CN212381205U - Communication terminal - Google Patents

Abstract

The application discloses a communication terminal, which comprises a transmission line and a filtering branch coupled with the transmission line, wherein the filtering branch comprises a first sub-branch, a second sub-branch and an adjustable capacitor, and two ends of the adjustable capacitor are respectively connected with the first sub-branch and the second sub-branch; the filtering branch knot can realize filtering, and the filtering frequency is related to the capacitance value of the adjustable capacitor. By means of the method, the filtering frequency of the communication terminal can be adjusted.

Description

Communication terminal

Technical Field

The utility model relates to a wireless communication technology field especially relates to a communication terminal.

Background

Spurious interference is interference caused by spurious emissions outside the transmission frequency band of one system falling into the reception frequency band of another system. The spurious interference directly affects the receive sensitivity of the system. In communication products, the application frequency of the nonlinear device is extremely high, and the spurious is a parasitic product which cannot be completely avoided. If the amplitude of the stray signal falling into a receiving frequency band of a certain system is high, the receiver system of the interfered system cannot filter the stray signal, and in order to prevent interference with other systems, some methods must be adopted to reduce the stray radiation of a transmitter.

The existing stray reduction method generally uses discrete elements to build a filter with a wider frequency band, and is matched with a switch in a switching way to realize stray filtering in different frequency bands.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the main technical problem who solves provides a communication terminal, can realize adjusting communication terminal's filtering frequency.

In order to solve the above technical problem, the utility model discloses a technical scheme provide a communication terminal, communication terminal includes: a transmission line; the filter branch is coupled to the transmission line and comprises a first sub branch, a second sub branch and an adjustable capacitor, wherein two ends of the adjustable capacitor are respectively connected with the first sub branch and the second sub branch; the filtering branch knot can realize filtering, and the filtering frequency is related to the capacitance value of the adjustable capacitor.

The filtering branches are U-shaped or semicircular.

The first sub-branch and the second sub-branch are L-shaped respectively, and the first sub-branch, the adjustable capacitor and the second sub-branch are connected to form the U-shaped filtering branch.

The communication terminal further comprises a microprocessor which is electrically connected to the control end of the adjustable capacitor and used for inputting a control signal for adjusting the capacitance value for the adjustable capacitor.

The communication terminal is provided with a plurality of channels with fixed frequency, and the microprocessor is used for adjusting the capacitance value of the adjustable capacitor so as to switch the filtering frequency to the frequency of the current channel.

The communication terminal is provided with a plurality of different working frequency bands, and the microprocessor is used for adjusting the capacitance value of the adjustable capacitor so as to switch the filtering frequency to the stray frequency corresponding to the current working frequency band.

The number of the filtering branches is two, and the two filtering branches are respectively arranged on two sides of the transmission line.

The shapes and the lengths of the two filtering branches are consistent, and the orientations of the two filtering branches are parallel to the length direction of the transmission line.

Wherein the orientation of the two filter branches is opposite.

The length of the filtering branch is one half wavelength of a filtering frequency point; and/or the first sub-branch and the second sub-branch are both strip-shaped metal sheets, and the adjustable capacitor is a variable capacitance diode; and/or the transmission line is a microstrip line, the communication terminal further comprises an antenna and a radio frequency circuit, and two ends of the transmission line are respectively connected with the antenna and the radio frequency circuit.

The utility model has the advantages that: unlike the case of the prior art, the communication terminal of the present application includes: a transmission line; the filter branch is coupled to the transmission line and comprises a first sub branch, a second sub branch and an adjustable capacitor, wherein two ends of the adjustable capacitor are respectively connected with the first sub branch and the second sub branch; the filtering branch can realize filtering, and the filtering frequency is related to the capacitance value of the adjustable capacitor. The filtering branches are coupled beside the transmission line, so that the transmitted signals can be filtered; and because the filtering branch comprises the first sub-branch, the second sub-branch and the adjustable capacitor, wherein two ends of the adjustable capacitor are respectively connected with the first sub-branch and the second sub-branch, and the filtering frequency is related to the capacitance value of the adjustable capacitor, the filtering frequency of the transmitted signal can be changed by changing the capacitance value of the adjustable capacitor, so that the filtering can be carried out in all working frequency bands of the communication terminal, and the stray emission of the communication terminal in the full working frequency band can meet the index requirement.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a communication terminal provided by the present invention;

fig. 2 is a schematic structural diagram of another embodiment of the communication terminal provided by the present invention;

fig. 3 is a schematic view of a partial structure of an application scenario of the communication terminal according to the present invention;

