TOBY-L1 and MPCI-L1 series - System Integration Manual
UBX-13001482 - R04
Advance Information
Design-in
Page 49 of 90
2.4
Antenna interface
TOBY-L1 and MPCI-L1 series modules provide two RF interfaces for connecting the external antennas:
•
The
ANT1
port represents the primary RF input/output for transmission and reception of the LTE RF signals.
•
The
ANT2
port represents the secondary RF input for the reception of the LTE RF signals for MIMO 2 x 2.
Both the
ANT1
and the
ANT2
port have a nominal characteristic impedance of 50
Ω
and must be connected to
the related antenna through a 50
Ω
transmission line to allow proper transmission / reception of RF signals.
Two antennas (one connected to
ANT1
port and one connected to
ANT2
port) must be used to support
the Down-Link MIMO 2 x 2 radio technology. This is a mandatory feature for LTE category 3 User
Equipments (up to 100 Mb/s Down-Link data rate) designed to operate on Verizon Wireless LTE 3GPP
Band 4 / 13 network.
2.4.1
Antenna RF interfaces (ANT1 / ANT2)
2.4.1.1
General guidelines for antenna selection and design
The LTE antenna is the most critical component to be evaluated. Designers must take care of the antennas from
all perspective at the very start of the design phase when the physical dimensions of the application board are
under analysis/decision, since the RF compliance of the device integrating TOBY-L1 and MPCI-L1 series module
with all the applicable required certification schemes depends on antennas radiating performance.
LTE antennas are typically available in the types of linear monopole or PCB antennas such as patches or ceramic
SMT elements.
•
External antennas (e.g. linear monopole)
o
External antennas basically do not imply physical restriction to the design of the PCB where the
TOBY-L1 and MPCI-L1 series module is mounted.
o
The radiation performance mainly depends on the antennas. It is required to select antennas with
optimal radiating performance in the operating bands.
o
RF cables should be carefully selected with minimum insertion losses. Additional insertion loss will
be introduced by low quality or long cable. Large insertion loss reduces radiation performance.
o
A high quality 50
Ω
RF connector provides proper PCB-to-RF-cable transition. It is recommended to
strictly follow the layout guidelines provided by the connector manufacturer.
•
Integrated antennas (e.g. patch-like antennas):
o
Internal integrated antennas imply physical restriction to the design of the PCB:
Integrated antenna excites RF currents on its counterpoise, typically the PCB ground plane of the
device that becomes part of the antenna: its dimension defines the minimum frequency that can be
radiated. Therefore, the ground plane can be reduced down to a minimum size that should be
similar to the quarter of the wavelength of the minimum frequency that has to be radiated, given
that the orientation of the ground plane related to the antenna element must be considered.
The isolation between the primary and the secondary antennas has to be as high as possible and
the correlation between the 3D radiation patterns of the two antennas has to be as low as possible.
In general, a separation of at least a quarter wavelength between the two antennas is required to
achieve a good isolation and low pattern correlation.
As numerical example, the physical restriction to the PCB design can be considered as following:
Frequency = 750 MHz
Wavelength = 40 cm
Minimum GND plane size = 10 cm
