MSP3405D Просмотр технического описания (PDF) - Micronas

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MSP3405D

Multistandard Sound Processors

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PRELIMINARY DATA SHEET

MSP 34x5D

4.1.2. Quadrature Mixers

The digital input coming from the integrated A/D conver-

ter may contain audio information at a frequency range

of theoretically 0 to 9 MHz corresponding to the selected

standards. By means of two programmable quadrature

mixers, two different audio sources; for example, NI-

CAM and FM-mono, may be shifted into baseband posi-

tion. In the following, the two main channels are provided

to process either:

– NICAM (MSP-Ch1) and FM/AM mono (MSP-Ch2) si-

multaneously or, alternatively,

– FM2 (MSP-Ch1) and FM1 (MSP-Ch2).

NICAM is not possible with MSP 3405D.

Two programmable registers, to be divided up into low

and high part, determine frequency of the oscillator,

which corresponds to the frequency of the desired audio

carrier. In section 6.2., format and values of the registers

are listed.

4.1.3. Low-pass Filtering Block

for Mixed Sound IF Signals

Data shaping and/or FM bandwidth limitation is per-

formed by a linear phase Finite Impulse Response (FIR-

filter). Just like the oscillators’ frequency, the filter coeffi-

cients are programmable and are written into the IC by

the CCU via the control bus. Thus, for example, different

NICAM versions can easily be implemented. Two not

necessarily different sets of coefficients are required,

one for MSP-Ch1 (NICAM or FM2) and one for MSP-

Ch2 (FM1 = FM-mono). In section 6.5.3., several coeffi-

cient sets are proposed.

VREFTOP

ANA_IN1+

AD_CV[7:1]

AGC

AD

DCO1

Oscillator

FIR1

Mixer

Lowpass

MODE_REG[6]

Phase and

AM Dis-

crimination

DQPSK

Decoder

Phase

Differen-

tiator

MSP sound IF channel 1

(MSP-Ch1: FM2, NICAM)

Carrier

Amplitude Detect

AD_CV[9]

MSP 3415D only

NICAM

Decoder

Mute

Lowpass

Mixer

ANA_IN-

FRAME

NICAMA

DCO2

Pins

Internal signal lines (see fig. 4–5)

Demodulator Write Registers

MSP sound IF channel 2 Amplitude

(MSP-Ch2: FM1, AM)

Carrier

Detect

Mixer

Lowpass

Oscillator

FIR2

Phase and

AM Dis-

crimination

Differen-

tiator

Phase

Mute

MODE_REG[8]

DCO2

Fig. 4–2: Demodulator architecture of MSP 34x5D

Lowpass

NICAMA

NICAMB

FM2

IDENT

FM1/AM

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