Coupler and related method, module and device

Abstract

Embodiments of the present disclosure relate to a coupler, antenna module and electronic device. The coupler comprises a first substrate layer and a second substrate layer located below the first substrate layer. The coupler also comprises a first coupling line located on an upper surface of the first substrate layer and a second coupling line located on a lower surface of the second substrate layer. The coupler further comprises a first ground layer located between a lower surface of the first substrate layer and an upper surface of the second substrate layer, a plurality of hole groups being formed in the first ground layer and being geometrically designed such that an electromagnetic field of the first coupling line is coupled to the second coupling line through the plurality of hole groups. In this way, PCB space and size may be saved, RF performance may be improved, and PCB cost may be reduced.

Description

FIELD

[0001] Embodiments of the present disclosure generally relate to the field oftelecommunication and in particular, to a coupler, an antenna module, an electronic deviceand a method for fabricating the coupler.BACKGROUND

[0002] A coupler is a core element of a calibration network for a multi-input multi-output(MIMO) antenna array. A conventional coupler consists of two coupling lines which areclosed located in a plane. When a radio frequency (RF) signal is transmitted on one of thetwo coupling lines, an electro-magnetic field is coupled to the other of the two couplinglines, resulting in coupling and isolation characteristics.

[0003] Although the conventional coupler is used widely in an antenna calibrationnetwork, some problems exist all the time such as a waste of printed circuit board (PCB)space due to a planar structure, deterioration of a RF performance due to a via design, fixedoutput characteristics, and so on. Thus, an improved coupler needs to be designed toovercome at least part of such problems.SUMMARY

[0004] In general, example embodiments of the present disclosure provide a coupler, anantenna module, an electronic device and a method for fabricating a coupler.

[0005] In a first aspect, there is provided a coupler. The coupler comprises: a firstsubstrate layer; a second substrate layer located below the first substrate layer; a firstcoupling line located on an upper surface of the first substrate layer; a second coupling linelocated on a lower surface of the second substrate layer; and a first ground layer locatedbetween a lower surface of the first substrate layer and an upper surface of the secondsubstrate layer, a plurality of hole groups being formed in the first ground layer and beinggeometrically designed such that an electro-magnetic field of the first coupling line iscoupled to the second coupling line through the plurality of hole groups.

[0006] In a second aspect, there is provided an antenna module. The antenna modulecomprises a plurality of couplers according to the first aspect.

[0007] In a third aspect, there is provided an electronic device. The electronic devicecomprises an antenna module according to the second aspect.

[0008] In a fourth aspect, there is also provided an electronic device. The electronicdevice comprises a coupler according to the first aspect.

[0009] In a fifth aspect, there is provided a method for fabricating a coupler. The methodcomprises: forming a first coupling line on an upper surface of a first substrate layer;forming a second coupling line on a lower surface of a second substrate layer, the secondsubstrate layer being located below the first substrate layer such that an upper surface of thesecond substrate layer faces a lower surface of the first substrate layer; and forming a firstground layer such that the first ground layer is located between the lower surface of the firstsubstrate layer and the upper surface of the second substrate layer, and such that a pluralityof hole groups are formed in the first ground layer and are geometrically designed such thatan electro-magnetic field of the first coupling line is coupled to the second coupling linethrough the plurality of hole groups.

[0010] It is to be understood that the summary section is not intended to identify key oressential features of embodiments of the present disclosure, nor is it intended to be used tolimit the scope of the present disclosure. Other features of the present disclosure willbecome easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Some example embodiments will now be described with reference to theaccompanying drawings, where:

[0012] Fig. 1 illustrates a diagram of an example MIMO antenna module in whichembodiments of the present disclosure may be implemented;

[0013] Fig. 2 illustrates a diagram of an operating principle of a coupler according to aconventional solution;

[0014] Fig. 3 illustrates a diagram of a structure of a coupler according to a conventionalsolution;

[0015] Fig. 4 illustrates a diagram of an example structure of a coupler according to someexample embodiments of the present disclosure;

[0016] Fig. 5 illustrates a diagram of an example of a two-PCB structure of a coupler according to some example embodiments of the present disclosure;

[0017] Fig. 6A illustrates a diagram of another example structure of a coupler according tosome example embodiments of the present disclosure;

[0018] Fig. 6B illustrates a diagram of another example of a two-PCB structure of acoupler according to some example embodiments of the present disclosure;

[0019] Fig. 7 illustrates a diagram of comparison between two PCBs of a coupleraccording to some example embodiments of the present disclosure;

[0020] Fig. 8A illustrates a diagram of an output signal amplitude of Port 3 of a coupleraccording to some example embodiments of the present disclosure;

[0021] Fig. 8B illustrates a diagram of an output signal amplitude of Port 4 of a coupleraccording to some example embodiments of the present disclosure;

[0022] Fig. 9A illustrates a diagram of coupling lines of a coupler according to someexample embodiments of the present disclosure;

[0023] Fig. 9B illustrates another diagram of coupling lines of a coupler according tosome example embodiments of the present disclosure;

[0024] Fig. 10 illustrates a diagram of example shapes of a hole group of a coupleraccording to some example embodiments of the present disclosure;

[0025] Fig. 11 illustrates a diagram of example constructions of a hole group of a coupleraccording to some example embodiments of the present disclosure;

[0026] Fig. 12A illustrates an example basic simulation model for optimization of acoupler according to some example embodiments of the present disclosure;

[0027] Fig. 12B illustrates a top view of the basic simulation model of FIG. 12A with alength L_win of a hole group;

[0028] Fig. 12C illustrates a graph of a coupling degree varied with L_win according tosome example embodiments of the present disclosure;

[0029] Fig. 13 illustrates a diagram of an antenna module according to some exampleembodiments of the present disclosure;

[0030] Fig. 14 illustrates a diagram of an electronic device according to some exampleembodiments of the present disclosure; and

[0031] Fig. 15 illustrates a flowchart of an example method of fabricating a coupler according to some example embodiments of the present disclosure.

[0032] Throughout the drawings, the same or similar reference numerals represent thesame or similar element.DETAILED DESCRIPTION

[0033] Principle of the present disclosure will now be described with reference to someexample embodiments. It is to be understood that these embodiments are described onlyfor the purpose of illustration and to help those skilled in the art to understand andimplement the present disclosure, without suggesting any limitation as to the scope of thedisclosure. The disclosure described herein can be implemented in various manners otherthan the ones described below.

[0034] In the following description and claims, unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonly understood by one ofordinary skills in the art to which this disclosure belongs.

[0035] References in the present disclosure to "one embodiment," "an embodiment," "anexample embodiment," and the like indicate that the embodiment described may include aparticular feature, structure, or characteristic, but it is not necessary that every embodimentincludes the particular feature, structure, or characteristic. Moreover, such phrases are notnecessarily referring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with an example embodiment, it issubmitted that it is within the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodiments whether or not explicitlydescribed.

[0036] It shall be understood that although the terms "first" and "second" etc. may beused herein to describe various elements, these elements should not be limited by theseterms. These terms are only used to distinguish one element from another. For example,a first element could be termed a second element, and similarly, a second element could betermed a first element, without departing from the scope of example embodiments. Asused herein, the term "and / or" includes any and all combinations of one or more of thelisted terms.

[0037] The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be further understood that theterms "comprises", "comprising", "has", "having", "includes" and / or "including", whenused herein, specify the presence of stated features, elements, and / or components etc., butdo not preclude the presence or addition of one or more other features, elements,components and / or combinations thereof.

