A wireless handheld or portable electronic device comprising: a slim radiating system configured to transmit and receive electromagnetic wave signals in a first frequency region, the slim radiating system comprising a slim radiating structure, a radio-frequency system, a first internal conductive path and a first external conductive path; the slim radiating structure comprises a first booster bar and a ground plane layer; the first booster bar comprises a single standard layer of dielectric material including a top and a bottom conductive surface electrically connected, said conductive top and bottom surface being formed by conductive material printed or deposited in the top and bottom surface of the dielectric material and said conductive surfaces being electrically connected by at least one via, the first booster bar being further characterized by a slim width factor greater than 3 and a slim height factor greater than 3, wherein the slim width factor characterizes the ratio between the length and the width of the booster bar, and the slim height factor characterizes the ratio between the length and the height of the booster bar, the first booster bar being separated from the ground plane layer by a gap and characterized by a location factor in a range of 0.3 to 1.8, wherein the location factor is a ratio between the width of the booster bar and the gap; the first booster bar fits in an imaginary sphere having a diameter smaller than 1/3 of a radiansphere having a radius equal to a free-space wavelength corresponding to a lowest frequency of the first frequency region, divided by two times π (pi); the first internal conductive path couples the first booster bar to the radio-frequency system; and the radio-frequency system comprises a first matching circuit configured to provide impedance matching within the first frequency region at the first external conductive path, wherein the slim radiating system is configured to transmit and receive electromagnetic wave signals in a second frequency region, wherein a lowest frequency of the second frequency region is at a frequency higher than a highest frequency of the first frequency region; and the first matching circuit is further configured to provide impedance matching within the second frequency region at the first external conductive path, wherein the first frequency region comprises an 824-960MHz frequency range and the second frequency region comprises a 1710-2170MHz frequency range, and wherein a maximum size of the first booster bar is smaller than 1/15 of the free-space wavelength corresponding to a lowest frequency of the first frequency region. a slim radiating system configured to transmit and receive electromagnetic wave signals in a first frequency region, the slim radiating system comprising a slim radiating structure, a radio-frequency system, a first internal conductive path and a first external conductive path; the slim radiating structure comprises a first booster bar and a ground plane layer; the first booster bar comprises a single standard layer of dielectric material including a top and a bottom conductive surface electrically connected, said conductive top and bottom surface being formed by conductive material printed or deposited in the top and bottom surface of the dielectric material and said conductive surfaces being electrically connected by at least one via, the first booster bar being further characterized by a slim width factor greater than 3 and a slim height factor greater than 3, wherein the slim width factor characterizes the ratio between the length and the width of the booster bar, and the slim height factor characterizes the ratio between the length and the height of the booster bar, the first booster bar being separated from the ground plane layer by a gap and characterized by a location factor in a range of 0.3 to 1.8, wherein the location factor is a ratio between the width of the booster bar and the gap; the first booster bar fits in an imaginary sphere having a diameter smaller than 1/3 of a radiansphere having a radius equal to a free-space wavelength corresponding to a lowest frequency of the first frequency region, divided by two times π (pi); the first internal conductive path couples the first booster bar to the radio-frequency system; and the radio-frequency system comprises a first matching circuit configured to provide impedance matching within the first frequency region at the first external conductive path, wherein the slim radiating system is configured to transmit and receive electromagnetic wave signals in a second frequency region, wherein a lowest frequency of the second frequency region is at a frequency higher than a highest frequency of the first frequency region; and the first matching circuit is further configured to provide impedance matching within the second frequency region at the first external conductive path, wherein the first frequency region comprises an 824-960MHz frequency range and the second frequency region comprises a 1710-2170MHz frequency range, and wherein a maximum size of the first booster bar is smaller than 1/15 of the free-space wavelength corresponding to a lowest frequency of the first frequency region.