Patent Application
20230118728
The present disclosure relates to an antenna arrangement for a communication device. The disclosure further relates to a communication device comprising such an antenna arrangement.
Currently antennas in mobile devices, such as user equipments (UEs), need to be placed in lossy and challenging environments, and yet provide efficient radiation. This calls for practical antenna structures approaching the ultimate efficiency limits for small antennas. Finding the optimal antenna shape may be very challenging and laborious due to high computational burden of electromagnetic simulations and complex relation between antenna shape and its electrical properties. Hence, there is no guarantee that the designer can find the optimal solution.
The theoretical and numerical electromagnetics research community focuses on finding mathematically optimal solutions. The research community has derived fundamental limitations for the antennas, such as the famous Chu's limit defining the upper limit for the performance of an electrically small antenna in terms of bandwidth and efficiency. The research community has also established relatively straightforward ways to find the ultimately best current or field distributions of an antenna, which could result in the best possible radiation properties. However, incorporating such optimal current distributions into practical antenna design is challenging.
Embodiments of the disclosure provide a solution which mitigates or solves drawbacks and problems of conventional solutions.
According to a first aspect of the disclosure, an antenna arrangement for a communication device is provided, the antenna arrangement comprising:
a substrate having a top surface and a bottom surface,
a top conductive patch arranged on the top surface, the top conductive patch comprising a first section and a second section adjoining the first section,
a bottom conductive patch arranged on the bottom surface opposite to the top conductive patch,
one or more feed circuits configured to carry a radio frequency, RF, signal to or from the top conductive patch,
wherein the top conductive patch comprises two or more coupling points in which the top conductive patch is coupled to the one or more feed circuits, the two or more coupling points comprising a first coupling point located in the first section and a second coupling point located in the second section, such that the RF signal has a first phase in the first coupling point and a second phase in the second coupling point, and wherein
a first slot extends in the top conductive patch between the first coupling point and the second coupling point.
The top conductive patch can act as an antenna for capturing or radiating a RF signal and may generally be of a design known in the art as a patch antenna. The top conductive patch can hence herein further be referred to as an antenna patch. The bottom conductive patch can act as a ground plane and can herein further be referred to as a ground patch.
A coupling point can herein be understood to correspond to a point-like region with a spatial extension which is small compared to the area of the top conductive patch.
An advantage of the antenna arrangement according to the first aspect is that multiple feed points in the form of coupling points make it possible to better control the current distribution in the antenna structure as compared to a single-feed antenna with only one coupling point. Better control of current distribution makes it possible to achieve high radiation efficiency, desired directive or polarization properties, and/or desired input impedance.
In an implementation form of an antenna arrangement according to the first aspect, the antenna arrangement further comprises
a first controllable capacitor arranged at the first slot and configured to vary the electrical length of the first slot.
An advantage of the antenna arrangement according to this implementation form is that the controllable capacitor makes it possible to control the current distribution on the antenna and even better compared to case where the antenna is fixed. Better control of current distribution makes it easier to maintain high radiation efficiency, good matching, and possible other radiation properties across a wider frequency band in different use scenarios, for instance if a user's hand is in the proximity of the antenna.
In an implementation form of an antenna arrangement according to the first aspect, the first slot has an open end and a closed end, and the first controllable capacitor is arranged between the open end and the closed end of the first slot. The first controllable capacitor may further be arranged at the open end or at the closed end of the first slot.
An advantage of the antenna arrangement according to this implementation form is that potentially high electric field is formed across the slot/gap and consequently the effect of the controllable capacitor on the currents is increased. The slot potentially increases the current controllability with the controllable capacitor.
In an implementation form of an antenna arrangement according to the first aspect, the second phase is 180 degrees phase rotated in relation to the first phase.
An advantage of the antenna arrangement according to this implementation form is that a 180 degree phase offset between the feeds of the different coupling points commonly results into a high efficiency and good impedance matching. Furthermore, the 180 degree phase difference is straightforward to realize with several different passive structures.
In an implementation form of an antenna arrangement according to the first aspect, the antenna arrangement further comprises
a third coupling point located in the first section such that the RF signal has a third phase in the third coupling point,
a fourth coupling point located in the second section such that the RF signal has a fourth phase in the fourth coupling point, and
a second slot extending in the top conductive patch and being arranged between the third coupling point and the fourth coupling point.
