Patent Description:
The present invention generally relates to waveguides and more particularly to waveguide feed networks.

Waveguide feed networks that can transmit left hand and right hand circularly polarized signals through circular waveguides and also can receive left hand and right hand circularly polarized signals from circular waveguides may require two transmit ports and two receive ports with good isolation between the ports. The waveguide feed networks may require filtering to provide the required isolation between the ports. Transmitter circuits may be coupled to transmit ports and receiver circuits may be coupled to the receive ports for transmitting and receiving the signals.

The waveguide feed network may be coupled to circular waveguides to implement a transformation from a linearly polarized signal at a transmit port to one of the left hand circularly polarized signal or right hand circularly polarized signal at the circular waveguide. Alternatively, the waveguide feed network may implement a transformation from one of the left hand circularly polarized signal or right hand circularly polarized signal at the circular waveguide to a linearly polarized signal at a receive port. This can make the design of an integrated waveguide feed network for transmitting and receiving signals with both left hand circular polarization and right hand circular polarization very complex.

In view of the foregoing, low complexity compact waveguide feed networks are required.

Document<CIT> relates to an assembly having an asymmetric diplexing orthomode transducer comprising two branches coupled to a main waveguide by two parallel coupling slots. The branches are respectively linked to two waveguides of an unbalanced branched coupler. The slots are formed in two orthogonal walls of the waveguide, and linked to the coupler via stub filters and recombination circuits. The coupler has two different splitting coefficients that are optimized to compensate for orthogonal spurious components of electric field produced by the asymmetry of the transducer. An independent claim is also included for a method for developing a compact excitation assembly for generating a circular polarization in an antenna.

Document<CIT> relates in general to microwave multiplexers and to improved high frequency multiplexer apparatus which allows the use of a single antenna and/or transmission line for simultaneous transmission and reception of signals within a plurality of frequency bands. Document D3<CIT> describes an antenna system including: an input port configured to receive tracking mode signals, in two orthogonal polarizations, from a target; a tracking coupler, configured to receive the tracking mode signals from the input port, the tracking coupler including: a first pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a first one of the orthogonal polarizations, and a second pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a second one of the orthogonal polarizations; and a tracking combiner network configured to combine the extracted tracking signals from the pairs of opposed slot couplers to generate tracking output signals for use in controlling the antenna system to track the target.

Document <CIT> relates to transmitting and receiving antenna comprises an array of feeds clustered by groups of four adjacent feeds along two directions X, Y of a plane, each feed comprising two transmitting ports and two receiving ports with orthogonal polarizations. For each group of four adjacent feeds, the first, or the second, transmitting ports, respectively the first, or the second, receiving ports, corresponding to a same pair of frequency and polarization values are connected two-by-two in the direction X then two-by-two in the direction Y, the four interconnected transmitting ports forming a transmitting beam and the four interconnected receiving ports forming a receiving beam.

The present invention relates to a feed network, a receiver unit and a method of operating a transmitter unit. The present invention is defined by the set of appended claims. In the following, parts of the description and drawing referring to examples, which are not covered by the claims are not presented as embodiments of the invention, but as illustrative examples useful for understanding the invention.

According to various aspects of the subject technology, a transmitter unit of a feed network for transmitting circularly polarized signals is described according to claim <NUM>.

According to various aspects of the subject technology, a receiver unit of a feed network for receiving circularly polarized signals is described according to claim <NUM>.

According to various aspects of the subject technology, a method of operating a transmitter unit of a feed network for transmitting circularly polarized signals is described according to claim <NUM>.

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions to be taken in conjunction with the accompanying drawings describing specific aspects of the disclosure, wherein:.

The present disclosure is directed, in part, to a feed network with dual circular polarization for satellite communications. A satellite may include a satellite receiver coupled to a satellite antenna system for receiving uplink signals, and may also include a satellite transmitter coupled to the satellite antenna system for transmitting downlink signals. The feed network may be coupled between elements of the satellite antenna system and the satellite receiver and also may be couple between the elements of the satellite antenna system and the satellite transmitter. The feed network that couples the satellite transmitter to the satellite antenna system may transform a linearly polarized signal received from the satellite transmitter into one of a right hand or a left hand circularly polarized signals for the satellite antenna system to be transmitted. Also, the feed network that couples the satellite receiver to the satellite antenna system may transform a received right hand or left hand circularly polarized signal from the satellite antenna system into a linearly polarized signal for the receiver. By providing circularly polarized signals for communication to and from the satellite, the communications may not be sensitive to an orientation of transceiver devices that communicates with the satellite.

The feed network includes a receiver unit and a transmitter unit. The transmitter unit may include two branches and two input ports, a first input port on a first end of a first branch and a second input port on a first end of a second branch. The input ports may also be coupled to circuitry for receiving input signals that can be linearly polarized signals. The transmitter unit can be coupled to a core waveguide, e.g., a circular waveguide, via the second end of the two branches that can include evanescent waveguides and may provide a circularly polarized signal based on the received signals at the input ports. The transmitter unit may provide a left hand circularly polarized signal at the core waveguide when the input signal is received from the first input port and may provide a right hand circularly polarized signal at the core waveguide when the input signal is received from the second input port. The transmitter unit may include an integrated branch line coupler between the two branches for generating the left hand and right hand circularly polarized signals. The integrated branch line coupler may have one or more branches between the first and second branches to form a branch line coupler. The integrated branch line coupler may include waveguide filters performing as waveguide reject filters that are integrated into the first and second branches. The waveguide reject filters may be used for isolating the input ports from undesired signals in the core waveguide. The waveguide reject filters of the integrated branch line coupler may include single-sided stubs that may be used for further tuning the waveguide reject filters.

