Patent Publication Number: US-2022238999-A1

Title: Close-range communication systems for high-density wireless networks

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/141,812, filed Jan. 26, 2021, the entire contents of which is being incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure pertains to wireless networks; more specifically, to improving quality of wireless communication links between network devices while reducing interference and noise from other network devices present in high-density wireless networks. 
     BACKGROUND 
     Modern wireless networks often support connections of multiple devices that transmit wireless signals concurrently with other devices. Simultaneous wireless transmission increases the likelihood of interference that can be detrimental to reliability and throughputs of various individual communication links. Furthermore, simultaneous transmission produces electromagnetic noise that can further degrade quality of wireless communications. As the size of modern transmitting and receiving devices tends to decrease while spatial density of such devices often increases significantly (together with the demands to the throughput of communication links), ensuring adequate quality of network connections is important for continuing progress of the wireless technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts schematically a high-density wireless environment, in accordance with some implementations of this disclosure. 
         FIG. 2A  is a schematic depiction of an example wireless network device capable of supporting close-range communications without significantly contributing to the noise and interference at far field, in accordance with some implementations. 
         FIG. 2B  is a schematic illustration of bandwidth control and channel selection during close-range transmission and/or receptions by a wireless networking device operating in accordance with some implementations of the present disclosure. 
         FIG. 3A  is a schematic depiction of an example antenna assembly that enables efficient close-range communication while preventing far-field noise and interference, in accordance with some implementations of the present disclosure. 
         FIG. 3B  depicts a rectangular close-range loop antenna. 
         FIG. 3C  depicts a circular close-range loop antenna. 
         FIG. 4A  is a schematic spatial characterization of the efficiency of a close-range communication that involves an antenna constructed in accordance with some implementations of the present disclosure. 
         FIG. 4B  depicts schematically an angular misalignment between transmitting and receiving antennas that still allows for an efficient close-range wireless communication. 
         FIG. 4C  depicts schematically a lateral misalignment between transmitting and receiving antennas that still allows for an efficient close-range wireless communication. 
         FIG. 4D  is a schematic illustration of a wireless communication device capable of supporting wireless communication links to multiple end devices, in accordance with some implementations of the present disclosure. 
         FIG. 5A  depicts an example side-by-side placement of a close-range antenna and a wireless network processor. 
         FIG. 5B  depicts an example placement of a close-range antenna and a wireless network processor on opposite surfaces of a laminate. 
         FIG. 5C  depicts an example placement in which a close-range antenna is integrated with wireless network processor into a single bundle device. 
         FIG. 5D  depicts an example cross section of the combined bundle device of  FIG. 5C . 
     
    
    