[0038] As used in this application, the term "circuitry" may refer to one or more or all ofthe following:(a) hardware-only circuit implementations (such as implementations in only analogand / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) withsoftware / firmware and(ii) any portions of hardware processor(s) with software (including digitalsignal processor(s)), software, and memory(ies) that work together to cause anapparatus, such as a mobile device or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portionof a microprocessor(s), that requires software (e.g., firmware) for operation, but thesoftware may not be present when it is not needed for operation.

[0039] This definition of circuitry applies to all uses of this term in this application,including in any claims. As a further example, as used in this application, the termcircuitry also covers an implementation of merely a hardware circuit or processor (ormultiple processors) or portion of a hardware circuit or processor and its (or their)accompanying software and / or firmware. The term circuitry also covers, for example andif applicable to the particular claim element, a baseband integrated circuit or processorintegrated circuit for a mobile device or a similar integrated circuit in server, a cellularnetwork device, or other computing or network device.

[0040] As used herein, the term "communication network" refers to a network followingany suitable communication standards, such as fifth generation (5G) systems, Long TermEvolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access(WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a networkdevice in the communication network may be performed according to any suitablegeneration communication protocols, including, but not limited to, the first generation (1G),the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation(4G), 4.5G, the future fifth generation (5G) new radio (NR) communication protocols,and / or any other protocols either currently known or to be developed in the future. Inaddition, the term "communication network" may also refer to non-cellularcommunications network. The communications may include direct device to devicecommunication, e.g. (a) base station node to base station node, or (b) mobile device tomobile device, without any interaction of a mobile device (in case a) or a base station (incase b). Embodiments of the present disclosure may be applied in various communicationsystems. Given the rapid development in communications, there will of course also befuture type communication technologies and systems with which the present disclosuremay be embodied. It should not be seen as limiting the scope of the present disclosure toonly the aforementioned system.

[0041] As used herein, the term "communication device" or "electronic device" refers to anetwork device or a terminal device in a communication network. The term "networkdevice" refers to a node in the communication network via which a terminal deviceaccesses the network and receives services therefrom. The network device may refer to abase station (BS) or an access point (AP), for example, a node B (NodeB or NB), anevolved NodeB (eNodeB or eNB), a NR Next Generation NodeB (gNB), a Remote RadioUnit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power nodesuch as a femto, a pico, and so forth, depending on the applied terminology and technology.An RAN split architecture comprises a gNB-CU (Centralized unit, hosting RRC, SDAP andPDCP) controlling a plurality of gNB-DUs (Distributed unit, hosting RLC, MAC andPHY).

[0042] The term "terminal device" refers to any end device that may be capable ofwireless communication. By way of example rather than limitation, a terminal device mayalso be referred to as a communication device, user equipment (UE), a mobile device, aSubscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an AccessTerminal (AT). The terminal device may include, but not limited to, a mobile phone, acellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, atablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminaldevices, music storage and playback appliances, vehicle-mounted wireless terminal devices,wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mountedequipment (LME), USB dongles, smart devices, wireless customer-premises equipment(CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounteddisplay (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery),an industrial device and applications (e.g., a robot and / or other wireless devices operatingin an industrial and / or an automated processing chain contexts), a consumer electronicsdevice, a device operating on commercial and / or industrial wireless networks, and the like.Although functionalities described herein can be performed, in various exampleembodiments, in a fixed and / or a wireless network node may, in other exampleembodiments, functionalities may be implemented in a user equipment apparatus (such as acell phone or tablet computer or laptop computer or desktop computer or mobile IOTdevice or fixed IOT device). This user equipment apparatus can, for example, befurnished with corresponding capabilities as described in connection with the fixed and / orthe wireless network node(s), as appropriate. The user equipment apparatus may be theuser equipment and / or or a control device, such as a chipset or processor, configured tocontrol the user equipment when installed therein. Examples of such functionalitiesinclude the bootstrapping server function and / or the home subscriber server, which may beimplemented in the user equipment apparatus by providing the user equipment apparatuswith software configured to cause the user equipment apparatus to perform from the pointof view of these functions / nodes.

[0043] The term "mobile device" refers to a device capable of being moved from point Ato point B by any means, for example and not limited to: by hand, by carrying, by vehicle(driving, flying, sailing / floating in a liquid, etc), by being worn by a user of the mobiledevice.

[0044] In addition, the term "communication device" or "electronic device" may alsorefer to fixed or stationary electronic communication devices, e.g. base station nodes, whichare devices which are fixed in place and do not move.

[0045] Due to better beam forming, beam pointing and hot spot coverage performance, alarge-scale active antenna array or massive MIMO antenna array will replace aconventional passive antenna array to become a basic form of 5G cellular mobilecommunication base station system. A calibration network may be detected and backward corrected the phase and amplitude of signals being transmitted or received from the antennaarray, and then beam-forming performance of the active antenna array may be controlled.Thus, a calibration network becomes a key device in the active antenna array, and a coupleris a core element of such calibration network.

[0046] As mentioned above, some problems in a conventional coupler exist all the timesuch as a waste of PCB space due to a planar structure, deterioration of a RF performancedue to a via design, fixed output characteristics, and so on.

[0047] In order to at least in part solve above and other potential problems, exampleembodiments of the present disclosure provide an improved coupler. The improvedcoupler comprises two coupling lines. The two coupling lines are located on top of eachother and a stack is sandwiched between the two coupling lines. The stack comprises twosubstrate layers and a ground layer between the two substrate layers. The ground layer isformed with a plurality of hole groups and the plurality of hole groups are partiallyoverlapped with the two coupling lines. In this way, a coupler is achieved in a verticalspace by forming two coupling lines at different layers without using a metal via. Thus,PCB space and size may be saved, RF performance may be improved, and PCB cost maybe reduced.

[0048] It is to be understood that a coupler according to embodiments of the presentdisclosure may be applied to a directional coupler or a partially directional coupler or anyother suitable types of couplers.

[0049] Principle and implementations of the present disclosure will be described in detailbelow with reference to Figs. 1 to 13.EXAMPLE OF APPLICATION ENVIRONMENT

[0050] Fig. 1 illustrates a diagram of an example MIMO antenna module 100 in whichembodiments of the present disclosure may be implemented. As shown in Fig. 1, theantenna module 100 may comprise an antenna array 110, a calibration network 120 for theantenna array 110 and a feeding network for the antenna array (not shown). The antennaarray 110 may comprise a plurality of antenna elements (AEs) 111. The calibrationnetwork 120 may comprise a plurality of couplers 121. Each coupler 121 is configuredfor each AE 111 or sub-array and causes a part of signals transmitted to or received fromthe AEs 111 to be transmitted to the calibration network 120. In other words, the pluralityof couplers 121 may collect calibration signals for the calibration network 120. The calibration network 120 may comprise a plurality of power dividers 122 such as Wilkinsonpower dividers. The plurality of power dividers 122 may be configured to combine allthose separated signals together to a calibration port 123.