An advantage of the antenna arrangement according to this implementation form is that the controllability of the antenna improves with an increasing number of coupling points/feeds. As compared to two coupling point case, four coupling points potentially offer better electrical antenna performance.
In an implementation form of an antenna arrangement according to the first aspect,
the first phase and the third phase have the same phase and the second phase and the fourth phase have the same phase; or
the first phase, the second phase, the third phase and the fourth phase have different phases.
An advantage of the antenna arrangement according to this implementation form is the fixed feed phases result to simpler feed structure than a realization, where feed phases are variables. Relatively good performance can typically be obtained even across a relatively wide band using fixed feed phases. This way no controllable RF phase shifters are needed and the feed structure is simpler.
In an implementation form of an antenna arrangement according to the first aspect, the antenna arrangement further comprises
a second controllable capacitor arranged at the second slot and configured to vary the electrical length of the second slot.
An advantage of the antenna arrangement according to this implementation form is that current controllability improves with the number of controllable capacitors on the antenna. Better controllability makes it possible to conserve a good matching, high efficiency, and other performance parameters across wider band and broader set of use cases. Furthermore, larger number of controllable capacitors potentially result into more uniform current distribution on the structure. More uniform current distribution consequently results into lower conduction losses.
In an implementation form of an antenna arrangement according to the first aspect, the second slot has an open end and a closed end, and the second controllable capacitor is arranged between the open end and the closed end of the second slot. The second controllable capacitor may further be arranged at the open end or at the closed end of the second slot.
An advantage of the antenna arrangement according to this implementation form is that the electric field across the slot is typically large, especially near the open end of the slot and far from the closed end of the slot. The larger the electric field across the controllable capacitor, the larger is its potential effect on the current distribution. Therefore, the controllability of the structure with the controllable capacitors can be improved by introducing a slot and placing a controllable capacitor across it.
In an implementation form of an antenna arrangement according to the first aspect, the open end of the first slot and the open end of the second slot are arranged on opposite sides of the top conducting patch.
An advantage of the antenna arrangement according to this implementation form is that this kind of structure with symmetrical layout could lead to fairly uniform current distribution and yet good current controllability. Uniform current distribution potentially leads to lower conduction losses.
In an implementation form of an antenna arrangement according to the first aspect, the first slot and the second slot extend in opposite directions and are aligned with each other.
An advantage of the antenna arrangement according to this implementation form is that this symmetric arrangement leads to symmetric feed port impedances and feed signal phases. This potentially results into simplified feed network and makes it easier to use fixed 180 degree phase shifted feed signals.
In an implementation form of an antenna arrangement according to the first aspect, the first slot and the second slot at least partially demarks the first section and the second section from each other.
In an implementation form of an antenna arrangement according to the first aspect, the first coupling point, the second coupling point, the third coupling point and the fourth coupling point are symmetrically arranged on the top conductive patch.
An advantage of the antenna arrangement according to this implementation form is that this symmetric arrangement leads to symmetric feed port impedances and feed signal phases. This potentially results into simplified feed network and makes it easier to use fixed 180 degree phase shifted feed signals.
In an implementation form of an antenna arrangement according to the first aspect, the RF signal in each coupling point have the same amplitude.
An advantage of the antenna arrangement according to this implementation form is that the feed network is potentially simpler as compared to a case where feed signal amplitudes should be arbitrary or controllable.
In an implementation form of an antenna arrangement according to the first aspect, the antenna arrangement further comprises
a single feed circuit configured to carry the RF signal,
a power divider coupled to the single feed circuit and configured to divide the RF signal to each coupling point and
a phase shifter for each coupling point wherein each phase shifter is coupled to the power divider and is configured to control the phase of the RF signal provided to its respective coupling point.
An advantage of the antenna arrangement according to this implementation form is that variable phase shifters provide good control of current distribution in the antenna structure. This makes it possible to achieve a good performance over a wide set of use cases and across a wide band. On the other hand, variable phase shifters realized with integrated circuit technology can be very inexpensive, small and easy to integrate with the antenna. It should be noted that also the power divider can be realized inside a multi-channel phase shifter chip. When using a multi-channel phase shifter chip, single chip could feed the whole antenna structure.