     DETAILED DESCRIPTION 
     High-density networks include devices, e.g., sensor arrays, whose circuit boards support multiple transmitters. High-density networks may also include charging pads (charging mats) that support wireless simultaneous charging connections of multiple devices, testing benches used in device manufacturing, wireless access points in public spaces, printed circuit boards with multiple transmitters, and the like. In some instances, tens of devices may be located within a distance of several centimeters (e.g., on printed circuit boards), or hundreds of devices may be located within a distance of one meter (e.g., on testing benches). Conventional solutions to simultaneous wireless communications of multiple devices include targeted placement of antennas, formation of complex interference patterns of transmitted radiation (beamforming) using multiple-input multiple-output (MIMO) antennas with maxima in the directions of targeted devices (and minima in the direction of other, unintended, devices), using carrier-sense multiple access with collision avoidance (CSMA/CA), code-division multiple access (CDMA) or time-division multiple access (TDMA), in which the same channels are shared among multiple communication links in the time or spectral domains. Such solutions have a number of shortcomings, including expensive MIMO antenna designs, reduced data transmission rates, lost air time, complex protocols and software for time/spectral multiplexing, poor robustness against adjacent channel interference, large-size hardware required for implementation of such solutions, and so on. 
     Aspects and implementations of the present disclosure address these and other limitations of the existing technology by enabling systems and methods of close-range communications that provide good signal strength in the near field communications but have reduced signal strength in the far field domain. This, on one hand, ensures that nearby devices A and B have a robust and reliable network communication capable of transmitting and receiving large amounts of data quickly and efficiently. On the other hand, because of a sufficiently fast decay of the radiated field with distance, the A-B communication link adds little in the way of interference and noise that might affect communications of other, e.g., C, D, etc., devices. In turn, if other devices deploy the same or a similar technology, the A-B communication link remains largely free from adverse interference and noise that may be caused by other wireless communications occurring nearby. Such a close-range communication ability is enabled by systems and components that include one or more close-range antennas, as described herein. 
       FIG. 1  depicts schematically a high-density wireless environment, in accordance with some implementations of this disclosure. Depicted are charging pads  102  and  120  that support wireless charging of multiple devices, e.g., smart phones  104 ,  112 ,  122 , and  126 , tablet computers  106 ,  130 , and  132 , smart watches  108  and  128 , earbuds  110  and  134 , camera  124 , etc. Connectivity of different devices to charging pads  102  and  120  may be supported by various antennas  116  and  136  operating in accordance with various systems and techniques described herein. Even though illustrated in  FIG. 1  are charging pads, implementations described herein may equally apply to any other networks with high densities of communicating devices. 
     In some implementations, close-range communication may be mediated by relatively high-frequency radio carriers, e.g., 60 GHz radio waves having a wavelength of about 5 mm in vacuum (or air). In other implementations, however, communications that use radio waves with lower frequencies, e.g., 30 GHz or lower, may similarly benefit from systems described in this disclosure. Higher frequency waves have a tendency to scatter and attenuate faster than lower frequency waves, e.g., communications that utilize 60 GHz waves generally do not have a range of 5 GHz or 2.4 GHz wireless networks. Higher frequency radio waves, however, enable higher bandwidths and, correspondingly, faster data exchanges. Even though multiple references to the 60 GHz band are made throughout this disclosure, it should be understood that the 60 GHz band may have a significant bandwidth, e.g., 8 GHz, so that the actual transmission of radio waves may take place within a broad range of frequencies, e.g., 57-64 GHz band (or 57-71 GHz, in some countries). The 60 GHz communications may use Wireless Gigabit (WiGig) IEEE 802.11ad standard with data throughput up to 4,600 Mps (or even higher, under favorable conditions), namely four times faster than the IEEE 802.11ac standard (which uses 5 GHz band) allows. 
     As depicted by the blowout section of  FIG. 1 , a wireless communication between any devices (e.g., charging pad  102  and smart phone  104 ) may be facilitated by a close-range antenna assembly (e.g., antenna assembly  115 ), which may include a close-range antenna  150 . As described in more detail in connection with  FIG. 3 , close-range antenna  150  may include, in one or more implementations, a loop antenna operating in conjunction with a specially engineered substrate. The loop antenna may be of a small size in order to reduce far-field radiation. The loop antenna may be in proximity to a substrate (e.g., dielectric substrate) that separates the loop antenna from a conducting layer. The conducting layer enhances the electromagnetic field in the near-field region by redirecting (reflecting) upwards the field emitted in the downward direction. 
       FIG. 2A  is a schematic depiction of an example wireless network device  200  capable of supporting close-range communications without significantly contributing to the noise and interference at far field, in accordance with some implementations. Wireless network device  200  may be a station device e.g., a charging pad  102  or charging pad  120 , a testing bench, a sensor array, an access point of a public service network, and so on. Wireless network device  200  may be capable of obtaining or generating digital data, forming data frames that include generated data, transforming the data frames into data packets, and transmitting the data packets over a wireless connection, among other operations. Wireless network device  200  may also be capable of performing these operations in a reverse order, when data packets are being received from another device. Modules and components of wireless network device  200  may be operating in accordance with any suitable wireless protocol, e.g., IEEE 802.11ad protocol. 
     Wireless network device  200  may include close-range antenna  202  capable of transmitting electromagnetic waves, receiving electromagnetic waves, or both. Close-range antenna  202  may be communicatively coupled to a suitable feed line (not shown) that delivers a transmission (TX) radio signal to close-range antenna  202  or obtains a reception (RX) radio signal received by antenna  202 . The feed line may be any suitable transmission line, waveguide, and the like. The feed line may be coupled to close-range antenna  202  via any suitable coupling mechanism, e.g., capacitive coupling, inductive coupling, combined capacitive-inductive coupling, direct contact coupling, and the like. Close-range antenna  202  may be supported by substrate  204 . Substrate  204  may be or include any printed circuit board. As described in more detail below in conjunction with  FIG. 3 , substrate  204  may include any number of conducting and/or non-conducting (insulating or dielectric) layers deposited on a printed circuit board or any other type of support. 