FIG. 4a is a schematic diagram of a simulation curve of a standing wave of the communication terminal when the tunable capacitor is not loaded on the filter branch in FIG. 3;

fig. 4b is a diagram of a simulation curve of the insertion loss of the communication terminal of fig. 4 a;

FIG. 5a is a schematic diagram of a simulation curve of standing waves of the communication terminal under different capacitance values when the adjustable capacitor is loaded on the filter stub in FIG. 3;

fig. 5b is a diagram illustrating a simulation curve of the insertion loss of the communication terminal of fig. 5a under different capacitance values.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work all belong to the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a communication terminal according to the present invention. The communication terminal in this embodiment includes a transmission line 10 and a filtering branch 12 coupled to the transmission line 10, where the filtering branch 12 includes a first sub-branch 121, a second sub-branch 122, and an adjustable capacitor 123, where two ends of the adjustable capacitor 123 are respectively connected to the first sub-branch 121 and the second sub-branch 122; the filter stub 12 can implement filtering, and the filtering frequency is related to the capacitance value of the tunable capacitor 123. The communication terminal can be an electronic device with a communication function, such as an interphone, a mobile phone, a tablet computer and a desktop computer.

The filtering branch 12 is coupled beside the transmission line 10, so that the transmitted signals can be filtered; and because the filtering branch 12 includes the first sub-branch 121, the second sub-branch 122 and the adjustable capacitor 123, wherein two ends of the adjustable capacitor 123 are respectively connected to the first sub-branch 121 and the second sub-branch 122, and the filtering frequency is related to the capacitance value of the adjustable capacitor 123, the filtering frequency of the filtering branch 12 to the transmitted signal can be changed by changing the capacitance value of the adjustable capacitor 123, so that filtering can be performed in all working frequency bands of the communication terminal, and the stray emission of the communication terminal in the full working frequency band can meet the index requirement.

Further, the shape of the filter stub 12 is U-shaped or semicircular. It will be appreciated that a fixed length of the filter stub 12 can filter a fixed frequency signal, and thus the filter frequency can be adjusted by changing the length of the filter stub 12; in practical applications, the filter branches 12 may be set to have different shapes, so that the filter branches 12 have different lengths, for example, the shape of the filter branches 12 is U-shaped or semicircular, but may also be other shapes. As the current communication terminal tends to be miniaturized and portable, the space for accommodating the filter stub 12 becomes smaller and smaller, and under such a condition, the overall size of the filter stub 12 is adjustable or various shapes are designed, which is necessary.

Further, when the shape of the filter branch 12 is U-shaped, the first sub-branch 121 and the second sub-branch 122 are L-shaped, and the first sub-branch 121, the adjustable capacitor 123 and the second sub-branch 122 are connected to form the U-shaped filter branch 12. Specifically, each of the first sub-branch 121 and the second sub-branch 122 has a long side branch and a short side branch, the long side branch and the short side branch form an L shape, and two ends of the adjustable capacitor 123 are respectively connected to the short side branches of the first sub-branch 121 and the second sub-branch 122, so that the long side of the first sub-branch 121, the short side of the first sub-branch 121, the adjustable capacitor 123, the short side of the second sub-branch 122, and the long side of the second sub-branch 122 are sequentially connected to form the U-shaped filter branch 12.

As an implementation manner, the first sub-branch 121 and the second sub-branch 122 are both strip-shaped metal sheets, and the adjustable capacitor 123 is a varactor. In the use process of the communication terminal, the filtering frequency of the filtering branch 12 to the transmitted signal can be changed by properly adjusting the capacitance value of the varactor diode.

