Abstract: A distributed antenna includes a strip member extending in a strip-like shape including a dielectric body of a plate shape having a first surface that is one surface of the dielectric body and a second surface that is opposite to the first surface; a transmission line provided on the first surface, on the second surface, or between the first surface and the second surface; and a plurality of antenna elements electrically connected to the transmission line and disposed in a distributed manner on the first surface or on the second surface, or electrically connected to the transmission line and disposed in a distributed manner between the first surface and the second surface.

Abstract: An antenna module radiates radio waves upon receiving a radio-frequency signal output from an RFIC. The antenna module includes flat radiating elements that radiate radio waves in a first polarization direction, feed conductors that each supply a radio-frequency signal from the RFIC to an associated one of the radiating elements, and a ground electrode disposed opposite the radiating elements. As viewed from the RFIC, frequency characteristics of an impedance of the radiating element are different from frequency characteristics of an impedance of the radiating element. Under a condition a frequency band in which a return loss is less than or equal to a predetermined value is defined as an operable band width in each of the radiating elements, the operable band width of the radiating element partially overlaps the operable band width of the radiating element.

Abstract: An antenna system can include an antenna radiating element configured for at least one of RF signal transmission or RF signal reception. The antenna radiating element can include a ground leg. The antenna radiating element can include a ground connection coupled to the ground leg and configured to couple the ground leg to ground. The ground connection can include one or more electromagnetically coupled regions. The one or more electromagnetically coupled regions can be configured to increase an electrical length of the ground connection relative to a conductor length of the ground connection.

Abstract: A radar system for a vehicle, having at least two transmission antennas, each for emitting a transmission signal into the surroundings of the vehicle, at least four reception antennas, each for acquiring a detection signal for detecting targets in the surrounding of the vehicle, and a processing device for determining the viewing angle, in order to assign phase information in the detection signals to at least one viewing angle for respective detected targets, such that a minimum ambiguous range of the reception antennas in a first direction is specific for the assignment to be ambiguous to more than one viewing angle, wherein all of the reception antennas are spaced apart from each other in the first direction by different distances such that only one of the distances corresponds to the minimum ambiguous range.

Abstract: Radiating elements include a conductive patch having first and second slots that each extend along a first axis and third and fourth slots that each extend along a second axis that is perpendicular to the first axis, a feed network that includes first through fourth feed lines, each feed line crossing a respective one of the first through fourth slots, and a conductive ring that at least partially surrounds the periphery of the conductive patch and that encloses each of the first through fourth slots.

Abstract: A radar system for a vehicle, having at least two transmission antennas, each for emitting a transmission signal into the surroundings of the vehicle, at least four reception antennas, each for acquiring a detection signal for detecting targets in the surrounding of the vehicle, and a processing device for determining the viewing angle, in order to assign phase information in the detection signals to at least one viewing angle for respective detected targets, such that a minimum ambiguous range of the reception antennas in a first direction is specific for the assignment to be ambiguous to more than one viewing angle, wherein all of the reception antennas are spaced apart from each other in the first direction by different distances such that only one of the distances corresponds to the minimum ambiguous range.

Abstract: Technologies directed to a radio frequency (RF) structure that provides an electrically insulating gap between a ground plane of a circuit board and a chassis at direct current (DC) and an electrical connection between the ground plane and the chassis at RF frequencies. One RF structure includes a first conductor electrically coupled to the ground plane and a second conductor electrically coupled to the chassis. A physical arrangement of a portion of the first conductor and a portion of the second conductor causes the RF structure to provide an electrically insulating gap between the ground plane and the chassis at DC and an electrical connection between the ground plane and the chassis at RF frequencies.

Abstract: A signal distribution system includes: a first signal divider arranged to generate a first output oscillating signal according to a first input oscillating signal; a second signal divider arranged to generate a second output oscillating signal according to the first input oscillating signal; a first transmitting channel coupled to the first signal divider and the second divider for transmitting the first input oscillating signal to the first signal divider and the second signal divider; and a second transmitting channel coupled to the first signal divider and the second divider for transmitting a second input oscillating signal to the first signal divider and the second signal divider; wherein the first input oscillating signal has a first frequency, the second input oscillating signal has a second frequency, and the second frequency is smaller than the first frequency.

