CLC-DRCS-PCASM
CLC-DRCS-PCASM DRCS Evaluation Board User's Guide
Literature Number: SNOS917C
CLC-DRCS-PCASM
DRCS Evaluation Board User’s Guide
June 1999
N
CLC-DRCS-PCASM
DRCS Evaluation Board User’s Guide
0
0
Overview
Required Evaluation Items
n DRCS Board
The DRCS Evaluation Board (CLC-DRCS-PCASM) is designed to
support simple and effective evaluation of the Diversity Receiver
Chipset (DRCS). This chipset consists of the CLC5956 Analog-toDigital Converter (ADC), the CLC5526 Digital Variable Gain
Amplifier (DVGA), and the CLC5902 Dual Digital Tuner/AGC.
The CLC5902 performs digital down conversion (DDC) and automatic gain control (AGC) with digital accuracy and repeatability.
(CLC-DRCS-PCASM)
n +5V power supply
n Signal generator
n DRCS Control Panel software
e
(drcscp.exe)
n PC running Windows® 95/98/NT
n One PC serial port
The DRCS Board accepts narrowband signals at IF frequencies up
to 300MHz (the LC noise filter must be retuned from the 150MHz
factory setup) and outputs quadrature baseband signals in a digital
format. There are two complete signal paths from the two input
connectors to the Channel A and Channel B digital outputs.
et
Suggested Evaluation Items
n Data Capture Board
(CLC-CAPT-PCASM)
n Data Capture Board software
The configuration of the DDC/AGC is controlled by a COP8 µController which loads one of several default configurations at power
up. The default configuration is selected using DIP switch SW2.
These configurations can also be modified with the DRCS Control
Panel software (drcscp.exe) provided with the DRCS Board that
runs under Windows® 95/98/NT.
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ol
(capture.exe)
n Data Capture Board User’s Guide
n Second PC serial port
n Matlab® software or other data
analysis software
Also available is a Data Capture Board (CLC-CAPT-PCASM) and
accompanying software (capture.exe) that mates with the evaluation board and enables the user to transfer data from the DDC/AGC
output, over the serial port of a PC and into a file.
Reference Documents
n CLC5956 data sheet
n CLC5526 data sheet
n CLC5902 data sheet
O
This document describes in detail the DRCS Board, DRCS Control
Panel software, and how to use it.
AIN1
Transformer
DVGA
ADC
150MHz
12
4
DDC/AGC
}
AOUT (serial)
BOUT (serial)
SCK
SFS
RDY
ParOut
J1
4
AIN2
Transformer
DVGA
ADC
12
150MHz
J9
RS-232
Serial I/O
Figure 1
COP8 µController
CLC-DRCS-PCASM Block Diagram
©1999 National Semiconductor Corporation
Rev. 3.01 June 4, 1999
General Description
DVGA
As seen in Figure 1, the DRCS Board accepts analog IF
inputs on a pair of SMA connectors and processes these
into baseband digital waveforms. There are several analog
components that condition the signal prior to sampling
with a pair of ADCs. The most important of these is the
DVGA which is the gain control element of an AGC loop.
The sampled signals are applied to a two channel digital
down converter (DDC) that performs a final mix to baseband, digitally filters the waveforms, and decimates to a
lower output sample rate. On-board automatic gain control
(AGC) loops operate in conjunction with the DVGAs to
extend the dynamic range of the analog signal paths.
The DVGA is a 350MHz amplifier that has a digitallycontrolled voltage gain range from -12 to +30dB in 6dB
steps. It has a 3rd-order output intercept point of 24dB at
150MHz and an o utpu t noise spectral density of
The DRCS Board is factory configured for an IF of
150MHz, a sampling frequency (FCK) of 52MSPS, and an
overall decimation of 192. This yields an output sample
rate of 270.8KSPS. The DDC/AGC features a high degree
of programmability so that key parameters such as mixer
frequency, decimation ratio, filter shape, etc. can be configured by the user.
The DVGA, in conjunction with the DDC/AGC, forms an
automatic leveling loop that compresses the dynamic
range of the input IF signal prior to sampling by the ADC.
By doing so, it extends the dynamic range of the ADC by
as much as 42dB. The loop dynamics and threshold of the
AGC are set by programming the control registers within
the DDC/AGC. It is also possible to inhibit the loop and
force specific DVGA gain values. These topics are
addressed later within this document.
Input Circuit and Signal Levels
G DVGA = ( 0.21 ) ⋅ 2
AGAIN
,
(EQ. 3)
e
where AGAIN is the 3-bit data word into the DVGA digital input of channel A. Refer to the CLC5526 data sheet
for further details.
et
The individual elements of the DRCS Board are discussed
in the following paragraphs.
69 nV ⁄ Hz . At 150MHz, the data sheet plots place the
maximum gain at about 28.5dB or,
Noise Filter
A simple noise filter resides between the DVGA and
ADC. Its only purpose is to attenuate noise from the
DVGA that appears at the ADC sampling image frequencies. Because of its simplicity, it does not have the ability
to sufficiently reject signals from the antenna that are
located at the sampling images. It is assumed that a SAW
filter will precede the DVGA and provide this capability.
The usefulness of the noise filter is due to the fact that
both the DVGA and ADC have wide bandwidths and so
there are many sampling images that fall in band. Each of
these will add noise power to the output if they are not
attenuated. See Figure 2.
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The AIN1 and AIN2 IF inputs are transformer coupled
into the DVGA inputs. The transformers are included to
interface with the differential analog components which
follow. They also match the 200 Ω input of the DVGAs to
the 50 Ω input connectors and provide a voltage gain of 2:
G XFMR = 2
(EQ. 1)
O
In a production system, the transformer might be replaced
by an IF SAW which also has differential output drive
capability. Please observe from the schematic diagrams
that the transformer introduces a dc short from the input
connector to ground.
With the DVGA set to maximum gain, the total analog
gain from the input connector to the ADC is 33.8dB and
an input level of -23.8dBm will drive a full-scale input at
the ADC. With the DVGA set to minimum gain, the total
analog gain is -8.3dB and a +18.3dBm input level is
required to drive the ADC to full scale. Typically, the
AGC reference level will be set such that the ADC will
never see full scale and the lowest gain setting of the
DVGA will not be used.
