Radio based automatic level control for linear radio calibration

A linear radio and a method for performing automatic level control are provided. A demultiplexer, within the linear radio, receives multiplexed signals from an indoor unit via a cable connecting the indoor unit with the linear radio. The demultiplexer demultiplexes the multiplexed signals to produce a transmit signal of an intermediate frequency. A variable gain amplifier within the linear radio, receives the transmit signal and a signal from an operational amplifier and produces the transmit signal with a changed gain, which is provided to a coupler. The coupler provides the transmit signal with the changed gain to a mixer and a power detector simultaneously. The power detector produces a second signal, which is provided to the operational amplifier, thereby forming a closed automatic level control loop. In some embodiments, the demultiplexer produces a power control signal, which is provided to the operational amplifier as a second input.

FIELD OF THE INVENTION

The invention relates to an automatic level control circuit for maintaining a fixed power level for a linear radio. In particular, the invention relates to an automatic level control loop circuit, completely contained in a linear radio, for maintaining a fixed power level for a transmit signal provided to an upconverting mixer.

BACKGROUND

Signal loss occurs for signals transmitted across an RG-6 cable connecting an indoor unit with an outdoor unit. During installation, linear VSAT terminal installers may manually calibrate for signal loss between the indoor unit and the outdoor unit using separate handheld devices to measure the signal loss at an output of various components. Manual calibration may be a lengthy process, which may include introduction of human errors. After the manual calibration is completed, the manual calibration is to be repeated when any parameter related to transmit signal power between the indoor unit and the outdoor unit changes. An example of such a parameter includes, but is not limited to, a change in length of a cable connecting the indoor unit with the outdoor unit.

FIG. 1illustrates use of a previous method for automatic calibration of linear radio transmit signals.FIG. 1shows an indoor unit108connected to an outdoor linear radio112of an outdoor unit via a RG-6 cable124. Indoor unit108includes an automatic level control circuit104for controlling a power level of transmit signals sent from indoor unit108to outdoor linear radio112. Outdoor linear radio112includes a demultiplexer114, an upconverting mixer106, a coupler116, and a power detector102. InFIG. 1, indoor unit108may transmit multiple multiplexed signals to outdoor linear radio112via RG-6 cable124. Demultiplexer114receives and demultiplexes the multiple signals to produce a transmit signal118of an intermediate frequency, as well as other signals. Upconverting mixer106receives transmit signal118and a local oscillator signal120to produce a transmit signal at a final output frequency122. Coupler116simultaneously provides transmit signal122to power detector102and a Very Small Aperture Terminal (VSAT) antenna126, which transmits transmit signal122to a destination device via a satellite. Power detector102measures a power level of transmit signal122and provides power information to automatic level control circuit104via a digital communication link110.

Automatic level control circuit104, in indoor unit108, receives the power information as feedback, thereby causing automatic level control circuit104to control, based on the power information, a power level of transmit signals transmitted to outdoor linear radio112via RG-6 cable124connecting indoor unit106with outdoor linear radio112.

SUMMARY

In a first embodiment, a method is provided for performing radio based automatic level control for linear radio calibration. A demultiplexer of a linear radio receives multiplexed signals communicated via a cable connecting the linear radio with a second unit. The multiplexed signals are demultiplexed to produce a transmit signal of an intermediate frequency. A variable gain amplifier of the linear radio receives the transmit signal and a signal from an operational amplifier and produces the transmit signal with a changed gain. The transmit signal with the changed gain is provided to a coupler, which further provides the signal with the changed gain to a mixer and a power detector simultaneously, thereby forming a closed automatic level control loop.

In a second embodiment and outdoor linear radio is provided. The outdoor linear radio includes an automatic level control loop, which is completely included in the outdoor linear radio. The automatic level control loop receives a transmit signal of an intermediate frequency and produces a power controlled transmit signal. The automatic level control loop automatically adjust a gain of the transmit signal based on an amount of power detected in the power controlled transmit signal.

DETAILED DESCRIPTION

Overview

An outdoor linear radio is provided, which includes a complete automatic level control circuit within the outdoor linear radio. The automatic level control circuit receives a transmit signal of an intermediate frequency. A power detector measures a power level of the transmit signal and feeds back power information from the power detector to a variable gain amplifier, such that a power level of the transmit signal of the intermediate frequency is controlled based on the power information provided to the variable gain amplifier.

Various embodiments eliminate use of a digital communication link between the power detector and an indoor unit, thereby providing a less complicated, more reliable, and less expensive solution for performing power level control of transmit signals. Further, detecting power of the transmit signal of the intermediate frequency is less complicated than detecting power of a transmit signal of a final output frequency, including but not limited to, an output frequency in a Ka band. In addition, changes to parameters such as, for example, a cable length between the indoor unit and the outdoor linear radio, will not negatively affect power control of the transmit signal performed by the automatic level control circuit within the outdoor linear radio. Because manual calibration of power control becomes unnecessary, introduction of human errors during calibration is eliminated.