Abstract: A hosted multi-reflector antenna system includes a primary reflector, a subreflector, an aperture, a feed structure and an anti-jam housing. The feed structure includes an electronically steered antenna (ESA). The subreflector directs a reflected beam between a primary reflector and an ESA, and the anti-jam housing encloses the subreflector and the ESA. The antenna system is thermo-elastically decoupled and thermally self-sufficient, accommodates thermal dissipation of the feed structure, and can maintain a precise antenna alignment.

Abstract: An antenna includes a substrate and a dipole antenna disposed on a surface of the substrate. The dipole antenna includes a first metal structure and a second metal structure arranged symmetrically with respect to each other. The first metal structure includes a head proximal to the second metal structure, and a tail distal from the second metal structure. A width of the first metal structure varies between the head and the tail.

Abstract: Novel directional antennas are disclosed which utilize plasmonic surfaces (PS) that include or present an array of closely-spaced parasitic antennas, which may be referred to herein as “parasitic arrays” or fractal plasmonic arrays (FPAs). These plasmonic surfaces represent improved parasitic directional antennas relative to prior techniques and apparatus. Substrates can be used which are transparent and/or translucent.

Abstract: An antenna system includes a first substrate, a plurality of chips and a waveguide antenna element based beam forming phased array that includes a plurality of radiating waveguide antenna cells for millimeter wave communication. Each radiating waveguide antenna cell includes a plurality of pins where a first pin is connected with a body of a corresponding radiating waveguide antenna cell and the body corresponds to ground for the pins. The first pin includes a first and a second current path, the first current path being longer than the second current path. A first end of the radiating waveguide antenna cells is mounted on the first substrate, where the plurality of chips are electrically connected with the plurality of pins and the ground of each of the plurality of radiating waveguide antenna cells to control beamforming through a second end of the plurality of radiating waveguide antenna cells for the communication.

Abstract: The present disclosure includes: an RFIC (110A) and an RFIC (110B) that are configured to respectively supply radio-frequency power to a first antenna group and a second antenna group; and a divider that divides a reference frequency signal input thereto and outputs the resulting first radio-frequency signals to the RFIC (110A) and the RFIC (110B). The divider is a Wilkinson-type first divider that is formed of a circuit system of a second impedance that is lower than a first impedance that is an impedance of signal transmission system into which the divider is inserted.

Abstract: An antenna system includes a first substrate, a plurality of chips and a waveguide antenna element based beam forming phased array that includes a plurality of radiating waveguide antenna cells for millimeter wave communication. Each radiating waveguide antenna cell includes a plurality of pins where a first pin is connected with a body of a corresponding radiating waveguide antenna cell and the body corresponds to ground for the pins. The first pin includes a first and a second current path, the first current path being longer than the second current path. A first end of the radiating waveguide antenna cells is mounted on the first substrate, where the plurality of chips are electrically connected with the plurality of pins and the ground of each of the plurality of radiating waveguide antenna cells to control beamforming through a second end of the plurality of radiating waveguide antenna cells for the communication.

Abstract: Methods and systems are provided herein for combining antenna signals based at least in part on the physical separation distance between antennas. A computing device includes a first antenna. The first the antenna is configured to receive a first signal. The first antenna is one of a plurality of antennas in the computing device. A second antenna is configured to receive a second signal. The second antenna has more physical separation distance from the first antenna relative to any other antenna within the computing device. A combiner within the computing device is configured to combine the first signal and the second signal based on the second antenna having more physical separation distance from the first antenna relative to any other antenna.

Abstract: An optical sensing device applicable to two dimensional electric field, includes sequentially connected input polarization maintaining fibers, a sensing unit, an output single mode fiber, a photodetector and a signal processing unit, the sensing unit includes a lithium niobate substrate; a first Y optical waveguide and two Mach Zehnder structure optical waveguides are arranged on the lithium niobate substrate; the input of the first Y optical waveguide is connected with the output of the laser source, the output is respectively connected to the inputs of the two Mach Zehnder structure optical waveguides; the outputs of the two Mach Zehnder structure optical waveguides are connected to the photodetector; dipole antenna is arranged at any single waveguide arm of each Mach Zehnder structure optical waveguide, the polarization directions of the two dipole antennas are in orthogonality with each other.

Abstract: A device is provided that includes a plurality of walls and at least one holding slot on a wall for temporarily holding the printed circuit board during assembly of the device at an angle with respect to the wall.

