signal including a signal indicative of the presence of a metallic target in the soil.