CMLMICRO CMX264

CMX264
Frequency Domain
Split Band Scrambler
D/CMX264/1 August 1999
1.0
Features
• Ensures Privacy
•
•
•
•
Full Duplex
High Quality Recovered Audio
Low Height, Surface Mount Package
3.0V, Low Power Operation
1.1
Advance Information
•
•
•
•
•
Fixed or Rolling Code
Standby Mode
Uses Split Band Inversion
Low Current, Low Voltage
4.433619MHz Operation
Brief Description
The CMX264 is a frequency domain scrambler for use in analogue cellular phone systems. It contains
separate Tx and Rx paths for full duplex operation and operates under µProcessor control via a simple serial
interface.
In the Tx path, scrambling is achieved by splitting the audio band into two parts, or sub-bands, and frequency
inverting each one. The frequency at which the signal is split, the “split-point”, can be either fixed or rolling
between four possible settings resulting in a transmitted audio signal which is unintelligible to eavesdroppers.
Descrambling is achieved by a receive device set to the same split point as the remote transmitter. Thus if the
Tx and Rx devices are synchronously cycled through the same sequence of split points, a clear recovered
signal will emerge at the output of the receiver.
A 4.433619MHz crystal is used allowing up to four split points to be programmed. The device is designed to
be compatible with existing cellphone circuitry.
 1999 Consumer Microcircuits Limited
Frequency Domain Split Band Scrambler
CMX264
CONTENTS
Section
Page
1.0 Features ......................................................................................................1
1.1 Brief Description.........................................................................................1
1.2 Block Diagram ............................................................................................3
1.3 Signal List ...................................................................................................4
1.4 External Components.................................................................................6
1.5 General Description....................................................................................7
1.5.1 Tx Channel ..................................................................................7
1.5.2 Rx Channel ..................................................................................8
1.5.3 Serial Interface ............................................................................9
1.6 Application Notes .....................................................................................13
1.6.1 General Use ...............................................................................13
1.6.2 Input Anti-Alias and Output Smoothing Filters.......................13
1.7 Performance Specification.......................................................................14
1.7.1 Electrical Performance..............................................................14
1.7.2 Packaging..................................................................................25
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Frequency Domain Split Band Scrambler
1.2
CMX264
Block Diagram
Figure 1: Block Diagram
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Frequency Domain Split Band Scrambler
1.3
CMX264
Signal List
Package
D5
Signal
Description
Pin No.
Name
Type
1
-
-
This pin should be left unconnected.
2
-
-
This pin should be left unconnected.
3
4
XTAL
XTALN
5
6
MICO
7
8
I/P
O/P
O/P
VBIAS
O/P
A 4.433619MHz crystal is connected to these
pins with the appropriate external components
(see Figure 2).
Alternatively, an externally derived clock signal
may be applied to the XTAL pin. In this case,
the XTALN pin should be left unconnected.
This pin should be left unconnected.
The Tx audio output from the scrambler. This
signal may be scrambled or clear. If scrambled
it may come from the variable split-band (VSB)
scrambler direct or via the Tx de-emphasis
block. All signal paths depend upon the internal
state selected.
This pin should be left unconnected.
A bias line for the internal circuitry, internally
held at ½VDD. This pin must be decoupled to
VSS by a capacitor mounted close to the device
pins.
9
-
-
This pin should be left unconnected.
10
-
-
This pin should be left unconnected.
11
MICIN
12
VSS
13
14
I/P
Power
-
RXIN
 1999 Consumer Microcircuits Limited
I/P
The input for the signal from the microphone
amplifier/limiter. This pin may be the input to the
Tx pre-emphasis circuit, the VSB scrambler or
the clear path, depending upon the internal state
selected.
The negative supply rail (ground)
This pin should be left unconnected.
The input for the received audio signal, whether
scrambled or clear. This pin may be routed to
the Rx pre-emphasis circuit, the flatband
frequency descrambler or the clear path,
according to the internal state selected via the
serial interface.
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Frequency Domain Split Band Scrambler
1.3
CMX264
Signal List (continued)
Package
D5
Signal
Description
Pin No.
