This is the generic class for demodulators. A demodulator
is a device which extracts an arbitrarily varying information carrying
signal from a signal formed by varying a characteristic of a repetitious
electrical or electromagnetic wave of less than infrared frequency
in accordance with this information carrying signal. Classification
herein is broadly by the type of modulation exhibited by the input
signal.
B. COMBINATIONS WITH BASIC SUBJECT MATTER INCLUDED
IN THIS CLASS
1. A demodulator combined with perfecting structure
is classified here. Such structure might include, for
example, a particular power supply for electronic devices within
the demodulator.
2. A demodulator combined with or incorporated in other
structure not otherwise classifiable is classified here.
This might include, for example, a demodulator combined
with an acoustical device such as a loudspeaker.
3. A combination including both a modulator and
a demodulator is classified elsewhere. See Lines With Other
Classes and Within This Class, below.
C. MISCELLANEOUS SYSTEMS AND DEVICES USED WITH DEMODULATORS
This class provides for (1) miscellaneous
systems and devices which are not of general utility and which are limited
to use with demodulators and (2) miscellaneous systems
and devices useful with demodulators which are not otherwise classified.
An example of this would be convertible demodulators which convert
between different types of demodulators or which convert to or from
devices other than demodulators.
SECTION II - LINES WITH OTHER CLASSES AND WITHIN THIS CLASS
A combination including both a modulator and a demodulator
is classified in Class 332where
such combination is not provided for elsewhere.
Excluded from this class are pulse code demodulators and delta
modulation demodulators which are now classified elsewhere. See
References to other Classes, below.
Several classes contain structure which is closely analogous
to demodulators. Particularly significant among these
is the art in the class for miscellaneous active electrical nonlinear
devices, circuits, and systems. See
the relevant SEARCH CLASS notes below in References to Other Classes
in completing the search for subject matter of Class 329.
Many classes contain subject matter which includes demodulators
or analogous devices as subcombinations thereof. Among
these are receivers and complete communication systems (i.e., transmitters
and receivers). (See References to Other
Classes, below.)Therefore, these
classes and others contained in the SEARCH CLASS notes below in
References to Other Classes, should be considered in completing
the search for subject matter of Class 329.
The terms "discriminator" and "detector" are often but not
always used synonymously with "demodulator". Classification
in Class 329 is appropriate where the terms "discriminator" or "detector"
are recited and which clearly disclose a corresponding function
of demodulation per the definition above. Classification
is elsewhere where no such disclosure is present. See
the SEARCH CLASS notes below in References to Other Classes, particularly
those for the class for miscellaneous active electrical nonlinear
devices, circuits, and systems.
Demodulators having a modulated input of less than infrared
frequency which may utilize an internal optical element (e.g., an
optical isolator) are classified in Class 329 by the type
of modulation.
The combination of modulation converter (e.g., FM
to AM) with a demodulator is classified in Class 329according to the modulation type of the
input to the converter. Modulation converters, per
se, are classified elsewhere. See References to
Other Classes, below.
For classification herein there must be complete extraction
of the modulating signal. Mere frequency converters (e.g., RF
to IF mixers) are not classified here. See References
to Other Classes, below.
Class 329 provides for demodulators, per se, with
structure for noise or distortion control (see Subclass
References to the Current Class, below).
Class 455, Telecommunications, provides for noise
or interference control in: (a) a telecommunication
system (i.e., transmitter and
receiver); (b) a complete telecommunication receiver; and (c)
a combination of two or more receiver elements (viz. wave
collector, wave mixer or modifier, demodulator, and
utilization device) where the combination is not elsewhere
classified. Therefore, consideration must be
given to extending the search for demodulator noise control circuitry
into relevant subclasses of Class 455. See also the SEARCH
CLASS notes in References to Other Classes, below, relating
to Class 455.
Subclasses of this class (329) relate to
suppressed carrier double sideband demodulators, per se, and
single/vestigial sideband demodulators, per se
(see Subclass References to the Current Class, below).
Class 455accepts this subject matter
in combination with what may be broadly recited diverse receiver
elements (viz. wave collector, wave modifier
or mixer, and utilization device). Therefore, in
completing the search for demodulators of an amplitude modulated
wave not having the full complement of carrier and two complete
sidebands, consideration must be given to extending the
search to relevant subclasses in Class 455. See also the
SEARCH CLASS notes in References to Other Classes, below, relating
to Class 455.
