- 您現在的位置：買賣IC網 > PDF目錄372107 > SA624D (NXP SEMICONDUCTORS) High performance low power FM IF system with high-speed RSSI PDF資料下載
參數資料
| 型號： | SA624D |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 接收器 |
| 英文描述： | High performance low power FM IF system with high-speed RSSI |
| 中文描述： | FM, AUDIO DEMODULATOR, PDSO16 |
| 封裝： | 3.90 MM, PLASTIC, SOT-109-1, MS-012AC, SO-16 |
| 文件頁數： | 10/15頁 |
| 文件大小： | 161K |
| 代理商： | SA624D |
Philips Semiconductors
Product specification
SA624
High performance low power FM IF system with
high-speed RSSI
1997 Nov 07
10
φ
=
∠
V
O
-
∠
V
IN
=
(2)
t
g-1
ω
1
Q
1
ω
(
ω
–
2
)
ω
1
1
Figure 12 is the plot of
φ
vs.
ω
ω
1
(
)
It is notable that at
ω
=
ω
1
, the phase shift is
π
2
φ
ω
The signal V
O
would have a phase shift of
2Q
1
ω
2
If V
IN
= A Sin
ω
t
V
O
= A
ω
t +
π
2
and the response is close to a straight
line with a slope of
=
ω
1
2Q
1
–
ω
1
π
with respect to the V
IN
.
Sin
(3)
ω
–
ω
1
2Q
1
Multiplying the two signals in the mixer, and
low pass filtering yields:
V
IN
V
O
= A
2
Sin
ω
t
ω
t +
π
2
after low pass filtering
Sin
(4)
ω
–
ω
1
2Q
1
Cos
(5)
ω
V
OUT
=
π
2
–
ω
1
)
ω
1
+
ω
2Q
1
1
2
A
2
=1
2A
2
Sin
ω
1
ω
ω
1
(
2Q
1
(
(6)
V
OUT
∝
2Q
1
2Q
1
ω
1
=
ω
)
For
2Q
1
ω
ω
1
<<
π
2
Which is discriminated FM output. (Note that
ω
is the deviation
frequency from the carrier
ω
1
.
Ref. Krauss, Raab, Bastian; Solid State Radio Eng.; Wiley, 1980, p.
311. Example: At 455kHz IF, with +5kHz FM deviation. The
maximum normalized frequency will be
455 +5kHz
455
= 1.010 or 0.990
Go to the f vs. normalized frequency curves (Figure 12) and draw a
vertical straight line at
ω
ω
1
= 1.01.
The curves with Q = 100, Q = 40 are not linear, but Q = 20 and less
shows better linearity for this application. Too small Q decreases
the amplitude of the discriminated FM signal. (Eq. 6)
Choose a
Q = 20
The internal R of the 624 is 40k. From Eq. 1c, and then 1b, it results
that
C
P
+ C
S
= 174pF and L = 0.7mH.
A more exact analysis including the source resistance of the
previous stage shows that there is a series and a parallel resonance
in the phase detector tank. To make the parallel and series
resonances close, and to get maximum attenuation of higher
harmonics at 455kHz IF, we have found that a C
S
= 10pF and C
P
=
164pF (commercial values of 150pF or 180pF may be practical), will
give the best results. A variable inductor which can be adjusted
around 0.7mH should be chosen and optimized for minimum
distortion. (For 10.7MHz, a value of C
S
= 1pF is recommended.)
Audio Outputs
Two audio outputs are provided. Both are PNP current-to-voltage
converters with 55k
nominal internal loads. The unmuted output
is always active to permit the use of signaling tones in systems such
as cellular radio. The other output can be muted with 70dB typical
attenuation. The two outputs have an internal 180
°
phase
difference.
The nominal frequency response of the audio outputs is 300kHz.
this response can be increased with the addition of external
resistors from the output pins to ground in parallel with the internal
55k resistors, thus lowering the output time constant. Singe the
output structure is a current-to-voltage converter (current is driven
into the resistance, creating a voltage drop), adding external parallel
resistance also has the effect of lowering the output audio amplitude
and DC level.
This technique of audio bandwidth expansion can be effective in
many applications such as SCA receivers and data transceivers.
Because the two outputs have a 180
°
phase relationship, FSK
demodulation can be accomplished by applying the two output
differentially across the inputs of an op amp or comparator. Once
the threshold of the reference frequency (or “no-signal” condition)
has been established, the two outputs will shift in opposite directions
(higher or lower output voltage) as the input frequency shifts. The
output of the comparator will be logic output. The choice of op amp
or comparator will depend on the data rate. With high IF frequency
(10MHz and above), and wide IF bandwidth (L/C filters) data rates in
excess of 4Mbaud are possible.
RSSI
The “received signal strength indicator”, or RSSI, of the SA624
demonstrates monotonic logarithmic output over a range of 90dB.
The signal strength output is derived from the summed stage
currents in the limiting amplifiers. It is essentially independent of the
IF frequency. Thus, unfiltered signals at the limiter inputs, spurious
products, or regenerated signals will manifest themselves as RSSI
outputs. An RSSI output of greater than 250mV with no signal (or a
very small signal) applied, is an indication of possible regeneration
or oscillation.
In order to achieve optimum RSSI linearity, there must be a 12dB
insertion loss between the first and second limiting amplifiers. With
a typical 455kHz ceramic filter, there is a nominal 4dB insertion loss
in the filter. An additional 6dB is lost in the interface between the
filter and the input of the second limiter. A small amount of
additional loss must be introduced with a typical ceramic filter. In the
test circuit used for cellular radio applications (Figure 5) the optimum
linearity was achieved with a 5.1k
resistor from the output of the
first limiter (Pin 14) to the input of the interstage filter. With this
resistor from Pin 14 to the filter, sensitivity of 0.25
μ
V for 12dB
SINAD was achieved. With the 3.6k
resistor, sensitivity was
optimized at 0.22
μ
V for 12dB SINAD with minor change in the RSSI
linearity.
Any application which requires optimized RSSI linearity, such as
spectrum analyzers, cellular radio, and certain types of telemetry,
相關PDF資料 |
PDF描述 |
|---|---|
| SA624 | High performance low power FM IF system with high-speed RSSI |
| SA626D | ECONOLINE: RB & RA - Dual Output from a Single Input Rail- Power Sharing on Output- Industry Standard Pinout- 1kVDC & 2kVDC Isolation- Custom Solutions Available- UL94V-0 Package Material- Efficiency to 85% |
| SA626DK | Low voltage high performance mixer FM IF system with high-speed RSSI |
| SA626 | Low voltage high performance mixer FM IF system with high-speed RSSI |
| SA630N | Single pole double throw SPDT switch |
相關代理商/技術參數 |
參數描述 |
|---|---|
| SA625 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:High performance low power mixer FM IF system with high-speed RSSI |
| SA625DK | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:High performance low power mixer FM IF system with high-speed RSSI |
| SA626 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low voltage high performance mixer FM IF system with high-speed RSSI |
| SA626A | 功能描述:MODULE SKT ADAPTER 20DIP/SSOP RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 適配器 系列:* 標準包裝:96 系列:- 模塊/板類型:TQFP 插座模塊 適用于相關產品:- |
| SA626D | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low voltage high performance mixer FM IF system with high-speed RSSI |
發(fā)布緊急采購，3分鐘左右您將得到回復。