Patent Publication Number: US-9905922-B2

Title: Wireless device with 3-D antenna system

Description:
BACKGROUND 
     I. Field 
     The present disclosure relates generally to electronics, and more specifically to a wireless device. 
     II. Background 
     A wireless device (e.g., a cellular phone or a smart phone) may include a transmitter and a receiver coupled to an antenna to support two-way communication. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to obtain a modulated signal, amplify the modulated signal to obtain an output RF signal having the proper power level, and transmit the output RF signal via the antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may condition and process the received RF signal to recover data sent by the base station. 
     A wireless device may include multiple transmitters and/or multiple receivers coupled to multiple antennas in order to improve performance. It may be challenging to design and build multiple antennas on the wireless device, especially at a very high frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a wireless device capable of communicating with different wireless communication systems. 
         FIG. 2  shows a wireless device with a 2-dimensional (2-D) antenna system. 
         FIG. 3  shows a wireless device with a 3-dimensional (3-D) antenna system. 
         FIGS. 4A and 4B  show two exemplary designs of a 3-D antenna system. 
         FIGS. 5A, 5B and 5C  show an exemplary design of a patch antenna. 
         FIGS. 6A, 6B and 6C  show another exemplary design of a patch antenna. 
         FIGS. 7A, 7B and 7C  show an exemplary design of an antenna array. 
         FIGS. 8A and 8B  show another exemplary design of an antenna array. 
         FIG. 9  shows yet another exemplary design of an antenna array. 
         FIG. 10  shows a 3-D antenna system formed on glass. 
         FIG. 11  shows a block diagram of a wireless device with a 3-D antenna system. 
         FIG. 12  shows a process for transmitting signals with a 3-D antenna system. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below is intended as a description of exemplary designs of the present disclosure and is not intended to represent the only designs in which the present disclosure can be practiced. The term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other designs. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary designs of the present disclosure. It will be apparent to those skilled in the art that the exemplary designs described herein may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary designs presented herein. 
     A wireless device with a 3-D antenna system is described herein. A 3-D antenna system is an antenna system that includes antenna elements formed on multiple planes pointing in different spatial directions, e.g., on two or more surfaces of a wireless device. A plane may “point” in a spatial direction that is orthogonal to the plane. The phrases “point in” and “point at” are used interchangeably herein. A wireless device with a 3-D antenna system may be any electronics device supporting wireless communication. 
       FIG. 1  shows a wireless device  110  capable of communicating with different wireless communication systems  120  and  122 . Wireless system  120  may be a Code Division Multiple Access (CDMA) system (which may implement Wideband CDMA (WCDMA), cdma2000, or some other version of CDMA), a Global System for Mobile Communications (GSM) system, a Long Term Evolution (LTE) system, etc. Wireless system  122  may be a wireless local area network (WLAN) system, which may implement IEEE 802.11, etc. For simplicity,  FIG. 1  shows wireless system  120  including one base station  130  and one system controller  140 , and wireless system  122  including one access point  132  and one router  142 . In general, each system may include any number of stations and any set of network entities. 
     Wireless device  110  may also be referred to as a user equipment (UE), a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. Wireless device  110  may be a cellular phone, a smart phone, a tablet, a wireless modem, a personal digital assistant (PDA), a handheld device, a laptop computer, a smartbook, a netbook, a cordless phone, a wireless local loop (WLL) station, a Bluetooth device, etc. Wireless device  110  may be equipped with any number of antennas. Multiple antennas may be used to provide better performance, to simultaneously support multiple services (e.g., voice and data), to provide diversity against deleterious path effects (e.g., fading, multipath, and interference), to support multiple-input multiple-output (MIMO) transmission to increase data rate, and/or to obtain other benefits. Wireless device  110  may be capable of communicating with wireless system  120  and/or  122 . Wireless device  110  may also be capable of receiving signals from broadcast stations (e.g., a broadcast station  134 ). Wireless device  110  may also be capable of receiving signals from satellites (e.g., a satellite  150 ) in one or more global navigation satellite systems (GNSS). 
     In general, wireless device  110  may support communication with any number of wireless systems, which may employ any radio technologies such as WCDMA, cdma2000, LTE, GSM, 802.11, GPS, etc. Wireless device  110  may also support operation on any number of frequency bands. 
     Wireless device  110  may support operation at a very high frequency, e.g., within millimeter (mm)-wave frequencies from 40 to 300 gigahertz (GHz). For example, wireless device  110  may operate at 60 GHz for 802.11 ad. Wireless device  110  may include an antenna system to support operation at mm-wave frequency. The antenna system may include a number of antenna elements, with each antenna element being used to transmit and/or receive signals. The terms “antenna” and “antenna element” are synonymous and are used interchangeably herein. Each antenna element may be implemented with a patch antenna, a dipole antenna, or an antenna of some other type. A suitable antenna type may be selected for use based on the operating frequency of the wireless device, the desired performance, etc. In an exemplary design, an antenna system may include a number of patch antennas supporting operation at mm-wave frequency. 
