Patent Publication Number: US-11050138-B2

Title: Combo sub 6GHz and mmWave antenna system

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to an antenna system and, in particular embodiments, to an antenna system that is a combination of a sub six gigahertz antenna and a millimeter wave antenna. 
     BACKGROUND 
     A user equipment (UE) or any other device used by an end user to communicate will be referred to herein as a UE. A UE might contain multiple antennas operating in multiple different frequency bands. For example, a UE might include an antenna for a second generation (2G) band, an antenna for a third generation (3G) band, an antenna for a fourth generation (4G) Long Term Evolution (LTE) band, an antenna for a Global Positioning System (GPS) unit, and/or an antenna for a Wi-Fi system. In addition, fifth generation (5G) UEs might include one or more sub 6 gigahertz (GHz) antennas and/or one or more millimeter wave (mmWave) antennas. 
     The term “sub 6 GHz” is typically used by those of skill in the art to refer to signals that have traditionally been used in cellular communications, and the term will be used in that manner herein. The frequency range for such signals might be between approximately 30 megahertz (MHz) and approximately 6 GHz, but the frequency range is not necessarily limited to those lower and upper values. 
     The term “mmWave” is typically used by those of skill in the art to refer to signals with a frequency in a range of approximately 24 GHz to 300 GHz, and the term will be used in that manner herein. However, the frequency range is not necessarily limited to those lower and upper values. 
     SUMMARY 
     In accordance with an embodiment of the present disclosure, an antenna system comprises a first antenna portion configured to transmit a first signal received from a first feed and a second antenna portion configured to transmit a second signal received from a second feed. The second antenna portion is capacitively coupled to the second feed and inductively coupled to the first antenna portion, and the second signal has a frequency greater than a frequency of the first signal. 
     In the previous embodiment, the second antenna portion might be capacitively coupled to the second feed via a capacitive coupling structure that includes a discrete or distributed capacitor. In any of the previous embodiments, the capacitive coupling structure might be at least one of parallel conductive plates in one plane; parallel conductive plates on different planes; or interdigitally coupled lines. In any of the previous embodiments, the second antenna portion might be inductively coupled to the first antenna portion via an inductive coupling structure that includes a discrete or distributed inductor. In any of the previous embodiments, the inductive coupling structure might be at least one of a wire-wound discrete inductor or a distributed transmission line on a substrate. In any of the previous embodiments, the first signal might have a frequency in a range of 30 MHz to 6 GHz. In any of the previous embodiments, the second signal might have a frequency in a range of 24 GHz to 300 GHz. In any of the previous embodiments, the frequency of the second signal might be at least ten times greater than the frequency of the first signal. In any of the previous embodiments, the antenna system might further comprise a third antenna portion inductively coupled to the second antenna portion and configured to transmit the first signal, the first signal having been received by the third antenna portion via the first antenna portion and the second antenna portion. In any of the previous embodiments, inductive coupling between the first antenna portion and the second antenna portion and between the second antenna portion and the third antenna portion might create impedance that limits passage of the second signal between the first, second, and third antenna portions more than passage of the first signal between the first, second, and third antenna portions. In any of the previous embodiments, the second antenna portion might be disposed within a frame of a device that includes the antenna system. In any of the previous embodiments, the first antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or disposed on a circuit board within a device that includes the antenna system. In any of the previous embodiments, the second antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or disposed on a circuit board within a device that includes the antenna system. 
     In accordance with another embodiment of the present disclosure, a method for transmitting or receiving from an antenna system is provided. The method comprises transmitting or receiving, from or to a first antenna portion of the antenna system, a first signal received from or to a first feed with a frequency in a range of 30 MHz to 6 GHz, and transmitting or receiving, from or to a second antenna portion of the antenna system, a second signal received from or to a second feed with a frequency in a range of 24 GHz to 300 GHz. The second antenna portion is capacitively coupled to the second feed and inductively coupled to the first antenna portion. 