Abstract: An antenna (100) for an RFID reading apparatus having a plurality of single antennas (10) of the inverted-F type, wherein the single antennas (10) are arranged in a plane and are arranged tilted with respect to one another within the plane, and having a feed circuit (16) that is connected to the single antennas (10) to control the single antennas (10) to generate a circular polarization having a mutual phase offset corresponding to the tilt is provided. The antenna (100) in this respect has at least four single antennas (10a-d), the single antennas (10a-d) are arranged in a direction of rotation, and the antenna (100) has a common ground plane (20, 28) in parallel with the plane.

Abstract: An antenna assembly includes a curved printed circuit board (PCB) configured to mount around a curved surface. The curved PCB can include an outward-facing first side and an inward-facing second side with a plurality of antenna structures disposed on one of the first side and second side of the PCB. The plurality of antenna structures can be configured to provide directional radiation in at least one frequency band.

Abstract: Systems and methods providing wireless synchronization of wave arrays may include an antenna that receives a wireless injection signal and another antenna that radiates a locked wave signal corresponding to the injection signal. In some embodiments, these systems may also provide a low noise amplifier, voltage controlled oscillator (VCO), buffer amplifier(s), phase shifter, and/or multi-stage amplifier. In some embodiments, the injection signal may be provided on an even harmonic, and the intended transmission frequency signal is on an odd harmonic of the locked signal. The substrate thickness may be designed to radiate electromagnetic waves in odd harmonics of the locked signal. In yet another embodiment, polarization of a receiving antenna may be orthogonal to a transmitter antenna.

Abstract: The invention is directed to a method of synchronizing transmission between two nodes in a wireless network. The method comprises the steps of obtaining an expected interference profile for each node; and agreeing a synchronized transmission schedule between the nodes, where the expected interference profile of the or each node meets predetermined criteria.

Abstract: A planar antenna includes a substrate formed of a dielectric; a distributed constant line formed on a first surface of the substrate, the distributed constant line including a first end to which power is supplied and a second end that is an open end or is grounded; and at least one first resonator arranged on the first surface of the substrate and within a range in which the at least one first resonator is allowed to be electromagnetically coupled to the distributed constant line in a vicinity of any of nodal points of a standing wave of a current that flows through the distributed constant line in response to a radio wave having a certain design wavelength radiated from the distributed constant line or received by the distributed constant line.

Abstract: An omni-directional antenna module includes a plurality of vertically and horizontally polarized antenna elements arranged to provide 360° coverage around an antenna, and to eliminate nulls below the antenna. The antenna elements are arranged in parallel with respective orthogonal axes of a three-dimensional Cartesian coordinate system, with the centers of the antenna elements being arranged collinearly along the vertical or “Z” axis so that the radiation patterns of the individual orthogonally polarized dipoles do not interfere.

Abstract: A method of forming overlapping antenna subarrays includes forming one or more first-level subarrays by combing multiple elements. Each first-level subarray may have a phase center. One or more second-level subarrays may be formed by arranging a number of the first-level subarrays to form each first-level subarray. One or more third-level subarrays may be formed by arranging a number of the second-level subarrays to form each second-level subarray. The first-level, second-level, and third-level subarrays may include overlapping antenna subarrays. Each element may include an antenna element. Some of the first level, second-level, or third level subarrays may have an interlocking feature that allows interlocking of each subarray with another one of the same subarray. Arranging subarrays may include interlocking subarrays.

Abstract: Antenna arrays which can work simultaneously in various frequency bands thanks to the physical disposition of the elements which constitute them, and also the multiband behaviour of some elements situated strategically in the array. The configuration of the array is described based on the juxtaposition or interleaving of various conventional mono-band arrays working in the different bands of interest. In those positions in which elements of different multiband arrays come together, a multiband antenna is employed which covers the different working frequency bands. The advantages with respect to the classic configuration of using one array for each frequency band are: saving in cost of the global radiating system and its installation (one array replaces several), and its size and visual and environmental impact are reduced in the case of base stations and repeater stations for communication systems.

Abstract: An antenna array including a plurality of elements, the elements including at least one element of a first type and at least four elements of a second type wherein the element of the first type comprises part of two balanced feeds with two elements of the second type and the element of the first type is capacitively coupled to two further elements of the second type.