       FIG. 2  shows an exemplary design of a wireless device  210  with a 2-D antenna system  220 . In this exemplary design, antenna system  220  includes a 2×2 array  230  of four patch antennas  232  formed on a single plane corresponding to the front surface of wireless device  210 . Patch antenna array  230  has an antenna beam  250 , which points in a direction that is orthogonal to the plane on which patch antennas  232  are formed. Wireless device  210  can transmit signals directly to other devices (e.g., access points) located within antenna beam  250  and can also receive signals directly from other devices located within antenna beam  250 . Antenna beam  250  thus represents a line-of-sight (LOS) coverage of wireless device  210 . 
     An access point  290  (i.e., another device) may be located inside the LOS coverage of wireless device  210 . Wireless device  210  can transmit a signal to access point  290  via a line-of-sight (LOS) path  252 . Another access point  292  may be located outside the LOS coverage of wireless device  210 . Wireless device  210  can transmit a signal to access point  292  via a non-line-of-sight (NLOS) path  254 , which includes a direct path  256  from wireless device  210  to a wall  280  and a reflected path  258  from wall  280  to access point  292 . 
     In general, wireless device  210  can transmit a signal via a LOS path directly to another device located within antenna beam  250 , e.g., as shown in  FIG. 2 . This signal may have a much lower power loss when received via the LOS path. The low power loss may allow wireless device  210  to transmit the signal at a lower power level, which may enable wireless device  210  to conserve battery power and extend battery life. 
     Wireless device  210  can transmit a signal via a NLOS path to another device located outside of antenna beam  250 , e.g., as also shown in  FIG. 2 . This signal may have a much higher power loss when received via the NLOS path, since a large portion of the signal energy may be reflected, absorbed, and/or scattered by one or more objects in the NLOS path. Wireless device  210  can transmit the signal at a high power level in order to ensure that the signal can be reliably received via the NLOS path. However, wireless device  210  may consume excessive battery power in order to transmit the signal at the high power level. 
     An antenna element may be formed on a plane corresponding to a surface of a wireless device and may be used to transmit and/or receive signals. The antenna element may have a particular antenna beam pattern and a particular maximum antenna gain, which may be dependent on the design and implementation of the antenna element. Multiple antenna elements may be formed on the same plane and used to improve antenna gain. Higher antenna gain may be especially desirable at mm-wave frequency since (i) it is difficult to efficiently generate high power at mm-wave frequency and (ii) attenuation loss may be greater at mm-wave frequency. Each antenna element may have a limited LOS coverage area due to the directivity of the antenna element. An antenna system composed of multiple antenna elements would also have a limited LOS coverage area. The area outside of the LOS coverage area may be covered by reflected signals, but the signal strength may be weak in the NLOS coverage area. Hence, it is preferable to have a larger LOS coverage area if possible. 
     In an aspect, a wireless device may include a 3-D antenna system to improve LOS coverage and enhance performance. The 3-D antenna system may include antenna elements formed on multiple planes pointing in different spatial directions. The 3-D antenna system would then have multiple antenna beams corresponding to the multiple planes on which the antenna elements are formed. The antenna beam for each plane would cover a different LOS coverage area. The multiple antenna beams can provide a larger overall LOS coverage area for the wireless device. NLOS coverage may also improve since antenna beams pointing in different spatial directions may result in reflected signals of higher power levels due to better signal reflection for some antenna beams. 
       FIG. 3  shows an exemplary design of a wireless device  310  with a 3-D antenna system  320 . In this exemplary design, antenna system  320  includes (i) a 2×2 array  330  of four patch antennas  332  formed on a first plane corresponding to the front surface of wireless device  310  and (ii) a 2×2 array  340  of four patch antennas  342  formed on a second plane corresponding to the top surface of wireless device  310 . Antenna array  330  has an antenna beam  350 , which points in a direction that is orthogonal to the first plane on which patch antennas  332  are formed. Antenna array  340  has an antenna beam  360 , which points in a direction that is orthogonal to the second plane on which patch antennas  342  are formed. Antenna beams  350  and  360  thus represent the LOS coverage of wireless device  310 . 
     An access point  390  (i.e., another device) may be located inside the LOS coverage of antenna beam  350  but outside the LOS coverage of antenna beam  360 . Wireless device  310  can transmit a first signal to access point  390  via a LOS path  352  within antenna beam  350 . Another access point  392  may be located inside the LOS coverage of antenna beam  360  but outside the LOS coverage of antenna beam  350 . Wireless device  310  can transmit a second signal to access point  392  via a LOS path  362  within antenna beam  360 . Wireless device  310  can transmit a signal to access point  392  via a NLOS path  354  composed of a direct path  356  and a reflected path  358  due to a wall  380 . Access point  392  may receive the signal via LOS path  362  at a higher power level than the signal via NLOS path  354 . 
     As shown in  FIGS. 2 and 3 , the LOS coverage of wireless device  310  may be enhanced by using a 3-D antenna system having antenna elements formed on multiple planes. This may allow wireless device  310  to transmit signals to multiple other devices simultaneously. This may also allow wireless device  310  to transmit a signal at a lower power level in more scenarios, which may enable wireless device  310  to conserve battery power and extend battery life. 
     The NLOS coverage of wireless device  310  may also be improved by using 3-D antenna system  320 . The signals transmitted via different antenna beams may encounter different objects and may be reflected and/or scattered in different directions. This may allow signals from wireless device  310  to be received at more locations and/or at higher power levels, which may improve the coverage of wireless device  310 . 