Exemplary Operating Environment

FIG. 2shows an exemplary operating environment200for various embodiments. Operating environment200includes an indoor unit202and an outdoor linear radio204of an outdoor unit. A cable124, which may be a RG-6 cable or other cable, may connect indoor unit202with outdoor linear radio204of an outdoor unit. Outdoor linear radio204may include a demultiplexer114, an automatic level control circuit loop208, and an upconverting mixer106. Automatic level control circuit loop208may include a variable gain amplifier216, a coupler218, a power detector220, and an operational amplifier222. Transmitted signals of a final output frequency122may be provided to an antenna126, including but not limited to a Very Small Aperture Terminal (VSAT) antenna.

Operation of indoor unit202and outdoor linear radio204will be explained with reference toFIG. 4. Indoor unit202may transmit multiple signals, which are received by demultiplexer114of outdoor linear radio302(act402). Demultiplexer114may demultiplex the received multiple signals to produce a transmit signal of an intermediate frequency118(act404). Variable gain amplifier216of automatic level control circuit loop208may receive transmit signal118and may adjust a power level of transmit signal118based on input from operational amplifier222(act406). Variable gain amplifier216may provide transmit signal118, with the adjusted power level, to coupler218(act408).

Coupler218may then simultaneously provide transmit signal118to power detector220(act414) and upconverting mixer106(act410). Upconverting mixer106may mix transmit signal118at the intermediate frequency with a local oscillator signal120to provide a transmit signal of a final output frequency (act412). In one embodiment, the final output frequency may be in a Ka band between 28 GHz to 30 GHz. In other embodiments, the final output frequency may be in a Ku band, an X band, a Z band, a C band, or another band.

Power detector220may detect an amount of power of transmit signal118and may output a signal indicating the amount of power to operational amplifier222(act416). Operational amplifier222may then output an amplified control signal, based on the signal indicating the amount of power, to variable gain amplifier216(act418), thereby completing the automatic level control circuit loop. Variable gain amplifier206may adjust a power level of transmit signal118based on the amplified control signal provided by operational amplifier222.

Variation of Above Embodiment

FIG. 3shows a variation of the embodiment ofFIG. 2. A difference betweenFIG. 2andFIG. 3is a power control signal304produced by demultiplexer114of outdoor linear radio302after demultiplexing the multiple signals received from indoor unit202. Power control signal304may be provided to operational amplifier308of automatic level control circuit loop306. An amplified control signal output by operational amplifier308is based on the signal representing the amount of power detected by power detector220and power control signal304. As a result, indoor unit202may transmit power control signal304within the transmitted multiple signals provided to outdoor linear radio302in order to adjust a power level of transmit signal118output from variable gain amplifier216when weather conditions change.

Operation of indoor unit202and outdoor linear radio302will be explained with reference toFIGS. 5 and 3. Indoor unit202may transmit multiple signals, which are received by demultiplexer114of outdoor linear radio302(act502). Demultiplexer114may demultiplex the received multiple signals to produce transmit signal of an intermediate frequency118and power control signal304(act504). Variable gain amplifier216of automatic level control circuit loop306may receive transmit signal118and may adjust a power level of transmit signal118based on input from operational amplifier222(act506). Variable gain amplifier216may provide transmit signal118, with the adjusted power level, to coupler218(act508).

Coupler218may then simultaneously provide transmit signal118to power detector220(act514) and upconverting mixer106(act510). Upconverting mixer106may mix transmit signal118at the intermediate frequency with a local oscillator signal120to provide a transmit signal of a final output frequency (act512). In one embodiment, the final output frequency may be in a Ka band between 28 GHz to 30 GHz. In other embodiments, the final output frequency may be in a Ku band, an X band, a Z band, a C band, or another band.

Power detector220may detect an amount of power of transmit signal118and may output a signal indicating the amount of power to operational amplifier308(act516). Meanwhile, power control signal304may be provided to operational amplifier308from demultiplexer114(act518). Operational amplifier308may then output an amplified control signal, based on the signal indicating the amount of power from power detector220and power control signal304, to variable gain amplifier216(act520), thereby completing the automatic level control circuit loop. Variable gain amplifier216may adjust a power level of transmit signal118based on the amplified control signal provided by operational amplifier308.

CONCLUSION

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms for implementing the claims.

Although the above descriptions may contain specific details, they should not be construed as limiting the claims in any way. Other configurations of the described embodiments are part of the scope of this disclosure. Further, implementations consistent with the subject matter of this disclosure may have more or fewer acts than as described, or may implement acts in a different order than as shown. Accordingly, the appended claims and their legal equivalents should only define the invention, rather than any specific examples given.