Two-port antenna structure for multiple-input multiple-output communications

A two-port antenna structure with four arms is provided on a printed circuit board.

TECHNICAL FIELD

Some embodiments of the present invention pertain to antennas. Some embodiments pertain to multiple-input multiple-output (MIMO) communication systems, and some embodiments pertain to multicarrier and orthogonal frequency division multiplexed (OFDM) communications.

BACKGROUND

Conventional dual-polarized antennas have been difficult to implement on printed circuit boards because of the complexity of their feed structure. Some conventional feed structures employ dual coaxial cables for each pair of radiating elements requiring four coaxial cables.

DETAILED DESCRIPTION

The following description and the drawings illustrate specific embodiments of the invention sufficiently to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. Embodiments of the invention set forth in the claims encompass all available equivalents of those claims. Embodiments of the invention may be referred to, individually or collectively, herein by the term “invention” merely for convenience and without intending to limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed.

FIG. 1Aillustrates a top view of an antenna structure in accordance with some embodiments of the present invention.FIG. 1Billustrates a side view of the antenna structure ofFIG. 1A, andFIG. 1Cillustrates a perspective view a center region of the antenna structure ofFIG. 1A. Antenna structure100employs a smart feed that may be less complex than many conventional feed structures and may eliminate some coaxial inputs/outputs associated with conventional dual-polarized antennas. In accordance with some embodiments of the present invention, antenna structure100may be a two-port antenna structure comprising four arms or radiating elements. As illustrated, first and second radiating elements101and102are disposed on first side105of insulating material111, and third and fourth radiating elements103and104are disposed on second side106of insulating material11.

Referring toFIG. 1C, first port crossover line107is disposed on first side105and coupled with second radiating element102extending across center region112of antenna structure100. First port crossover line107may couple a first communication signal to second radiating element102. In these embodiments, second port crossover line108is disposed on second side106and coupled with fourth radiating element104extending across center region112of antenna structure100. Second port crossover line108may couple a second communication signal to fourth radiating element104.

In some embodiments, first conductor113of first signal input109may extend through insulating material111to couple with first port crossover line107. Second conductor115of first signal input109may couple with third radiating element103. First conductor114of second signal input110may extend through insulating material111to couple with first radiating element101. Second conductor116of second signal input110may couple with second port crossover line108.

In some multiple-input multiple-output (MIMO) embodiments, first signal input109may couple the first communication signal and second signal input110may couple the second communication signal. In these MIMO embodiments, signal inputs109and110may carry separate and distinct communication signals for either simultaneous transmission by a MIMO transmitter or simultaneous reception by a MIMO receiver.

In some non-MIMO dual-polarized embodiments, the signals communicated by second and third radiating elements102and103may have a first polarization, and the signals communicated by first and fourth radiating elements101and104may have a second polarization. In these non-MIMO embodiments, the signal components communicated by adjacent radiating elements of structure100may be ninety-degrees out-of-phase with each other allowing for the transmission and/or reception of a circularly polarized signal, although the scope of the invention is not limited in this respect.

In some embodiments, first signal input109may comprise a first coaxial cable input, first conductor113of first signal input109may be a center conductor and second conductor115of first signal input109may be an outer ground path conductor. Second signal input110may comprise a second coaxial cable input, first conductor114of second signal input110may be a center conductor and second conductor116of second signal input110may be an outer ground path conductor.

In some embodiments, first and second signal inputs109and110may use RF connectors119and120for coupling with other system components. In some embodiments, antenna structure100may include coaxial cables having coaxial connectors at the opposite ends for connecting to other system components, although the scope of the invention is not illustrated in this respect.

In some embodiments, insulating material111may comprise a printed circuit board. In some embodiments, insulating material111may be an insulating substrate, although the scope of the invention is not limited in this respect.

In some embodiments, second and third radiating elements102and103may be diagonally or oppositely positioned with respect to each other for communicating (i.e., transmitting and/or receiving) a first communication signal. In these embodiments, first and fourth radiating elements101and104may also be diagonally or oppositely positioned with respect to each other for communicating (i.e., transmitting and/or receiving) a second communication signal. In some embodiments, the four radiating elements may be disposed on insulating material111in quadrature positions about center region112as illustrated inFIG. 1.

In some embodiments, the radiating elements may have either a spacing or an overlap therebetween that may be selected based on the desired performance characteristics of the antenna structure.FIG. 1Aillustrates small spacing117between the antenna's radiating elements, whileFIG. 1Billustrates overlap118between the radiating elements on opposite sides of the insulating material111.

Although radiating elements101,102,103, and104are illustrated as having a particular shape (e.g., somewhat like a pinwheel), the scope of the invention is not limited in this respect. Radiating elements with other shapes may also be suitable.

In some embodiments, first port crossover line107may extend diagonally on first side105across center region112of antenna structure100, and second port crossover line108may extend diagonally on second side106across center region112of antenna structure100. In some embodiments, first and second port crossover lines107and108may be substantially perpendicular to each other on opposite sides of insulating material111. In some embodiments, first and second port crossover lines107and108may comprise microstrip lines, although the scope of the invention is not limited in this respect.