     In some implementations, substrate  204  may be deposited directly over a wireless network processor (WNP)  206 . In some implementations, WNP  206  may be located differently, e.g., side-to-side with close-range antenna  202 . WNP  206  may perform a number of functions, including but not limited to authenticating wireless connections, forming, processing, routing, and scheduling for transmission data packets, performing cryptographic encoding and decoding of the data packets, coordinating data packet transmission. WNP  206  may perform operations for both TX and RX data exchanges. WNP  206  may have a radio component which includes filters (e.g., band-pass filters), low-noise radio-frequency amplifiers, down-conversion mixer(s), intermediate-frequency amplifiers, analog-to-digital converters, inverse Fourier transform modules, deparsing modules, interleavers, error correction modules, scramblers, and other (analog and/or digital) circuitry that may be used to process modulated signals received by close-range antenna  202 . The radio component may provide the received (and digitized) signals to a physical layer (PHY) component of WNP  206 . During reception, the PHY component may convert the digitized signals into frames that may be fed into a media access control (MAC) component of WNP  206 . The MAC component may transform frames into data packets. During transmission, data processing may occur in the opposite direction, with the MAC component transforming data packets into frames that are then transformed by PHY component into digital signals provided to the radio component. The radio component may convert digital signals into radio signals and transmit the radio signals using close-range antenna  202 . In some implementations, the radio component, the PHY component, and the MAC component of WNP  206  may be implemented on a single integrated circuit. 
     Wireless network device  200  may include a software stack  208  that includes one or more applications that use wireless communications to transmit and/or receive data packets or other types of wireless signals. For example, software stack  208  may include a smart sensor array application, a data download/upload application, a video/audio application, a computational application, a testing application, or any other type of application that may be instantiated on example wireless network device  200 . In some implementations, an application that is making use of WNP  206  may be a charging application that utilizes a power of RX radio waves to charge one or more batteries of wireless network device  200 . Similarly, an application that is making use of WNP  206  may utilize TX waves to provide charging power to one or more end devices that are in a wireless communication with wireless network device  200 . Software stack  208  may be loaded in memory  210 , which may be (or include) any non-volatile, e.g., read-only (ROM) memory, and volatile, e.g., random-access (RAM), memory. 
     Wireless network device  200  may include one or more central processing units (CPUs)  212 . In some implementations, CPU  212  may include one or more finite state machines (FSMs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASIC), or the like. Wireless network device  200  may have a single CPU  212  that executes various operations of close-range communications in cooperation with WNP  206 . In some implementations, CPU  212  may perform operations of software stack  208  whereas all (or most) wireless communication operations are performed by WNP  206 . 
     Wireless network device  200  may also include a power management unit (PMU)  214  to manage clock/reset and power resources. Wireless network device  200  may further include an input/output (I/O) controller  216  to enable communications with other external devices (including non-network devices) and structures. In some implementations, I/O controller  216  may enable a general purpose I/O (GPIO) interface, a USB interface, a PCM digital audio module, and other I/O components. 
     Wireless network device  200  may be capable of a wireless connectivity (including simultaneous and concurrent connectivity) with more than one network. Wireless network device  200  may be capable of connectivity to various types of networks, including wireless local area networks (WLAN), wide area networks (WAN), personal area networks (PAN), mesh networks, internet-of-things networks, and the like, or any combination thereof. Wireless network device  200  may be capable of connectivity at 60 GHz as well as at 30 GHz, 5 GHz, 2.4 GHz, or at any other suitable band. Wireless network device  200  may, therefore, have multiple antennas configured to enable connectivity at different bands. In some implementations, wireless network device  200  may be capable of connectivity with multiple networks using the same band. For example, wireless network device  200  may be capable of close-range connectivity (e.g., up to several centimeters) at 60 GHz and a longer-range (e.g., several meters or longer) WiGig connectivity at the same 60 GHz band. This dual capability may be facilitated by wireless network device  200  having multiple 60 GHz antennas, e.g., close-range antenna  202  and a longer-range antenna (not depicted in  FIG. 2A  for conciseness). In some implementations, the two antennas may be separated from each other by a distance of several centimeters, to reduce interference. Some of the additional antennas of wireless network device  200  may be MIMO antennas deployed in the context of other techniques referenced above. For example, WiGig antenna(s) may be MIMO antenna(s) to be used with beamforming techniques, which may be utilized to direct maxima of beamformed signals away from close-range antenna  202 . In some implementations, close-range antenna  202  may be a loop antenna whereas a WiGig antenna may be a dipole (or patch) antenna. 
     Various components of wireless network device  200  may be implemented as parts of a single integrated circuit (IC) (e.g., disposed on a single semiconductor die). For example, WNP  206  and CPU  212  may so be implemented. Close-range antenna  202  may also be disposed on the same die, although in some implementations, close-range antenna  202  and/or other parts of wireless network device  200  may be implemented on different dies. For example, close-range antenna  202  may be implemented on a die that is separate from a die on which WNP  206  (or CPU  212 ) is implemented. One or more dies that implement various components of wireless network device  200  may also host multiple other components. For example, a die that supports close-range antenna  202  may further host multiple other antennas. 
