S1M8660A Datasheet, PDF (15/32 Pages) Samsung semiconductor – RX IF / BBA WITH GPS

RX IF/BBA WITH GPS
S1M8660A (Preliminary)
GPS Rx Signal Path
The difference of the S1M8660A from the S1M8656A is that S1M8660A provides GPS receiving operation.
While GPS receiving path shares function blocks with FM and CDMA modes, it needs independent low pass
filter.
GPS IF signal from GPS RF-IF mixer is applied to S1M8660A via GPS SAW filter. Because both outputs of FM
SAW filter and GPS SAW filter are generally single ended signals, differential input pins of FM AGC are
designed to be shared with GPS block. And as a consequence of this sharing, external circuit is necessary for
switching of input signal. A recommended circuit for this is in Figure. 8.
The operation of I/Q demodulator is the same in CDMA/FM/GPS modes and the phase relation of I/Q signal of
the output is the same as depicted in Figure . 7.
GPS low pass filter of S1M8660A has its cut off frequency at around 800kHz.
FM_ENB
R2
GPS_ENB
R1
C3
FM_IF
GPS_IF
C4
L1
D1
S1M8660A
L2
C2
10
9
C1
D2
F/GRX_IF2
F/GRX_IF1
Figure 7. FM/GPS IF Input Application
A-D converter, as output of GPS path, is the 4bit parallel converter which is the same one used in CDMA path.
But the sampling frequency is different from that of CDMA mode. And in operating in GPS mode, sampling clock
of A-D converter should be supplied from the modem.
15