US4725844A — Fiber optical discrete phase modulation system

Claim 1

Independent Claim 139 words

A phased-array antenna feed system, comprising: an optical carrier signal source; a radio-frequency (rf) subcarrier signal source coupled to amplitude-modulate the optical carrier signal; data modulator means, including switch-selectable optical delay paths for controlling the phase of the optical carrier signal by selected increments of subcarrier phase angle, to produce a data-modulated signal; star coupler means, for splitting the data-modulated signal into an array of separate signals of substantially equal power; phase-shifting means, for applying selected phase shifts to the separate signals, to effect beam steering in a phased-array antenna, wherein the phase-shifting means includes a plurality of phase shifters, each having multiple optical signal paths, multiple electro-optical switching means, and switching logic means for selecting a particular phase delay; and detector means for converting the data-modulated and phase-shifted optical signals to rf signals for application to the antenna.

Claim 2

Dependent Claim 139 words

A phased-array antenna feed system, comprising: an optical carrier signal source; a radio-frequency (rf) subcarrier signal source coupled to amplitude-modulate the optical carrier signal; data modulator means, including switch-selectable optical delay paths for controlling the phase of the optical carrier signal by selected increments of subcarrier phase angle, to produce a data-modulated signal; star coupler means, for splitting the data-modulated signal into an array of separate signals of substantially equal power; phase-shifting means, for applying selected phase shifts to the separate signals, to effect beam steering in a phased-array antenna, wherein the phase-shifting means includes a plurality of phase shifters, each having multiple optical signal paths, multiple electro-optical switching means, and switching logic means for selecting a particular phase delay; and detector means for converting the data-modulated and phase-shifted optical signals to rf signals for application to the antenna.

Claim 3

Dependent Claim 112 words

A phased-array antenna feed system as set forth in claim 1, wherein: the star coupler means includes a first star coupler for splitting the data-modulated signal into a plurality of beams arrayed in a single column, and a plurality of additional star couplers for splitting each of the beams arrayed in a column into a plurality of beams arrayed a row; and the phase-shifting means includes a first stack of phase shifters for application of selected phase shifts to the beams arrayed in a column, to effect vertical beam control, and a second stack of phase shifters for applying selected phase shifts to selected columns of beams, to effect horizontal beam control.

Claim 4

Dependent Claim 46 words

A phased-array antenna feed system as set forth in claim 1, wherein: the star coupler means produces and two-dimensional array of beams; and the phase-shifting means includes multiple phase shifters for applying selected phase shifts to corresponding beams in the array, to effect angular beam control.

Claim 5

Dependent Claim 157 words

A phased-array antenna feed system for use as a receiver, said system comprising: an optical carrier signal source; a radio-frequency (rf) subcarrier signal source coupled to amplitude-modulate the optical carrier signal; star coupler means, for splitting the resulting signal into an array of separate signals of substantially equal power; phase-shifting means, for applying selected phase shifts to the separate signals, to effect beam steering in a phased-array antenna, wherein the phase-shifting means includes a plurality of phase shifters, each having multiple optical signal paths, multiple electro-optical switching means, and switching logic means for selecting a particular phase delay; detector means for converting the data-modulated and phase-shifted optical signals to rf signals; mixing means for combining these rf signals with other rf signals received from corresponding antenna elements, to obtain intermediate-frequency signals; signal summation means, for combining the elemental intermediate-frequency signals into one intermediate-frequency signal; and data demodulation means, for producing data signal from the single intermediate-frequency signal.

Claim 6

Dependent Claim 157 words

A phased-array antenna feed system for use as a receiver, said system comprising: an optical carrier signal source; a radio-frequency (rf) subcarrier signal source coupled to amplitude-modulate the optical carrier signal; star coupler means, for splitting the resulting signal into an array of separate signals of substantially equal power; phase-shifting means, for applying selected phase shifts to the separate signals, to effect beam steering in a phased-array antenna, wherein the phase-shifting means includes a plurality of phase shifters, each having multiple optical signal paths, multiple electro-optical switching means, and switching logic means for selecting a particular phase delay; detector means for converting the data-modulated and phase-shifted optical signals to rf signals; mixing means for combining these rf signals with other rf signals received from corresponding antenna elements, to obtain intermediate-frequency signals; signal summation means, for combining the elemental intermediate-frequency signals into one intermediate-frequency signal; and data demodulation means, for producing data signal from the single intermediate-frequency signal.

Claim 7

Dependent Claim 135 words

A phased-array antenna feed system for use as a receiver, said system comprising: an array of optical signal sources, each of which is directly modulated by amplified rf signals received from an array of antenna elements; light-conducting means for connecting the optical signal sources to a processing site; a plurality of phase-shifters connected to the light-conducting means, each phase shifter having multiple optical delay paths, multiple opto-electrical switches and switching logic means for selecting a phase delay for each elemental optical signal; a plurality of detectors, for converting the elemental optical signals into radio-frequency (rf) signals; signal summation means, for electrically combining the rf signals and producing a single rf output signal indicative of data received from a selected antenna direction; and data demodulation means, for deriving data signals from the single rf output signal.

Claim 8

Dependent Claim 135 words

A phased-array antenna feed system for use as a receiver, said system comprising: an array of optical signal sources, each of which is directly modulated by amplified rf signals received from an array of antenna elements; light-conducting means for connecting the optical signal sources to a processing site; a plurality of phase-shifters connected to the light-conducting means, each phase shifter having multiple optical delay paths, multiple opto-electrical switches and switching logic means for selecting a phase delay for each elemental optical signal; a plurality of detectors, for converting the elemental optical signals into radio-frequency (rf) signals; signal summation means, for electrically combining the rf signals and producing a single rf output signal indicative of data received from a selected antenna direction; and data demodulation means, for deriving data signals from the single rf output signal.

Claim 9

Independent Claim 111 words

A method of angularly deflecting a phased-array antenna beam, comprising the steps of: amplitude-modulating an optical carrier signal with a radio-frequency subcarrier signal; applying selected phase delays to the optical carrier signal, equivalent to phase delay angles of the rf subcarrier signal, to modulate the carrier signal with digital data; splitting the data-modulated carrier signal into an array of elemental optical signals; applying selected phase delays to the elemental optical signals to effect angular steering of the antenna beam; amplitude-demodulating the elemental optical signals in a plurality of detectors, to obtain a set of data-modulated, phase-shifted elemental rf signals; and applying these rf signals to antenna elements in a phased-array antenna.

Claim 10

Independent Claim 111 words

A method of angularly deflecting a phased-array antenna beam, comprising the steps of: amplitude-modulating an optical carrier signal with a radio-frequency subcarrier signal; applying selected phase delays to the optical carrier signal, equivalent to phase delay angles of the rf subcarrier signal, to modulate the carrier signal with digital data; splitting the data-modulated carrier signal into an array of elemental optical signals; applying selected phase delays to the elemental optical signals to effect angular steering of the antenna beam; amplitude-demodulating the elemental optical signals in a plurality of detectors, to obtain a set of data-modulated, phase-shifted elemental rf signals; and applying these rf signals to antenna elements in a phased-array antenna.

Claim 11

Dependent Claim 54 words

A method as set forth in claim 6, wherein the step of splitting the carrier signal includes: passing the carrier signal through a first star coupler to produce a linear array of signals; and passing each of the array signal through an additional star coupler to produce a two-dimensional array of elemental optical signals.

Claim 12

Dependent Claim 51 words

A method as set forth in claim 6, wherein the steps for applying selected phase delays include: introducing the carrier signal into a phase-delay network having multiple alternate paths, each having a different phase delay; and switching the phase-delay network by means of opto-electrical switches, to provide the desired phases delay.