     In the previous embodiment, the second antenna portion might be capacitively coupled to the second feed via a capacitive coupling structure that includes a discrete or distributed capacitor. In any of the previous embodiments, the capacitive coupling structure might be at least one of parallel conductive plates in one plane; parallel conductive plates on different planes; or interdigitally coupled lines. In any of the previous embodiments, the second antenna portion might be inductively coupled to the first antenna portion via an inductive coupling structure that includes a discrete or distributed inductor. In any of the previous embodiments, the inductive coupling structure might be at least one of a wire-wound discrete inductor or a distributed transmission line on a substrate. In any of the previous embodiments, the second signal might be transmitted or received at a frequency at least ten times greater than a frequency of the first signal. In any of the previous embodiments, the method might further comprise transmitting the first signal from a third antenna portion of the antenna system. The third antenna portion might be inductively coupled to the second antenna portion, and the first signal might have been received by the third antenna portion via the first antenna portion and the second antenna portion. In any of the previous embodiments, inductive coupling between the first antenna portion and the second antenna portion and between the second antenna portion and the third antenna portion might create impedance that limits passage of the second signal between the first, second, and third antenna portions more than passage of the first signal between the first, second, and third antenna portions. In any of the previous embodiments, the first antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or formed on a circuit board within a device that includes the antenna system. In any of the previous embodiments, the second antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or formed on a circuit board within a device that includes the antenna system. 
     In accordance with another embodiment of the present disclosure, an antenna system comprises a first antenna portion configured to transmit a first signal received from a first feed; a second antenna portion configured to transmit a second signal received from a second feed, the second antenna portion capacitively coupled to the second feed and inductively coupled to the first antenna portion, and the second signal having a frequency greater than a frequency of the first signal; and a third antenna portion inductively coupled to the second antenna portion and configured to transmit the first signal, the first signal having been received by the third portion via the first antenna portion and the second antenna portion. 
     In the previous embodiment, the second antenna portion might be capacitively coupled to the second feed via a capacitive coupling structure that includes a discrete or distributed capacitor. In any of the previous embodiments, the capacitive coupling structure might be at least one of parallel conductive plates in one plane; parallel conductive plates on different planes; or interdigitally coupled lines. In any of the previous embodiments, the second antenna portion might be inductively coupled to the first antenna portion via a first inductive coupling structure that includes at least one discrete or distributed inductor, and the second antenna portion might be inductively coupled to the third antenna portion via a second inductive coupling structure that includes at least one discrete or distributed inductor. In any of the previous embodiments, at least one of the first inductive coupling structure or the second inductive coupling structure might be at least one of a wire-wound discrete inductor or a distributed transmission line on a substrate. In any of the previous embodiments, the first signal might be a sub 6 gigahertz signal. In any of the previous embodiments, the second signal might be a millimeter wave signal. In any of the previous embodiments, the frequency of the second signal might be at least ten times greater than the frequency of the first signal. In any of the previous embodiments, inductive coupling between the first antenna portion and the second antenna portion and between the second antenna portion and the third antenna portion might create impedance that limits passage of the second signal between the first, second, and third antenna portions more than passage of the first signal between the first, second, and third antenna portions. In any of the previous embodiments, the first antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or disposed on a circuit board within a device that includes the antenna system. In any of the previous embodiments, the second antenna portion might be at least one of disposed within a frame of a device that includes the antenna system or disposed on a circuit board within a device that includes the antenna system. 
     An advantage of the embodiments is that a combination of a sub 6 GHz antenna and a mmWave antenna takes up substantially the same amount of space as the sub 6 GHz antenna alone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating an embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 2  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 3A  is a diagram illustrating an embodiment mmWave antenna radiator; 
         FIG. 3B  is a diagram illustrating another embodiment mmWave antenna radiator; 
         FIG. 4  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 5  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 6  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 7  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 8  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 9  is a diagram illustrating another embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 10A  is a graph illustrating the performance of an embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 10B  is another graph illustrating the performance of an embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 11  is a graph illustrating the isolation between ports in an embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 12A  is a graph illustrating the performance of the sub 6 GHz antenna portion of an embodiment combination sub 6 GHz antenna and mmWave antenna system; 
         FIG. 12B  is another graph illustrating the performance of the sub 6 GHz antenna portion of an embodiment combination sub 6 GHz antenna and mmWave antenna system; and 
         FIG. 13  is a flowchart illustrating a method for transmitting from an antenna system. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The structure, manufacture and use of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable novel concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the embodiments, and do not limit the scope of the disclosure. 
     As the number of antennas included in UEs increases, the difficulty in fitting all the antennas in the limited space of a UE also increases. Embodiments disclosed herein provide an antenna system that combines a sub 6 GHz antenna and a mmWave antenna and that efficiently uses the limited space within a UE. For simplicity, the various embodiments of a combined sub 6 GHz antenna and mmWave antenna will be referred to hereinafter as the combination antenna system. 
