Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Reexamination Certificate
1999-01-29
2001-03-06
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
C342S385000, C342S417000, C342S422000, C342S423000
Reexamination Certificate
active
06198436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to Electronic Surveillance Measurement (ESM) receivers and more particularly relates to the use of phase receivers in determining frequency and angle-of-arrival (AOA) in ESM receivers.
2. Description of the Prior Art
Electronic Surveillance Measurement (ESM) receivers commonly require that both frequency and angle-of-arrival (AOA) calculations be performed on input signals from targets of interest. Usually, frequency is measured first, with the measurement spanning a wide instantaneous bandwidth to maximize probability of signal intercept. After a signal of interest is detected and its frequency is determined, the bandwidth of measurement is narrowed substantially for the determination of AOA. Centering a narrow measurement band around the signal frequency improves signal separation in a multi-signal environment, and reduces the influence of receiver noise on the accuracy of the AOA measurement. Prior art uses separate systems to measure each of these two parameters. The frequency of the input signals is often measured using an Instantaneous Frequency Measurement (IFM) device as illustrated in FIG.
1
A. The AOA is typically measured using an interferometer as illustrated in FIG.
1
B. Both the IFM and the interferometer use the difference in phase between the received input signals to calculate the frequency and the AOA of the input signals.
The IFM illustrated in
FIG. 1A
includes a receptor element
10
, a delay line
12
and an N-channel phase receiver
14
. The input signals
16
are received from the target by the receptor element
10
, such as an antenna. The received input signals
16
are then applied to the delay line
12
, which provides two or more output signals delayed in time and thus relative phases, to the N-channel phase receiver
14
. The frequency of the received input signals
16
are determined by the difference in phase between inputs to the N-channel phase receiver
14
by means well known in the art. Phase receivers are alternatively referred to as phase discriminators, phase correlators or quadrature mixers. Further detail regarding phase receivers is presented in the product specification catalog entitled
Anaren RF
&
Microwave Components,
February 1997, distributed by Anaren Microwave, Inc., 6635 Kirkville Road, East Syracuse, N.Y. 13057, which is hereby incorporated by reference in its entirety.
The interferometer illustrated in
FIG. 1B
includes the receptor elements
10
(such as antennas), and the N-channel phase receiver
14
. The receptor elements
10
are offset by a predetermined distance d. The interferometer uses the difference in phase between the input signals received by the offset receptor elements
10
to determine the AOA. The sine of the AOA &thgr; of the input signals
16
is proportional to the phase difference between the input signals received by the offset receptor elements
10
in accordance with equation (1) as follows:
Phase difference=2&pgr; sin&thgr;
d/&lgr;
(1)
Thus, both the interferometer and the IFM utilize N-channel phase receivers as a means for calculating the AOA and the frequency of the input signal, respectively.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an integrated interferometer and Instantaneous Frequency Measurement (IFM) receiver, which calculates the frequency and the angle-of-arrival (AOA) of input signals using a shared N-channel phase receiver.
It is a further object of the present invention to provide an integrated interferometer and IFM receiver, which is less costly to produce and maintain than interferometers and IFM devices manufactured as separate and distinct units.
It is still a further object of the present invention to provide an integrated interferometer and IFM receiver, which occupies less space than interferometers and IFM devices manufactured as separate and distinct units.
It is still a further object of the present invention to provide an integrated interferometer and IFM receiver, which is less complex to maintain than interferometers and IFM devices manufactured as separate and distinct units.
It is still a further object of the present invention to provide an integrated interferometer and IFM receiver, which is more easily calibrated than interferometers and IFM devices manufactured as separate and distinct units.
In accordance with one form of the present invention, an integrated receiver including an IFM, an interferometer and switches for selectively connecting the shared N-channel phase receiver to the IFM when the IFM is determining the frequency of the signals, and selectively connecting the shared N-channel phase receiver to the interferometer when the interferometer is determining the AOA of the signals is provided. The IFM receives signals from a target and determines the frequency of the signals. The IFM includes the shared N-channel phase receiver. The interferometer also receives the signals from the target and determines the AOA of the signals. The interferometer includes the shared N-channel phase receiver, and shares the shared N-channel phase receiver with the IFM. The shared N-channel phase receiver determines phase information indicative of the frequency of the signals and the AOA of the signals. The integrated receiver may also include an amplitude measurement circuit responsive to the signals, which determines amplitude-based parameters of the signals.
In accordance with another form of the present invention, a method for calculating the frequency and the AOA of the signals from the target is provided, which includes the steps of receiving the signals, determining the frequency of the signals using a shared N-channel phase receiver, and determining the AOA of the signals using the shared N-channel phase receiver. The method may also include the step of determining amplitude-based parameters of the signals.
Previously, interferometers and IFM devices were operated as separate and distinct units having unique N-channel phase receivers. By implementing an integrated interferometer and IFM, the same N-channel phase receiver may be shared between the interferometer and the IFM and used for both AOA and frequency measurements, respectively.
REFERENCES:
patent: 4481519 (1984-11-01), Margerum
patent: 5315307 (1994-05-01), Tsui et al.
patent: 5563982 (1996-10-01), Wang et al.
Ail Systems, Inc.
Gregory Bernarr E.
Hoffmann & Baron , LLP
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