Source: https://patents.justia.com/patent/9366750
Timestamp: 2019-10-15 03:41:41
Document Index: 99964158

Matched Legal Cases: ['Application No. 60', 'art 11', 'Application No. 06', 'art 11', 'art 11', 'art 11', 'art 16']

US Patent for Radar detection and dynamic frequency selection Patent (Patent # 9,366,750 issued June 14, 2016) - Justia Patents Search
Justia Patents By Changing FrequencyUS Patent for Radar detection and dynamic frequency selection Patent (Patent # 9,366,750)
Apr 16, 2010 - Marvell World Trade LTD.
A method and apparatus for: receiving a radio frequency (RF) signal on a first channel; determining a radio signal strength of the RF signal; performing a correlation of the RF signal with a predetermined sequence of a wireless data packet to determine whether the RF signal contains the predetermined sequence; in response to the RF signal not containing the predetermined sequence, generating an indication that the RF signal is not a wireless data packet; and determining whether the radio signal strength of the RF signal exceeds a predetermined threshold. In response to i) the radio signal strength exceeding the predetermined threshold and ii) the indication being generated: measuring a parameter associated with the RF signal; determining whether the RF signal is a radar signal based on the parameter; and changing from the first channel in response to the RF signal being determined to be a radar signal.
This application is a continuation of U.S. patent application Ser. No. 11/410,938, filed Apr. 25, 2006, which claims the benefit of U.S. Provisional Application No. 60/742,480, filed Dec. 5, 2005. The disclosures of the above applications are incorporated herein by reference in their entirety.
Radar is an acronym for Radio Detection and Ranging. The term “radio” refers to a radio frequency (RF) wave called a carrier of frequency fc that is modulated to form a radar pulse train. The detection and ranging part of the acronym refers to timing a delay between transmission of an RF pulse and its subsequent return. If the time delay is Δt, a range of the radar may be determined by the formula:
where c=3×108 m/s and is the speed of light. The factor of two in the formula accounts for the return trip.
A wireless network device comprises a correlation module that correlates a predetermined portion of a radio frequency (RF) signal and that generates a correlation signal based thereon. The wireless network device comprises an automatic gain control (AGC) module that generates a gain control signal based on the RF signal. The wireless network device comprises a control module that selectively determines whether the RF signal is a radar signal based on the correlation signal and the gain control signal.
IEEE sections 802.11, 802.11(a), 802.11(b), 802.11(g), 802.11(h), 802.11(n), 802.16, 802.20, which are hereby incorporated by reference, define ways for configuring wireless networks and devices. According to these standards, a wireless network device may operate in either an an infrastructure mode or an ad-hoc mode.
The radar detection module 14 confirms whether the RF signal is chirp radar by further determining if an absolute value of (di−di-1) for all i's is less than a predetermined threshold. If true, the change in frequency is linear, and the RF signal is chirp radar. The radar detection module 14 generates an is Chirp signal.
Thus, the radar detection module 14 determines if the RF signal is chirp radar if di exceeds a predetermined threshold and if abs(di−di-1) is less than a predetermined threshold. FIG. 12 shows an even distribution of number of zero crossings when pulses of chirp radar are centered at center frequency of the DFS-enabled device that is receiving the radar signal. FIG. 13 shows an uneven distribution of number of zero crossings when pulses of chirp radar are not centered at center frequency of the DFS-enabled device that is receiving the radar signal.