In an implementation form of an antenna arrangement according to the first aspect, the antenna arrangement further comprises at least one of
a first feed circuit configured to carry the RF signal with the first phase,
a second feed circuit configured to carry the RF signal with the second phase,
a third feed circuit configured to carry the RF signal with the third phase, and
a fourth feed circuit configured to carry the RF signal with the fourth phase.
An advantage of the antenna arrangement according to this implementation form is that no power dividers or phase shifters are needed.
According to a second aspect of the disclosure, a communication device is provided for a wireless communication system, the communication device comprising an antenna arrangement according to any one of the preceding implementation forms of an antenna arrangement according to the first aspect.
In an implementation form of a communication device according to the second aspect, the communication device comprises
a chassis,
a glass layer,
a dielectric layer arranged between the chassis and the glass layer;
and wherein
the antenna arrangement is arranged between the chassis and the dielectric layer.
Further applications and advantages will be apparent from the following detailed description.
The appended drawings are intended to clarify and explain different embodiments, in which:
An optimal current or field distributions of an antenna can be theoretically determined using numerical optimization. However, incorporating optimal current distributions into practical antenna design is challenging. The calculated antenna structures are often simple in geometry, far from the complicated models of antenna structures in modern wireless devices. A major challenge is that the obtained current distribution is difficult to excite in practice, as any practical excitation element easily alters the optimal distribution.
Conventional antenna solutions for obtaining optimal current distribution includes: parasitic metal pixel layers excited through aperture coupling or by a single antenna, collaboratively fed antenna elements, multifeed patch antennas, two separated patches fed with differential signal, pixelized/gridded antennas having single feed or two separate feeds.
The conventional solutions suffer from problems such as e.g. non-optimal feed of the antenna, that complex excitations are used, and that relatively thick antennas are needed. Thus, none of the conventional solution manages to provide an optimal current distribution in an antenna in a controlled and systematic manner.
The above-mentioned drawbacks are addressed and the current distribution is improved in antenna arrangements disclosed herein. The improved current distribution is achieved with an antenna arrangement that enables a desired current distribution to be realized in the antenna in a controlled and systematic manner.
With reference to
The top conductive patch 102 comprises a first section 106 and a second section 110 adjoining the first section 106, as shown in
In the embodiment shown in
The top conductive patch 102 further comprises a first slot 112 extending in the top conductive patch 102 between the first coupling point 104 and the second coupling point 108, as shown in
A first controllable capacitor 114 may be arranged at the first slot 112 and configured to vary the electrical length of the first slot 112. The first controllable capacitor 114 may hence tune the electrical length of the first slot 112 and hence the resonant frequency of the antenna arrangement 100. Controllable capacitor can be for instance a varactor diode, ferroelectric varactor, or switchable capacitor bank realized with integrated circuit or MEMS (microelectromechanical systems) technology. The varactor diode and ferroelectric varactor are analogue devices and their capacitance is controlled by a DC (direct current) bias voltage or current. They are typically connected to the antenna circuit using DC block capacitors and RF choke inductors to separate bias circuit from the RF circuit. Capacitor banks are typically digital components. They have separate ports for RF signal and digital control signal. The digital control signal is used to select the capacitance of the component from a set of discrete capacitance states available. The capacitance affects the current distribution on the antenna structure, and the current distribution subsequently determines all the electrical properties of the antenna, including input impedance, radiation efficiency, radiation pattern and polarization. Therefore, by varying/altering the capacitance, the properties of the antenna can be controlled.
With reference to
In embodiments, the first phase P1 and the third phase P3 have the same phase and the second phase P2 and the fourth phase P4 have the same phase. In such embodiments, the second phase P2 and the fourth phase P4 may be 180 degrees phase rotated in relation to the first phase P1 and the third phase P3. However, the first phase P1, the second phase P2, the third phase P3 and the fourth phase P4 may in embodiments instead have different phases. A 180 degree phase difference between the ports typically result in good radiation properties and impedance matching, especially when the structure is symmetric. If the antenna is asymmetric, or if it is placed on asymmetric environment, e.g., on a size of a mobile phone, other than 180 degree offset feed signals might provide better performance.
