US 8,094,081 B1Granted

Dual band radio frequency (RF) and optical communications antenna and terminal design methodology and implementation

AssigneeThe Johns Hopkins University

InventorsJonathan R. Bruzzi, Bradley G. Boone

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Abstract

A dual-band antenna is provided that combines two normally disparate communications modes into a single compact aperture minimizing overall mass and volume, while maintaining high performance efficiency and reciprocity of each individual mode. The antenna is compatible with both optical (near-IR/visible) and RF (microwave/millimeter-wave) transceiver subsystems for high bandwidth communications, applicable primarily to long- to extremely long-range (space-to-ground) link distances. The optical link provides high bandwidth while the RF provides a lower data-rate weather backup, accommodation for traditional navigation techniques, and assistance in cueing the extremely tight optical beam by matching the RF beamwidth to an optical fine-steering mechanism field-of-regard. The configuration is built around a near-diffraction-limited high performance primary mirror shared by both a direct-fed RF antenna design and a Cassegrain optical telescope. Material properties are exploited to combine the optical secondary mirror with the RF feed structure, providing a collimated optical beam interface at the antenna vertex.

Claims21

Dependent claims

A common aperture dual-band antenna for optimally transmitting and receiving microwave and optical energy for high data-rate communications, the dual-band antenna comprising:

(A) a shared portion comprising a primary reflector configured for focusing and reflecting said microwave and optical energy;
(B) an optical portion in a largely Cassegrain configuration comprising:
(i) an optical transceiver configured for high data rate transmission and laser beam pointing, acquisition and tracking, the optical transceiver further comprising:
a laser source, an optical detector, a tracking detector array and a beam-steerer;
(ii) an optical beam interface positioned substantially at a vertex of said dual-band antenna to facilitate integration the dual-band antenna with said optical transceiver;
(iii) a dichroic secondary reflector configured for optical reflection and RF transmission;
(iv) a dichroic vertex window configured for optical transmission and RF reflection;
(v) an optical baffle positioned substantially between the primary reflector and the secondary reflector configured for shielding unwanted stray optical wave energy;
(vi) a divergent lens positioned substantially at the vertex of the primary reflector and configured for transferring a collimated beam to the secondary reflector and for transferring an converging beam from the secondary to a collimated beam behind the vertex of the primary reflector;
(C) a microwave portion in a direct fed configuration comprising:
a microwave feed assembly further comprising:
(i) an RF feed horn located on a central axis of the apparatus to which all portions of said apparatus are co-aligned proximal to the focus of the primary reflector, said RF feed configured for optimally illuminating the primary reflector with microwave energy for transmission to a remote terminal and for receiving microwave energy from said remote terminal reflected from the primary reflector and focused to the RF feed horn;
(ii) a circular polarizer interface for circularly polarizing RF energy transmitted from said RF feed horn to allow the arbitrary orientation of the terminal around its pointing vector while communicating with said remote terminal.

10 more elements

A communications terminal, comprising:

(1) a common aperture dual-band antenna for optimally transmitting and receiving microwave and optical energy for high data-rate communications, the dual-band antenna comprising:
(A) a shared portion comprising a primary reflector configured for focusing and reflecting said microwave and optical energy;
(B) an optical portion in a largely Cassegrain configuration comprising:
(i) an optical transceiver configured for high data rate transmission and laser beam pointing, acquisition and tracking, the optical transceiver further comprising:
a laser source, an optical detector, a tracking detector array and a beam-steerer;
(ii) an optical beam interface positioned substantially at a vertex of said dual-band antenna to facilitate integration the dual-band antenna with said optical transceiver;
(iii) a dichroic secondary reflector configured for optical reflection and RF transmission;
(iv) a dichroic vertex window configured for optical transmission and RF reflection;
(v) an optical baffle positioned substantially between the primary reflector and the secondary reflector configured for shielding unwanted stray optical wave energy;
(vi) a divergent lens positioned substantially at the vertex of the primary reflector and configured for transferring a collimated beam to the secondary reflector and for transferring an converging beam from the secondary to a collimated beam behind the vertex of the primary reflector;
(C) a microwave portion
(i) an RF feed horn located on a central axis of the apparatus to which all portions are co-aligned proximal to the focus of the primary reflector, said RF feed configured for optimally illuminating the primary reflector with microwave energy for transmission to a remote terminal and for receiving microwave energy from said remote terminal reflected from the primary reflector and focused to the RF feed horn;
(ii) a circular polarizer interface for circularly polarizing RF energy transmitted from said RF feed horn to allow the arbitrary orientation of the terminal around its pointing vector while communicating with said remote terminal;
and
(2) transceiver logic configured for modulating a transmitted laser beam from said laser source and further configured for demodulating a received laser beam;
(3) an encoder and decoder for converting digital data to a protected modulation waveform for authentication;
and
(4) forward error correction code to compensate for implementation losses, atmospheric propagation losses, and pointing and tracking errors.

15 more elements

A multi-channel communications terminal comprising:

a common aperture dual-band antenna for optimally transmitting and receiving microwave and optical energy for high data-rate communications, the dual-band antenna further comprising:
(A) a shared portion comprising a primary reflector configured for focusing and reflecting said microwave and optical energy;
(B) an optical portion in a largely Cassegrain configuration comprising:
(i) a multi-channel optical transceiver/tracker further comprising:
a multiple receiver detector array, and a multiply sub-windowed CMOS tracking array, said multi-channel optical transceiver/tracker optical transceiver configured for high data rate transmission and laser beam pointing, acquisition and tracking;
(ii) an optical beam interface positioned substantially at a vertex of said dual-band antenna to facilitate integration the dual-band antenna with said optical transceiver;
(iii) a dichroic secondary reflector configured for optical reflection and RF transmission;
(iv) a dichroic vertex window configured for optical transmission and RF reflection;
(v) an optical baffle positioned substantially between the primary reflector and the secondary reflector configured for shielding unwanted stray optical wave energy;
(v) a divergent lens positioned substantially at the vertex of the primary reflector and configured for transferring a collimated beam to the secondary reflector and for transferring an converging beam from the secondary to a collimated beam behind the vertex of the primary reflector;
(C) a microwave portion
(i) an RF feed horn located on a central axis of the apparatus to which all portions of said apparatus are co-aligned proximal to the focus of the primary reflector, said RF feed configured for optimally illuminating the primary reflector with microwave energy for transmission to a remote terminal and for receiving microwave energy from said remote terminal reflected from the primary reflector and focused to the RF feed horn;
and
(ii) a circular polarizer interface for circularly polarizing RF energy transmitted from said RF feed horn to allow the arbitrary orientation of the terminal around its pointing vector while communicating with said remote terminal.

11 more elements

Dependencies are inferred from the claim text.