LG B1200 Schematics 8

2. TECHNICAL BRIEF

2-1 The RF Chipset

The A316 RF integrates the TRF6150 transceiver IC, TX/RX VCO, Power amplifier(RF3110), Front End Module 8450T(switchplexer, RF-SAW filter), for dulaband transmitting and receiving function.

32KHz QUARTZ

VCOs

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2. TECHNICAL BRIEF

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2-1-1 The Receiver

The RF receive signal( EGSM 925Mhz – 960MHz, DCS 1805Mhz – 1880Mhz) is input via the antenna or coaxial connector.

An antenna matching circuit is between the antenna and the connector.

2. TECHNICAL BRIEF

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2-1-2 The TX IF Modulator

The TX I & Q signals from baseband IC are fed to Pin#18-21 of the TRF6150, where they are then modulated onto a TX IF by the modulator inside TRF6150. The TX IF frequency is listed as below.

EGSM Band

DCS Band

The signal TX LO IF (416 ~ 429Mhz) is produced by the AUX VCO (832 ~ 858MHz), which has been divided down by a factor of 2 .

2-1-3 The Translation Loop Transmitter

The translation loop approach has many advantages over a traditional upconverter solution. A typical upconverter transmitter usually consists of an IF modulator followed by a mixer for upconversion to RF. In the translation loop transmitter, the RF transmit signal is instead generated directly by a voltage controlled oscillator (VCO), the phase of which is locked to the modulated IF reference in a fast phaselocked-loop. Because a VCO is inherently a lower-noise source than a mixer, the translation loop transmitter produces a low noise floor, so no subsequent high-selectivity filtering is necessary, and the diplexer or other post-PA filter of the conventional approach is eliminated. This saves power and cost, as the insertion loss of the duplexer is eliminated, and the output level of the power amplifier can be reduced.

The transmit signal is generated directly by a external TX/RX VCO (VON1885C28DKB). In the feedback path, the RF transmit signal is mixed with the off-chip main VCO to produce the desired TXIF (416 ~ 429Mhz). This TXIF signal from the feedback path is then compared to the TXIF signal from the IF modulator at the detector. The resulting signal after passing a low pass filter drives the external TX/RX VCO.

A high side injection, i.e. RF = LO - IF, is used in the EGSM band upconversion while a low side injection, i.e. RF = LO + IF, is used in the DCS band upconversion. This upconversion scheme, with appropriate TXIFs, allows for a single wide-band VCO to be used.

From To AUX VCO= 2 x IF Frequency

CH 1 CH 26 858 MHz CH 27 CH 43 852.8 MHz CH 44 CH 91 858 MHz CH 92 CH 108 842.4 MHz

CH 109 CH 985 858 MHz CH 986 CH 1002 842.4 MHz

CH 1003 CH 1024 858 MHz

From To AUX VCO= 2 x IF Frequency

CH 512 CH 532 832 MHz CH 533 CH 549 837.2 MHz CH 550 CH 575 832 MHz CH 576 CH 597 858 MHz CH 598 CH 614 837.2 MHz CH 615 CH 662 858 MHz CH 663 CH 679 852.8 MHz CH 680 CH 727 858 MHz CH 728 CH 744 852.8 MHz CH 745 CH 792 858 MHz CH 793 CH 809 847.6 MHz CH 810 CH 857 858 MHz CH 858 CH 874 847.6 MHz CH 875 CH 885 858 MHz

2. TECHNICAL BRIEF

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2-2 Front End Module

The switchplexer is used to control the Rx and Tx paths. And the control signals is connected to Switchplexer(Diplexer) of Front End

Module(FEM8450T) to switch either Rx or Tx path on. When the Rx path is turned on, the RF receive signal then feeds into two paths, EGSM Rx and DCS1800 Rx.

This Front End Module contains two RF SAW filters, DCS SAW Filter to filter any unwanted signal apart from the DCS Rx band. And the GSM SAW filter in the Front End Module is to filter out

unwanted signal beyond the GSM Rx band. These two paths are then connected to the GSMLNA and DCSLNA of TRF6150 respectively.

