H03D - Definition

Definition statement

This subclass covers:

Demodulation or transference of signals modulated on a sinusoidal carrier or on electromagnetic waves

Demodulation of amplitude-modulated oscillations

Demodulation of angle-modulated oscillations

Circuits for demodulating amplitude-modulated or angle-modulated oscillations at will

Transference of modulation from one carrier to another

Demodulation or transference of modulation of modulated electromagnetic waves

Super-regenerative demodulators

Circuits for comparing the phase or frequency of two mutually independent oscillations

Relationship between large subject matter areas

The modulation and demodulation of pulse trains, for example in Pulse Width Modulation circuits, is covered in subclass H03K.

The modulation by digital signals of the frequency, phase or amplitude of a sinusoidal carrier, or carriers, for example in quadrature (I-Q) modulation systems, and the demodulation thereof, is covered in subclass H04L.

Analogue quadrature modulation used in the NTSC and PAL colour television systems (where the I and Q signals representing colour difference values are substantially continuously variable), and the demodulation of these signals, is covered in H04N.

The modulation of sinusoidal signals, for example in AM and FM broadcasting, is covered in sub class H03C.

References relevant to classification in this subclass

This subclass does not cover:

Masers, lasers	H01S
Circuits capable of acting both as modulator and demodulator; balanced modulators	H03C, H03C 1/54
Details applicable to both modulators and frequency changers	H03C
Demodulating pulses which have been modulated with a continuously variable signal	H03K 9/00
Transforming types of pulse modulation	H03K 11/00
Relay systems, e.g. repeater stations	H04B 7/14
Demodulators adapted for digitally modulated-carrier systems.	H04L 27/00
Synchronous demodulators adapted for colour television	H04N 9/66
Phase locked loops; phase comparators therein	H03L 7/08 - H03L 7/097

Informative references

Attention is drawn to the following places, which may be of interest for search:

Coding, decoding or code conversion, in general	H03M
Details of receivers	H04B 1/06
Circuits for superheterodyne receivers	H04B 1/26

Glossary of terms

In this subclass, the following terms or expressions are used with the meaning indicated:

Homodyne	A receiver in which the local oscillator (LO) frequency is set to the same frequency as the received RF carrier frequency resulting in direct conversion of the received signal to a baseband (or zero IF) frequency for information recovery. In a near-zero IF receiver, the LO frequency is set very close to the carrier frequency of the RF signal.
Superheterodyne receiver	A receiver in which a received RF signal is converted to an intermediate frequency (IF) by at least one stage of frequency conversion (e.g. a 'mixer' stage which forms the product of the RF signal and a local oscillator signal)

Synonyms and Keywords

In patent documents the following abbreviations are often used:

Superhet	A superheterodyne receiver
Double (multiple) superhet	A double-conversion receiver using two intermediate frequencies, i.e. a superhet receiver in which a received RF signal passes through two (or more) successive stages of frequency conversion to different intermediate frequencies, one of which may be zero-IF or baseband.