Nokia 2650 Manual Do Serviço
ISSUE 1 09/2004
COMPANY CONFIDENTIAL
37
Copyright © 2004 Nokia. All Rights Reserved.
RH-53/54
8-System Module
Nokia Customer Care
The VCO for the 900/1800 (RH-53) bands covers the range of 3420 to 3840 MHz, while the
VCO for 850/1900 (RH-54) (and thereby the quad band) covers 3296 to 3980 MHz.
VCO for 850/1900 (RH-54) (and thereby the quad band) covers 3296 to 3980 MHz.
PLL Synthesizer, Functional Description
The frequency synthesis PLL in conjunction with the VCO and 2/4 dividers generates the LO
signal for both RX and TX paths, locked to the VCXO which again is locked to the base station
through the AFC.
signal for both RX and TX paths, locked to the VCXO which again is locked to the base station
through the AFC.
■
Receiver
The Receiver, figure 14, is a dual band direct conversion linear receiver. The received RF signal
is routed from the antenna to the FEM, where the RX/TX switch is located. The RX/TX switch
performs both the switching between receive – transmit routing of the antenna signals as well
as the selection of the band to be used.
is routed from the antenna to the FEM, where the RX/TX switch is located. The RX/TX switch
performs both the switching between receive – transmit routing of the antenna signals as well
as the selection of the band to be used.
The RX signal is routed from the RX/TX switch, in the FEM, to the RX bandpass filter. The filter
input is single ended and the output is balanced in order to exploit the balanced nature of the
RF-ASIC. The bandlimited signal is amplified in the internal LNA and the Pre-gain amplifier be-
fore being converted to a BB signal in the passive mixer.
input is single ended and the output is balanced in order to exploit the balanced nature of the
RF-ASIC. The bandlimited signal is amplified in the internal LNA and the Pre-gain amplifier be-
fore being converted to a BB signal in the passive mixer.
Figure 14:Simplified BB, either I or Q channel
The BB signal from the passive mixer is amplified by 24 dB in BBAMP1. In order to provide the
first band limitation a 4 MHz pole is added at the input and a 250 kHz pole at the output of
BBAMP1. No AGC is provided in this amplifier. BBAMP1 is followed by LPF1 with a gain of 14
dB and with a pole at 86 kHz. LPF1 is followed by DCN1 (DC compensation amplifier 1) with a
minimum gain of 0 dB and a maximum gain of 24 dB. The DCN1 output is followed by a con-
trolled attenuator, which has a control range of 48 dB. The attenuator output is filtered in LPF2,
a biquad filter, before passing DNC2, (DC compensation amplifier 1). The total filter combina-
tion gives a flat transfer function from DC to 90 kHz. All capacitors for both filters are located in
the RF-ASIC.
first band limitation a 4 MHz pole is added at the input and a 250 kHz pole at the output of
BBAMP1. No AGC is provided in this amplifier. BBAMP1 is followed by LPF1 with a gain of 14
dB and with a pole at 86 kHz. LPF1 is followed by DCN1 (DC compensation amplifier 1) with a
minimum gain of 0 dB and a maximum gain of 24 dB. The DCN1 output is followed by a con-
trolled attenuator, which has a control range of 48 dB. The attenuator output is filtered in LPF2,
a biquad filter, before passing DNC2, (DC compensation amplifier 1). The total filter combina-
tion gives a flat transfer function from DC to 90 kHz. All capacitors for both filters are located in
the RF-ASIC.
The gain characteristic of the BB amplifier is an amplifier with a maximum gain of 80 dB with
an AGC range of 72 dB.
an AGC range of 72 dB.
The receiver selectivity for out-of-band signals is defined by the RF front-end SAW filter.
4 MHz
pole at
input
250
kHz
kHz
pole at
output
86 kHz
pole
BBAMP
1
LPF 1
DCN 1
AGC
LPF 2
DCN 2
114 kHz
pole pair
Gain ~24 dB
Gain ~14 dB
Gain ~ 0 to
24 dB
Gain ~ -48
to 0 dB
Gain ~20 dB
Gain ~0 dB
AGC ~ 0 dB
AGC ~ 0 dB
AGC ~ 24 dB
AGC ~ 48 dB
AGC ~ 0 dB
AGC ~ 0 dB
Step ~ 6 dB
Step ~ 6 dB