Patent Application
20230253703
Embodiments of the present disclosure relate generally to wireless communication devices. More particularly, embodiments of the invention relate to ultra wideband isolation for coupling reduction in antenna arrays.
In recent years, wireless communication has been experiencing rapid advancements driven by demands from newer applications at every front of wireless technology, such as mobile communications (e.g., 5G and beyond), satellite communications, or Internet of Things (IoT). Different technologies have respective specific requirements, and based on a particular application, the demand may be for high speed and low latency, increased capacity, low power consumption and mass devices connection, and so on.
In the near future, there will be applications where a number of these technologies may come together in a single terminal to provide ubiquitous services among the various technologies. Also, in other application scenarios the demand may be for supporting the technologies globally across various geographic regions. For example, the prominent frequency bands in mmWave 5G communications globally range from 24 GHz all the way to 43.5 GHz, although each region may only be operating in a limited part of this spectrum. Therefore, to cater the needs for such applications it will be desirable that the front end of the terminal supports a wide frequency bandwidth.
Moreover, those demands from the underlying applications place stringent requirement on device front-end and antenna designs. The antenna, which is probably the single most important component of a wireless communication system, acts as the interface between a terminal device, and the wireless communication medium or the wireless channel as it is often called. Apart from wider frequency bandwidth, the trend is also towards the antennas being agile in beam formation, thereby providing ways to electronically scanned arrays or phased arrays.
To one skilled in antenna design, it will be known that for an antenna to be able to cover a wide operating bandwidth (whether to cater multiple technologies, to cover multiple regional areas, or both), the antenna is required to have a larger electrical volume. For a planar antenna fabricated using conventional printed circuit board (PCB) technologies, the antenna needs to be supported on thicker dielectric material (also called substrate). However, at the same time, a thicker substrate supports surface waves which are detrimental to the antenna’s performance. Surface waves in the dielectric material increase coupling between antenna elements of an antenna array, thereby incurring power loss in nearby antenna elements rather than contributing to direct radiation. This results in lower antenna efficiency and even scan blindness (meaning the antenna is not able to radiate in certain direction(s), and all power is lost in neighboring antenna elements).
In addition, wide beam scanning places further constraint on antenna element spacing for electronically steerable antennas (ESAs). Closer element spacing, which is required to avoid grating lobes in a scanned pattern (strong radiation in directions opposing the main lobe, often undesired), means even stronger coupling between neighboring elements through the surface waves.
Embodiments of the invention are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.
Various embodiments and aspects of the inventions will be described with reference to details discussed below, and the accompanying drawings will illustrate the various embodiments. The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of various embodiments of the present invention. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present inventions.
Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment.
Note that in the corresponding drawings of the embodiments, signals are represented with lines. Some lines may be thicker or have a slash over the lines, to indicate more constituent signal paths, such as a differential signal, and/or have arrows at one or more ends, to indicate primary information flow direction. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme.
Throughout the specification, and in the claims, the term “connected” means a direct electrical connection between the things that are connected, without any intermediary devices. The term “coupled” means either a direct electrical connection between the things that are connected, or an indirect connection through one or more passive or active intermediary devices. The term “circuit” means one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function. The term “signal” means at least one current signal, voltage signal or data/clock signal. The meaning of “a”, “an”, and “the” include plural references. The meaning of “in” includes “in” and “on”.
As used herein, unless otherwise specified the use of the ordinal adjectives “first,” “second,” and “third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner. The term “substantially” herein refers to being within 10% of the target.
Embodiments of the disclosure relate to an antenna or antenna apparatus designed to reduce surface wave coupling among tightly packed antenna elements in an antenna array. As described in more detail herein below, this can be achieved by use of surface wave filtering structures (e.g., frequency selective structures) around the antenna elements that act as surface wave mode filters to reduce surface wave interaction between adjacent antenna elements and improve element-to-element isolation over wideband spectrum. The reduction of surface wave coupling can also improve element patterns in the antenna array. As such, the embodiments of the disclosure described herein can play a positive and vital role in boosting and promoting the development of a new generation of wireless communication antenna systems where such antenna arrays are in demand.