Name
Type
15
-
-
This pin should be left unconnected.
16
MUTERX
I/P
A logic input which when high (VDD) immediately
de-activates the two Rx outputs (RECO and
EXTO), overriding the serial data previously
loaded. When this input is low (VSS), the Rx
outputs are controlled by the serial data port.
17
EXTO
O/P
One of two Rx outputs. This is used for routeing
the recovered audio to external devices, e.g. a
speakerphone. This output may be
independently activated or de-activated by
selecting the appropriate internal state. When
de-activated, either by the serial data or by the
MUTERX pin, the output is set to VBIAS.
18
19
-
-
RECO
20
O/P
-
21
22
23
CSN
SCLOCK
SDATA
24
VDD
Notes: I/P =
O/P =
BI
=
-
This pin should be left unconnected.
The other Rx output. This is used for routeing
the recovered audio to the telephone
loudspeaker. This output may be independently
activated or de-activated by selecting the
appropriate internal state. When de-activated,
either by the serial data or by the MUTERX pin,
the output is set to VBIAS.
This pin should be left unconnected.
I/P
I/P
I/P
)The serial port input pins. Data applied here
)sets up the internal state of the device, e.g. split
)point, scramble/clear, etc. See Figure 10.
POWER
The positive supply rail. This pin must be
decoupled to VSS by a capacitor mounted close
to the device.
Input
Output
Bidirectional
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Frequency Domain Split Band Scrambler
1.4
CMX264
External Components
C1
C2
C3
C4
C5
C6
X1
Note:
10pF
±10%
10pF
±10%
100nF
±20%
100nF
±20%
100nF
±20%
100nF
±20%
4.433619MHz
C5 and C6 should be low inductance types which are mounted close to their
respective device pins.
Figure 2: Recommended External Components
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Frequency Domain Split Band Scrambler
1.5
CMX264
General Description
This device has been designed to be compatible with mobile station baseband channels. All signal processing
blocks such as lowpass filters, pre-emphasis, de-emphasis, and balanced modulators use switched capacitor
(SWC) techniques.
In each mode of operation, all blocks not in the signal path are turned off in order to minimise power
consumption. All internal settings and signal paths are selected by means of the serial interface according to
Section 1.5.3.
1.5.1
Tx Channel
1.5.1.1 Tx Channel Pre-Emphasis
A pre-emphasis circuit at the input of the Tx scramble block. It has a slope of 6dB per octave between
280Hz and 3140Hz. In scramble mode, it may be selected to “whiten” the audio signal prior to split
band inversion. It may be used in conjunction with the optional de-emphasis at the Rx output of the
descrambler.
1.5.1.2 Tx Lowerband Input Filter (TXLBIPF)
A lowpass filter whose input is the externally amplified and limited baseband audio signal from the
microphone. It selects that part of the audio spectrum which is below the split point. Its output signal is
processed by the lowerband balanced modulator and output filter to form the transmitted lowerband.
The bandwidth of the lowerband is controlled according to the split point chosen by varying the
bandwidth of this filter. The bandwidth is proportional to the sampling clock frequency and so an
appropriate clock frequency is internally selected for each split point.
1.5.1.3 Tx Lowerband Balanced Modulator
This modulates the output of the Tx Lowerband Input Filter (TXLBIPF) to form a frequency shifted
upper sideband and a frequency inverted lower sideband. It is the frequency inverted lower sideband
which is eventually transmitted as the lower frequency part of the scrambled signal, i.e. the lowerband.
The lower carrier frequency varies with split point and is always about 230Hz above the corner
frequency of the preceding lowpass filter (TXLBIPF). This means that baseband frequencies around
230Hz below the lower carrier frequency are translated to approximately 230Hz in the scrambled
audio. These frequencies form the lowest corner frequency of the transmit spectrum.
1.5.1.4 Tx Lowerband Output Filter (TXLBOPF)
A lowpass filter whose input is the output signal from the lowerband balanced modulator. Its function is
to select the frequency inverted lower sideband and remove the upper sideband. The resulting output
signal from this filter forms the lowerband part of the scrambled audio. It is summed with the output of
the Tx upperband channel to form the complete scrambled signal for transmission. This filter's corner
response also eventually defines the lower corner frequency of the recovered audio.
