 Apparatus and method for billing in a wireless communication system |
| In order to address this need and others, the present invention provides a method and an apparatus ... |
|
| High speed squelch circuit |
| It is, accordingly, the principle object of this invention to provide a novel and improved squelch ... |
|
| Muting circuit |
| What is claimed is: 1. In a receiver including carrier selection means for tuning to a selected ... |
|
| Data eye monitor |
| I claim: 1. A data eye monitor for a data input signal comprising: first means for comparing said ... |
|
| Single-sideband radiotelephone system |
| The present invention relates to a single-sideband radio system which may be used for ... |
|
| Wideband FM modulator and AFC control loop therefor |
| The present invention pertains to an improved digital frequency discriminator for use in a wideband ... |
|
| Extremely accurate automatic frequency control circuit and method therefor |
| The above and other objects are achieved by an automatic frequency control circuit which receives ... |
|
| Receiver data gate with automatic gain control |
| OF THE PREFERRED EMBODIMENT Referring to the Figure, a telephone system, such as a private branch ... |
|
| Picture transmission system using secondary differential variable sampling rate coding |
| Accordingly, the principal object of the present invention is to provide a picture transmission ... |
|
|
Jamming suppression of spread spectrum antenna/receiver systems
| Details |
Inventors: Holmes, Jerry D.; Barron, Kenneth S.; Reid, Anthony;
Assignee: Raytheon Company (Lexington, MA)
Primary Examiner: Chin; Stephen
Assistant Examiner: Ghayour; Mohammad
Attorney, Agent or Firm: Baker Botts L.L.P.
A jamming suppression system which includes a plurality of receivers for receiving electromagnetic radiations and a separate notch filter coupled to each receiver for filtering selected frequencies from electromagnetic radiations received by each of the receivers. In accordance with one embodiment of the invention, a spatial combiner responsive to the outputs of each of the notch filters extracts essentially jam-free information from the electromagnetic radiations. In accordance with a second embodiment of the invention, a plurality of spatial combiners, each responsive to the outputs of each of the notch filters, extracts essentially jam-free information from the electromagnetic radiations. The notch filters are adaptive notch filters for on-line selection of their filtering action. One of the notch filters is a master filter and the remainder of the notch filters are slave filters controlled by the master filter. In both embodiments, spatial filtering action is accomplished using a generalized sidelobe canceler that permits gain (relative to an isotropic antenna) to be preserved in the direction of one or more satellites while casting spatial mulls in the directions of inadvertent friendly or hostile jamming signals. |
|
DETAILED DESCRIPTION In accordance with the present invention, there is provided an improved jamming suppression technique and system for spread spectrum antenna/receiver systems.
Briefly, according to one feature of the invention, the temporal filters precede the spatial combiner, resulting in the suppression of narrowband jamming signals to a degree that would be much more difficult using spatial techniques.
Having the temporal filters precede the spatial combiner results in the suppression of narrowband jamming signals before the spatial adaptation algorithm is invoked.
This allows the spatial adaptation algorithm to apply all degrees of freedom to the remaining jammers, all of which are broadband.
As an example of what could otherwise happen, assume the strongest jamming signals into the antenna are narrowband.
If the spatial adaptation were attempted first, then it would cast spatial nulls in the direction of the strong narrowband jammers.
Every null so cast is one less null that is available for broadband jammer suppression.
(The temporal finite impulse response (FIR) filter is unable to suppress the broadband jamming signals without also suppressing the GPS signal by the same amount or more.
) Having one spatial combiner per GPS satellite signal to be acquired/tracked rather than a single spatial combiner for all GPS satellite signals to be acquired/tracked, is also highly desirable.
In some spatial adaptation schemes, one may use spatial degrees of freedom in the following way: one degree of freedom is required per angle where a null is cast, and one degree of freedom is required per angle required to be protected from nulling (in this case, the GPS satellite signal angle of arrival).
If only a single spatial combiner is used, and if six GPS satellites are being acquired/tracked, then the first six degrees of freedom could be required just to retain gain toward the GPS satellites.
If several spatial nulls are required, then a very large number of antenna/receiver channels are required
|
|
Multiplexer-related 
