Module for combining signals having different frequencies

Certain features relate to a telecommunications system with a modular frequency combiner combining multiple received signals at different frequency bands without using frequency-dependent multiplexers. The frequency combiner can include adjustable tuning elements for adjusting various signal-processing parameters of the frequency combiner while the frequency combiner is in the telecommunications system. For example, adjustable tuning elements can adjust the phases of phase shifters of each RF path so that the RF paths are matched for combining the received signals and outputting them through an output port. The adjustable tuning elements can also adjust the electrical length or physical length of the transmission lines that carry the received signals. The adjustable tuning elements can be adjusted manually or automatically while the frequency combiner is deployed in the field in the telecommunications system.

TECHNICAL FIELD

The disclosure relates generally to telecommunications and, more particularly (although not necessarily exclusively), to a frequency combiner for adjusting signal-processing parameters and combining signals of multiple frequency bands.

BACKGROUND

In a telecommunications system, such as a distributed antenna system (DAS) or a repeater installation, multiple frequency bands can be wirelessly received via one or more antennas. A DAS or a repeater installation can be used to extend wireless coverage in an area. For example, a repeater can receive multiple frequency bands from a base station wirelessly from one or more donor antennas. After amplification to a desired output power, individual transmit and receive paths can be combined using a frequency combiner. The combined signal can be output via one or more RF ports to serve a coverage area. But, a frequency dependent frequency combiner can involve insertion loss and lack flexibility when a frequency band unsupported by the frequency combiner is used.

In a telecommunications system such as a DAS, a repeater, or a small cell, one or more head-end units can receive downlink signals on multiple frequency bands from one or more base stations. The head-end unit can distribute the downlink signals in analog or digital format to one or more remote units. The individual transmit paths can be combined in a multiplexer in a remote unit and output from one or more RF ports to serve a coverage area. But, a frequency dependent multiplexer can lack flexibility when a frequency band unsupported by the multiplexer is used.

SUMMARY

In one aspect, a telecommunications system is provided. The telecommunications system can include input ports configured for receiving signals at different frequencies. The telecommunications system can also include at least one output port configured for outputting the signals. The telecommunications system can also include a frequency combiner communicatively coupled between the input ports and the at least one output port. The frequency combiner includes adjustable tuning elements, each adjustable tuning element configured to adjust a signal-processing parameter of the frequency combiner while the frequency combiner is in the telecommunications system.

In another aspect, a remote unit of a distributed antenna system is provided. The remote unit is configured to provide wireless communication from a head-end unit to one or more user equipment devices. The remote unit can include a frequency combiner. The frequency combiner includes input ports for receiving signals at different frequencies from the head-end unit. The frequency combiner also includes at least one output port for outputting the signals to the one or more user equipment devices. The frequency combiner also includes a combiner component communicatively coupled between the input ports and the at least one output port. The combiner component includes adjustable tuning elements, each adjustable tuning element being configured to adjust a signal-processing parameter of the frequency combiner while the frequency combiner is in the remote unit.

In another aspect, a method is provided. The method can include receiving multiple signals at different frequencies. The method can also include adjusting signal-processing parameters of a frequency combiner positioned between multiple input ports and an output port of a telecommunications system. The signal processing parameters can be adjusted using adjustable tuning elements while the frequency combiner is in the telecommunications system. The method also includes outputting the signals.

DETAILED DESCRIPTION

Certain aspects and features are directed to a telecommunications system with a frequency combiner that includes adjustable tuning elements for adjusting signal-processing parameters of the frequency combiner while the frequency combiner is in the telecommunications system. For example, a frequency combiner can include input ports that receive multiple signals at different frequencies. The frequency combiner can include adjustable tuning elements for adjusting the phase shifts of the multiple RF paths using phase shifters. The frequency combiner can be frequency independent (e.g., configured to receive and combine signals at any frequency) so that multiple RF modules that each support different frequency bands can be used and adjusted. By adjusting the phase shift of the RF path for each RF module, the frequency combiner can ensure that the RF modules are matched at the output ports. In other aspects, the adjustable tuning elements of the frequency combiner can include an electric length tuner for changing a relative permittivity of the transmission line or a tuning line for varying the physical length of the transmission line. The frequency combiner can be field-configurable and adjustable while implemented in the telecommunications system.