1.5.1.5 Tx Upperband Input Filter (TXUBIPF)
A lowpass filter whose cutoff frequency represents the upper limit of the baseband audio which is
scrambled, transmitted and descrambled. The output from this filter is processed by the upperband
balanced modulator, the output filter and any external channel filtering to form the transmitted
upperband.
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Frequency Domain Split Band Scrambler
CMX264
1.5.1.6 Upperband Balanced Modulator
This modulates the output of the Tx Upperband Input Filter (TXUBIPF) to form two sidebands, a
frequency inverted lower sideband and a non-inverted upper sideband. Part of the inverted lower
sideband is selected by the Tx Upperband Output Filter (TXUPOPF) to form the transmitted
upperband, i.e. that part of the audio spectrum above the split point.
For each split point setting, the upper carrier frequency is chosen so that baseband frequencies close
to 2770Hz are shifted to just above the split point. Conversely, baseband frequencies just above the
split point are shifted to the upper transmission limit of the channel. The result is that the upper carrier
is the same (approximate) distance above the lower carrier at all split point settings. The
approximation arises because of the need to have frequencies derivable from the crystal frequency
and the fact that only certain divisors of associated filter sample rates have been chosen as carriers, in
order to avoid aliasing.
1.5.1.7 Tx Upperband Output Filter (TXUBOPF)
A lowpass filter whose input is the output signal from the upperband balanced modulator. Its function
is to select that part of the frequency inverted lower sideband which will form the upperband part of the
transmitted scrambled audio. This output is summed with the output of the lowerband Tx channel to
form the complete scrambled signal for transmission.
This filter's response, together with any external filtering e.g. a lowpass filter used to ensure
compliance with statutory transmission requirements, defines the upper frequency of the transmitted
scrambled signal.
1.5.1.8 Tx Summer
This sums the lowerband and upperband to form the complete scrambled audio signal prior to
transmission.
1.5.1.9 Tx Channel De-Emphasis
A de-emphasis circuit at the output of the Tx scramble block. It has a slope of -6dB per octave
between 280Hz and 3140Hz. It may be used to compensate for pre-emphasis in the transmission
channel.
1.5.2
Rx Channel
1.5.2.1 Rx Channel Pre-Emphasis
A pre-emphasis circuit at the input of the Rx descramble block. It has a slope of 6dB per octave
between 280Hz and 3140Hz. In descramble mode, it may be selected to pre-emphasise the received
audio signal prior to signal recovery. It may, for example, be used to compensate for de-emphasis in
the transmission channel.
1.5.2.2 Rx Lowerband Input Filter (RXLBIPF)
A lowpass filter whose function is to select the lowerband part of the received scrambled signal. Its
bandwidth is controlled by the split point setting, which should be chosen to match the spectrum of the
received lowerband.
1.5.2.3 Rx Lowerband Balanced Modulator
This modulates the output of the preceding Rx Lowerband Input Filter (RXLBIPF). The carrier is
identical to that of the lowerband carrier in the transmitter section. The output consists of two
sidebands.
The lower sideband is inverted with respect to the received lowerband, i.e. returned to its original
frequency with respect to the original baseband signal. If the Tx and Rx carriers are the same
frequency, the lower sideband is the desired recovered lowerband.
The upper sideband is not required in the final descrambled output. It is removed by the Rx
Lowerband Output Filter (RXLBOPF)
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Frequency Domain Split Band Scrambler
CMX264
1.5.2.4 Rx Lowerband Output Filter (RXLBOPF)
A lowpass filter whose function is to select the lower sideband output of the preceding balanced
modulator. Its output is the lowerband part of the descrambled signal which is summed with the
output of the upperband Rx channel to form the complete descrambled signal.
1.5.2.5 Rx Upperband Input Filter (RXUBIPF)
A lowpass filter whose cutoff frequency is close to the upper corner frequency of the transmit channel.
