Four-port omnidirectional antenna
A four-port omnidirectional antenna comprising a dielectric resonator, a first substrate and a second substrate. The first substrate comprising two sets of feed lines adapted for providing two transverse magnetic (TM) modes, one of which is provided in a higher order. The second substrate also comprises two sets of feed lines adapted for providing two transverse electric (TE) modes, one of which is provided in higher order. The dielectric resonator, the first substrate and the second substrate are stacked with each other to form a double-layer printed circuit board (PCB), and the feed lines are configured to isolate fields excited by each of the two TM modes and the two TE modes, thereby enabling independent operation between each of the two TM modes and the two TE modes.
1 . A four-port omnidirectional antenna comprising:
(i) a dielectric resonator,
(ii) a first substrate in contact with the dielectric resonator, comprising a first set of feed lines adapted for providing a fundamental transverse magnetic (TM) mode in a lower frequency band, and a second set of feed lines adapted for providing a high order TM mode in a higher frequency band;
(iii) a second substrate in contact with the first substrate, comprising a third set of feed lines adapted for providing a fundamental transverse electric (TE) mode in the lower frequency band, and a fourth set of feed lines adapted for providing a high order TE mode in the higher frequency band;
wherein the first, second, third and fourth set of feed lines are configured to isolate fields excited by each of the two TM modes and the two TE modes, thereby enabling independent operation between each of the two TM modes and the two TE modes.
2 . The four-port omnidirectional antenna according to claim 1 , wherein the antenna is a duplex antenna adapted to receive and transmit data simultaneously at any two of the two TM modes and two TE modes at two distinct frequency bands.
3 . The four-port omnidirectional antenna according to claim 2 , wherein the two distinct frequency bands include a first frequency band of 1.8 Ghz and a second frequency band of 3.9 Ghz.
4 . The four-port omnidirectional antenna according to claim 1 , wherein the first set of feed lines is electrically interconnected and fed by a first power divider to form a first feed network.
5 . The four-port omnidirectional antenna according to claim 4 , wherein the first power divider is disposed radially between the third set of feed lines and the fourth set of feed lines on the second substrate, and comprises circumferentially extending arc strips with cascading structures along the radial direction adapted to provide a first order and a second order of power division.
6 . The four-port omnidirectional antenna according to claim 5 , wherein the circumferentially extending arc strips include a first arc strip adapted to provide the first order of power division, wherein the first arc strip has a circumferential span of 180 degrees.
7 . The four-port omnidirectional antenna according to claim 6 , further comprising a filter structure comprising an arc adapted to eliminate coupling between the first set of feed lines and the second set of feed lines, wherein the arc has a dimension comparable to a wavelength associated with the frequency band of the high order TM mode.
8 . The four-port omnidirectional antenna according to claim 4 , wherein the first set of feed lines comprises four stubs extending radially in an outer region relative to the second set of feed lines, and wherein each of the four stubs is separated from each other by an angular span of 90 degrees.
9 . The four-port omnidirectional antenna according to claim 1 , wherein the second set of feed lines is fed from a central via with a central patch to form a second feed network.
10 . The four-port omnidirectional antenna according to claim 9 , wherein the second set of feed lines comprises four shorting stubs extending radially at the centre of the first substrate, wherein the four shorting stubs are positioned orthogonally to each other while being connected to each other at the centre patch.
11 . The four-port omnidirectional antenna according to claim 1 , wherein the third set of feed lines is electrically interconnected and fed from a second power divider to form a third feed network.
12 . The four-port omnidirectional antenna according to claim 11 , wherein the second power divider is disposed in an outermost region of the second substrate.
13 . The four-port omnidirectional antenna according to claim 11 , wherein the third set of feed lines comprises a first loop consisting of four discrete angular strips in an outer region relative to the fourth set of feed lines, wherein each of the four discrete angular strips of the first loop has a first arc length defined by a first subtended angle.
14 . The four-port omnidirectional antenna according to claim 1 , wherein the fourth set of feed lines is electrically interconnected and fed by a third power divider to form a fourth feed network.
15 . The four-port omnidirectional antenna according to claim 14 , wherein the third power divider is positioned at an innermost region of the second substrate.
16 . The four-port omnidirectional antenna according to claim 14 , wherein the fourth set of feed lines comprises a second loop comprising of four discrete angular strips in an inner region relative to the third set of feed lines, wherein each of the four discrete angular strips of the second loop has a second arc length defined by a second subtended angle.
17 . The four-port omnidirectional antenna according to claim 14 , further comprising a grounded coplanar waveguide (GCPW) structure positioned around the third power divider on the second substrate to reduce cross-polarization.
18 . The four-port omnidirectional antenna according to claim 1 , wherein the first substrate and the second substrate are circular and planar, and are stacked on a common axis of rotation.
19 . The four-port omnidirectional antenna according to claim 1 , wherein the dielectric resonator is in a shape of a cylinder, and is formed of a material having a dielectric constant of 5.