Panasonic EB-X700, Руководство по обслуживанию

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4-3
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4.1.6 Antenna
The antenna is a fixed helical type and is designed for a triple band operation (EGSM 900, DCS 1800 and PCS 1900).
4.2. Transmitter
4.2.1 Functional Description
Figure 4.3: Transmitter Block Diagram
The transceiver IC U500 supports quadrature modulation and employs direct modulation. The differential I/Q inputs from
thebaseband circuit are up-converted to the transmit frequency by the quadrature modulator. The required signal path is
selected (EGSM 900 or DCS 1800/ PCS 1900). The transceiver output level is approximately 0 dBm.
The modulated outputs pass through third harmonic filters, FL500 and FL501, to the quad band limiter amplifier U501.
In EGSM operation, the differential outputs from the limiter amplifier pass into the TX SAW filter where they are converted into
a single-ended signal. The SAW filter also attenuates the Tx noise. In the case of PCS and DCS, the differential to single-
ended conversion takes place in the limiter amp and the output is passed into the input of the PAM U503. The PAM contains an
integrated power control function and therefore does not require any additional external components to implement the
Automatic PowerControl (APC) loop. The TX output from the PAM is applied to the ASM U502 which provides a connection
path via the RFconnector to the external antenna.
PROVISIONAL ISSUE