Its function is to select the received scrambled signal and reject channel noise at frequencies above
this signal.
It is assumed that any transmitted 4kHz SAT tone has been attenuated prior to the Rx channel input of
the CMX264.
1.5.2.6 Rx Upperband Balanced Modulator
This modulates the output of the preceding Rx Upperband Input Filter (RXUBIPF). The carrier is
identical to that of the upperband carrier in the transmitter section. The output consists of two
sidebands.
The lower sideband is inverted with respect to the received lowerband, i.e. non-inverted with respect to
the original baseband signal. If the Tx and Rx carriers are the same frequency, the lower sideband is
the desired recovered upperband.
The upper sideband is a non-inverted, frequency shifted signal and is not required in the final
descrambled output. It is removed by the Rx Upperband Output Filter (RXUBOPF).
1.5.2.7 Rx Upperband Output Filter (RXUBOPF)
A lowpass filter whose function is to select the lower sideband output of the Rx upperband balanced
modulator. Its output is the upperband part of the descrambled signal which is summed with the output
of the lowerband Rx channel to form the complete descrambled signal.
1.5.2.8 Rx Summer
This sums the lowerband and upperband to form the complete descrambled audio signal.
1.5.2.9 Rx Channel De-Emphasis
A de-emphasis circuit at the output of the Rx descramble block. It has a slope of -6dB per octave
between 280Hz and 3140Hz. It may be selected to de-emphasise the recovered (descrambled) audio
signal. It may be selected in conjunction with the pre-emphasis circuit at the input of the Tx scramble
block.
1.5.3
Serial Interface
1.5.3.1 General Operation
The serial interface controls the internal states and modes of operation of the CMX264. Data is input to
the SDATA pin MSD (D10) first and is clocked into the device on the rising edge of SCLK. Only the
last 11 bits of data is loaded on the rising edge of CSN. The bit functions are shown in
Table 1. Also refer to the timing diagram of Figure 10.
D10
D9
Powersave
Clear/
Scramble
D8
D7
D6
MICO
RECO
EXTO
Output Control Output Control Output Control
D5
D4
D3
Pre/De-Emphasis
Select/Bypass
D2
D1
D0
Split Point
Select
Table 1
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Frequency Domain Split Band Scrambler
CMX264
1.5.3.2 Powersave Mode (D10)
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
1
X
X
X
X
X
X
X
X
X
X
Table 2: Powersave Mode
D10 = 1 powersaves the whole device, including the oscillator. All other bits become DON'T CARE
when this mode is selected.
On power up, the CMX264 automatically sets itself into the powersave state.
The host equipment should then select the operating mode via the serial interface at least 3ms after
initial power up. The delay is to allow the reset circuit to become dormant. This is the only occasion on
which it operates.
1.5.3.3 Clear/Scramble Modes (D9)
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
0
1
MICO
Output Control
RECO
Output Control
EXTO
Output Control
X
X
X
X
X
X
Table 3: Clear Mode
D9 = 1 selects clear mode. The scramble, descramble, pre-emphasis and de-emphasis blocks in both
Tx and Rx channels are all bypassed. No signal processing or filtering is carried out.
All other bits become DON'T CARE except the output select bits (D8, D7, D6).
D10
D9
D8
D7
D6
0
0
MICO
Output Control
RECO
Output Control
EXTO
Output Control
D5
D4
D3
Pre/De-Emphasis
Block Select
D2
D1
D0
Split Point
Select
Table 4: Scramble Mode
D9 = 0 selects scramble mode, i.e. the scrambler and descrambler blocks in the Tx and Rx channels
are selected.
In this mode, the split point is controlled by bits D1, D0. The four Pre-De-Emphasis blocks are
independently selectable by means of bits D5, D4, D3, D2.
.
