CSRR-loaded MIMO antenna systems
The CSRR-loaded MIMO antenna systems provide highly compact designs for multiple-input-multiple-output (MIMO) antennas for use in wireless mobile devices. Exemplary two element (2×1), and four element (2×2) MIMO antenna systems are disclosed in which complementary split-ring resonators load patch antennas elements. The overall dimensions of the exemplary MIMO antenna system designed for operation from 750 MHz to 6 GHz band remain within 100×50×0.8 mm 2 .
1. A CSRR(complementary split-ring resonators)-loaded MIMO antenna system, comprising a printed circuit board (PCB) having:
at least one pair of patch antenna elements on an upper substrate surface of the PCB, the patch antenna elements being co-aligned lengthwise in mirror-image fashion, each of the patch antenna elements being a substantially rectangular planar conductor having a substantially rectangular planar microstrip transmission line extending parallel to but offset from a centerline of the rectangular planar conductor towards an edge of the PCB;
a ground plane disposed on a lower substrate surface of the PCB; and
a plurality of complementary split-ring resonators (CSRRs) defined in the ground plane, each of the patch antenna elements having a corresponding one of the CSSRs centered directly beneath the patch antenna element, each of the resonators being concentric inner and outer split rings.
2. The CSRR-loaded MIMO antenna system according to claim 1 , wherein in each said resonator, the outer ring has the split defined therein 180° opposite the split defined in the inner ring.
3. The CSRR-loaded MIMO antenna system according to claim 1 , wherein the split in the outer ring of each said resonator extends parallel to the microstrip transmission line of the corresponding patch antenna element directly above said resonator.
4. The CSRR-loaded MIMO antenna system according to claim 1 , wherein:
in each said resonator, the outer ring has the split defined therein 180° opposite the split defined in the inner ring; and
the split in the outer ring of each said resonator extends parallel to the microstrip transmission line of the corresponding patch antenna element directly above said resonator.
5. The CSRR-loaded MIMO antenna system according to claim 1 , wherein said at least one pair of patch antenna elements consists of a single pair of patch antenna elements, the transmission lines of the patch antenna elements extending to the same edge of the PCB.
6. The CSRR-loaded MIMO antenna system according to claim 1 , wherein said microstrip transmission lines are matched to an impedance of 50Ω.
7. The CSRR-loaded MIMO antenna system according to claim 1 , wherein said PCB substrate is an FR-4 material having relative permittivity of about 4.4 and thickness of about 0.8 mm.
8. The CSRR-loaded MIMO antenna system according to claim 7 , wherein said at least one pair of patch antenna elements consists of a two pairs of patch antenna elements, the transmission lines of one of the pairs of the patch antenna elements extending to a first edge of the PCB, the transmission lines of the other pair of the patch antenna elements extending to a second edge of the PCB 180° opposite the first edge, the two pairs of the patch antenna elements being disposed as symmetrical mirror images of each other on the PCB.
9. The CSRR-loaded MIMO antenna system according to claim 8 , wherein:
each said patch antenna element has dimensions of about 14×18 mm 2 ;
said patch antenna elements in each of the pairs has a centerline displacement of the microstrip transmission lines of about 4 mm;
spacing between each said patch antenna elements in each of the pairs is about 10 mm;
radii of the outer rings of said resonators is about 6 mm;
each of the rings in said resonators has a strip width of about 0.5 mm;
spacing between the inner and outer rings of each said resonator is about 0.5 mm; and
the splits in each said ring have a width of about 0.5 mm;
whereby the CSRR-loaded MIMO antenna system is tuned for operation at about 2.45 GHz in the ISM band.
10. The CSRR-loaded MIMO antenna system according to claim 8 , wherein each of said patch antenna elements has dimensions of about 14×11 mm 2 , spacing between said patch antenna elements in each of the pairs is about 5 mm, and radii of the outer rings of each said resonator is about 2.5 mm, whereby the CSRR-loaded MIMO antenna system is tuned for operation at about 5 GHz.
11. The CSRR-loaded MIMO antenna system according to claim 1 , wherein said at least one pair of patch antenna elements consists of a two pairs of patch antenna elements, the transmission lines of one of the pairs of the patch antenna elements extending to a first edge of the PCB, the transmission lines of the other pair of the patch antenna elements extending to a second edge of the PCB 180° opposite the first edge, the two pairs of the patch antenna elements being disposed as symmetrical mirror images of each other on the PCB.