Additionally, the receiver unit may include two branches and two output ports, a first output port at a first end of a first branch and a second output port at a first end of a second branch. The receiver unit can be coupled to a core waveguide, e.g., a circular waveguide, via the second end of the two branches to receive a left hand or right hand circularly polarized signal. The receiver unit may receive a left hand circularly polarized signal from the core waveguide and may provide a linearly polarized signal at a first output port. Alternatively, the receiver unit may receive a right hand circularly polarized signal from the core waveguide and may provide a linearly polarized signal at a second output port. The receiver unit may include an integrated branch line coupler coupled between the two branches for creating linearly polarized signals from the left hand and right hand circularly polarized signals. Waveguide reject filters may be integrated into each one of the branches of the integrated branch line coupler for isolating the output ports from undesired signals in the core waveguide. The subject technology includes a number of advantageous features. For example, the disclosed system provides a compact and low complexity feed network by the couplers and the rejection filters at the two sides of each branch and also by arranging the transmitter unit and receiver unit on a same core waveguide.

<FIG> illustrates a diagram of an example waveguide feed network, according to some aspects of the disclosure. Waveguide feed network <NUM> includes transmit section <NUM>, receive section <NUM>, and a body section <NUM>. As shown in the figure, body section <NUM> includes first lower portion <NUM>, first upper portion <NUM>, and second upper portion <NUM>. Transmit section <NUM> of waveguide feed network <NUM> includes second lower portion <NUM> and third upper portion <NUM>. First upper portion <NUM>, third upper portion <NUM>, first lower portion <NUM>, and second lower portion <NUM> may together include a transmitter unit that is described in more details with respect to <FIG> as transmitter unit <NUM>.

Additionally, receive section <NUM> of waveguide feed network <NUM> includes third lower portion <NUM> and fourth upper portion <NUM>. Second upper portion <NUM>, fourth upper portion <NUM>, first lower portion <NUM>, and third lower portion <NUM> may together include a receive unit that is described in more details with respect to <FIG> as receiver unit <NUM>.

Additionally, transmit section <NUM> of <FIG> includes core waveguide <NUM> having an outer body <NUM> that is coupled to second lower portion <NUM>. In some examples, core waveguide <NUM> may extend from outer body <NUM> of transmit section <NUM>, through second lower portion <NUM> of transmit section <NUM>, and through first lower portion <NUM> of body section <NUM> to third lower portion <NUM> of receive section <NUM>. In some examples, a diameter of core waveguide <NUM> may change one or more times when passing through outer body <NUM> to third lower portion <NUM>. In some examples, core waveguide <NUM> is a circular waveguide. In some other examples, core waveguide <NUM> is a cruciform waveguide.

In some examples, the transmitter unit, shown in <FIG>, comprises two segments. A first segment of the transmitter unit is included in first upper portion <NUM> and first lower portion <NUM> of body section <NUM> and a second segment of the transmitter unit is included in third upper portion <NUM> and second lower portion <NUM> of transmit section <NUM>. Thus, the transmitter unit is formed when transmit section <NUM> and body section <NUM> are connected to each other. In some examples, connecting transmit section <NUM> and body section <NUM> also forms two input ports <NUM> and <NUM>. In some examples, the transmitter unit receives a signal through one of input ports <NUM> and <NUM> that causes the transmitter unit to transmit a circularly polarized wave through core waveguide <NUM>. In some examples, the transmitter unit receives signal through input port <NUM> and transmits a right hand circularly polarized wave through core waveguide <NUM>. In some examples, transmitter unit receives the signal through input port <NUM> and transmits a left hand circularly polarized wave through core waveguide <NUM>. In some examples, waveguide feed network <NUM> provides an isolation of better than <NUM> dB between input ports <NUM> and <NUM> of the transmitter unit.

In some examples, the receiver unit, shown in <FIG>, comprises two segments. A first segment of the receiver unit is included in second upper portion <NUM> and first lower portion <NUM> of body section <NUM> and a second segment of the receiver unit is included in fourth upper portion <NUM> and third lower portion <NUM> of receive section <NUM>. Thus, the receiver unit is formed when receive section <NUM> and body section <NUM> are connected to each other. In some examples, connecting receive section <NUM> and body section <NUM> also forms two output ports <NUM> and <NUM>. In some examples, the receiver unit receives a circularly polarized wave through core waveguide <NUM> that causes the receiver unit to generate a signal at one output ports <NUM> or <NUM>. In some examples, the receiver unit receives a right hand circularly polarized wave and generates a signal at output port <NUM>. In some examples, the receiver unit receives a left hand circularly polarized wave and generates a signal at output port <NUM>. In some examples, waveguide feed network <NUM> provides an isolation of better than <NUM> dB between output ports <NUM> and <NUM> of the receive unit. In some examples, waveguide feed network <NUM> is a compact and low complexity excitation assembly for generating /receiving a circular polarization in/from core waveguide <NUM>. In some examples, waveguide feed network <NUM> is made of aluminum.