Abstract: An apparatus for synthetic imaging of an object is disclosed. The apparatus includes a plurality of transmitter elements spaced apart by a first distance in a first column and a plurality of receiver elements spaced apart by a second distance in a second column. The first distance and the second distance are different. The plurality of transmitter elements is a non-integer multiple of the plurality of receiver elements, and the plurality of receiver elements is a non-integer multiple of the plurality of transmitter elements.

Abstract: An antenna apparatus includes a first dielectric layer, a ground plane, a conductive line, a second dielectric layer, and a first conductive element and a second conductive element configured to be disposed on the second dielectric layer so that the first and the second conductive elements intersect the conductive line at first and second positions corresponding to first and second nodes of a standing wave of current flowing through the conductive line, respectively, wherein the first and the second conductive elements are bent or rounded toward a feeding point with respect to the first and the second positions in plan view, respectively, and wherein a first bent degree, a first rounded degree or a first length of the first conductive element is different from a second bent degree, a second rounded degree or a second length of the second conductive element.

Abstract: A two-element array antenna system includes a first antenna element and a second antenna element. A transmitting, receiving, and processing (TRP) system is coupled to the first and second antenna elements via, respectively, a single first transmission element and a single second transmission element. The first and second transmission elements have respective transmit-path and receive-path functionality. The TRP system is configured to determine an amplitude offset and phase offset associated with the transmit-path functionality of the first and second transmission elements, and, based on data obtained during the determination of amplitude offset and phase offset associated with the transmit-path functionality of the first and second transmission elements, determine an amplitude offset and phase offset associated with the receive-path functionality of the first and second transmission elements.

Abstract: An electromagnetic bandgap structure and a printed circuit board that solve a mixed signal problem are disclosed. In accordance with embodiments of the present invention, the electromagnetic bandgap structure includes a first metal layer; a first dielectric layer, stacked in the first metal layer; a second metal layer, stacked in the first dielectric layer, and having a holed formed at a position of the second dielectric layer; a second dielectric layer, stacked in the second metal layer; a metal plate, stacked in the second dielectric layer; a first via, penetrating the hole formed in the second metal layer and connecting the first metal layer and the metal plate; a third dielectric layer, stacked in the metal plate and the second dielectric layer; a third metal layer, stacked in the third dielectric layer; and a second via, connecting the second metal layer to the third metal layer.

Abstract: A two-dimensional (2-D) beam steerable phased array antenna is presented comprising a continuously electronically steerable material including a tunable material or a variable dielectric material, preferred a liquid crystal material. A compact antenna architecture including a patch antenna array, tunable phase shifters, a feed network and a bias network is proposed. Similar to the LC display, the proposed antenna is fabricated by using automated manufacturing techniques and therefore the fabrication costs are reduced considerably.

Abstract: In one embodiment, an active array antenna device includes: M (M?2) bandpass filters to filter signals received by M antenna elements; M low noise amplifiers to amplify the filtered received signals; M distributors to distribute respective of the M amplified signals into N (N?2) distributed signals; M sets of N phase shifters provided for respective of the M distributors to shift phases of the N distributed signals; M sets of N attenuators to attenuate N phase-shift signals; N beam synthesis circuits provided for N sets of the M attenuators to synthesize a beam by summing attenuator outputs from the M attenuators corresponding to the M distributors; a heat insulating container accommodating the low noise amplifiers and the receiving filters and formed of a superconductor material; and a cooler to cool the receiving filters and the low noise amplifiers to make the receiving filters in a superconducting state.

Abstract: The subject disclosure relates to solar energy collection and use in communications systems and to enhancements thereof. In an aspect, dual function antennas are disclosed that can simultaneously function as an antenna and as a solar energy collection system. In further aspects, disclosed embodiments can focus incident solar radiation to increase output voltage of conventional solar cells. Measured and simulated results demonstrate various aspects of the subject disclosure.

Abstract: A compact patch antenna array for mobile terminal applications comprising: a plurality of radiators mounted on one surface of a dielectric, with a ground plane being mounted on the other side of the dielectric. Beneath the ground plane, another dielectric with feeding network is placed. Other embodiments are described and shown in FIG. 2.