According to a first aspect, an antenna apparatus includes a substrate, antenna elements on the substrate, and surface wave filtering structures on the substrate. Each surface wave filtering structure is operable to decouple surface wave coupling between adjacent antenna elements of the antenna elements.
In one embodiment, each surface wave filtering structure is disposed on a side of an antenna element or between a pair of antenna elements of the antenna elements.
In one embodiment, the antenna apparatus further includes a printed circuit board (PCB) comprising a coating of dielectric material forming the substrate.
In one embodiment, isolation between the adjacent antenna elements is at least 10 decibels (dB) in low-band spectrum and wideband spectrum.
In one embodiment, each antenna element is spaced from another antenna element based on a fraction of free space wavelength (e.g., ranging from about 0.3 to 0.6 free space wavelength).
In one embodiment, the antenna elements include wideband antenna elements.
According to a second aspect, a radio frequency (RF) transceiver includes an antenna including a substrate, antenna elements on the substrate, and surface wave filtering structures on the substrate. Each surface wave filtering structure is operable to decouple surface wave coupling between adjacent antenna elements of the plurality of antenna elements.
According to a third aspect, a radio frequency (RF) frontend circuit includes a digital signal processing unit, and a transceiver coupled to the digital signal processing unit to transmit and receive signals to and from the digital signal processing unit. The transceiver includes an antenna including a substrate, antenna elements on the substrate, and surface wave filtering structures on the substrate. Each surface wave filtering structure is operable to decouple surface wave coupling between adjacent antenna elements of the plurality of antenna elements.
In a radio receiver circuit, the RF frontend is a generic term for all the circuitry between the antenna up to and including the mixer stage. It consists of all the components in the receiver that process the signal at the original incoming radio frequency, before it is converted to a lower frequency, e.g., IF. A baseband processor is a device (a chip or part of a chip) in a network interface that manages all the radio functions (all functions that require an antenna).
In one embodiment, RF frontend module 101 includes one or more RF transceivers, where each of the RF transceivers transmits and receives RF signals within a particular frequency band (e.g., a particular range of frequencies such as non-overlapped frequency ranges) via one of a number of RF antennas. The RF frontend IC chip further includes an IQ generator and/or a frequency synthesizer coupled to the RF transceivers. The IQ generator or generation circuit generates and provides an LO signal to each of the RF transceivers to enable the RF transceiver to mix, modulate, and/or demodulate RF signals within a corresponding frequency band. The RF transceiver(s) and the IQ generation circuit may be integrated within a single IC chip as a single RF frontend IC chip or package.
In an embodiment, substrate 301 may be part of a printed circuit board (PCB), not shown, or substrate 301 may be a layer or coating of the PCB. Surface wave filtering structures 302A-C and antenna elements 303A-B (which may collectively form an antenna element array) may be supported on substrate 301. In an embodiment, each surface wave filtering structure may be disposed around an antenna element (e.g., on a side of the antenna element), or in between two antenna elements, without being in direct contact with the antenna elements. Antenna elements 303A-B may be closely spaced (in terms of wavelengths in free space, e.g., speed of light divided by 5G frequency) to avoid, for example, grating lobes for wide angle scanning capability. The antenna element spacing can vary, for example, from about 0.3 wavelength at lower frequencies of a supported band to about 0.5 to 0.6 wavelength at a higher range of the supported band.
In an embodiment, surface wave filtering structures 302A-C are configured to reduce surface waves in substrate 301, thereby improving isolation between antenna elements 303A-B, particularly in a tightly packed configuration. The arrangement of surface wave filtering structures 302A-C also improves antenna radiation pattern properties of antenna elements 303A-B.
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In the foregoing specification, embodiments of the invention have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
