Abstract: A hand-held metal detector coil, including a coil housing which houses aggregate transmit windings and aggregate receive windings. The aggregate transmit windings include a major group of transmit windings that includes a first transmit winding, and the aggregate receive windings include a major group of receive windings that includes a first receive winding; the coil further includes a minor group of windings to null the aggregate receive windings with respect to the aggregate transmit windings. In an absence of external influences, a mutual inductance coupling coefficient between the aggregate receive windings and the aggregate transmit windings, kTR, is <0.03.

Abstract: Provided is a method for detecting a metal target in soil using a metal detector including the steps of generating a transmit magnetic field for transmission into the soil using a transmit winding based on a transmit signal; receiving a first receive magnetic field using the transmit winding during a receive period to produce a first receive signal; and receiving a second receive magnetic field using a receive winding during the receive period to produce a second receive signal. The transmit winding and the receive winding are separated spatially; and producing an indicator output signal based on the first receive signal, the second receive signal and at least one synchronous demodulation function. The first receive signal includes first parameters that define a first transfer function transforming the first receive magnetic field into the first receive signal.

Abstract: Provided is a method to detect a target using a metal detector. The method includes transmitting a repeating sequence of transmitted magnetic field into an environment. The repeating sequence of transmitted magnetic field is generated by a repeating sequence of transmitted electrical current flowing through a transmit inductive winding such that the repeating sequence of transmitted electrical current includes at least a first period of rapid change of current, followed by a first period of non-zero approximately constant current. A transition time between the first period of rapid change of current and the first period of non-zero approximately constant current is controlled by a first value of an electrical current flowing through the transmit inductive winding during the first period of rapid change of current.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: A method for detecting a target using a metal detector by producing at least two different modulated audio tones, by modulating a first audio tone with a first stereo audio modulator signal and modulating a second audio tone with a second stereo audio modulator signal; and applying at least the first audio tone to a left side of an audio stereo target indicator indicative of the target, and applying at least the second audio tone to a right side of the audio stereo target indicator. The modulating of the first audio tone and modulating of the second audio tone, includes one or more of the following; a modulation of a volume of a tone, a modulation of a pitch of a tone, a modulation of relative harmonics ratios of a tone, a modulation of a chord richness of a tone.

Abstract: An antenna of a handheld metal detector for detecting a target in a soil, the antenna including a housing including a bottom plane for facing the soil; two lateral sides; a front side; and a rear side; wherein the lateral sides, the front side and rear side are with respect to a user of the handheld metal detector holding and operating the handheld metal detector to detect the target in the soil; and at least one winding within the housing. A mean distance of conductors of the at least one winding near at least one of the two lateral sides of the housing is closer to the bottom plane than a mean distance of conductors of the at least one winding near at least one of the front side and rear side of the housing.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: A winding of an antenna of a metal detector, the winding includes multi-turn wire with both ends connected to the metal detector; and at least one resistive component for connecting a first part of the winding to a second part of the winding. The first part or the second part are not both ends of the winding. The resistive component is configured to damp an internal resonance of the winding with an order greater than 1.

Abstract: Provided is a method for detecting a metal target in soil using a metal detector including the steps of generating a transmit magnetic field for transmission into the soil using a transmit winding based on a transmit signal; receiving a first receive magnetic field using the transmit winding during a receive period to produce a first receive signal; and receiving a second receive magnetic field using a receive winding during the receive period to produce a second receive signal. The transmit winding and the receive winding are separated spatially; and producing an indicator output signal based on the first receive signal, the second receive signal and at least one synchronous demodulation function. The first receive signal includes first parameters that define a first transfer function transforming the first receive magnetic field into the first receive signal.

Abstract: A metal detector for detecting a target, the metal detector including: a transmitter for transmitting a transmitted magnetic field; a receiver, including a winding with a plurality of turns, for receiving a magnetic field; and a receive electronics connected to the winding for receiving signals from the winding. The receiver further includes an electrostatic screen covering at least part of the winding. The electrostatic screen is connected to an electronic circuit to receive signals from the receiver to reduce an effective capacitance presented by the electrostatic screen to the winding.

Abstract: An antenna of a handheld metal detector for detecting a target in a soil, the antenna including a housing including a bottom plane for facing the soil; two lateral sides; a front side; and a rear side; wherein the lateral sides, the front side and rear side are with respect to a user of the handheld metal detector holding and operating the handheld metal detector to detect the target in the soil; and at least one winding within the housing. A mean distance of conductors of the at least one winding near at least one of the two lateral sides of the housing is closer to the bottom plane than a mean distance of conductors of the at least one winding near at least one of the front side and rear side of the housing.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: A metal detector, includes a transmitter for transmitting a repeating sequence of transmit magnetic field, each of the sequence includes a period of changing or constant non-zero transmit magnetic field, immediately followed by period of rapid change of transmit magnetic field, immediately followed by a period of substantially constant or zero transmit magnetic field; a receive coil; and a damping resistor. An end of the receive coil is connected to one end of the damping resistor and the other end of the damping resistor is connectable to a circuit with a variable parameter. A signal is induced in the receive coil during the period of rapid change of transmit magnetic field, and the signal induced in the receive coil decays at least at a termination of the period of rapid change of transmit magnetic field.

Abstract: A winding of an antenna of a metal detector, the winding includes multi-turn wire with both ends connected to the metal detector; and at least one resistive component for connecting a first part of the winding to a second part of the winding. The first part or the second part are not both ends of the winding. The resistive component is configured to damp an internal resonance of the winding with an order greater than 1.

Abstract: A metal detector for detecting a target, the metal detector including: a transmitter for transmitting a transmitted magnetic field; a receiver, including a winding with a plurality of turns, for receiving a magnetic field; and a receive electronics connected to the winding for receiving signals from the winding. The receiver further includes an electrostatic screen covering at least part of the winding. The electrostatic screen is connected to an electronic circuit to receive signals from the receiver to reduce an effective capacitance presented by the electrostatic screen to the winding.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: A method for detecting an electrically conductive target in soil using a metal detector, including the steps of: processing a receive signal using at least two different functions for producing at least two processed signals, each of the processed signals is at least partly insensitive to at least one unwanted signal due to the soil or an electromagnetic interference noise; determining a noise level of each of the at least two processed signals for producing at least two noise signals; and producing, from at least one of the at least two processed signals, an indicator output signal indicative of the presence of the electrically conductive target when the electrically conducting target is within the influence of a transmit magnetic field transmitted by the metal detector; wherein the step of producing an indicator output signal is dependent upon characteristics of the at least two noise signals.

Abstract: A metal detector, includes a transmitter for transmitting a repeating sequence of transmit magnetic field, each of the sequence includes a period of changing or constant non-zero transmit magnetic field, immediately followed by period of rapid change of transmit magnetic field, immediately followed by a period of substantially constant or zero transmit magnetic field; a receive coil; and a damping resistor. An end of the receive coil is connected to one end of the damping resistor and the other end of the damping resistor is connectable to a circuit with a variable parameter. A signal is induced in the receive coil during the period of rapid change of transmit magnetic field, and the signal induced in the receive coil decays at least at a termination of the period of rapid change of transmit magnetic field.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: A method for reducing unwanted signals, due to a back emf decay, within a receive signal received by a receive coil of a metal detector during a demodulation of the receive signal after a transmission by a transmit coil of the metal detector, including controlling a T/R switch to control a characteristic of the back emf decay to reduce a duration of the period of the back emf decay.