The total gain of the DRCS Board, including both the analog and digital parts is best described by the equation,
G TOTAL = G XFMR G DVGA G LC G DDC ,
(EQ. 2)
where the first term has already been introduced and the
others will be in subsequent sections of this manual.
The noise figure of the DRCS Board is 13dB and is calculated in the ADC section on page 3.
Rev. 3.01 June 4, 1999
2
The nominal component values for the filter provide a center frequency of 150MHz, a 3dB bandwidth of 18MHz,
and an insertion loss of 0.7dB. Assuming an ADC sample
rate of 52MSPS, the filter provides about 4dB of attenuation at the closest image frequency which is at 162MHz
(Figure 2). The attenuation at the image frequencies not
shown will of course be greater. More attenuation is possible by increasing the Q of the filter, but this would make
the center frequency tolerance more critical and also
increase the group delay through the filter. (The damping
of the AGC loop is negatively impacted by large group
delays.) More attenuation will also be achieved if the IF is
moved further away from 156MHz.
To change the IF frequency of the DRCS Board, the noise
filter components must be changed. The equations below
pertain to Figure 3 and provide a means of computing the
new values:
1
ω c = ----------------L1 CT
(EQ. 4)
©1999 National Semiconductor Corporation
Baseband Filter
Translated To
Sampling Images
Baseband
Filter
4dB
LC Noise
Filter
3X Sampling
Frequency
Sampling
Image
IF Frequency
150
202
162
208
214
Frequency (MHz)
Illustration of the need for noise filter attenuation at the sampling images.
(EQ. 5)
RT
C
G LC = 1 + ------- ⋅ ------T
QL
L1
(EQ. 6)
improves to 68dBFS (or, 55 nV ⁄ Hz at 52MSPS). This
behavior is due to the fact that the large-signal, high-frequency SNR is dominated by clock jitter. Communication
systems such as GSM require minimum SNRs of no better
than 9dB which can be achieved at input levels of 59dB
below full scale. Therefore, the ADC acts as though it
were a 68dB device for these systems (Figure 4). The digital filters following the ADC provide processing gain that
e
1 ω BW = -----------RT CT
et
Figure 2
156
C T = C93 ⁄ 2 + C 99 + 1.5pF
(EQ. 7)
In these equations, C 93 = C 94 , RT = 600 || 1K = 375Ω ,
G LC is the filter gain at ω c , and Q L is the quality factor of
DVGA Output
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the inductor at ω c .
SNR vs. Input Amplitude
80
Extrapolates to 68dB
70
ADC Input and Stray PCB Capacitance
60
C93
L1
C99
1.5p
1K
SNR (dBc)
600
C94
50
40
30
Noise filter components for AIN1.
O
Figure 3
20
10
In addition to setting the center frequency of the filter,
capacitors C93 and C94 absorb the transient current that is
sourced out of the ADC coincident with the sampling
instant. It is recommended that C 93 and C 94 be no less
-45
The frequency response of the noise filter can be checked
at spot frequencies by observing either the CLC5902
Mixer AI or BI outputs in debug mode with the NCO set
to 0 frequency and 0 phase.
ADC
The ADC is a 12 bit, wideband converter capable of inputs
as high as 300MHz at sample rates of 52MSPS. The SNR
for an input 3dB below the full scale input of 2VPP differential is 62dBFS at an IF frequency in the range of
150MHz. For levels much below this, however, the SNR
3
-40
-35
-30
-25
-20
-15
-10
-5
0
Input Amplitude (dBFS)
Figure 4
than 20pF.
©1999 National Semiconductor Corporation
-50
CLC5956 SNR extrapolates to 68dBFS.
improve further upon this by 24dB (factory default configuration). Assuming that a single sampling image interferes
at a level of -4dB (Figure 2), the total noise voltage density
at the ADC input is,
2
2
55 + 69 ( 1 + 10
– 4 ⁄ 10
) = 98nV ⁄ Hz .
(EQ. 8)
When this is referred through the 33.8dB maximum gain
to the input connector, this yields a 13dB noise figure for
the DRCS Board.
Rev. 3.01 June 4, 1999
+
1
,
B3
;
(
EXP
(from AGC)
(
/$
&
6
3+$6(B$
Figure 5
21
I
TO
OUTPUT
CIRCUIT
SAT
21
F2 FILTER
DECIMATE BY
2 OR 4
SAT & ROUND
21
F1 FILTER
DECIMATE BY 2
SAT & ROUND
SHIFT UP
21
Q
17
SIN
COS
NCO
CLC5902 down converter, channel A.
The digital output format of the ADC is two’s complement. For further information, consult the CLC5956 data
sheet.
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)5(4B$
22
CIC FILTER
DECIMATE BY
8 TO 2K
15
17
22
SHIFT UP
15
FLOAT
TO FIXED
CONVERTER
ROUND
EXPONENT
14
&
(
'
B
<
%
B
&
(
'
)
(
2
&
B
)
EXP
3
MUXA
)
(
2
&
B
)
$
B
1
,
$
*
0
0
-10
DDC
et
-20
The ADC outputs feed into the two channel DDC/AGC.
This part consists of two down converter channels (DDC)
and automatic gain control (AGC) loops. The DDC performs the final mix to baseband and baseband filtering
(see Figure 5).
-30
-50
-60
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ol
Magnitude (dB)
GSM blocker and interferer
requirements
-40
The NCO can tune across the full Nyquist band with 32 bit
precision. With phase dither enabled, the spurious performance is -101dBc or better and SNR is 84dB. The frequency and phase of the two channels are completely
independent. In addition, the phase dither of the two are
uncorrelated.
-70
-80
-90
-100
The FLOAT TO FIXED CONVERTER within the DDC
will match any change in gain by the DVGA with a compensating digital gain change. It does this by treating the
complement of the DVGA control word as an exponent to
the ADC output. The overall effect of this is to make the
Rev. 3.01 June 4, 1999
4
Figure 6
Output Power
O
Although the ADC combined with the processing gain of
the digital filters provides 92dB of instantaneous SNR,
this is not enough to meet the requirements of the
GSM900 specification without some analog filtering to
attenuate the blocker. Nonetheless, the digital filters can be
used to relax the requirements on the analog filter. In particular, the digital filters can meet the reference interference level of ETSI GSM 05.05 paragraph 6.3 without any
assistance from the analog filter. Further, the blocker performance of ETSI GSM 05.05 paragraph 5.1 can be met
with only minor assistance from the analog filter.