In one example, a distributed antenna system (DAS), repeater, or other telecommunications system can include multiple input ports that are each frequency specific. The telecommunications system can also include one or more output ports. The telecommunications system can include a frequency combiner for combining the multiple input signals for output through the one or more output ports. Adjusting signaling parameters of the frequency combiner can ensure that the phase shifts and other parameters of the multiple RF paths are matched together in the telecommunications system. The adjustable elements of the frequency combiner can be tuned manually or automatically so that RF modules with different input frequencies can be swapped in the telecommunications system while in the field. Further, adjustable tuning elements can provide for low passive intermodulation (PIM) to avoid desensitizing the receive path by PIM products created in the transmit path.

The use of a frequency combiner with adjustable tuning elements can allow for combining input signals of varying frequencies in a telecommunications system while reducing the total number of required frequency-dependent multiplexers. Further, use of a frequency combiner with adjustable elements can offer the flexibility to upgrade and exchange frequency bands in field installations.

These illustrative aspects and examples are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the drawings in which like numerals indicate like elements, and directional descriptions may be used to describe the illustrative aspects but, like the illustrative aspects, should not be used to limit the present disclosure.

FIG. 1is a block diagram of an example of a frequency combiner100for use in a telecommunications system, such as a DAS or a repeater. The frequency combiner100can be positioned between multiple input ports and at least one output port of the telecommunications system. The frequency combiner can include one or more RF modules102a-dcommunicatively coupled to a combiner component108. The combiner component108can include circuitry for adjusting signal-processing parameters of the RF paths for combining the signals of the RF modules102a-d.The combiner component108can combine signals of varying frequencies. The frequency combiner100can be frequency independent while the RF modules102a-dcan be frequency dependent (e.g., each tuned to a specific frequency band). The RF modules102a-dcan each include input ports104a-d.The input ports104a-dcan respectively include receive (RX) ports114a-dfor receiving RF signals and transmit (TX) ports116a-dfor transmitting RF signals. Each of the RX ports114a-dand the TX ports116a-dcan be tuned to a different frequency band. As the frequency combiner100can be frequency independent, RF modules102a-dcan be exchanged while the frequency combiner100is deployed in a telecommunications system to support different frequencies.

For example, RF module102acan include RX port114adesigned to receive signals at frequencies between 925 MHz-960 MHz and TX port116adesigned to transmit signals between 880 MHz-915 MHz. Similarly, RF module102bcan include RX port114bdesigned to receive signals at frequencies between 791 MHz-821 MHz and TX port116bdesigned to transmit signals between 832 MHz-862 MHz. RF module102ccan include RX port114cdesigned to receive signals at frequencies between 1805 MHz-1880 MHz and TX port116cdesigned to transmit signals between 1710 MHz-1785 MHz. RF module102dcan include RX port114ddesigned to receive signals at frequencies between 2620 MHz-2690 MHz and TX port116ddesigned to transmit signals at frequencies between 2500 MHz-2570 MHz. A new frequency range can be used within the frequency combiner100by swapping an RF module102with a new module that supports an RX port for receiving signals at frequencies between 2110 MHz-2170 MHz and a TX port for transmitting signals at frequencies between 1920 MHz-1980 MHz.

Each RF module102a-dcan include amplifiers106a-h for increasing the gain of signals received on RX ports114a-dand transmitted on TX ports116a-d.The RF modules102a-dcan be communicatively coupled to a combiner component108via duplexers118a-d.Duplexers118a-dcan be used to provide bidirectional communication with the combiner component108. For example, the duplexer118aallows signals received on RX port114aand signals transmitted on TX port116ato share the communications path with the combiner component108. The combiner component108can include adjustable tuning elements110a-d.Test signals from each of the RF modules102a-dcan be provided to the combiner component108so that by adjusting of certain signal-processing parameters at the respective adjustable tuning elements110a-dthe RF paths can be optimized for combining signals. For example, the adjusting tuning elements110a-dcan include phase shifters for adjusting the phase shift of each RF path in the combiner component108, electric length tuners for changing the relative permittivity of the transmission lines of the RF paths in the combiner component108, or a tuning line varying the physical length of each transmission line used by the combiner component108. For example, tuning lines can be used for combining signals in starpoint or manifold combiners, where cables between filters are dimensioned with the correct electrical length to each other. After adjusting the signal-processing parameters of the frequency combiner100, the signals of each RF module102a-dcan be combined before being communicated through an output port112.