Abstract: The present invention provides, as one aspect, a microstrip array antenna including a dielectric substrate, on a back face of which a conductive grounding plate is formed, and a strip conductor formed on the dielectric substrate. The strip conductor comprises a feeding strip line which extends in an extension direction, and at least two radiation antenna elements. At least one of the antenna elements is connected with one side of the strip line, and at least one of the antenna elements is connected with the other side of the strip line. The longitudinal directions of the antenna elements are parallel to each other and are at an angle of other than 90° with respect to the extension direction. The strip line has a bending shape and fully extends in the extension direction so that the antenna elements are connected with the strip line at the same angle.

Abstract: An RF transceiver front-end includes receiver and transmitter front-ends. The receiver front-end includes 1st and 2nd antennas, a ninety degree phase shift module and an LNA module. The 1st and 2nd antennas receive inbound RF signals and provide a first directional circular polarization. The ninety degree phase shift module phase shifts the RF signals received by the 2nd antenna. The LNA module amplifies the RF signals received by the 1st antenna and the shifted RF signals. The transmitter front-end includes a PA module and 3rd and 4th antennas, which provide a second directional circular polarization. The PA module amplifies outbound RF signals to produce amplified outbound RF signals and amplified orthogonal outbound RF signals. The 3rd antenna transmits the amplified outbound RF signals and the 4th antenna transmits the amplified orthogonal outbound RF signals.

Abstract: A metamaterial for a radio frequency communications apparatus is disclosed. The metamaterial can comprise a flex circuit and an array of circuit elements mounted on the flex circuit. Each of the circuit elements can comprise a conductive trace and at least one hybrid component electrically coupled to the conductive trace.

Abstract: A ground based avian radar receive antenna is implemented using a vertically oriented offset parabolic cylindrical antenna. The desired azimuth beamwidth is determined by the width of the parabolic cylinder reflector surface and the desired elevation beamwidth by the height of the parabolic cylinder reflector surface. A vertical array of antenna elements is mounted along the vertical focal line to provide electronic scanning in elevation. Low sidelobe levels are obtained using tapered antenna element illumination. Low cost modular construction with high reflector accuracy is obtained by attaching a thin metal reflector to thin ribs machined or stamped in the shape of the parabolic cylinder reflector surface. The antenna is enclosed in a radome and mechanically rotated 360 degrees in azimuth.

Abstract: In an exemplary embodiment, a modular phased array comprises a ground plane with a first side and a second side, where the ground plane has a slot. The modular phased array also comprises a patch antenna located on the first side of the ground plane, and a feed network located on the second side of the ground plane. In an exemplary embodiment, the ground plane isolates the patch antenna from the feed network. The feed network includes a compacted hybrid with two output ports. In an exemplary embodiment, the ground plane comprises slots that are nonorthogonal and nonparallel to the two output ports of the feed network. In another exemplary embodiment, the distance from the center of the patch antenna to the farthest output port of the two output ports of the compacted hybrid is ½ wavelengths or less.

Abstract: In an antenna array, a metal layer is used for covering a block mapped by micro-strips, which are disposed on an obverse side of a base plate, on a reverse side of the base plate, so as to concentrating energy of radio signals emitted from radiator sets on a predetermined direction. The base plate and elements loaded by the base plate are fabricated according to designed specifications, so as to enhance the concentration of energy of the radio signals on the predetermined direction.

Abstract: The present invention relates to a system for changing the radiation pattern shape of an antenna array during electrical tilting. The antenna array has multiple antenna elements, and the system comprises a phase-shifting device provided with a primary port configured to receive a transmit signal, and multiple secondary ports configured to provide phase shifted output signals to each antenna element. The system further comprises a phase-taper device that changes phase taper over the antenna elements, and thus the beam shape, with tilt angle ?. The invention is adapted for use in down-link as well as up-link within a wireless communication system.

Abstract: Apparatus and methods are provided for integrally packaging antennas with semiconductor IC (integrated circuit) chips to provide highly-integrated and high-performance radio/wireless communications systems for millimeter wave applications including, e.g., voice communication, data communication, and radar applications. For example, wireless communication modules are constructed with IC chips having receiver/transmitter/transceiver integrated circuits and planar antennas that are integrally constructed from BEOL (back end of line) metallization structures of the IC chip.