[0051] It should be noted that the number of the antenna array, AEs, couplers, powerdividers and calibration network in Fig. 1 is given for the purpose of illustration withoutsuggesting any limitations to the present disclosure. The antenna module 100 may includeany suitable number of the antenna array, AEs, couplers, power dividers and calibrationnetwork adapted for implementing implementations of the present disclosure. Further, theantenna module 100 may comprise additional components not shown and / or may omitsome components as shown, and the scope of the present disclosure is not limited in thisregard. It should also be noted that embodiments of the present disclosure may also beapplied to any other suitable high-frequency applications, and are not limited to the aboveantenna application.OUTLINE OF CONVENTIONAL SOLUTION

[0052] Fig. 2 illustrates a diagram 200 of an operating principle of a coupler according toa conventional solution. As shown in Fig. 2, the coupler comprises two coupling lines 210and 220. The two coupling lines 210 and 220 are closely located with a distance D.When a RF signal is transmitted on one of the coupling lines (for example, from Port 1 toPort 2 of the coupling line 210), an electro-magnetic field is coupled to another one (forexample, the coupling line 220), resulting in coupling and isolation characteristics.

[0053] For example, Port 1 of the coupling line 210 may be coupled to an antenna arrayvia a feeding network for the antenna array, and Port 2 of the coupling line 210 may becoupled to a transceiver processing module. Assuming that Port 3 of the coupling line 220is a coupling port and Port 4 of the coupling line 220 is an isolation port. Port 3 may becoupled to a calibration network for the antenna array. Port 3 may collect signalstransmitted from Port 1 to Port 2 and transmit the collected signals to the calibrationnetwork for antenna calibration. Port 4 of the coupling line 220 may be coupled to animpedance element.

[0054] The distance D between the two coupling lines 210 and 220 determines amagnitude of coupling of the coupler, and a length of parallel portions of the two couplinglines 210 and 220 determines an operating frequency of the coupler. By changing shapesof the two coupling lines, good isolation and return loss performance may be obtained.

[0055] Fig. 3 illustrates a diagram 300 of a structure of a coupler according to aconventional solution. As shown in Fig. 3, one coupling line (an antenna feeding line) arebroken into three parts 311, 312 and 313. The parts 311 and 312 are located on the topside of a dielectric substrate 301 and the part 313 is located on the bottom side of adielectric substrate 302 or on the tope side of a dielectric substrate 303. Another couplingline 330 is located in the same plane as the part 313. Each of the parts 311 and 312 isconnected to the part 313 by a metal via 350 so as to be coupled with the coupling line 330.A ground plane 320 is located between dielectric substrates 301 and 302 and used to isolatethe two coupling lines. Besides, a dielectric substrate 303 and a ground layer 340 on thebottom side of the dielectric substrate 303 are used to protect the coupler to get better RFperformance.

[0056] It can be seen that, the conventional coupler is a planar structure, and lots of planarsize will be used. Thus, a PCB space is wasted. Further, one of the coupling lines (forexample, the parts 311, 312 and 313) is a part of an antenna feeding line. As the antennafeeding line usually uses a good PCB material to get a better antenna performance, PCBcost is increased. Furthermore, when the antenna feeding line goes to a different layer tocouple with another coupling line, vias are used. However, the vias may deteriorate theRF performance. Moreover, output characteristics of the conventional coupler are fixed.In other words, once a type of the coupler is selected, no matter how to design, the couplingport, isolation port and output phase are fixed and cannot be changed. In addition, the twocoupling lines in the conventional coupler should have an equal length, and must be nearlyto a λ / 4, where λ denotes a wavelength at a center frequency of an operating bandwidth ofthe coupler. Thus, such design is not flexible.EXAMPLE IMPLEMENTATION OF IMPROVED COUPLER

[0057] In view of this, embodiments of the present disclosure provide an improvedcoupler. The details will be described below with reference to Figs. 4 to 12C.1. BASIC STRUCTURE

[0058] Fig. 4 illustrates a diagram of an example structure of a coupler 400 according tosome example embodiments of the present disclosure. As shown in Fig. 4, the coupler400 comprises a substrate layer 411 (for convenience, also referred to as a first substratelayer herein) and a substrate layer 412 (for convenience, also referred to as a secondsubstrate layer herein) located below the substrate layer 411. The coupler 400 also comprises a coupling line 421 (for convenience, also referred to as a first coupling lineherein) located on an upper surface of the substrate layer 411 and a coupling line 422 (forconvenience, also referred to as a second coupling line herein) located on a lower surface ofthe substrate layer 412.

[0059] Further, the coupler 400 comprises a ground layer 423 (for convenience, alsoreferred to as a first ground layer herein) located between a lower surface of the substratelayer 411 and an upper surface of the substrate layer 412. A plurality of hole groups (forillustration, two hole groups 431 and 432 are shown here) are formed in the ground layer423 and are geometrically designed such that an electro-magnetic field of the coupling line421 is coupled to the coupling line 422 through the plurality of hole groups.

[0060] In some embodiments, the hole structures 431 and 432 may be located atoverlapped portions of the coupling lines 421 and 422. That is, as shown in Fig. 4,projections 441 and 442 of the hole groups 431 and 432 on a plane in which the couplingline 421 is located are partially overlapped with the coupling line 421, and projections 443and 444 of the hole groups 431 and 432 on a plane in which the coupling line 422 is locatedwill be partially overlapped with the coupling line 422. It is to be understood that theprojections 441, 442, 443 and 444 are shown merely for illustration, and are not actuallypresent elements.

[0061] In some embodiments, the plurality of hole groups may be arranged nonlinearly.Of course, the plurality of hole groups may be arranged linearly. The present disclosuredoes not limit this aspect. In some embodiments, the plurality of hole groups maycomprise two groups of holes, and each group may comprise one or more holes. The oneor more holes may be arranged in any suitable forms and may adopt any suitable shapes.The present disclosure also does not limit this aspect.

[0062] In some embodiments, each of the substrate layers 411 and 412 may be amulti-layer stack. In some embodiments, the substrate layers 411 and 412 may havedifferent thicknesses. In some embodiments, the substrate layers 411 and 412 may havedifferent relative dielectric constants.

[0063] In some embodiments, the coupler 400 may be implemented by one PCB. Inother words, the substrate layers 411 and 412, the coupling lines 421 and 422 and theground layer 423 may be formed in the same PCB, for example, in a multi-layer PCB.

[0064] In some alternative embodiments, the coupler 400 may be implemented by two PCBs. For clarity, the detailed description will be given with reference to Fig. 5. Fig. 5illustrates a diagram of an example of a two-PCB structure of a coupler 500 according tosome example embodiments of the present disclosure. For convenience, Fig. 5 will bedescribed in connection with the example of Fig. 4.

[0065] As shown in Fig. 5, the coupler 500 comprises two PCBs 501 and 502. In thisexample, the PCB 501 may comprise the substrate layer 411, the coupling line 421 and theground layer 423 in Fig. 4. In some embodiments, the ground layer 423 may be formedon the lower surface of the substrate layer 411. The PCB 502 may comprise the substratelayer 412 and the coupling line 422 in Fig. 4.

[0066] In a modified example (not shown) for Fig. 5, the ground layer 423 may be formedin PCB 502 instead of PCB 501. In this case, the ground layer 423 may be formed on theupper surface of the substrate layer 412.

[0067] With the two-PCB structure, the substrate layers 411 and 412 may be formed indifferent PCBs and may be fabricated by different materials so as to reduce the PCB cost.For example, in an antenna application, the PCB 501 may be fabricated by a low-loss andexpensive material to ensure good RF performance, and the PCB 502 may be fabricated bya cheaper material. Thus, the PCB cost is reduced significantly.2 . MODIFIED STRUCTURE

[0068] Fig. 6A illustrates a diagram of another example structure of a coupler 600Aaccording to some example embodiments of the present disclosure. For convenience, Fig.6A will be described in connection with the example of Fig. 4.

