US4318099A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Clutter filter using a minimum number of radar pulses
Assignee: United States Department of the Navy
•
Filing: 1980-02-21
•
Granted: 1982-03-02
•
Expires: 2000-02-21
Abstract
Abstract A clutter filter which reduces by (N-1) the number of input pulses requiredor operation of an N-pulse MTI canceler when L>N consecutive filtered outputs are desired. The clutter filter includes the two channels of an N-pulse MTI canceler which weight and sum the in-phase and quadrature-phase components of N radar returns, and a pair of delay circuits which introduce a delay of N interpulse time periods to the N and subsequent in-phase and quadrature-phase components of the radar returns. The stored outputs of the two channels of the canceler and the consecutive outputs of the delay circuits are combined in a complex multiplier to generate the consecutive in-phase and quadrature-phase outputs of the filter. The clutter filter has utility in a multiple-stage filter system employing a Doppler filter as the last stage.
Inventors
- 👤 James K. Hsiao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:00
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/522; G01S13/524; G01S13/526
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
178 words
A clutter filter using a minimum number of radar pulses, comprising: input means for receiving a series of phase-detected radar returns in digital form, the radar returns having a fixed interpulse time period; canceling means for weighting and summing N of the phase-detected radar returns to cancel clutter signals, where N is an integer; store means; first switching means for connecting the canceling means to the input means during receipt of the N returns and disconnecting the canceling means from the input means thereafter; second switching means for disconnecting the canceling means from the store means during receipt of the N returns and connecting the canceling means to the store means for an interval less than the interpulse time period thereafter; first delay means coupled to the input means for introducing a delay equal to N interpulse time periods to each of the phase-detected radar returns; and a complex multiplier connected to the store means and to the first delay means for generating more than N filtered outputs with (N-1) less pulses than required by an N-pulse canceler.
Claim 2
Dependent Claim
178 words
A clutter filter using a minimum number of radar pulses, comprising: input means for receiving a series of phase-detected radar returns in digital form, the radar returns having a fixed interpulse time period; canceling means for weighting and summing N of the phase-detected radar returns to cancel clutter signals, where N is an integer; store means; first switching means for connecting the canceling means to the input means during receipt of the N returns and disconnecting the canceling means from the input means thereafter; second switching means for disconnecting the canceling means from the store means during receipt of the N returns and connecting the canceling means to the store means for an interval less than the interpulse time period thereafter; first delay means coupled to the input means for introducing a delay equal to N interpulse time periods to each of the phase-detected radar returns; and a complex multiplier connected to the store means and to the first delay means for generating more than N filtered outputs with (N-1) less pulses than required by an N-pulse canceler.
Claim 3
Dependent Claim
73 words
The clutter filter recited in claim 1 wherein the canceling means includes: second delay means coupled to the switching means for introducing successive delays equal to the fixed interpulse time period to the N phase-detected radar returns; multiplying means coupled to the second delay means for multiplying the successively delayed N phase-detected radar returns by selected coefficients; and summing means coupled to the multiplying means for summing the multiplied N phase-detected radar returns.
Claim 4
Dependent Claim
359 words
A clutter filter using a minimum number of radar pulses, comprising: input means for receiving a series of phase-detected radar returns in digital form, the radar returns having a fixed interpulse time period; first canceling means for weighting and summing N of the phase-detected radar returns to cancel clutter signals, where N is an integer; first store means; a pair of nodes; first switching means for connecting the first canceling means to the pair of nodes during receipt of the N returns and disconnecting the first canceling means from the pair of nodes thereafter; second switching means for disconnecting the first canceling means from the first store means during receipt of the N returns and connecting the first canceling means to the first store means for an interval less than the interpulse time period thereafter; first delay means coupled to the pair of nodes for introducing a first delay equal to N interpulse time periods to each of N+N 1 of the phase-detected radar returns, where N+N 1 is an integer; a first complex multiplier connected to the first store means and the first delay means for generating N 1 outputs; second canceling means coupled to the first complex multiplier for weighting and summing the N 1 outputs of the first complex multiplier; second store means; third switching means for connecting the pair of nodes to the input means during receipt of N+N 1 returns and disconnecting the pair of nodes from the input means thereafter; fourth switching means for disconnecting the second canceling means from the second store means during receipt of N+N 1 returns and connecting the second cancelling means to the second store means for an interval less than the interpulse time period thereafter; second delay means coupled to the input means for introducing a delay equal to (N+N 1 ) interpulse time periods to each of the phase-detected radar returns; a second complex multiplier connected to the second store means and to the second delay means for generating more than (N+N 1 ) filtered outputs with (N+N 1 -2) less pulses than required by an N-pulse canceler and an N 1 -pulse canceler in cascade.
Claim 5
Dependent Claim
359 words
A clutter filter using a minimum number of radar pulses, comprising: input means for receiving a series of phase-detected radar returns in digital form, the radar returns having a fixed interpulse time period; first canceling means for weighting and summing N of the phase-detected radar returns to cancel clutter signals, where N is an integer; first store means; a pair of nodes; first switching means for connecting the first canceling means to the pair of nodes during receipt of the N returns and disconnecting the first canceling means from the pair of nodes thereafter; second switching means for disconnecting the first canceling means from the first store means during receipt of the N returns and connecting the first canceling means to the first store means for an interval less than the interpulse time period thereafter; first delay means coupled to the pair of nodes for introducing a first delay equal to N interpulse time periods to each of N+N 1 of the phase-detected radar returns, where N+N 1 is an integer; a first complex multiplier connected to the first store means and the first delay means for generating N 1 outputs; second canceling means coupled to the first complex multiplier for weighting and summing the N 1 outputs of the first complex multiplier; second store means; third switching means for connecting the pair of nodes to the input means during receipt of N+N 1 returns and disconnecting the pair of nodes from the input means thereafter; fourth switching means for disconnecting the second canceling means from the second store means during receipt of N+N 1 returns and connecting the second cancelling means to the second store means for an interval less than the interpulse time period thereafter; second delay means coupled to the input means for introducing a delay equal to (N+N 1 ) interpulse time periods to each of the phase-detected radar returns; a second complex multiplier connected to the second store means and to the second delay means for generating more than (N+N 1 ) filtered outputs with (N+N 1 -2) less pulses than required by an N-pulse canceler and an N 1 -pulse canceler in cascade.
Claim 6
Dependent Claim
75 words
The clutter filter recited in claim 3 wherein the first canceling means includes: third delay means coupled to the first switching means for introducing successive delays equal to the fixed interpulse time period to the N phase-detected radar returns; multiplying means coupled to the third delay means for multiplying the successively delayed N phase-detected radar returns by selected coefficients; and summing means coupled to the multiplying means for summing the multiplied N phase-detected radar returns.
Claim 7
Dependent Claim
86 words
The clutter filter recited in claim 3 wherein the second canceling means includes: third delay means coupled to the first complex multiplier for introducing successive delays equal to the fixed interpulse time period to the N 1 outputs of the first complex multiplier; multiplying means coupled to the third delay means for multiplying the successively delayed N 1 outputs of the first complex multiplier by selected coefficients; and summing means coupled to the multiplying means for summing the N 1 outputs of the first complex multiplier.
References Cited (Backward Citations)
US3631490A
Cited
US3797016A
Cited
US4035799A
Cited
US4153899A
Cited
US4217584A
Cited
US4137532A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-03-01 | 1985-08-31 | 1986-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-03-01 | 1989-08-31 | 1990-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-03-01 | 1993-08-31 | 1994-03-02 | $7700.00 | Window Closed / Lapsed |