CMX264D5 データシートの表示（PDF） - MX-COM Inc

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CMX264D5

Frequency Domain Split-Band Scrambler

MX-COM Inc  

Frequency Domain Split-Band Scrambler

11

4.3.5 Pre/De-Emphasis Select (D5, D4, D3, D2)

CMX264 Advance Information

D10

0

D9

D8

D7

D6

D5 D4 D3 D2 D1 D0

0

MICO

RECO

EXTO

Output Control Output Control Output Control

Pre/De-Emphasis

Select/Bypass

(See Text)

Split Point

Select

Table 8: Pre/De-Emphasis Select

Bits D5, D4, D3, D2 have an effect in scramble mode only and are used to select or bypass the pre-

emphasis and de-emphasis blocks.

The bits are used as follows:

D2 Tx Channel Input Pre-Emphasis

D3 Tx Channel Output De-Emphasis

D4 Rx Channel Input Pre-Emphasis

D5 Rx Channel Output De-Emphasis

In all cases, setting the relevant bit to 1 selects the block. Resetting the bit to 0 bypasses and powersaves it.

4.3.6 Scramble Mode - Split Point Selection (D1, D0)

D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Split Point

(Hz)

0 0 MICO RECO EXTO Pre/De-Emphasis 0 0

Output Output Output Select/Bypass

01

Control Control Control

10

11

1966

1482

1276

1027

Lower Carrier

(Hz)

2244

1759

1551

1304

Upper Carrier

(Hz)

5132

4618

4398

4198

Table 9: Scramble Mode - Split Point Selection

Bits D1, D0 operate in scramble mode only and are used to select the split point.

5 Application Notes

5.1 General Use

The transmit scramble function may be implemented by connecting the device in the microphone line. The

receive function is achieved by connecting the device in the earpiece line. Some external pre- and post-

amplification and limiting may be necessary to ensure good signal to noise and dynamic range performance.

Many existing cellphones incorporate the functions of SAT tone filtering and anti-splatter filtering so these

features are not included in the CMX264. The transmit and receive spectral shaping is designed to make this

interfacing easy.

It is anticipated that statutory transmission requirements will be met by filtering within the host equipment e.g.

for removal of a SAT tone at 4kHz. The filtering required for this is quite stringent (see Figure 8) and so the

Tx Upperband Output Filter (TXUBOPF) has been designed to avoid unnecessary signal loss in the region of

3kHz. (see Figure 7).

Because this filter does not completely remove unwanted harmonics from the output of the upperband

balanced modulator, transmit output distortion and noise is specified at the output of the host transmit filter

(see Section 6.1.3).

It is desirable to introduce any channel control signals (whether in-band or sub-audio) after the scramble

function and to remove the signals before descrambling.

2000 MX-COM, Inc.

www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054

Doc. # 20480210.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All Trademarks and service marks are held by their respective companies.

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