[0069] As shown in Fig. 6A, in addition to the substrate layers 411 and 412, the couplinglines 421 and 422 and the ground layer 423, the coupler 600A comprises a substrate layer613 (also referred to as a third substrate layer herein) located on the substrate layer 411 anda ground layer 624 (also referred to as a second ground layer herein) located on thesubstrate layer 613. In this way, the coupling line 421 may be well isolated.

[0070] As shown in Fig. 6A, the coupler 600A also comprises a substrate layer 614 (alsoreferred to as a fourth substrate layer herein) located below the substrate layer 412 and aground layer 625 (also referred to as a third ground layer herein) located below thesubstrate layer 614. In this way, the coupling line 422 may also be well isolated.

[0071] In some embodiments, each of the substrate layers 613 and 614 may be a multi-layer stack. In some embodiments, the substrate layers 411, 412, 613 and 614 mayhave different thicknesses. In some embodiments, the substrate layers 411, 412, 613 and614 may have different relative dielectric constants.

[0072] In a modified example (not shown) for Fig. 6A, in addition to the substrate layers411 and 412, the coupling lines 421 and 422 and the ground layer 423, the coupler 600Amay only comprise the substrate layer 613 and the ground layer 624. In another modifiedexample (not shown) for Fig. 6A, in addition to the substrate layers 411 and 412, thecoupling lines 421 and 422 and the ground layer 423, the coupler 600A may also onlycomprise the substrate layer 614 and the ground layer 625.

[0073] In some embodiments, the coupler 600A may be implemented by one PCB. Insome alternative embodiments, the coupler 600A may be implemented by two PCBs. Forclarity, the detailed description will be given with reference to Fig. 6B. Fig. 6B illustratesa diagram of another example of a two-PCB structure of a coupler 600B according to someexample embodiments of the present disclosure. For convenience, Fig. 6B will bedescribed in connection with the example of Fig. 6A.

[0074] As shown in Fig. 6B, the coupler 600B comprises two PCBs 601 and 602. In thisexample, the PCB 601 may comprise the substrate layer 613, the ground layer 624, thesubstrate layer 411, the coupling line 421 and the ground layer 423 in Fig. 6A. The PCB602 may comprise the substrate layer 412, the coupling line 422, the substrate layer 614and the ground layer 625 in Fig. 6A.

[0075] In a modified example (not shown) for Fig. 6B, the ground layer 423 may beformed in PCB 602 instead of PCB 601. In a modified example (not shown) for Fig. 6B,the PCB 601 may only comprise the substrate layer 411, the coupling line 421 and theground layer 423 and not comprise the substrate layer 613 and the ground layer 624 in Fig.6A. In another modified example (not shown) for Fig. 6B, the PCB 602 may onlycomprise the substrate layer 412 and the coupling line 422 and not comprise the substratelayer 614 and the ground layer 625.

[0076] For the two-PCB structure, the two PCBs may be fabricated in different sizes.Fig. 7 illustrates a diagram 700 of comparison between two PCBs of a coupler according tosome example embodiments of the present disclosure. For convenience, Fig. 7 will bedescribed in connection with the example of Figs. 5 and 6B.

[0077] As shown in Fig. 7, PCB 710 has a larger size and PCB 720 has a smaller size.For example, the PCB 710 may implement the PCB 501 in Fig. 5, and the PCB 720 mayimplement the PCB 502 in Fig. 5. As another example, the PCB 710 may implement thePCB 601 in Fig. 6B, and the PCB 720 may implement the PCB 602 in Fig. 6B. As twoPCBs may be fabricated in different sizes, PCB area is saved.3 . EXAMPLE ANALYSIS OF OUTPUT CHARACTERISTICS

[0078] With reference to Fig. 4, assuming that a total length of the coupling line 421 is L1between the two hole groups 431 and 432, and a phase corresponding to an operatingfrequency is θ1, where the unit of θ1 is degree. Also, assuming that a total length of thecoupling line 422 is L2 between the two hole groups 431 and 432, and a phasecorresponding to an operating frequency is θ2, where the unit of θ2 is degree.

[0079] Assuming that a RF signal is transmitted from Port 1 to Port 2 of the coupling line421. In this case, output characteristics of Port 4 and Port 3 of the coupling line 422 maybe represented in equations (1) and (2).Port 4 = Ae-j0 + Ae-jθ1-jθ2 = A + A*cos(θ1+θ2) + j*A*sin(θ1+θ2) (1)Port 3 = Ae-jθ2 + Ae-jθ1 (2)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency, A denotes a coupling amplitude, and j denotesmathematic symbol of complex number.

[0080] It can be seen from equations (1) and (2) that outputs of Port 3 and Port 4 of thecoupling line 422 may be different based on different lengths of the coupling lines 421 and422.

[0081] If Port 4 of the coupling line 422 is an isolation port, equation (3) should be met:Port 4 = Ae-j0 + Ae-jθ1-jθ2 = A + A*cos(θ1+θ2) + j*A*sin(θ1+θ2) = 0 (3)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency, A denotes a coupling amplitude, and j denotesmathematic symbol of complex number.

[0082] So, equation (4) may be obtained as below.θ1 + θ2 = 180 * (2N+1) (4)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency and N denotes an integer.

[0083] When taking equation (4) into equation (2), output characteristics of Port 3 may berepresented in equation (5):Port 3 = Ae-jθ2 + Ae-jθ1= Ae-jθ1 + Ae-j(180-θ1) = 2A*j*sin(θ1) (5)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency, A denotes a coupling amplitude, and j denotesmathematic symbol of complex number.

[0084] Fig. 8A illustrates a diagram 800A of an output signal amplitude of Port 3 of acoupler according to some example embodiments of the present disclosure. Fig. 8Ashows a relationship between θ1 or 180-θ2 and an output normalized amplitude (outputamplitude / 2A). It can be seen from Fig. 8A that the relationship exhibits a typical sinewave. No matter what value of θ1 is selected, Port 3 has a signal output.

[0085] It can be seen from equation (5) and Fig. 8A that Port 3 is a coupling port with asignal output. Especially when θ1 and θ2 meet below equation (6), Port 3 has a maximumamplitude output.θ1 = 180 - θ2 = 90*(2N+1) (6)where θ1 denotes a phase of the coupling line 421 corresponding to an operating frequency,θ2 denotes a phase of the coupling line 422 corresponding to an operating frequency, and Ndenotes an integer.

[0086] It is found that equation (6) is another form of L1 = L2 = λ / 4 when N=0 (which isthe typical value used in the industry), where λ denotes a wavelength at a center frequencyof an operating bandwidth of the coupler. Then it is concluded that whenθ1+θ2=180*(2N+1), Port 4 acts as an isolation port with no signal output, while Port 3 actsas a coupling port. When θ1 = 180-θ2 = 90*(2N+1), Port 3 can output a maximum signalamplitude. In this way, the coupling direction has the same direction with transmitting.So, the coupler operates as a forward coupler.

[0087] To achieve a given coupling value, θ1 may be freely selected, and then θ2 may beobtained by the above equation (4). It is possible even if θ1 is not equal to θ2 and they are not 90 degrees. So far, the phases of the coupling lines 421 and 422 may be obtained.The phases may be changed into physical lengths of transmission lines based on equation(7). The distance between the two hole groups 431 and 432 is the same as the lengthof coupling line 422.[Equation] (7)where c denotes a speed of light in vacuum; freq denotes an operating frequency of thecoupler; er denotes an equivalent dielectric constant of dielectric materials on whichcoupling lines 421 and 422 are formed.