Please refer to fig. 2, fig. 2 is a schematic structural diagram of another embodiment of the communication terminal according to the present invention. In this embodiment, the communication terminal further includes a microprocessor 14, and the microprocessor 14 is electrically connected to the control end of the adjustable capacitor 123 and is configured to input a control signal for adjusting the capacitance value to the adjustable capacitor 123. It can be understood that, in the existing communication terminal, for example, an intercom, a low-pass filter is usually designed at the front end of the antenna to suppress the spurious outside the transmission frequency band, but this method cannot filter the spurious within the transmission frequency band, and the flatness in the pass band has a large influence on the transmission power and efficiency, and is difficult to balance; in this embodiment, the microprocessor 14(MCU) is electrically connected to the control terminal of the adjustable capacitor 123, and the capacitance of the adjustable capacitor 123 is adjusted by changing the pin output voltage of the MCU, so that the filtering frequency of the filtering branch 12 can be adjusted, and for a fixed stray point in the frequency band, the filtering frequency can be controlled to a stray point that needs to be suppressed.

In addition, the microprocessor 14 is connected to the control end of the adjustable capacitor 123, so that the filtering frequency can be automatically controlled, that is, the MCU automatically outputs a corresponding control voltage according to the current transmission frequency of the communication terminal, and adjusts the adjustable capacitor 123 to a corresponding capacitance value, thereby realizing filtering at a corresponding frequency. In one embodiment, the communication terminal has a plurality of channels with fixed frequencies, and the microprocessor 14 is configured to adjust the capacitance of the adjustable capacitor 123 to switch the filtering frequency to the frequency of the current channel. For example, when the communication terminal is an interphone with fixed frequency of each channel, the spur suppression can be automatically controlled by identifying the channel, that is, different fixed corresponding voltages can be written in the control program for different channels CH1/CH2/CH3, and when the communication terminal switches the channel, the voltage can be controlled to switch to the corresponding voltage, so that the filtering frequency is switched to the frequency of the current channel, and the spur suppression of the current channel can be automatically realized. In another embodiment, the communication terminal has a plurality of different operating frequency bands, and the microprocessor 14 is configured to adjust the capacitance of the adjustable capacitor 123, so that the filtering frequency is switched to the spurious frequency corresponding to the current operating frequency band. For another example, the operating frequency band of the communication terminal is subdivided into bands B1 and B2 … … B10, and different voltage output values V1 and V2 … … V10 are written for different bands in the control program, and when the current operating frequency band of the communication terminal is switched from B1 to B3, the voltage output value is switched from V1 to V3, so that the filtering frequency is switched to the spurious frequency corresponding to the current operating frequency band, thereby automatically suppressing the spurious of the current transmission frequency.

In one embodiment, the number of the filter branches 12 is two, and the two filter branches 12 are respectively disposed on two sides of the transmission line 10. In this embodiment, by designing the two filtering branches 12, the filtering frequency width of the filtering branches 12 can be increased; and through setting up two filtering branches 12 in the both sides of transmission line 10, can adapt to the space size of transmission line 10 both sides in a flexible way, can not appear setting up in one side and appear having big space occupation demand to transmission line 10 one side.

Further, the two filter branches 12 have the same shape and length, and the two filter branches 12 are both oriented parallel to the length direction of the transmission line 10. By arranging the orientation of the filter stub 12 parallel to the length direction of the transmission line 10, the filter stub 12 can be adapted to the arrangement of the transmission line 10 and other lines in the communication terminal.

In one embodiment, the two filter stubs 12 are oriented oppositely. In other embodiments, the orientation of the two filter branches 12 may also be the same.

In addition, the length of the filtering branch 12 is half the wavelength of the filtering frequency point, so that the design size of the filtering branch 12 can be greatly reduced, a notch at the filtering frequency point is formed, and the effect of suppressing stray is better.

As an embodiment, the transmission line 10 is a microstrip line; the communication terminal further comprises an antenna 16 and radio frequency circuitry 18; the transmission line 10 is connected at both ends to an antenna 16 and a radio frequency circuit 18, respectively. For example, the radio frequency signal output by the radio frequency circuit 18 is output to the antenna 16 (or to the antenna 16 through the low pass filter LPF) through the microstrip line of 50 Ω, and by loading the coupled filter stub 12 beside the microstrip line, since the adjustable capacitor 123 is loaded on the filter stub 12, the filter frequency can be changed by changing the capacitance value of the adjustable capacitor 123, and the control voltage of the adjustable capacitor 123 is provided by the microprocessor 14, so that the microprocessor 14 can adjust the control voltage of the adjustable capacitor 123, and the capacitance value can be changed by controlling the voltage, and the filter frequency can be changed along with the change of the capacitance value.

