1-22 (No.RA054<Rev.001>)
2.4.9.1
Bluetooth Circuit
TX/RX frequency is 2400-2483.5MHz (79ch Hopping, 2402-2480MHz, 1MHz step). Transmitting power is +2dBm at Bluetooth
antenna input.
Using the printed antenna with Bluetooth, and connected to the Bluetooth/GPS IC (IC5) through the saw filter (L11).
Frequency configuration for Bluetooth is following:
There are two LO modes: 2X and Offset LO (OSLO). 2X where LO is 2*RF_FREQ (e.g. when transmitting at 2441MHz it is at
4882MHz). OSLO where LO is at (2/3)*RF_FREQ (e.g. when transmitting at 2441MHz it is at 1627.333MHz).
In RX the 2X is always used.
In GFSK TX if power is >10dBm then OSLO is used
In EDR2 TX if power is >-12dBm then OSLO is used
In EDR3 TX if power is >-12dBm then OSLO is used
Otherwise 2X is used for TX as well.
2.4.9.2
GPS Circuit
The GPS RF signal is received with the active antenna, and connected to the Bluetooth/GPS IC (IC5) through the terminal (CN5) and
saw filter (L9).
The output is passed to pin L2 of the GPS IC. The input match for pin L2 comprises of C38, C36 and L7. The control and data lines
for the GPS IC are GPS_PA_EN, BTFM_nSHUTDOWN, GPS_TX and GPS_RX. GPS_TX and GPS_RX are shared with Bluetooth
data line.
Frequency configuration for GPS is following:
Lo is GPS: 1571.324MHz
Fig.6 GPS Circuit
BPF
GPS
antenna
TCXO
19.2MHz
MPU/DSP
IC404
1.8V
3.3V
GPS_LNA_IN(L2)
TCXO_CLK_LV(F1)
BT_HCI_UART_TX(A4)
BT_HCI_UART_RX(B5)
RTC_CLK(H9)
OSCILLATOR
32.768kHz
BTFM_nSHUTDOWN(A6)
GPS_PA_EN(G3)
VBAT1(A2)
Level
Conversion
TCXO_LDO_IN(H1)
VDDS
GPS TX
GPS_RX
BT
antenna
BT_RF
BT/GPS IC
Antenna
connector
BPF
GPS ANT ALM
GPS ANT PWR
GPS
Antenna
Detect
3.3V
33GPS
33BT
18BT
Summary of Contents for NX-3720
Page 188: ...MEMO No RA054 Rev 001 2 20 ...