[0088] If Port 3 is needed to be used as an isolation port, then the below equation (8)should be met:Port 3 = Ae-jθ2 + Ae-jθ1=2A*cos(θ2 / 2-θ1 / 2) * (cos(θ1 / 2+θ2 / 2) + j * sin(θ1 / 2+θ2 / 2)) = 0 (8)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency, A denotes a coupling amplitude, and j denotesmathematic symbol of complex number.

[0089] It also means that equation (9) is met:cos(θ1 / 2-θ2 / 2) = 0 (9)where θ1 denotes a phase of the coupling line 421 corresponding to an operating frequency,θ2 denotes a phase of the coupling line 422 corresponding to an operating frequency.

[0090] So, equation (10) is obtained:θ1 - θ2 = 180*(2N+1) (10)where θ1 denotes a phase of the coupling line 421 corresponding to an operating frequency,θ2 denotes a phase of the coupling line 422 corresponding to an operating frequency, and Ndenotes an integer.

[0091] It can be seen from equation (10) that Port 3 has two signals with equal amplitudesand opposite phases. Thus the two signals cancel out with each other, which leading to Port3 being an isolation port without signal output.

[0092] When taking equation (10) into equation (1), output characteristics of Port 4 isobtained by equation (11):Port 4 = Ae-j0 + Ae-jθ1-jθ2 = A + A*cos(θ1+θ2) + j*A*sin(θ1+θ2) = A - A*cos(2*θ2) -j*A*sin(2*θ2) (11)where θ1 denotes an output phase of the coupling line 421 (Port 2) corresponding to anoperating frequency, θ2 denotes an output phase of the coupling line 422 (Port 3)corresponding to an operating frequency, A denotes a coupling amplitude, and j denotesmathematic symbol of complex number.

[0093] Fig. 8B illustrates a diagram 800B of an output signal amplitude of Port 4 of acoupler according to some example embodiments of the present disclosure. Fig. 8Bshows a relationship between θ2 or θ1-180 and an output normalized amplitude (outputamplitude / 2A). It can be seen from Fig. 8B that the relationship exhibits a typical sinewave. No matter what value of θ2 is selected, Port 4 has a signal output.

[0094] It can be seen from equation (11) and Fig. 8B that Port 4 is a coupling port withsignal output. Especially when θ1 and θ2 meet below equation (12), Port 4 has amaximum amplitude output.θ2 = θ1 -180 = 90*(2N+1) or θ1 + θ2 =360*N (12)where θ1 denotes a phase of the coupling line 421 corresponding to an operating frequency,θ2 denotes a phase of the coupling line 422 corresponding to an operating frequency, and Ndenotes an integer.

[0095] It can be seen from the above that when θ1 - θ2 = 180*(2N+1), Port 3 acts as anisolation port with no signal output while Port 4 acts as a coupling port. When θ2 =θ1-180 = 90*(2N+1), Port 4 may output a maximum signal amplitude. In this way, thecoupling direction has an opposite direction with transmitting. So, the coupler operates asa backward coupler.

[0096] To achieve a given coupling value by using this backward coupler, θ1 may befreely selected, and then θ2 may be obtained by equation (10). It is possible when θ1 isnot equal to θ2 and they are not 90 degrees. Then physical lengths of the coupling lines421 and 422 also may be obtained based on equation (7). A distance of the two holegroups 431 and 432 is the same as a length of the coupling line 422.

[0097] Based on above analysis, it can be seen that the output characteristics may bevariable by changing the length of the coupling lines 421 and 422. When θ1 + θ2 = 180 *(2N+1), the coupler is convenient to be used as a forward coupler, where Port 4 is an isolation port and Port 3 is a coupling port. When θ1 - θ2 = 180*(2N+1), the coupler maybe used as a backward coupler, where Port 3 is an isolation port and Port 4 is a couplingport. In this case, the right length or phase may be selected to meet the actualrequirements in layout.

[0098] Besides, as the two coupling lines are unnecessary to keep parallel relationship orspacing the 1 / 4 wave-length during the whole coupling process, so the design is moreflexible. Similarly, the planar size is also saved because the coupling lines exist in thevertical direction. Of course, when different θ1 and θ2 are used, output characteristics ofPort 3 and Port 4 may be checked by simulation or calculation by using equations (1) and(2).

[0099] The coupling amplitude may be changed by adjusting the size of the hole groups431 and 432, including the thickness of the substrate layer 411. The size of hole groups isbigger, the coupling amplitude will be bigger accordingly. However, if it is expected toachieve a weak coupling, but the thickness of the substrate layer 412 is thin, even the sizeof coupling holes is little enough, the coupling may still be bigger. Besides, a hole groupwith a little size is also not easy to be fabricated. Based on above analysis of couplingprinciple, the coupling amplitude will be decreased by keeping the port outputcharacteristics unchanged while adjusting the length or phase of two coupling lines slightly.For example, if the forward coupler is used to achieve the coupling amplitude of A (half oftotal 2A), we can select θ1=30, and θ2=150 degrees based on equation (5). By thismethod, the hole groups 431 and 432 may be designed with a bigger size, but a weakcoupling is still obtained.4. EXAMPLE IMPLEMENTATION OF COUPLING LINES

[00100] According to embodiments of the present disclosure, the coupling lines 421 and422 may be arranged freely into any routing shapes. In some embodiments, the couplinglines 421 and 422 may be not parallel to each other. Of course, the coupling lines 421 and422 may also be parallel with each other. In some embodiments, the coupling lines 421and 422 may have different lengths. Of course, the coupling lines 421 and 422 may alsohave the same length. In some embodiments, the coupling lines 421 and 422 may havedifferent routing shapes. Of course, the coupling lines 421 and 422 may also have thesame routing shape.

[00101] Fig. 9A illustrates a diagram of coupling lines of a coupler 900A according to some example embodiments of the present disclosure. As shown in Fig. 9A, one couplingline 901 may be formed in a staggered shape, and another one coupling line 902 may beformed in a linear shape.

[00102] Fig. 9B illustrates another diagram of coupling lines of a coupler 900B accordingto some example embodiments of the present disclosure. As shown in Fig. 9B, onecoupling line 911 may be formed in a staggered shape, and another one coupling line 912may be formed in a different staggered shape.

[00103] Of course, examples of Figs. 9A and 9B are merely for illustration, and the presentdisclosure is not limited to these examples.

[00104] In some embodiments, the coupling lines 421 and 422 may be comprised ofmicro-strip lines. Of course, any other suitable forms are also feasible. In someembodiments, an equivalent impedance of each of the coupling lines 421 and 422 may beabout 50ohm. In some embodiments, the equivalent impedance may also be a valueranged from 20ohm to 100ohm. Of course, any other suitable values are also feasible.5. EXAMPLE IMPLEMENTATION OF HOLE GROUPS

[00105] According to embodiments of the present disclosure, by increasing a width (W) orlength (L) of the hole groups 431 and 432 to make the hole groups bigger, the coupling maybe stronger. In some embodiments, the coupling amplitude will be changed by changingthe value of W compared to L.