0
100
200
300
400
500
600
700
800
900
1000
Frequency (kHz)
Frequency response of down converter
O AG
ve C
rT O
hi per
s R at
an es
ge
-110
The baseband filtering is performed by a cascade of three
decimating FIR filters. The overall decimation ratio can be
programmed from 8 to 16,384. The two final filters feature
21 and 63 user-programmable taps, respectively. A set of
tap coefficients are published in the CLC5902 data sheet
which provide adequate filtering to meet the GSM blocker
and interferer requirements. The frequency response for
these at a sample rate of 52MSPS is shown in Figure 6.
DDC Output
ADC Output
Input Power
Figure 7
ADC and DDC output level vs. input level
©1999 National Semiconductor Corporation
$*&B7$%/(
$*&B/223B*$,1
Envelope Detector
SHIFT DOWN
AGAIN
3
MUX
POUT
32X8
RAM
FIXED
TO FLOAT
CONVERTER
2 STAGE
DECIMATE BY 8
CIC FILTER
ABSOLUTE
VALUE
AIN
EXP
$*&B,&B$
$*&B+2/'B,&
$*&B5(6(7B(1
$*&B)25&(
$*&B&2817
LOAD
ONE SHOT
$*&B(1
COUNTER
PERIOD
16
FUNCTION PROGRAMMED
INTO RAM
LOG
AGC circuit, channel A.
-REF
et
Figure 8
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EN
AGC
The AGC loop for channel A is shown in Figure 8. Each
channel has its own loop. The ADC output power is measured with an envelope detector and used to adjust the
DVGA gain. Envelope detection is performed by an
absolute value circuit followed by a lowpass filter whose
response is shown in Figure 9. The filtered signal is used
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ol
DRCS Board appear as a fixed gain channel with
extremely large dynamic range as shown in Figure 7. This
mode can also be inhibited by asserting (;3B,1+. An
expression for the gain through the DDC channel A is,
1
4
G DDC = --- ( '(& + 1 )
2
⋅2
⋅2
,
(EQ. 9)
[ 6&$/( – 44 – AGAIN ⋅ ( 1 – (;3B,1+ ) ]
*$,1
Magnitude Spectrum of Power Detect CIC Filter
0
0
⋅ G F1 ⋅ G F2
-10
21
∑ h1 ( i )
-30
63
∑ h2 ( i )
G F2 =
-40
i--------------------=1
-.
16
(EQ. 11)
2
-50
The numerators of G F1 and G F2 equal the sums of the
impulse response coefficients of F1 and F2, respectively.
For the STD and GSM sets, G F1 and G F2 are nearly equal
to unity. Observe that the AGAIN term in (EQ. 9) is cancelled by the corresponding term appearing in (EQ. 3) so
that the entire gain of the DRCS Board is independent of
1
the DVGA setting when (;3B,1+ . The --- appearing
2
in (EQ. 9) is the result of the 6dB conversion loss in the
mixer.
©1999 National Semiconductor Corporation
Magnitude
(dB)
Magnitude
(dB)
(EQ. 10)
2
O
G F1 =
-20
i--------------------=1
-,
16
5
-60
-60
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Frequency Normalized to Fs
0.7
0.8
0.9
1
1
Frequency Normalized to FCK
Figure 9
Frequency response of envelope detector
filter.
to address a lookup table which generates an error signal
based on the programmed threshold, deadband and loop
time constant targets. This error is integrated to produce
the 3 bit control signal for the DVGA. Integrator gain is
Rev. 3.01 June 4, 1999
In the course of measuring ADC power, the absolute value
block within the envelope detector also generates a second
harmonic of the aliased IF frequency. For example, an IF
of 150MHz aliases to -6MHz at the ADC output when the
sample rate is 52MHz. The absolute value block produces
from this a dc term and a second harmonic at -12MHz, the
latter of which is rejected by the low pass filter. If the alias
frequency is too low, though, its second harmonic will fall
within the passband of the filter and a clean power detection will not occur. This problem can be avoided by choosing the IF and sample rates such that the alias frequency
magnitude is greater than FCK/16.
Data and Clock Outputs
The CLC5902 outputs several standard serial formats for
interface to a DSP. These formats can be specified by loading the appropriate values in the CLC5902 registers. The
CLC5902 datasheet provides complete information. The
default setup of the DRCS Board is 3$&.(',
08;B02'( , and )250$7 . These settings provide a
24-bit serial output word, a frame sync output pulse once
for each I/Q pair, and the outputs for channel A and B
muxed onto the single output pin AOUT. The serial outputs and control signals are available at the Eurocard connector J1. This connector mates directly to the data capture
board which can be used to transfer data to a PC. The
serial output is also available from the 16-pin DSP interface header. Note that AND gate U12 is not factory loaded
but a location is provided for compatibility with previous
versions of the DRCS Board. The trace from pin 2 to 4 of
U12 must be cut before installing it.
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Deadband
6dB
DVGA Output Power
et
The user interface software makes programming of the
AGC very easy. The user need only specify the loop time
constant, reference and deadband and from these, the
lookup table values and shifter values are computed. As
shown in Figure 10, deadband in excess of 6dB shows up
as hysteresis. Hysteresis will eliminate excessive DVGA
gain changes caused by the input signal level dwelling at a
transition point.
to the signal level applied to the board. This mode is easiest to use and is probably suitable for most applications.
The default configuration of the DRCS Board and user
software is for this mode. The other mode is a gated mode
and is useful, for example, in TDMA systems when one
wishes the AGC to be active only during the power ramp
up. In this mode, the loop is active when the gate signal is
applied and then opens when the gate is removed. The gate
signal can be an external pulse whose width defines the
AGC active period. Alternatively, the gate can be an edge
which starts a counter within the DDC/AGC. The AGC
active period is then the time it takes for the counter to
reach its terminal value. By using the configuration registers, it is possible to write the initial gain condition of the
loop into the integrator and also to read the final gain
value from this integrator. Consult the CLC5902 data
sheet for further details.
e
programmable via the shifter preceding it to allow loop
time constants that can be varied by factors of 2. Fractional control of time constant can be achieved by altering
the slope of the transfer function stored within the lookup
table.