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Frequency Domain Split Band Scrambler
CMX264
1.5.3.4 Output Select (D8, D7, D6)
D10
D9
D8
D7
D6
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
D5
D4
D3
D2
Pre/De-Emphasis
Select/Bypass
D1
D0
Split Point
Select
MICO
RECO
EXTO
Bias
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Bias
Active
Active
Pre/De-Emphasis
Blocks all Powersaved
and Bypassed
X
X
X
X
Scrambler
Bypassed
Bias
Bias
Active
X
X
Bias
Active
Active
Table 5
Bits D8, D7, D6 activate or de-activate the audio outputs in both clear (D9 = 1) and scramble
(D9 = 0) modes:
Bit D8 controls the Tx output MICO.
Bit D7 controls the Rx output RECO.
Bit D6 controls the Rx output EXTO.
In all cases, the output is activated by setting the relevant data bit to logic 1 and is de-activated
by setting the bit to logic 0. The Rx outputs (RECO and EXTO) can also be de-activated by the
MUTERX pin, which asynchronously overrides bits D6 and D7.
When activated, the signal output at an output pin is determined by the internal state of the device,
e.g. in clear mode (D9 = 1), the MICO pin will output the signal from the MICIN pin. In scramble mode,
when the Tx de-emphasis circuit is selected, the MICO pin will carry the signal from the de-emphasis
output, and so on.
When de-activated, an output is pulled to VBIAS by means of an internal high impedance.
1.5.3.5 Pre/De-Emphasis Select (D5, D4, D3, D2)
D10
D9
D8
D7
D6
0
0
MICO
Output Control
RECO
Output Control
EXTO
Output Control
D5
D4
D3
Pre/De-Emphasis
Select/Bypass
(See Text)
D2
D1
D0
Split Point
Select
Table 6
Bits D5, D4, D3, D2 have an effect in scramble mode only and are used to select or bypass the preemphasis and de-emphasis blocks.
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Frequency Domain Split Band Scrambler
CMX264
The bits are used as follows:
D2
D3
D4
D5
Tx Channel
Tx Channel
Rx Channel
Rx Channel
Input Pre-Emphasis
Output De-Emphasis
Input Pre-Emphasis
Output De-Emphasis
In all cases, setting the relevant bit to 1 selects the block. Resetting the bit to 0 bypasses and
powersaves it.
1.5.3.6 Scramble Mode - Split Point Selection (D1, D0)
D10
D9
D8
D7
D6
0
0
MICO
Output
Control
RECO
Output
Control
EXTO
Output
Control
D5
D4
D3
Pre/De-Emphasis
Select/Bypass
D2
D1
D0
Split
Point
(Hz)
Lower
Carrie
r
(Hz)
Upper
Carrie
r
(Hz)
0
0
1
1
0
1
0
1
1966
1482
1276
1027
2244
1759
1551
1304
5132
4618
4398
4198
Table 7: Split Point Selection
Bits D1, D0 operate in scramble mode only and are used to select the split point.
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1.6
Application Notes
1.6.1
General Use
CMX264
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 Electrical Performance Specification in Section 1.7.1).
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.
1.6.2.
Input Anti-Alias and Output Smoothing Filters
1.6.2.1 Input Anti-Alias Filtering
The internal circuitry of the device uses sampled techniques and so anti-alias filtering and post-filtering
(smoothing) may be required.
Input anti-alias filtering is supplied on chip at the MICIN and RXIN inputs. The filtering is first order with
a corner frequency of 25kHz.
Possible alias frequencies are:
(with input pre-emphasis selected)
63.337kHz
(with input pre-emphasis not selected)
85.261kHz
63.337kHz
52.780kHz
44.336kHz
184.734kHz
(Split point 1)
(Split point 2 and clear mode)
(Split point 3)
(Split point 4)
(All split points)
1.6.2.2 Output Smoothing
All output buffers are sampled circuits clocked at 63.337kHz but no post-filtering is provided on chip.
This is not included in this product as such circuitry is normally included elsewhere, so it may be
necessary for the host equipment to provide this filtering either to comply with transmission
requirements or to prevent aliasing within other sampled circuits in the system.
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Frequency Domain Split Band Scrambler
1.7
Performance Specification
1.7.1
Electrical Performance
CMX264
Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the device.
