Sony Ericsson W890 Troubleshooting Manual page 88

Bluetooth and FM Radio
The STLC2592 circuit N1400 combines Bluetooth and FM tuner functionality into one.
Bluetooth
The Bluetooth implementation is compliant with Bluetooth specification 2.1 + EDR.
TM
The Bluetooth transceiver has frequency channels with 1 MHz separation from 2402 to 2480
MHz. The same band is used for both transmission and reception. This gives 79 frequency
channels.
Receiver
The first stage of the receiver is an external antenna filter, which suppresses unwanted
frequencies. The receiver is of a "near-zero" IF receiver architecture. The local oscillator is
generated by a frequency synthesizer, which allows the receiver to be set at frequencies in
intervals of 1 MHz. The synthesizer is controlled from the logic part.
The received signal is sampled in the logic for later signal processing.
Transmitter
The synthesizer generates the TX frequency which modulated by the BT baseband block. It is
then amplified. The BT system is a class 1 device with maximum of +4 dBm output power
(minimum setting is about -50 dBm).
FM Radio
FM Receiver
The receiver uses a digital low-IF architecture. The receive (RX) section integrates a low noise
amplifier (LNA) supporting the worldwide FM broadcast band (76 to 108 MHz). An automatic
gain control (AGC) circuit controls the gain of the LNA to optimize sensitivity and rejection of
strong interferers. An image-reject mixer down converts the RF signal to low-IF. The
quadrature mixer output is amplified, filtered and digitized with high resolution analog-to­
digital converters (ADCs). This advanced architecture allows the use of digital signal
processing (DSP) to perform channel selection, FM demodulation and stereo audio processing.
Tuning
The receiver uses frequency synthesizer technology including a completely integrated VCO.
The frequency synthesizer generates the quadrature local oscillator signal used to
downconvert the RF input to a low intermediate frequency. The VCO frequency is locked to
the reference clock and adjusted with an automatic frequency control (AFC) servo loop during
reception. The tuning frequency is defined as:
Freq (MHz) = Spacing (kHz) × Channel + Bottom of Band (MHz)
FUNCTIONAL OVERVIEW Technical Description
External Connectors
External units are connected to the transceiver by means of a 12-pin connector on the bottom
of the phone.
System connector pin out:
1
Vbus
Clocks
Clock Distribution
The clocking for the access and application subsystems is separated. This means that
they can wake up or go to sleep mode independently. The access subsystem is clocked by the
26 MHz Voltage Controlled Crystal Oscillator (VCXO) located in the GSM/EDGE module N1200
(Thor). When the access subsystem has a job to do, the Master Clock (MCLK) signal is
requested from the RF part. Most other clocks needed within the access subsystem are
generated from the MCLK. Some minor parts like sleep timer and cable detect use the 32 kHz
real-time clock. The 32 kHz real-time clock clocks the application subsystem, and all other
internal clocks needed within the application subsystem are generated from this clock.
However, when audio is transferred between the application and the access subsystems, the
MCLK is used.
Master Clock
(26 MHz)
The 26.00 MHz VCXO-based MCLK is distributed as a square wave signal from the
N1200 Gimli circuit. In order to have full control over the load on the MCLK, only the access
side of the digital baseband controller is allowed to request the MCLK. However, by indirect
means also the application side CPU can issue the request. A VCXO-based square wave is also
distributed to the WCDMA circuit, but is turned on only upon a command from the digital
baseband controller.
Real-time Clock
(32. 768 KHz)
A 32.768 kHz crystal oscillator provides a low frequency clock whenever the phone has power.
This clock is used to keep the Real-Time Clock (RTC) block functioning, so that the phone can
keep track of the time and date. The low frequency clock is generated in the analog baseband
controller N2000 (Vera) and distributed to the digital baseband controller D2000 (Anja), and if
necessary to external devices like Bluetooth, FM radio and A-GPS.
2 3 4 5 6 7 8
SP Mic+ Mic ­ Sp Sp Video AID GND
Ref / L R / /
/
Aux in Aux in / / Strobe ACB
L R DBG DBG /
TX RX Vpp
Flash
SEMC Troubleshooting Manual
W890
9 10 11 12
D+ D ­
/ / DCIO
DTMS DFMS
1217-3942 rev. 1 88 (119)