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參數資料
| 型號： | SA614A |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | Low power FM IF system |
| 中文描述： | 低功耗調頻中頻系統(tǒng) |
| 文件頁數： | 10/14頁 |
| 文件大小： | 216K |
| 代理商： | SA614A |
Philips Semiconductors
Product specification
SA614A
Low power FM IF system
1997 Nov 07
10
From the above equation, the phase shift between nodes 1 and 2, or
the phase across C
S
will be:
ω
1
Q
1
ω
(
1
φ
=
∠
V
O
-
∠
V
IN
=
(2)
t
g-1
ω
–
2
)
ω
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
ω
1
ω
ω
1
(
2Q
1
(
(6)
V
OUT
∝
2Q
1
2Q
1
ω
1
=
)
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 614A 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 SA614A
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
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相關代理商/技術參數 |
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| SA614AD | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Low power FM IF system |
| SA614AD,118 | 功能描述:射頻放大器 LOW POWER FM IF SYSTEM RoHS:否 制造商:Skyworks Solutions, Inc. 類型:Low Noise Amplifier 工作頻率:2.3 GHz to 2.8 GHz P1dB:18.5 dBm 輸出截獲點:37.5 dBm 功率增益類型:32 dB 噪聲系數:0.85 dB 工作電源電壓:5 V 電源電流:125 mA 測試頻率:2.6 GHz 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 封裝:Reel |
| SA614AD,602 | 功能描述:射頻放大器 LOW POWER FM IF SYSTEM RoHS:否 制造商:Skyworks Solutions, Inc. 類型:Low Noise Amplifier 工作頻率:2.3 GHz to 2.8 GHz P1dB:18.5 dBm 輸出截獲點:37.5 dBm 功率增益類型:32 dB 噪聲系數:0.85 dB 工作電源電壓:5 V 電源電流:125 mA 測試頻率:2.6 GHz 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 封裝:Reel |
| SA614AD | 制造商:NXP Semiconductors 功能描述:IC FM IF SYSTEM SMD SOIC16 614 |
| SA614AD | 制造商:NXP Semiconductors 功能描述:IC FM IF SYSTEM SMD SOIC16 614 |
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