     The embodiment combination antenna systems might be described herein as being installed in a UE, but it should be understood that the combination antenna systems could be installed in other types of devices. Also, the embodiment combination antenna systems might be described herein in terms of example shapes and sizes, but it should be understood that the antenna systems could have other shapes and sizes. In addition, signals might be described herein as being transmitted by a UE, but similar concepts might apply to signals received by a UE. 
     To achieve a high gain, mmWave antennas might be deployed in arrays of different dimensions. For example, mmWave antennas might be arranged in a 1×2 array, a 2×2 array, a 2×4 array, or an array with other dimensions. In addition, mmWave antennas might be implemented in a packaged array or other self-contained module that might have connector pins for connection to a printed circuit board (PCB). Alternatively, mmWave antennas might be printed or otherwise formed directly on either a rigid PCB or a PCB with a flexible, bendable substrate. Any such mmWave antenna configuration or combination of configurations might be appropriate for the embodiment combination antenna systems disclosed herein. 
       FIG. 1  illustrates a UE  100  that includes an idealized depiction of an embodiment combination antenna system  110 . The UE  100  may be viewed as having been cut open to reveal the combination antenna system  110  within a first section  100  of the UE  100 . Other components in the UE  100  might be contained in a second section  102  of the UE  100 . 
     The combination antenna system  110  and other combination antenna systems might be described herein as having a sub 6 GHz antenna portion A  120 , a mmWave antenna portion B  130 , and another sub 6 GHz antenna portion C  140 , where portion C  140  is optional, depending on the specific design. That is, portion A  120  is a first section of a sub 6 GHz antenna, portion B  130  is a mmWave antenna, and portion C  140  is a second section of the sub 6 GHz antenna. In other embodiments, other numbers and arrangements of the portions might be used. For example, portion C  140  might not present, and only the sub 6 GHz antenna portion A  120  and the mmWave antenna portion B  130  might be present. In other embodiments, portion B  130  might be a phased array antenna or might comprise multiple mmWave antennas. In other embodiments, the combination antenna system  110  might be represented as A/B/B/B/B/C or a similar pattern of portions. In other words, a single portion A  120  might be present, multiple instances of portion B  130  might be present, and a single portion C  140  might be present. As another example, multiple sub 6 GHz antennas and multiple mmWave antennas might be present in an A/B/C/D/E, etc., pattern, where B and D are mmWave antennas or antenna arrays and are separated by sub 6 GHz antenna portions. Although the portions are depicted as separate components, the portions might be components within a single antenna structure. 
     In an embodiment, portion A  120  is inductively coupled to portion B  130 , and portion B  130  is inductively coupled to portion C  140 , where inductively coupled means two conductors are physically and electrically connected to one another through either a discrete or a distributed inductor. Examples of inductively coupled structures include a wire-wound discrete inductor or a distributed transmission line such as a 0.254 mm wide, 2.54 mm long stripline on top of a 1.25 mm thick substrate, where the distributed transmission line has about a 10 nanohenry inductance. In another embodiment, the coupling between the sub 6 GHz portion A  120  and the mmWave antenna portion B  130  is a band pass connection with a pass of a desired sub 6 GHz band or a band stop connection with a stop band at the intended mmWave band. Because of the inductive coupling between portion A  120  and portion B  130  and between portion B  130  and portion C  140 , the connections between each of the portions have a relatively high impedance at relatively high frequencies and a relatively low impedance at relatively low frequencies. Any physical and electrical connection between components that provides a relatively high impedance between the components at relatively high frequencies and provides a relatively low impedance between the components at relatively low frequencies will be referred to herein as an impedance line. An impedance line might be any combination of electrical conductors and coils, or the microelectronic equivalent of coils, that, through inductive coupling, provides a desired impedance characteristic. For example, an impedance line might be a piece of straight or curved transmission line, or might be a single layer structure or multiple layers connected through vias. 
     In an embodiment, impedance line  170  physically and electrically connects portion A  120  to portion B  130 , and impedance line  180  physically and electrically connects portion B  130  to portion C  140 . Although the impedance lines  170  and  180  and other impedance lines shown in other drawings described herein might be depicted as single lines, it should be understood that the impedance lines  170  and  180  and other impedance lines might include various combinations of electrical conductors and coils or the microelectronic equivalent of coils. The impedance lines  170  and  180  (modeled as inductors) might allow an electrical connection at some frequencies but might substantially block an electrical connection at other frequencies. That is, because impedance is directly proportional to frequency, the sub 6 GHz signal and the mmWave signal experience different impedances when passing through the impedance lines  170  and  180 . The relatively higher frequency mmWave signal experiences a relatively high impedance at the impedance lines  170  and  180  and is thus effectively blocked from reaching and radiating from portion A  120  or portion C  140 . The mmWave signal fed in at the second feed  160  thus effectively radiates only from portion B  130 . 