Claim 13

Independent Claim 111 words

A method of angularly deflecting a phased-array receiving antenna beam, comprising the steps of: amplitude-modulating an optical carrier signal with a radio-frequency subcarrier signal; splitting the amplitude-modulated carrier signal into an array elemental optical signals; applying selected phase delays to the elemental optical signals to effect angular steering of the antenna beam; amplitude-demodulating the elemental optical signals in a plurality of detectors to obtain a set of phase-shifted elemental rf signals; and mixing these elemental rf signal with corresponding elemental rf siynal received from antenna elements, to obtain elemental intermediate-frequency signals; combining the elemental intermediate-frequency signals to produce a single intermediate-frequency signal; and demodulating the intermediate-frequency signal to obtain data signals.

Claim 14

Independent Claim 111 words

A method of angularly deflecting a phased-array receiving antenna beam, comprising the steps of: amplitude-modulating an optical carrier signal with a radio-frequency subcarrier signal; splitting the amplitude-modulated carrier signal into an array elemental optical signals; applying selected phase delays to the elemental optical signals to effect angular steering of the antenna beam; amplitude-demodulating the elemental optical signals in a plurality of detectors to obtain a set of phase-shifted elemental rf signals; and mixing these elemental rf signal with corresponding elemental rf siynal received from antenna elements, to obtain elemental intermediate-frequency signals; combining the elemental intermediate-frequency signals to produce a single intermediate-frequency signal; and demodulating the intermediate-frequency signal to obtain data signals.

Claim 15

Independent Claim 87 words

A method of angularly deflecting a phased-array receiving antenna beam, comprising the steps of: amplitude-modulating a plurality of optical signal sources with elemental radio-frequency (rf) subcarrier signals derived from correponding receiving antenna elements, to produce a plurality of elemental optical carrier signals; applying selected phase delays to the elemental carrier signals, to effect antenna beam steering; amplitude-demodulating the elemental carrier signals, to produce elemental rf signals that have been phase-shifted for antenna beam steering; and combining by summation the elemental rf signals into a single rf signal.

Claim 16

Independent Claim 87 words

A method of angularly deflecting a phased-array receiving antenna beam, comprising the steps of: amplitude-modulating a plurality of optical signal sources with elemental radio-frequency (rf) subcarrier signals derived from correponding receiving antenna elements, to produce a plurality of elemental optical carrier signals; applying selected phase delays to the elemental carrier signals, to effect antenna beam steering; amplitude-demodulating the elemental carrier signals, to produce elemental rf signals that have been phase-shifted for antenna beam steering; and combining by summation the elemental rf signals into a single rf signal.

Claim 17

Dependent Claim 163 words

Apparatus for applying selected discrete phase shifts to an optical carrier signal, said apparatus comprising: an optical input port and an optical output port; multiple optical waveguides, defining multiple optical signal paths, each having selected phase delays corresponding to phase delays with respect to a subcarrier signal modulated onto the optical carrier signal; multiple optical switching means, including electro-optical switches providing switching of an optical signal from one path to another upon the application of an electrical switching signal connecting the signal paths between the input ports and the output ports; and switching logic means, having input terminals for receiving phase delay selection signals, and output terminals connected to the optical switching means, to actuate the switching means and select appropriate phase delays corresponding to the phase delay selection signals; and wherein the apparatus is used for quadrature phase-shift keying (QPSK) phase modulation, and the optical waveguides provide phase delays of 0, 90, 180, or 270 degrees with respect to the subcarrier signal.

Claim 18

Dependent Claim 163 words

Apparatus for applying selected discrete phase shifts to an optical carrier signal, said apparatus comprising: an optical input port and an optical output port; multiple optical waveguides, defining multiple optical signal paths, each having selected phase delays corresponding to phase delays with respect to a subcarrier signal modulated onto the optical carrier signal; multiple optical switching means, including electro-optical switches providing switching of an optical signal from one path to another upon the application of an electrical switching signal connecting the signal paths between the input ports and the output ports; and switching logic means, having input terminals for receiving phase delay selection signals, and output terminals connected to the optical switching means, to actuate the switching means and select appropriate phase delays corresponding to the phase delay selection signals; and wherein the apparatus is used for quadrature phase-shift keying (QPSK) phase modulation, and the optical waveguides provide phase delays of 0, 90, 180, or 270 degrees with respect to the subcarrier signal.

Claim 19

Dependent Claim 67 words

Apparatus as set forth in claim 11, wherein: there are four alternate waveguides defining the optical paths, and four sets of electo-optical switches for selecting one of the waveguides at any time; and the switching logic means includes means for generating a control signal on one of four output terminals, connected to one of the four sets of electro-optical switches, in response to phase delay switching signals.

Claim 20

Dependent Claim 80 words

Apparatus as set forth in claim 11, wherein: there are two separate waveguides defining the multiple optical paths, one with a phase delay of 90 degrees and the other with a phase delay of 180 degrees; the electro-optical switches are switchable to interpose one, both, or none of the two waveguides in the optical light path through the device; and the switching logic means includes means for generating control signals for selecting either one or both of the two waveguides.

Claim 21

Independent Claim 129 words

A method for applying selected phase delays to an optical carrier signal that has been amplitude-modulated with a radio-frequency (rf) subcarrier signal, the method comprising the steps of: inputting the optical carrier signal to a phase delay network having a plurality of alternate optical waveguide paths, each providing a different delay of 0, 90, 180, or 270 degrees with respect to the phase of the rf subcarrier signal; applying phase delay selection signals to switching logic means; generating in the switching logic means a set of corresponding control signals; and applying the control signals to electro-optical switches to control the flow of the optical carrier signal through the phase delay network in such a manner as to achieve the desired phase delay for quadrature phase-shift keying (QPSK) phase modulation.

Claim 22

Independent Claim 129 words

A method for applying selected phase delays to an optical carrier signal that has been amplitude-modulated with a radio-frequency (rf) subcarrier signal, the method comprising the steps of: inputting the optical carrier signal to a phase delay network having a plurality of alternate optical waveguide paths, each providing a different delay of 0, 90, 180, or 270 degrees with respect to the phase of the rf subcarrier signal; applying phase delay selection signals to switching logic means; generating in the switching logic means a set of corresponding control signals; and applying the control signals to electro-optical switches to control the flow of the optical carrier signal through the phase delay network in such a manner as to achieve the desired phase delay for quadrature phase-shift keying (QPSK) phase modulation.

Claim 23

Dependent Claim 37 words

A method as set forth in claim 14, wherein: the step of generating control signals includes generating a control signal on one of four output terminals, for connection to the electro-optical switches, in response to data signals.

Claim 24

Dependent Claim 73 words

A method as set forth in claim 14, wherein: there are two separate waveguides making up the alternate optical waveguide paths, one with a phase delay of 90 degrees and the other with a phase delay of 180 degrees; and the step of applying the control signals is effective to switch the electro-optical switches to interpose one, both, or none of the two waveguides paths in the optical light path through the device.

Claim 25

Independent Claim 119 words

A method for applying selected phase delays to an optical carrier signal that has been modulated with a radio-frequency (rf) subcarrier signal, the method comprising the steps of: inputting the optical carrier signal to a phase delay network having a plurality of alternate optical waveguide paths, each providing a different delay to the phase of the rf subcarrier signal; applying phase delay selection signals to switching logic means; generating in the switching logic means a set of corresponding control signals; and applying the control signals to electro-optical switches to control the flow of the optical carrier signal through the phase delay network in such a manner as to achieve the desired phase delay for phase-shift keying (PSK) phase modulation.

Claim 26

Independent Claim 119 words

A method for applying selected phase delays to an optical carrier signal that has been modulated with a radio-frequency (rf) subcarrier signal, the method comprising the steps of: inputting the optical carrier signal to a phase delay network having a plurality of alternate optical waveguide paths, each providing a different delay to the phase of the rf subcarrier signal; applying phase delay selection signals to switching logic means; generating in the switching logic means a set of corresponding control signals; and applying the control signals to electro-optical switches to control the flow of the optical carrier signal through the phase delay network in such a manner as to achieve the desired phase delay for phase-shift keying (PSK) phase modulation.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-02-15	1991-08-17	1992-02-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-02-15	1995-08-17	1996-02-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-02-15	1999-08-17	2000-02-16	$7700.00	Window Closed / Lapsed

Fiber optical discrete phase modulation system

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