Supply (VDD - VSS)
Voltage on any pin to VSS
Current into or out of VDD and VSS pins
Current into or out of any other pin
D5 SSOP Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
Operating Temperature
Min.
-0.3
-0.3
-30
-20
Max.
7.0
VDD + 0.3
+30
+20
Units
V
V
mA
mA
Min.
-55
-40
Max.
550
9
+125
+85
Units
mW
mW/°C
°C
°C
Min.
2.7
-40
4.43229
Max.
3.75
+85
4.43495
Units
V
°C
MHz
Operating Limits
Correct operation of the device outside these limits is not implied.
Notes
Supply (VDD - VSS)
Operating Temperature
Xtal Frequency
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Frequency Domain Split Band Scrambler
CMX264
Operating Characteristics
For the following conditions unless otherwise specified:
Xtal Frequency = 4.433619MHz, Noise Bandwidth = 25kHz.
VDD = 3.0V, Tamb = - 40°C to +85°C.
Input Signal 0dB = 250mV (Tx Channel), 100mV (Rx Channel) @1kHz, scramble mode selected.
Neither pre nor de-emphasis enabled.
Typical radio channel filtering employed between transmitting (scrambling) and receiving
(descrambling) device (such as shown in Figure 8).
Notes
Min.
Typ.
Max.
Units
3.3
0.3
V
mA
mA
DC Parameters
VDD
IDD (powersaved)
IDD (not powersaved)
2.7
1
1
3.0
AC Parameters
Tx Channel
Audio In (MICIN)
Input Impedance
Signal Level
Audio Baseband Signal Lower 3dB Point
Audio Baseband Signal Upper 3dB Point
Scrambled Audio Out (MICO)
Scrambled Spectrum Lower 3dB Point
Scrambled Spectrum Upper 3db Point
Scrambled Spectrum Signal Level at
4000Hz
Tx Channel Passband Gain
Output Impedance (output active)
Output Impedance (output not active)
Any Spurious Output
Noise and Distortion
100
2
2
2,3
2,3,4
230
3200
Hz
Hz
2,3,4
2,3,4,5
6
6
7,8,9
7,9,10
-26.0
-1.0
1.0
500
-40.0
2.0
dB
dB
kΩ
kΩ
dB
%
1000
kΩ
mVrms
Rx Channel
Scrambled Audio In (RXIN)
Input Impedance
Signal Level
2.5
100
250
Audio Out (RECO or EXTO)
Recovered Spectrum Lower 3dB Point
Recovered Spectrum Upper 3dB Point
Rx Channel Passband Gain
Output Impedance (output active)
Output Impedance (output not active)
Any Spurious Output
2,11
2,11
2,11,12
6
6
7,8
Noise and Distortion
7,10
 1999 Consumer Microcircuits Limited
300
1000
kΩ
mVrms
Hz
Hz
250
230
2700
15
300
230
2700
-2.0
1.0
500
-30.0
Hz
Hz
dB
kΩ
kΩ
dB
4.0
%
2.5
D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
Notes
Pre-emphasis Filters
Slope
Gain at 1kHz
13
De-emphasis Filters
Slope
Gain at 1kHz
13
Operating Split Points
14
Min.
Typ.
Max.
Units
6.0
0.7
dB/Octave
dB
-6.0
-0.7
dB/Octave
dB
Clear Mode Overall Signal Gain
15
1027
1276
1482
1966
0
Reset Circuit Delay
14
3.0
ms
Serial Data Clock Frequency
14
1.0
MHz
Digital Inputs
Input Logic "1" Level
Input Logic "0" Level
Notes:
Hz
dB
80%
20%
VDD
VDD
1.
Not including any current drawn from the device pins by external circuitry.
2.
This ignores the effects of pre-emphasis and de-emphasis, if selected.
3.
Relative to a single tone at the MICIN pin. Because of the frequency inversion of the
scrambling process, the output frequency will not in general be equal to the input frequency.
However, the scramble signal output MICO will typically be within the limits given by Figures
3, 4, 5 or 6. The scrambled signal upper rolloff is defined by the filter TXUBOPF (Figure 7).
4.