Reference
Hysteresis=Deadband-6dB
6dB
O
DVGA Input Power
Figure 10
Relationship between deadband and
hysteresis.
The AGC has several operating modes. The simplest is the
free-run mode where the loop is closed continuously and
the DVGA gain setting is constantly updated in response
The default serial output configuration is compatible with
the TMS320C54X serial input. Figure 11 shows the timing. To interface to the ‘C54X, set the DSP serial port in
continuous mode (FSM bit set to 0) with frame ignore
enabled (FIG bit set to 1). In this mode the 24-bit words
may be read as 3 groups of 8 bits. The overall input stream
of four 24-bit words is read as twelve 8-bit words for later
reassembly by the DSP.
The parallel outputs from the CLC5902 are also available
on the Eurocard connector J1. The parallel output bus of
96 clocks
6&.
6)6
$287
Figure 11
0
23 ... 1
0
0
23 ... 1
lsb
msb
lsb msb
I chan A
Q chan A
0
23 ... 1
msb
lsb
I chan B
23 ... 1
0
msb
lsb
Q chan B
DSP Interface Timing Diagram
Rev. 3.01 June 4, 1999
6
©1999 National Semiconductor Corporation
A simple inversion of the MSB converts two’s complement data to offset binary data. In this format the MSB has
the same polarity as all the other bits so that negative full
scale is all zeroes and positive full scale is all ones. An
inverter is provided on the board to generate this output
coding for the parallel output. The inverted MSB is
brought out on pin 3A of J1.
Refer to the CLC5902 data sheet for further information
on the parallel output.
Probing of DDC/AGC Debug Nodes
For optimal ADC performance the clock must have less
than 1psec jitter. Higher levels of jitter will spread out the
spectrum of any applied signals. In a laboratory environment, we suggest the use of a low phase noise synthesizer
such as the HP8643 or the HP8644 as a sinewave source.
Excessive phase noise will cause unacceptable levels of
jitter.
DRCS Control Panel Software
The DRCS Control Panel (drcscp.exe) requires Windows
95/98/NT and a free serial port to operate. Run setup.exe
from the CD ROM to copy the appropriate files to your
hard drive and build the necessary directory structure. Run
drcscp.exe to start the program. To configure the COM
port, choose &RQILJXUH,2 from the )LOH menu.
The DRCS Control Panel is a program interface which
allows the CLC5902 configuration registers to be programmed. All register settings are controlled from the four
tabs on the left. The 5HJLVWHUV page allows you to view a
summary of the register values that are down-loaded to the
CLC5902. Except for the 5HJLVWHUV page, each page has a
6HQG3DJH or 6HQG button. When pressed, the register values associated with that page are down-loaded to the
CLC5902. In addition, a 6HQG$OO'DWD command is available under the )LOH menu. Although the registers within the
CLC5902 can also be read, the present version of the software does not provide this capability.
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ol
et
The user has the ability to probe internal nodes within the
CLC5902 by selecting the desired node using the internal
configuration registers. The node is then switched on to
the 20-bit wide parallel debug bus which is a collection of
output pins that are re-assigned to this function when the
debug mode is enabled. (Refer to the CLC5902 data sheet
for pin assignments, output data formats, and configuration register parameters.) Both the DRCS Control Panel
and Data Capture Board support this mode.
removed. The CLK connector hooks to a sine-to-PECL
clock converter to drive the ADCs. This circuit requires a
2-3VPP (10 to 16dBm) sinewave at the clock SMA connector. The PECL clock is further converted to a TTL
clock for use by DDC/AGC.
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the CLC5902 is 16 bits wide and a set of enable and
address lines allow the I/Q data from channels A and B to
be accessed from 8 internal registers. These control lines
also connect to J1. A set of DIP switches SW1D allow the
enable and address lines to be statically set. These
switches must be open if the Data Capture Board is
used for parallel data capture.
When this mode is enabled, signal pin SCK is re-configured as a data strobe with the proper timing for the
selected internal node. This gives the user the ability to
debug his design when trouble arises. The internal nodes
available for probing include the outputs of the mixers,
CIC filters, and AGC power detectors.
µController
O
The COP8 microcontroller contains preprogrammed data
to load into the CLC5902. When the board is powered up
or the reset switch is closed, the COP8 reads the 8-position
dip switch SW2 to determine which set of data to load.
The CLC5902 is loaded, the LEDs alternate briefly, and
the COP8 enters an idle loop awaiting further serial communication. To change the operating program in the
CLC5902, change the SW2 dip switch setting and press
the ’RESET’ switch. The new data is loaded and the COP8
again enters the idle loop.
The COP8 provides an RS-232 serial port for connection
to an external controller on connector J9. This port allows
the DRCS Control Panel software to access the DDC registers thus providing greater configuration flexibility.
System Clock
The DRCS Board is equipped with an SMA connector
labeled as CLK so that an external clock signal can be
applied. However, the board is factory-configured with an
on-board 52MHz crystal oscillator (Y2) and so the external clock signal is not needed. If the user wishes to use
an external clock, the socketed oscillator must first be
©1999 National Semiconductor Corporation
7
The configuration data entered into the various pages can
be written to a .dcp configuration file. This provides a convenient method of retrieving previous configurations
because these files can also be read into the DRCS Control
Panel. The file is ASCII and has one line for each byte that
is written to the CLC5902. The first column is the address
and the second is the data. Both are in hex format. The
/RDG&RQILJXUDWLRQ and 6DYH&RQILJXUDWLRQ commands can
be found under the )LOH menu.
When you start the DRCS Control Panel, it will load the
last used .dcp file within the Data subdirectory. If you have
not yet created one, it will look for default.dcp. If
default.dcp is not found, it will use a set of hard-coded
defaults for everything except FIR Filters F1 and F2. For
the filters, the program will search for default.f1 and
default.f2. If they are not found, zeros will be loaded for
the coefficients.