     In some implementations, wireless network device  200  may have a tunable matching network (e.g., as part of WNP  206 ) configured to control channel selection and channel bandwidth used by close-range antenna  202 .  FIG. 2B  is a schematic illustration of bandwidth control and channel selection during close-range transmission and/or receptions by a wireless networking device operating in accordance with some implementations of the present disclosure. The top panel of  FIG. 2B  depicts a total available frequency bandwidth (e.g., 8 GB interval of 57-65 GHz frequencies, or any other suitable interval) split into four channels (or any other number M of channels), e.g. four 2 GB channels, as may be set up by the tunable matching network. The tunable matching network may further select (indicated by shadowing) channel k for transmission (and/or reception) by close-range antenna  202 . (In some implementations, separate channels for transmission and reception may be selected.) At a later time, WNP  206  (or CPU  212 ) may determine that multiple other devices have joined the network at nearby locations. To decrease interference, the tunable matching network may reconfigure (e.g., upon instructions from a lead/router device of the network) transmission (and/or reception) by close-range antenna  202  to one of channels of a smaller (or larger) bandwidth. For example, as depicted by the bottom panel of  FIG. 2B , the total available frequency bandwidth may be split into a different number of channels N, e.g., eight 1 GHz channels. The tunable matching network may further select (as indicated by shadowing) a narrower channel j for transmission (and/or reception) by close-range antenna  202 . A similar channel reconfiguration (e.g., back to a smaller number of broader channels) may be performed at any moment, as dictated by the current conditions of the environment and/or the amount of data that needs to be communicated. Generally, a larger number of narrower channels may be favored when reducing interference/noise is important, whereas a smaller number of broader channels may be used when a greater throughput is desired. 
     Additional channel selection control provided by the tunable matching network may include polarization control. Specifically, each channel may support two sub-channels having different polarizations, e.g., perpendicular linear polarization, circular (or elliptical) polarizations rotating in opposite directions, and the like. Two communication links deploying different polarizations may be robust against mutual interference even when using the same frequency. In some implementations, two different polarizations may be generated by controlling the current in the antenna provided by WNP  206 . 
       FIG. 3A  is a schematic depiction of an example antenna assembly  300  that enables efficient close-range communication while preventing far-field interference and noise, in accordance with some implementations of the present disclosure. Depicted is a loop antenna  302  supported by a substrate  304 . Shown is one possible substrate  304  that includes a conducting layer  308  and an insulating (non-conducting) layer  306  that separates loop antenna  302  from the conducting layer  308 . In some implementations, both the conducting layer  308  and the insulating layer  306  may be manufactured during the same deposition process on top of a wafer (not depicted for simplicity of viewing). Loop antenna  302  may be coupled to a feed line  312 , which may be a waveguide, a coaxial cable, a transmission line (e.g., a line that includes two or more wires), and the like. The feed line  312  may lead to an antenna matching network (not shown), which may include impedance transformer to interface loop antenna  302  with a radio frequency amplifier (e.g., of WNP  206  in  FIG. 2A ) in a way that minimizes undesirable power losses during signal transmission/reflection. 
     In some implementations, an example antenna assembly  300  enables efficient close-range communication but produces a reduced far field. The shape of the loop antenna  302  ensures that, unlike dipole antennas, emission by the antenna is of a magnetic dipole type, which has a reduced strength (compared with dipole or patch antennas) in the far field domain (e.g., at distances from the loop antenna  302  that are at least several times the wavelength of the emitted waves). Dimensions of close-range antenna  302  may be comparable to or smaller than the wavelength of the waves in vacuum, e.g., λ 0 =c/f≈5 mm at operational frequency f=60 GHz. In some implementations, a circumference of the antenna may be in the millimeter range, e.g., 1-2 mm.  FIG. 3B  and  FIG. 3C  are depictions of various possible designs of the loop antenna  302 , with  FIG. 3B  depicting a rectangular close-range loop antenna and  FIG. 3C  depicting a circular close-range loop antenna. 
     In some implementations, the loop antenna  302  may have a square shape with length L and width W being approximately equal, L≈W. In some implementations, the size of the antenna (e.g., its length L, width W, or diameter D) may be less than a quarter wavelength of the transmitted/received waves: L,W&lt;λ 0 /4 (or D&lt;λ 0 /4). In some implementations, the size of the antenna may be less than one eighths of the wavelength of the transmitted/received waves: L, W&lt;λ 0 /8 (or D&lt;λ 0 /8). For example, in some implementation, L≈W≈0.3−0.5 mm. In some implementations, the shape of the loop antenna  302  may be rectangular, but not square. In some implementations, the shape of the loop antenna  302  may be non-rectangular, e.g., being of a triangular, hexagonal, or some other polygonal form. The thickness of the wire of which the loop antenna  302  is made may be different in different implementations, e.g., T≈0.05 mm in one non-limiting example. 
     Conducting layer  308  (herein also referred to as a conducting screen) may be made of a good conductor, such as copper, silver, gold, or some other conductor with the conductivity at least 10 6  Siemens/m. In contrast, insulating layer  306  may be made of a dialectic or a poor conductor, such as an undoped silicon, silicon dioxide, or some other insulating material with the conductivity at most 10 2  Siemens/m. Conducting layer  308  may serve multiple purposes. Firstly, it prevents emission of waves into the lower hemisphere (referring to geometry of  FIG. 3A ) and thus maintains electromagnetic energy above the conducting layer  308 . This reduces losses and decreases interference with devices that may be located on the other side of conducting layer  308 . Secondly, electric currents and charges generated in the conducting layer  308  amount to an appearance of an image loop  310 , in which (as depicted in  FIG. 3A ) electric current circulates in a direction opposite to the direction of electric current in the loop antenna  302 . If d is the thickness of the insulating layer  306 , the image loop  310  is located at distance 2d under the loop antenna  302 . 
     The existence of the image loop  310  negates significantly the electromagnetic field in the far field domain (which may be viewed as a quadrupole magnetic radiation from two oppositely circulating loop currents). In the near field, however, the negating effect of the image loop  310  is less significant. In some implementations, additional increase in the near filed may be achieved by constructive interference of the field emitted by the loop antenna  302  and the image loop  310 . More specifically, if the square root of the dielectric constant of the insulating layer  306  is n, the wavelength of electromagnetic waves in the insulating layer  306  is λ=λ 0 /n. For example, for silicon the square root of the dielectric constant is n≈3.45, and for silicon dioxide n≈1.95. For the waves propagating in the vertical direction, the additional phase acquired by the field emitted by the image loop  310  is ϕ2π×2d/λ, which for d≈λ/4 amounts to the π phase shift. This phase shift compensates for the opposite direction (relative to the loop antenna  302 ) of the electric current in the image loop  310 , so that the electromagnetic fields produced by the two loops interfere constructively. In some implementations, the exact condition of constructive interference need not be satisfied, as an enhancement (albeit less than the maximum possible) may be achieved for phase shifts that are within ϕ∈(3π/4, 5π/4), which amounts to thickness of the insulating layer  306  being within the range d∈(3λ/16, 5λ/16). 