<FIG> illustrates a perspective view of a body section of an example waveguide feed network, according to some aspects of the disclosure. As shown, body section <NUM> includes first lower portion <NUM> that includes a first segment of core waveguide <NUM> having perimeter <NUM>. In some examples, second lower portion <NUM> of transmit section <NUM> includes a complementary second segment of core waveguide <NUM> that together with the first segment of core waveguide <NUM>, when body section <NUM> is connected to transmit section <NUM>, form core waveguide <NUM> of the transmitter unit. Core waveguide <NUM> is described with respect to <FIG> and <FIG>.

Body section <NUM> also includes first upper portion <NUM> that includes a plurality of openings with length <NUM> that make a first segment of a plurality of rectangular waveguides that are described in more details with respect to <FIG> as transmitter unit <NUM>. The first segment of the plurality of rectangular waveguides forms the first segment of the transmitter unit which also includes a first segment of input ports <NUM> and <NUM>. In some examples, third upper portion <NUM> of transmit section <NUM> includes a plurality of similar openings that make a complementary second segment of the plurality of rectangular waveguides that form the complementary second segment of the transmitter unit. In some examples, the first segment of a plurality of rectangular waveguides in first upper portion <NUM> and the second segment of a plurality of rectangular waveguides in third upper portion <NUM> are symmetrical with respect an outer surface of first upper portion <NUM> and thus a zero electric field is generated at the outer surface of first upper portion <NUM>. Also, in some examples, a length of the plurality of rectangular waveguides of the transmitter unit is twice length <NUM>.

<FIG> illustrates a cross sectional diagram of an example transmitter unit, according to some aspects of the disclosure. A perspective view of transmitter unit <NUM> is shown with respect to <FIG>. In some examples, a linearly polarized input signal is received through one of input ports <NUM> or <NUM> and circularly polarized signal is generated in core waveguide <NUM>. An operation of transmitter unit <NUM> is described with respect to <FIG>. In some examples, transmitter unit <NUM> is a cross sectional surface through waveguide feed network <NUM> of <FIG>, e.g., along a contact surface between body section <NUM> and transmit section <NUM> as shown in <FIG>. Transmitter unit <NUM> shows core waveguide <NUM> with perimeter <NUM> around core waveguide <NUM> as shown in <FIG> as well as a smaller perimeter <NUM> of the core waveguide at the receiver unit. In some examples, diameter D2 of the core waveguide of waveguide feed network <NUM> is smaller at the receiver unit compared to diameter D1 at the transmitter unit. In some examples, the smaller diameter of the core waveguide at the receiver provides a higher cut off frequency for the receiver unit compared to the transmitter unit.

Transmitter unit <NUM> shows two branches 310A and 310B that are coupled to core waveguide <NUM>. Each one of branch 310A or 310B includes waveguide reject filter 312A or 312B that includes one or more stubs, e.g., three stubs. As an example, <FIG> shows three single-sides stubs 302A, 302C, and 302E on branch 310A as well as three single-sides stubs 302B, 302D, and 302F on branch 310B. As shown the stubs are protruding outward. In some examples, the waveguide filters are waveguide reject filters that are implemented to prevent signals in certain frequency bands to reach input ports <NUM> and <NUM> of <FIG>, <FIG>. In some examples, waveguide reject filters 312A or 312B are low pass filters and the sizes of filters 312A and 312B including the sizes of stubs 302A, 302B, 302C, 302D, 302E, and 302F as well as a number of the stubs may be determined based on an allowed wavelength and a rejection band of the waveguide reject filters. In some examples, waveguide reject filters 312A and 312B suppress a signal in a predetermined range that is received via the core waveguide from reaching input ports <NUM> and <NUM>.

In some examples, the C band is used for receiving and transmitting signals and allowed frequency ranges and stop (e.g., suppressed) frequency ranges of the transmitter unit are predefined. In some examples, a transmitting frequency band includes frequencies <NUM> to <NUM> that may pass from input ports <NUM> or <NUM> to core waveguide <NUM>. The receiving frequency band includes frequencies <NUM> to <NUM> that are suppressed, e.g., by more than <NUM> dB, from reaching input ports <NUM> or <NUM> from the core waveguide. Thus, an isolation of better than <NUM> dB may be achieved for input ports <NUM> and <NUM> from undesired signals in the core waveguide that are in the receiving frequency band.

As shown, a free end of stubs 302A, 302B, 302C, 302D, 302E, and 302F may be short-circuited. Then an input impedance of a short-circuited stub is purely reactive; either capacitive or inductive, depending on the electrical length and width of the stubs and a wavelength of signal passing through waveguide reject filters 312A or 312B. Stubs may thus function as capacitors and inductors in waveguide reject filters 312A or 312B and may be used to tune a bandwidth of waveguide reject filters 312A or 312B. As shown in <FIG>, more than three stubs, e.g., five stubs may be integrated into the waveguide reject filters of each branch to further shape a frequency response of waveguide reject filters.

Additionally, transmitter unit <NUM> shows two evanescent waveguides 304A and 304B that are coupled between branches 310A and 310B and core waveguide <NUM>. In some examples, a size of evanescent waveguides 304A and 304B are adjusted such an insertion loss between core waveguide <NUM> and the waveguide reject filters 312A and 312B of branches 310A and 310B are less than a predetermined level, e.g., less than <NUM> dB, in each branch. In some examples, evanescent waveguides 304A and 304B of first and second branches 310B and 310A of transmitter unit <NUM> have predetermined angles, e.g., <NUM> degrees, when coupled to the core waveguide. The <NUM>-degree turns of evanescent waveguides 304A and 304B may cause a supposed continuation of branches 310A and 310B to intersect each other at a center of core waveguide <NUM> with an angle A equal to <NUM> degrees. Thus, the ends of the branches 310A and 310B coupled to the core waveguide <NUM> may become perpendicular to each other. Additionally, the <NUM>-degree turn may allow integrated branch line coupler <NUM> to stay close to core waveguide <NUM>, reducing a size and mass of transmitter unit <NUM> to make it compact.