Please refer to fig. 3, fig. 3 is a schematic diagram of a partial structure of an application scenario of a communication terminal according to the present invention. Arranging a transmission line 10 and filter branches 12 on a dielectric slab 11, wherein the width of the dielectric slab 11 is 20mm, the dielectric slab 11 adopts an FR-4 epoxy fiberglass cloth substrate, the thickness of the dielectric slab is set to be 0.5mm, the coupled filter branches 12 adopt a U-shaped structure, the orientation of the filter branches 12 is parallel to the length direction of the transmission line 10, the size of the filter branches 12 in the length direction of the transmission line 10 is 47.5mm, and the total length of the single filter branches 12 is about one-half wavelength of a notch frequency point; then, an adjustable capacitor 123 such as a varactor diode is loaded on the filter branch 12 with a fixed length, for example, the filter branch 12 is directly cut into two sections, and the two sections are connected by the adjustable capacitor 123, so that the electric tuning of the filter branch 12 can be performed by changing the capacitance value of the adjustable capacitor 123, thereby changing the notch frequency of the communication terminal.

In order to verify that the notch frequency range and the spurious suppression effect of the communication terminal meet the design requirements, simulation tests are performed on the communication terminal when the adjustable capacitor 123 is not loaded on the filter branch 12 and the communication terminal when the adjustable capacitor 123 is loaded on the filter branch 12, and the test results are shown in fig. 4a to 5 b. Fig. 4a and 4b are simulation diagrams of the communication terminal when the tunable capacitor 123 is not loaded on the filter branch 12, where fig. 4a is a simulation curve diagram of a standing wave of the communication terminal when the tunable capacitor 123 is not loaded on the filter branch 12 in fig. 3, and fig. 4b is a simulation curve diagram of an insertion loss (S21) of the communication terminal in fig. 4 a. It can be found that, when the filter branch 12 is not loaded with a capacitor, taking the stray point 860MHz as an example, the following information is obtained by performing simulation on the communication terminal of fig. 3: within 0.4-0.47GHz, the standing wave is about 1.33, the insertion loss is less than 0.2dB, and at 860MHz, the standing wave is 3.23, and the insertion loss is 14 dB. Therefore, the trap effect of a single frequency point can be realized by coupling the filter branches 12 beside the transmission line 10. Fig. 5a and 5b are simulation diagrams of the communication terminal when the tunable capacitor 123 is loaded on the filter branch 12, where fig. 5a is a simulation curve diagram of standing waves of the communication terminal under different capacitance values when the tunable capacitor 123 is loaded on the filter branch 12 in fig. 3, and fig. 5b is a simulation curve diagram of insertion loss of the communication terminal of fig. 5a under different capacitance values. L1, L2, L3 shown in fig. 5a are standing wave curves for a tunable capacitor 123 with capacitance values of 37, 19, 10pF, respectively, while L4, L5, L6 shown in fig. 5b are insertion loss (S21) curves for a tunable capacitor 123 with capacitance values of 37, 19, 10pF, respectively, it can be seen that when the filter stub 12 is loaded with a capacitor, it can be obtained: when the capacitance is 37, 19, 10pF, the corresponding trap frequency points are 860, 900, 940MHz, and when 400 plus 470MHz, the insertion loss is less than 0.2dB, the standing wave is about 1.3, at the trap frequency point, the insertion loss is more than 7dB, and the standing wave is more than 3.2. Therefore, the adjustable capacitor 123 is loaded on the filter branch 12, so that the movement of the notch frequency point can be realized.

In the application, the filtering branch 12 is coupled beside the transmission line 10, so that the trap of a single frequency point can be performed on the transmitted signal, and the filtering effect is achieved; the filtering branch 12 comprises a first sub-branch 121, a second sub-branch 122 and an adjustable capacitor 123, wherein two ends of the adjustable capacitor 123 are respectively connected with the first sub-branch 121 and the second sub-branch 122, and the filtering frequency is related to the capacitance value of the adjustable capacitor 123, so that the adjustable capacitor 123 is loaded on the filtering branch 12, and the capacitance value of the adjustable capacitor 123 is changed, thereby realizing the movement of a notch frequency point, namely changing the filtering frequency of a transmitted signal, further realizing the filtering in all working frequency bands of the communication terminal, and enabling the stray emission of the communication terminal in the full working frequency band to meet the index requirement; in addition, by adjusting the control voltage by the microprocessor 14 to adjust the capacitance value of the adjustable capacitor 123, the automatic control of the stray suppression of the communication terminal can be realized; the insertion loss of the system is less than 0.2dB, stray suppression (namely the insertion loss of a trapped wave frequency point) is more than 7dB, and the influence of the temperature is small.

In the several embodiments provided in the present invention, it should be understood that the disclosed communication terminal can be implemented in other manners. For example, the above-described embodiment of the communication terminal is only illustrative, and the division of each functional part is only one logical functional division, and there may be another division manner in actual implementation, for example, a plurality of functional parts may be combined or may be integrated into several modules, or each functional part may exist alone physically, and so on.

In the present application, the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless expressly limited otherwise. The terms "mounted," "connected," "fixed," and the like are to be construed broadly and include, for example, fixed connections, removable connections, or integral connections. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the description of the present invention, it should be understood that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or unit indicated must have a specific direction, be constructed and operated in a specific orientation, and therefore, should not be construed as limiting the present invention.

In the description herein, the terms "several embodiments," "one implementable embodiment," "detailed description," "implementation scenario," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example manner of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above only is the embodiment of the present invention, not limiting the patent scope of the present invention, all the equivalent structures or equivalent principle changes made by the contents of the specification and the drawings, or directly or indirectly applied to other related technical fields, are included in the patent protection scope of the present invention.

Claims (10)

1. A communication terminal, comprising:

a transmission line;

the filter branch is coupled to the transmission line and comprises a first sub branch, a second sub branch and an adjustable capacitor, wherein two ends of the adjustable capacitor are respectively connected with the first sub branch and the second sub branch; the filtering branch knot can realize filtering, and the filtering frequency is related to the capacitance value of the adjustable capacitor.

2. The communication terminal according to claim 1, wherein the filter stub has a U-shape or a semi-circular shape.

3. The communication terminal according to claim 2, wherein the first sub-branch and the second sub-branch are each L-shaped, and the first sub-branch, the adjustable capacitor and the second sub-branch are connected to form the U-shaped filter branch.

4. The communication terminal according to claim 1, further comprising a microprocessor electrically connected to the control terminal of the tunable capacitor for inputting a control signal for adjusting the capacitance value to the tunable capacitor.

5. The communication terminal according to claim 4,

the communication terminal is provided with a plurality of channels with fixed frequency, and the microprocessor is used for adjusting the capacitance value of the adjustable capacitor so as to switch the filtering frequency to the frequency of the current channel.

6. The communication terminal according to claim 4,

the communication terminal is provided with a plurality of different working frequency bands, and the microprocessor is used for adjusting the capacitance value of the adjustable capacitor so as to switch the filtering frequency to the stray frequency corresponding to the current working frequency band.

7. The communication terminal according to claim 1, wherein the number of the filter branches is two, and the two filter branches are respectively disposed on two sides of the transmission line.

8. The communication terminal of claim 7, wherein the two filter branches have the same shape and length, and the two filter branches are oriented parallel to the length direction of the transmission line.

9. The communication terminal according to claim 8, wherein the two filter branches are oriented oppositely.

10. The communication terminal of claim 1,

the length of the filtering branch is one half wavelength of the filtering frequency point; and/or the presence of a gas in the gas,

the first sub-branch and the second sub-branch are both strip-shaped metal sheets, and the adjustable capacitor is a variable capacitance diode; and/or the presence of a gas in the gas,

the transmission line is a microstrip line, the communication terminal further comprises an antenna and a radio frequency circuit, and two ends of the transmission line are respectively connected with the antenna and the radio frequency circuit.

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