With reference to
The antenna arrangement 100 with four coupling points 104, 108, 116, 118 further comprises a second slot 120 different form the first slot 112 and extending in the top conductive patch 102 and being arranged between the third coupling point 116 and the fourth coupling point 118. In a similar way as for the first slot 112, a second controllable capacitor 122 may be arranged at the second slot 120 and configured to vary the electrical length of the second slot 120. In embodiments, the second slot 120 has an open end 134 and a closed end 134′. The second controllable capacitor 122 may be arranged between the open end 134 and the closed end 134′ of the second slot 120, including at the open end 134 or at the closed end 134′. In the embodiment shown in
With reference to
The antenna arrangement 100 further comprises a power divider 144 coupled to the single feed circuit 142 and configured to divide the RF signal to each coupling point. In the embodiment shown in
The antenna arrangement 100 further comprises a phase shifter 146a; 146b; 146c; 146d for each coupling point 104; 108; 116; 118. Each phase shifter 146a; 146b; 146c; 146d is coupled to the power divider 144 and is configured to control the phase of the RF signal provided to its respective coupling point 104; 108; 116; 118. Thus, each phase shifter 146a; 146b; 146c; 146d receives a RF signal from the power divider 144 and provides the RF signal with a specific phase to its respective coupling point 104; 108; 116; 118.
In the embodiment shown in
As previously mentioned, the first phase P1 and the third phase P3 may have the same phase and the second phase P2 and the fourth phase P4 may have the same phase, or the first phase P1, the second phase P2, the third phase P3 and the fourth phase P4 may have different phases.
In embodiments, the first feed circuit 142a and the third feed circuit 142c may hence provide the RF signal with the first phase P1 to the first coupling point 104 and the third coupling point 116, respectively, while the second feed circuit 142b and the fourth feed circuit 142d may provide the RF signal with the second phase P2 to the second coupling point 108 and the fourth coupling point 118, respectively. Alternatively, the first feed circuit 142a, the second feed circuit 142b, the third feed circuit 142c, the fourth feed circuit 142d may provide different phases P1; P2; P3; P4 to their respective coupling point 104; 108; 116; 118.
Both in embodiments where a single feed circuit 142 is used and where multiple feed circuits 142a, 142b, 142c, 142d are used, the feed circuit(s) may be implemented using at least one of vias, capacitive feeds, aperture coupling, and microstrip line feeds.
In embodiments, the top conductive patch 102 may be a metallic patch and be implemented on the substrate 150 such as e.g. a low-loss substrate such as Teflon. The top conductive patch 102 may further be a planar patch realized on a PCB. Furthermore, instead of the top conductive patch 102 being a metallic patch, the top conductive patch 102 may in embodiments be implemented as a hole in otherwise metallic structure top layer. Such a structure is a negative of previously described structures, that is, non-metal regions and metal regions are interchanged. Such negative or complementary structures are commonly used in antennas.
With reference to
The chassis 202 may further be denoted base 202 or body 202 of the communication device 200 and may comprise one or more batteries and one or more PCB structures including one or more processors and memory devices which are not shown in
In a non-limiting example, the thickness of the glass layer 204 may be 0.55 mm, the thickness of the dielectric layer 206 may be 0.3 mm, the thickness of the antenna arrangement 100 may be 0.5 mm, and the thickness of the chassis 202 may be 2.5 mm.
The antenna arrangement 100 may further be used to realize antennas in other challenging environments. For example, antennas on wearable and implantable devices tend to be highly lossy, and the antenna arrangement 100 can help increase the efficiency in such devices.
Additionally, very thin conformal antennas are needed in many applications. For example, automobile antennas are preferred to be visually invisible and further preferably realized either on screens or other surfaces. Conformal antennas are also needed in airplanes, trains and ships. The antenna arrangement 100 can help increase the efficiency of very thin conformal antennas.
Dish antennas used for satellite reception are often considered aesthetically problematic. Ideally satellite antennas would be thin and installed on building walls in an unobtrusive manner. Such thin planar antennas however suffer from low efficiency if realized traditionally. Thus, the antenna arrangement 100 can help increase the efficiency also in such antennas.
The first step in analytical solving of coupling point currents that maximize the radiation efficiency is to construct the far-field pattern a linear combination of port currents. The far field is
where {right arrow over (K)}k=Kkθ(θ, ϕ)ûθ+Kkϕ(θ, ϕ)ûϕ maps the current ik at port k to a far-field vector. Solving current-far field-basis K for all ports requires formulation of N equations
where {right arrow over (E)}k is the far field when only port k is excited, and the remaining ports are terminated.