Abstract: An artificial medium includes: a dielectric layer having a front surface and a back surface; a plurality of first grid lines respectively formed on the front surface and the back surface and extending in a first direction and a plurality of second grid lines extending in a second direction different from the first direction; and electrically conductive elements respectively formed on the front surface and the back surface of the dielectric layer and located in areas where the first grid lines intersect the second grid lines, wherein when an electromagnetic wave propagated in the direction of the thickness of the dielectric layer is incident, a current excited by the electromagnetic wave is increased in a prescribed operating frequency and a current loop is formed in a plane parallel to the direction of the thickness.

Abstract: Measurement opportunities are provided to a wireless transmit/receive unit (WTRU) operating with a switched beam antenna in a CDMA wireless communication system. The switched beam antenna is a smart antenna generating a plurality of directional beams and an omni-directional beam. The bursty nature of packet data transmission generates periods of inactivity or low traffic during a call. The WTRU switches to antenna beams other than the selected antenna beam for receiving and measuring signals during these periods of inactivity or low traffic. Moreover, if the network has knowledge of the fact the WTRU is operating using a switched beam antenna, the network can use this information when making decisions on channel allocations, thus providing frequent measurement opportunities to the WTRU in order to support the switched beam antenna operation.

Abstract: A microwave antenna having an electrically nonconductive substrate with a top and bottom side. A radiator array having a plurality of rows of radiator patches is disposed on the top side of the substrate while an input feed line and power divider network are disposed on the bottom side of the substrate. The power divider network includes a plurality of ends wherein each end is adapted for electrical connection through a via formed through the substrate to the end of its associated row in the radiator array. An electrically conductive layer is disposed over a portion of the top side of the substrate so that the electrically conductive layer overlies the power divider network and shields the power divider network from the radiator array.

Abstract: An RF transceiver front-end includes receiver and transmitter front-ends. The receiver front-end includes 1st and 2nd antennas, a ninety degree phase shift module and an LNA module. The 1st and 2nd antennas receive inbound RF signals and provide a first directional circular polarization. The ninety degree phase shift module phase shifts the RF signals received by the 2nd antenna. The LNA module amplifies the RF signals received by the 1st antenna and the shifted RF signals. The transmitter front-end includes a PA module and 3rd and 4th antennas, which provide a second directional circular polarization. The PA module amplifies outbound RF signals to produce amplified outbound RF signals and amplified orthogonal outbound RF signals. The 3rd antenna transmits the amplified outbound RF signals and the 4th antenna transmits the amplified orthogonal outbound RF signals.

Abstract: To provide an array antenna which has both excellent directional characteristics and axial ratio characteristics without changing a substrate or dimensions, even when a frequency is changed. A first sequential arrangement section, in which antennas are sequentially arranged from the left end section to the center section, and a second sequential arrangement section, in which antennas are sequentially arranged from the right end section to the center section, are symmetrically arranged.

Abstract: The present invention relates to an antenna arrangement comprising a first and third set of antenna elements, being arranged as a first and third column and aligned along a first and third symmetry axis, respectively, each column comprising elements being operative in a first frequency band (f1) and elements being operative in a second frequency band (f2). The antenna arrangement further comprises a second set of antenna elements, being arranged as a second intermediate column along a second symmetry axis, said second symmetry axis being parallel to said first and third symmetry axes, and being operative in said second frequency band (f2), wherein the ratio of said second center frequency (f2) to said first center frequency (f1) is in the range 1.5 to 3. The distance between said first and third symmetry axes is less than or equal to 0.

Abstract: A radar system having orthogonal antenna apertures is disclosed. The invention further relates to an antenna system wherein the orthogonal apertures comprise at least one transmit aperture and at least one receive aperture. The cross-product of the transmit and receive apertures provides a narrow spot beam and resulting high resolution image. An embodiment of the invention discloses orthogonal linear arrays, comprising at least one electronically scanned transmit linear array and at least one electronically scanned receive linear array. The design of this orthogonal linear array system produces comparable performance, clutter and sidelobe structure at a fraction of the cost of conventional 2D filled array antenna systems.

Abstract: There is provided a method comprising: determining a phase difference between at least two antenna units of a distributed antenna system on the basis of at least one pilot signal received from at least one of a plurality of antenna units; and transmitting phase correction commands to a common base station of the plurality of antenna units on the basis of the determined phase difference in order to synchronize carrier phases between at least two antenna units of the distributed antenna system.