Filtering within the host equipment should ensure compliance with statutory transmission
requirements e.g. removal of a 4kHz SAT tone. See Figure 8 for a typical transmit filter which
would be used to accomplish this.
5
Not applicable within the region of the split point.
In transmit, the upperband is shifted upwards away from the lowerband so that there is a gap
in the scrambled spectrum. This avoids aliasing between the two bands in the recovered
audio. See Figures 3, 4, 5 and 6 which show these gaps for each split point.
6.
An output may be de-activated by powersaving the whole device (D10 = 0) or by deselecting it
by means of the relevant control bit (D6, D7 or D8) or, for the RECO and EXTO outputs, by
setting the MUTERX pin to logic ‘1’
7.
With a single tone at the relevant input pin (MICIN or RXIN).
8. This parameter specifies the level of any unwanted spurious tones relative to the expected
output tone, whether that wanted tone is frequency shifted or not. The unwanted tones may be
the result of carrier breakthrough, baseband breakthrough or other aliasing effects.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
9.
CMX264
Measured at the output of the host transmit radio filter, such as shown in Figure 8.
10. The distortion figure of the expected output tone, whether that wanted tone is frequency
shifted or not. This parameter is defined as the rms value of the spurious tones specified in
Note 8 plus the noise within the measurement bandwidth, divided by the rms value of the total
signal, i.e. the wanted signal plus noise plus spurious tones.
11. Specified over the complete scrambling/descrambling process i.e. scrambling by the Tx
channel of the transmitting device, typical radio channel filtering such as shown in Figure 8
and descrambling by the Rx channel of the receiving device. The typical Rx channel
passband gain of the CMX264 receive section only is -1.0dB.
12. Not applicable in the region of the split point.
The response may exceed these limits within ±0.3 octaves of the frequencies 1950Hz,
1420Hz, 1180Hz and 980Hz (for split points 1 to 4, respectively).
Also, it may be outside ±3dB within ±0.15 octaves of the frequencies 1900Hz,
1450Hz, 1210Hz and 1000Hz (for split points 1 to 4, respectively).
In the recovered audio, some of the energy at the split point will have been transmitted in the
lowerband and some will have been transmitted in the upperband. When the Rx device
reconstitutes the signal, frequencies in the vicinity of the split point will consist of signals
summed together which have a random phase in relation to each other. The relative phase will
change over time so that the signals will vary between reinforcing each other or cancelling
each other, thus taking the response outside the given limits.
13. See Figures 9a and 9b for typical responses of the pre/de-emphasis circuits.
14. The internal state of the device is controlled by the data D0-D10 input at the serial interface.
Data should not be loaded until 3ms after initial power up to allow the reset circuit to complete
its operation and exit the RESET state..
15. No filtering is performed in clear mode, however there is a possibility of aliasing at 63.337kHz
(see Section 1.6.2.1).
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
10
0
Response (d
-10
-20
-30
-40
-50
100
1000
10000
100000
Frequency (Hz)
Figure 3a
4
3
2
1
0
-1
-2
-3
-4
-5
-6
100
1000
10000
Frequency (Hz)
Figure 3b
Figure 3: Typical Response Envelope of Scramble Signal at MICO pin, relative to MICIN,
with Split Point 1 Selected.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
10
0
-10
-20
-30
-40
-50
100
1000
10000
100000
Frequency (Hz)
Figure 4a
4
3
2
1
0
-1
-2
-3
-4
-5
-6
100
1000
10000
Frequency (Hz)
Figure 4b
Figure 4: Typical Response Envelope of Scramble Signal at MICO pin, relative to MICIN,
with Split Point 2 Selected.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
10
0
-10
-20
-30
-40
-50
100
1000
10000
100000
F requency (Hz)
Figure 5a
4
3
2
1
0
-1
-2
-3
-4
-5
-6
100
1000
10000
F requency (Hz)
Figure 5b
Figure 5: Typical Response Envelope of Scrambled Signal at MICO pin, relative to MICIN,
with Split Point 3 Selected.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
10
0
Response (d
-10
-20
-30
-40
-50
100
1000
10000
100000
Frequency (Hz)
Figure 6a
4
3
2
1
0
-1
-2
-3
-4
-5
-6
100
1000
10000
Frequency (Hz)
Figure 6b
Figure 6: Typical Response Envelope of Scramble Signal at MICO pin, relative to MICIN,
with Split Point 4 Selected.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
10
0
-10
-20
-30
-40
-50
-60
100
1000
10000
F requency (Hz)
Figure 7: Typical Response of Upperband Transmit Output Filter (TXUBOPF)
10
0
-10
-20
-30
-40
-50
-60
100
1000
10000
Frequency (Hz)
Figure 8: Typical Transmission Channel Filtering to Ensure Compliance
with Statutory Transmission Requirement.