In addition, transmitter unit <NUM> shows transformers 306A, 306B, 306C, and 306D on branches 310A and 310B. The transformers have dimensions that are determined based on a frequency range of the transmitted signals that may be input at input ports <NUM> and <NUM> and to minimize an insertion loss of the transmitter unit. In some examples, the one or more transformers of each branch 310A or 310B are quarter wave transformers that are configured to provide a change of wavelength for matching. By using transformers 306A, 306B, 306C, and 306D, to change the wavelength, branches 310A or 310B may match to a transmitter circuit that can be coupled to input ports <NUM> and <NUM>. In some examples, quarter wave transformer WR229 may be used.

In some examples, waveguide reject filters 312A and 312B of branches 310A and 310B of transmitter unit <NUM> are low pass filters. Waveguide reject filters 312A and 312B may transmit received input signals at a first frequency, e.g., in a range between <NUM> and <NUM>, from input ports <NUM> and <NUM> to core waveguide <NUM>. The waveguide reject filters may reject a second signal at a second frequency greater than the first frequency, e.g., in a range between <NUM> and <NUM>. Thus, waveguide reject filters 312A and 312B may prevent a received second signal in the second frequency from core waveguide <NUM> to reach input ports <NUM> and <NUM>.

Transmitter unit <NUM> shows integrated branch line coupler <NUM> that includes couplers 314A, 314B, and 314C that inwardly couple branches 310A and 310B. Integrated branch line coupler <NUM> also includes waveguide reject filters 312A and 312B that are described above. A number, size, and location of couplers 314A, 314B, and 314C may be selected to create left hand circular polarization as well as right hand circular polarization signals in core waveguide <NUM>. The circular polarization signals are created based on the linearly polarized signals that are received from input ports <NUM> and <NUM> of branches 310A and 310B. In some examples, waveguide reject filters 312A or 312B have an inner face and an outer face. In some examples, couplers 314A, 314B, and 314C are coupled between the inner face of waveguide reject filters 312A or 312B. In some examples, integrated branch line coupler <NUM> provides splitting a power by 3dB and a <NUM> degrees phase shift to generate a circular polarization mode from a linear polarization mode. In some examples, width <NUM> of couplers 314A, 314B, and 314C can provide the <NUM> degrees phase shift. Waveguide reject filters 312A or 312B of integrated branch line coupler <NUM> may isolate an unwanted circular polarization mode to get to input ports <NUM> or <NUM>.

In some examples, integrated branch line coupler <NUM> may also provide a predetermined axial ratio, e.g., <NUM> dB axial ratio, over a bandwidth of up to <NUM> percent, between the left hand and right hand circularly polarized signals. In some examples, a distance between couplers 314A, 314B, and 314C, depends on diameter D1 of core waveguide <NUM>. In some examples, couplers 314A, 314B, and 314C are e-plane couplers and a height of the couplers may determine an amount of energy that may be transferred between the branches. As an example, height <NUM> of coupler 314B determines an amount of energy that may be transferred between the branches 310A and 310B. Integrated branch line coupler <NUM> is described with respect to <FIG>.

Additionally, in some examples, stubs 302A, 302B, 302C, 302D, 302E, and 302F are coupled to and extended from the outer face of waveguide reject filters 312A or 312B. In some examples, the one or more single-sided stubs 302A, 302B, 302C, 302D, 302E, and 302F of waveguide reject filters 312A and 312B correspond to one or more cascaded filter sections. As shown in <FIG>, one or more single-sided stubs 302A, 302B, 302C, 302D, 302E are coupled outwardly to waveguide reject filters 312A or 312B. Additionally, couplers 314A, 314B, and 314C are coupled inwardly to waveguide reject filters 312A or 312B in between a location of the one or more single-sided stubs. In some examples, waveguide reject filters 312A and 312B allows a signal being in frequency range <NUM> to <NUM> to pass, e.g., from input ports <NUM> and <NUM> to core waveguide <NUM>. In some examples, waveguide reject filters 312A and 312B suppresses a signal being in frequency range <NUM> to <NUM> to pass, e.g., from core waveguide <NUM> to any of input ports <NUM> and <NUM>, and provide at least a <NUM> dB isolation.

In some examples, integrated branch line coupler <NUM> generates, at core waveguide <NUM>, one or both of a right hand circularly polarized signal and a left hand circularly polarized signal from a linearly polarized signal. In some examples, transmitter unit <NUM> receives an input signal at a first frequency from input port <NUM> of first branch 310B and generates a right hand circularly polarized signal at the first frequency in core waveguide <NUM>. In some examples, transmitter unit <NUM> receives an input signal at a first frequency from input port <NUM> of second branch 310A and generates a left hand circularly polarized signal at the first frequency in the core waveguide.

<FIG> illustrates components of an example integrated branch line coupler, according to some aspects of the disclosure. Diagram <NUM> of <FIG> shows integrated branch line coupler <NUM> that is consistent with integrated branch line coupler <NUM> of <FIG>. In some examples, integrated branch line coupler <NUM> is an integration of branch line coupler <NUM> and portions of corrugated low pass filters 412A and 412B. Branch line coupler <NUM> may have a plurality of couplers <NUM>. Corrugated low pass filters 412A and 412B may have a plurality of stubs <NUM>. Integrated branch line coupler <NUM> may be viewed as an integration of branch line coupler <NUM>, upper half of corrugated low pass filter 412A, and lower half of corrugated low pass filter 412B. Alternatively, integrated branch line coupler <NUM> may be viewed as an integration of branch line coupler <NUM> and one of the corrugated low pass filters 412A or 412B. In some examples, the plurality of couplers <NUM> and the plurality of stubs <NUM> do not face each other when coupled in integrated branch line coupler <NUM>. In some examples, integrated branch line coupler <NUM> performs functions of filtering as well as dividing power and providing phase shift to create linearly polarized signals.

<FIG> illustrates a perspective view of a receive section of an example waveguide feed network, according to some aspects of the disclosure. As shown, receive section <NUM> includes third lower portion <NUM> that includes core waveguide <NUM> having perimeter <NUM>. In some examples, third lower portion <NUM> of receive section <NUM> includes a complementary second segment of core waveguide <NUM> that together with the first segment of core waveguide <NUM> form core waveguide <NUM> of the receiver unit. In some examples, a diameter of core waveguide <NUM> changes, e.g., is reduced, between the transmitter unit and the receiver unit such that core waveguide <NUM>, which is a portion of core waveguide <NUM>, has a smaller diameter compared to anther portion of core waveguide <NUM>, which is core waveguide <NUM>. Core waveguides <NUM> and <NUM> are described in more details with respect to <FIG> and <FIG>.

Receive section <NUM> also includes fourth upper portion <NUM> that includes a plurality of openings with length <NUM> that make a first segment of a plurality of rectangular waveguides that are described in more details with respect to <FIG> as receiver unit <NUM>. The first segment of the plurality of rectangular waveguides forms the first segment of the receiver unit which also includes a first segment of output ports <NUM> and <NUM>. In some examples, second upper portion <NUM> of body section <NUM> includes a plurality of similar openings that make a complementary second segment of the plurality of rectangular waveguides that form the complementary second segment of the receiver unit. In some examples, the first segment of a plurality of rectangular waveguides in fourth upper portion <NUM> and the second segment of a plurality of rectangular waveguides in second upper portion <NUM> are symmetrical with respect to an outer surface of fourth upper portion <NUM> and thus a zero electric field is generated at the outer surface of fourth upper portion <NUM>. In addition, in some examples, a length of the plurality of rectangular waveguides of the transmitter unit is twice length <NUM>.

<FIG> illustrates a cross sectional diagram of an example receiver unit, according to some aspects of the disclosure. A perspective view of receiver unit <NUM> is shown with respect to <FIG>. In some examples, receiver unit <NUM> shows a cross sectional surface through waveguide feed network <NUM> of <FIG>, e.g., along a contact surface between body section <NUM> and receive section <NUM> as shown in <FIG>. Receiver unit <NUM> shows core waveguide <NUM> with perimeter <NUM> around core waveguide <NUM> as shown in <FIG>. In some examples, core waveguide <NUM> has diameter D2 shown also in <FIG>.

In some examples, circularly polarized signals are received through core waveguide <NUM> via branches 610A and 610B that are coupled to core waveguide <NUM>. The received signals pass through filters 612A and 612B as well as couplers 614A, 614B, and 614C, and generate a linearly polarized signal. The linearly polarized signal may be generated at one of output ports <NUM> or <NUM> depending on the signal being right hand circularly polarized or left hand circularly polarized, respectively. In some examples, an isolation of better than <NUM> dB is provided between output ports <NUM> and <NUM>. In some examples, waveguide reject filters 612A and 612B allows a signal being in frequency <NUM> to <NUM> to pass, e.g., from core waveguide <NUM> to one of output ports <NUM> and <NUM>. In some examples, waveguide reject filters 612A and 612B suppresses a signal being in frequency range <NUM> to <NUM> to pass, e.g., from core waveguide <NUM> to any of output ports <NUM> and <NUM>, and provides at least <NUM> dB isolation.

Receiver unit <NUM> includes two branches 610A and 610B that are coupled to core waveguide <NUM>. Each one of branch 610A or 610B includes waveguide reject filters 612A or 612B. Waveguide reject filters 612A and 612B may have dimensions that are determined based on a frequency of the transmitted signals, and may act as transmit reject filters. Waveguide filters 612A and 612B may also be called waveguide reject filters 612A and 612B that suppress rectangular mode TE10 in the frequency range of <NUM> and <NUM>. Thus, waveguide reject filters 612A and 612B may perform a filtering, e.g., high pass filtering, to suppress the transmitter signals and further prevent the transmitter signals from reaching output ports <NUM> or <NUM> of the receiver unit.

Receiver unit <NUM> shows integrated branch line coupler <NUM> that includes couplers 614A, 614B, and 614C that inwardly couples branches 610A and 610B. Integrated branch line coupler <NUM> also includes waveguide reject filters 612A or 612B that are described above. A number, size, and location of the couplers 614A, 614B, and 614C may be selected to transform left hand circular polarization as well as right hand circular polarization signals at core waveguide <NUM> to linearly polarized signals at output ports <NUM> and <NUM> of branches 610A and 610B. In some examples, a distance between couplers 614A, 614B, and 614C, depends on diameter D2 of core waveguide <NUM>. In some examples, couplers 614A, 614B, and 614C are e-plane couplers.

In some examples, the waveguide filters, e.g., waveguide reject filters 612A or 612B have an inner face and an outer face. In some examples, integrated branch line coupler <NUM> comprises couplers 614A, 614B, and 614C that are coupled between the inner face of the waveguide reject filters 612A or 612B. As described, integrated branch line coupler <NUM> may divide power and generate phase shift to create linearly polarized signals from circularly polarized signals. In some examples, couplers 614A, 614B, and 614C of integrated branch line coupler <NUM> generates a linearly polarized signal at a first frequency from a circularly polarized signal at the first frequency. In some examples, the integrated branch line coupler provides, splitting a power by 3dB, causing <NUM> degrees phase shift to generate a linear polarization from a circular polarization mode, and isolating a signal to get to the other port.

In addition, receiver unit <NUM> shows transformers 606A, 606B, 606C, and 606D on branches 610A and 610B. The transformers have dimensions that are determined based on a frequency of the received signals from the core waveguide and to minimize an insertion loss of the receiver unit at output ports <NUM> and <NUM>. In some examples, the one or more transformers of each branch 610A or 610B are quarter wave transformers that are configured to provide a change of wavelength for matching. By using transformers 606A, 606B, 606C, and 606D, to change wavelength, branches 610A or 610B may match to a receiver circuit that can be coupled to output ports <NUM> and <NUM>. In some examples, quarter wave transformer WR137 may be used.

In some examples, the circularly polarized signal is received from core waveguide <NUM> and the linearly polarized signal is generated at an output of waveguide reject filters 612A and 612B that is coupled to a transformer. In some examples, receiver unit <NUM> receives a right hand circularly polarized signal at a first frequency from core waveguide <NUM> and generates an output signal at the first frequency at output port <NUM> of second branch 610B. In some examples, receiver unit <NUM> receives a left hand circularly polarized signal at a first frequency from core waveguide <NUM> and generates an output signal at the first frequency at output port <NUM> of first branch 610A. In some examples, branches 610A or 610B have a <NUM>-degree turn, e.g., bend, at an end that attaches to core waveguide <NUM>. The <NUM>-degree turn may allow integrated branch line coupler <NUM> to stay close to core waveguide <NUM>, reducing a size and mass of receiver unit <NUM> and creating a compact receiver unit. In some examples, placing integrated branch line coupler <NUM> close to core waveguide <NUM> may allow more effective impedance matching between core waveguide <NUM> and receiver unit <NUM>.

<FIG> illustrates a perspective view of an example waveguide feed network, according to some aspects of the disclosure. Returning back to <FIG>, diagram <NUM> of <FIG> shows core waveguide <NUM> of the transmitter unit. Core waveguide <NUM> is consistent with a portion of core waveguide <NUM> of <FIG> that is coupled to branches 310A and 310B. <FIG> also shows core waveguide <NUM> of the receiver unit that is consistent with a portion of core waveguide <NUM> of <FIG> that is coupled to branches 610A and 610B. Core waveguides <NUM> and <NUM> are coupled together via core waveguide <NUM> extended between the transmitter unit and receiver unit inside first lower portion <NUM> of body section <NUM>. A diameter of core waveguides <NUM>, <NUM>, and <NUM> are described with respect to <FIG>. Diagram <NUM> also shows core waveguide <NUM> that is extended outward. In some examples, waveguide feed network <NUM> receives signals from input ports <NUM> and <NUM> and transmits circularly polarized signals through core waveguide <NUM>. In some examples, waveguide feed network <NUM> receives signals from core waveguide <NUM> and provides output signals through output ports <NUM> and <NUM>. Diagram <NUM> additionally shows a perspective view of branches 310A and 310B of the transmitter unit that include input ports <NUM> and <NUM> and a perspective view of branches 610A and 610B of the receiver unit that include output ports <NUM> and <NUM>.

<FIG> illustrates a side view of an example waveguide feed network, according to some aspects of the disclosure. In some examples, diagram <NUM> of <FIG> is a side view of diagram <NUM> of <FIG> that shows a side view of branch 310A of the transmitter unit and a side view of branch 610A of the receiver unit. Diagram <NUM> also includes core waveguide <NUM> and core waveguide <NUM> coupled together via core waveguide <NUM>. In some examples as shown in diagram <NUM>, diameter D2 of core waveguide <NUM> of the receiver unit is smaller than diameter D1 of core waveguide <NUM> of the transmitter unit. Consequently, core waveguide <NUM> of the receiver unit may have a higher cutoff frequency for waveguide propagation modes compared to the cutoff frequency of core waveguide <NUM> of the transmitter unit. In some examples, diameter D1 of core waveguide <NUM> is reduced through core waveguide <NUM> to match diameter D2 of core waveguide <NUM> in one or more steps, e.g., in one step. In some examples, the transmitter unit has length L1, the receiver unit has length L2, and the transmitter unit and the receiver unit are separated by length L3.

In some examples, dimensions of waveguide feed network <NUM> depends on a frequency of operation of waveguide feed network <NUM>. In some examples, transmitting and receiving frequencies are selected in C band. In some examples, a transmitting frequency is in a range F1 = <NUM> to F2 = <NUM> and a receiving frequency is in a range F3 = <NUM> to F4 = <NUM>. In some examples, D1 is selected in a first range between <NUM> inches and <NUM> inches, e.g., D1 is selected at <NUM> inches. By selecting D1 in the first range, the cutoff frequency for TE21 mode in core waveguide <NUM> stays between <NUM> and <NUM>. Thus, the higher frequency F4 is sufficiently, e.g., by at least <NUM> percent below the lower cutoff frequency. Thus, TE21 mode may not propagate in the core waveguide <NUM> of waveguide feed network <NUM> in the transmitting frequency range of F1 to F2 or receiving frequency range of F3 to F4. D2 being smaller than D1, TE21 mode may not also propagate in the core waveguide <NUM> in the transmitting frequency range of F1 to F2 or receiving frequency range of F3 to F4.

The cutoff frequency for TE11 mode in core waveguide <NUM>, having diameter D1 in the first range, may be between <NUM> and <NUM>. Thus, the transmitting frequencies in the transmitting frequency range of F1 = <NUM> to F2 = <NUM> may propagate from the transmitter unit <NUM> via TE11 mode in the core waveguide <NUM>. The lower frequency F1 is at least above the higher cutoff frequency of <NUM> by more than <NUM> percent. In some examples, L1 is selected between <NUM> inches and <NUM> inches, e.g., <NUM> inches, such that no TE20 or TE30 modes can propagate in rectangular waveguides of waveguide reject filters 312A and 312B. By selecting L1 between <NUM> inches and <NUM> inches, TE10 mode is sufficiently out of a cutoff frequency in the rectangular waveguides of transmitter unit <NUM> and thus may propagate through transmitter unit <NUM> to core waveguide <NUM>. In some examples, D2 is selected between <NUM> inches and <NUM> inches, e.g., <NUM> inches, such that in core waveguides <NUM> and <NUM> the TE11 mode is sufficiently in cutoff for F2 and clearly for F1. D2 is selected such that F3 and clearly F4 are sufficiently out of cutoff for TE11 mode in core waveguides <NUM> and <NUM>. In some examples, L3 is selected longer than <NUM> inches, e.g., <NUM> inches, such that a greater that <NUM> dB suppression may be obtained for TM01 mode in the core waveguide between the transmitter unit and receiver unit.

<FIG> illustrates an image of an example waveguide feed network, according to some aspects of the disclosure. Returning back to <FIG>, image <NUM> of <FIG> shows an example manufactured body of waveguide feed network <NUM>. Image <NUM> shows outer body <NUM> of core waveguide <NUM>, second lower portion <NUM>, first lower portion <NUM>, and third lower portion <NUM>. Image <NUM> also shows input ports <NUM> and <NUM> as well as output port <NUM> and <NUM>. In some examples as shown, the transmitter unit and the receiver unit are not at a same side of waveguide feed network <NUM> and may even be at the opposite sides. In some examples as shown, input ports <NUM> and <NUM> as well as output port <NUM> and <NUM> are at opposite sides of waveguide feed network <NUM> and the openings to the output ports and input ports may have different orientations.

<FIG> illustrates an image of an example waveguide feed network, according to some aspects of the disclosure. Returning to <FIG>, image <NUM> of <FIG> shows an example manufactured body of waveguide feed network <NUM>. Image <NUM> shows outer body <NUM> of core waveguide <NUM>, second lower portion <NUM>, first lower portion <NUM>, and third lower portion <NUM>. Image <NUM> also shows output port <NUM> and <NUM>. Input ports <NUM> and <NUM> are respectively coupled through waveguides <NUM> and <NUM> to transmitter circuits (not shown) such the input signal may be connected through connection <NUM>.

In some examples and referring back to <FIG> and <FIG>, a plurality of transmitter units <NUM> may be included in waveguide feed network <NUM>. The plurality of transmitter units <NUM> may be coupled to core waveguide <NUM> and may operate at a plurality of first distinct transmitting frequencies. Also, a plurality of receiver units may be included in waveguide feed network <NUM>. The plurality of receiver units <NUM> may be coupled to core waveguide <NUM> and may operate at a plurality of second distinct receiving frequencies different from and greater that the plurality of first distinct transmitting frequencies.

In some examples and returning back to <FIG>, core waveguide <NUM> is designed to suppress a propagation of TE21 in the core waveguide. A diameter of the core waveguide is reduced from the transmitter unit to the receiver unit to suppress transmitting frequencies of the transmitter unit in TE11 mode from reaching the receiver. Reduced diameter D2 of core waveguide <NUM> at the receiver unit <NUM> and length L3 of core waveguide <NUM> between transmitter unit <NUM> and receiver unit <NUM> may also prevents the TM01 mode from reaching the receiver unit. In some examples, at highest receiving frequency in the range of F3 to F4, TM01 mode is reduced in the core waveguide by more than <NUM> dB to prevent disrupting an antenna pattern.

<FIG> illustrates a flow diagram of an example method of operation of a waveguide feed network, according to some aspects of the disclosure. Notably, one or more steps of method <NUM> described herein may be omitted, performed in a different sequence, and/or combined with other methods for various types of applications contemplated herein. Method <NUM> can be performed to operate transmitter unit <NUM> of <FIG>. As shown in <FIG>, transmitter unit <NUM> may be coupled between two input ports <NUM> and <NUM> and core waveguide <NUM> and may receive linearly polarized input signals from the input ports. Transmitter unit <NUM> may generate circularly polarized signal in core waveguide <NUM>.

As show in <FIG>, at step <NUM>, a transmitter unit receives a first linearly polarized signal by an input port. In some examples as shown in <FIG>, the transmitter unit includes two branches each having an input port. In some examples, the transmitter unit receives the first linearly polarized signal from input port <NUM> of first branch 310B.

At step <NUM>, a portion of the first linearly polarized signal is transmitted via a first waveguide reject filter to a circular waveguide. In some examples, a first half of the first linearly polarized signal is transmitted to the circular waveguide. In some examples, the portion of the first linearly polarized signal is transmitted through first waveguide reject filter 312B of first branch 310B to core waveguide <NUM> that may be a circular waveguide. In some examples, first waveguide reject filter 312B is part of integrated branch line coupler <NUM> that is located in first branch 310B. In some examples, as shown in <FIG>, one or more transformers 306B and 306D are coupled between input port <NUM> and first waveguide reject filter 312B to provide a change of wavelength for matching. In some examples an evanescent waveguide, e.g., evanescent waveguide 304B of <FIG>, couples first waveguide reject filter 312B to core waveguide <NUM>.

At step <NUM>, a second linearly polarized signal is generated by providing a quarter wavelength phase shift to a remaining portion of the first linearly polarized signal. In some examples, the a quarter wavelength phase shift is provided by a transmission of the remaining portion of the first linearly polarized signal to second branch 310A through couplers 314A, 314B, and 314C of integrated branch line coupler <NUM>. Couplers 314A, 314B, and 314C are inwardly coupled between first waveguide reject filter 312B and second waveguide reject filter 312A. In some examples, a second half of the first linearly polarized signal that is transmitted to second waveguide reject filter 312A receives <NUM> degrees phase shift.

At step <NUM>, the second linearly polarized signal is transmitted via a second waveguide reject filter to a circular waveguide. In some examples, the second linearly polarized signal is generated from the second half of the first linearly polarized signal. The second half of the first linearly polarized signal is transmitted through couplers 314A, 314B, and 314C of integrated branch line coupler <NUM> and receives <NUM> degrees phase shift. In some examples, as shown in <FIG>, the second linearly polarized signal is transmitted through second waveguide reject filter 312A of second branch 310A to core waveguide <NUM>. In some examples, second waveguide reject filter 312A is part of integrated branch line coupler <NUM> that is located in second branch 310A. In some examples, an evanescent waveguide, e.g., evanescent waveguide 304A of <FIG>, couples second waveguide reject filter 312A to core waveguide <NUM>.

At step <NUM>, the portion of the first linearly polarized signal and the second linearly polarized signal are combined to generate a circularly polarized signal in the circular waveguide. As shown in <FIG>, first branch 310B and second branch 310A are coupled to core waveguide <NUM> via evanescent waveguides 304A and 304B at separate predefined locations of core waveguide <NUM> to generate the circularly polarized signal in core waveguide <NUM>. In some examples, when the first linearly polarized signal is received through input port <NUM>, a right hand circularly polarized signal is generated in core waveguide <NUM> and additionally input port <NUM> is isolated by better than <NUM> dB. In some examples, when the first linearly polarized signal is received through input port <NUM>, a left hand circularly polarized signal is generated in core waveguide <NUM> and additionally input port <NUM> is isolated by better than <NUM> dB.

The description of the subject technology is provided to enable any person skilled in the art to practice the various aspects described herein. While the subject technology has been particularly described with reference to the various figures and aspects, it should be understood that these are for illustration purposes only.

Claim 1:
A feed network (<NUM>) comprising:
a first transmitter unit (<NUM>) that comprises:
a first branch (310B) having a first input port (<NUM>) and a second branch (310A) having a second input port (<NUM>);
a first integrated branch line coupler (<NUM>) coupling the first branch (<NUM>10B) and the second branch (310A), the first integrated branch line coupler (<NUM>) comprising:
a first waveguide reject filter (312B) in the first branch (310B) comprising a first end and a second end and an outer face and an inner face, wherein the first end of the first waveguide reject filter (312B) is coupled to the first input port (<NUM>);
a second waveguide reject filter (312A) in the second branch (310A) comprising a first end and a second end and an outer face and an inner face, wherein the first end of the second waveguide reject filter (312A) is coupled to the second input port (<NUM>);
a first group of one or more couplers (314A, 314B, 314C) coupled between the inner face of the first waveguide reject filter (312B) and the inner face of the second waveguide reject filter (312A); and
a first group of one or more single-sided stubs (302B, 302D, 302F) protruding outwardly from the outer face of the first waveguide reject filter (312B) and a second group of one or more single-sided stubs (302A, 302C, 302E) protruding outwardly from the outer face of the second waveguide reject filter (312A); and
a core waveguide (<NUM>) coupled to the first branch (<NUM>10B) via the second end of the first waveguide reject filter (312B) and to the second branch (310A) via the second end of the second waveguide reject filter (312A);
wherein the first group of one or more couplers (314A, 314B, 314C) are coupled inwardly between locations of the first and second groups of one or more single-sided stubs (302A, 302B, 302C, 302D, 302E, 302F), and
wherein the first transmitter unit (<NUM>) is configured to receive a linearly polarized signal from one of the first input port (<NUM>) or the second input port (<NUM>) and to generate a circularly polarized signal in the core waveguide (<NUM>).