Communications: directive radio wave systems and devices (e.g. – Radar ew
Reexamination Certificate
2003-02-03
2004-04-27
Lobo, Ian J. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
C342S195000, C342S444000
Reexamination Certificate
active
06727840
ABSTRACT:
BACKGROUND OF THE INVENTION
1.0 Field of the Invention
The present invention relates to an Electronic Support Measure (ESM) system and, more particularly, to a circuit for removing interference signals from the frequency spectrum of the RF signals incoming to and being analyzed by the ESM system.
2.0 Description Related to the Prior Art
Electronic Support Measure (ESM) system, such as a prior art ESM system
10
shown in
FIG. 1
herein, often employ a single, Wide Bandwidth Receiver
12
, for measuring RF frequency parameters on RF signals received via an Omnidirectional antenna
14
. This single serial arrangement is in parallel with a multi-channel receiver, such as Crystal Video Receiver (CVR)
16
, operatively cooperating with a Constant Beamwidth Lens (CBL) antenna
18
, providing, in a manner to be described, quantities
20
comprising RF amplitude, pulse width, Time Of Arrival (TOA), and Direction Finding (D/F) data associated with the incoming RF signal.
In operation, an incoming RF signal entering the Omnidirectional antenna
14
is detected and the RF signal frequency parameters thereof are estimated and sent, by way of the Wide Band Receiver
12
, to the System Digital Processor
22
. Simultaneously, an adjacent Constant Beamwidth Lens (CBL) Antenna
18
receives the same RF input. The CBL antenna
18
, as well as the Crystal Video Receiver (CVR)
16
, is comprised of multiple receiving elements. The multiple elements, as well as RF signal portions, are identified herein by the use of subscripts. When appropriate, a grouping of elements is simply referred to by its generic reference number. Each portion
18
1
,
18
2
. . .
18
M
of the RF signal received by CBL antenna
18
is delivered to a single Constant Bandwidth Lens (CBL)
24
which focuses the received RF signal, dependent on the azimuth of the RF source relative to the receiving elements, to multiple parallel lens RF outputs
26
1
,
26
2
. . .
26
N
. Each lens RF output
26
1
,
26
2
. . .
26
N
serving as channels is provided for by the Crystal Video Receiver (CVR)
16
, consisting of an RF band filters
28
1
,
28
2
. . .
28
N
, protective RF Limiters
30
1
,
30
2
. . .
30
N
, and Detector Log Video Amplifiers (DLVA)
32
1
,
32
2
. . .
32
N
. Following RF filtering appropriate to the RF band of interest, the DLVA
32
logarithmically detects the input RF signal amplitude and each CVR channel respectively produces an analog video voltage output
34
1
,
34
2
. . .
34
N
proportional to the logarithm of the RF input signal envelope power to be further described hereinafter with reference to
FIGS. 3 and 4
. To permit processing of a wide range of RF input duty cycles, (including CW) outputs of the CVR elements
32
1
,
32
2
. . .
32
N
are DC coupled.
The multiple parallel video outputs from the CVR elements
32
1
,
32
2
. . .
32
N
on signal paths
34
1
,
34
2
. . .
34
N
are provided to a Digitizer/Angle Encoder
36
, where each RF amplitude video input is digitized. Multiple adjacent digitized video inputs on signal paths
34
1
,
34
2
. . .
34
N
are compared with each other to determine the relative azimuth of the RF signal source, using a relative amplitude comparison process. The highest level RF video input on signal paths
34
1
,
34
2
. . .
34
N
is processed to estimate the RF input signal power level, the RF input signal pulse width, and the TOA. This parametric data derived by the Digitizer/Angle Encoder
36
, are sent to the System Digital Processor
22
where these data are combined with the RF frequency data received from wide band receiver
12
and then analyzed by the System Digital Processor
22
to determine the type of RF signal source and relative azimuth of the signal source generating the incoming RF signal.