The data entry fields are designed to allow values to be
entered using pulldown menus or edit boxes in familiar
engineering terms, as opposed to the integer values that
are required by the CLC5902. The engineering values are
converted to the appropriate integer values and appear on
the 5HJLVWHUV page. For example, when -150.03 is entered
into )UHT, &KDQQHO$, the 5HJLVWHUV page displays the value
493095284 for )5(4B$. When the mouse is held over a
Rev. 3.01 June 4, 1999
data entry field, a balloon is displayed which describes the
function. If a value is entered that is outside the valid
range, a warning is displayed.
Output Page - 6&.5DWH must be selected low enough to
allow all serial bits to exit within one output sample
period. See the CLC5902 data sheet for further discussion.
For the most part, the data entry fields are intuitive given
an understanding of the CLC5902 data sheet. A few
exceptions are noted below:
Filter Data Page - The coefficient values for each of the
symmetric FIR filters can be manually entered or loaded
from an ASCII text file using the /RDG button. The file
must have a .f1 extension for ),5)LOWHU and a .f2 extension for ),5)LOWHU. The file format is one signed integer
coefficient per line and the number of lines must equal the
number of unique coefficients. Also, there must be no
blank space before the values in the files.
Channels Page - )UHT is the frequency of the NCO. You
can either enter the IF frequency at the ADC input or the
aliased frequency at the ADC output. To down-convert
without a phase inversion, enter the negative of the frequency of interest. For example, an IF frequency of
150.03MHz requires an entry of -150.03 for no phase
inversion. An alternative is to recognize that 150.03MHz
aliases to -5.97MHz when )&. is 52MHz and, for no
phase inversion, enter +5.97. )&. refers to the sample rate
of the DRCS Board, which has a factory default of
52MHz. 6FDOH refers to the bit shift prior to the CIC filter (Figure 5). 6FDOH&DOFXODWHG is calculated by the program and is the value required of 6FDOH to maintain the
gain of the DDC up to and including the CIC filter to unity
or just less. It changes when &,&'HFLPDWLRQ changes.
6FDOH$GMXVW is a bit shift value added to 6FDOH prior to
downloading to the CLC5902. You can enter either a positive or negative value with the restriction that 6FDOH$GMXVW
+ 6FDOH&DOFXODWHG fall within the range of 0 to +44 inclusive. A warning is issued for values entered outside this
range. *DLQ refers to the bit shift after the CIC filter (Figure 5).
There is no handshaking between the DRCS Board and the
PC. If the system is operating correctly, all the LEDs will
light during transmission and only LED1 will remain lit at
the completion of transmission. If the transmit sequence is
upset, reset the DRCS Board and re-send.
e
Data Capture Board Settings
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The Data Capture Board and companion software provides
the ability to capture data from the DRCS Board as well as
a variety of analog-to-digital converter products. When
used together, it is important that the settings of one board
do not conflict with those of the other. If any conflicts
occur, it will be with entries on the 2XWSXW page of the
DRCS Control Panel and often will result in the data being
unintelligible. The first step to ensure compatibility is by
making sure all switches on the Data Capture Board are
off. The next step is to obtain a copy of the Data Capture
Board documentation.
AGC Page - The popup menus for initial conditions and
gains refer to the gain of the DVGA. The loop dynamics
for the AGC are set in the lower left box. Press the Calculate button after entering values for 7KUHVKROG, 'HDGEDQG,
and 7LPH&RQVWDQW and the AGC lookup table values and
$*&B/223B*$,1 are computed.
Default Configuration and SW2 Settings
The CLC-DRCS-PCASM is shipped configured with an
on-board 52MHz crystal clock source. The LC noise filter
has an 18MHz bandwidth centered at 150MHz. These
SW2 Switch Settings (4321)
Register Name
0001
'(&B%<B
0010
0011
0100
0101
0110
47
3
7
47
47
47
47
0
0
0
0
0
0
0
O
'(&
0000
6&$/(
21
36
32
21
21
21
21
)5(4B$
-493,095,283a
-493,095,283
-493,095,283
0
-479,054,044b
-479,054,044
-479,054,044
)5(4B%
-493,095,283
-493,095,283
-493,095,283
0
-1,156,337,348c
-479,054,044
-1,156,337,348
',7+B$%
1
1
1
1
1
1
0
$*&B/223B*$,1
1d
1
1
1
1
1
1
'(%8*B(1
0
1
1
0
0
0
1
7$3B6(/
0
6 (F1 AI Input)
6 (F1 AI Input)
12 (NCO AI)
0
0
8 (NCO A
cosine)
Table 1
eCLC5902
configurations for SW2 segment 1 settings (continued in Table 2).
a. With FCK=52MHz, -493,095,283 (0xE29BF68D) provides an NCO frequency of -5.97MHz. FIN=150.03MHz aliases to 150.03MHz3*52MHz=-5.97MHz
b. With FCK=52MHz, -479,054,044 (0xE3723724) provides an NCO frequency of -5.8MHz.
c. With FCK=52MHz, -1,156,337,348 (0xBB13B13C) provides an NCO frequency of -14MHz.
d. Yields a loop time constant of 1.5µs for FCK=52MHz and either position of switch number 6.
e. See Table 3 for register values common to all SW2 configurations.
Rev. 3.01 June 4, 1999
8
©1999 National Semiconductor Corporation
SW2 Switch Settings (4321)
Register Name
0111
1000
1001
1010
1011
1100
'(&
47
23
1
47
47
23
'(&B%<B
0
1
0
0
0
1
6&$/(
21
25
40
21
21
25
)5(4B$
-479,054,044
-493,095,283
-493,095,283
0
0
-479,054,044
)5(4B%
-1,156,337,348
-493,095,283
-493,095,283
0
0
-1,156,337,348
',7+B$%
0
1
1
0
0
1
$*&B/223B*$,1
1
1
1
0a
1
1
'(%8*B(1
1
0
1
1
1
0
7$3B6(/
10 (NCO B
cosine)
0
6 (F1 AI Input)
12 (Mixer AI)
14 (Mixer BI)
0
Table 2
b
CLC5902 configurations for SW2 segment 1 settings (continued from Table 1).
apart from building their own interface. The set of configurations available with SW2 is described below. Requests
for configurations not presently available should be
directed to the factory.
et
values are designed to operate in combination with SW2
configured to 0000|0000 as discussed below.
e
a. Yields a loop time constant of 3.0µs for FCK=52MHz and either position of switch number 6.
b. See Table 3 for register values common to all SW2 configurations.
