T-shaped offset circuit and calibration board for base station antenna

Abstract

A T-shaped bias circuit and a calibration board for a base station antenna are disclosed. One of the T-shaped bias circuits includes: a synthesis path configured to transmit a synthesis signal via the synthesis path, the synthesis signal including a combination of a radio frequency signal and a direct current signal; a radio frequency path configured to transmit the radio frequency signal included in the synthesis signal via the radio frequency path; a direct current path configured to transmit the direct current signal included in the synthesis signal via the direct current path; and an impedance transformer connected between a first end of the synthesis path, a first end of the radio frequency path, and a first end of the direct current path, and configured to cause the reflection coefficient of the radio frequency signal transmitted between the synthesis path and the radio frequency path to have a resonance mode at at least two frequencies in the operating radio frequency band.

Description

Technical Field

[0001] The present disclosure relates to the field of radio frequency communication, and particularly to a T-type bias (Bias-Tee) circuit for this field. Background Art

[0002] Base station antennas using beamforming can improve the channel reuse rate and base station coverage area of a mobile communication system, and overcome increasingly serious interference problems such as co-channel interference and multipath fading. When using a beamforming antenna, the antenna array must be calibrated to ensure that the phase relationship between different RF paths is known and can be calculated during beamforming operations. The operating frequency band of beamforming antennas is also increasing day by day, so technologies suitable for calibrating broadband beamforming antennas are required.

[0003] A T-type bias (Bias-Tee) circuit is often used inside a base station antenna to allow low-frequency AISG signals and / or DC power signals to be transmitted to the antenna via the same coaxial cable used to transmit RF signals to the antenna, thereby reducing the number of cables and the load on the antenna tower. Summary of the Invention

[0004] One object of the present invention is to provide a new T-type bias circuit and a calibration board for a base station antenna including the T-type bias circuit.

[0005] According to a first aspect of the present invention, there is provided a T-shaped bias circuit, which includes: a synthesis path having a first end and a second end and configured to transmit a synthesis signal, the synthesis signal including a combination of a radio frequency signal and a direct current signal; a radio frequency path having a first end and a second end and configured to transmit the radio frequency signal included in the synthesis signal; a direct current path having a first end and a second end and configured to transmit the direct current signal included in the synthesis signal; and an impedance transformer connected between the first end of the synthesis path, the first end of the radio frequency path, and the first end of the direct current path, and configured to make the reflection coefficient of the radio frequency signal transmitted between the second end of the synthesis path and the second end of the radio frequency path have at least two resonance modes in the operating radio frequency band.

[0006] According to a second aspect of the present invention, there is provided a calibration board for a base station antenna, which includes: the T-shaped bias circuit as described above, a calibration port, a direct current bias port, and a power divider. The second end of the synthesis path in the T-shaped bias circuit is connected to the calibration port and configured to input a calibration signal as the synthesis signal, the second end of the radio frequency path is connected to the input end of the power divider and configured to output the radio frequency signal to the power divider, and the second end of the direct current path is connected to the direct current bias port and configured to output the direct current signal for driving RET.

[0007] According to a third aspect of the present invention, there is provided a T-shaped bias circuit, comprising: a DC port; an RF port; a synthesis port; and an impedance converter configured to transfer a DC signal received at the synthesis port to the DC port and substantially block the transfer of an RF signal received at the synthesis port to the DC port, and configured to transfer an RF signal received at the synthesis port to the RF port and substantially block the transfer of a DC signal received at the synthesis port to the RF port; wherein the impedance converter includes a closed loop connecting the synthesis port to both the DC port and the RF port.

[0008] Other features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings forming a part of the specification depict embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0010] With reference to the accompanying drawings, the present invention can be more clearly understood from the following detailed description, wherein:

[0011] Figure 1 is a simplified schematic diagram of a conventional T-shaped bias circuit;

[0012] Figure 2 is a schematic diagram of a T-shaped bias circuit according to some exemplary embodiments of the present invention;

[0013] Figure 3 is a more detailed schematic diagram of a T-shaped bias circuit according to some exemplary embodiments of the present invention;

[0014] Figure 4A is Figure 3 a planar schematic diagram of an exemplary implementation manner of the T-shaped bias circuit in

[0015] Figure 4B is for Figure 1 and Figure 4A a schematic diagram of a curve of the return loss of the T-shaped bias circuit in

[0016] Figures 5 - 7 is a schematic diagram of other structures of a T-shaped bias circuit according to multiple embodiments of the present invention;

[0017] Figure 8 is a schematic diagram of a specific structure of a calibration board for a base station antenna according to an exemplary embodiment of the present invention.

