DataSheet.in

AN189 डेटा पत्रक PDF( Datasheet डाउनलोड )


डेटा पत्रक - Balanced Modulator / Demodulator Applications - Philips

भाग संख्या AN189
समारोह Balanced Modulator / Demodulator Applications
मैन्युफैक्चरर्स Philips 
लोगो Philips लोगो 
पूर्व दर्शन
1 Page
		
<?=AN189?> डेटा पत्रक पीडीएफ

AN189 pdf
Philips Semiconductors
Balanced modulator/demodulator applications using
the MC1496/1596
Application note
AN189
freedom to choose gain, current levels, and power supplies. The
device can be operated with single-ended or dual supplies.
+6V
1.5k
1.5k
RS
RS
2.2k RS
2.2k
RS
GAIN
SELECT
500 500
500
NOTE:
All resistor values are in ohms
-6V SR00776
Figure 3. Dual Supply Biasing
VBIAS = VBE = 500 × IS
where IS is the current set in the current sources.
For the example VBE is 700mV at room temperature and the bias
voltage at Pin 5 becomes 1.7V. Because of the cascode
configuration, both the collectors of the current sources and the
collectors of the signal transistors must have some voltage to
operate properly. Hence, the remaining voltage of the negative
supply (–6V+1.7V=–4.3V) is split between these transistors by
biasing the signal transistor bases at –2.15V. Countless other bias
arrangements can be used with other power supply voltages. The
important thing to remember is that sufficient DC voltage is applied
to each bias point to avoid collector saturation over the expected
signal wings.
BALANCED MODULATOR
In the primary application of balanced modulation, generation of
double sideband suppressed carrier modulation is accomplished.
Due to the balance of both modulation and carrier inputs, the output,
as mentioned, contains the sum and difference frequencies while
attenuating the fundamentals. Upper and lower sideband signals are
the strongest signals present with harmonic sidebands being of
diminishing amplitudes as characterized by Figure 4.
Gain of the 1496 is set by including emitter degeneration resistance
located as RE in Figure 5. Degeneration also allows the maximum
signal level of the modulation to be increased. In general, linear
response defines the maximum input signal as
Vs 15 RE (Peak)
and the gain is given by
AVS
+
RE
RL
) 2re
(2)
This approximation is good for high levels of carrier signals. Table 1
summarizes the gain for different carrier signals.
As seen from Table 1, the output spectrum suffers an amplitude
increase of undesired sideband signals when either the modulation
or carrier signals are high. Indeed, the modulation level can be
increased if RE is increased without significant consequence.
However, large carrier signals cause odd harmonic sidebands
(Figure 4) to increase. At the same time, due to imperfections of the
carrier waveforms and small imbalances of the device, the second
harmonic rejection will be seriously degraded. Output filtering is
often used with high carrier levels to remove all but the desired
sideband. The filter removes unwanted signals while the high carrier
level guards against amplitude variations and maximizes gain.
Broadband modulators, without benefit of filters, are implemented
using low carrier and modulation signals to maximize linearity and
minimize spurious sidebands.
NOTES:
FREQUENCY
fC Carrier Fundamental
fS Modulating Signal
fC ± fS Fundamental Carrier Sidebands
fC ± nfS Fundamental Carrier Sideband Harmonics
nfC Carrier Harmonics
nfC ± nfS Carrier Harmonic Sidebands
Figure 4. Modulator Frequency Spectrum
1988 May
2
SR00777

विन्यास 5 पेज
डाउनलोड[ AN189 Datasheet.PDF ]


शेयर लिंक


अनुशंसा डेटापत्रक

भाग संख्याविवरणविनिर्माण
AN180Frequency SynthesisPhilips
Philips
AN1801FSK DecoderPhilips
Philips


भाग संख्याविवरणविनिर्माण
30L120CTSchottky RectifierPFC Device
PFC Device
AT28C010-12DKSpace 1-MBit (128K x 8) Paged Parallel EEPROMATMEL
ATMEL
B20NM50FDN-CHANNEL POWER MOSFETSTMicroelectronics
STMicroelectronics
D8442SD844SavantIC
SavantIC
FAE391-A20AM/FM Automotive Electronic TunerMitsumi
Mitsumi


Index : 0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z



www.DataSheet.in    |   2017   |  संपर्क   |   खोज     |   English