[[TOC(Hardware, Hardware/lDirAnt*, depth=3)]]

== Antennas ==

In addition to chip antennas on various USB attached wireless devices, three types of external antennas are attached to various RF devices on the nodes. 
 
=== !WiFi Antennas ===

Most of the internal !WiFi devices are attached to dual band (2.4/5 GHz), blade style omni-directional antennas shown in Figure 1. These are mounted at the end of the two rods extending at the 45 degree angle downwards from the node harness as shown in Figure 2 with the distance between the two antenna rods (i.e. the two internal !WiFi devices) of 26 inches.

 || [[Image(Ant1.png, width=400, caption="Figure 1")]] || [[Image(NodeWiFi.png, width=400)]] ||

These antennas have a [attachment:Ant1.pdf typical donut-shaped shape radiation pattern] with an average gain of 2 dBi (@ 2.4 GHz) and 4 dBi (@ 5GHz).  

=== Multi-standard Antennas ===

A number of SDR units in the grid use [attachment:Ant2.pdf Taoglas TG-25-8113 multi-band antennas] covering most of the !WiFi and 4G bands. They are mounted on a square plate 12 inches apart (in the horizontal plane) as shown in Figure 4. To minimize antenna correlation, the corner positions are used with the TX (and RX) of each RF chain on opposite diagonal corners.

 Top-down view of multi-band antenna panel:
 
 || [[Image(Ant2.png, width=400)]] || [[Image(MountingPlate.png, width=400)]] ||


 Antenna locations on square plate relative to USRP:
 ||||=''Front of USRP''=||
 || RFB RX2 || RFA TX/RX ||
 || RFB TX/RX || RFA RX2 ||


=== Massive-MIMO Antennas ===

The top of each Massive-MIMO mini-rack is populated with a horizontal array of 32 [attachment:APAMSJ-137.pdf antennas]. They are mounted on a rectangular plate with a 2 inch spaced grid pattern. See table below for antenna location to USRP mapping.

Example antenna configuration (top-down view) for node23-1 through node23-8:
 ||||||||||||||||=''Back of Massive-MIMO mini-rack''=||
 ||23-1 RF A TX/RX||23-1 RF A RX2||23-1 RF B TX/RX||23-1 RF B RX2||23-2 RF A TX/RX||23-2 RF A RX2||23-2 RF B TX/RX||23-2 RF B RX2||
 ||23-3 RF A RX2||23-3 RF A TX/RX||23-3 RF B RX2||23-3 RF B TX/RX||23-4 RF A RX2||23-4 RF A TX/RX||23-4 RF B RX2||23-4 RF B TX/RX||
 ||23-5 RF A TX/RX||23-5 RF A RX2||23-5 RF B TX/RX||23-5 RF B RX2||23-6 RF A TX/RX||23-6 RF A RX2||23-6 RF B TX/RX||23-6 RF B RX2||
 ||23-7 RF A RX2||23-7 RF A TX/RX||23-7 RF B RX2||23-7 RF B TX/RX||23-8 RF A RX2||23-8 RF A TX/RX||23-8 RF B RX2||23-8 RF B TX/RX||
 ||||||||||||||||=''Front of Massive-MIMO mini-rack''=||

=== Electronically Steerable Antennas ===

4 nodes with USRP X310 devices in addition to standard antennas (WiFI for two internal devices and multi-standard paddle antennas) are equipped with a electronically steerable antenna and a block of RF switches facilitating antenna selection.

The 2.4-2.5 GHz [http://www.fidelity-comtech.com/wp-content/uploads/SpecSheet_FCI-3740.pdf Fidelity Comtech FCI-3740 Phased Array] device actually comprises of: 
 * Directional antenna with 14.5 dBi of gain and 49 electronically selectable antenna patterns 
 * Omni-directional 9 dBi antenna
 * Embedded GPS
The antenna is managed either directly by the USRP via a fast GPIO-to-RS485 link or through OMF services which facilitate the selection of power state and pattern selection.

==== Antenna Switching Hardware ====

The antenna switching hardware is shown in Figure 6. It consists of: bank of RF switches, RS-485 drivers and ''Raspberry PI'' as an embedded controlled. This hardware enables remote antenna selection and steering. 

 ||  [[Image(DirAnt-1.0.jpg, width=400)]]  ||  [[Image(ESA.jpg, width=400)]]  ||

The bank of switches is used to route both nodal !WiFi and X310 antenna feeds to either regular antennas or to directional or omni-directional antennas on FCI-3740. The table below shows switch states and corresponding antenna selections (blanks indicate the particular switch state does not matter for ''the particular configuration'').

 ||'''Configuration'''||'''SW 1'''||'''SW 2'''||'''SW 3'''||'''SW 4'''||
 ||Node Wifi 0 -> standard antenna||RF 1|| || || ||
 ||Node Wifi 0 -> directional (FCI antenna)||RF 2||RF 1|| || ||
 ||USRP RF A -> standard antenna|| || ||RF 1|| ||
 ||USRP RF A -> directional (FCI antenna)|| ||RF 2||RF 2|| ||
 ||USRP RF B -> standard antenna|| || || ||RF 1||
 ||USRP RF B -> omni (FCI antenna)|| || || ||RF 2||

The embedded controller is used to provide IP/HTTP based remote management. [wiki:Software/eAM/sDA Directional Antenna AM] Service is used by experimenters to manage the antenna selection and steering.