參數(shù)資料
型號(hào)： CLC5902VLA
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 調(diào)諧器
英文描述： Dual Digital Tuner/AGC
中文描述： 1-BAND, AUDIO TUNER, PQFP128
封裝： PLASTIC, QFP-128
文件頁(yè)數(shù)： 14/28頁(yè)
文件大?。?/td> 783K
代理商： CLC5902VLA
Rev. 3.05 May 27, 1999
14
1999 National Semiconductor Corporation
Oscillator (NCO) circuit to generate sine and cosine sig-
nals used by the digital mixer. The NCOs can be synchro-
nized with NCOs on other chips via the sync pin
SI
. This
allows multiple down converter outputs to be coherently
combined, each with a unique phase and amplitude.
The tuning frequency is set by loading the FREQ register
according to the formula FREQ = 2
32
F/F
CK
, where F is
the desired tuning frequency and F
CK
is the chip’s clock
rate. FREQ is a 2’s complement word. The range for F is
from -F
CK
/2 to +F
CK
(1-2
-31
)/2.
In some cases the sampling process causes the order of the
I and Q components to be reversed. Should this occur sim-
ply invert the polarity of the tuning frequency F.
The 2’s complement format represents full-scale negative
as 10000000 and full-scale positive as 01111111 for an 8-
bit example.
The 16 bit phase offset is set by loading the PHASE regis-
ter according to the formula PHASE = 2
16
P/2
π
, where P
is the desired phase in radians ranging between 0 and 2
π
.
PHASE is an unsigned 16-bit number. P ranges from 0 to
2
π
(1-2
-16
).
Phase dithering can be enabled to reduce the spurious sig-
nals created by the NCO due to phase truncation. This
truncation is unavoidable since the frequency resolution is
much finer than the phase resolution. With dither enabled,
spurs due to phase truncation are below -100 dBc for all
frequencies and phase offsets. Each NCO has its own
dither source and the initial state of one is maximally off-
set with respect to the other so that they are effectively
uncorrelated. The phase dither sources are on by default.
They are independently controlled by the DITH_A and
DITH_B bits. The amplitude resolution of the ROM cre-
ates a worst-case spur amplitude of -101dBc rendering
amplitude dither unnecessary.
The spectrum plots in Figure 16 show the effectiveness of
phase dither in reducing NCO spurs due to phase trunca-
tion for a worst-case example (just below F
S
/8). With
dither off, the spur is at -86.4dBFS. With dither on, the
spur is below -125dBFS, disappearing into the noise floor.
This spur is spread into the noise floor which results in an
SNR of -83.6dBFS.
Figure 17 shows the spur levels as the tuning frequency is
scanned over a narrow portion of the frequency range. The
spurs are again a result of phase quantization but their
locations move about as the frequency scan progresses. As
before, the peak spur level drops when dithering is
enabled. When dither is enabled and the fundamental fre-
quency is exactly at F
S
/8, the worst-case spur due to
amplitude quantization can be observed at -101dBc in Fig-
ure 18.
Four Stage CIC Filter
The mixer outputs are decimated by a factor of N in a four
stage CIC filter. N is programmable to any integer
between 8 and 2048. Decimation is programmed in the
DEC register where DEC = N - 1. The programmable dec-
imation allows the chip’s usable output bandwidth to range
from about 2.6kHz to 1.3MHz when the input data rate
(which is equal to the chip’s clock rate, F
CK
) is 52 MHz. A
block diagram of the CIC filter is shown in Figure 19.
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-160
-140
-120
-100
-80
-60
-40
-20
0
Frequency Normalized to F
S
M
Figure 17
NCO Spurs due to Phase Quantization
Complex NCO Output
Phase Dither Disabled
NCO frequency swept through F
S
/8
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-160
-140
-120
-100
-80
-60
-40
-20
0
Frequency Normalized to F
S
M
Figure 18
Worst Case Amplitude Spur, NCO at F
S
/8
Complex NCO Output
Phase Dither Enabled
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參數(shù)描述
CLC5903 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual Digital Tuner / AGC
CLC5903CISM/NOPB 功能描述:上下轉(zhuǎn)換器 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128
CLC5903SM 功能描述:上下轉(zhuǎn)換器 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128
CLC5903SM/NOPB 功能描述:上下轉(zhuǎn)換器 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128
CLC5903VLA 功能描述:上下轉(zhuǎn)換器 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128
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