On power up (or on reset), the COP8 reads the value of
DIP switch SW2 and programs the CLC5902 configuration registers. SW2 can be thought of as being segmented
into two pieces. Segment 1 comprises switch positions 1
through 4. These program the CLC5902 as shown in Table
1 and Table 2. The CLC5902 register values that are common to all of these configurations are given in Table 3.
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ol
It is advised that the reader has a copy of the CLC5902
data sheet available while reading the following material
even though it is not necessary to fully understand that
document before using the DRCS Board. Immediate
results can be obtained most easily when the DRCS Board
is used in conjunction with the DRCS Control Panel software, Data Capture Board and the capture board software.
The DRCS Control Panel software allows a user to communicate with the DRCS Board using plain-English commands from a menu. If the user wishes to configure the
board without a PC, though, SW2 is the only other means
Register Name
Value
2
5$7(
1
6287B(1
1
6&.B32/
0
6)6B32/
0
5'<B32/
0
08;B02'(
1
3$&.('
1
)250$7
2 (24 bit)
3+$6(B$%
0
$B6285&(
0
%B6285&(
1
7(67B5(*
4096
O
*$,1B$%
Table 3
Segment 2 is comprised of the remaining switches, each of
which programs an independent function as shown in
Table 4. The CLC5902 data sheet should be referenced for
the F1/F2 filter coefficients corresponding to the STD Set
and the GSM Set coefficients. The AGC lookup table values corresponding to the two choices of AGC dynamics
are given in Table 5.
SW2 Switch Settings
Switch
Position
Function
F1/F2 Coefficient
Set
0
1
5
STD Set
GSM Set
AGC Dynamics
(Threshold/Deadband)
6
-12dB/12dB
-15dB/15dB
AGC Mode
7
Continuous
Burst
Dither
8
On
Off
a
Table 4
Common register values for
segment 1 of SW2.
©1999 National Semiconductor Corporation
a.
SW2 Segment 2 settings.
$*&B/223B*$,1 is controlled from segment 1. See
Table 1 and Table 2.
9
Rev. 3.01 June 4, 1999
Table 6 gives the configuration register values for each of
the AGC modes associated with switch position 7 as mentioned in Table 4.
Decimal Values (Hex)
Decimal Register
Address (Hex)
-12dB/-12dB
-15dB/-15dB
128 (0x80)
-88 (0xA8)
-82 (0xAE)
129 (0x81)
-88 (0xA8)
-82 (0xAE)
130 (0x82)
-75 (0xB5)
-68 (0xBC)
131 (0x83)
-66 (0xBE)
-60 (0xC4)
132 (0x84)
-61 (0xC3)
-54 (0xCA)
133 (0x85)
-56 (0xC8)
-49 (0xCF)
134 (0x86)
-53 (0xCB)
-46 (0xD2)
135 (0x87)
-50 (0xCE)
-43 (0xD5)
136 (0x88)
-47 (0xD1)
-40 (0xD8)
137 (0x89)
-42 (0xD6)
-36 (0xDC)
138 (0x8A)
-39 (0xD9)
-32 (0xE0)
139 (0x8B)
-36 (0xDC)
-29 (0xE3)
140 (0x8C)
-33 (0xDF)
-26 (0xE6)
141 (0x8D)
-29 (0xE3)
-22 (0xEA)
142 (0x8E)
-25 (0xE7)
-18 (0xEE)
143 (0x8F)
-22 (0xEA)
0 (0x00)
SW2 Switch Position 7
Settings
Register Name
-19 (0xED)
0 (0x00)
-15 (0xF1)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
0 (0x00)
153 (0x99)
0 (0x00)
20 (0x14)
154 (0x9A)
17 (0x11)
23 (0x17)
155 (0x9B)
20 (0x14)
26 (0x1A)
156 (0x9C)
22 (0x16)
29 (0x1D)
157 (0x9D)
27 (0x1B)
34 (0x22)
158 (0x9E)
30 (0x1E)
37 (0x25)
159 (0x9F)
34 (0x22)
40 (0x28)
145 (0x91)
146 (0x92)
147 (0x93)
148 (0x94)
149 (0x95)
150 (0x96)
151 (0x97)
O
152 (0x98)
Table 5
1
$*&B+2/'B,&
0
0
$*&B5(6(7B(1
0
0
$*&B)25&(
1
0
(;3B,1+
0
0
$*&B&2817
2815
2815
$*&B,&B$%
32
32
Register values corresponding to SW2
switch position 7.
e
Table 6
et
Any of these default configurations can be modified by
using the DRCS Control Panel software. See the DRCS
Control Panel Software section on page 7.
Initial Operation
This procedure will verify proper operation of the DRCS
Board and Data Capture Board
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144 (0x90)
0
It is assumed that the you will be conducting this test in
conjunction with the Data Capture Board. If not, you will
have to solve the problem of data capture. Refer to the
CLC5902 data sheet to understand its data capture requirements. The sequence below requires an unmodulated
source such as an HP8643 or the HP8644.
AGC lookup table values for the two AGC
dynamics options.
For either selection, a loop time constant τ of 1.5µs results
when $*&B/223B*$,1 and F CK =52MHz. Each
increase of $*&B/223B*$,1 by 1 will decrease τ by a
factor of 2. Halving FCK will increase τ by a factor of 2.
Rev. 3.01 June 4, 1999
10
1.
If you have not already done so, install the DRCS
Control Panel and Data Capture Board software.
2.
Connect +5V to VCC and ground to GND of connector J3 on the Data Capture Board. When the
boards are connected together in the next step, these
connections will power both boards. Note that VEE
is not required because neither board needs a negative power supply.
3.
Connect J1 of the DRCS Board to J1 of the Data
Capture Board.
4.
