referring now to the drawings , wherein like numbers represent like parts in each of the several figures , fig1 depicts the known phenomenon that when two circularly polarized millimeter waves having equal amplitude and opposite directions of rotation are combined , they will produce a linearly polarized wave . the resultant linearly polarized vector will have a fixed orientation in space when the relative phase between the two circularly polarized waves is fixed . this known phenomenon is discussed in polarization - agile antennas , by wallace , zimmer , and johnson , 17th annual symposium on usaf antenna research and development , university of ill ., november , 1967 . the orientation of the plane of the linearly polarized vector is determined by the relative phase τ between the two circularly polarized waves . if a delay is introduced into the relative phase τ between the circularly polarized waves , the resultant linearly polarized vector will turn in space to a different orientation plane . if the phase delay is varied sinusoidally , the polarization vector will rotate in space at the modulation rate . this rotation of the vector is referred to as &# 34 ; polarization agility &# 34 ;, and a beam made up of rotating vectors referred to as &# 34 ; polarization - agile &# 34 ; beams . fig2 illustrates a prior art method of causing a linear polarization vector to rotate in space by means of a variable phase shifter 2 , with the rotating linearly polarized wave being transmitted into space as a radiated wave . in the system as shown in fig2 a millimeter wave input signal 3 is divided into two equal paths 5a and 5b by a power divider 4 , with one path having the means 2 for introducing a phase delay in the signal . the two signals are then coupled from the two paths 5a and 5b ( arms of a rectangular waveguide ) into a section of a square waveguide known as a dual - mode coupler 6 that allows simultaneous transmission of the two orthogonal linearly polarized millimeter waves along an output path 7 . the combined millimeter waves are introduced to a circular - to - linear polarization transducer 8 , then to an antenna 10 to provide a radiated polarization - agile wave . the superposition of two oppositely polarized coaxial circular millimeter waves is a linearly polarized wave . by varying the phase with the variable phase shifter 2 in one arm , the linearly polarized electric field vector is caused to rotate in space as is well known . if the phase is varied non - linearly , the rotation will be at different rates within a 360 ° rotation of the linearly polarized vector . fig3 illustrates one embodiment of the invention showing the use of a single nutating polarization - agile beam 12 for guiding a missile 14 that is moving through space . millimeter wave generator 15 generates an output wave that is coupled to a phase shifter 16 and to a linearly polarized wave generator 18 . the variable phase shifter ( or modulator ) 16 causes the polarized vector of the wave generated by millimeter wave generator 15 to rotate . the rate of rotation goes from f 1 to f 5 through a 360 ° rotation of the polarization vector , and at f 5 goes back to f 1 at the start of a new rotation cycle of the vector ( fig4 ). the wave from the phase shifter 16 goes to the linearly polarized wave generating device 18 for modulating the output therefrom . a nutating subreflector 20 is modulated by nutating subreflector drive circuit 22 at a frequency f n . the relationship between f 1 through f 5 , and f n is shown in fig4 wherein f 5 & gt ; f 1 & gt ;& gt ; f n . the change in rotation rate f 1 to f 5 of the linear vector of the polarization - agile beam 12 is synchronized with the rate of modulation of the nutating subreflector drive 22 by means of a synchronizer 24 . the signal generated by the linearly polarized wave generating device 18 is transmitted to the nutating subreflector 20 by means of a parabolic antenna 26 . missile 14 , flying in the centerline 30 formed by the nutation of the beam , has a single rearward looking polarized antenna 27 connected to receiver 28 that senses the amplitude of the modulation rate induced by the varying rotation frequency of the polarization vector of the beam and thereby establishes the specific radial of the nutation beam that it is located on . the amplitude of the modulation at a particular polarization vector rotation frequency establishes the distance out from the beam center on the radial , so the missile can establish its position in two coordinates , i . e . the particular radial and the distance out on the radial . from this information , guidance commands are developed to cause the missile to fly down the sight line 30 around which the beam 12 rotates . additionally , the rate of rotating the polarization vector of a linearly polarized beam 12 can go from a higher frequency to a lower frequency , and the rotation rate can vary continuously or in discrete steps . although the rotation rate can vary other than linearly , a linear rate of change is preferred , and best repeatability and stability is achieved by varying the rotation rate in discrete steps by digital control rather than by analog control . angular resolution capability is improved by increasing the difference between the highest rotation frequency and the lowest . an embodiment of a rearward - looking missile receiver 28 is shown in fig5 . a