     In one example implementation, the conducting layer is at a distance d=0.306 mm of a silicon layer, for which λ≈1.45 mm. Accordingly, the maximum of the sum of the two waves is achieved for d=λ/4≈0.36 mm whereas at least some enhancement is present as long as d∈(0.27 mm, 0.45 mm). 
     In another example implementation, the conducting layer is at a distance d=0.69 mm of the glass-reinforced epoxy laminate material FR4, for which n=2.14 and λ≈2.336 mm. Accordingly, the maximum of the sum of the two waves is achieved for d=λ/4≈0.6 mm whereas at least some enhancement is present as long as d ∈(0.44 mm, 0.74 mm). 
     In some implementations, an efficient antenna may be constructed outside the range of optimal enhancement. For example, in yet another implementation, the conducting layer is at a distance d=0.4 mm of the multi-layered material MCL-E-770G for which n=2.14 and λ≈2.336 mm. Accordingly, the maximum of the sum of the two waves is achieved for d=λ/4≈0.59 mm whereas at least some enhancement is present as long as d ∈(0.44 mm, 0.74 mm), so that the distance d is outside the range of enhancement. 
     In some implementations, the thickness of the insulating layer  306  may be kept under half the wavelength in the respective material, d&lt;&lt;λ/2. In some implementations, as highlighted by the above-referenced examples of the FR4 and MCL-E-770G materials, the insulating layer  306  may be a composite material made of multiple layers having somewhat different dielectric constants. For example, insulating layer  306  made mostly of silicon may also include a layer of silicon dioxide (which may be a layer that is directly in contact with the loop antenna  302 ). 
       FIG. 4A  is a schematic spatial characterization of the efficiency of a close-range communication that involves an antenna constructed in accordance with some implementations of the present disclosure. Depicted is a part  400  of a wireless network that includes a TX(RX) antenna assembly  402  capable of transmitting (or receiving) radio waves and an RX(TX) antenna assembly  404  capable of receiving (or transmitting) the radio waves and establishing a wireless communication link between respective devices (not shown explicitly) associated with the antenna assemblies  402  and  404 . The antenna assemblies  402  and  404  may include close-range antennas configured to produce (when operating in a transmitting mode) electromagnetic field that has a signal strength sufficient for a reliable close-range communication while also having a reduced reach of the electromagnetic radiation into the far filed region. For example, when TX(RX) antenna assembly  402  is operating in a transmitting mode, several zones may be defined as being formed around an antenna  403  (e.g., a loop antenna) of the assembly. 
     Within an active zone  406 , located inside a region depicted schematically with a dot-dashed line, the strength of the signal transmitted by antenna  403  may be at or above a certain first threshold S 1 . The first threshold may depend on the size and other characteristics of a receiving antenna of the RX(TX) antenna assembly  404 , on settings of amplifiers and other circuitry of the receiving device coupled to RX(TX) antenna assembly  404 , and the like. In one example non-limiting implementation, S 1 =−25 dB (whereas in other implementations, different threshold values, e.g., −20 dB, −30 dB, may exist). A good-quality communication link may be established inside the active zone  406  where signal strength S&gt;S 1 . A high-density network environment may be designed and set up in a way that limits a number of devices in the active zone  406  to a transmitting device and a receiving device with no other devices placed inside the active zone  406 . 
     Outside the active zone  406  but within a marginal zone  408 , depicted schematically with a dotted line, the strength of the signal transmitted by antenna  403  may be above a certain second threshold S 2  that is lower the first threshold. The second threshold may likewise depend on the specifics of the receiving device. In one example non-limiting implementation, S 2 =−35 dB (or some other value, e.g., S 2 =−30 dB, −40 dB, . . . ). A communication link with a receiving device inside the marginal zone  408  may be of a borderline quality. Accordingly, a high-density network environment may be designed and set up in such a way that placement of directly communicating devices is avoided in the marginal zone  408 , where S 1 &gt;S&gt;S 2 . Likewise, placement of other devices within the marginal zones of two directly communicating devices may similarly be avoided, to limit effects of interference and noise generated by these communicating devices. 
     Outside the marginal zone  408  is a quiet zone  410  where the strength of the signal transmitted by antenna  403  is below the second threshold S 2 . Devices in the quiet zone  410  do not receive detectable signals (or interference/noise) produced by the communicating devices. Similarly, two communicating devices that are within each other&#39;s active zone  406  are not disturbed by interference/noise produced by other devices of those other devices are located in the quiet zone  408 . The loop antennas (and, more generally, the antenna assemblies) may be configured to make the marginal zone  408  as narrow as possible, to reduce the amount of space where quality of transmission/reception is borderline while interference and noise are substantial. 
     The boundary of the active zone  406  (and, similarly, of the marginal zone  408 ) may be identified from a signal strength map S(x, y, z) (the third dimension y is implied but not depicted explicitly in  FIG. 4A ) as the surface z(x, y) on which S(x, y, z)=S 1  (and similarly for the boundary between the marginal zone  408  and the quiet zone  410 ). Alternatively, the same boundary may be identified in the spherical coordinates (with the center of the coordinate system, e.g., being at the center of the antenna  403 ) as a function R (θ, ϕ), that expresses the distance to the boundary of the active zone  406  in terms of the polar angle θ and the azimuthal angle ϕ. 
     The boundary of the active zone  406 , e.g., z(x, y) and/or R (θ, ϕ), as well as the boundary of the marginal zone  408 , may be used to identify optimal locations and orientations of various devices of the wireless network. In some implementations, the optimal locations may be marked or otherwise defined for the ease of using. For example, locations for devices that connect to a charging pad or a testing bench may be defined using lines, notches, indentations, magnetic contacts, docking points, or via any other suitable means. For example, under the most favorable conditions, the antennas of two devices communicating with each other may be located directly opposite to each other, with no lateral or angle tilt, as shown in  FIG. 4A . The following table illustrates a power transferred from a TX antenna to an RX antenna as a function of the vertical distance z between the centers of the respective antennas. (In this example, the TX antenna is supported by a silicon substrate.) 
                     TABLE 1                  Power transferred from an example TX        antenna for optimal TX/RX alignment                             z (mm)   S (dB)                                         1.0   −16.4           2.5   −20.5           5.0   −25.8           25.0   −40.5           50.0   −46.8                        
As follows from Table 1, for the referenced devices, the distance z=0.5 mm is close to the boundary between the active zone  406  and the marginal zone  408  whereas distance z=25 mm is well into the quiet zone  410 .
 