       FIG. 3  shows an exemplary design of a 3-D antenna system comprising two 2×2 antenna arrays  330  and  340  formed on two planes. In general, a 3-D antenna system may include any number of antenna elements formed on any number of planes pointing in different spatial directions. The planes may or may not be orthogonal to one another. Any number of antennas may be formed on each plane and may be arranged in any formation. Using antennas on more planes may improve LOS coverage and possibly NLOS coverage. 
       FIG. 4A  shows an exemplary design of a wireless device  410   a  with a 3-D antenna system  420   a . In this exemplary design, antenna system  420   a  includes (i) a 4×2 array  430  of eight patch antennas  432  formed on a first plane corresponding to the front surface of wireless device  410   a  and (ii) a 4×2 array  440  of eight patch antennas  442  formed on a second plane corresponding to the top surface of wireless device  410   a . Antenna array  430  has a first antenna beam that points in a direction that is orthogonal to the first plane on which patch antennas  432  are formed. Antenna array  440  has a second antenna beam that points in a direction that is orthogonal to the second plane on which patch antennas  442  are formed. 
       FIG. 4B  shows an exemplary design of a wireless device  410   b  with a 3-D antenna system  420   b . In this exemplary design, antenna system  420   b  includes 4×2 array  430  of eight patch antennas  432  and 4×2 array  440  of eight patch antennas  442 , similar to 3-D antenna system  420   a  in  FIG. 4A . 3-D antenna system  420   b  further includes (i) a 4×2 array  450  of four patch antennas  452  formed on a third plane corresponding to the left side surface of wireless device  410   b  and (ii) a 2×2 array  460  of four patch antennas (not visible in  FIG. 4B ) formed on a fourth plane corresponding to the right side surface of wireless device  410   b . Antenna arrays  430 ,  440 ,  450  and  460  have four antenna beams that point in different spatial directions. 
       FIGS. 4A and 4B  show two exemplary designs of a 3-D antenna system. A 3-D antenna system may also be implemented in other manners. For example, a 3-D antenna system may include antenna arrays on the front and two sides (but not the top), or antenna arrays on the front and back (but not the top or sides), or antenna arrays on the front, back, and two sides (but not the top), or antenna arrays on the front, back, top, and two sides. A 3-D antenna system may also include antennas of other types (instead of patch antennas) and/or antennas arranged in other formations (instead of 2-D arrays). 
     In general, a 3-D antenna system may include antennas of any type or any combination of types. For example, a 3-D antenna system may include patch antennas, monopole antennas, dipole antennas, loop antennas, microstrip antennas, stripline antennas, printed dipole antennas, inverted F antennas, planar inverted F antennas (PIFA), polarized patches, plate antennas (which are irregularly shaped, flat antennas with no ground plane), half-wave antennas, quarter-wave antennas, etc. A patch antenna is also referred to as a planar antenna. A dipole antenna is also referred to as a whip antenna. A suitable type of antennas to use for a 3-D antenna system may be selected based on various factors such as the operating frequency of a wireless device, the desired performance, etc. Several exemplary designs of patch antennas suitable for use at 60 GHz (e.g., for 802.11ad) are described below. 
       FIG. 5A  shows an exemplary design of a patch antenna  510  suitable for mm-wave frequency. Patch antenna  510  includes a conductive patch  512  formed over a ground plane  514 . Patch  512  has a dimension (e.g., 1.55×1.55 mm) selected based on the desired operating frequency. Ground plane  514  has a dimension (e.g., 2.5×2.5 mm) selected to provide the desired directivity of patch antenna  510 . A larger ground plane also results in smaller backlobes. A feedpoint  516  is located near the center of patch  512  and is the point at which an output RF signal is applied to patch antenna  510  for transmission. The location of feedpoint  516  may be selected to provide the desired impedance match to a feedline. 
       FIG. 5B  shows a plot of an antenna beam pattern  520  for patch antenna  510  in  FIG. 5A . Antenna beam pattern  520  has a spherical shaped main lobe that points in the z-direction, which is orthogonal to the x-y plane on which patch antenna  510  is formed. The maximum antenna gain is approximately 7 decibel relative to isotropic (dBi) along the z-direction from the center of patch  512 . 
       FIG. 5C  shows a plot  530  of the frequency response of patch antenna  510  in  FIG. 5A . In  FIG. 5C , the vertical axis represents return loss in units of decibel (dB), and the horizontal axis represents frequency in units of GHz. As shown in  FIG. 5C , patch antenna  510  has a bandwidth of approximately 1.2 GHz centered at approximately 60 GHz. The bandwidth corresponds to a range of frequencies in which the return loss is lower/better than a target return loss, which may be −10 dB in  FIG. 5C . 
       FIG. 6A  shows an exemplary design of a patch antenna  610  suitable for mm-wave frequency. Patch antenna  610  includes a conductive E-shaped patch  612  formed over a ground plane  614 . Patch  612  has a dimension (e.g., 1.37×2.10 mm) selected based on the desired operating frequency. Each of slots  618   a  and  618   b  has a dimension (e.g., 1.00×0.26 mm) selected based on the desired frequency response. Ground plane  614  has a dimension (e.g., 5.0×5.0 mm) selected to provide the desired directivity. A feedpoint  616  is located near the center of patch  612  and is the point at which an output RF signal is applied to patch antenna  610 . The location of feedpoint  616  is selected to provide the desired impedance match. 
       FIG. 6B  shows a plot of an antenna beam pattern  620  for patch antenna  610  in  FIG. 6A . Antenna beam pattern  620  has a spherical shaped main lobe that points in the z-direction, which is orthogonal to the x-y plane on which patch antenna  610  is formed. The maximum antenna gain is approximately 8 dBi along the z-direction from the center of patch  612 . 