     The relatively lower frequency sub 6 GHz signal, on the other hand, experiences a relatively low impedance at the impedance lines  170  and  180 . Thus, the sub 6 GHz signal fed in at the first feed  150  can radiate from portion A  120 , pass through impedance line  170  to reach portion B  130 , radiate from portion B  130 , pass through impedance line  180  to reach portion C  140 , and radiate from portion C  140 . 
     In other words, the impedance lines  170  and  180  that physically and electrically connect the mmWave antenna portion B  130  to the sub 6 GHz antenna portions A  120  and C  140  can be viewed as low pass or band pass connections. As is well known in the art, a low pass connection typically includes electrical components arranged in a circuit such that signals with a frequency lower than a cutoff frequency pass through the connection, and signals with a frequency higher than the cutoff frequency do not pass through the connection. Due to the low pass connections, a sub 6 GHz radio frequency (RF) signal can pass between the mmWave antenna portion B  130  and the sub 6 GHz antenna portions A  120  and C  140 , but a mmWave signal cannot pass between the mmWave antenna portion B  130  and the sub 6 GHz antenna portions A  120  and C  140 . 
     When reference is made herein to a signal passing through a connection or between connections, it should be understood that a negligible amount of attenuation of the signal might occur, and when reference is made herein to a signal not passing through a connection or between connections, it should be understood that the signal might be attenuated to down a negligible level. In other words, even with the high impedance experienced by the mmWave signal, at least some portion of the mmWave signal might pass from portion B  130  to portion A  120  and portion C  140 . It may be stated more generally that the mmWave signal is attenuated more from passing between portion A  120 , portion B  130 , and portion C  140  than the sub 6 GHz signal is attenuated from passing between portion A  120 , portion B  130 , and portion C  140 . That is, the inductive coupling of the impedance lines  170  and  180  almost entirely blocks the mmWave signal but causes little or no resistance for the passage of the sub 6 GHz signal. 
     In an embodiment, the combination antenna system  110  is fed by two separate feeds, one for sub 6 GHz signals and one for mmWave signals. That is, a first feed  150  feeds a sub 6 GHz signal into the sub 6 GHz antenna in portion A  120 , and a second feed  160  feeds a mmWave signal into the mmWave antenna in portion B  130 . To reduce the coupling between the sub 6 GHz system and the mmWave system, the mmWave antenna  130  is physically and electrically connected to the mmWave antenna feed  160  through a high pass connection  165  or a band pass matching circuit. As is well known in the art, a high pass connection typically includes electrical components arranged in a circuit such that signals with a frequency higher than a cutoff frequency pass through the connection, and signals with a frequency lower than the cutoff frequency do not pass through the connection. Due to the high pass connection  165 , a mmWave signal can pass from the mmWave antenna feed  160  to the mmWave antenna  130 , but a sub 6 GHz RF signal will be attenuated down to a negligible level at the mmWave antenna feed  160 . In other words, the second feed  160  is capacitively coupled (high pass) to the mmWave antenna in portion B  130 , where capacitively coupled means two conductors are physically and electrically connected to one another through either a discrete or a distributed capacitor. Examples of capacitively coupled structures include parallel conductive plates in one plane, parallel conductive plates on different planes that might or might not overlap, or interdigitally coupled lines that might be arranged in a pattern such as a square wave. Because of the capacitive coupling between the mmWave antenna feed  160  and the mmWave antenna  130 , the second feed  160  has a relatively low impedance at the relatively high mmWave frequencies and a relatively high impedance at the relatively low sub 6 GHz frequencies. The second feed  160  is therefore effectively an open circuit with respect to the sub 6 GHz antennas in portion A  120  and portion C  140 . The mmWave antenna in portion B  130  can thus be placed anywhere within an antenna structure that includes a sub 6 GHz antenna. The capacitive coupling between the mmWave antenna feed  160  and the mmWave antenna  130  is independent of the locations of the mmWave antenna feed  160  and the mmWave antenna  130 . In another embodiment, the high pass connection  165  between the second feed  160  and the mmWave antenna portion B  130  is a serial inductance/capacitance (LC) resonator (band pass), with a pass band in the targeted mmWave band. One of skill in the art will be aware of values of inductance and capacitance that might be appropriate for such a high pass connection  165 , and the embodiments disclosed herein are not limited to any specific values of inductance or capacitance in the high pass connection  165 . 