The ESM System
10
of
FIG. 1
, particularly suited for shipboard use, is a typical design. In practice, the Omnidirectional antenna
14
and the Wide Band Receiver
12
usually provides hemispherical coverage, with two systems employed, each covering one side of a ship. Similarly, the CBL Antenna
18
usually provides instantaneous coverage of a single quadrant, with two CBL Antennas
18
and two Crystal Video Receiver
16
per one Omnidirectional antenna
14
and Wide Band Receiver
12
.
The number of CVR
16
channels per CBL Antenna
18
depends on the RF frequency band coverage associated with the incoming RF signals and the desired azimuth measurement resolution; typically, this varies from ten to twenty CVR element grouping per CBL Antenna
18
. For example, a CVR
16
having twenty (20) channels requires band filters
28
1
,
28
2
. . .
28
20
. The instantaneous RF frequency coverage of a system is usually restricted to a 3:1 bandwidth, for example, 2-6 GHz or 6-18 GHz. A full shipset, covering 2-18 GHz, might then require four Omnidirectional antennas
14
and Wide Band Receivers
12
(one per ship side per band); and each Omnidirectional antenna
14
and Wide Band Receiver
12
would require two Crystal Video Receivers
16
(one per quadrant). Each Crystal Video Receiver
16
would require (typically) fifteen groups of elements
28
,
30
, and
32
. The total elements
28
,
30
and
32
, per ship, is approximately one hundred and twenty units.
The ESM System
10
has generally proven to be accurate and cost effective. There is, however, a problem with local interference, particularly with own-ship CW emitters (such as CW target illuminators and SATCOM related signals). More particularly, an own-ship CW signal existing in the ESM System
10
operating band and received above the ESM System
10
operating threshold, set for its receiving elements, will be detected and processed by both the single serial arrangement of the Omnidirectional antenna
14
and Wide Band Receiver
12
and the parallel operating CBL antenna
18
and the CVR
16
. Any other received RF signal that is of lesser RF power at these antennas
14
or
18
will be obscured by this own-ship signal; if the other signal is associated with a threat, a serious condition occurs, that is, where an own-ship signal has blinded the ESM System
10
to the existence of the threat.
Normally, own-ship interfering signals, such as those generated by CW emitters, are eliminated with the use of fixed or tunable RF notch filters. This approach is useful and effective for the single serial arrangement of the Omnidirectional antenna
14
and Wide Band Receiver
12
, but is not useful for the parallel operating CBL antenna
18
and CVR
16
. More particularly, consider that a typical installation employs only four serial arrangements of the Omnidirectional antenna
14
and Wide Band Receiver
12
, but requires one hundred twenty grouping of CVR
16
elements
28
,
30
, and
32
to support the parallel operation of the CBL antenna
18
and CVR
16
. Further, if multiple signals are present and one signal frequency is suppressed in the single serial arrangement of the Omnidirectional antenna
14
and Wide Band Receiver
12
, but not in the parallel operating CBL antenna
18
and CVR
16
, the system is likely to produce RF frequency data from one emitter and RF amplitude, TOA, pulse width, and AOA data from a different emitter. Solutions to this problem have, to date, focused on trapping out the interference in the single serial arrangement of the Omnidirectional antenna
14
and Wide Band Receiver
12
, reducing the sensitivity of both the Wide Band Receiver
12
and the CVR
16
, and shielding the CBL Antennas
18
from the interference. None of these solutions or combinations therefore has proved satisfactory. It is desired to provide an ESM System that reduces or even eliminates the operational detrimental local interference effects created by own-ship emitters, while minimizing the additional circuitry needed to accomplish the elimination.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an ESM system successfully operated on a ship and that reduces or even eliminates the operational detrimental local interference effects created by own-ships emitters, while m
Lobo Ian J.
Wobensmith, III Zachary T.
LandOfFree
Interference suppression circuit and method thereof for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Interference suppression circuit and method thereof for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interference suppression circuit and method thereof for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3262377