Antenna control unit attenuator and Bi-phase modulator

#This invention relates to wideband communications and more particularly to minimizing the effects of interference in a radio receiver system utilizing an adaptive antenna array.

#Any communication system is susceptible to degradation due to interfering conditions. In a wideband transmission system the desired signal is vulnerable to interruption by natural phenomena, interference from other signals, or countermeasures. Countermeasures may take the form of a variety of jamming schemes whose sole purpose is to disrupt the operation of a receiver.

#A variety of techniques are currently used to decrease the effects of interference in receivers. Frequency agility, sensitivity time control, sidelobe blanking, random PRF and sidelobe cancellation are but a few of the well known techniques for countering interfering signals. Jammer signals are often non-pulsed or continuous wave and may be sinusoidal, modulated or noise like in nature.

#FIG. 1 is a block diagram of the wideband receiver system capable of incorporating the teachings of the present invention;

#FIG. 2 is a block diagram of a portion of a GPS receiver incorporating the teachings of the present invention;

#FIG. 3 is a block diagram of a portion of the antenna control unit of FIG. 2;

#Referring now to the drawings wherein like items are referenced as such throughout, FIG. 1 illustrates a block diagram of certain portions of a GPS receiver system 10 (such as available from the Assignee) in which the teachings of the present invention may be incorporated. It should be noted that a GPS receiver is used for illustration purposes only and does not imply a limitation for the teachings of the present invention.

#A variety of signals, depicted for illustration purposes as a desired signal 11 and an undesired signal 12, are received by an antenna array 14. GPS signals, the desired signal 11 in this instance, are centered at one of two frequencies, 1575.42 megahertz (MHz) and 1227.60 MHz, referred to as "L1" and "L2", respectively, and may be referred to as such throughout this document. The signals L1 and L2 detected by the antenna array 14 are then coupled to a antenna control unit 16. The antenna control unit 16 is then coupled to a receiver 20. The GPS signal is a spread spectrum signal, separated in signal processing. The reception of three satellites is needed to derive location.

#FIG. 2 illustrates a more detailed depiction of the antenna array 14 and the antenna control unit 16 of FIG. 1. The antenna array 14 is comprised of four antenna elements 101, 103, 105 and 107 which all detect the downlink signals from the constellation of GPS satellites (not shown). Although depicted as a four channel device, it is understood that any number of desired channels may be utilized. For the sake of simplicity only one channel is described in detail, the elements and connections of additional channels being substantially similar and easily understood from the provided drawings and specification. Signals that are detected by antenna element 107 are routed through a preselect filter 109, a low noise amplifier 119 and a complex weight function 129. (Similar processing is provided for the other three channels beginning with antenna elements means 101, 103 and 105). It should be noted that the filter 109 and the amplifier 119 are not required for the function of the control unit. The outputs of all complex weight function means 129, 131, 133 and 135 are summed via summing means 139 and 141 thereby forming an output signal 144.