     As mentioned above, the sub 6 GHz antenna in portion A  120  and portion C  140  might transmit signals with frequencies in the range of approximately 30 MHz to approximately 6 GHz, and the mmWave antenna in portion B  130  might transmit signals with frequencies in the range of approximately 24 GHz to approximately 300 GHz. In an embodiment, where inductive impedance lines are used to couple signals between portion A  120  and portion B  130  and between portion B  130  and portion C  140 , the mmWave antenna transmits at a frequency at least ten times greater than the frequency at which the sub 6 GHz antenna transmits. Therefore, the impedance lines  170  and  180  have an impedance at least ten times greater for the mmWave antenna than for the sub 6 GHz antenna. In another embodiment, where another band pass or band stop coupling structure is used, the ratio of the mmWave signal frequency to the sub 6 GHz RF signal frequency may be less than ten while keeping enough isolation between the mmWave antenna portion B  130  and the sub 6 GHz antenna portion A  120 . The actual acceptable ratio of mmWave signal frequency to sub 6 GHz RF signal frequency depends on the frequency response of the coupling structure. 
     With the physical and electrical arrangement of components described above, the mmWave signal fed into portion B  130  can radiate substantially independently from the sub 6 GHz signal fed into portion A  120 , even though portion A  120  and portion B  130  share the same physical antenna structure of the combination antenna system  110 . In other words, the mmWave signal fed into portion B  130  might radiate almost entirely from portion B  130 , with little to no mmWave signal radiation from portion A  120  or portion C  140 . The sub 6 GHz signal fed into portion A  120 , on the other hand, might radiate from portion A  120 , from portion B  130 , and from portion C  140 , with little signal coupled into the mmWave antenna feed  160  (thus to the mmWave subsystem). Stated another way, the radiating parts of the combination antenna system  110  might be considered continuous at sub 6 GHz frequencies, but portion B  130  might be considered a discrete component at mmWave frequencies. 
     When the combination antenna system  110  is created by combining a mmWave antenna and a sub 6 GHz antenna in the configuration described herein, the design of the sub 6 GHz antenna does not need to be substantially changed, and the resulting combination antenna system  110  does not take up substantially more space than the sub 6 GHz antenna alone. Furthermore, the performance of the sub 6 GHz antenna and the performance of the mmWave antenna are not significantly hampered, despite the two antennas residing in the same physical antenna structure. 
       FIG. 2  illustrates another idealized depiction of an embodiment combination antenna system  210 . The combination antenna system  210  might be substantially similar to the combination antenna system  110  of  FIG. 1 . The combination antenna system  210  includes a partial sub 6 GHz antenna structure  220  that might be substantially similar to portion A  120  of  FIG. 1 . The combination antenna system  210  further includes one or more mmWave antenna radiators  230  that might be substantially similar to portion B  130  of  FIG. 1 . As used herein, the term “radiator” might refer to any component capable of radiating an electromagnetic wave. The partial sub 6 GHz antenna structure  220  is fed by a sub 6 GHz antenna feed  240 , and the mmWave antenna radiators  230  are independently fed by mmWave antenna feeds  250 . A low pass (or band pass/band stop) impedance line  260  physically and electrically connects the partial sub 6 GHz antenna structure  220  and the mmWave antenna radiators  230  and might be substantially similar to the impedance lines  170  and  180  of  FIG. 1 . The impedance line  260  has a relatively high impedance at relatively high frequencies and has a relatively low impedance at relatively low frequencies. Thus, the relatively low frequency signals from the sub 6 GHz antenna feed  240  can pass through the impedance line  260  to the mmWave antenna radiators  230 , but the relatively high frequency signals from the mmWave antenna feed  250  cannot pass through the impedance line  260  to the partial sub 6 GHz antenna structure  220 . Therefore, the mmWave antenna radiators  230  are effectively an open circuit with respect to the partial sub 6 GHz antenna structure  220 . The mmWave antenna radiators  230  and the mmWave antenna feed  250  are physically and electrically connected though a high pass (or band pass) connection, which effectively has high impedance at a sub 6 GHz band and effectively has low impedance at a mmWave band. Thus, the sub 6 GHz antenna feed  240  and the mmWave antenna feed  250  can function substantially independently from one another, even though the partial sub 6 GHz antenna structure  220  and the mmWave antenna radiators  230  are components in the same combination antenna system  210 . 