[00106] In some embodiments, the W and L may be less than 4 times of coupling linewidth. In this way, only weak coupling may be obtained, for example, less than -10dB.It's hard to achieve stronger coupling by this structure, like bigger than -10dB. But it isbetter used in antenna calibration network application, which only requires -20dB to -40dBcoupling. Of course, W and L may also be any other values or shapes, as long as the shapesof the two coupling lines needs to be modified to get a better RL. In this way, the designof the coupler is very flexible.

[00107] According to embodiments of the present disclosure, the hole groups 431 and 432may have any suitable shapes of holes. Fig. 10 illustrates a diagram 1000 of example holeshapes of a hole group of a coupler according to some example embodiments of the presentdisclosure. As shown in Fig. 10, a hole in the hole group may have an arc shape as shownby 1001. In some embodiments, a hole in the hole group may have a rectangle shape asshown by 1002. In some embodiments, a hole in the hole group may have a square shape as shown by 1003. In some embodiments, a hole in the hole group may have a circleshape as shown by 1004. In some embodiments, a hole in the hole group may have across shape as shown by 1005. In some embodiments, a hole in the hole group may havean angled rectangle shape as shown by 1006. Of course, any other suitable shapes are alsofeasible. For example, a hole in the hole group may have an angled square shape, anangled rectangle shape, an angled arc shape, an angled cross shape, and so on.

[00108] In some embodiments, each of the hole groups 431 and 432 may comprise one ormore holes. In this way, a relative bandwidth of the coupler may be increased. Forexample, a hole group may comprise 1 to 3 holes. In this way, a proper coupling degreemay be obtained.

[00109] The one or more holes may have any suitable shapes. Fig. 11 illustrates adiagram 1100 of example constructions of a hole group of a coupler according to someexample embodiments of the present disclosure. As shown in Fig. 11, a hole group 1101may comprise two rectangle holes. In some embodiments, a hole group 1102 maycomprise two diamond holes. In some embodiments, a hole group 1103 may comprisethree ellipse holes. These are merely examples, and the present disclosure does not limitthis aspect.

[00110] In some embodiments, an electric length between the hole groups 431 and 432may be within λ / 8 to 3λ / 8, where λ denotes a wavelength at a center frequency of anoperating bandwidth of the coupler. Of course, any other suitable electric length may alsobe feasible.

[00111] In some embodiments, an area of a hole group in the plurality of hole groups maybe within 1% * λ2, where λ denotes a wavelength at a center frequency of an operatingbandwidth of the coupler. Of course, any other suitable area values may also be feasible.6 . EXAMPLE MODELING SIMULATION

[00112] A simulation example will be described below with reference to Figs. 12A to 12C.To get the optimum couplings degree, electro-magnetic field simulation may be carried out.The calculation algorism is not limited. However, the size of the hole group should bemathematic described with one or two parameters. A parameter can be swept in a givenrange. The best results can be chosen for design.

[00113] Fig. 12A illustrates an example basic simulation model 1200A for optimization ofa coupler according to some example embodiments of the present disclosure. Assuming that a size of a hole group should be optimized for a coupling degree of -19 dB by 3.6GHz.A perspective view of a modeled coupler is as shown by 1201, and an enlarged view of themodeled coupler is as shown by 1202.

[00114] As shown in Fig. 12A, the modeled coupler comprises PCB 1 and PCB 2. ThePCB 1 comprises a substrate layer, a coupling line and a ground layer. The coupling lineis formed on the top surface of the substrate layer and has Port 1 and Port 2. The grouplayer is formed on the bottom surface of the substrate layer and is opened with two squareholes 1210. The PCB 2 comprises an upper substrate layer, another coupling line formedon the bottom surface of the upper substrate layer and having Port 3 and Port 4, a lowersubstrate layer formed under the upper substrate layer, and another ground layer formed onthe bottom surface of the lower substrate layer.

[00115] A typical thickness of PCB 1 for antenna network is 20 mil (0.5 mm) or 30 mil(0.762 mm). If the thickness is fixed, empirical formulas for network design arerecommended based on simulation results as shown in Table 1. There are the followingvariables: the length L and width W of holes 1210; the distance d of holes 1210; and awavelength λ at a center frequency of an operating bandwidth of the modeled coupler.Table 1 An Example of Variables

[00116] If the above mentioned variables are fixed, lengths of the two coupling lines maybe calculated by the above equation 7 according design requirements.

[00117] Fig. 12B illustrates a top view 1200B of the basic simulation model of FIG. 12A.As shown in Fig. 12B, each of the holes 1210 has a length L_win. The L_win mayinfluence the coupling degree. For an optimum result, the L_win should be varied in apredefined range, for example, 1.6mm-2.4 mm.

[00118] Fig. 12C illustrates a graph 1200C of a coupling degree varied with L_winaccording to some example embodiments of the present disclosure. As shown in Fig. 12C,a curve 1221 denotes a relationship between a couple degree and a frequency in case thatL_win=2.4. In this case, the couple degree is -18.675417 dB. A curve 1222 denotes arelationship between a couple degree and a frequency in case that L_win=2.2. In this case, the couple degree is -18.93624 dB. A curve 1223 denotes a relationship between a coupledegree and a frequency in case that L_win=2. In this case, the couple degree is-19.228423 dB. A curve 1224 denotes a relationship between a couple degree and afrequency in case that L_win=1.8. In this case, the couple degree is -19.575055 dB. Acurve 1225 denotes a relationship between a couple degree and a frequency in case thatL_win=1.6. In this case, the couple degree is -19.96076 dB.

[00119] To get the target coupling degree of -19 dB, L_win = 2.2 is chosen for design.Similarly, other parameters like distance of holes can be optimized as well.

[00120] So far, a coupler according to some embodiments of the present disclosure isdescribed. In the direction coupler, two coupling lines are formed at different layers andthe coupling between the two coupling lines is achieved by a plurality of hole or holegroups in a ground layer without using a metal via. Thus, PCB space and size may besaved, RF performance may be improved, and PCB cost may be reduced.EXAMPLE IMPLEMENTATION OF DEVICE

[00121] Correspondingly, embodiments of the present disclosure also provide an antennamodule. Fig. 13 illustrates a diagram of an antenna module 1300 according to someexample embodiments of the present disclosure.

[00122] As shown in Fig. 13, the antenna module 1300 comprises an antenna array 1310and a calibration network 1320 for the antenna array 1310. The calibration network 1320comprises a plurality of couplers 400 as described in Figs. 4 to 12C. It is to be understoodthat the antenna module may also comprise any other suitable additional elements. Forexample, the antenna module 1300 may also comprise a feeding network (not shown)coupled between the antenna array 1310 and the calibration network 1320. The pluralityof couplers 400 are configured to collect a portion of a RF signal transmitted via thefeeding network for use in antenna calibration of the calibration network 1320. Thepresent disclosure does not limit other details of the feeding network and the calibrationnetwork 1320.

[00123] Embodiments of the present disclosure also provide an electronic device. Theelectronic device comprises a plurality of couplers as described in Figs. 4 to 12C. Theelectronic device may be a communication device or a high-frequency device. Fig. 14illustrates a diagram of an electronic device 1400 according to some example embodimentsof the present disclosure. The electronic device 1400 can be implemented at or as at least a part of a network device or a terminal device.

[00124] As shown, the electronic device 1400 includes a processor 1410, a memory 1420coupled to the processor 1410, a suitable transmitter (TX) and receiver (RX) 1440 coupledto the processor 1410, and a communication interface coupled to the TX / RX 1440. Thememory 1410 stores at least a part of a program 1430. The TX / RX 1440 is forbidirectional communications. The TX / RX 1440 has an antenna module to facilitatecommunication, though in practice an Access Node mentioned in this application may haveseveral ones. The at least one antenna module may comprise one or more coupler asdescribed in Figs. 4 to 12C.

