Product Info

JODY-W2 - Application Note
UBX-20053581 - TBD Contents Page 4 of 11
1 Scope
This document defines the essential specifications necessary to implement the JODY-W2 antenna
reference designs as used in certification. It is part of the equipment certification application issued
to FCC and ISED. The information contained herein and its references should be sufficient to guide a
skilled person to implement the design on a host carrier. It will provide the designer with PCB layout
details and expected performance specifications.
This document supports a connector-based design for the use of external antennas (one for each
antenna pin of the module).
2 General description and requirements
JODY-W2 series modules provide two RF interfaces for connecting external antennas. The antenna
ports ANT0 and ANT1 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 impedance matching along the RF
path. A bad termination of the pin may result in poor performance or even damage the RF section of
the module.
For optimal performance in multiradio mode, the isolation between the antennas shall target the
requirements as specified in Table 1 and Table 2 in order to ensure good performance.
Item Requirements Remarks
Impedance
50  nominal characteristic
impedance
The impedance of the antenna RF connection must match
the 50  impedance of the antenna pins.
Frequency range 2400 - 2500 MHz
5150 - 5850 MHz
For 802.11b/g/n and Bluetooth.
For 802.11a/n/ac.
Return loss
S11 < -10 dB (VSWR < 2:1)
recommended
S11 < -6 dB (VSWR < 3:1) acceptable
The return loss or the S11, as the VSWR, refers to the
amount of reflected power, measuring how well the primary
antenna RF connection matches the 50  characteristic
impedance of antenna pins.
The impedance of the antenna termination must match as
much as possible the 50  nominal impedance of antenna
pins over the operating frequency range, to maximize the
amount of power transferred to the antenna.
Efficiency > -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
The radiation efficiency is the ratio of the radiated power to
the power delivered to antenna input: the efficiency is a
measure of how well an antenna receives or transmits.
Maximum gain
The maximum antenna gain must not exceed the value
specified in type approval documentation to comply with
regulatory agencies radiation exposure limits.
Table 1: Summary of antenna interface requirements
Item Requirements Remarks
Isolation
(in-band)
S
21
> 25 dB recommended
S
21
> 20 dB acceptable
The antenna to antenna isolation is the S
21
parameter
between the two antennas in the band of operation.
Isolation
(out-of-band)
S
21
> 35 dB recommended
S
21
> 30 dB acceptable
Out-of-band isolation is evaluated in the band of the
aggressor to ensure that the transmitting signal from the
other radio is sufficiently attenuated by the receiving
antenna to avoid saturation and intermodulation effect at
the receiver’s port.
Envelope correlation
Coefficient (ECC)
ECC < 0.1 recommended
ECC < 0.5 acceptable
The ECC parameter correlates the far field parameters
between antennas in the same system. A low ECC
parameter is fundamental to improve performance in
MIMO-based systems.
Table 2: Summary of MIMO and Wi-Fi/Bluetooth coexistence requirements. MIMO is not applicable for JODY-W2.