     The embodiment combination antenna system  200  of  FIG. 2  might be contrasted with a prior art dual-feed, dual-band antenna. In such an antenna, an RF dual-band signal is typically fed into a diplexer. Filters in the diplexer separate the RF dual-band signal into a low band feed and a high band feed. The low band feed and the high band feed are then radiated together from a shared antenna radiator. That is, both the low band feed and the high band feed are radiated from substantially all portions of the shared antenna radiator. 
       FIGS. 3A and 3B  demonstrate possible embodiments of mmWave antenna radiators  310  and mmWave antenna feeds  320 . mmWave antenna radiators  310  and mmWave antenna feeds  320  might be similar to radiator  230  and feed  250 , respectively, in  FIG. 2  or portion B  130  and feed  160 , respectively, in  FIG. 1 . In  FIG. 3A , multiple mmWave element antennas  310  are fed through a power distribution network  330 , which is frequency selective, high pass or band pass, to pass through a mmWave signal and reject a sub 6 GHz RF signal. The power distribution network  330  might be an RF power distribution network. The mmWave signals from the feed  320  might be split into two signals by a power splitter and then split into four signals by cascaded power splitters. Thus, mmWave power is distributed into four element antennas  310  as in the  FIG. 3A . On the receiving side, the mmWave signals collected through the element antennas  310  might be combined through the splitters (combiners) and summed at the antenna feed. The power distribution network  330  can be used to control how much power is distributed to each element antenna  310 . By varying the path delay between the feed  320  and the element antenna feeds, the power distribution network  330  can control the relative signal phase between each element antenna  310 , thus steering a fixed beam in a certain direction. The power distribution network  330  by nature is frequency dependent. Distribution network  330  with feed  320  might be equivalent to feed  250  in  FIG. 2  or feed  160  in  FIG. 1 . A single feed  320  is used to feed the antenna, and the antenna is treated as a single antenna. Between each element antenna  310 , a low pass (or band pass) connection  300  is used, which has high impedance at the mmWave band and low impedance at the sub 6 GHz band. The connections  300  might be substantially similar to the impedance lines  170  and  180  of  FIG. 1  and the impedance line  260  of  FIG. 2 . Multiple element antenna  310  with connections  300  is equivalent to the mmWave antenna radiator  230  in  FIG. 2  or portion B  130  in  FIG. 1 . 
     In  FIG. 3B , multiple individually fed antennas  310  are present. Each element antenna  310  is coupled to an adjacent element antenna  310  though a low pass (or band pass) connection  300 . Multiple element antenna  310  with connection  300 , marked as  340 , is equivalent to the mmWave antenna radiator  230  in  FIG. 2  or portion B  130  in  FIG. 1 . The multiple feeds  320  are equivalent to feed  250  in  FIG. 2  or feed  160  in  FIG. 1 . In an embodiment, the connection  300  is realized with an inductive impedance line, which has impedance proportional to frequency. In an embodiment, a high pass connection (not shown) between feed  320  and antenna  310  or between power distribution network  330  and antenna  310  is realized by a capacitive coupling structure, which has impedance inversely proportional to frequency. The high pass connection (not shown) between feed  320  and antenna  310  or between power distribution network  330  and antenna  310  might be substantially similar to the high pass structure  165  of  FIG. 1 . 