Connect a serial cable from the PC to J9 on the
DRCS Board.
5.
If two serial ports are available on the PC, connect
the other to J9 of the Data Capture Board. If not, the
single port will have to be shared.
6.
Make sure that all DIP switches on both boards are
set to off.
7.
Turn on the power supply.
8.
Start the DRCS Control Panel and Data Capture
Board software.
9.
Configure the COM ports for the DRCS Control
Panel and Data Capture Board software. The COM
©1999 National Semiconductor Corporation
port setup for the DRCS Control Panel is located
under )LOH, &RQILJXUH,2. The COM port setup for
the Data Capture Board software is accessed by
right-mouse-button clicking anywhere on the program window and selecting &RQILJXUH,2. Note that
power must be applied to the Data Capture Board
and the serial cable must be connected in order for
the software to accept the COM port configuration.
10. Connect a -10dBm sinewave at 150.00MHz to the
DRCS Board AIN1 input.
Screen configuration for step 12.
%LWV box. Press 2. The screen should appear as in
Figure 13.
13. Press 6WDUW on the front panel of the Data Capture
Board software window. When the completion bar
reaches 100%, the captured data will be written to
the file C:\TEMP\DATA.DAT.
et
The first measurement will be to use the debug mode of
the CLC5902 to probe the output of the ADC.
Figure 13
e
The DVGA should ser vo to a gain of either 0dB
(AGAIN=2) or +6dB (AGAIN=3) and the ADC should be
operating at a level of -16 or -10dBFS. Because (;3B,1+
is not asserted for this configuration, the DDC output
(which will be observed below) should be at -32dBFS.
This can be computed from the gain equations presented
earlier and the register data provided in the 5HJLVWHUV page
of the DRCS Control Panel.
If the TEMP directory did not previously exist, the software will create it. You can also specify a different file
name and directory by right-mouse-button-clicking on the
Data Capture Board software window and choosing the
&KDQJH'DWD)LOH command.
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11. On the &KDQQHOV page of the DRCS Control Panel,
enter 0 for )UHT within the &KDQQHO$ box to set the
frequency of the channel A NCO to zero. Also
check 'HEXJ(QDEOHG and select 0L[HU$, from the
3UREHDW pulldown menu within the &RPPRQ box.
The screen should appear as in Figure 12 Click on
the 6HQG3DJH button. Immediately following this, a
data transfer indicator box will appear on the monitor and all the LEDs on the DRCS Board will light
momentarily.
O
12. On the &RQILJXUH&DSWXUH screen of the Data Capture Board software, choose &DSWXUH'HEXJwithin
the 0RGH box. Then choose 8SSHU%LWV within the
The values in DATA.DAT represent 24-bit 2’s complement
integers. When 0L[HU$, is selected, only the upper 15 bits
are non-zero. These numbers can be converted to signed
fractional values using the following MATLAB script:
ORDGF?WHPS?GDWDGDW
GDWD GDWDA
GDWD GDWDGDWDGDWDGDWD! Verify that the waveform is sinusoidal with amplitude of
either -16 or -10dBFS and frequency of 150MHz(3*52MHz) = -6MHz.
The next measurement will be to observe the output of the
DDC.
14. On the &KDQQHOV page of the DRCS Control Panel,
enter -150.03 for )UHT of &KDQQHO$, uncheck 'HEXJ
(QDEOHG. The screen should appear as in Figure 14.
Click on the 6HQG3DJH button.
15. Choose &DSWXUH within the 0RGH box of the &RQILJ
XUH&DSWXUH screen of the Data Capture Board software. Then choose %LWV within the %LWV box and
&DSWXUHVW%LW within the VW%LW box. Finally,
choose &KDQQHO$ from the &KDQQHO box and press
2.. The screen should appear as in Figure 15.
Figure 12
16. Click 6WDUW on the front panel of the Data Capture
Board software window.
Screen configuration for step 11.
©1999 National Semiconductor Corporation
11
Rev. 3.01 June 4, 1999
DDC Large-Signal Nonlinearity Exercise
This exercise is intended to illustrate the two types of
large-signal nonlinearity that can be encountered when the
CLC5902 is incorrectly configured. Both can be observed
at the input of filter F1. The same equipment is used as in
the Initial Operation section on page 10.
Screen configuration for step 14.
Connect a -10dBm sinewave at 150.000MHz to the
DRCS Board AIN1 input.
2.
Load default.dcp by choosing /RDG &RQILJXUDWLRQ
from the )LOH menu of the DRCS Control Panel.
3.
On the &KDQQHOV page, enter -150.005 for )UHT within the &KDQQHO$ box and enter 6 for 6FDOH$GMXVW
within the &RPPRQ box. Also check 'HEXJ(QDEOHG
and select ),Q$, from the 3UREHDW pulldown
menu. Click on the 6HQG3DJH button.
4.
On the &RQILJXUH&DSWXUH screen of the Data Capture Board software, choose &DSWXUH'HEXJ within
the 0RGH box and %LWV from the %LWV box. Click
on 2..
Press 6WDUW on the front panel of the Data Capture
Board software window.
et
5.
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Figure 14
1.
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As before, the values in DATA.DAT represent 24-bit 2’s
complement integers and only the upper 18 bits are nonzero. After conversion to signed values, the first 300
points when plotted look like Figure 16. This distortion is
1
0.8
0.6
0.4
0.2
Figure 15
Screen configuration for step 15.
0
O
The values in the file again represent 24-bit 2’s complement integers except now all 24 bits are non-zero. The
same MATLAB script can be used to convert to signed
fractional values. Regardless of the true width of the
word being captured, the Data Capture Board will
always write 24-bit, 2s complement numbers to
DATA.DAT. The only exception to this is when probing
$*&&,&$% in which case each number represents two
appended 9 bit numbers. (Refer to the CLC5902 data
sheet.)
Ve r if y t h a t t h e o u tp u t i s - 3 2 d B F S a t f r e q u e n c y
150.00MHz-150.03MHz = -0.03MHz. A slight frequency
offset may exist due to variations in the frequency of the
on-board 52MHz crystal oscillator. Note that the output
sample rate is 52MHz/192 = 270.8KHz. If you perform an
FFT you will see the CLC5902’s filter bandwidth reflected
in the shape of the noise floor.