     As indicated by the extent of the active zone  406  in  FIG. 4A , relative disposition of the TX antenna and the RX antenna may tolerate a certain angular or lateral misalignment. For example, a user may place a receiving (or transmitting) network device in such a way that the receiving (or transmitting) antenna is not fully aligned with its counterpart in the transmitting (or receiving) device. Likewise, various pre-determined docking locations or magnetic contacts may not ensure a full alignment.  FIG. 4B  depicts schematically an angular misalignment between transmitting and receiving antennas that still allows for an efficient close-range wireless communication. The following table illustrates a power transferred from a TX antenna to an RX antenna as a function of the tilt angle θ between the axes of the respective antennas. (In this example, the TX antenna is supported by a FR4 substrate.) 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Power transferred from an example TX 
               
               
                 antenna with angular TX/RX misalignment 
               
            
           
           
               
               
               
            
               
                 z (mm) 
                 θ (deg) 
                 S (dB) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 1.0 
                 0.0 
                 −9.59 
               
               
                   
                 15.0 
                 −9.73 
               
               
                 2.5 
                 0.0 
                 −20.85 
               
               
                   
                 15.0 
                 −20.65 
               
               
                 5.0 
                 0.0 
                 −25.07 
               
               
                   
                 15.0 
                 −25.10 
               
               
                 25.0 
                 0.0 
                 −38.92 
               
               
                   
                 15.0 
                 −39.50 
               
               
                 50.0 
                 0.0 
                 −45.42 
               
               
                   
                 15.0 
                 −49.27 
               
               
                   
               
            
           
         
       
     
       FIG. 4C  depicts schematically a lateral misalignment between transmitting and receiving antennas that still allows for an efficient close-range wireless communication. The following table illustrates a power transferred from a TX antenna to an RX antenna as a function of the lateral displacement y between the axes of the respective antennas, for the vertical distance z=5 mm. (In this example, the TX antenna is supported by a FR4 Substrate.). 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Power transferred from an example TX 
               
               
                 antenna with lateral TX/RX misalignment 
               
            
           
           
               
               
               
            
               
                   
                 y (mm) 
                 S (dB) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0.0 
                 −25.1 
               
               
                   
                 1.0 
                 −24.9 
               
               
                   
                 2.5 
                 −25.3 
               
               
                   
                 5.0 
                 −28.3 
               
               
                   
                 25.0 
                 −48.3 
               
               
                   
                 50.0 
                 −58.2 
               
               
                   
                   
               
            
           
         
       
     
     Referring again to  FIG. 4A , in some instance the RX(TX) antenna assembly  404  may be associated with a device that is not intended to communicate with antenna  403  of the TX(RX) antenna assembly  402 . For example, the RX(TX) antenna assembly  404  may include a WiGig antenna. The WiGig antenna, being of a different construction than a close-range antenna, may not efficiently couple to the radiation by a close-range antenna. The following table illustrates a power transferred from a TX antenna to a WiGig RX antenna as a function of the vertical distance z between the centers of the two antennas. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Power transferred from an example TX 
               
               
                 antenna to an aligned WiGig antenna 
               
            
           
           
               
               
               
            
               
                   
                 z (mm) 
                 S (dB) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 25.0 
                 −32.5 
               
               
                   
                 30.0 
                 −34.5 
               
               
                   
                 40.0 
                 −38.5 
               
               
                   
                 50.0 
                 −42.5 
               
               
                   
                 60.0 
                 −45.0 
               
               
                   
                 75.0 
                 −47.0 
               
               
                   
                   
               
            
           
         
       
     
     Similarly, when a WiGig antenna is laterally displaced, as depicted in  FIG. 4C , power transmission to the WiGig antenna may be further reduced. The following table illustrates a power transferred from a TX antenna to a laterally displaced WiGig RX antenna for the vertical distance z=25 mm. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Power transferred from an example TX 
               
               
                 antenna to a laterally displaced WiGig antenna 
               
            
           
           
               
               
               
            
               
                   
                 y (mm) 
                 S (dB) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0.0 
                 −32.4 
               
               
                   
                 1.0 
                 −32.1 
               
               
                   
                 2.5 
                 −32.3 
               
               
                   
                 5.0 
                 −31.8 
               
               
                   
                 25.0 
                 −37.7 
               
               
                   