The current element ik,j is the induced current at port j, when port k is excited. Now the port specific far fields can be defined as a matrix decomposition for each angle and frequency
E(θ,ϕ)=IK(θ,ϕ), (3)
where E and K are column vectors with a length of N containing elements {right arrow over (E)}k and {right arrow over (E)}j, respectively. I is a N×N matrix containing element ik,j. When the far fields and current for individual port excitations are known, it is straight forward to compute K.
When the current-far field-basis K is known, we can compute the radiation efficiency corresponding any current excitation vector
I=[i1. . . ik. . . iN]T (4)
with ik being total current at port k.
Now the time-averaged power radiated to the far field can be expressed as
where Δθ=θp+1−θp, Δϕ=ϕq+1−ϕq and
{circumflex over (K)}=[{circumflex over (K)}1. . . {circumflex over (K)}k. . . {circumflex over (K)}N]. (6)
{circumflex over (K)}k is a column vector containing elements
K
k
pol(θp,ϕq)√{square root over (sin θp)},pol∈{θ,ϕ},p∈[1 . . . P]−,q∈[1 . . . Q].
Thus, the size of the matrix is 2PQ×N.
The power accepted to the antenna structure is calculated from the port voltages and currents
S
acc=½UHI=½(ZI)HI=½IHZHI, (7)
where Z is the impedance matrix of the N-port antenna. However, only the real part of the power contributes to the radiated power, i.e.
P
acc
=
{S
acc}=¼IH(ZH+Z)I. (8)
As a result, the radiation efficiency can be written in terms of two powers as
The computed radiation efficiency has a general from of Rayleigh quotient, which can be solved as a general eigenvalue problem for currents I. The maximum radiation efficiency is obtained by
with corresponding eigenvector giving the optimal currents.
Embodiments disclosed herein have improved performance compared to conventional solutions. It has been concluded that the radiation efficiency of the present antenna arrangement may be approximately from −6 dB to −2 dB. The total efficiency is increased as well from below −6 dB to above −4 dB. While the total efficiency increases the overall shape of the radiation pattern remains similar for the present antenna arrangement. Also, the beam-width is larger for the present antenna arrangement and the radiation to back direction is reduced by approximately 5 dB compared to conventional solutions.
Further, the total active reflection coefficient of the antenna can be shifted as the capacitance value is changed. The total efficiency of approximately more than −5.8 dB is achievable between 3.3-4.2 GHz, while the instantaneous bandwidth is 100 MHz when the capacitance value is varied between 0.847-2.96 pF.
Non-limiting example values for a variable capacitance (also known as a varicap) may be between 0.4-5.0 pF, such as between 0.4-2.5 pF or 1.0-5.0 pF depending on application. The tuning range of the variable capacitance may e.g. be 1:5.
The communication device 200 or mobile device 200 in this disclosure includes but is not limited to: a UE such as a smart phone, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having a wireless communication function, a computing device or another processing device connected to a wireless modem, an in-vehicle device, a wearable device, an integrated access and backhaul node (IAB) such as mobile car or equipment installed in a car, a drone, a device-to-device (D2D) device, a wireless camera, a mobile station, an access terminal, an user unit, a wireless communication device, a station of wireless local access network (WLAN), a wireless enabled tablet computer, a laptop-embedded equipment, an universal serial bus (USB) dongle, a wireless customer-premises equipment (CPE), and/or a chipset. In an Internet of things (JOT) scenario, the communication device 200 may represent a machine or another device or chipset which performs communication with another wireless device and/or a network equipment. The UE may further be referred to as a mobile telephone, a cellular telephone, a computer tablet or laptop with wireless capability. The UE in this context may e.g. be portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a station (STA), which is any device that contains an IEEE 802.11-conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as NR.
Moreover, it is realized by the skilled person that embodiments of the communication device 200 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.
Especially, the processor(s) of the communication device 200 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.
Finally, it should be understood that the invention is not limited to the embodiments described above, but relates to and incorporates all embodiments within the scope of the appended independent claims.
This application is a continuation of International Application No. PCT/EP2020/061638, filed on Apr. 27, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2020/061638 | Apr 2020 | US |
| Child | 17975253 | US |