       FIG. 6C  shows a plot  630  of the frequency response of patch antenna  610  in  FIG. 6A . As shown in  FIG. 6C , patch antenna  610  has a bandwidth of approximately 10 GHz centered at approximately 60 GHz. This bandwidth is more than adequate for 802.11ad, which operates on 8.64 GHz bandwidth. E-shaped patch antenna  610  in  FIG. 6A  has a much wider bandwidth than square patch antenna  510  in  FIG. 5A . 
       FIGS. 5A and 6A  show two exemplary patch antenna designs. A patch antenna may also be implemented with other shapes such as a rectangular shape, a circular shape, an elliptical shape, an H shape, an O shape, a T shape, a V shape, a W shape, a X shape, a Y shape, a Z shape, etc. Different shapes may be associated with different bandwidths and/or different antenna beam patterns. A suitable patch shape may be selected based on the desired performance, e.g., the desired bandwidth. In general, various characteristics of an antenna such as antenna beam pattern, bandwidth, maximum antenna gain, etc. may be dependent on various factors such as the shape and dimensions of an antenna, the materials used to implement the antenna, etc. 
     Multiple patch antennas may be arranged in various formations to form an antenna array. Different array formations may be associated with different antenna beam patterns and different maximum antenna gains. 
       FIG. 7A  shows an exemplary design of a 4×1 antenna array  710  composed of four patch antennas  720   a  to  720   d  arranged in a straight line. Each patch antenna  720  may be implemented with square patch antenna  510  shown in  FIG. 5A , E-shape patch antenna  610  shown in  FIG. 6A , or a patch antenna of some other shape. Adjacent patch antennas  720  are separated by a distance of d, which may be 2.5, 3, 4, 5, 10, 20 mm, etc. Different antenna beam patterns may be obtained with different separation distances. 
       FIG. 7B  shows a plot of an antenna beam pattern  730  for patch antenna  710  in  FIG. 7A  in the y-z plane. Antenna beam pattern  730  has a main lobe that points in the z-direction, which is orthogonal to the x-y plane on which patch antennas  720  are formed. 
       FIG. 7C  shows a plot of an antenna beam pattern  740  for patch antenna  710  in  FIG. 7A  in the x-z plane. Antenna beam pattern  740  has a main lobe that points in the z-direction. The main lobe along the x-axis in  FIG. 7C  is wider than the main lobe along the y-axis in  FIG. 7B . 
       FIG. 8A  shows an exemplary design of a 2×2 antenna array  810  composed of four patch antennas  820   a  to  820   d . Each patch antenna  820  may be implemented with square patch antenna  510 , E-shape patch antenna  610 , or a patch antenna of some other shape. Patch antennas  820  are separated by a distance of d, which may be 2.5, 3, 4, 5, 10, 20 mm, etc. Different antenna beam patterns may be obtained with different separation distances. 
       FIG. 8B  shows a plot of an antenna beam pattern  830  for patch antenna  810  in  FIG. 8A  in the x-z plane. Antenna beam pattern  830  has a main lobe that points in the z-direction, which is orthogonal to the x-y plane on which patch antennas  820  are formed. An antenna beam pattern for patch antenna  810  in the y-z plane is similar to antenna beam pattern  830  in the x-z plane. 
       FIG. 9  shows an exemplary design of an antenna array  910  composed of four patch antennas  920   a  to  920   d . Each patch antenna  920  may be implemented with square patch antenna  510 , E-shape patch antenna  610 , or a patch antenna of some other shape. Patch antennas  920  are separated by a distance of d, which may be 2.5, 3, 4, 5, 10, 20 mm, etc. 
       FIGS. 7A, 8A and 9  show some exemplary antenna arrays. In general, multiple patch antennas may be arranged in any formation, which may be selected based on various factors such as the desired antenna beam pattern, the desired maximum antenna gain, the available space, etc. More patch antennas lined up in a given axis may provide a more focused and narrow antenna beam but a higher antenna gain. Multiple patch antennas lined up in a given axis may also be used for beamforming, as described below. 
       FIG. 10  shows a side view of an exemplary design of a 3-D antenna system  1010  formed on glass. 3-D antenna system  1010  includes (i) an array  1020  of patch antennas (Ant)  1022   a  and  1022   b  formed on a first plane (e.g., corresponding to the front surface of a wireless device) and (ii) an array  1030  of patch antennas  1032   a  and  1032   b  formed on a second plane (e.g., corresponding to the top surface of the wireless device). 
     Antennas  1022  and  1032  are formed over an outer surface  1042  of an L-shaped glass substrate  1040 . An RF chip  1050  includes (i) transmit circuits to generate output RF signals for transmission via antennas  1022  and  1032  and/or (ii) receive circuits to process received RF signals from antennas  1022  and  1032 . RF chip  1050  is electrically coupled to antennas  1022  through vias  1024 , which are formed through glass substrate  1040 . RF chip  1050  is also electrically coupled to antennas  1032  through a conductive interconnect  1036  and vias  1034 , which are formed through glass substrate  1040 . 
     Table 1 lists different ways of forming antennas in a 3-D antenna system. As shown in Table 1, antenna elements may be formed on an integrated circuit (IC) chip, on an IC package, on a circuit board, or on a glass substrate (e.g., as shown in  FIG. 10 ). On-chip implementation may provide easy integration but may have high cost because of the high per unit area cost of an IC chip. On-package implementation may be compact but may require a customized IC package. On-board implementation may provide good performance (depending on the material used for a circuit board) and may provide flexibility. On-glass implementation may have certain advantages such as lower cost, simple integration with microelectromechanical systems (MEMS) technology, and ease of 3-D manufacturing. Antenna elements may be formed on glass based on MEMS or some other process technology. Antennas in a 3-D antenna system may be fabricated based on any one or any combination of the ways listed in Table 1 and/or in other ways. In Table 1, a smaller loss tangent is better and may reduce loss. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Implementations of Antennas in a 3-D Antenna System 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Loss 
                   