[00125] The communication interface may represent any interface that is necessary forcommunication with other network elements, such as X2 interface for bidirectionalcommunications between eNBs, S1 interface for communication between a MobilityManagement Entity (MME) / Serving Gateway (S-GW) and the eNB, Un interface forcommunication between the eNB and a relay node (RN), or Uu interface forcommunication between the eNB and a terminal device.

[00126] The program 1430 is assumed to include program instructions that, when executedby the associated processor 1410, enable the electronic device 1400 to operate inaccordance with the embodiments of the present disclosure. The embodiments herein maybe implemented by computer software executable by the processor 1410 of the electronicdevice 1400, or by hardware, or by a combination of software and hardware. Theprocessor 1410 may be configured to implement various embodiments of the presentdisclosure. Furthermore, a combination of the processor 1410 and memory 1420 mayform processing means 1450 adapted to implement various embodiments of the presentdisclosure.

[00127] The memory 1420 may be of any type suitable to the local technical network andmay be implemented using any suitable data storage technology, such as a non-transitorycomputer readable storage medium, semiconductor based memory devices, magneticmemory devices and systems, optical memory devices and systems, fixed memory andremovable memory, as non-limiting examples. While only one memory 1420 is shown inthe electronic device 1400, there may be several physically distinct memory modules in thedevice 1400. The processor 1410 may be of any type suitable to the local technicalnetwork, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based onmulticore processor architecture, as non-limiting examples. The electronic device 1400may have multiple processors, such as an application specific integrated circuit chip that isslaved in time to a clock which synchronizes the main processor.EXAMPLE IMPLEMENTATION OF METHOD

[00128] Correspondingly, embodiments of the present disclosure also provide a method forfabricating a coupler. Fig. 15 illustrates a flowchart of an example method 1500 forfabricating a coupler according to some example embodiments of the present disclosure.For the purpose of discussion, the method 1500 will be described with reference to Figs. 4to 6B. It is to be understood that the method 1500 may further include additional blocksor steps not shown and / or omit some shown blocks or steps, and the scope of the presentdisclosure is not limited in this regard.

[00129] As shown in Fig. 15, at block 1510, a first coupling line (for example, the couplingline 421) is formed on an upper surface of a first substrate layer (for example, the substratelayer 411). In some embodiments, the coupling line 421 may be formed by a microstripline. Of course, any other suitable ways are also feasible. In some embodiments, thesubstrate layer 411 may be formed from a low-loss dielectric material which may beexpensive. It is to be understood that the substrate layer 411 may be formed from anysuitable dielectric materials. In some embodiments, the substrate layer 411 may be amulti-layer substrate. Of course, the substrate layer 411 may be a single-layer substrate.

[00130] At block 1520, a second coupling line (for example, the coupling line 422) isformed on a lower surface of a second substrate layer (for example, the substrate layer 412).In some embodiments, the coupling line 422 may be formed by a microstrip line. Ofcourse, any other suitable ways are also feasible. In some embodiments, the substratelayer 412 may be formed from a different material from the substrate layer 411. Of course,the substrate layer 412 may be formed from the same material as the substrate layer 411.In some embodiments, the substrate layer 412 may be a multi-layer substrate. Of course,the substrate layer 412 may be a single-layer substrate.

[00131] At block 1530, a first ground layer (for example, the ground layer 423) is formedsuch that the ground layer 423 is located between a lower surface of the substrate layer 411and an upper surface of the substrate layer 412. A plurality of hole groups (for example,hole groups 431 and 432) are formed in the ground layer 423 and are geometrically designed such that an electro-magnetic field of the coupling line 421 is coupled to thecoupling line 422 through the plurality of hole groups. For example, the hole groups maybe designed in lengths, widths and shapes so that the electro-magnetic field of the couplingline 421 is coupled to the coupling line 422 through the hole groups.

[00132] In some embodiments, the ground layer 423 may be formed on the lower surfaceof the substrate layer 411. In some embodiments, the ground layer 423 may be formed onthe upper surface of the substrate layer 412.

[00133] In some embodiments, the hole group 431 or 432 may be comprised of only onehole. In some embodiments, the hole group 431 or 432 may be comprised of multipleholes. For example, the number of holes in a hole group may be between 1 and 3.

[00134] In some embodiments, the plurality of hole groups comprise two hole groups 431and 432. In these embodiments, the coupling line 421 and the coupling line 422 may beformed such that an electric length between the two hole groups 431 and 432 is within λ / 8to 3λ / 8, where λ denotes a wavelength at a center frequency of an operating bandwidth ofthe coupler. For example, the coupling line 421 and the coupling line 422 may begeometrically designed in lengths, widths and shapes so that the electric length between thetwo hole groups 431 and 432 is within λ / 8 to 3λ / 8.

[00135] In some embodiments, a hole group in the plurality of hole groups may be formedsuch that an area of a hole group in the plurality of hole groups is within 1% * λ2, where λdenotes a wavelength at a center frequency of an operating bandwidth of the coupler. Thearea of the hole group may refer to a total area of one or more holes in the hole group.

[00136] In some embodiments, the coupling line 421 and the substrate layer 411 may beformed in a PCB (for example, PCB 501), and the coupling line 422 and the substrate layer412 may be formed in another PCB (for example, PCB 502). In this case, the groundlayer 423 may be formed in any one of the two PCBs. In some embodiments, thesubstrate layer 411 may be formed from an expensive low-loss material, and the substratelayer 412 may be formed from a cheaper material. In some embodiments, the substratelayer 412 may be formed with a size smaller than that of the substrate layer 411. In thisway, PCB cost may be significantly reduced.

[00137] In some embodiments, the coupling line 421, the substrate layer 411, the groundlayer 423, the substrate layer 412 and the coupling line 422 may be formed in a multi-layerPCB. In these embodiments, the substrate layer 411 and the substrate layer 412 may be formed from the same material and may be formed with the same size.

[00138] In some embodiments, a third substrate layer (for example, the substrate layer 613)may be further formed on the substrate layer 411, and a second ground layer (for example,the ground layer 624) may be further formed on the substrate layer 613. In this way, thecoupling line 421 may be well isolated.

[00139] In some embodiments, a fourth substrate layer (for example, the substrate layer614) may be further formed on a lower surface of the substrate layer 412 to cover thecoupling line 422, and a third ground layer (for example, the ground layer 625) may befurther formed on a lower surface of the substrate layer 614. In this way, the coupling line422 may also be well isolated.

[00140] It is to be understood that the formation of the above layers or lines may beimplemented by any suitable semiconductor processes, and the present disclosure does notlimit this aspect.

[00141] Generally, various embodiments of the present disclosure may be implemented inhardware or special purpose circuits, software, logic or any combination thereof. Someaspects may be implemented in hardware, while other aspects may be implemented infirmware or software which may be executed by a controller, microprocessor or othercomputing device. While various aspects of embodiments of the present disclosure areillustrated and described as block diagrams, flowcharts, or using some other pictorialrepresentation, it will be appreciated that the blocks, apparatus, systems, techniques ormethods described herein may be implemented in, as non-limiting examples, hardware,software, firmware, special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

[00142] As an example, the embodiments of the present disclosure can be described in thecontext of the machine executable instruction which is included, for example, in a programmodule executed in a device on a target physical or virtual processor. Generally, theprogram module includes a routine, program, library, object, class, component, datastructure and the like, which executes a particular task or implement a particular abstractdata structure. In various embodiments, the functions of the program modules can bemerged or split among the program modules described herein. A machine executableinstruction for a program module can be executed locally or within a distributed device.In a distributed device, a program module can be located in both of a local and a remote storage medium.