linearly polarized antenna 27 with the polarization vector aligned with either the azimuth or elevation plane of the missile converts the polarization - agile signals to amplitude modulated signals . the incoming amplitude modulated millimeter wave signal is received by antenna 27 . using a mixer 29 , this received signal is combined with a signal from local oscillator 30 to obtain a lower intermediate frequency , which is amplified in amplifier 31 , filtered in filter bank 32 and detected in detector bank 34 . filter bank 32 is comprised of filters 32a , 32b , 32c , and 32d which are coupled respectively to detector 34a , 34b , 34c , and 34d of detector bank 34 . the frequencies in the range f 1 - f 2 that correspond to or define the first quadrant of rotation of the guidance beam 12 , as shown in fig3 are filtered ( filter 32a ) and detected ( detector 34a ) and the output is applied to an error signal computer 36 . the frequencies f 2 - f 3 are likewise filtered and detected to provide an input to the error signal computer for the second quadrant , and frequencies f 3 - f 4 and f 4 - f 5 provide inputs to the error computer for quadrants 3 and 4 respectively . a nutation frequency filter 38 allows the nutation frequency to be coupled to a detector 40 . the output of detector 40 is coupled to computer 36 and used in conjunction with the nutation frequencies to provide the azimuth and elevation outputs . the preferred embodiment of the invention is shown in fig6 . instead of the nutating beam as shown in fig3 four polarization agility devices 50a - d are employed to produce a non - nutating four beam system modulated by respective polarization modulators 52a - d . each output beam 54a - d has a distinctly different polarization rotation frequency , f 6 , f 7 , f 8 , and f 9 , separated from each other to allow efficient filtering in a missile borne receiver 56 . a missile 14a with a rearward - looking linear antenna 58 and receiver 56 detects and filters all four modulating frequencies . the beams are arranged to overlap in space . under these conditions , the relative amplitudes of the four modulating linearly polarized agile waves provide coordinate information relative to the center line 60 that is established by the four beams . if the missile is flying down the center line of the four beams , the amplitudes of the four modulation frequencies that are received by receiver 56 are the same , and no commands to the missile are required . the relative amplitudes of the four modulation frequencies which modulate the four respective beams are compared to generate corrective commands that cause the missile to fly down center line 60 . fig7 and 8 show the respective beam transmitter circuit and receiver circuits from fig6 . each of the four beams , 54a , 54b , 54c , and 54d is generated and detected in a like manner ; therefore only the signal processing along one beam path will be discussed in detail . for the polarization agile millimeter wave beam projection or transmitter of fig7 a modulator 62 and transmitter 64 are coupled in series to a power divider 66 which divides output power into two paths associated with each beam . power is coupled through phase shifter 68a to polarization transducer 69a for one path and is coupled directly to transducer 69a for the second path . an output from transducer 69a is then coupled to four - beam antenna 70 to provide the output beam 54a . similarly , phase shifters 68b - d and polarization transducers 69b - d provide coupling from divider 66 to antenna 70 to produce beams 54b - d . a phase and frequency control circuit 72 is coupled to modulator 62 and the phase shifters 68 , synchronizing power and phase shift . for the missile receiver 56 , antenna 58 receives the four beams as shown in fig8 and mixes the signals in mixer 74 with a local oscillator 76 output to produce an intermediate frequency that is amplified ( amplifier 78 ) and coupled to filter bank 80 to select the respective frequencies f 6 , f 7 , f 8 , and f 9 . the respective filter bank outputs from the filters are detected in detector bank 82 and the outputs , from the detectors are processed in error signal computer 84 to provide elevation and azimuth output signals to the missile . the local oscillator 76 frequency hops in synchronization with the transmitter to assume accurate mixing of received signals . the millimeter frequencies that are considered optimum for this invention are 94 ghz and 140 ghz . both of these frequency bands are in atmospheric windows where atmospheric attenuation reaches a minimum , and component and device work essential for implementing this invention has been done in both bands . the invention can be implemented in the 94 ghz band and take advantage of the more mature device and component technology and more favorable propagation conditions , or in the 140 ghz band where narrower beams can be formed to reduce multipath effects , but with the penalty of less mature and more lossy components and less favorable atmospheric transmission . although a particular embodiment and form of this invention has been illustrated , it is apparent that various modifications and embodiments of the invention may be made by those skilled in the art without departing from the scope and spirit of the foregoing disclosure . accordingly , the scope of the invention should be limited only by the claims appended hereto .