The adjustable tuning elements110a-dmay be electrically, automatically, or manually adjustable. For example, the tuning element can be controlled by an electric voltage or current. Possible adjustable tuning elements110a-dthat can be electrically controlled are micro-electromechanical systems (MEMS) elements, varactor diodes, variable capacitors, and others. The voltage or current can be changed by a controller. The controller can perform the changes automatically following an algorithm that uses input from the analysis of the combiner component108output. As an example, the controller algorithm can optimize the tuning elements and thus maximize the RF output power.

The adjustable tuning elements110a-dcan also include screws, handles, wheels, or other tools for manual adjustment. The adjustable tuning elements110a-dcan also be coupled and driven by a motor or engine for automatic adjustment. When being adjusted manually, the adjustable tuning elements110a-dcan each be marked per module band in a way to identify to a user how to adjust the adjustable tuning element. For example, an adjustable tuning element110can include a first marking indicating the required adjustments for a first a desired TX frequency and a second marking indicating required adjustments for a second desired TX frequency.

In some aspects, the supported bandwidth of some ports of the frequency combiner100may be limited. In this aspect, a frequency combiner100can include filters for limiting the frequencies of the individual ports into a low band and a high band.FIG. 2is a block diagram that depicts an example of a frequency combiner202followed by a low/high band combiner210. Frequency combiner202can include input ports204a-d,each of which can carry TX signals or RX signals of different frequencies. Signal-processing parameters (e.g., phase shifts) can be adjusted at respective adjustable tuning elements206a-d(e.g., phase shifters), as described above with respect toFIG. 1. The adjustable tuning elements206a-dcan be communicatively coupled to the low/high band combiner210. The low/high band combiner210can include a low pass filter212communicatively coupled to the outputs of adjustable tuning elements206a-b.The low pass filter212filters and outputs signals below a certain threshold frequency. Similarly, the low/high band combiner210can also include a high pass filter214communicatively coupled to the outputs of adjustable tuning elements206c-d.The high pass filter214filters and outputs signals above a certain threshold frequency. The frequency combiner202with the low/high band combiner210can output adjusted signals below a certain threshold frequency and adjusted signals above a certain threshold frequency.

In some aspects, each RF module102a-dof frequency combiner100(shown inFIG. 1) can include components for detecting the power difference between the signals output from the combiner component108with the signals input into the combiner component108. The adjustable tuning elements110a-dof the frequency combiner100can be tuned so that the difference in power is minimized.FIG. 3is a circuit diagram depicting an example of an RF module301of a frequency combiner300that includes circuitry for power detection and control.

The RF module301can include an amplifier302for increasing the power of signals input into the RF module301. The amplified signal can be provided to a pre-RF coupler304, which directs the amplified signal to a duplexer306and a power detector component308. The amplified signal can be provided through the duplexer306to a combiner component320as discussed above with respect toFIG. 1. Adjustable tuning elements316a-dcan adjust signal processing parameters such that the RF path of the amplified signal is optimized for combining with signals from other RF modules (not shown). The combined signal can be provided to a post-RF coupler318, which can provide the combined signal to output port322and to an input of the power detector component308. The power detector component308can thus receive as inputs the signal inputted into the combiner component320and the combined signal output from the combiner component320.

By using a frequency combiner300with a power detector component308in a telecommunications system, a calibration process can be started within the telecommunication system to adjust the signal-processing parameters accordingly. For example, a tone injection signal (e.g., a test signal) can be provided through the amplifier302towards the duplexer306and the power detector component308. The tone injection signal can include continuous-wave (CW) tones per RF module band. The CW tones can be part of the TX passband of the respective RF modules, which produce a certain output power.

The power detector component308of the RF module301can determine a difference in power between the signal inputted into the combiner component320(e.g., the CW tone injection signal) and the signal outputted by the combiner component320. Each RF module301within the frequency combiner can include similar circuitry with a power detector component for comparing the difference of power levels between the signals input into the combiner component320with the combined signal output from the combiner component320. Each power detector component308can provide the difference in power level to a controller310. The difference in power level for each RF module301can also be displayed on a display device312. The controller310can be coupled to a motor314or other automatic tuning element and electronically steer the motor314to automatically tune the adjustable tuning elements316a-d.The controller310, with the use of the motor314, can automatically tune the signal processing parameters of the adjustable tuning elements316a-duntil the difference in power between signals input into the combiner component320and signals output from the combiner component320is minimized and optimized. By adjusting the differences in power to a minimum, the adjustable tuning elements316a-dcan be calibrated to the required needs.