[00143] Program code for carrying out methods of the present disclosure may be written inany combination of one or more programming languages. The program code may beprovided to a processor of a general purpose computer, special purpose computer, or otherprogrammable data processing apparatus, such that the program codes, when executed bythe processor or controller, cause the functions / operations specified in the flowcharts and / orblock diagrams to be implemented. The program code may execute entirely on a machine,partly on the machine, as a stand-alone software package, partly on the machine and partlyon a remote machine or entirely on the remote machine or server.

[00144] In the context of this disclosure, computer program code or related data can becarried by any appropriate carrier, such as an apparatus, device or processor can executevarious processing and operations as described above. The example of the carrier includesa signal, a computer readable medium and the like. The example of the signal mayinclude a signal broadcast electrically, optically, wirelessly, acoustically or in other forms,such as a carrier, an infrared signal and the like.

[00145] A computer readable medium may be any tangible medium that may contain, orstore a program for use by or in connection with an instruction execution system, apparatusor device. The computer readable medium may be a computer readable signal medium ora computer readable storage medium. A computer readable medium may include but notlimited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductorsystem, apparatus, or device, or any suitable combination of the foregoing. More specificexamples of the computer readable storage medium would include an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, a random accessmemory (RAM), a read-only memory (ROM), an erasable programmable read-onlymemory (EPROM or Flash memory), an optical fiber, a portable compact disc read-onlymemory (CD-ROM), an optical storage device, a magnetic storage device, or any suitablecombination of the foregoing.

[00146] Further, although operations of the present methods are described in a particularorder in the drawings, it does not require or imply that these operations are necessarilyperformed according to this particular sequence, or a desired outcome can only be achievedby performing all shown operations. On the contrary, the execution order for the steps asdepicted in the flowcharts may be varied. Alternatively, or in addition, some steps may be omitted, a plurality of steps may be merged into one step, or a step may be divided into aplurality of steps for execution. It would be appreciated that features and functions of twoor more devices according to the present disclosure can be implemented in combination in asingle implementation. Conversely, various features and functions that are described inthe context of a single implementation may also be implemented in multiple devices.

[00147] Although the present disclosure has been described with reference to variousembodiments, it should be understood that the present disclosure is not limited to thedisclosed example embodiments. The present disclosure is intended to cover variousmodifications and equivalent arrangements included in the spirit and scope of the appendedclaims.

Claims

1. A coupler (400), comprising: a first substrate layer (411); a second substrate layer (412) located below the first substrate layer (411); a first coupling line (421) located on an upper surface of the first substrate layer (411); a second coupling line (422) located on a lower surface of the second substrate layer (412); and a first ground layer (423) located between a lower surface of the first substrate layer (411) and an upper surface of the second substrate layer (412), a plurality of hole groups (431, 432) being formed in the first ground layer (423) and being geometrically designed such that an electro-magnetic field of the first coupling line (421) is coupled to the second coupling line (422) through the plurality of hole groups.

2. The coupler of claim 1, wherein the first coupling line (421) and the first substrate layer (411) are located in a first printed circuit board (501), and the second coupling line (422) and the second substrate layer (412) are located in a second printed circuit board (502) different from the first printed circuit board (501).

3. The coupler of claim 2, wherein the first ground layer (423) is formed on a lower surface of the first substrate layer (411).

4. The coupler of claim 2, wherein the first ground layer (423) is formed on an upper surface of the second substrate layer (412).

5. The coupler of claim 1, wherein the first coupling line (421), the first substrate layer (411), the first ground layer (423), the second substrate layer (412) and the second coupling line (422) are located in a multi-layer printed circuit board.

6. The coupler of claim 1, wherein a hole group in the plurality of hole groups comprises one or more holes.

7. The coupler of claim 1, wherein the plurality of hole groups comprise two hole groups and an electric length between the two hole groups is within λ / 8 to 3λ / 8, where λ denotes a wavelength at a center frequency of an operating bandwidth of the coupler.

8. The coupler of claim 1, wherein an area of a hole group in the plurality of hole groups is within 1% * λ2, where λ denotes a wavelength at a center frequency of an operating bandwidth of the coupler.

9. The coupler of claim 1, further comprising: a third substrate layer (613) located on the first substrate layer (411); and a second ground layer (624) located on the third substrate layer (613).

10. The coupler of claim 1, further comprising: a fourth substrate layer (614) located below the second substrate layer (412); and a third ground layer (625) located below the fourth substrate layer (614).

11. An antenna module (1300) comprising: an antenna array (1310); and a calibration network (1320) for the antenna array, the calibration network comprising a plurality of couplers (400) of any of claims 1 to 10.

12. An electronic device (1400) comprising an antenna module (1300) of claim 11.

13. An electronic device comprising a coupler (400) of any of claims 1-10.

14. A method (1500) for fabricating a coupler (400), comprising: forming (1510) a first coupling line (421) on an upper surface of a first substrate layer (411); forming (1520) a second coupling line (422) on a lower surface of a second substrate layer (412), the second substrate layer (412) being located below the first substrate layer (411); and forming (1530) a first ground layer (423) such that the first ground layer (423) is located between a lower surface of the first substrate layer (411) and an upper surface of the second substrate layer (412), and such that a plurality of hole groups (431, 432) are formed in the first ground layer (423) and are geometrically designed such that an electro-magnetic field of the first coupling line (421) is coupled to the second coupling line (422) through the plurality of hole groups.

15. The method of claim 14, wherein the first coupling line (421) and the first substrate layer (411) are formed in a first printed circuit board (501), and the second coupling line (422) and the second substrate layer (412) are formed in a second printed circuit board (502) different from the first printed circuit board (501).

16. The method of claim 15, wherein forming the first ground layer (423) comprises: forming the first ground layer (423) on the lower surface of the first substrate layer (411).

17. The method of claim 15, wherein forming the first ground layer (423) comprises: forming the first ground layer (423) on the upper surface of the second substrate layer (412).

18. The method of claim 14, wherein the first coupling line (421), the first substrate layer (411), the first ground layer (423), the second substrate layer (412) and the second coupling line (422) are formed in a multi-layer printed circuit board.

19. The method of claim 14, wherein a hole group in the plurality of hole groups is comprised of one or more holes.

20. The method of claim 14, wherein the plurality of hole groups comprise two hole groups, and wherein the first coupling line (421) and the second coupling line (422) are formed such that an electric length between the two hole groups is within λ / 8 to 3λ / 8, where λ denotes a wavelength at a center frequency of an operating bandwidth of the coupler.

21. The method of claim 14, wherein a hole group in the plurality of hole groups is formed such that an area of a hole group in the plurality of hole groups is within 1% * λ2, where λ denotes a wavelength at a center frequency of an operating bandwidth of the coupler.

22. The method of claim 14, further comprising: forming a third substrate layer (613) on the first substrate layer (411); and forming a second ground layer (624) on the third substrate layer (613).

23. The method of claim 14, further comprising: forming a fourth substrate layer (614) below the second substrate layer (412); and forming a third ground layer (625) below the fourth substrate layer (614).