Modulation - Motorola W208 Manual

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W208 Level 3 Circuit Description

The volume control is performed in the audio digital filter. Volume control is performed in

steps of 1 dB from 0 dB to -30 dB. In mute state, attenuation is higher than 40 dB. The

gain is independently programmable on the Left and Right channels, using the same

Left/Right summer and 6dB attenuator allows output of a mono audio path. These

configurations are programmed with the register VAUDCTRL.

The Left and right head set amplifiers provide the stereo signal on terminals

Pin G1) and

HSOR

or the Right and Left headset outputs. The mono audio signal may be sum to the speech

signal and provided on the Auxiliary, Earphone and/or 8Ohm Speaker outputs. The Audio

Stereo/Mono path can be powered down and configure with the PWDNG, VAUDCTRL and

VAUDPLL registers.

2.4 Modulation

As illustrated in Figure 8, GMSK 0.3 is generated with Gaussian low-pass filtered

bipolar data, applied to a DC coupled FM modulator, set to a modulation index of 0.5.

2.4.1 Transmit Section

As compared with a traditional VCO, TI takes advantage of DCO scheme to design the

(U103

Pin F1). The mono audio signal may be provided on the Right

Figure 6: Stereo Audio Path

Figure 7: GMSK Modulation

Service Engineering & Optimization

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HSOL

(U103

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