                 50.0 
                 −48.9 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 4D  is a schematic illustration of a wireless communication device  450  capable of supporting wireless communication links to multiple end devices, in accordance with some implementations of the present disclosure. Shown is a common substrate  411  and a common conducting layer  413 . Three antennas ( 403 ,  405 , and  407 ) are supported by the common substrate  411 . Three wireless communication links are shown with devices whose RX(TX) antenna assemblies ( 404 ,  414 , and  424 ) are also depicted. The close-range character of antennas  403 ,  405 , and  407  ensures that each communication link suffers little if at all from interference/noise caused by the other communication links. Although only three communication links are shown in  FIG. 4D  for brevity and conciseness, a wireless communication device may support any number of such (suitably spaced) links. 
       FIGS. 5A-C  are schematic depictions of possible placements of a short range antenna for integration into a wireless network device, in accordance with some implementations of the present disclosure.  FIG. 5A  depicts an example side-by-side placement  500  of a close-range antenna  502  and a wireless network processor (WNP)  506  supported by the same laminate  504 . Example placement shown in  FIG. 5A  is advantageous for its ease of fabrication but has a substantial footprint along the lateral direction.  FIG. 5B  depicts an example placement  501  of a close-range antenna  502  and a WNP  506  on opposite surfaces of the laminate  504 . Shown is a placement with the close-range antenna  502  and WNP  506  partially overlapping with each other (in the direction along the surface of the laminate  504 ), but a complete overlap (e.g., over-and-under placement) may also be used in some implementations. Example placement  501  shown in  FIG. 5B  has an advantage over placement  500  in the reduced footprint. Moreover, a small size of the optimized close-range antenna  502  makes the advantages of placement  501  even more significant. Namely, with a large-size antenna (larger than the size of WNP  506 ), a relative reduction in the footprint of the combined device may be relatively small. Yet when the size of the close-range antenna  502  is similar to the size of WNP  506 , the reduction of the footprint compared with placement  500  may be close to 50%. 
       FIG. 5C  depicts an example placement  503  in which a close-range antenna  502  is integrated with WNP  506  into a single bundle device. More specifically, the close-range antenna  502  may be manufactured as a combined module that includes laminate  504  separating the close-range antenna  502  from WNP  506  and a second laminate  508  serving as a support for WNP  506 .  FIG. 5D  depicts an example cross section of the combined bundle device of  FIG. 5C . Second laminate  508  may include a silicon layer  510  supported by a conducting layer  512 . An insulating layer  514  (e.g., a silicon dioxide layer) may be placed on top of silicon layer  510  and WNP  506  (that may have one or more layers inside) may be deposited thereupon. Conducting layer  516  and substrate  518  may support close-range antenna  502 , and a passivation layer  520  may cover close-range antenna  502 , to prevent close-range antenna  502  from oxidation and other adverse environmental conditions. Although  FIG. 5D  depicts two conducting layers, in some implementations one of the conducting layers, e.g., conducting layer  512  or conducting layer  516 , may be absent. In some implementations, both conducting layer  512  and conducting layer  516  may be absent. Instead, a conducting layer may be implemented as one of the layers of WNP  506 . 
     Example implementations of the instant disclosure are further illustrated with examples set forth below and the various features of such example implementations may be claimed alone or in combination with one another. In one example, an antenna assembly (e.g., antenna assembly  300  of  FIG. 3 ) is disclosed that includes a loop antenna (e.g., loop antenna  302 ) and a feed line (e.g., feed line  312 ) electromagnetically coupled to the loop antenna. Electromagnetic coupling may be of any suitable type: a wire contact, a capacitive coupling, an inductive coupling, or any combination thereof. The antenna assembly further includes a substrate support (e.g., substrate  304 ) in contact with the loop antenna. The substrate support includes a plurality of layers and may be configured to reduce a ratio S(1)/S(2) of a first strength S(1) of electromagnetic field generated by the loop antenna in a first region (1) to a second strength S(2) of electromagnetic field generated by the loop antenna in a second region (2). For example, the first region (1) may be in the far field domain of the antenna (e.g., at distance of 50 mm) and may be farther away from the loop antenna than the second region (2), which may be in the near field domain of the antenna (e.g., closer than 10 mm). 
     In one example, the plurality of layers of the antenna assembly includes a conducting layer (e.g., conducting layer  308 ) and a first non-conducting layer (e.g., substrate  304 ) that separates the loop antenna from the conducting layer. 
     In one example, the feed line is configured to provide, to the loop antenna, a signal having an operational frequency, e.g., frequency between 30 GHz and 100 GHz. In one specific example, operational frequency may be between 56 GHz and 72 GHz, although other signals with other operational frequencies may be provided. The first non-conducting layer may be made of (or include) a material having a thickness that is less than a wavelength of light in the material (e.g., λ), wherein the wavelength of light is determined for the operational frequency (e.g., λ=f/(nc)). 
     In one example, the plurality of layers further includes a second non-conducting layer (e.g., a layer that includes silicon dioxide) different from the first non-conducting layer (e.g., a layer that includes silicon) and disposed between the first non-conducting layer and the loop antenna. In one specific example, a thickness of the second non-conducting layer is at least ten times less than a thickness of the first non-conducting layer. 
     In one example, the loop antenna has a rectangular shape with the largest dimension (e.g., circumference of the antenna) not exceeding twice a wavelength of light in air (2λ 0 ), the wavelength of light in air determined for the operational frequency of the loop antenna (λ 0 =f/c). 
     In one example, the loop antenna has an operational bandwidth that is at least 8 GHz. In other examples, the loop antenna has an operational bandwidth that is at least 4 GHz, 2 GHz, 1 GHz, or any other suitable value. 
     In one example, disclosed is an antenna assembly that includes a loop antenna having an operational frequency between 50 GHz and 70 GHz, and further includes a substrate supporting the loop antenna, the substrate having a conducting layer and a dielectric layer (e.g., a silicon layer, an FR4 layer, or any other dielectric layer). In one specific example, the dielectric layer is disposed between the loop antenna and the conducting layer and a distance from the conducting layer to the loop antenna is less than a first wavelength of light (e.g., λ) in the dielectric layer, wherein the first wavelength of light is determined for the operational frequency (e.g., λ=f/(nc)). 
     In one example, the distance from the conducting layer to the loop antenna is less than one quarter of the first wavelength of light (λ/4). 
     In one example, conductivity of the conducting layer is at least one million Siemens per meter and conductivity of the dielectric layer is at most one hundred Siemens per meter. 
     In one example, a maximum of a circumference of the loop antenna is less than a second wavelength of light in air λ 0 , wherein the second wavelength of light is determined at the operational frequency (λ 0 =f/c). 
     In one example, disclosed is a system for wireless communications that includes a first antenna (e.g., antenna  403  of  FIG. 4A ) having an operational frequency between 50 GHz and 70 GHz and a circumference that is less than twice a wavelength of light at the operational frequency and a first substrate support for the first antenna. The first substrate support may include a first conducting screen. The system further includes a first radio communicatively coupled to the first antenna, the first radio to support a first wireless communication link (WCL) with a second radio coupled to that comprises a second antenna. For example, the second transceiver may be a transceiver associated and interacting with RX(TX) antenna assembly  404 . The first WCL may be characterized by a first strength of transmitted power that is at least −20 dB at a first location where the second antenna (e.g., antenna of the RX(TX) antenna assembly  404 ) is located. The first WCL is further characterized by a second strength of transmitted power that is at most −35 dB at a second location that is in a quiet zone (e.g., quiet zone  410  of  FIG. 4A ). In one specific example, the second location may be at a distance, from the first antenna, that is at most ten times a distance from the first antenna to the first location. 
     In one example, the distance (e.g., z or √{square root over (z 2 +x 2 )}) from the first antenna to the first location (where the second antenna is located) is less than 10 mm. 
     In one example, the system for wireless communications further includes an antenna matching network for the first antenna, the antenna matching network configured to support at least a 1 GB bandwidth of the first WCL. 
     In one example, the system for wireless communications further includes a third antenna and a second substrate support for the third antenna, the second substrate support including a second conducting layer. The system may further include a second radio communicatively coupled to the third antenna, the second radio supporting a second WCL with a fourth radio (to establish a communication link that is different from the communication link between the first antenna and the second antenna). The third antenna may be located a distance from the first antenna that is at most ten times the distance from the first antenna to the first location (e.g., distance z or √{square root over (z 2 +x 2 )}). 
     In one example, the first substrate support and the second substrate support are different portions of the same substrate layer (e.g., manufactured using the same deposition process). Likewise, the first conducting screen and the second conducting screen are different portions of the same conducting layer. 
     In one example, the first WCL and the second WCL use the same operational frequency between 50 GHz and 70 GHz. 
     In one example, as shown in  FIG. 4D , the system for wireless communications has three or more antennas (including the first antenna and the third antenna) and three or more radios (including the first radio and the second radio). In one specific example, the three or more antennas and the three or more radios are part of a wireless testing bench or a wireless charging mat. In one specific example, at least one of the three or more antennas is a Wireless Gigabit (WiGig) antenna. 
     In one example, as shown in  FIG. 5B , the system for wireless communications further includes a wireless network processor (e.g., WNP  506 ) disposed on a side of the first substrate support (e.g., laminate  504 ) that is opposite to a side in contact with the first antenna (e.g., close-range antenna  502 ). The first antenna and the wireless network processor may have at least partially overlapping footprints (in the direction along the film). 
     In one example, as shown in  FIG. 5C , the first substrate (e.g., laminate  504 ) is disposed (directly or via one or more intervening materials) on a wireless network processor (e.g., WNP  506 ). In some implementations, the first substrate may be deposited (e.g., during substrate manufacturing process) on the wireless network processor. 
     It should be understood that the above description is intended to be illustrative, and not restrictive. Many other implementation examples will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure describes specific examples, it will be recognized that the systems and methods of the present disclosure are not limited to the examples described herein, but may be practiced with modifications within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the present disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     The implementations of methods, hardware, software, firmware or code set forth above may be implemented via instructions or code stored on a machine-accessible, machine readable, computer accessible, or computer readable medium which are executable by a processing element. “Memory” includes any mechanism that provides (i.e., stores and/or transmits) information in a form readable by a machine, such as a computer or electronic system. For example, “memory” includes random-access memory (RAM), such as static RAM (SRAM) or dynamic RAM (DRAM); ROM; magnetic or optical storage medium; flash memory devices; electrical storage devices; optical storage devices; acoustical storage devices, and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer). 
     Reference throughout this specification to “one implementation” or “an implementation” means that a particular feature, structure, or characteristic described in connection with the implementation is included in at least one implementation of the disclosure. Thus, the appearances of the phrases “in one implementation” or “in an implementation” in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations. 
     In the foregoing specification, a detailed description has been given with reference to specific exemplary implementations. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. Furthermore, the foregoing use of implementation, implementation, and/or other exemplarily language does not necessarily refer to the same implementation or the same example, but may refer to different and distinct implementations, as well as potentially the same implementation. 
     The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example’ or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Moreover, use of the term “an implementation” or “one implementation” or “an implementation” or “one implementation” throughout is not intended to mean the same implementation or implementation unless described as such. Also, the terms “first,” “second,” “third,” “fourth,” etc. as used herein are meant as labels to distinguish among different elements and may not necessarily have an ordinal meaning according to their numerical designation.