The adjustable tuning elements316a-dcan also include a manual input324for adjusting the signal-processing parameters of the adjustable tuning elements316a-d,as discussed above forFIG. 1. For example, a user can manually adjust the parameters of the adjustable tuning elements316a-duntil the display device312indicates a minimal difference in power between the input signals and output signals. In some aspects, the display device312can present a user interface that can receive inputs from a user. For example, the user interface on the display device312can receive inputs for manually adjusting and tuning the adjustable tuning elements316a-d.

The frequency combiners100,202,300can be implemented in a telecommunications system, such as a repeater or a DAS. For example,FIG. 4is a block diagram of an example of a repeater400with a frequency combiners410a-bfor combining and splitting multiple signals of varying frequencies. Multiple frequency bands can be received from base stations (not shown) wirelessly via one or more donor antennas402. The multiple frequencies can be split into separate frequency bands and separated into transmit (TX) paths404a-dand receive (RX) paths406a-dusing frequency combiner410a.Each of the separate TX paths404a-dand RX paths406a-dcan carry signals on separate frequency bands. After extracting the separate TX paths404a-dand RX paths406a-d,signal-processing components408can amplify signals on the TX paths404a-dand RX paths406a-dto a desired output power. Signal-processing components408can include, for example, analog RF components or digital signal-processing components. After a final amplification to a desired output power, the individual TX paths404a-dand RX paths406a-dcan be combined using frequency combiner410b.The resulting combined output signal can be transmitted via one or more output ports412to one or more antennas or radiating cables (not shown) in order to provide signal coverage to user equipment devices positioned within the coverage zone.

Similarly, frequency combiners100,202,300can be implemented in a DAS.FIG. 5depicts an example of frequency combiners510a-bimplemented in a DAS500. Specifically, DAS500can include remote units502a-bthat include frequency combiners510a-baccording to aspects discussed herein. The remote units502a-bcan provide signal coverage to user equipment devices positioned within respective coverage zones. The remote units502a-bcan communicate with base stations504a-evia a head-end unit506. Remote units502a-bcan be communicatively coupled with head-end unit506via a direct wired connection or a wireless connection. For example, remote units502a-bcan be communicatively coupled with head-end unit via copper cables, optical fiber, or a wireless communication medium. WhileFIG. 5depicts DAS500with a single head-end unit506, the DAS500can also include multiple head-end units.

The head-end unit506can receive downlink signals from base stations504a-eand transmit uplink signals to the base stations504a-e.Any suitable communication link can be used for communication between the base stations504a-eand the head-end unit506. For example, the base stations504a-eand the head-end unit506can be communicatively coupled using a direct connection (e.g., copper cable or optical fiber) or a wireless communication medium. In some aspects, the head-end unit506can include an external repeater or internal RF transceiver to communicate with base stations504a-e.

Base stations504a-ecan communicate signals on multiple frequencies and on different operators with head-end unit506. The head-end unit506can include duplexers508a-efor providing bi-directional communication with base stations504a-e.For example, downlink signals from base station504acan be separated from uplink signals to base station504avia duplexer508a.The downlink signals from base stations504a-ecan be provided to a splitting/combining matrix512a.Splitting/combining matrix512acan combine the downlink signals from base stations504a-eto the appropriate downlink paths514a-bintended for the respective remote units502a-b.Downlink signals on downlink paths514a-bcan then be provided to optical transceivers516a-band then transmitted to remote units502a-b.Thus, downlink signals from base stations504a-ethat are intended for remote unit502acan be combined via splitting/combining matrix512aand transmitted to remote unit502a.Similarly, downlink signals from base stations504a-ethat are intended for remote unit502bcan be combined via splitting/combining matrix512aand transmitted to remote unit502b.The downlink signals transmitted to remote units502a-bcan include signals on multiple frequencies (e.g., each base station504a-ecan transmit downlink signals on a respectively different frequency band).

