Carrier Suppression
Carrier suppression is defined as the ratio of each
sideband output to carrier output for the carrier and signal
voltage levels specified.
Carrier suppression is very dependent on carrier input
level, as shown in Figure 22. A low value of the carrier does
not fully switch the upper switching devices, and results in
lower signal gain, hence lower carrier suppression. A higher
than optimum carrier level results in unnecessary device and
circuit carrier feedthrough, which again degenerates the
suppression figure. The MC1496 has been characterized
with a 60 mVrms sinewave carrier input signal. This level
provides optimum carrier suppression at carrier frequencies
in the vicinity of 500 kHz, and is generally recommended for
balanced modulator applications.
Carrier feedthrough is independent of signal level, VS.
Thus carrier suppression can be maximized by operating
with large signal levels. However, a linear operating mode
must be maintained in the signal−input transistor pair −or
harmonics of the modulating signal will be generated and
appear in the device output as spurious sidebands of the
suppressed carrier. This requirement places an upper limit
on input−signal amplitude (see Figure 20). Note also that an
optimum carrier level is recommended in Figure 22 for good
carrier suppression and minimum spurious sideband
generation
Carrier SuppressionCarrier suppression is defined as the ratio of eachsideband output to carrier output for the carrier and signalvoltage levels specified.Carrier suppression is very dependent on carrier inputlevel, as shown in Figure 22. A low value of the carrier doesnot fully switch the upper switching devices, and results inlower signal gain, hence lower carrier suppression. A higherthan optimum carrier level results in unnecessary device andcircuit carrier feedthrough, which again degenerates thesuppression figure. The MC1496 has been characterizedwith a 60 mVrms sinewave carrier input signal. This levelprovides optimum carrier suppression at carrier frequenciesin the vicinity of 500 kHz, and is generally recommended forbalanced modulator applications.Carrier feedthrough is independent of signal level, VS.Thus carrier suppression can be maximized by operatingwith large signal levels. However, a linear operating modemust be maintained in the signal−input transistor pair −orharmonics of the modulating signal will be generated andappear in the device output as spurious sidebands of thesuppressed carrier. This requirement places an upper limiton input−signal amplitude (see Figure 20). Note also that anoptimum carrier level is recommended in Figure 22 for goodcarrier suppression and minimum spurious sidebandgeneration
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Carrier Suppression
Carrier suppression is defined as the ratio of each
sideband output to carrier output for the carrier and signal
voltage levels specified.
Carrier suppression is very dependent on carrier input
level, as shown in Figure 22. A low value of the carrier does
not fully switch the upper switching devices, and results in
lower signal gain, hence lower carrier suppression. A higher
than optimum carrier level results in unnecessary device and
circuit carrier feedthrough, which again degenerates the
suppression figure. The MC1496 has been characterized
with a 60 mVrms sinewave carrier input signal. This level
provides optimum carrier suppression at carrier frequencies
in the vicinity of 500 kHz, and is generally recommended for
balanced modulator applications.
Carrier feedthrough is independent of signal level, VS.
Thus carrier suppression can be maximized by operating
with large signal levels. However, a linear operating mode
must be maintained in the signal−input transistor pair −or
harmonics of the modulating signal will be generated and
appear in the device output as spurious sidebands of the
suppressed carrier. This requirement places an upper limit
on input−signal amplitude (see Figure 20). Note also that an
optimum carrier level is recommended in Figure 22 for good
carrier suppression and minimum spurious sideband
generation
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