In some embodiments, antenna structure100may comprise a two-signal input antenna structure for use in a multiple-input multiple-output multicarrier communication system, such as an orthogonal frequency division multiplexed (OFDM) communication system, although the scope of the invention is not limited in this respect. In these embodiments, second and third radiating elements102and103may communicate a first multicarrier communication signal and first and fourth radiating elements101and104may communicate a second multicarrier communication signal. In some embodiments, the first and second communication signals may be transmitted concurrently and may comprise a single orthogonal frequency division multiplexed symbol, although the scope of the invention is not limited in this respect. Examples of these embodiments are described in more detail below.

In some embodiments, radiating elements101,102,103and104, and first and second port crossover lines107and108may comprise almost any conductive material that may be disposed or printed on insulating material111. In some embodiments, the conductive material may comprise copper, gold or silver, although the scope of the invention is not limited in this respect. In some embodiments, insulating material111may comprise almost any insulating substrate including many convention printed circuit board materials.

FIG. 2illustrates S-parameter performance of an example antenna structure in accordance with some embodiments of the present invention. S-parameter magnitude202shows an example of computed return loss (i.e., S11) for a first signal input, such as first signal input109(FIG. 1A) of antenna structure100(FIG. 1A), and S-parameter magnitude204shows an example of computed return loss (i.e., S22) for a second signal input, such as second signal input110(FIG. 1A) of antenna structure100(FIG. 1A). S-parameter magnitude206shows an example of either transmission or reception loss (i.e., S21) for either the first or the second signal input of an antenna structure, such as antenna structure100(FIG. 1A).

Although the S-parameters illustrated inFIG. 2illustrate the operation of antenna structure100(FIG. 1A) over a particular frequency range, the scope of the invention is not limited in this respect. The size and spacing of the elements of antenna100(FIG. 1A) may be changed and tuned to operate over other frequency ranges.

FIG. 3illustrates a block diagram of a multiple-input multiple-output (MIMO) communication station in accordance with embodiments of the present invention. MIMO communication station300includes transceiver312, antenna structure302for receiving communication signals and antenna structure310for transmitting communication signals. Antenna structure100(FIG. 1A) may be suitable for use as antenna structure302and/or antenna structure310, although the scope of the invention is not limited in this respect.

In some embodiments, transceiver312may comprise radio-frequency (RF) transmitter (TX) circuitry308A and309B to generate first and second first and second communication signals309A and309B respectively from first and second baseband signals311A and311B. In these embodiments, transceiver312may also comprise baseband processing circuitry306to generate first and second transmit baseband signals311A and311B from one or more data streams307for concurrent transmission.

In some embodiments, transceiver312may comprise RF receiver (RX) circuitry304A and304B to receive communication signals from antenna structure302and generate first and second received baseband signals305A and305B respectively from the received first and second multicarrier communication signals303A and303B. In some of these embodiments, baseband processing circuitry306may weight and combine components of first and second received baseband signals305A and305B (e.g., in the frequency-domain) to generate one or more output data streams307, although the scope of the invention is not limited in this respect.

In some embodiments, multicarrier transceiver312may be part of a wireless communication device that may transmit multicarrier signals, such as orthogonal frequency division multiplexed (OFDM) communication signals. In some embodiments, multicarrier transceiver312may communicate over a multicarrier communication channel. The multicarrier communication channel may be within a predetermined frequency spectrum and may comprise a plurality of orthogonal subcarriers. In some embodiments, the orthogonal subcarriers may be closely spaced OFDM subcarriers. To help achieve orthogonality between the closely spaced subcarriers, each subcarrier may have a null at substantially a center frequency of the other subcarriers. In some embodiments, to help achieve orthogonality between the closely spaced subcarriers, each subcarrier may have an integer number of cycles within a symbol period, although the scope of the invention is not limited in this respect.

In some embodiments, the frequency spectrums for a multicarrier communication signal may comprise either a 5 GHz frequency spectrum or a 2.4 GHz frequency spectrum. In these embodiments, the 5 GHz frequency spectrum may include frequencies ranging from approximately 4.9 to 5.9 GHz, and the 2.4 GHz spectrum may include frequencies ranging from approximately 2.3 to 2.5 GHz, although the scope of the invention is not limited in this respect as other frequency spectrums are also equally suitable. In some broadband and WiMax embodiments, the frequency spectrum for communications may comprise frequencies between 2 and 11 GHz, although the scope of the invention is not limited in this respect.

In some embodiments, multicarrier transceiver312may communicate in accordance with specific communication standards, such as the Institute of Electrical and Electronics Engineers (IEEE) standards including IEEE 802.11(a), 802.11(b), 802.11(g), 802.11 (h) and/or 802.11 (n) standards for wireless local area networks (WLANs), although multicarrier transceiver312may also be suitable to transmit and/or receive communications in accordance with other techniques including the Digital Video Broadcasting Terrestrial (DVB-T) broadcasting standard, and the High performance radio Local Area Network (HiperLAN) standard. In some broadband and WiMax embodiments, multicarrier transceiver312may communicate broadband wireless communications in accordance with the IEEE 802.16(e) standards for wireless metropolitan area networks (WMANs).

In some embodiments, multicarrier transceiver312may be part of a wireless communication device, such as personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, television or other device that may receive and/or transmit information wirelessly. In some broadband and WiMax embodiments, multicarrier transceiver312may be part of a multicarrier communication station.