Signal processing device, radar apparatus and method of processing signal

Patent metadata

Field	Value
Publication number	US-10677912-B2
Application number	US-201515546530-A
Country	US
Kind code	B2
Filing date	Dec 15, 2015
Priority date	Feb 4, 2015
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A signal processing device and method to accurately detect a distress signal from a search and rescue transponder and reduce a calculation load for the detection. The device may include an instantaneous frequency change rate calculating module configured to calculate a change rate of an instantaneous frequency of a complex reception signal generated from a reception wave received by a wave receiver, a memory configured to store a value obtained based on a reference frequency sweeping speed that is a frequency sweeping speed of the distress signal, and a distress signal determining module configured to determine whether the distress signal is issued from the search and rescue transponder, based on a comparison result between the instantaneous frequency change rate calculated by the instantaneous frequency change rate calculating module and the value obtained based on the reference frequency sweeping speed stored in the memory.

First claim

The invention claimed is:

1. A signal processing device for detecting a distress signal from a search and rescue transponder, comprising:
a memory configured to store a value obtained based on a reference frequency sweeping speed that is a frequency sweeping speed of the distress signal; and
processing circuitry configured
to calculate an instantaneous frequency by differentiating a phase of a complex reception signal with time, the complex reception signal being generated from a reception wave received by a wave receiver,
to calculate a change rate of the instantaneous frequency of the complex reception signal by differentiating the instantaneous frequency with time, and
to determine whether the distress signal is issued from the search and rescue transponder, based on a comparison result between the instantaneous frequency change rate and the value obtained based on the reference frequency sweeping speed stored in the memory.

2. The signal processing device of claim 1 , wherein,
the memory is further configured to store a higher limit threshold that takes a higher value than the reference frequency sweeping speed and a lower limit threshold that takes a lower value than the reference frequency sweeping speed, and
the processing circuitry is further configured to determine that the distress signal is included in the complex reception signal under a condition that the instantaneous frequency change rate is between the upper limit threshold and the lower limit threshold.

3. The signal processing device of claim 2 , wherein,
the processing circuitry is further configured
to calculate the instantaneous frequency change rate at a plurality of timings, and
to determine that the distress signal is included in the complex reception signal under a condition that the instantaneous frequency change rate that is between the upper limit threshold and the lower limit threshold is continuously obtained for at least a given number of times.

4. A radar apparatus, comprising:
a wave receiver configured to receive a reception wave;
the signal processing device of claim 3 , with the processing circuitry being further configured to detect the distress signal from the search and rescue transponder and generate a radar image of inside a detection area by processing the complex reception signal generated from the reception wave that is received by the wave receiver; and
a display configured to display information regarding the distress signal detected by the signal processing device and the radar image.

5. The radar apparatus of claim 4 , wherein, regarding a first area that is at least a part of the detection area, the signal processing device generates the radar image for a section of the first area where the distress signal is not detected by pulse-compressing the complex reception signal obtained from a reflection wave of a frequency modulated pulse that is a transmission wave, and the signal processing device generates the radar image for a section of the first area where the distress signal is detected by using the complex reception signal obtained from a reflection wave of a non-frequency-modulated pulse that is a transmission wave.

6. The radar apparatus of claim 4 , wherein
the processing circuitry is further configured
to fetch the reception signal in the transmission-and-reception period of the non-modulated pulse and to perform reception processing on a reception echo to extract reception echo data of the second area,
to fetch the reception signal during the transmission-and-reception period of the modulated pulse, to pulse-compress a reception echo, and to extract the reception echo data of the area, and
to combine the reception echo of the non-modulated pulse with the reception echo of the modulated pulse.

7. A radar apparatus, comprising:
a wave receiver configured to receive a reception wave;
the signal processing device of claim 2 , with the processing circuitry being further configured to detect the distress signal from the search and rescue transponder and generate a radar image of inside a detection area by processing the complex reception signal generated from the reception wave that is received by the wave receiver; and
a display configured to display information regarding the distress signal detected by the signal processing device and the radar image.

8. The radar apparatus of claim 7 , wherein, regarding a first area that is at least a part of the detection area, the signal processing device generates the radar image for a section of the first area where the distress signal is not detected by pulse-compressing the complex reception signal obtained from a reflection wave of a frequency modulated pulse that is a transmission wave, and the signal processing device generates the radar image for a section of the first area where the distress signal is detected by using the complex reception signal obtained from a reflection wave of a non-frequency-modulated pulse that is a transmission wave.

9. The radar apparatus of claim 7 , wherein
the processing circuitry is further configured
to fetch the reception signal in the transmission-and-reception period of the non-modulated pulse and to perform reception processing on a reception echo to extract reception echo data of the second area,
to fetch the reception signal during the transmission-and-reception period of the modulated pulse, to pulse-compress a reception echo, and to extract the reception echo data of the area, and
to combine the reception echo of the non-modulated pulse with the reception echo of the modulated pulse.

10. A radar apparatus, comprising:
a wave receiver configured to receive a reception wave;
the signal processing device of claim 1 , with the processing circuitry being further configured to detect the distress signal from the search and rescue transponder and generate a radar image of inside a detection area by processing the complex reception signal generated from the reception wave that is received by the wave receiver; and
a display configured to display information regarding the distress signal detected by the signal processing device and the radar image.

11. The radar apparatus of claim 10 , wherein,
regarding a first area that is at least a part of the detection area, the signal processing device generates the radar image for a section of the first area where the distress signal is not detected by pulse-compressing the complex reception signal obtained from a reflection wave of a frequency modulated pulse that is a transmission wave, and the signal processing device generates the radar image for a section of the first area where the distress signal is detected by using the complex reception signal obtained from a reflection wave of a non-frequency-modulated pulse that is a transmission wave.

12. The radar apparatus of claim 10 , wherein
the processing circuitry is further configured
to fetch the reception signal in the transmission-and-reception period of the non-modulated pulse and to perform reception processing on a reception echo to extract reception echo data of the second area,
to fetch the reception signal during the transmission-and-reception period of the modulated pulse, to pulse-compress a reception echo, and to extract the reception echo data of the area, and
to combine the reception echo of the non-modulated pulse with the reception echo of the modulated pulse.

13. A method of processing a signal, the method detecting a distress signal from a search and rescue transponder, comprising:
calculating an instantaneous frequency by differentiating a phase of a complex reception signal with time, the complex reception signal being g

Assignees

• Furuno Electric Co

Inventors

• Nakatani Fumiya

Classifications

• G01S7/12 Primary

  Plan-position indicators, i.e. P.P.I. · CPC title

• G01S13/767 Primary

  Responders; Transponders (teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26) · CPC title

• G01S13/30

  using more than one pulse per radar period · CPC title

• G01S7/292

  Extracting wanted echo-signals · CPC title

• G01S13/76

  wherein pulse-type signals are transmitted · CPC title