       FIG. 4  illustrates a UE  400  that includes an embodiment combination antenna system shown in more detail. A sub 6 GHz antenna  410  includes a first sub 6 GHz antenna portion  420  that might be substantially similar to portion A  120  of  FIG. 1 . The sub 6 GHz antenna  410  also includes a mmWave antenna array  430  that might be substantially similar to portion B  130  of  FIG. 1  or structure  340  of  FIG. 3B . In this example, two mmWave antennas are present in the mmWave antenna array  430 , but in other embodiments, other numbers of mmWave antennas might be present in the mmWave antenna array  430 . Also, the mmWave antenna array  430  might have other arrangements, such as a square grid, a triangular grid, or a hexagonal grid, and all antenna elements or a portion of the antenna elements might be present in an array. In an embodiment, the mmWave antenna array  430  is a patch antenna. In another embodiment, the mmWave antenna array  430  is a monopole antenna. The two mmWave antennas in the mmWave antenna array  430  are coupled to each other through an impedance line  450 , which has impedance proportional to frequency. The sub 6 GHz antenna  410  further includes a second sub 6 GHz antenna portion  440  that might be substantially similar to portion C  140  of  FIG. 1 . The first sub 6 GHz antenna portion  420  is connected to the mmWave antenna array  430  and the mmWave antenna array  430  is connected to the second sub 6 GHz antenna portion  440  by impedance lines  450  that might be substantially similar to the impedance lines  170  and  180  of  FIG. 1 . The first sub 6 GHz antenna portion  420  is fed by a sub 6 GHz antenna feed  460  that might be substantially similar to the first feed  150  of  FIG. 1 . The mmWave antenna array  430  is fed by a mmWave antenna element feed  470  that might be substantially similar to the second feed  160  of  FIG. 1  or feeds  320  in  FIG. 3B . 
     The combination of the first sub 6 GHz antenna portion  420 , the mmWave antenna array  430 , the second sub 6 GHz antenna portion  440 , and the impedance lines  450  might be viewed as being substantially similar to the combination antenna system  110  of  FIG. 1 . Alternatively, the mmWave antenna array  430  might be viewed as residing within the sub 6 GHz antenna  410  and as connected to the first sub 6 GHz antenna portion  420  of the sub 6 GHz antenna  410  and the second sub 6 GHz antenna portion  440  of the sub 6 GHz antenna  410  by the impedance lines  450 . 
       FIG. 5  illustrates a UE  500  that includes an embodiment combination antenna system  510  with components having different shapes than those in  FIG. 4 . The combination antenna system  510  includes a first sub 6 GHz antenna portion  520  that might support multiple sub 6 GHz bands and that might be substantially similar to portion A  120  of  FIG. 1 . The combination antenna system  510  also includes a mmWave antenna array  530  that might be substantially similar to portion B  130  of  FIG. 1  or structure  340  of  FIG. 3B . The combination antenna system  510  further includes a second sub 6 GHz antenna portion  540  that might be substantially similar to portion C  140  of  FIG. 1 . The first sub 6 GHz antenna portion  520  is connected to the mmWave antenna array  530  and the mmWave antenna array  530  is connected to the second sub 6 GHz antenna portion  540  by impedance lines  550  that might be substantially similar to the impedance lines  170  and  180  of  FIG. 1 . 
       FIG. 6  illustrates a UE  600  that includes an embodiment combination antenna system  610  with components having a different arrangement than those in the previous figures. The combination antenna system  610  includes a mmWave antenna array  620  that might be substantially similar to portion B  130  of  FIG. 1  or structure  340  of  FIG. 3B . In this example, the mmWave antenna array  620  is a 2×2 array, but only two of the element antennas are used as sub 6 GHz antenna radiators. These two mmWave antennas are coupled to each other through an impedance line, which has impedance proportional to frequency. The combination antenna system  610  also includes a Wi-Fi 5 GHz antenna  630  that might be substantially similar to portion A  120  of  FIG. 1 . The combination antenna system  610  further includes a sub 6 GHz antenna portion  640  that might be substantially similar to portion C  140  of  FIG. 1 . The combination antenna system  610  also includes a Wi-Fi 5 GHz antenna ground  650 . The mmWave antenna array  620 , the Wi-Fi 5 GHz antenna  630 , the sub 6 GHz antenna portion  640 , and the Wi-Fi 5 GHz antenna ground  650  might work together as an inverted-F type antenna (IFA) at sub 6 GHz frequencies. Although not shown in the figure, the mmWave antenna array  620  might be physically and electrically connected to the Wi-Fi 5 GHz antenna  630  and the sub 6 GHz antenna portion  640  by impedance lines that might be substantially similar to the impedance lines  170  and  180  of  FIG. 1  and the impedance line  260  of  FIG. 2 . 