SECTION III - SUBCLASS REFERENCES TO THE CURRENT CLASS
Measuring and Testing, appropriate subclasses for measuring or testing
of a parameter which is typically neither electrical, optical, thermal, nor
chemical and which may include a demodulation technique.
Telegraphy,
subclasses 66.1+ for a teles:graphic system which transmits
messages between stations using alternating or pulsating currents
and particularly subclass 66.2 for such a system having
a transmitter which is turned on and off, subclass 117
for a teles:graphic system utilizing a coherer, and
subclasses 118+ for teles:graphic receivers in
general.
Radiant Energy, appropriate subclasses for the detection of invisible
radiation or the testing of material by invisible radiation which
may include a modulation - demodulation technique.
Active Solid-State Devices (e.g., Transistors, Solid-State
Diodes), appropriate subclasses for active solid-state
devices used as demodulators, including
subclass 10 , 11, 21, 53-56, 113-118, 184-189, 225-234, 257-258, 290-294, and 414-466
for radiation-sensitive active semiconductor devices.
Electrical Lamp and Discharge Devices: Systems,
subclasses 1+ for cathode-ray tube circuits with power
supply or the combination of cathode-ray tube and circuit
element in a unitary device, and subclasses 94+ for
an electron discharge device which is an ultimate load together
with a cathode or cathode heater supply circuit.
Electricity: Motive Power Systems,
subclasses 606+ for servo systems utilizing a feedback signal which
frequency or phase modulates a system carrier (particularly
subclasses 607 and 608 for obtaining the modulating wave by reference
signal frequency or phase comparison, respectively) subclass
622 for an AC lead or lag network which may include a demodulation technique, and
subclasses 671+ for particular servo system motor control (particularly
subclass 684 which utilizes a specific demodulator).
Electricity: Power Supply or Regulation
Systems, appropriate subclasses for control of the magnitude
or phase of current or voltage in a system comprising a single electrical
source coupled to a single electrical load.
Electricity: Measuring and Testing, appropriate subclasses for measurement of electrical properties, in
general, and particularly
subclasses 76.11+ for systems measuring and testing electricity which
may include demodulation, particularly subclasses 76.39+ for frequency
measurement and subclasses 76.77+ for phase comparison, and
subclass 118 for modulation of voltage or current to be measured
onto a carrier combined with subsequent structure to recover a replica
of the original voltage or current by demodulation.
Miscellaneous Active Electrical Nonlinear Devices, Circuits, and
Systems,
subclasses 1+ for miscellaneous signal parameter discriminating
or comparing for input signals not carrying intelligence, particularly
subclasses 2+ for miscellaneous phase discriminating, subclasses 31+ for
miscellaneous pulse spacing discriminating, subclasses
39+ for miscellaneous frequency discriminating, and
subclasses 50+ for miscellaneous amplitude discriminating. (See Lines
With Other Classes, above)
Amplifiers,
subclass 10 for an amplifier having an input which is the output
of a modulator and an output which is the input of a subsequent demodulator.
Oscillators,
subclasses 1+ for automatic oscillator frequency stabilization
using phase or frequency sensing which may include comparison with
a reference oscillator or a modulation technique, subclasses
46+ for plural oscillator systems in general, and
subclass 58 for an oscillator with structure to perform an additional
simultaneous function.
Modulators,
subclasses 100+ for a frequency shift keying modulator, subclasses
103+ for a phase shift keying modulator, subclasses
106+ for a pulse modulator, subclasses 117+ for
a frequency modulator, subclasses 144+ for a phase
modulator and subclasses 149+ for an amplitude modulator; subclasses
183+ for modulation converters, per se.
Wave Transmission Lines and Networks,
subclasses 24+ for transmission line coupling networks (particularly
subclasses 25+ for balanced to unbalanced circuits, subclasses
138+ for lumped parameter delay lines, and subclasses165 - 212
for filters), subclasses 236+ for long
lines, per se, and subclasses 245+ for
long line elements and components.
Tuners, appropriate subclasses for tuner circuits, per
se, which may include a broad recitation of a demodulator
plus details of a tuner and particularly
subclasses 30+ for a tuner with a resonance indicator in which
a demodulator may be used and subclass 39 for tuners combined with
other devices which may include a demodulator recited broadly.
Electrical Resistors,
subclass 1 for a coherer-type resistor and subclasses
13+ for a resistor whose resistance value varies in response
to a condition such as temperature or magnetic field.
Communications: Electrical,
subclasses 870.01+ for telemetry systems and especially subclasses
870.18+ indented thereunder for such systems
where the quantity to be telemetered is imposed on a carrier by
a particular type of modulation.
Coded Data Generation or Conversion,
subclasses 126+ for a pulse code demodulator, per se, and
subclass 143 for a delta modulation demodulator, per se.
Communications: Directive Radio Wave
Systems and Devices (e.g., Radar, Radio
Navigation),
subclasses 350+ for directive radio wave systems which may include
demodulation techniques and particularly subclasses 385+ for
a directive beacon or receiver.
Television,
subclasses 638+ for a demodulator particularly adapted for extracting
a component of a natural color television signal from a carrier
or subcarrier, subclasses 726+ for television
signal receivers and subcombination thereof.
Facsimile and Static Presentation Processing,
subclass 469 for modulation onto a carrier of a facsimile signal
derived from scanning a picture or for demodulation of such a modulated carrier
to reconstruct the picture.
Dynamic Magnetic Information Storage or Retrieval,
subclass 28 for control of a demodulator by a reference carrier
signal stored concurrently with the information signal to be demodulated
and subclasses 29+ for dynamic magnetic recording or reproducing
containing particular demodulator circuitry.
Electric Power Conversion Systems, particularly
subclasses 13+ for current conversion which includes generic
AC to DC rectifiers and generic DC to AC inverters of diverse type.
Thermal Measuring and Testing, appropriate subclasses for measurement systems responsive
to an external thermal condition which may utilize a modulation
technique.
Pulse or Digital Communications, appropriate subclasses for demodulators combined with receiving
structure to couple a modulated pulse wave from a transmission medium (i.e., a receiver) or
complete systems (i.e., transmitter and
receiver) incorporating such a combination, particularly
subclasses 237 through 242+ for a system or receiver utilizing pulse
number modulation, pulse width modulation, pulse position, frequency, or
spacing modulation, pulse amplitude modulation, or
pulse code modulation, subclasses 259+ for other
diverse types of digital communication systems which may include
a particular demodulator, and subclasses 316+ for
other diverse types of digital communication receivers which may
include a particular demodulator. (also see Lines
With Other Classes, above)
Motion Video Signal Processing for Recording or
Reproducing,
subclasses 307 through 310for frequency modulation of a color video signal, subclass
311 for amplitude modulation of a color video signal, and
subclass 312 for phase modulation of a color video signal in a recording
and reproduction device.
Telecommunications, appropriate subclasses for nondigital demodulators combined
with receiving structure to couple a modulated wave from a transmission
medium (i.e., a receiver) or
complete systems (i.e., transmitter
and receiver) incorporating such a combination, particularly
subclass 21 for frequency conversion in a repeater including
a demodulator, subclasses 39+ for separated transmitter
and receiver which may include a particular demodulator, subclasses
73+ for a transceiver which may include a particular demodulator, and
subclasses 130+ for a telecommunications receiver which
may include a particular demodulator; subclasses 202 and
204 for suppressed carrier double sideband demodulators, per
se, and single/vestigial sideband demodulators, in
combination with what may be broadly recited diverse receiver elements (viz. wave collector, wave
modifier or mixer, and utilization device); subclasses
313+ for mere frequency converters (e.g., RF
to IF mixers). (also see Lines With Other
Classes, above)
SECTION V - GLOSSARY
ARBITRARILY VARYING
Indicates having a future value which is not predictable from
past values. (Arbitrary is the opposite of repetitious).
CARRIER
An electrical or electromagnetic repetitious sinusoidal wave.
CHARACTERISTIC
An attribute associated with the size or shape of a wave or
signal. Examples are amplitude, frequency, or
phase of a sine wave and repetition rate, position, amplitude, or
width of a nonsine wave.
DEMODULATOR
A device which extracts an arbitrarily varying modulating
signal from an electrical or electromagnetic modulated signal of
less than infrared frequency.
MODULATED SIGNAL
A repetitious wave which has had a characteristic thereof
varied by a modulating signal.
MODULATING SIGNAL
An information carrying signal whose informational content
is to be impressed on a carrier or pulse wave.
MODULATOR
A device which varies a characteristic of a repetitious electrical
or electromagnetic wave of less than infrared frequency in accordance
with a characteristic of an arbitrarily varying modulating signal.
PULSE WAVE
An electrical or electromagnetic repetitious nonsinusoidal
wave. Examples are square wave, saw-tooth
wave, or trapezoidal wave.
REPETITIOUS WAVE
A cyclic wave whose individual component cycles are substantially
identical. Examples of repetitious waves are sine waves, square
waves, saw-tooth waves and trapezoidal waves.
FREQUENCY SHIFT KEYING OR MINIMUM SHIFT KEYING DEMODULATOR:
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from a signal which has undergone frequency shift keying modulation
or minimum shift keying modulation.
(1)
Note. Frequency shift keying modulation occurs when the frequency
of a carrier is shifted among a plurality of discrete values in
accordance with the modulating signal.
(2)
Note. Minimum shift keying modulation is a type of frequency
shift keying modulation in which there is phase continuity at the
frequency transition points.
(3)
Note. This subclass includes frequency shift keying demodulators,
per se. See the SEARCH CLASS notes below for combinations with
the subject matter of this subclass.
Pulse or Digital Communications,
subclasses 272+ for a frequency shift keying system (i.e., transmitter
and receiver) and subclasses 322+ for a frequency shift
keying demodulator combined with receiving structure.
This subclass is indented under subclass 300. Subject matter containing an electrical device whose constituent
portions are constructed from solid material having room temperature conductivity
between that of a conductor and an insulator and which conductivity
is typically modified through the addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 300. Subject matter where the modulated signal input to the demodulator
interacts with oscillations from a secondary source.
(1)
Note. The secondary oscillations may be internally generated
or externally supplied and may be at a frequency other than that
of the modulated input signal"s carrier.
PHASE SHIFT KEYING OR QUADRATURE AMPLITUDE DEMODULATOR:
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from a signal which has undergone phase shift keying modulation
or quadrature amplitude modulation.
(1)
Note. Phase shift keying modulation occurs when the phase
of a carrier is shifted among a plurality of discrete angles in
accordance with the modulating signal.
(2)
Note. Quadrature amplitude modulation occurs when the phase
and amplitude of a carrier is simultaneously shifted among a plurality
of discrete angle/magnitude pairs.
(3)
Note. This subclass includes phase shift keying demodulators
or quadrature amplitude demodulators, per se. See the SEARCH CLASS
notes below for combinations with the subject matter of this subclass.
Pulse or Digital Communications,
subclass 261 for a quadrature amplitude modulation system (i.e.,
transmitter and receiver), subclasses 279+ for a phase
shift keying system, and subclasses 322+ for a phase shift
keying demodulator combined with receiving structure.
This subclass is indented under subclass 304. Subject matter containing an electrical device whose constituent
portions are constructed from solid material having room temperature conductivity
between that of a conductor and an insulator and which conductivity
is typically modified through the addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 304. Subject matter where the modulated signal input to the demodulator
interacts therein with oscillations from a secondary source.
(1)
Note. The secondary oscillations may be internally generated
or externally supplied and may be at a frequency other than that
of the modulated input signal"s carrier.
This subclass is indented under subclass 306. Subject matter in which a phase or frequency locked loop
provides stability to or synchronization with the secondary source
of oscillations.
This subclass is indented under subclass 307. Subject matter utilizing a plurality of signal combiners
where the modulated input signal is combined with relatively phase
shifted versions of the secondary oscillations, or where the secondary
oscillations are combined with relatively phase shifted versions
of the modulated input signal.
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from a modulated signal which has undergone pulse modulation.
(1)
Note. Pulse modulation occurs when a repetitious pulse wave
has a characteristic varied in accordance with the modulating signal.
(2)
Note. Interrupted continuous wave modulation occurs when
a pulsed continuous wave has a characteristic varied in accordance
with the modulating signal.
(3)
Note. Examples of pulse waves are square waves, sawtooth
waves, and trapezoidal waves.
(4)
Note. Comparable structure having an input which is pulse
code modulated (PCM) or delta modulated are found elsewhere. See
the Search Notes below.
(5)
Note. This subclass includes pulse demodulators, per se.
See the SEARCH CLASS notes below for combinations with the subject
matter of this subclass.
Coded Data Generation or Conversion,
subclasses 126+ or 143 for a structure comparable structure to
this subclass (311) having an input which is pulse code modulated
(PCM) or delta modulated.
This subclass is indented under subclass 311. Subject matter where the modulated signal input to the demodulator
has undergone pulse position, frequency, phase or spacing modulation.
(1)
Note. Pulse position, frequency, phase or spacing modulation
are forms of pulse modulation where the characteristics being varied
are the relative positions of the pulses, the frequency (repetition
rate) of the pulses, the phase of the pulses, or the spacing (time)
between the pulses.
This subclass is indented under subclass 313. Subject matter containing an electrical device whose constituent
portions are constructed from solid material having room temperature conductivity
between that of a conductor and an insulator and which conductivity
is typically modified through the addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from a modulated signal which has undergone frequency modulation.
(1)
Note. Frequency modulation occurs when the frequency of a
carrier is varied over a continuum of values in accordance with
the modulating signal.
(2)
Note. This subclass includes frequency modulation demodulators,
per se. See the SEARCH CLASS notes below for combinations with
subject matter of this subclass.
Telecommunications,
subclasses 42+ for frequency demodulation in a system with separated
transmitter and receiver, and subclasses 205+ for a combination
of frequency demodulator with receiving structure.
This subclass is indented under subclass 315. Subject matter which utilizes a diverse intermediate type
of demodulator within the FM demodulator or combines the outputs
of a plurality of FM demodulators or has an output selectable from
a plurality of demodulators one of which must be an FM type.
This subclass is indented under subclass 315. Subject matter including the neutralization of an undesirable
characteristic of a frequency modulation demodulator or its signals.
Telecommunications,
subclasses 63.1 through 65and subclasses 501-506 for noise control in a telecommunication
system with separated transmitter and receiver, subclasses 210-211
for carrier amplitude modulation elimination in an FM receiver and
subclasses 296-312 for receiver noise or interference control, particularly
subclasses 309 and 312.
This subclass is indented under subclass 318. Subject matter which combines a derived error or deviation
signal with an intermediate demodulator signal to achieve neutralization
of an undesirable characteristic in the final demodulator output.
This subclass is indented under subclass 318. Subject matter which restricts the magnitude of signal fluctuations
within the demodulator itself to achieve the neutralization.
This subclass is indented under subclass 315. Subject matter utilizing a structure or device which is
peculiar to microwave frequencies or which has resistance, inductance
or capacitance not concentrated in lumped circuit elements.
This subclass is indented under subclass 315. Subject matter where the modulated signal input to the demodulator
interacts therein with oscillations from a secondary source.
(1)
Note. The secondary oscillations may be internally generated
or externally supplied and may be at a frequency other than that
of the modulated input signal"s carrier.
Telecommunications,
subclasses 208+ for synchronized or controlled local oscillator
in a FM receiver and subclasses 255+ for generic local
oscillator frequency control in a receiver.
This subclass is indented under subclass 323. Subject matter in which the modulated input signal has a
direct interaction with the secondary source of oscillations and
where the modulating signal is extracted directly therefrom.
This subclass is indented under subclass 323. Subject matter in which a phase or frequency locked loop
provides stability to the secondary source of oscillations.
This subclass is indented under subclass 325. Subject matter containing an electrical device whose constituent
portions are constructed from solid material having room temperature conductivity
between that of a conductor and an insulator and which conductivity
is typically modified through the addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 315. Subject matter where the modulated signal input to the demodulator
is separated into a plurality of closely analogous or identical
representations.
This subclass is indented under subclass 327. Subject matter which incorporates a resonant component having
the ability to transform mechanical energy into electrical energy
(e.g., piezoelectric).
(1)
Note. Piezoelectric resonant elements are typically crystals.
This subclass is indented under subclass 327. Subject matter in which the separated signal representations
are obtained at the various wound portions of a transformer (e.g.,
primary or secondary windings).
This subclass is indented under subclass 329. Subject matter where representations of the modulated input
signal are extracted from the primary and the secondary windings
of the transformer.
This subclass is indented under subclass 330. Subject matter which additionally utilizes a plurality of
diodes in demodulation.
(1)
Note. An example of this structure is a ratio detector where
the ratio of a pair of diode rectified currents is proportional
to frequency variations of an input signal.
This subclass is indented under subclass 329. Subject matter where representations of the modulated input
signal are extracted from plural secondary windings of the transformer.
This subclass is indented under subclass 332. Subject matter which additionally utilizes a plurality of
diodes in demodulation.
(1)
Note. An example of this structure is a ratio detector where
the ratio of a pair of diode rectified currents is proportional
to frequency variations of an input signal.
This subclass is indented under subclass 333. Subject matter which additionally utilizes a pair of tuned
circuits having resonant frequencies above and below the carrier
frequency of the input signal.
This subclass is indented under subclass 329. Subject matter which additionally utilizes a plurality of
diodes in demodulation.
(1)
Note. An example of this structure is a ratio detector where
the ratio of a pair of diode rectified currents is proportional
to frequency variations of an input signal.
This subclass is indented under subclass 327. Subject matter in which an unmodified modulated signal is
subsequently combined with a time delayed version thereof.
(1)
Note. Such a time delay can also be considered to be a phase
shift.
This subclass is indented under subclass 327. Subject matter in which the input signal is separated into
plural representations by an inductive-capacitive resonant circuit.
This subclass is indented under subclass 338. Subject matter utilizing a pair of inductive-capacitive
tuned circuits having resonant frequencies above and below the carrier
frequency of the input signal.
This subclass is indented under subclass 327. Subject matter which additionally utilizes a plurality of
diodes in demodulation.
(1)
Note. An example of this structure is a ratio detector where
the ratio of a pair of diode rectified currents is proportional
to frequency variations of an input signal.
This subclass is indented under subclass 315. Subject matter in which the frequency modulated input signal
is first changed to a pulse equivalent and then processed.
This subclass is indented under subclass 341. Subject matter containing an electrical device whose constituent
portions are constructed from solid material having room temperature conductivity
between that of a conductor and an insulator and which conductivity
is typically modified through the addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 315. Subject matter in which the modulated input signal transits
a single demodulating circuit path which contains a tuned circuit.
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from a modulated signal which has undergone phase modulation.
(1)
Note. Phase modulation occurs when the phase of a carrier
is varied over a continuum of values in accordance with the modulating
signal.
(2)
Note. This subclass includes phase modulation demodulators,
per se. See SEARCH CLASS notes below for combinations with the
subject matter of this subclass.
Telecommunications,
subclasses 42+ for phase demodulation in a system with separated
transmitter and receiver, and subclasses 205+ for a combination
of phase demodulator with receiving structure.
This subclass is indented under subclass 345. Subject matter where the modulated signal input to the demodulator
interacts therein with oscillations from a secondary source.
(1)
Note. The secondary oscillations may be internally generated
or externally supplied and may be at a frequency other than that
of the modulated input signal"s carrier.
Telecommunications,
subclasses 208+ for a synchronized or controlled local oscillator
in a phase modulation receiver and subclasses 255+ for generic
local oscillator frequency control in a receiver.
This subclass is indented under the class definition. Subject matter where the demodulator extracts the modulating
signal from an input AM signal.
(1)
Note. Amplitude modulation is achieved by varying the amplitude
of a carrier over a continuum of values in accordance with a modulating
signal.
(2)
Note. This subclass includes amplitude modulation demodulators,
per se. See the SEARCH CLASS note below for combinations with the
subject matter of this subclass.
This subclass is indented under subclass 347. Subject matter where there are more than one output signal
which as undergone demodulation, one of which must have undergone
amplitude demodulation.
This subclass is indented under subclass 347. Subject matter including the neutralization of an undesirable
characteristic of an amplitude modulation demodulator or its signals.
Telecommunications,
subclasses 63.1 through 65and 501-506 for noise control in a telecommunication
system with separated transmitter and receiver, and subclasses 296-312
for receiver noise or interference control, particularly subclasses
309 and 312.
This subclass is indented under subclass 349. Subject matter in which undesirable fluctuations in the
magnitude of a demodulator signal are eliminated or reduced.
This subclass is indented under subclass 349. Subject matter where an undesirable nonlinear characteristic
of a demodulator, its components or its signals is neutralized.
This subclass is indented under subclass 349. Subject matter in which undesired signal components superimposed
upon a desired demodulator signal are attenuated.
(1)
Note. In some instances, noise is generated due to an inherent
characteristic of a demodulator circuit component.
This subclass is indented under subclass 347. Subject matter utilizing a structure or device which is
peculiar to microwave frequencies or which has resistance, inductance
or capacitance not concentrated in lumped circuit elements.
This subclass is indented under subclass 354. Subject matter utilizing a device which has electrical current
flow between two spaced electrodes in a gas, vapor or vacuum.
(1)
Note. This might include, for example, vacuum or gas tubes
such as diodes, triodes or pentodes.
(2)
Note. Additional control electrodes may be present.
Telecommunications,
subclass 46 for a suppressed carrier system having separated
transmitter and receiver and subclass 202 for a suppressed carrier- type
receiver.
Telecommunications,
subclass 47 for a single or vestigial sideband system with
separated transmitter and receiver and subclasses 203 or 204 for a
single sideband or vestigial sideband-type receiver, respectively.
This subclass is indented under subclass 347. Subject matter where the modulated signal input to the demodulator
interacts therein with oscillations from a secondary source.
(1)
Note. The secondary oscillations may be internally generated
or externally supplied and may be at a frequency other than that
of the modulated input signal"s carrier.
(2)
Note. A synchronous demodulator uses a local carrier frequency
signal synchronized with the carrier of the modulated input signal
to cancel out the modulated input signal"s carrier.
This subclass is indented under subclass 358. Subject matter where the input AM signal interacts directly
with the local secondary source of oscillations.
This subclass is indented under subclass 358. Subject matter in which frequency stability is provided
to the secondary source of oscillations by a phase or frequency
locked loop.
This subclass is indented under subclass 361. Subject matter utilizing an electrical device with three
external connection points where the constituent portions of the
device are constructed from solid material having room temperature
conductivity between that of a conductor and an insulator and which
conductivity is typically modified through the addition of small
amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 347. Subject matter in which the modulated signal input to the
demodulator is separated into a plurality of closely analogous or
identical representations.
This subclass is indented under subclass 363. Subject matter utilizing an electrical device with three
external connection points where the constituent portions of the
device are constructed from solid material having room temperature
conductivity between that of a conductor and an insulator and which
conductivity is typically modified through the addition of small
amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 347. Subject matter in which an AM demodulator, not requiring
a supplemental source of oscillations to achieve demodulation, positively
feeds back a portion of its output to provide signal enhancement.
This subclass is indented under subclass 347. Subject matter in which an AM demodulator utilizes a device
which has electrical current flow between two spaced electrodes
in a gas, vapor or vacuum and which current flow is controlled by
an additional electrode.
This subclass is indented under subclass 347. Subject matter in which the AM demodulator utilizes an electrical
device with three external connection points where the constituent
portions of the device are constructed from solid material having
room temperature conductivity between that of a conductor and an
insulator and which conductivity is typically modified through the
addition of small amounts of dopant.
(1)
Note. This might include, for example, semiconductor diodes
or transistors of diverse type.
This subclass is indented under subclass 347. Subject matter where the demodulating element includes conductors
loosely resting against each other in imperfect conducting contact,
the conductors being of such a material and shape that passage of
a high frequency current therethrough modifies the conducting contact.
(1)
Note. Usually the demodulating element is formed from loosely
packed metallic granules, whose contact resistance decreases upon
passage of a high frequency current therethrough. However, the
contact resistance may increase under these conditions to constitute
an anticoherer, which is also included here.
(2)
Note. The coherer often includes structure, namely, a decoherer,
for breaking the coherence established by the high frequency current.
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