Cooperative Patent Classification

CPC Definition - Subclass H04K

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Last Updated Version: 2016.11
Definition statement

This place covers:

Two main groups (H04K 1/00 - secret communication, H04K 3/00 - Jamming of communication; Countermeasures), which both relate to communication and to (ensuring or attacking) the security of the physical transmission channel.

Secret communication (ciphering or deciphering apparatus per se G09C; systems with reduced bandwidth or suppressed carrier H04B 1/66; spread spectrum techniques H04B 1/69; by using a sub-carrier H04B 14/08; by multiplexing H04J; transmission systems for secret digital information H04L 9/00; secret or subscription television systems H04N 7/16, H04N 21/00)
Definition statement

This place covers:

Secret communication in the analogue domain for speech and non-speech data.

Limiting references

This place does not cover:

Ciphering or deciphering apparatus per se

Systems with reduced bandwidth or suppressed carrier

Spread spectrum techniques in general

By using a sub-carrier

By multiplexing

Transmission systems for secret digital information

Secret or subscription television systems

Jamming of communication; Counter-measures (counter-measures used in radar or analogous systems G01S 7/00; {in radar G01S 7/36, G01S 7/38; in lidar G01S 7/495; in sonar G01S 7/537})
Definition statement

This place covers:

  • "jamming", only when it means purposefully trying to interfere with the physical transmission and reception of communication.
  • provided this condition is met, this group covers devices and methods for:

1. jamming of communication:

1.1 jamming by intentionally decreasing the signal to noise ratio

1.2 deceptive jamming (H04K 3/65)

1.3 passive jamming (H04K 3/68)

1.4 destructive jamming (H04K 3/62)

2. countermeasures against jamming (H04K 3/20 and lower)

3. countermeasures against undesired self-jamming resulting from jamming (H04K 3/28)

4. countermeasures against surveillance, interception or detection (H04K 3/82 and lower)

5. other electronic countermeasures using or against electromagnetic or acoustic waves (H04K 3/00)

6. signal detection techniques used in relation to

6.1. jamming: for interception and monitoring of the jamming target signal (H04K 3/45)

6.2. anti-jamming: for jamming detection (H04K 3/22 and lower)

6.3. anti-surveillance: for surveillance detection (H04K 3/822)

  • in particular, this group covers:

1. jamming for testing or assessing countermeasures (H04K 3/94)

2. jamming used to prevent:

i) in a vehicle during motion (H04K 3/415)

ii) in particular areas, including prisons, hospitals, planes, petrol stations, theatres (H04K 3/84)

iii) to trigger RCIEDs (H04K 3/92 and H04K 2203/24)

  • reception of positioning data using GPS (H04K 3/90)
  • wireless communication in ad hoc networks or in sensor networks (H04K 2203/18)
  • exchange of data between wirelessly connected devices or device units, on Bluetooth, infrared or near field links
  • unauthorized access to network, service or information (H04K 3/86), including:

i) access to a WLAN network (H04K 2203/18)

ii) access to information stored in contactless carriers, including RFID carriers (H04K 2203/20)

i) of speech in meeting rooms (H04K 2203/12)

ii) of electromagnetic emissions from a computer screen H04K 2203/14)

  • interception or detection of a wirelessly transmitted signal (H04K 3/825)
Relationships with other classification places

H04K 3/00 and application fields

Application fields (e.g. in the lower part of the "Informative reference" table below): when a patent document discloses how the jamming, anti-jamming, anti-surveillance or any other countermeasure covered by H04K 3/00 is carried out, it should be classified in H04K 3/00.


Jamming should be understood as meaning "intentional disturbance".

Interference should be understood as meaning "unintentional disturbance".

This distinction in the terminology is however not always respected in patent documents (in particular in the expressions "transceiver self-jamming" and "jamming cancellation", where jamming means interference).


Jamming and anti-jamming techniques are covered by H04K 3/00 and lower.

Anti-interference techniques are covered by H04B.

Since intentional and unintentional disturbances often present similar characteristics, they can be countered by the same techniques. Therefore, there exists an overlap between H04K 3/20 and H04B, and some documents are classified in both places.

Cancellation of "self-jamming"

  • intentional self-jamming (e.g. self-jamming of receiver to counter interference; self-jamming of transmitter to counter surveillance): H04K;
  • undesired self-jamming caused by transmitting: H04B 1/525;
  • undesired self-jamming caused by transmitting a jamming signal intentionally: H04B 1/525 and H04K 3/28;


If the intentional self-jamming signal is known by the transmitter and the receiver of the jammed signal (and can therefore be regarded as a shared secret): H04K 1/00

Other cases of intentional self-jamming: H04K 3/00

Limiting references

This place does not cover:

Counter-measures used in radar

Counter-measures used in sonar

Counter-measures used in lidar

Informative references

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

Secret communication

Vehicle anti-theft relating to remote keyless entry

Vehicle anti-theft alarm transmission


Defence devices

Radars and GPS

Contactless record carriers (e.g. RFID carriers)

Remote keyless entry

Alarm and surveillance



Gain control

Automatic frequency control

Electric pulse generators


Reducing, in transceivers, leakage of transmitter signal into the receiver

Spread spectrum techniques

Suppression or limitation of noise or interference

Monitoring or testing of receivers for locating or positioning the transmitter

Measuring or estimating channel quality parameters

Flow control or congestion control packet switching networks

Network architectures or network communication protocols for network security for supporting lawful interception, monitoring or retaining of communications or communication related information

Handfree telephone for vehicles

Television systems

Wireless communications networks

Wireless security

Cognitive radio

Wireless local area networks (WLAN)

Self-organizing networks, ad-hoc networks and sensor networks


Special rules of classification

A patent document should be classified in H04K 3/20 when the countered signal disturbance is:

  • intentional (whether offensive or defensive) or
  • used in a military, security or confidentiality context.
Glossary of terms

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

Jamming of communication

Purposefully trying to interfere with the physical transmission or reception of communication

Self-jamming resulting from jamming

Undesired interference, caused by a jamming device, to the communication of the jamming device itself or of a friendly device, and resulting from intentionally interfering with the communication of adversary devices

Follower jammer

Jammer adapted to determine and follow the frequency of a jamming target signal that uses frequency hopping techniques

Look-through mode

Operation mode wherein jamming and monitoring of the jamming target alternate

Reactive jammer

Jammer wherein jamming is activated only when a target has been detected

Synonyms and Keywords

In patent documents, the following abbreviations are often used:


(Fast) Frequency Hopping


Global Positioning System


Near Field Communication


Remote Controlled Improvised Explosive Device


Radio Frequency IDentification


Wireless Local Area Network