A substrate for a dual interface smartcard, the substrate comprising: a contact pad module receiving portion; an auxiliary module receiving portion; and a conductor pattern including: an antenna coil having a first end and a second end; a first set of connectors arranged in the contact pad module receiving portion for electrical connection with corresponding connectors (47,49) of a contact pad module, the first set of connectors including a GND connector for electrical connection with a GND connector of the contact pad module, and a VCC connector for electrical connection with a VCC connector of the contact pad module; a second set of connectors arranged in the auxiliary module receiving portion for electrical connection with corresponding connectors (55,57) of an auxiliary module, the second set of connectors including a GND connector for electrical connection with a GND connector of the auxiliary module, and a VCC connector for electrical connection with a VCC connector of the auxiliary module; and leads connecting connectors in the first set with connectors in the second set, the leads at least connecting the GND connector in the first set of connectors with the GND connector in the second set of connectors, and connecting the VCC connector in the first set of connectors with the VCC connector in the second set of connectors, characterized in that one of the GND connector and the VCC connector in the first set of connectors is conductively connected to one of the first end and the second end of the antenna coil. a contact pad module receiving portion; an auxiliary module receiving portion; and a conductor pattern including: an antenna coil having a first end and a second end; a first set of connectors arranged in the contact pad module receiving portion for electrical connection with corresponding connectors (47,49) of a contact pad module, the first set of connectors including a GND connector for electrical connection with a GND connector of the contact pad module, and a VCC connector for electrical connection with a VCC connector of the contact pad module; a second set of connectors arranged in the auxiliary module receiving portion for electrical connection with corresponding connectors (55,57) of an auxiliary module, the second set of connectors including a GND connector for electrical connection with a GND connector of the auxiliary module, and a VCC connector for electrical connection with a VCC connector of the auxiliary module; and leads connecting connectors in the first set with connectors in the second set, the leads at least connecting the GND connector in the first set of connectors with the GND connector in the second set of connectors, and connecting the VCC connector in the first set of connectors with the VCC connector in the second set of connectors, an antenna coil having a first end and a second end; a first set of connectors arranged in the contact pad module receiving portion for electrical connection with corresponding connectors (47,49) of a contact pad module, the first set of connectors including a GND connector for electrical connection with a GND connector of the contact pad module, and a VCC connector for electrical connection with a VCC connector of the contact pad module; a second set of connectors arranged in the auxiliary module receiving portion for electrical connection with corresponding connectors (55,57) of an auxiliary module, the second set of connectors including a GND connector for electrical connection with a GND connector of the auxiliary module, and a VCC connector for electrical connection with a VCC connector of the auxiliary module; and leads connecting connectors in the first set with connectors in the second set, the leads at least connecting the GND connector in the first set of connectors with the GND connector in the second set of connectors, and connecting the VCC connector in the first set of connectors with the VCC connector in the second set of connectors, characterized in that one of the GND connector and the VCC connector in the first set of connectors is conductively connected to one of the first end and the second end of the antenna coil.