The remote units502a-bcan include frequency combiners510a-baccording to aspects described herein. The frequency combiners510a-bcan include adjustable tuning elements110a-d(shown inFIG. 1) for adjusting the signal-processing parameters of the frequency combiners510a-b.For example, adjustable tuning elements110a-dcan adjust the phase shift of each downlink RF path to ensure that the downlink RF paths are matched optimally for combining the downlink signals and outputting the downlink signals from the remote units502a-b.Implementing frequency combiners510a-bin remote units502a-bcan allow the DAS500to support new frequency bands from base stations504a-e.

Uplink signals transmitted by user equipment devices can be received by remote units502a-b.The remote units502a-bcan separate the uplink signals received from user equipment devices via frequency combiners510a-band transmit the separated uplink signals to head-end unit506. The uplink signals from each remote unit502a-bcan be respectively provided to optical transceivers516a-b,which can be used for bi-directional communication between head-end unit506and remote units502a-b.The uplink signals can be provided on uplink paths518a-bto splitting/combining matrix512b.The splitting/combining matrix512bcan split the uplink signals from each remote unit502a-bfor transmittal to the appropriate base stations504a-e.For example, uplink signals from remote unit502amay include combined signals on multiple frequency bands, signals on each frequency band intended for a respective base station504a-e.Splitting/combining matrix512bcan split the uplink signals according to frequency band and direct the split uplink signals to the correct base stations504a-e.The uplink signals can be provided to duplexers508a-eand output to base stations504a-e.

WhileFIGS. 4 and 5depict block diagrams of frequency combiners being implemented in a repeater and a DAS, respectively, frequency combiners can be included in any telecommunications system.

FIG. 6is a flowchart depicting an example process600for combining separate frequency bands using a frequency combiner. The process600is described with respect to the system depicted inFIG. 1. Other implementations, however, are possible. Process600can include receiving signals at different frequencies, as shown in block610. For example, as discussed above with respect toFIG. 1, a frequency combiner100can include RF modules102a-d,each RF module102a-dtuned to receive and transmit signals on a different frequency band. The frequency combiner can receive signals on different frequencies via RF modules102a-d.

Process600can further include adjusting signal-processing parameters of a frequency combiner positioned between multiple input ports and an output port of a telecommunications system while the frequency combiner is in the telecommunications system, as shown in block620. For example, frequency combiner100can include a combiner component108with adjustable tuning elements110a-d.The frequency combiner100can be positioned between input ports104a-dthat receive multiple signals on different frequencies and at least one output port112. Signals received on each of the input ports104a-dcan be provided to RF modules102a-d.Signals from RF modules102a-dcan be provided to adjustable tuning elements110a-d.The signal-processing parameters of the frequency combiner100can be adjusted by automatically or manually adjusting adjustable tuning elements110a-d.For example, adjustable tuning elements110a-dcan adjust the phases of phase shifters, adjust the relative permittivity of electrical length tuners or vary the physical length of transmission lines. Thereby the phase shift of each RF path can be adjusted. The phase-matched RF paths allow for combining the multiple received signals in the combiner component108without the use of frequency-dependent multiplexers.

The signal-processing parameters of frequency combiner can be adjusted while the frequency combiner100is in a telecommunications system. For example, the adjustable tuning elements102a-dcan be adjusted while the frequency combiner100is already deployed in the field within a telecommunications system, such as a DAS or a repeater. The signal-processing parameter can include phase shifting or varying the electrical length of a transmission line. Further, the frequency bands utilized by the telecommunications system can be upgraded while the telecommunications system is deployed in the field by exchanging the RF modules102a-das described above with respect toFIG. 1.

Process600can also include outputting the combined signals, as shown in block630. For example, after adjusting the RF paths and combining the received signals, the frequency combiner100can output the signals via an output port112. In one aspect, the frequency combiner100can be included in a repeater unit400and the signals output to one or more remote units in communication with the repeater unit400. In another aspect, the frequency combiner100can be included in a remote unit502and the signals output to one or more user equipment devices within a coverage zone of the remote unit502.

The foregoing description of the examples, including illustrated examples, of the disclosed subject matter has been presented only for the purpose of illustration and description and is not intended to be exhaustive or to limit the subject matter to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof can be apparent to those skilled in the art without departing from the scope of this subject matter. The illustrative examples described above are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts.