MIMO antenna assembly having stacked structure
Provided is a multiple-input multiple-output (MIMO) antenna having a lightweight stacked structure. According to one aspect of the present invention, there is provided a MIMO antenna assembly having a lightweight stacked structure, in which a calibration network, which was provided between antenna elements and filters in the related art, is provided on one printed circuit board (PCB), together with a power amplifier and a digital circuit, and filters are closely coupled to the bottom of the PCB on which the feeding network is provided. The present invention employs a strategy in which an antenna assembly is reduced to a compact size while managing phase deviation caused due to filters at an acceptable level. According to another aspect of the present invention, there is provided a calibration method, in which transmission/reception (TX/RX) calibration may be performed by a single calibration hardware component of a MIMO antenna operated by a time division duplex (TDD) scheme and may be performed in real time during the operation of the MIMO antenna, and the MIMO antenna employing the calibration method.
1. A multiple-input multiple-output (MIMO) antenna system comprising:
a radome;
a housing including a heat sink on a rear side thereof, and
an antenna assembly having a stacked structure and embedded between the radome and the housing,
wherein the antenna assembly comprises:
a first printed circuit board (PCB) on which a feeding network is provided;
a plurality of antenna elements provided on an upper surface of the first PCB opposite the radome, and electrically connected to the feeding network;
a second PCB arranged opposite the housing, the second PCB including:
a plurality of transmitting/receiving circuits;
a digital circuit being configured to perform digital processing on a baseband signal and electrically connected to the plurality of transmitting/receiving circuits;
a calibration circuits with a plurality of switches connected in a tree structure; and
a plurality of directional couplers; and
a filter assembly disposed between the first PCB and the second PCB, the filter assembly including a plurality of band-pass filters electrically connected to the feeding network and electrically connected to the plurality of transmitting/receiving circuits, and
wherein the plurality of directional couplers are coupled at nodes connecting the plurality of transmitting/receiving circuits with the plurality of band-pass filters and are electrically connected to the calibration circuit without radio-frequency (RF) cabling to form calibration paths, and
wherein a filter body of each of the plurality of band-pass filters is attached to the first PCB, and a first port of each of the plurality of band-pass filters is directly connected to the feeding network without radio-frequency (RF) cabling.
2. The MIMO antenna system of claim 1 , wherein a plurality of through-holes electrically connected to the feeding network are further provided in the first PCB,
the first port of each of the plurality of band-pass filters comprises a conductive pin extending from an internal cavity and protruding from an upper surface of the band-pass filter, and
the filter body of each of the plurality of band-pass filters is fastened to the first PCB such that a portion of the conductive pin is inserted into one of the plurality of through-holes of the first PCB.
3. The MIMO antenna system of claim 1 , wherein a plurality of contact pads connected to the feeding network are provided on the first PCB,
the first port of each of the plurality of band-pass filters comprises a conductive plunger electrically connected to an internal cavity and protruding from an upper surface of the band-pass filter, and
the filter body of each of the plurality of band-pass filters is fastened to the first PCB such that a portion of the conductive plunger is in contact with one of the plurality of contact pads on the first PCB.
4. The MIMO antenna system of claim 1 , wherein a plurality of contact pads connected to the feeding network are provided on the first PCB,
the first port of each of the plurality of band-pass filters comprises:
a conductive pin extending from an internal cavity and protruding from an upper surface of the band-pass filter; and
a conductive rod fixed on an end of the conductive pin in a vertical direction, and
the filter body of each of the plurality of band-pass filters is fastened to the first PCB such that a portion of the conductive rod is in contact with one of the plurality of contact pads on the first PCB.
5. The MIMO antenna system of claim 1 , wherein, in the filter assembly, the plurality of band-pass filters are assembled in a line to a push bar fastened to the second PCB.
6. The MIMO antenna system of claim 5 , wherein the push bar fastened to the second PCB is configured to apply uniform pressure to the plurality of band-bass filters such that the plurality of band-pass filters are coupled to the second PCB by a uniform force.
7. The MIMO antenna system of claim 1 , wherein each of the plurality of band-pass filters comprises a second port configured to be directly connected to one of the transmitting/receiving circuits without RF cabling.
8. The MIMO antenna system of claim 7 , wherein a plurality of RF sockets connected to the plurality of transmitting/receiving circuits are mounted on an upper surface of the second PCB,
the second port of each of the plurality of band-pass filters comprises:
a protruding part protruding from a lower surface of the band-pass filter and including a groove in a center thereof, wherein one of the plurality of RF sockets is inserted into the groove; and
a conductive pin extending from an internal cavity and passing through the groove of the protruding part, and
each of the plurality of band-pass filters is coupled to the second PCB such that a portion of the conductive pin is inserted into a groove formed in one of the plurality of RF sockets.
9. The MIMO antenna system of claim 7 , wherein a plurality of structures each including a contact pad electrically connected to one of the plurality of transmitting/receiving circuits are mounted on an upper surface of the second PCB,
the second port of each of the plurality of band-pass filters comprises a conductive plunger extending from an internal cavity and protruding from a lower surface of the band-pass filter, and
the filter body of each of the plurality of band-pass filters is coupled to the second PCB such that a portion of the conductive plunger is in contact with one of the plurality of contact pads.
10. The MIMO antenna system of claim 7 , wherein a plurality of structures each including a contact pad electrically connected to one of the plurality of transmitting/receiving circuits are mounted on an upper surface of the second PCB,
the second port of each of the plurality of band-pass filters comprises:
a conductive pin extending from an internal cavity and protruding from a lower surface of the band-pass filter; and
a conductive rod fixed on an end of the conductive pin in a vertical direction, and
the filter body of each of the plurality of band-pass filters is coupled to the first PCB such that a portion of the conductive rod is in contact with the contact pad.
11. The MIMO antenna system of claim 1 , wherein at least one ground plane is provided on the first PCB, the at least one ground plane functioning as a reflector for a plurality of antenna elements.
12. A multiple-input multiple-output (MIMO) antenna assembly having a stacked structure, comprising:
a first printed circuit board (PCB) on which a feeding network is provided;
a plurality of antenna elements provided on an upper surface of the first PCB and connected to the feeding network;
a second disposed under the first PCB,
the second PCB comprising:
a plurality of transmitting/receiving circuits;
a digital circuit connected to the plurality of transmitting/receiving circuits and configured to perform digital processing on a baseband signal;
a calibration circuit with a plurality of switches connected in a tree structure; and
a plurality of directional couplers; and
a filter assembly disposed between the first PCB and the second PCB, the filter assembly including a plurality of band-pass filters electrically connected to the feeding network and electrically connected to the plurality of transmitting and receiving circuits,
wherein the plurality of directional couplers are coupled at nodes connecting the plurality of transmitting/receiving circuits with the plurality of band-pass filters and are electrically connected to the calibration circuit without radio-frequency (RF) cabling to form calibration paths, and
wherein a first port of each of the plurality of band-pass filters is directly coupled to the feeding network without radio-frequency (RF) cabling, and a filter body of each of the plurality of band-pass filters is attached to the first PCB.
13. The MIMO antenna assembly of claim 12 , wherein each of the plurality of band-pass filters comprises a second port directed connected to one of the plurality of transmitting/receiving circuits without radio-frequency (RF) cabling.