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
15
10
Response (dB)
5
0
-5
-10
-15
-20
100
1000
10000
Frequency (Hz)
Figure 9a
15
10
Response (dB)
5
0
-5
-10
-15
-20
100
1000
10000
Frequency (Hz)
Figure 9b
Figure 9: Typical Response of Pre-Emphasis and De-Emphasis Circuits
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
CMX264
Operating Characteristics - Timing Diagram
Figure 10: Serial Port Timing Diagram
 1999 Consumer Microcircuits Limited
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D/CMX264/1
Frequency Domain Split Band Scrambler
1.7.2
CMX264
Packaging
Figure 11: D5 Mechanical Outline: Order as part no. CMX264D5
Handling precautions: This product includes input protection, however, precautions should be taken to prevent device damage from
electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent
licences are implied. CML reserves the right at any time without notice to change the said circuitry and this product specification. CML
has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product specification.
Specific testing of all circuit parameters is not necessarily performed.
Oval Park - LANGFORD
MALDON - ESSEX
CM9 6WG - ENGLAND
Telephone: +44 (0)1621 875500
Telefax:
+44 (0)1621 875600
e-mail:
sales@cmlmicro.co.uk
http://www.cmlmicro.co.u
k
CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CML Product Data
In the process of creating a more global image, the three standard product semiconductor
companies of CML Microsystems Plc (Consumer Microcircuits Limited (UK), MX-COM, Inc
(USA) and CML Microcircuits (Singapore) Pte Ltd) have undergone name changes and, whilst
maintaining their separate new names (CML Microcircuits (UK) Ltd, CML Microcircuits (USA)
Inc and CML Microcircuits (Singapore) Pte Ltd), now operate under the single title CML Microcircuits.
These companies are all 100% owned operating companies of the CML Microsystems Plc
Group and these changes are purely changes of name and do not change any underlying legal
entities and hence will have no effect on any agreements or contacts currently in force.
CML Microcircuits Product Prefix Codes
Until the latter part of 1996, the differentiator between products manufactured and sold from
MXCOM, Inc. and Consumer Microcircuits Limited were denoted by the prefixes MX and FX
respectively. These products use the same silicon etc. and today still carry the same prefixes.
In the latter part of 1996, both companies adopted the common prefix: CMX.
This notification is relevant product information to which it is attached.
Company contact information is as below:
CML Microcircuits
(UK)Ltd
CML Microcircuits
(USA) Inc.
CML Microcircuits
(Singapore)PteLtd
COMMUNICATION SEMICONDUCTORS
COMMUNICATION SEMICONDUCTORS
COMMUNICATION SEMICONDUCTORS
Oval Park, Langford, Maldon,
Essex, CM9 6WG, England
Tel: +44 (0)1621 875500
Fax: +44 (0)1621 875600
uk.sales@cmlmicro.com
www.cmlmicro.com
4800 Bethania Station Road,
Winston-Salem, NC 27105, USA
Tel: +1 336 744 5050,
0800 638 5577
Fax: +1 336 744 5054
us.sales@cmlmicro.com
www.cmlmicro.com
No 2 Kallang Pudding Road, 09-05/
06 Mactech Industrial Building,
Singapore 349307
Tel: +65 7450426
Fax: +65 7452917
sg.sales@cmlmicro.com
www.cmlmicro.com
D/CML (D)/1 February 2002