[0018] Note that in the embodiments described below, the same reference numerals are sometimes used among different drawings to denote the same or functionally identical parts, and their repeated description is omitted. In some cases, similar reference numerals and letters are used to denote similar items. Therefore, once an item is defined in one drawing, further discussion thereof in subsequent drawings is not necessary.

[0019] For ease of understanding, the positions, dimensions, ranges, etc. of the various structures shown in the drawings and the like sometimes do not represent the actual positions, dimensions, ranges, etc. Therefore, the present invention is not limited to the positions, dimensions, ranges, etc. disclosed in the drawings and the like. Detailed embodiments

[0020] The present invention will be described below with reference to the drawings, in which several embodiments of the present invention are shown. However, it should be understood that the present invention can be presented in many different ways and is not limited to the embodiments described below. In fact, the embodiments described below are intended to make the disclosure of the present invention more complete and to fully explain the scope of protection of the present invention to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide more additional embodiments.

[0021] It should be understood that the terms used herein are only for describing specific embodiments and are not intended to limit the present invention. All terms used herein (including technical terms and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. For the sake of brevity and / or clarity, well-known functions or structures may not be described in detail.

[0022] Figure 1 is a simplified schematic diagram of a conventional T-type bias circuit. As Figure 1 shown, the conventional T-type bias circuit includes three conductive paths commonly connected at point d, namely paths 1-3, which respectively transmit three signals, namely the composite signal (DC signal + RF signal) on path 1, the RF signal on path 2, and the DC signal on path 3. In some cases, at one end of path 1, namely Figure 1At point a in [the circuit], a DC + RF signal is input. Ideally, the RF signal in this composite signal is transmitted to point c without loss, and the DC signal therein is transmitted to point b without loss. However, the connection of path 3 has an impact on the transmission of the RF signal between points a and b. Therefore, some of the RF energy input at point a may be reflected back instead of being transmitted to point c. The echo loss between points a and b can be reduced or minimized by making the connection between point d and point b appear as an open circuit for the transmitted RF signal. In the case of implementing this T-type bias circuit using a microstrip transmission line on a printed circuit board (PCB), this can be achieved by setting the length of path 3 to λ / 4, where λ corresponds to the center frequency of the operating frequency band of the RF signal. This is because according to the calculation formula for the reflection coefficient from point a to point b, the reflection coefficient exhibits a resonant mode when the length of path 3 is λ / 4, that is, it has a local minimum, but the reflection coefficient remains low only within a very narrow range near the center frequency of the operating frequency band corresponding to this local extremum. Therefore, this T-type bias circuit exhibits good echo loss performance only over a relatively narrow frequency range.

[0023] As discussed previously, in Figure 1 the traditional T-type bias circuit shown, to ensure that there is no loss in the transmission of the RF signal between the two ends a and c, path 3 should be equivalent to an open circuit at the connection point b. Impedance transformation can be carried out by designing the length or impedance of path 3, so that path 3 appears as an open circuit at the connection point b, but this can only be achieved at a single frequency. In the frequency range near this frequency point, this traditional T-type bias circuit can also have good echo loss characteristics, but since the reflection coefficient of the RF signal between points a and c has only one resonant mode, the frequency range over which the echo loss is still small is relatively narrow. As a result, the traditional T-type bias circuit can only transmit the RF signal from point a to point c with low echo loss within a very narrow frequency band. However, in practice, a T-type bias circuit with a wider operating frequency band may be desired.

[0024] According to an embodiment of the present invention, it can be achieved by Figure 1An impedance transformer is added between three paths included in a conventional T-shaped bias circuit to expand the frequency range in which the upper T-shaped bias circuit exhibits low return loss. The impedance transformer can be designed to match the impedances of the three terminals, thereby introducing one or more new resonance modes, which broaden the operating frequency bandwidth of the T-shaped bias circuit (i.e., the bandwidth in which the upper T-shaped bias circuit provides acceptable return loss performance). The impedance transformer can be designed such that at and near two frequencies corresponding to the resonance modes, the DC path exhibits an open circuit (or approximately an open circuit) along two (or more) paths through which the RF signal passes, and due to the interaction of two relatively adjacent resonance modes, the reflection coefficient for the RF signal is also reduced within the frequency band between the two resonance frequency points. Therefore, the reflection coefficient for the RF signal is small at two resonance frequencies in the operating frequency band, and the reflection coefficient within the frequency band between the two resonance frequencies is also small. That is to say, the impedance transformer can make the reflection coefficient for the RF signal low within a certain frequency band, thereby expanding the operating frequency band of the RF signal. Of course, those skilled in the art can understand that the newly added impedance transformer can not only introduce two resonance modes, but also introduce more resonance modes as needed, thereby further expanding the operating frequency band and / or reducing the reflection coefficient within the frequency band.

