Joon Y Choe

US Patent:

7408507, Aug 5, 2008

Filed:

Mar 14, 2006

Appl. No.:

11/376633

Inventors:

Eung Gi Paek - Germantown MD, US
Mark Parent - Port Tobacco MD, US
Joon Y Choe - Potomac MD, US

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H01Q 3/00
H01Q 3/22
G01S 1/44

US Classification:

342368, 342398, 342375

Abstract:

A phased array antenna system includes an RF front end, a radome, and an optical calibrator embedded in the radome for enabling in-situ calibration of the RF front end. The optical calibrator employs an optical timing signal generator (OTSG), a Variable Optical Amplitude and Delay Generator array (VOADGA) for receiving the modulated optical output signal and generating a plurality of VOADGA timing signals, and an optical timing signal distributor (OTSD). The in-situ optical calibrator allows for reduced calibration time and makes it feasible to perform calibration whenever necessary.

US Patent:

7535409, May 19, 2009

Filed:

Dec 18, 2006

Appl. No.:

11/612153

Inventors:

Joon Y Choe - Potomac MD, US
Eung Gi Paek - Germantown MD, US

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G01S 13/02
G01S 13/89
H01Q 3/00

US Classification:

342159, 342 54, 342 82, 342179, 342196, 342368

Abstract:

A time-reversal imaging radar system for acquiring an image of a remote target includes an antenna array having a plurality of spaced-apart antennas, and a transceiver coupled to the antenna array for alternately transmitting a radar signal via the antenna array toward the target and for receiving target-reflected radar signals. The transceiver includes means for multiple-pass time-reversing the transmitted and received radar signals whereby coherent beam focusing is realized at both the target and at the receiver to thereby enhance the resolution of the acquired target image.

US Patent:

7671799, Mar 2, 2010

Filed:

Jun 25, 2008

Appl. No.:

12/145601

Inventors:

Eung Gi Paek - Germantown MD, US
Mark G Parent - Port Tobacco MD, US
Joon Y Choe - Potomac MD, US

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H01Q 3/00
H01Q 19/06
H01S 3/00

US Classification:

342368, 343753, 359344

Abstract:

A phased array antenna system includes an RF front end, a radome, and an optical calibrator embedded in the radome for enabling in-situ calibration of the RF front end. The optical calibrator employs an optical timing signal generator (OTSG), a Variable Optical Amplitude and Delay Generator array (VOADGA) for receiving the modulated optical output signal and generating a plurality of VOADGA timing signals, and an optical timing signal distributor (OTSD). The in-situ optical calibrator allows for reduced calibration time and makes it feasible to perform calibration whenever necessary.

US Patent:

8264397, Sep 11, 2012

Filed:

Oct 26, 2010

Appl. No.:

12/911817

Inventors:

Eung Gi Paek - Germantown MD, US
Joon Y Choe - Potomac MD, US

Assignee:

The United States of America, as represented by the Secretary of the Navy - Washington DC

International Classification:

G01S 13/00

US Classification:

342 31, 342145

Abstract:

A Time Transfer Time Reverse Mirror (TT TRM) method and system includes a radio transceiver for transmitting a series of short pulses repeatedly at a period T and for receiving from a remote node a return signal that is a retransmission of the original signal at the same period T: a clock circuit for inputting a clock signal to the transceiver: and a computer for (i) computing and generating an imaginary time-reversed signal version of the original signal, (ii) comparing the return signal with the imaginary version, (iii) computing a delay between the return signal and the imaginary version that is substantially equal to twice the time difference between the two nodes, and (iv) applying the computed delay to a clock input calibration for a desired signal. The system includes time transfer using the ionospheric reflection (refraction), producing precise synchronization among remote nodes beyond the line-of-sight and thus without necessitating GPS or communication satellites.

US Patent:

8350750, Jan 8, 2013

Filed:

Nov 18, 2010

Appl. No.:

12/948841

Inventors:

Eung Gi Paek - Germantown MD, US
Joon Y Choe - Potomac MD, US

Assignee:

The United States of America, as represented by the Secretary of the Navy - Washington DC

International Classification:

G01S 13/89

US Classification:

342103, 342 25 E, 342 25 F, 342125, 342179

Abstract:

A distributed time reversal mirror array (DTRMA) system includes a plurality of independent, sparsely distributed time reversal mirrors (TRMs). Each of the TRMs includes an antenna; a transceiver connected to the antenna for transmitting a signal toward a target, for receiving a return, reflected signal from the target, and for retransmitting a time-reversed signal toward the target: means for phase-locking and for maintaining spatial and temporal coherences between the TRMs; and a computer including a machine-readable storage media having programmed instructions stored thereon for computing and generating the time-reversed retransmitted signal, thereby providing a phased array functionality for the DTRMA while minimizing distortion from external sources. The DTRMA is capable of operating in an autonomous, unattended, and passive state, owing to the time-reversal's self-focusing feature. The beam may be sharply focused on the target due to the coherently synthesized extended aperture over the entire array.

US Patent:

51325861, Jul 21, 1992

Filed:

Apr 4, 1991

Appl. No.:

7/680864

Inventors:

Kevin Boulais - Silver Spring MD
Joon Choe - Potomac MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H01J 4304
H01J 4300

US Classification:

313105CM

Abstract:

A microchannel plate device utilizing a semiconducting bulk material is cacterized by electron emissions of high output current density and efficiency. The channel passages in the plate device which are square in cross-section accommodates a larger open area ratio at the input and output plate surfaces. An extended range of high electron emission applications for the plate device is provided. Such applications may include a photocathode installation to which a modulation pulse input is applied under low voltages isolated from high post-accelerating voltages.

US Patent:

54345839, Jul 18, 1995

Filed:

May 23, 1994

Appl. No.:

8/247827

Inventors:

Philip W. Hesse - Ellicott City MD
Han S. Uhm - Potomac MD
Joon Choe - Potomac MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

H01Q 128

US Classification:

343705

Abstract:

Signal antennae are mounted on the casing wall between forward nose and r tail ends of an aerospace launched vehicle for radio communication through a radiation conducting sheath of plasma formed thereon by atmospheric ionization during descent of the vehicle along a non-gliding reentry path. The reentry path is maintained by vehicle guidance at a steep angle in response to data transmitted to the antennae through the radiation conducting sheath having a plasma content minimized by cooling which is thereby maintained in complete surrounding relation to the vehicle and modulated to enhance data transmission during the entire duration of vehicle descent.