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3.DETAILED DESCRIPTION
3.1 Overview
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The CMM200 is a 2x8-element dual-polarization antenna sub-array module which can be used to
construct the passive radiator section of a Massive MIMO system capable of operating in the 5-
6GHz band. The CMM200 will maintain a constant spacing between elements when attached to
other CMM200 modules using its proprietary threadless fastening scheme. Each module can be
mated with another module on either the long or short side. This property allows for a large
number of array configurations to be easily realized.
Upon mating, conductive O-rings located around the perimeter of the modules near the antenna
end make intimate contact with O-rings from the mating module, implementing a large ground
plane automatically as a result of fastening the two modules together. This ground plane can be
extended with the ground plane extenstions (GPEs) included with the research kit, which have the
same fastening pattern and dimensions as the modules. The GPEs have 4 threaded bosses evenly
spaced at twice the lattice spacing constant (2x28mm=56mm) which allows for fastening to
infrastructure.
The ground plane formation due to making up a larger array supports a uniform endfire pattern
for each radiating element, since the elements are dual-polarization patches having 3dB-
beamwidth of ±45°. This arrangement allows for a high front-to-back ratio of at least 15dB,
allowing for frequency reuse in other sectors.
These salient features allow for a large number of possible array configurations and field scenarios
to be implemented in terms of array configuration, site location and the resultant implications on
beamforming and propagation properties.
The CMM200 passive version has 34 SMA connectors on the back side of the module for each of
the 32 antenna ports (16 horizontal, 16 vertical), as well as 2 connectors for calibration and
calibration daisy chaining. The connectors can be delivered terminated with cable upon request
for ease of use.
The CAL port has a 28-35dB coupling and network loss between itself and each of the 32
addressable radiating element ports using a meandering coupling network. The CAL and CAL_DSY
ports allow for the transceivers (which are attached to each SMA port) for each antenna to be
coupled to a reference transceiver (on the CAL port) for TDD reciprocity calibration. This network
does not increase coupling or crosstalk between elements enough to be any system impairment.
The CAL_DSY port has a 3dB insertion loss relative to the CAL port and is used to daisy chain other
modules.
DSP-17-08-005/A/JD
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