JODY-W1 antenna reference design
UBX-18017767
Page 2 of 3
Item
Requirements
Remarks
Impedance
50
nominal characteristic
impedance
The impedance of the antenna RF connection must match
the 50
impedance of Antenna pins.
Frequency Range
2400 - 2500 MHz
5150 - 5850 MHz
For 802.11b/g/n and Bluetooth.
For 802.11a/n/ac.
Return Loss
S
11
< -10 dB (VSWR < 2:1)
recommended
S
11
< -6 dB (VSWR < 3:1) acceptable
The Return loss or the S
11
, 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 2: 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 3: Summary of MIMO and Wi-Fi/Bluetooth coexistence requirements
4
Reference design of RF path
The reference design of the 50
Ω
path to connect the modules antenna pins with a SMA connector
is displayed in Figure 1. The specification can be found in Table 4. The two coplanar ground planes
beside the signal trace should be connected to the lower ground plane using vias (illustrated in
Figure 2). It is recommended that this vias are placed with a maximum distance of 0.5 mm to the
coplanar ground edge and a maximum pitch of 2 mm. The top side should be coated with generic
LPI solder stop mask. The antenna traces should have a minimum distance of 20 mm, preferably
more, to ensure the required antenna to antenna isolation.
The SMA connector is used to mount an antenna. For Bluetooth and Wi-Fi operation in the 2.4 GHz
band and Wi-Fi operation in the 5 GHz band, the module has been tested and approved for use with
antennas up to 2 dBi antenna gain.
