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MODULATION (measuring, testing G01R; masers, lasers H01S; modulators specially adapted for use in the amplifiers H03F 3/38; modulating pulses H03K 7/00; so-called modulators capable only of a switching between predetermined states of amplitude, frequency or phase H03K 17/00, H04L; coding, decoding or code conversion, in general H03M; synchronous modulators specially adapted for colour television H04N 9/65)
Definition statement
This subclass/group covers:
  • Modulation, keying, or interruption of sinusoidal oscillations or electromagnetic waves, the modulating signal having any desired waveform.
  • Amplitude modulation
  • Angle modulation
  • Amplitude and angle modulation produced simultaneously or at will by the same modulating signal
  • Modulating electromagnetic waves
Relationship between large subject matter areas

Transference of modulation from one carrier to the other and frequency changing is classified in H03D 7/00. Frequency changers used to convert from baseband may, where appropriate, additionally be classified in H03C.

H03C is used to classify modulators essentially at the lowest circuit level. Higher level aspects, e.g. transmitters or transmission systems, particularly where the modulator type is only a black box or of a standard configuration, are generally classified in H04B, H04L or with the specific application.

References relevant to classification in this subclass
This subclass/group does not cover:
Measuring, testing
Modulating light
Masers, lasers
Modulators specially adapted for use in dc amplifiers
Modulating pulses
So-called modulators capable only of switching between predetermined states of amplitude, frequency or phase
Coding, decoding or code conversion, in general
Transmission of data signals, monitoring and testing arrangements and suppression of noise and interference
Modulating non-sinusoidal oscillations
AC transmission systems
Synchronous modulators specially adapted for colour television
Special rules of classification within this subclass

- Circuits usable both as modulator and demodulator are classified in H03C.

- Quite frequently, an exclusive group assignment of documents to amplitude modulation (H03C 1/00) or angle modulation (H03C 3/00) is not feasible (and/or not given within the document). In these cases, the best match with a subgroup definition in either or both groups is decisive.

- Cases concerning a type of modulation that effects neither amplitude nor angle modulation, e.g. waveform modulation, should be classified in H03C 99/00.

Amplitude modulation (H03C 5/00, H03C 7/00 take precedence)
Definition statement
This subclass/group covers:

Circuits and methods usable for modulation of a sinusoidal electromagnetic carrier wave whereby its amplitude is modified according to a modulating signal with frequency lower than that of the carrier. The modulating signal can be digital, resulting e.g. in Amplitude Shift Keying, or analog (see the example below).

Example:

Waveform of amplitude modulated carrier wave.

Relationship between large subject matter areas

While modulators modulating the angle as well as the amplitude of a signal are classified in H03C 5/00, aspects of the amplitude modulation may still be classified in H03C 1/00.

References relevant to classification in this main group
This subclass/group does not cover:
Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal
Modulating electromagnetic waves
Mixers per se
Pulse amplitude modulation
Informative references
Attention is drawn to the following places, which may be of interest for search:
Balanced modulators/mixers
H03D 7/1425, H03D7/14D, H03D7/14E
Amplifiers
Summing of phase-modulated signals
Automatic control of gain
Transmitters and details of transmission
AC transmission systems including amplitude modulation circuits
Special rules of classification within this main group

Documents should in general be classified in all subgroups which apply, e.g. a single sideband modulator may, in addition to H03C 1/60, be classified in H03C 1/36, if it is a transistor type.

Glossary of terms
In this subclass/group, the following terms (or expressions) are used with the meaning indicated:

In this main group, the following terms (or expressions) are used with the meaning indicated:

by means of
The actual amplitude modulation is performed by these "means". It does not mean that such "means" are merely present in the circuit but fulfilling another purpose.
Synonyms and Keywords

In patent documents the following abbreviations are often used:

AM
Amplitude Modulation
SSB
single side band
by means of variable impedance element (H03C 1/28 to H03C 1/34, H03C 1/46 to H03C 1/52, H03C 1/62 take precedence)
References relevant to classification in this subgroup
This subclass/group does not cover:
Amplitude Modulation by means of transit-time tube
Amplitude Modulation by means of a magnetron
Amplitude Modulation by deflection of electron beam in discharge tube
Amplitude Modulation by means of light-sensitive element
Amplitude Modulators with mechanically or acoustically driven parts
Amplitude Modulation by means of Hall-effect devices
Amplitude Modulation by converting angle modulation to amplitude modulation
Amplitude Modulators in which carrier or one side-band are wholly or partially suppressed
Amplitude Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present
by means of discharge device having at least three electrodes (H03C 1/28 to H03C 1/34, H03C 1/50, H03C 1/52, H03C 1/62 take precedence)
References relevant to classification in this group
This subclass/group does not cover:
Amplitude Modulation by means of transit-time tube
Amplitude Modulation by means of a magnetron
Amplitude Modulation by deflection of electron beam in discharge tube
Amplitude Modulation by means of light-sensitive element
Amplitude Modulation by converting angle modulation to amplitude modulation
Amplitude Modulators in which carrier or one side-band are wholly or partially suppressed
Amplitude Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present
by means of semiconductor device having at least three electrodes (H03C 1/34, H03C 1/50, H03C 1/52, H03C 1/62 take precedence)
References relevant to classification in this group
This subclass/group does not cover:
Amplitude Modulation by means of light-sensitive element
Amplitude Modulation by converting angle modulation to amplitude modulation
Amplitude Modulators in which carrier or one side-band are wholly or partially suppressed
Amplitude Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present
by converting angle modulation to amplitude modulation (H03C 1/28 to H03C 1/34, H03C 1/46, H03C 1/48 take precedence)
Definition statement
This subclass/group covers:

Example:

US2007040606

Conversion of angle modulation (212) in amplitude modulation (228).

References relevant to classification in this subgroup
This subclass/group does not cover:
Amplitude Modulation by means of transit-time tube
Amplitude Modulation by means of a magnetron
Amplitude Modulation by deflection of electron beam in discharge tube
Amplitude Modulation by means of light-sensitive element
Amplitude Modulators with mechanically or acoustically driven parts
Amplitude Modulation by means of Hall-effect devices
Modulators in which carrier or one side-band are wholly or partially suppressed (H03C 1/28 to H03C 1/34, H03C 1/46, H03C 1/48 take precedence)
References relevant to classification in this subgroup
This subclass/group does not cover:
Amplitude Modulation by means of transit-time tube
Amplitude Modulation by means of a magnetron
Amplitude Modulation by deflection of electron beam in discharge tube
Amplitude Modulation by means of light-sensitive element
Amplitude Modulators with mechanically or acoustically driven parts
Amplitude Modulation by means of Hall-effect devices
[N: using field-effect transistors]
Definition statement
This subclass/group covers:

Example:

EP1338085

Carrier suppression in a double balanced modulator using field effect transistors.

Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present (H03C 1/28 to H03C 1/34, H03C 1/46, H03C 1/48 take precedence)
References relevant to classification in this group
This subclass/group does not cover:
Amplitude Modulation by means of transit-time tube
Amplitude Modulation by means of a magnetron
Amplitude Modulation by deflection of electron beam in discharge tube
Amplitude Modulation by means of light-sensitive element
Amplitude Modulators with mechanically or acoustically driven parts
Amplitude Modulation by means of Hall-effect devices
Angle modulation (H03C 5/00, H03C 7/00 take precedence)
Definition statement
This subclass/group covers:

-Circuits and methods usable for angle, i.e. frequency and/or phase modulation.

Relationship between large subject matter areas

While modulators modulating the angle as well as the amplitude of a signal are classified in H03C 5/00, aspects of the angle modulation may still be classified in H03C 3/00.

References relevant to classification in this group
This subclass/group does not cover:
Frequency tuning of oscillators
Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal
Modulating electromagnetic waves
Tuning of resonant circuits
Pulse/frequency modulators
Informative references
Attention is drawn to the following places, which may be of interest for search:
Oscillators, VCO
Mixers per se
PLLs and other frequency regulation arrangements in general
PLL with fractional dividers
Reduction of nonlinear distortion in amplifiers (particularly regarding H03C 3/406 and H03C 5/00
Transmitters and details of transmission
AC transmission systems including phase or frequency modulation circuits
Glossary of terms
In this subclass/group, the following terms (or expressions) are used with the meaning indicated:
FM
Frequency Modulation
PLL
Phase Locked Loop
VCO
Voltage Controlled Oscillator
"by means of" in the subgroup definition
see explanation in H03C 1/00
Means for changing frequency deviation
Definition statement
This subclass/group covers:

Means for modifying the frequency modulation characteristics, e.g. the frequency range or bandwidth or the sensitivity of frequency deviation with respect to the modulating signal.

Informative references
Attention is drawn to the following places, which may be of interest for search:
Reducing frequency deviation for demodulation
Modifications of modulator for regulating the mean frequency [N: for demodulation H03D 3/003, H03D 3/242 ]
Definition statement
This subclass/group covers:

Modifications of angle modulators for regulating the mean frequency of the carrier wave

Example:

US5331293

Regulation of mean frequency in a modulator without PLL, using a demodulator in the feedback path

[N: using a phase locked loop]
Definition statement
This subclass/group covers:

Schematic view of a PLL including a reference clock (LO), a phase detector, a loop filter, a voltage controlled oscillator (VCO) and a divider. The arrows point to subgroups assigned to manners of modulation.