[0025] Figure 2 is a schematic diagram of a T-shaped bias circuit according to some exemplary embodiments of the present invention.

[0026] As Figure 2 shown, the T-shaped bias circuit includes a synthesis path, a radio frequency path, and a DC path, and an impedance transformer 210 connected between these three paths. The synthesis path has a first end a1 and a second end a2, and is configured to transmit a synthesis signal, which is a synthesis signal of a radio frequency signal and a DC signal (DC + RF). The DC path has a first end b1 and a second end b2, and is configured to transmit the DC signal included in the synthesis signal. The radio frequency path has a first end c1 and a second end c2, and is configured to transmit the radio frequency signal included in the synthesis signal.

[0027] The impedance transformer 210 is connected between the first end a1 of the synthesis path, the first end b1 of the DC path, and the first end c1 of the radio frequency path, and is configured to make the reflection coefficient of the RF signal transmitted between the second end a2 of the synthesis path and the second end c2 of the radio frequency path have at least two resonance modes in the operating frequency band of the RF signal.

[0028] It should be noted that the present invention does not limit the direction of signal flow in the T-shaped bias circuit. The T-shaped bias circuit according to the present invention can either receive a combined signal at port a2 of the synthesis path and output DC and RF signals from the other two ports b2 and c2 respectively, or receive DC and RF signals at ports b2 and c2 respectively and output the combined signal DC+RF at port a2, or can also be designed to accommodate bidirectional signal flow. Therefore, the reflection coefficient of the RF signal transmitted between the second end a2 of the synthesis path and the second end c2 of the RF path can be determined by the flow direction of the RF signal. For example, when the RF signal flows from the synthesis path to the RF path, the reflection coefficient is the reflection coefficient of the RF signal from the input end a2 of the synthesis path to the output end c2 of the RF path, which has at least two resonance modes, i.e., local minima, in the operating frequency band. In some other embodiments, when the RF signal flows from the RF path to the synthesis path, the reflection coefficient is the reflection coefficient of the RF signal from the input end c2 of the RF path to the output end a2 of the synthesis path, which has at least two resonance modes, i.e., local minima, in the operating frequency band.

[0029] In some embodiments, the above operating frequency band can be the 2.3–2.7 GHz frequency band.

[0030] The present invention will be mainly described below by taking as an example a specific impedance transformer structure introducing two resonance modes. However, in view of the present disclosure, those skilled in the art can easily develop other impedance transformer structures including more than two resonance modes without creative labor, and those should also be included within the scope of the present invention.

[0031] Figure 3 is a more detailed schematic diagram of a T-shaped bias circuit according to some exemplary embodiments of the present invention.

[0032] As Figure 3 shown, the impedance transformer 310 includes first to third conductive wires 311-313, wherein the first conductive wire 311 is connected between the first end a1 of the synthesis path and the first end b1 of the DC path, the second conductive wire 312 is connected between the first end a1 of the synthesis path and the first end c1 of the RF path, and the third conductive wire 313 is connected between the first end c1 of the RF path and the first end b1 of the DC path.

[0033] Compared with Figure 1 the prior art structure of Figure 3The structure adds a bypass wire, creating an additional connection point between the DC path and the path through which the RF signal passes, and there are two parallel branches to each connection point. As a result of this design, the impedance transformer 310 has a closed-loop structure. The lack of uniqueness in impedance transformation using a single branch can be compensated by impedance compensation of the two parallel branches. For example, at a frequency within the desired operating frequency band, when the DC path exhibits inductive impedance at the connection point via one branch, the DC path can be made to exhibit capacitive impedance at the connection point via the other branch by adjusting various parameters (such as length) of the other branch. According to the principle of mutual compensation of capacitance and inductance in microwave circuits, the impedance transformer 310 can make the DC path appear open (or approximately open) at the connection point a1 at a certain frequency, and similarly appear open (or approximately open) at the connection point c1 at another frequency. In other words, the impedance transformer 310 can be configured to introduce two resonance modes in the desired RF frequency band, resulting in a small reflection coefficient over a wide frequency band between the two resonance frequencies. In some embodiments, to obtain a higher operating bandwidth, the impedance transformer 310 can include additional connected wires to introduce more branches to compensate for the impedance matching limitations of a single branch, as will be discussed in detail later in conjunction with Figures 5 - 7 As will be discussed in detail later in conjunction with

[0034] As Figure 3 shown, the first wire 311 forms the first branch connected between the combined path and the DC path, and the second wire 312 and the third wire 313 together form the second branch connected between the combined path and the DC path. These two branches can be designed such that the DC path exhibits capacitive impedance and inductive impedance at the first end a1 of the combined path via these two branches respectively. Either of the branches connecting the combined path and the DC path can exhibit capacitive impedance while the other branch can exhibit inductive impedance, as long as the capacitance and inductance impedances compensate each other such that the influence of the DC path at point a1 at the desired frequency point is as equivalent to an open circuit (i.e., causing resonance) as possible.

[0035] In addition, the third conductive line 313 forms a first branch connected between the DC path and the RF path, and the first conductive line 311 and the second conductive line 312 together form a second branch connected between the DC path and the RF path. These two branches can be arranged such that the DC path presents a capacitive impedance and an inductive impedance at the first end c1 of the RF path via these two branches respectively. Any one of the branches connecting the DC path and the RF path can present a capacitive impedance while the other branch can present an inductive impedance, as long as the capacitive and inductive impedances compensate each other so that the influence of the DC path at point c1 at the desired frequency point is as equivalent to an open circuit as possible.

[0036] The parameters of the three conductive lines 311 - 313 can be designed according to the actual application through various means such as theoretical formulas, experience, experiments, simulation software, etc.

[0037] Please note that Figure 3 the curves in

[0038] are only schematic and are not intended to limit or restrict the shape of each conductive line.

[0039] Figure 4A is implemented using a microstrip transmission line Figure 3 a planar schematic diagram of a specific example of the T - type bias circuit in

[0040] Although not shown in the drawings, those skilled in the art can understand that Figure 4A the microstrip transmission line in Figure 4A can also include an electrically insulating substrate and a conductive grounding member. Among them, the conductive grounding member is disposed on one side of the electrically insulating substrate, while Figure 4A the metal pattern shown in

[0041] Figure 4B compares Figure 1 the traditional T - type bias circuit (curve 401) of Figure 4AGraph of the return loss performance (unit: dB) of the T-type bias circuit (curve 402) according to an embodiment of the present invention. Curves 401 and 402 show the return loss of the RF signal from the synthesis path to the RF path obtained by simulation, which is merely exemplary and mainly used for visually comparing the curve shapes of the return losses of two different structures, rather than intending to show specific values. Those skilled in the art understand that the return loss RL = 20lg(Rho) dB here, where Rho is the magnitude of the reflection coefficient, so the curve of the return loss indicates the magnitude of the reflection coefficient.

[0042] From Figure 4B corresponding to Figure 1 in the prior art T-type bias circuit of curve 401, it can be seen that its return loss has only one resonance mode and has an appropriate value only in a narrow frequency band near the resonance frequency, so the operating frequency band is narrow. On the contrary, from curve 402 corresponding to the T-type bias circuit of the embodiment of the present invention, it can be seen that its return loss has a resonance mode near the frequencies of 2.3 GHz and 2.6 GHz, which is at a local minimum, and the curve between these two resonance frequencies presents a relatively flat depression. Therefore, the T-type bias circuit according to the embodiment of the present invention has a smaller reflection coefficient at least in the frequency band between these two resonance frequencies, thereby broadening the operating frequency band.

[0043] As mentioned above, in order to obtain a larger operating bandwidth, more branches can be introduced into the Figure 3 impedance converter.

[0044] In some embodiments, the impedance converter according to the present invention may further include a fourth conductive wire, wherein one end of the fourth conductive wire is connected to the first end of the DC path, and the other end is connected to the first end of the synthesis path or the first end of the RF path. In other embodiments, one end of the fourth conductive wire may be connected to the first end of the DC path, and the other end is connected to a non-end point on any one of the first to third conductive wires. In still other embodiments, the two ends of the fourth conductive wire may be respectively connected to non-end points on any two of the first to third conductive wires. Of course, those skilled in the art can understand that the present invention is not limited to the above structure, but more conductive wires can also be added to the impedance converter as needed.

[0045] Figures 5 - 7 are respectively Figure 3 schematic diagrams of some examples of the above variant structures of the T-type bias circuit.

[0046] As Figure 5 shown, a conductive wire 514 is added between the first end a1 of the synthesis path and the first end b1 of the DC path.

[0047] As Figure 6 shown, a conductive wire 614 is added between the first end b1 of the DC path and a non-endpoint on the second conductive wire 612. Thereby, the connection points between the DC path and the path through which the RF signal passes become three, and resonance modes can be introduced at three different frequencies, thereby further broadening the operating frequency band.

[0048] As Figure 7 shown, a conductive wire 714 is added between a non-endpoint on the first conductive wire 711 and a non-endpoint on the third conductive wire 713.

[0049] By designing Figures 5 - 7 parameters such as the shape, length, and position of the connection points of the conductive wires in

[0050] Note that the impedance converter according to the embodiments of the present invention is not limited to the types and structures discussed above, as long as the impedance converter can introduce at least two resonance modes within the operating frequency band.

[0051] It should be noted that although the T-shaped bias circuit mentioned in the background art is implemented on the calibration board for the base station antenna, the T-shaped bias circuit of the present invention can also be applied to other places within the antenna, such as on the feedback board or the phase shifter printed circuit board, or its own printed circuit board.

[0052] Figure 8 shows a scenario where a T-shaped bias circuit according to some exemplary embodiments of the present invention is implemented on the calibration board.

[0053] As Figure 8 shown, the calibration board for the base station antenna is a PCB board, which includes a T-shaped bias circuit, a calibration port, a DC bias port, a power splitter, and a plurality of couplers as shown in Figure 4A shown. Figure 8 The remotely electrical tilt (RET) unit shown in

[0054] In some embodiments, one end of the composite path in the T-shaped bias circuit can be connected to a calibration port, and a calibration signal can be input as the composite signal. One end of the RF path is connected to the input end of the power splitter, and the RF signal is output to the power splitter, and then the power splitter distributes the RF signal to each coupler. One end of the DC path is connected to the DC bias port, and a DC power signal is output to power the RET unit. Therefore, the DC signal and the RF signal can be input simultaneously through only one cable without interfering with each other, and the operating frequency band of the transmitted RF signal is extended according to the T-shaped bias circuit of the present invention.

[0055] Note that in this document, when an element is said to be "on", "attached" to, "connected" to, "coupled" to, or "in contact" with another element, etc., the element can be directly on, attached to, connected to, coupled to, or in contact with the other element, or there can be intervening elements. In contrast, when an element is said to be "directly" on, "directly attached" to, "directly connected" to, "directly coupled" to, or "directly in contact" with another element, there will be no intervening elements. In this document, a feature being arranged "adjacent" to another feature can mean that the feature has an overlapping portion with the adjacent feature or a portion above or below the adjacent feature.

[0056] In this document, elements or nodes or features that are "coupled" together may be mentioned. Unless otherwise explicitly stated, "coupled" means that one element / node / feature can be connected to another element / node / feature directly or indirectly mechanically, electrically, logically, or otherwise to allow interaction, even if the two features may not be directly connected. That is, "coupled" is intended to include both direct and indirect connections of elements or other features, including connections using one or more intermediate elements.

[0057] In this document, spatial relationship terms such as "above", "below", "left", "right", "front", "rear", "high", "low", etc. can illustrate the relationship between one feature and another feature in the drawings. It should be understood that the spatial relationship terms include different orientations of the device during use or operation in addition to the orientations shown in the drawings. For example, when the device in the drawing is inverted, a feature originally described as "below" other features can then be described as "above" the other features. The device can also be oriented in other ways (rotated 90 degrees or in other orientations), and the relative spatial relationship will be correspondingly interpreted at this time.

[0058] As used herein, the phrase "A or B" includes "A and B" as well as "A or B", and does not exclusively include only "A" or only "B" unless otherwise specifically stated.

[0059] As used herein, the term "exemplary" means "serving as an example, instance, or illustration", rather than as a "model" to be precisely replicated. Any implementation described herein by way of example is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, the present invention is not limited by any theory expressed or implied in the above technical field, background art, summary of the invention, or detailed description.

[0060] As used herein, the term "substantially" means including any minor variations caused by design or manufacturing defects, tolerances of devices or components, environmental effects, and / or other factors. The term "substantially" also allows for differences from a perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may exist in an actual implementation.

[0061] Additionally, for reference purposes only, terms such as "first", "second", etc. may also be used herein and are not intended to be limiting. For example, unless the context clearly indicates otherwise, the words "first", "second", and other such numerical words referring to structures or elements do not imply an order or sequence.

[0062] It should also be understood that when the term "comprising / including" is used herein, it indicates the presence of the stated features, wholes, steps, operations, units, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, units, and / or components and / or combinations thereof.

[0063] Additionally, embodiments of the present invention may also include the following examples:

[0064] 1. A T-shaped bias circuit, characterized by comprising:

[0065] A synthesis path having a first end and a second end and configured to transmit a synthesis signal, the synthesis signal including a combination of a radio frequency signal and a direct current signal,

[0066] A radio frequency path having a first end and a second end and configured to transmit the radio frequency signal included in the synthesis signal,

[0067] A direct current path having a first end and a second end and configured to transmit the direct current signal included in the synthesis signal, and

[0068] An impedance converter is connected between the first end of the synthesis path, the first end of the RF path, and the first end of the DC path, and is configured such that the reflection coefficient of the RF signal transmitted between the second end of the synthesis path and the second end of the RF path has at least two resonance modes in the operating RF frequency band.

[0069] 2. The T-shaped bias circuit according to 1, wherein the impedance converter includes first to third conductive wires, wherein the first conductive wire is connected between the first end of the synthesis path and the first end of the DC path, the second conductive wire is connected between the first end of the synthesis path and the first end of the RF path, and the third conductive wire is connected between the first end of the RF path and the first end of the DC path.

[0070] 3. The T-shaped bias circuit according to 2, wherein the first conductive wire forms a first branch connected between the synthesis path and the DC path,

[0071] The second conductive wire and the third conductive wire together form a second branch connected between the synthesis path and the DC path,

[0072] The first branch and the second branch are arranged such that the DC path presents one of an inductive impedance and a capacitive impedance at the first end of the synthesis path via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the synthesis path via the second branch.

[0073] 4. The T-shaped bias circuit according to 3, wherein the third conductive wire forms a first branch connected between the DC path and the RF path,

[0074] The first conductive wire and the second conductive wire together form a second branch connected between the DC path and the RF path,

[0075] The first branch and the second branch are arranged such that the DC path presents one of an inductive impedance and a capacitive impedance at the first end of the RF path via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the RF path via the second branch.

[0076] 5. The T-shaped bias circuit according to 2, wherein the impedance converter further includes a fourth conductive wire, wherein one end of the fourth conductive wire is connected to the first end of the DC path, and the other end is connected to the first end of the synthesis path or the first end of the RF path.

[0077] 6. The T-shaped bias circuit according to claim 2, wherein the impedance converter further includes a fourth conductive wire, one end of the fourth conductive wire being connected to the first end of the DC path and the other end being connected to a non-end point on any one of the first to third conductive wires.

[0078] 7. The T-shaped bias circuit according to claim 2, wherein the impedance converter further includes a fourth conductive wire, both ends of the fourth conductive wire being respectively connected to non-end points on any two of the first to third conductive wires.

[0079] 8. The T-shaped bias circuit according to claim 2, wherein the first to third conductive wires are all microstrip transmission lines or strip transmission lines.

[0080] 9. The T-shaped bias circuit according to claim 1, wherein the operating radio frequency band is 2.3 - 2.7 GHz.

[0081] 10. The T-shaped bias circuit according to claim 1, wherein the synthesis path is configured to input a synthesized signal from the second end of the synthesis path,

[0082] the radio frequency path is configured to output the radio frequency signal included in the synthesized signal from the second end of the radio frequency path,

[0083] the DC path is configured to output the DC signal included in the synthesized signal from the second end of the DC path, and

[0084] the impedance converter is configured such that the reflection coefficient of the radio frequency signal output from the radio frequency path has at least two resonance modes in the operating frequency band.

[0085] 11. The T-shaped bias circuit according to claim 1, wherein the radio frequency path is configured to input the radio frequency signal from the second end of the radio frequency path,

[0086] the DC path is configured to input the DC signal from the second end of the DC path,

[0087] the synthesis path is configured to output the synthesized signal obtained by synthesizing the radio frequency signal and the DC signal from the second end of the synthesis path, and

[0088] the impedance converter is configured such that the reflection coefficient of the radio frequency signal in the synthesized signal output from the synthesis path has at least two resonance modes in the operating frequency band.

[0089] 12. A calibration board for a base station antenna, comprising:

[0090] The T-shaped bias circuit according to any one of 1-11,

[0091] Calibration port,

[0092] DC bias port, and

[0093] Power divider,

[0094] wherein the second end of the synthesis path in the T-shaped bias circuit is connected to the calibration port and is configured to input a calibration signal as the synthesis signal,

[0095] The second end of the RF path is connected to the input end of the power divider and is configured to output the RF signal to the power divider,

[0096] The second end of the DC path is connected to the DC bias port and is configured to output the DC signal for driving the RET.

[0097] 13. A T-shaped bias circuit, characterized by comprising:

[0098] DC port;

[0099] RF port;

[0100] Synthesis port; and

[0101] An impedance converter configured to transfer the DC signal received at the synthesis port to the DC port and substantially block the RF signal received at the synthesis port from being transferred to the DC port, and configured to transfer the RF signal received at the synthesis port to the RF port and substantially block the DC signal received at the synthesis port from being transferred to the RF port,

[0102] wherein the impedance converter includes a closed loop connecting the synthesis port to both the DC port and the RF port.

[0103] 14. The T-shaped bias circuit according to 13, characterized by further comprising:

[0104] A synthesis path connecting the synthesis port to the closed loop;

[0105] An RF path connecting the RF port to the closed loop; and

[0106] A DC path connecting the DC port to the closed loop.

[0107] 15. The T-shaped biasing circuit according to claim 14, wherein the closed loop includes first to third conductive wires, wherein the first conductive wire is connected between the first intersection of the synthesis path and the closed loop and the second intersection of the DC path and the closed loop, the second conductive wire is connected between the first intersection of the synthesis path and the closed loop and the third intersection of the RF path and the closed loop, and the third conductive wire is connected between the second intersection of the DC path and the closed loop and the third intersection of the RF path and the closed loop.

[0108] 16. The T-shaped biasing circuit according to claim 15, wherein the first conductive wire includes a first branch of the closed loop, and the combination of the second and third conductive wires includes a second branch of the closed loop, and

[0109] wherein the first and second branches are arranged such that the DC path presents either an inductive impedance or a capacitive impedance at the first intersection of the synthesis path and the closed loop via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the synthesis path via the second branch.

[0110] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present invention. The embodiments disclosed herein can be combined arbitrarily without departing from the spirit and scope of the present invention. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A T-shaped bias circuit, characterized in that, comprising: a synthesis path having a first end and a second end and configured to transmit a synthesis signal, the synthesis signal including a combination of a radio frequency signal and a direct current signal, a radio frequency path having a first end and a second end and configured to transmit the radio frequency signal included in the synthesis signal, a direct current path having a first end and a second end and configured to transmit the direct current signal included in the synthesis signal, and an impedance transformer connected between the first end of the synthesis path, the first end of the radio frequency path, and the first end of the direct current path and configured to cause the reflection coefficient of the radio frequency signal transmitted between the second end of the synthesis path and the second end of the radio frequency path to have at least two resonance modes in an operating radio frequency band.

2. The T-shaped bias circuit according to claim 1, characterized in that, the impedance transformer includes first to third conductive wires, wherein the first conductive wire is connected between the first end of the synthesis path and the first end of the direct current path, the second conductive wire is connected between the first end of the synthesis path and the first end of the radio frequency path, and the third conductive wire is connected between the first end of the radio frequency path and the first end of the direct current path.

3. The T-shaped bias circuit according to claim 2, characterized in that, the first conductive wire forms a first branch connected between the synthesis path and the direct current path, the second conductive wire and the third conductive wire together form a second branch connected between the synthesis path and the direct current path, the first branch and the second branch are arranged such that the direct current path presents one of an inductive impedance and a capacitive impedance at the first end of the synthesis path via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the synthesis path via the second branch.

4. The T-shaped bias circuit according to claim 3, characterized in that, the third conductive wire forms a first branch connected between the direct current path and the radio frequency path, the first conductive wire and the second conductive wire together form a second branch connected between the direct current path and the radio frequency path, the first branch and the second branch are arranged such that the direct current path presents one of an inductive impedance and a capacitive impedance at the first end of the radio frequency path via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the radio frequency path via the second branch.