If the DFS module 22 determines that the RF signal is a radar signal, the system 10 determines that the channel should be changed. The system 10 controls interruption of normal operation of the network device 24. The system 10 accomplishes this by not enabling radar detection and DFS in response to every RF interference received. Instead, the system 10 screens and qualifies an input RF signal before enabling radar detection and DFS. For example, the system 10 generates a dfsDetected signal to indicate that the network device 24 should change the channel if the received RF signal is a single tone radar or chirp radar with parameters that match those of known radar signals, or if the received RF signal is a pulse of a very short duration.
a radio frequency transceiver to receive a radio frequency signal on a first channel;
an automatic gain control circuit having a gain, wherein the gain i) changes from a normal value in response to the radio frequency transceiver receiving the radio frequency signal, and ii) subsequently returns to the normal value after a period of time, and wherein the automatic gain control circuit is configured to determine a radio signal strength of the radio frequency signal based on the period of time taken by the gain of the automatic gain control circuit to return to the normal value;
a clear channel assessment circuit to perform a correlation of the radio frequency signal with a predetermined sequence of a wireless data packet to determine whether the radio frequency signal contains the predetermined sequence, and in response to the radio frequency signal not containing the predetermined sequence, generate an indication that the radio frequency signal is not a wireless data packet;
a radar detector configured to determine whether the radio signal strength of the radio frequency signal exceeds a predetermined threshold;
a controller to, in response to i) the radio signal strength of the radio frequency signal exceeding the predetermined threshold and ii) the indication that the radio frequency signal is not a wireless data packet, divide the radio frequency signal into N equal segments, where N is an integer greater than one; count zero-crossings in each of the N equal segments; determine a difference between the zero-crossings in a first one of the N equal segments and the zero-crossings in a second one of the N equal segments; determine that the radio frequency signal is a chirp radar signal when the difference is greater than or equal to a predetermined zero-crossings threshold; and determine that the radio frequency signal is a tone radar signal when the difference is less than the predetermined zero-crossings threshold; and
a dynamic frequency selection circuit to change channel from the first channel to a second channel in response to the radio frequency signal being determined to be a chirp radar signal or a tone radar signal.
2. The system of claim 1, wherein the predetermined threshold is −64 dBm.
3. The system of claim 1, wherein the system is implemented within a wireless network device.
4. The system of claim 3, wherein the wireless network device is configured in accordance with one or more wireless networking standards including IEEE 802.11, 802.11 (a), 802.11 (b), 802.11 (g), 802.11 (h), 802.11 (n), 802.16, and 802.20.
5. The system of claim 3, wherein the wireless networking device is implemented in a high-definition television, a cellular phone, a set top box, of media player.
receiving a radio frequency signal on a first channel, wherein a gain of an automatic gain control module changes from a normal value in response to receiving the radio frequency signal, and ii) subsequently returns to the normal value after a period of time;
determining a radio signal strength of the radio frequency signal based on the period of time taken by the gain of the automatic gain control module to return to the normal value;
performing a correlation of the radio frequency signal with a predetermined sequence of a wireless data packet to determine whether the radio frequency signal contains the predetermined sequence;
in response to the radio frequency signal not containing the predetermined sequence, generating an indication that the radio frequency signal is not a wireless data packet;
determining whether the radio signal strength of the radio frequency signal exceeds a predetermined threshold;
in response to i) the radio signal strength of the radio frequency signal exceeding the predetermined threshold and ii) the indication that the radio frequency signal is not a wireless data packet, dividing the radio frequency signal into N equal segments, where N is an integer greater than one; counting zero-crossings in each of the N equal segments; determining a difference between the zero-crossings in a first one of the N equal segments and the zero-crossings in a second one of the N equal segments; determining that the radio frequency signal is a chirp radar signal when the difference is greater than or equal to a predetermined zero-crossings threshold; and determining that the radio frequency signal is a tone radar signal when the difference is less than the predetermined zero-crossings threshold; and
changing from the first channel to a second channel in response to the radio frequency signal being determined to be a chirp radar signal or a tone radar signal.
7. The method of claim 6, wherein the predetermined threshold is −64 dBm.
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Patent Publication Number: 20100202359
Inventors: Bhaskar V. Nallapureddy (Sunnyvale, CA), Tsunglun Yu (Cupertino, CA), Yungping Hsu (Saratoga, CA), Sek Kin Neng (Cupertino, CA)
Application Number: 12/761,937
International Classification: H04L 27/06 (20060101); G01S 7/02 (20060101);