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PMB2240

GSM-Transmitter

Siemens AG 

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- Transmitter with I/Q modulator

- Direct I/Q modulation

- Generation of orthogonal carriers with possibility of phase adjust with external

resistors at OFF1/OFF2

- 32dB minimum carrier rejection, 35dB minimum SSB rejection with 1 Vpp I/Q drive level

- 50dB rejection of third order products with 1 Vpp I/Q drive level

- -3dBm output power at 1 Vpp I/Q drive level with 200 Ohms load according testcircuit 1

- RF oscillator signal is AC-coupled to internal buffer stage (symmetrical or unsymmetrical)

- The RF oscillator-signal is buffered for off-chip use, especially for receiver chip PMB2405.

- Prescaler for the RF oscillator signal

- Possibility to build RF-PLL with integrated prescaler + PMB2306

- Possibility to use the IF oscillator signal from the IF-VCO on PMB2405

- Possibility to use external source for IF oscillator-signal

- Digital parts of fixed IF frequency PLL (fixed-PLL) for IF-VCO on PMB2405

- Supply voltage range from 2.7 V to 4.5 V

- P-TQFP-48 package

- Temperature range -30° to 85°C

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- Vector modulated digital mobile cellular systems as GSM, DAMPS, PDC,WLAN etc.

- Various modulation schemes, such as PM, PSK, FSK, QAM, QPSK, GMSK etc.

- Analog systems with FM and AM modulation

- Space and power saving optimizations of existing discrete transmitter circuits

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The PMB2240 is a single-chip transmitter which includes a prescaler for the main oscillator signal and

a fixed frequency PLL for the IF oscillator. The transmitter is designed for use in conjunction with the

single-chip receiver PMB2405 and the CMOS PLL PMB2306.

The RF oscillator signal can be supplied from an external source symmetrically as well as

unsymmetrically. The oscillator signal can be buffered for off-chip use, depending on a separate power

down pin.

There is a prescaler by 64/65 for the RF oscillator signal on chip, which can be used to implement a

PLL together with the PMB2306.

The on-chip fixed-PLL consists of the system clock divider, the IF oscillator signal divider, the phase

detector and the charge pump. The IF oscillator signal divider is driven by the oscillator on the

PMB2405 or by an external discrete VCO.

The two oscillator signals are combined in the transmit mixer, and the image sideband and other

mixing products are suppressed with an external interstage filter. The filtered signal reenters the chip

at the modulator inputs LO/LOX. The modulator generates two orthogonal carriers which are mixed

with the modulation signals I and Q in two Gilbert multipliers. The phase between the two carriers can

be fine-adjusted to 90 ° (orthogonality) by two external resistors at OFF1/OFF2 for best SSB

suppression. The outputs of the Gilbert cells are added and amplified by a linear output stage.

The PMB2240 is designed for digital mobile telephones according to the GSM-Standard. The chip can

also be used for other digital systems and the dual mode system.

As part of the Siemens GSM/DCS chipset the derivatives PMB2245 and PMB2247 are offered for the

DCS 1800 and DCS 1900 frequency range.

The reproduction, transmission or use of this document is not permitted without express written authority. Offenders will be liable for damages. All

rights, including rights created by patent grant or registration of a utility model or design, are reserved.

Siemens AG

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05.97

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