       FIG. 7  illustrates a UE  700  that includes an embodiment combination antenna system  710  with mmWave antenna and sub 6 GHz antenna portions having different arrangements than those in  FIG. 6 . The combination antenna system  710  includes a mmWave antenna array  720  that might be substantially similar to portion B  130  of  FIG. 1  or structure  340  of  FIG. 3B . In this example, the mmWave antenna array  720  is a 1×3 array. The combination antenna system  710  also includes a Wi-Fi 5 GHz antenna  730  that might be substantially similar to portion A  120  and portion C  140  of  FIG. 1 . In this example, the Wi-Fi 5 GHz antenna  730  has the form of a loop type antenna. Although not shown in the figure, the mmWave antenna array  720  might be physically and electrically connected to the Wi-Fi 5 GHz antenna  730  by impedance lines that might be substantially similar to the impedance lines  170  and  180  of  FIG. 1  and the impedance line  260  of  FIG. 2 . 
       FIG. 8  illustrates a UE  800  that includes another embodiment combination antenna system. In this example, only a mmWave antenna array portion  810  and an impedance line portion  820  of the combination antenna system are shown. The figure is intended to illustrate an example location where the mmWave antenna array  810  and the impedance lines  820  might be located within the UE  800 , and thus the mmWave antenna array  810  and the impedance lines  820  are not shown in detail. The mmWave antenna array portion  810  may be a parasitic patch element that is fed capacitively. The mmWave feeding structure may not be part of a sub 6 GHz radiator. The mmWave element patches are connected through impedance lines  820 , which have impedance proportional to frequency. A frame  830  surrounds the UE  800 , and in this example, the mmWave antenna array  810  and the impedance lines  820  are embedded or otherwise disposed inside the frame  830 . A dashed line  840  represents a sub 6 GHz antenna radiator and indicates that the frame  830  is radiating at both sub 6 GHz frequencies and mmWave frequencies. In an embodiment, a sub 6 GHz antenna might be disposed in the UE  800  in such a manner instead of or in addition to the mmWave antenna array  810 . 
       FIG. 9  illustrates a UE  900  that includes another embodiment combination antenna system. In this example, again only a mmWave antenna array portion  910  and an impedance line portion  920  of the combination antenna system are shown. The figure is intended to illustrate another example location where the mmWave antenna array  910  and the impedance lines  920  might be located within the UE  900 , and thus the mmWave antenna array  910  and the impedance lines  920  are not shown in detail. In this example, the mmWave antenna array  910  and the impedance lines  920  are printed on a PCB  930  in the UE  900 . An electrical connection between the mechanical parts of the UE  900  and the PCB  930  might be realized by using a c-clip. For example, a c-clip might connect to the frame of the UE  900  and its pad might connect to the traces on the PCB  930 . A dashed line  940  again represents a sub 6 GHz antenna radiator and indicates that the combination antenna system is radiating at both sub 6 GHz frequencies and mmWave frequencies. In an embodiment, a sub 6 GHz antenna might be disposed in the UE  900  in such a manner instead of or in addition to the mmWave antenna array  910 . 
       FIG. 10A  is a graph  1000  illustrating antenna loss for an embodiment combination antenna system, such as combination antenna system  410  of  FIG. 4 .  FIG. 10B  is a graph  1050  illustrating antenna efficiency for an embodiment combination antenna system, such as combination antenna system  410  of  FIG. 4 . 
       FIG. 11  is a graph  1100  illustrating the isolation between ports in an embodiment combination antenna system, such as between the first feed  150  and the second feed  160  of  FIG. 1 . It can be seen that there is little coupling between the ports, and that at sub 6 GHz frequencies, the mmWave port acts like an open circuit. 
       FIG. 12A  is a graph  1200  illustrating an aspect of the performance of the sub 6 GHz antenna portion of an embodiment combination antenna system, such as combination antenna system  510  of  FIG. 5 .  FIG. 12B  is a graph  1250  illustrating another aspect of the performance of the sub 6 GHz antenna portion of an embodiment combination antenna system, such as combination antenna system  510  of  FIG. 5 . 
     It can be seen from the graphs that the presence of both the sub 6 GHz antenna and the mmWave antenna in the same physical antenna structure does not have a significant negative impact on the performance of the two antennas. 
       FIG. 13  is a flowchart illustrating a method  1300  for transmitting or receiving from an antenna system. At block  1310 , a first signal received from or to a first feed is transmitted or received from or to a first antenna portion of the antenna system with a frequency in a range of 30 MHz to 6 GHz. At block  1320 , a second signal received from or to a second feed is transmitted or received from or to a second antenna portion of the antenna system with a frequency in a range of 24 GHz to 300 GHz. The second antenna portion is capacitively coupled to the second feed and inductively coupled to the first antenna portion. 
     While this disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the disclosure, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.