               
               
                 Antenna 
                 Material 
                 Tangent 
                 Description 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 On Chip 
                 CMOS wafer 
                   
                 Easy integration but high cost. 
               
               
                 On 
                 Wafer level 
                   
                 Compact implementation; ground 
               
               
                 Package 
                 package 
                   
                 plane inside package is not clear; 
               
               
                   
                   
                   
                 may need a special package design. 
               
               
                 On Board 
                 FR4 
                 0.02 
                 Low cost but lossy. 
               
               
                 On Board 
                 Rogers RT/ 
                 0.0009 
                 Good performance; variety of antenna 
               
               
                   
                 Duroid 5880 
                   
                 options available. 
               
               
                 On Glass 
                 Glass 
                 0.004 
                 Can implement antennas with MEMS 
               
               
                   
                   
                   
                 technology. 
               
               
                   
               
            
           
         
       
     
     In general, a wireless device may include antenna elements (e.g., patch antennas) formed on any number of planes in a volume, a sphere, or some other shape. Furthermore, any number of antenna elements may be formed on a given plane. The number of planes to use, the number of antenna elements on each plane, and the design of each antenna element may be flexibly selected based on the requirements of the wireless device. 
     In an exemplary design, beamforming may be used for a 3-D antenna system to improve LOS coverage and/or obtain other advantages. Beamforming may be performed for one or more antenna arrays in the 3-D antenna system. Beamforming may be used to steer an antenna beam of an antenna array in different spatial directions, which would then expand the LOS coverage of the antenna array. Beamforming may be performed for an array of antennas by applying complex gains to multiple signals transmitted via different antennas in the array. 
       FIG. 11  shows a block diagram of an exemplary design of a wireless device  1110  with a 3-D antenna system  1120 . In this exemplary design, 3-D antenna system  1120  includes K antenna arrays  1130   a  to  1130   k  formed on K planes pointing in different spatial directions, where K may be any integer value greater than one. Each antenna array  1130  includes N antennas  1132 , where N may be any integer value greater than one. The K antenna arrays  1130   a  to  1130   k  may include the same or different numbers of antennas. 
     For data transmission, a data processor  1150  may process (e.g., encode and modulate) data to be transmitted and provide K data signals Xout 1  to XoutK for the K antenna arrays  1130   a  to  1130   k . In one exemplary design, the K data signals may be identical, and the same information may be sent from all K antenna arrays  1130   a  to  1130   k . In another exemplary design, the K data signals may be different data signals, and different information may be sent from the K antenna arrays  1130   a  to  1130   k.    
     Within a transmit section  1152   a  for antenna array  1130   a , the Xout 1  data signal may be provided to N multipliers  1160   a  to  1160   n , which may also receive N complex gains G T11  to G T1N , respectively. Each multiplier  1160  may multiply the Xout 1  data signal with its complex gain and provide a scaled data signal. The scaled data signal from each multiplier  1160  may be processed by associated transmit (TX) circuits  1162  and further amplified by an associated power amplifier (PA)  1164  to generate an output RF signal. The output RF signal may be routed through a switchplexer/duplexer (Sw/Duplexer)  1166  and transmitted via an associated antenna  1132 . TX circuits  1162  may include digital-to-analog converters (DACs), amplifiers, filters, upconverters/mixers, etc. N scaled data signals from N multipliers  1160   a  to  1160   n  may thus be processed and transmitted via N antennas  1132   aa  to  1132   an  of antenna array  1130   a . Multipliers  1160   a  to  1160   n  may also be placed at other locations within the N transmit paths (e.g., after TX circuits  1162 ) in transmit section  1152   a . Multipliers  1160   a  to  1160   n  may be implemented in hardware, software, firmware, etc. 
     Each remaining transmit section  1152  may similarly receive and process its data signal with a set of complex gains for its associated antenna array  1130  to generate a set of scaled data signals. The scaled data signals may be further processed and transmitted via N antennas  1132  in the associated antenna array  1130 . 
     For data reception, antenna arrays  1130   a  to  1130   k  may receive RF signals transmitted by other devices. The received RF signals from antennas  1132  may be routed through switchplexers/duplexers  1166 , amplified by low noise amplifiers (LNAs)  1170 , and further processed by receive (RX) circuits  1172  to obtain received baseband signals. RX circuits  1172  may include downconverters/mixers, amplifiers, filters, analog-to-digital converters (ADCs), etc. 
     Within a receive section  1154   a  for antenna array  1130   a , N multipliers  1174   a  to  1174   n  are provided with N received baseband signals from N RX circuits  1172  and also N complex gains G R11  to G R1N , respectively. Each multiplier  1174  may multiply its received baseband signal with its complex gain and provide a scaled received baseband signal. N received RF signals from N antennas  1132   aa  to  1132   an  of antenna array  1130   a  may thus be processed and scaled by N multipliers  1174   a  to  1174   n . A summer  1176  may sum the N scaled received baseband signals from multipliers  1174   a  to  1174   n  and provide an input signal Xin 1  to data processor  1150 . Multipliers  1174   a  to  1174   n  and summer  1176  may also be placed at other locations within the N receive paths (e.g., before RX circuits  1172 ) in receive section  1154   a . Multipliers  1174   a  to  1174   n  for each antenna array  1130  may be implemented in hardware, software, firmware, etc. Each remaining receive section  1154  may similarly receive and process its received RF signals with a set of complex gains for its associated antenna array  1130  to generate an input signal. Data processor  1150  may process (e.g., demodulate and decode) the K input signals Xin 1  to XinK from K summers  1176  for the K antenna arrays  1130   a  to  1130   k.    
     A controller/processor  1190  may direct the operation of various units within wireless device  1110 . A memory  1192  may store program codes and data for wireless device  1110 . Data processor  1150 , controller/processor  1190 , and memory  1192  may communicate via a bus  1194  and/or other means. 
     All or a portion of transmit sections  1152   a  to  1152   k  and receive sections  1154   a  to  1154   k  may be implemented on one or more analog ICs, RF ICs (RFICs), mixed-signal ICs, etc. The remaining portion of transmit sections  1152   a  to  1152   k  and receive sections  1154   a  to  1154   k , data processor  1150 , controller/processor  1190 , and memory  1192  may be implemented on one or more application specific integrated circuits (ASICs) and/or other ICs. 
     Wireless device  1110  may perform beamforming in various manners for 3-D antenna system  1120 . Wireless device  1110  may perform beamforming for only one antenna array  1130   a  (e.g., an antenna array on the front surface of wireless device  1110 ), or all K antenna arrays  1130   a  to  1130   k , or a subset of the K antenna arrays. In one exemplary design, wireless device  1110  may perform beamforming independently for each antenna array  1130  for which beamforming is supported. For each antenna array  1130 , wireless device  1110  may evaluate different antenna beams and may select the antenna beam with the best performance. This may be achieved in various manners. 
     In one exemplary design, wireless device  1110  may identify the best antenna beam for each antenna array  1130  based on signals received by wireless device  1110 . Wireless device  1110  may select one antenna beam at a time for evaluation for a given antenna array. For each antenna beam, wireless device  1110  may detect for signals (e.g., pilot signals and/or data signals) from other devices and may measure the received power of each detected signal. Wireless device  1110  may identify the antenna beam with the highest received power for a device of interest as the best antenna beam for the antenna array. Wireless device  1110  may identify the best antenna beam for each remaining antenna array in similar manner. 
     In another exemplary design, wireless device  1110  may identify the best antenna beam for each antenna array  1130  based on signals transmitted by wireless device  1110 . Wireless device  1110  may select one antenna beam at a time for evaluation for a given antenna array. For each antenna beam, wireless device  1110  may transmit signals (e.g., pilot signals and/or data signals) to other devices. Wireless device  1110  may receive feedback determined by other devices based on the signals transmitted by wireless device  1110 . For example, wireless device  1110  may receive feedback indicating the received power of the pilot and/or data signals transmitted by wireless device  1110  as measured at the other devices. As another example, wireless device  1110  may receive feedback indicating whether data signals transmitted by wireless device  1110  have been decoded correctly by the other devices. In any case, wireless device  1110  may identify the antenna beam with the best performance (e.g., the highest received power or the lowest error rate) as the best antenna beam for the antenna array. Wireless device  1110  may identify the best antenna beam for each remaining antenna array in similar manner. In yet another exemplary design, wireless device  1110  may identify the best antenna beam for each antenna array  1130  based on a combination of received signals and transmitted signals. 
     In general, wireless device  1110  may determine a performance metric for each antenna beam based on one or more criteria. For example, a performance metric may relate to the received power of signals received by wireless device  1110 , the received power of signals transmitted by wireless device  1110  as measured at other devices, an error rate of transmitted signals or received signals, etc. Wireless device  1110  may identify the best antenna beam for each antenna array based on the performance metric for each antenna beam for that antenna array. 
     A set of complex gains or coefficients may be used for each antenna array  1130  to perform beamforming for that antenna array, as shown in  FIG. 11 . A complex gain may be defined by either (i) a real value A and an imaginary value B (i.e., A+jB) or (ii) an amplitude K and a phase θ (i.e., K ∠θ). In one exemplary design, the complex gains for each antenna array  1130  can have different amplitudes and/or phases, which may be selected to obtain the desired antenna beam. This exemplary design may provide more flexibility to define an antenna beam for an antenna array. In another exemplary design, the complex gains for each antenna array  1130  have the same amplitude (e.g., 1.0) but can have different phases, which may be selected to obtain the desired antenna beam. This exemplary design may allow the full transmit power to be utilized for each antenna  1132 . In an exemplary design, one complex gain in a set of complex gains for an antenna array may have a fixed value (e.g., 1.0). This may allow one multiplier (e.g., multiplier  1160   a  in transmit section  1152   a  in  FIG. 11 ) to be omitted. 
