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Page 17 of 35

4.6 Range of BLE121LR

Module

Typical

TXP

Sensitivity

Direction

Antenna

Attenuation

Link Budget

Calculated

Range

Tested

Range

BLE121LR

8 dBm

-98 dBm

Front

-3 dB

100 dB

470m

450m

BLE121LR

8 dBm

-98 dBm

Back

-7 dB

92 dB

300m

300m

BLE121LR

8 dBm

-98 dBm

Side

-5 dB

96 dB

370m

340m

-120

-110

-100

-90

-80

-70

-60

-50

-40

10

100

1000

Plane Earth Loss

Free Space Loss

Range (m)

14.7 mm

13.7 mm

Figure 12: Range of BLE121LR vs BLE121LR when antennas are 1.5m above GND

The range of BLE121LR is dependent on the mother board layout, height of the antennas above GND and

any obstacles within the RF path or near the RF path (multipath propagation). See Figure 25 how the layout

impacts to the range of BLE121LR.

In an open field the received power is a sum of the line-of-sight wave and the ground-reflected wave.

Depending on the phase of the ground-reflected wave, it either amplifies or attenuates the total received

power. Figure 14 shows how the antenna height from ground impacts to the RF path loss and range in an

open field.

RF power propagates in fr

ee space within a virtual “pipe” which can be defined by so called Fresnel ellipsoid.

Any obstacles within the area of this “pipe” will attenuate the RF power and thus decrease the actual range of

the link.

The radius of the “pipe” can be approximated by

12





=

D

R

Where R is the radius, D is the distance between the antennas and lambda is the wave length (12.2 cm).