The RF receive signal is amplified by LNAs in TRF6150, and then the signal then feeds into quadrature demodulator for mixing with LO which is produced by the main synthesiser of TRF6150 and

external TX/RX VCO. TX/RX VCO will generate 2 times of RX frequency in EGSM band and half times of RX frequency in DCS band to minimize the DC offset generated by self mixing.

In TRF6150, the quadrature demodulator produce baseband(I/Q) signal . This I/Q signal is amplified by two variable gain amplifiers and filtered by low pass filter, and then fed to baseband IC in differential mode.

An t e n n a

An t e n n aAn t e n n a

An t e n n a S w i t c h

Swi tc hSwi tc h

Switch Module

Mo d u l eMo d u l e

Mo d u l e

Diplexer

DiplexerDiplexer

Diplexer

DC S 18 0 0

DC S 18 0 0DC S 1 8 0 0

DC S 18 0 0

Swi tc h

Swi tc hSwi tc h

Swi tc h

EG S M

EG S MEG S M

EG S M

Swi tc h

Swi tc hSwi tc h

Swi tc h

LPF

LPFLPF

LPF

LPFLPF

LPF

An t

An tAn t

An t

DC S 18 0 0

DC S 18 0 0DC S 1 8 0 0

DC S 18 0 0

band

bandband

band

EG S M

EG S MEG S M

EG S M ba n d

bandband

band

EGSM-Rx

EGSM-RxEGSM-Rx

EGSM-Rx

EGSM-Tx

EGSM-TxEGSM-Tx

EGSM-Tx

DCS1800-Rx

DCS1800-RxDCS1800-Rx

DCS1800-Rx

DCS1800-Tx

DCS1800-TxDCS1800-Tx

DCS1800-Tx

SAW

SAWSAW

SAW

SAWSAW

SAW

Fro nt

Fro ntFro nt

Fro nt End

En dEn d

En d Mod ul e

Mo d u l eMo d u l e

Mo d u l e

2. TECHNICAL BRIEF

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2-3 The PA Circuit

The RF3110 is a triple-band GSM/DCS/PCS power amplifier module that incorporates an indirect closed loop method of power control. This simplifies the phone design by eliminating the need for the complicated control loop design. The indirect closed loop is fully self contained and required does not require loop optimization. It can be driven directly from the DAC out-put in the baseband circuit.

The indirect closed loop is essentially a closed loop method of power control that is invisible to the user. Most power control systems in GSM sense either for-ward power or collector/drain current. The RF3110 does not use a power detector. A high-speed control loop is incorporated to regulate the collector voltages of the amplifier while the stages are held at a constant bias. The V RAMP signal is multiplied and the collector voltages are regulated to the multiplied V RAMP voltage.

2. TECHNICAL BRIEF

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2-4 Penpheral Citcult

Temperature Sensor

When the chip is not transmitting or receiving, its temperature can be measured by sensing the voltage on the external resistor from pin 31 to ground. From –40 to +85 C, the resistor voltage varies linearly from 0.9V to 1.35V.

Regulator and Serial Data Interface

TRF6150 built in 3 voltage regulators to supply internal functions and external RF components. The serial interface of TRF6150 consists of a 3-wire serial bus, comprising DATA, CLOCK and

STROBE signals. These signals are used to enter control words into the chip. The control words contain information for programming the regulators, the synthesizers and the receiver.

13 MHz Clock

The 13 MHz-clock consists of a TCXO (TOA1300VPM4DKG-SM2) which oscillates at a frequency of 13MHz. It acts as time base of all synthesizers and Baseband.

2-5 Digital Baseband Chip : HERCROM20, F741529

HERCROM20 is a chip implementing the digital baseband processing of a GSM mobile phone. It combines a TMS320C54X (LEAD2) DSP, a micro controller ARM7TDMIE, an internal 2Mbit RAM memory, and their associated application peripherals.

The HERCROM20 supports the following features:

• CPU & DSP

• Memory Interface (MEMINT)

• Interrupt Controller

• I2C / Micro Wire Interface

• Serial Port Interface (SPI)

• UART Control/Interface

• Display Interface

• SIM Card Interface

• I/O System Connector Interface

• Radio Interface (RIF)

• JTAG Interface

• Real Time Clock (RTC)

• General Timers / Watch Dog Timer

• Keypad Control

• Backlight Control

• Vibrator Control

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