SUMMARY

Communication satellites transmit (i.e., broadcast) to earth a number of commercial radio-frequency (RF) electrical signals such as cell-phone signals, voice signals and data signals other than cell-phone signals, radio signals, and television signals.

Typically, a communication satellite is configured to broadcast such commercial RF signals over a wide area of the earth's surface so that a terrestrial (e.g., ground-based, near-ground-based) device or system configured to receive one or more of such signals can do so regardless of where in the area the device or system is located. Examples of such terrestrial devices and systems include cell-phone systems, smart phones, pagers, radios, and televisions.

Unfortunately, it can be difficult to impossible for a terrestrial device or system to receive such RF signals in all locations of the satellite's broadcast area. For example, a device can be in a “coverage hole,” which is a location, such as a building, under trees, or a tunnel, that does not have an unobstructed line of sight to the satellite.

Furthermore, even if a terrestrial device or system is in an unobstructed line-of-sight location in which it can receive an RF signal from a communication satellite, the size and expense of the components required to receive and amplify the signal may render the components impractical for use with the device or system. For example, even a smaller satellite-receive antenna (e.g., a satellite dish) configured for receiving satellite signals in the Ku band (12 GHz-18 GHz) can have a diameter of about 43 centimeters (cm) (about 18 inches). Although often suitable for receiving satellite television signals, an antenna of this size is typically too large, expensive, and cumbersome for a device such as a smartphone or even a car radio. Furthermore, for mobile devices such as a smart phone or a car radio, the satellite-receive antenna typically would need to be mounted on a moveable platform that includes control circuitry for maintaining a suitable orientation of the antenna relative to the satellite.

To allow a terrestrial device or system located in a “coverage hole,” or for which a satellite-receive antenna is impractical, to receive RF satellite signals, engineers have developed reception-and-retransmission systems for receiving signals from communication satellites and for retransmitting (i.e., rebroadcasting) these received signals in a form that renders the retransmitted signals receivable both by terrestrial devices and systems located in satellite-coverage holes and by terrestrial devices and systems without satellite dishes. For example, such a reception-and-retransmission system can retransmit the satellite signal in a different direction than the direction of propagation of the satellite signal, can increase the power and signal-to-noise ratio (SNR) of the retransmitted signal relative to the received satellite signal, and can re-encode and re-modulate the retransmitted signal according to coding and modulation techniques that are more suitable for a terrestrial device or system to decode and demodulate.

FIG. 1is a diagram of a satellite-communication system10, which includes a satellite12and a satellite-signal receiver and retransmitter14.

The satellite12can be a conventional communication satellite that transmits to earth one or more RF communication signals in one or more of the defined satellite-frequency bands, such as the L-Band (1 GHz-2 GHz), C-Band (4 GHz-8 GHz), Ku-Band (12 GHz-18 GHz), and Ka-Band (26.5 GHz-40.0 GHz). Such RF satellite signals typically carry commercial data such as voice data, radio-broadcast data, television-broadcast data, and other data (e.g., texts, emails, and data downloads and uploads from/to the world-wide web).

The satellite-signal receiver and retransmitter14includes a satellite-signal-receive antenna16, an RF-signal input cable18, a terrestrial signal repeater20, an RF-signal output cable22, and a retransmission antenna24, which cooperate to receive, to condition, and to retransmit the RF satellite signals from the satellite12in a form that is more suitable for reception by a terrestrial device or system. For example, the system14can be configured to retransmit the RF satellite signals at a higher power and at a higher SNR, and in one or more different directions, as compared to the RF satellite signals that the system receives from the satellite12.

The satellite-signal-receive antenna16can be a conventional satellite antenna such as a satellite dish, and can be configured to “excite” RF signals within the one or more frequency bands that the antenna is configured to receive. For example, the antenna16can be configured to have resonant (e.g., higher-gain) modes at frequencies that are approximately at the centers, or are otherwise within, the frequency bands of the RF signals that the antenna is configured to receive. That is, the antenna16can be configured to emphasize the RF signals that it is configured to receive, and to de-emphasize other signals. Such emphasis acts to amplify, and to pass on to the repeater20, the RF signals that the receiver-and-retransmitter14is configured to receive, and to filter out, and to block from the repeater, out-of-band signals and noise.

The antenna16can also include, or be coupled to, optional receiver circuitry26, which is configured to transcode one or more of the received RF satellite signals. That is, the receiver circuitry26is configured to convert the encoding of a received satellite signal from one form or algorithm to another form or algorithm, typically without a need to perform separate and distinct decoding and re-encoding steps. Said another way, the receiver circuitry26is configured to convert the encoding of a received satellite signal directly from one code to another code. The code to which the receiver circuitry26converts the RF signal may be more suitable for decoding by a terrestrial device or system configured to receive the RF signal. Similarly, the receiver circuitry26can be configured to convert the RF signal from one form of modulation to another form of modulation. Furthermore, the receiver circuitry26can be configured to emphasize and filter the received RF satellite signals, and the emphasizing and filtering that receiver circuitry is configured to perform can be instead of, or in addition to, the emphasizing and filtering performed by the antenna16.

The RF-signal input cable18is configured to couple, to the repeater20, the band-excited (and possibly transcoded or transmodulated) RF satellite signals from the antenna16. For example, the cable18can be a coaxial cable having a characteristic impedance of 50 Ohms (Ω), and, for maximum power transfer, the output port of the antenna16(or receiver circuitry26if present) and the input port of the repeater20can each be configured to present an impedance of 50Ω to the cable.

The repeater20includes a conventional amplifier circuit, such as a conventional power amplifier28, which is configured to amplify the RF satellite signal that the repeater receives from the antenna16(and receiver circuitry26if present) via the cable18.

The RF-signal output cable22is configured to couple, to the retransmission antenna24, the amplified RF satellite signal from the antenna repeater20. For example, like the input cable18, the output cable22can be a coaxial cable having a characteristic impedance of 50 Ohms (Ω), and, for maximum power transfer, the output port of the repeater20and the input port of the retransmission antenna24can each be configured to present an impedance of 50Ω to the output cable.

And the retransmission antenna24is configured to retransmit the amplified RF signal from the repeater20and the output cable22with a power, an SNR, and one or more directions that render the retransmitted signal more suitable for reception by a terrestrial device or system than the satellite signal from the satellite12. The power and SNR of the retransmitted RF signal can be sufficient for a terrestrial device or system to receive the retransmitted RF signal without the need for a satellite dish. For example, a smart phone or a car radio can be configured to receive the retransmitted RF signal with antennas that are of a standard size for a smart phone and a car radio, respectively. Furthermore, a direction of the retransmitted RF signal can be suitable for reception by a terrestrial device or system that is in a coverage hole (e.g., tunnel, shadow of a tree, building, or other object) of the satellite12, and that, therefore, would be unable to receive an RF signal directly from the satellite. Moreover, the retransmission antenna24can be any suitable type of antenna such as a dipole, reflector, or multi-element antenna.

Unfortunately, it can be difficult to find a suitable terrestrial location for the satellite-signal receiver and retransmitter14.

Because the power of the received RF signals that the antenna16and receiver circuitry26provide to the input cable18is relatively small, and because the signal loss per unit distance (e.g., decibels (dB) per meter (m)) of the input cable is relatively high, a designer of the receiver and retransmitter14typically limits the length of the input cable to no more than a few meters.

For similar reasons, a designer of the receiver and retransmitter14typically limits the length of the output cable22to no more than a few meters.

Therefore, the satellite-signal receive antenna16(and receiver circuitry26if present), the repeater20, and the retransmit antenna24typically are constrained to be in the same location.

But unfortunately, a location suitable for the satellite-signal receive antenna16may be unsuitable for the retransmit antenna24, and vice-versa. Suitable locations for the receive antenna16typically lie along respective unobstructed line-of-sight paths with the satellite12, and include relatively high places like hills, mountains, and the tops of buildings. In contrast, although a suitable location for the retransmit antenna24need not lie along an unobstructed line-of-sight path with the satellite12, such a location typically lies relatively close to the ground (e.g., no more than 35 m above the ground) and in a populated area where terrestrial devices and systems configured to receive RF signals broadcast by the satellite12are more likely to be found.

Consequently, locations suitable for the receiver and retransmitter14are limited in number because such a location typically must have all of the features (e.g., unobstructed line-of-sign path, low to ground, and in a populated area) that are suitable for both the satellite-signal receive antenna16and the retransmit antenna24.

Furthermore, even if the receiver and retransmitter14is located in a suitable place, the relatively close spacing between the satellite-signal receive antenna16and the retransmit antenna24can cause other problems. For example, in addition to receiving the signals transmitted by the satellite12, the receive antenna16can receive unwanted feedback of retransmitted signals from the retransmit antenna24. Although the repeater20can include circuitry to reduce or eliminate the effect of such unwanted feedback, such feedback-cancelling circuitry is typically relatively complex and expensive, and adds extra weight and heat generation to the repeater20. Furthermore, the receive antenna16and the retransmit antenna24may become electrically coupled to one another, or may otherwise interfere with one another, such that one of the antennas may alter one or more characteristics (e.g., effective aperture) of the other antenna as compared to the characteristics that the other antenna would have in the absence of such coupling/interference. Because such antenna coupling/interference depends on a specific placement and orientation of the receive antenna16relative to the retransmit antenna24, and because such placement and orientation are typically unknown until the receiver and retransmitter circuit14is installed, it is difficult to design and to configure the repeater20to minimize the effects of such antenna coupling/interference.

Therefore, a need has arisen for a receiver and transmitter configured to provide one or more of the following technical improvements: allowing independent placement of the satellite-signal receive antenna and the retransmit antenna in respective suitable locations, and reducing, or eliminating, one or more of unwanted feedback, unwanted coupling, and unwanted interference between the receive and retransmit antennas.

An embodiment of a signal repeater that solves at least one of the aforementioned problems includes a master unit and a remote unit that are optically coupled to one another. The master unit includes master-unit circuitry configured to receive an input electrical signal from a satellite-signal receive antenna, and to convert the input electrical signal into an optical signal. And the remote unit includes remote-unit circuitry configured to convert the optical signal into an intermediate electrical signal, to amplify the intermediate electrical signal into an output electrical signal, and to couple the output electrical signal to a retransmission antenna. An optical channel, such as an optical fiber, is coupled between the master and remote units and is configured to carry the optical signal from the master unit to the remote unit.

Because an optical channel, such as an optical fiber, attenuates an optical signal significantly less per unit of distance than a coaxial cable attenuates an electrical signal, a signal repeater with optically coupled master and remote units allows a satellite-signal receive antenna to be located at a significant distance (e.g., up to ˜20 kilometers (˜12 miles) from a retransmit antenna.

And locating the satellite-signal receive antenna far from the retransmit antenna allows both antennas to be in respective suitable locations, and reduces or eliminates electromagnetic feedback, coupling, and interference between the antennas.