     A plurality of sets of complex gains associated with different antenna beams may be available for an antenna array. In one exemplary design, the plurality of sets of complex gains may be (i) determined a priori based on computer simulations, empirical measurements, and/or via other means and (ii) stored in a non-volatile memory (e.g., memory  1192 ) on wireless device  1110 . For example, M sets of complex gains for M antenna beams pointing in different spatial directions (e.g., evenly spaced apart in the spatial domain) may be determined and stored, where M may be any integer value. One set of complex gains may be applied at any given moment to obtain an antenna beam associated with that set of complex gains. 
     In another exemplary design, a plurality of sets of complex gains for an antenna array may be adaptively determined. For example, an initial set of complex gains may be used for the antenna array, and a performance metric may be determined for this initial set. One or more complex gains in the initial set may be varied within a predetermined range to obtain a new set of complex gains. The complex gain(s) may be varied randomly or based on a search algorithm. A performance metric may be determined for the new set of complex gains. The new set of complex gains may be retained if the performance metric for the new set is better than the performance metric for the initial set. One or more complex gains may be iteratively varied and evaluated in similar manner until the best performance metric is obtained. 
     In an exemplary design, an apparatus may comprise first and second sets of antenna elements, e.g., as shown in  FIGS. 3 and 11 . The apparatus may be a wireless device, an antenna module, an IC chip, an IC package, a circuit board, etc. The first set of antenna elements (e.g., antenna elements  332  in  FIG. 3 , or antenna elements  1132   aa  to  1132   an  in  FIG. 11 ) may be formed on a first plane of a wireless device and may be associated with a first antenna beam obtained with beamforming, e.g., via a first set of complex gains for the first set of antenna elements. The second set of antenna elements (e.g., antenna elements  342  in  FIG. 3 , or antenna elements  1132   ka  to  1132   kn  in  FIG. 11 ) may be formed on a second plane of the wireless device. The first and second planes may point in different spatial directions. For example, the first plane may be orthogonal to the second plane of the wireless device. 
     In an exemplary design, the first plane may correspond to a front surface of the wireless device, and the second plane may correspond to a top surface of the wireless device, e.g., as shown in  FIG. 3 . The first and second planes may also correspond to other surfaces of the wireless device. 
     In an exemplary design, the second set of antenna elements may be associated with a second antenna beam obtained with beamforming, e.g., via a second set of complex gains for the second set of antenna elements. In general, beamforming may be performed for only the first set of antenna elements or both the first and second sets of antenna elements. Beamforming may also be performed independently for the first and second sets of antenna elements, e.g., using different sets of complex gains for the two sets of antenna elements. Alternatively, beamforming may be performed jointly for the two sets of antenna elements, e.g., using the same set of complex gains for both sets of antenna elements. 
     In an exemplary design, the first set of antenna elements may radiate an output signal via the first antenna beam, and the second set of antenna elements may also radiate the output signal via the second antenna beam. In this exemplary design, the same output signal may be transmitted from both sets of antenna elements. In another exemplary design, different output signals may be transmitted from the first and second sets of antenna elements. 
     In an exemplary design, the same antenna beam may be used for both transmission and reception. In this exemplary design, the first set of antenna elements may receive a signal from another device via the first antenna beam. In another exemplary design, different antenna beams may be used for transmission and reception. In this exemplary design, the first set of antenna elements may receive a signal from another device via another antenna beam obtained with beamforming, e.g., via another set of complex gains for the first set of antenna elements, e.g., as shown in  FIG. 11 . 
     The apparatus may further comprise first and second sets of power amplifiers, e.g., as shown in  FIG. 11 . The first set of power amplifiers (e.g., power amplifiers  1164  in transmit section  1152   a  in  FIG. 11 ) may receive a first set of input signals generated based on the output signal and may provide a first set of output RF signals for transmission via the first set of antenna elements. The second set of power amplifiers (e.g., power amplifiers  1164  in transmit section  1152   k  in  FIG. 11 ) may receive a second set of input signals generated based on the same output signal or another output signal and may provide a second set of output RF signals for transmission via the second set of antenna elements. 
     The apparatus may further comprise first and second sets of LNAs, e.g., as shown in  FIG. 11 . The first set of LNAs (e.g., LNAs  1170  in receive section  1154   a  in  FIG. 11 ) may receive a first set of received RF signals from the first set of antenna elements and may provide a first set of amplified signals. The second set of LNAs (e.g., LNAs  1170  in receive section  1154   k  in  FIG. 11 ) may receive a second set of received RF signals from the second set of antenna elements and may provide a second set of amplified signals. 
     In an exemplary design, the first set of antenna elements may form a first antenna array, and the second set of antenna elements may form a second antenna array. In an exemplary design, the first set of antenna elements may comprise a plurality of patch antennas, which may be arranged in a 2-D array. In an exemplary design, each patch antenna may have a square shape, as shown in  FIG. 5A . In another exemplary design, each patch antenna may have a non-square shape, i.e., any shape that is not a square or a rectangle. For example, each patch antenna may have an E shape, as shown in  FIG. 6A . 
     In an exemplary design, the first set of antenna elements may be formed on a first surface of a glass substrate, and the second set of antenna elements may be formed on a second surface of the glass substrate, e.g., as shown in  FIG. 10 . The second surface may be orthogonal to the first surface. In other exemplary designs, the first and second sets of antenna elements may be formed on an IC chip, an IC package, a circuit board, etc., as listed in Table 1. 
     In an exemplary design, the apparatus may further comprise a memory that stores a plurality of sets of complex gains associated with different antenna beams for the first set of antenna elements. The first set of complex gains for the first set of antenna elements may be one of the plurality of sets of complex gains. In an exemplary design, the complex gains in the first set may have equal amplitude and variable phases (i.e., possibly different phases). In another exemplary design, the complex gains in the first set may have variable amplitudes and variable phases (i.e., possibly different amplitudes and phases). 
     In an exemplary design, the first and second sets of antenna elements may operate at a millimeter wave frequency between 40 and 300 GHz. The first and second sets of antenna elements may also operate at other frequency ranges. 
     The apparatus may also include one or more additional sets of antenna elements formed on one or more additional planes of the wireless device. Each set of antenna elements may be associated with a respective antenna beam pointing in a different spatial direction. The first, second, and possibly additional sets of antenna elements may provide better LOS coverage and possibly better NLOS coverage for the wireless device. 
       FIG. 12  shows an exemplary design of a process  1200  for transmitting signals with a 3-D antenna system. A first signal may be transmitted with beamforming from a first set of antenna elements formed on a first plane of a wireless device (block  1212 ). The first signal may be transmitted with beamforming via a first set of complex gains for the first set of antenna elements. A second signal may be transmitted from a second set of antenna elements formed on a second plane of the wireless device (block  1214 ). The second signal may also be transmitted with beamforming, e.g., via a second set of complex gains for the second set of antenna elements. The first and second planes may point in different spatial directions. 
     In an exemplary design, the first and second signals may comprise the same output signal. This exemplary design may improve LOS coverage of the wireless device. In another exemplary design, the first and second signals may comprise different output signals. This exemplary design may enable the wireless device to transmit to multiple other devices simultaneously, e.g., as shown in  FIG. 3 . 
     In an exemplary design, a performance metric may be determined for the first set of antenna elements for each of a plurality of sets of complex gains corresponding to different antenna beams (block  1216 ). A set of complex gains may be selected from among the plurality of sets of complex gains based on the performance metric for each of the plurality of sets of complex gains (block  1218 ). The selected set of complex gains may be used for beamforming for the first set of antenna elements. Blocks  1216  and  1218  may be performed after blocks  1212  and  1214  (as shown in  FIG. 12 ) or before blocks  1212  and  1214  (not shown in  FIG. 12 ). 
     In an exemplary design, a third signal may be received via the first set of antenna elements. The third signal may be received with beamforming, e.g., via the first set of complex gains or a third set of complex gains for the first set of antenna elements. A fourth signal may be received via the second set of antenna elements. The fourth signal may be received with beamforming, e.g., via the second set of complex gains or a fourth set of complex gains for the first set of antenna elements. For each set of antenna elements, the same antenna beam may be used for both transmission and reception, or different antenna beams may be used for transmission and reception. 
     Certain parts of a wireless device with a 3-D antenna system described herein may be implemented on an IC, an analog IC, an RFIC, a mixed-signal IC, an ASIC, a printed circuit board (PCB), an electronic device, etc. Circuitry supporting transmission and/or reception of signals via the 3-D antenna system may be fabricated with various IC process technologies such as complementary metal oxide semiconductor (CMOS), N-channel MOS (NMOS), P-channel MOS (PMOS), bipolar junction transistor (BJT), bipolar-CMOS (BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), heterojunction bipolar transistors (HBTs), high electron mobility transistors (HEMTs), silicon-on-insulator (SOI), etc. 
     An apparatus with a 3-D antenna system described herein may be a stand-alone device or may be part of a larger device. A device may be (i) a stand-alone IC, (ii) a set of one or more ICs that may include memory ICs for storing data and/or instructions, (iii) an RFIC such as an RF receiver (RFR) or an RF transmitter/receiver (RTR), (iv) an ASIC such as a mobile station modem (MSM), (v) a module that may be embedded within other devices, (vi) a receiver, cellular phone, wireless device, handset, or mobile unit, (vii) etc. 
     In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
     The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.