17. Repeat steps 10 through 13 for input AIN2 replacing all occurrences of &KDQQHO$with &KDQQHO%.
This completes the verification of the board operation.
Rev. 3.01 June 4, 1999
12
-0.2
-0.4
-0.6
-0.8
-1
0
Figure 16
50
100
150
200
250
300
CIC overflow distortion.
caused by overflow in the CIC filter due to 6&$/( being
set too large. This overflow cannot be sensed and the only
way to avoid it is by making sure that 6&$/( is set consistent with the chosen CIC decimation value so that the CIC
output is less than full scale. Figure 16 may not look
exactly as yours. The exact look depends greatly on the
frequency error between the on-board clock oscillator and
the input source. The important characteristic of the distortion is that the positive sinusoid peaks have been translated
©1999 National Semiconductor Corporation
to negative values and the negative peaks to positive values.
Pin
J1 A
J1 B
Go back to the &KDQQHOV page of the DRCS Control
Panel and change 6FDOH$GMXVW back to 0. Next, select G% from the *DLQ pulldown menu in the
&KDQQHO$ box. Click on 6HQG3DJH.
7
N/C
D11_T
8
N/C
D10_T
9
N/C
D9_T
10
N/C
D8_T
Press 6WDUW on the front panel of the Data Capture
Board software window.
11
N/C
D7_T
12
N/C
D6_T
Convert the numbers in DATA.DAT to signed values and
plot the first 300 points. You should see the clipping as
shown in Figure 17. This represents the type of nonlinearity at all stages of the DDC other than within the CIC filter.
13
N/C
D5_T
14
N/C
D4_T
15
N/C
D3_T
16
N/C
D2_T
17
N/C
D1_T
18
N/C
LSB_T
19
GND
GND
20
N/C
RDY
21
SFS
SCK
22
BOUT
AOUT
0.4
23
POUT_SEL2
N/C
0.2
24
POUT_SEL1
N/C
25
POUT_SEL0
RDY
26
POUT_EN
AGC_EN
27
GND
GND
28
GND
GND
6.
7.
1
e
0.8
et
0.6
0
-0.2
-0.4
-0.8
-1
0
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-0.6
50
100
150
200
250
29
N/C
N/C
30
N/C
N/C
31
+5V (DIGITAL)
+5V (DIGITAL)
32
+5V (ANALOG)
+5V (ANALOG)
300
Table 7
Figure 17
Eurocard connector J1 pinout.
Data path saturation at the input of F1.
Pin
This completes this exercise.
O
Connector Pinouts
Table 7 describes the 64-pin Eurocard connector (J1)
pinouts on the DRCS Board. Table 8 describes 10-pin
JTAG header and 16-pin DSP header pinouts. The schematics provide the pinout for J9, a female DB-9 used to
connect the standard RS-232 serial cable from the PC.
Power is supplied through J1. If the Data Capture Board is
connected to J1, power must be connected to the power
connector on the Data Capture Board.
Pin
J1 A
J1 B
JTAG
DSP
1
TCK
N/C
2
GND
GND
3
TDO
SCK
4
VCC
GND
5
TMS
BFSR
6
N/C
GND
7
TRST
BDR
8
SCAN_EN
GND
9
TDI
GND
10
GND
GND
11
N/C
1
N/C
N/C
12
GND
2
GND
GND
13
N/C
3
MSB_T
MSB_F
14
GND
4
N/C
D14_T
15
N/C
5
N/C
D13_T
16
GND
6
N/C
D12_T
Table 7
Table 8
JTAG and DSP header pinouts.
Eurocard connector J1 pinout.
©1999 National Semiconductor Corporation
13
Rev. 3.01 June 4, 1999
Schematics
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Figure 18, Figure 19, Figure 20, and Figure 21 are the
CLC-DRCS-PCASM schematics.
Figure 18
ADC Input AIN1
Rev. 3.01 June 4, 1999
14
©1999 National Semiconductor Corporation
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Figure 19
ADC Input AIN2
©1999 National Semiconductor Corporation
15
Rev. 3.01 June 4, 1999
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Figure 20
CLC5902 Dual Digital Tuner/AGC
Rev. 3.01 June 4, 1999
16
©1999 National Semiconductor Corporation
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Figure 21
COP8 Microprocessor
©1999 National Semiconductor Corporation
17
Rev. 3.01 June 4, 1999
PC Board Layout
Silk screen parts placement drawings are shown below.
The complete board layout package can also be provided.
Primary areas of concern are the analog inputs to the ADC
and the ADC digital outputs.
Care has been exercised to prevent ground loops and noise
coupling on the circuit board at the inputs.
Figure 22 and Figure 23 show the DRCS parts placement.
Figure 24, Figure 25, Figure 26, and Figure 27 show the
PC board layers.
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The ADC outputs have been kept as short as possible to
minimize capacitive loading. The internal ground plane
has been removed under these traces to reduce the parasitic capacitance. Higher capacitance values will load the
ADC output drivers causing additional noise on the internal analog signals. This will degrade the ADC performance. Analog and digital grounds have been star
connected to minimize crosstalk. The supplies have series
inductors for each section to provide as much isolation as
is practical.
Figure 22
DRCS Board layout, top.
Rev. 3.01 June 4, 1999
18
©1999 National Semiconductor Corporation
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DRCS Board layout, bottom.
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Figure 23
©1999 National Semiconductor Corporation
19
Rev. 3.01 June 4, 1999
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DRCS Board layout, L1.
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Figure 24
Figure 25
DRCS Board layout, L2.
Rev. 3.01 June 4, 1999
20
©1999 National Semiconductor Corporation
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DRCS Board layout, L3.
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Figure 26
Figure 27
DRCS Board layout, L4.
©1999 National Semiconductor Corporation
21
Rev. 3.01 June 4, 1999
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CLC-DRCS-PCASM
DRCS Evaluation Board User’s Guide
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National Semiconductor Customer Response Group at 1-800-272-9959 or fax 1-800-737-7018.
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1.
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©1999 National Semiconductor Corporation
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Rev. 3.01 June 4, 1999
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