5. The T-shaped bias circuit according to claim 2, characterized in that, the impedance transformer further includes a fourth conductive wire, wherein one end of the fourth conductive wire is connected to the first end of the direct current path, and the other end is connected to the first end of the synthesis path or the first end of the radio frequency path.

6. The T-shaped bias circuit according to claim 2, characterized in that, the impedance transformer further includes a fourth conductive wire, wherein one end of the fourth conductive wire is connected to the first end of the direct current path, and the other end is connected to a non-end point on any one of the first to third conductive wires.

7. The T-shaped bias circuit according to claim 2, characterized in that, The impedance converter further includes a fourth conductive wire, wherein both ends of the fourth conductive wire are respectively connected to a non-end point on any two of the first to third conductive wires.

8. The T-shaped bias circuit according to claim 2, wherein, the first to third conductive wires are all microstrip transmission lines or strip transmission lines.

9. The T-shaped bias circuit according to claim 1, wherein, the operating radio frequency band is 2.3 - 2.7 GHz.

10. The T-shaped bias circuit according to claim 1, wherein, the synthesis path is configured to input a synthesized signal from the second end of the synthesis path, the radio frequency path is configured to output the radio frequency signal included in the synthesized signal from the second end of the radio frequency path, the DC path is configured to output the DC signal included in the synthesized signal from the second end of the DC path, and the impedance converter is configured to make the reflection coefficient of the radio frequency signal output from the radio frequency path have at least two resonance modes in the operating frequency band.

11. The T-shaped bias circuit according to claim 1, wherein, the radio frequency path is configured to input the radio frequency signal from the second end of the radio frequency path, the DC path is configured to input the DC signal from the second end of the DC path, the synthesis path is configured to output the synthesized signal obtained by synthesizing the radio frequency signal and the DC signal from the second end of the synthesis path, and the impedance converter is configured to make the reflection coefficient of the radio frequency signal in the synthesized signal output from the synthesis path have at least two resonance modes in the operating frequency band.

12. A calibration board for a base station antenna, wherein, comprising: the T-shaped bias circuit according to any one of claims 1 - 11, a calibration port, a DC bias port, and a power splitter, wherein the second end of the synthesis path in the T-shaped bias circuit is connected to the calibration port and is configured to input a calibration signal as the synthesized signal, the second end of the radio frequency path is connected to the input end of the power splitter and is configured to output the radio frequency signal to the power splitter, the second end of the DC path is connected to the DC bias port and is configured to output the DC signal for driving the RET.

13. A T-shaped bias circuit, wherein, comprising: a DC port; a radio frequency port; a synthesis port; and an impedance converter configured to transfer the DC signal entering the circuit at the synthesis port to the DC port and substantially block the transfer of the radio frequency signal entering the circuit at the synthesis port to the DC port, and configured to transfer the radio frequency signal entering the circuit at the synthesis port to the radio frequency port and substantially block the transfer of the DC signal entering the circuit at the synthesis port to the radio frequency port, wherein the impedance converter includes a closed loop connecting the synthesis port to both the DC port and the radio frequency port.

14. The T-shaped bias circuit according to claim 13, wherein, further comprising: a synthesis path connecting the synthesis port to the closed loop; A radio frequency path connecting a radio frequency port to a closed loop; and A DC path connecting a DC port to the closed loop.

15. The T-shaped bias circuit according to claim 14, wherein, the closed loop includes first to third conductive wires, wherein the first conductive wire is connected between a first intersection of the synthesis path and the closed loop and a second intersection of the DC path and the closed loop, the second conductive wire is connected between the first intersection of the synthesis path and the closed loop and a third intersection of the radio frequency path and the closed loop, and the third conductive wire is connected between the second intersection of the DC path and the closed loop and the third intersection of the radio frequency path and the closed loop.

16. The T-shaped bias circuit according to claim 15, wherein, the first conductive wire includes a first branch of the closed loop, and the combination of the second and third conductive wires includes a second branch of the closed loop, and wherein the first and second branches are arranged such that the DC path presents either an inductive impedance or a capacitive impedance at the first intersection of the synthesis path and the closed loop via the first branch, and presents the other of the inductive impedance and the capacitive impedance at the first end of the synthesis path via the second branch.

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