Example:

US2007093217

Regulation of mean frequency in a modulator with PLL, using three point modulation (H03C 3/0941) in divider (H03C 3/0925), reference clock (H03C 3/0966) and in front of the VCO (H03C 3/095) and at a mixer (H03C 3/0983).

Informative references
Attention is drawn to the following places, which may be of interest for search:
PLL with frequency divider/counter in general
[N: using fractional frequency division in the feedback loop of the PLL]
References relevant to classification in this subgroup
This subclass/group does not cover:
PLL synthesisers with fractional dividers
by means of variable impedance (H03C 3/30 to H03C 3/38 take precedence)
Definition statement
This subclass/group covers:

Circuits or methods using an element with variable impedance for angle modulation.

References relevant to classification in this group
This subclass/group does not cover:
Angle modulation by means of transit-time tube
Angle modulation the tube being a magnetron
Angle modulation by deflection of electron beam in discharge tube
Angle modulation by means of light-sensitive element
Conversion of amplitude to angle modulation
[N: using bipolar transistors (H03C 3/227 takes precedence) ]
References relevant to classification in this group
This subclass/group does not cover:
Using a combination of bipolar transistors and field effect transistors
[N: using field effect transistors (H03C 3/227 takes precedence)]
References relevant to classification in this group
This subclass/group does not cover:
Using a combination of bipolar transistors and field effect transistors
[N: using two quadrature frequency conversion stages in cascade]
Definition statement
This subclass/group covers:

Example:

US2003095608

Conversion of amplitude to angle modulation by using two quadrature frequency conversion stages in cascade (4, 5 and 11, 12)

by means of electromechanical devices (H03C 3/28 takes precedence)
References relevant to classification in this group
This subclass/group does not cover:
Angle modulation using variable impedance driven mechanically or acoustically
Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal (H03C 7/00 takes precedence)
Definition statement
This subclass/group covers:
  • Circuits selectable between FM and AM modulation
  • Polar or phase-amplitude modulation by means of transistor circuits
  • Polar or phase-amplitude modulation by means of transit time tubes

Example:

EP2034686

Polar modulation resulting in simultaneous amplitude and phase modulation.

References relevant to classification in this group
This subclass/group does not cover:
Conversion of angle to amplitude modulation
Conversion of amplitude to angle modulation
Modulating electromagnetic waves
Glossary of terms
In this subclass/group, the following terms (or expressions) are used with the meaning indicated:
"by the same modulating signal"
also includes the common case where the modulation signal is split into two components
Modulating electromagnetic waves (modulating light G02F 1/00 ; for generating oscillations H03B, H03K)
Definition statement
This subclass/group covers:

Modulation of electromagnetic waves, e.g. microwaves

- in transmission line, waveguide, cavity resonator or radiation field of aerial H03C 7/02

References relevant to classification in this main group
This subclass/group does not cover:
Modulating light
Informative references
Attention is drawn to the following places, which may be of interest for search:
For generating oscillations H03B
[N: using semiconductor devices]
Definition statement
This subclass/group covers:

Example:

EP0463665

Microwave modulator using transmission line (2), vector modulator (4) and quadrature detector (6).

Polarisation of transmitted wave being modulated [N: H03C 7/022 takes precedence]
References relevant to classification in this subgroup
This subclass/group does not cover:
Using ferromagnetic devices, e.g. ferrites
Subject matter not provided for in other groups of this subclass
Definition statement
This subclass/group covers:

Modulation, keying, or interruption of sinusoidal oscillations or electromagnetic waves that does not comply with other groups of this subclass.

References relevant to classification in this group
This subclass/group does not cover:
Amplitude modulation
Angle modulation
Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal
Modulating electromagnetic waves
Special rules of classification within this main group

So far this main group is empty.

Indexing scheme relating to details of modulators or modulation methods covered by H03C
Definition statement
This subclass/group covers:

Particular circuit elements of modulators H03C200/01

Functional aspects of modulators H03C200/02

Filters with particular characteristics
References relevant to classification in this group
This subclass/group does not cover:
Filtering of the input modulating signal for obtaining a constant sensitivity of frequency modulation
T03C200/02D1
Gilbert multipliers
Informative references
Attention is drawn to the following places, which may be of interest for search:
Balanced arrangements for transference of modulation from one carrier to another
Modulators with one sideband wholly or partially suppressed
References relevant to classification in this group
This subclass/group does not cover:
Amplitude modulators in which one side-band is wholly or partially suppressed
Measures to linearise modulation or reduce distortion of modulation characteristics
References relevant to classification in this group
This subclass/group does not cover:
Modification of amplitude modulators to reduce distorsion
Modification of angle modulators to linearise modulation
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Last Modified: 10/11/2013