Method of eliminating resonances in multiband radiating arrays
A multiband radiating array according to the present invention includes a vertical column of lower band dipole elements and a vertical column of higher band dipole elements. The lower band dipole elements operate at a lower operational frequency band, and the lower band dipole elements have dipole arms that combine to be about one half of a wavelength of the lower operational frequency band midpoint frequency. The higher band dipole elements operate at a higher frequency band, and the higher band dipole elements have dipole arms that combine to be about three quarters of a wavelength of the higher operational frequency band midpoint frequency. The higher band radiating elements are supported above a reflector by higher band feed boards. A combination of the higher band feed boards and higher band dipole arms do not resonate in the lower operational frequency band.
1. A multiband radiating array, comprising:
a) at least one vertical column of low band dipole elements having a first operational frequency band;
b) at least one vertical column of high band dipole elements having a second operational frequency band that is higher than the first operational frequency band and that has a midpoint frequency, the high band dipole elements having high band dipole arms that combine to be about three quarters of a wavelength of the midpoint frequency of the second operational frequency band, the high band dipole elements being supported about one quarter of a wavelength of the second operational frequency band above a planar reflector by a respective one of a plurality of the high band feed boards;
wherein each combination of a respective one of the high band feed boards and a respective one of the high band dipole arms does not resonate in the first operational frequency band.
2. The multiband radiating array of claim 1 , wherein the high band dipole elements have an impedance of about 400Ω-600Ω in the second operational frequency band.
3. The multiband radiating array of claim 1 , wherein the first operational frequency band is about 694 MHz-960 MHz.
4. The multiband radiating array of claim 1 , wherein the first operational frequency band is about 790 Mhz-960 MHz and the second operational frequency band is about 1710 Mhz-2170 MHz.
5. The multiband radiating array of claim 1 , wherein the second operational frequency band is about 1710 MHz-2170 MHz.
6. The multiband radiating array of claim 1 , wherein the second operational frequency band is about 1710 Mhz-2700 MHz.
7. The multiband radiating array of claim 1 , wherein the second operational frequency band is about twice the first operational frequency band.
8. The multiband radiating array of claim 1 , wherein the dipole arms of the high band dipole elements are capacitively coupled to feed lines on respective ones of the plurality of the high band feed boards.
9. The multiband radiating array of claim 1 , wherein each high band feed board comprises a balun and a pair of feed lines, wherein each feed line is capacitively coupled to an inductive section, and each inductive section is capacitively coupled to a respective high band dipole arm.
10. The multiband radiating array of claim 1 , wherein a length of each high band dipole arm is selected so that a combination of the high band dipole arm and the high band feed board that supports it does not resonate in the first operational frequency band.
11. A multiband radiating array, comprising:
a) at least one vertical column of low band dipole elements having a first operational frequency band;
b) at least one vertical column of high band dipole elements having a second operational frequency band that is higher than the first operational frequency band and that has a midpoint frequency, each high band dipole element having a pair of high band dipole arms that combine to be about three quarters of a wavelength of the midpoint frequency of the second operational frequency band, the high band dipole elements being supported above a planar reflector by respective ones of a plurality of high band feed boards;
wherein each high band feed board comprises a balun and a pair of feed lines, wherein each feed line is capacitively coupled to a respective one of a plurality of inductive sections, and each inductive section is capacitively coupled to a respective high band dipole arm, and
wherein a length of each high band dipole arm is selected so that a combination of the high band dipole arm and the high band feed board that supports it does not resonate in the first operational frequency band.
12. The multiband radiating array of claim 11 , wherein the second operational frequency band is about twice the first operational frequency band.
13. A radiating element, comprising:
a. first and second dipole arms, the first dipole arm and the second dipole arm each having a respective capacitive coupling area; and
b. a feedboard having a balun and first and second matching circuits coupled to the balun, the first matching circuit being coupled to the first dipole arm and the second matching circuit being coupled to the second dipole arm,
wherein the first matching circuit comprises a first capacitive element, a first inductor and a second capacitive element that are arranged electrically in series, the second capacitive element being coupled to the first dipole arm,
wherein the second matching circuit comprises a third capacitive element, a second inductor and a fourth capacitive element that are arranged electrically in series, the fourth capacitive element being coupled to the second dipole arm, and
wherein the second capacitive element and the capacitive coupling area of the first dipole arm combine to form a capacitor that blocks out of band currents.
14. The radiating element of claim 13 , wherein the first capacitive element and an area of a stalk coupled to the balun comprise parallel plates of a capacitor and a substrate of the feedboard comprises a dielectric of a capacitor that includes the first capacitive element.
15. The radiating element of claim 13 , wherein the radiating element comprises a cross dipole radiating element.
16. The radiating element of claim 13 , wherein a combined length of the first and second dipole arms is between 0.6 wavelengths and 0.9 wavelengths of an operational frequency band of the radiating element.
17. The radiating element of claim 13 , wherein a combined length of the first and second dipole arms is about three quarters of a wavelength of a midpoint frequency of an operational frequency band of the radiating element.