CN219018787U

CN219018787U - Radio frequency matching circuit

Info

Publication number: CN219018787U
Application number: CN202223234374.9U
Authority: CN
Inventors: 周勇; 庄颖
Original assignee: Shenzhen Zhixin Microelectronics Co ltd
Current assignee: Shenzhen Zhixin Microelectronics Co ltd
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2023-05-12
Anticipated expiration: 2032-12-01

Abstract

The utility model provides a radio frequency matching circuit, which relates to the technical field of circuits, and comprises: the balun transformer comprises an unbalanced port and a balanced port, wherein the balanced port comprises an input end and an output end which are respectively grounded, and a center tap of the balanced port is grounded through an isolation circuit; the balun transformer further comprises a filter circuit connected to the unbalanced port of the balun transformer; the filter circuit comprises a wave stabilizing inductor and a filter module connected with the wave stabilizing inductor, wherein the filter module comprises two filter capacitors, one of the two filter capacitors and the wave stabilizing inductor are connected in parallel to the unbalanced port, and the other filter capacitor, the wave stabilizing inductor and the filter capacitor connected in parallel with the wave stabilizing inductor are connected in series and grounded. The utility model aims to solve the technical problems that the rejection capability of other frequency bands is improved by adding a filter after a balun transformer in the prior art, and the loss and the area are greatly increased.

Description

Radio frequency matching circuit

Technical Field

The utility model relates to the technical field of circuits, in particular to a radio frequency matching circuit.

Background

Impedance matching is often performed between a double-ended output radio frequency power amplifier and a single-ended antenna using balun transformers.

In the prior art, the technical scheme is based on the balun of GaAs process design, as shown in the attached figure 1. The balun transformer works at 3.3-4.2 GHz, an S21 curve of the balun transformer has a notch point at 7.4-7.5 GHz, but the balun transformer is poor in suppression capability at a low frequency end, and a filter is often required to be added behind the balun transformer to improve the suppression capability of other frequency bands, so that the loss and the area are greatly increased.

Disclosure of Invention

Based on the above, the utility model aims to provide a radio frequency matching circuit, which aims to solve the technical problems that the rejection capability of other frequency bands is improved by adding a filter after a balun transformer in the prior art, and the loss and the area are greatly increased.

In order to achieve the above object, the present utility model provides a radio frequency matching circuit, comprising:

the balun transformer comprises an unbalanced port and a balanced port, wherein the balanced port comprises an input end and an output end which are respectively grounded, and a center tap of the balanced port is grounded through an isolation circuit;

a filter circuit connected to the unbalanced port of the balun transformer;

the filter circuit comprises a wave stabilizing inductor and a filter module connected with the wave stabilizing inductor, wherein the filter module comprises two filter capacitors, one of the two filter capacitors and the wave stabilizing inductor are connected in parallel to the unbalanced port, and the other filter capacitor, the wave stabilizing inductor and the filter capacitor connected in parallel with the wave stabilizing inductor are connected in series and grounded.

According to an aspect of the above technical solution, an input end of the balancing port is grounded through a first filter capacitor, and an output end of the balancing port is grounded through a second filter capacitor.

According to an aspect of the foregoing technical solution, the input end of the balancing port is further connected in parallel to the first electrode terminal, and the output end of the balancing port is further connected in parallel to the second electrode terminal.

According to an aspect of the above technical solution, the center tap of the balanced port is connected in parallel to the unbalanced port and grounded.

According to an aspect of the foregoing technical solution, a third filter capacitor is further disposed at a front end of the center tap connected to the unbalanced port.

According to an aspect of the foregoing technical disclosure, the filtering module includes a fourth filtering capacitor and a fifth filtering capacitor, where the fourth filtering capacitor and the stabilizing inductor are arranged in parallel, and the fifth filtering capacitor is connected in series to the stabilizing inductor and the fourth filtering circuit which are arranged in parallel.

According to an aspect of the above-described technical solution, the unbalanced port is further connected in parallel to the third electrode terminal.

According to an aspect of the above technical solution, the layout area of the balun transformer is 660um x 800um.

Compared with the prior art, the radio frequency matching circuit shown in the embodiment is adopted, and has the beneficial effects that:

the input end, the output end and the center tap of the balance port of the balun transformer are respectively grounded, each port is provided with a corresponding filter capacitor to realize a filtering effect, the filter network is formed by arranging the steady wave inductor and the filter module at the unbalanced port of the balun transformer, the filter module comprises two filter capacitors, one of the filter capacitors is arranged in parallel with the steady wave inductor, the other filter capacitor is connected in series with the steady wave inductor and the filter capacitor which are arranged in parallel, and the filter network is grounded, so that the balun transformer has the dual functions of impedance transformation and filtering at the same time, the manufacturing cost is low, and the balun transformer can be popularized and manufactured in mass production.

Drawings

FIG. 1 is a schematic circuit diagram of a balun transformer in the prior art;

fig. 2 is a circuit diagram of a radio frequency matching circuit according to a first embodiment of the present utility model;

fig. 3 is a schematic diagram of a radio frequency matching circuit according to a first embodiment of the present utility model;

the following detailed description will further illustrate the utility model with reference to the above-described drawings.

Detailed Description

In order that the utility model may be readily understood, a more complete description of the utility model will be rendered by reference to the appended drawings. Several embodiments of the utility model are presented in the figures. This utility model may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "mounted" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this utility model belongs. The terminology used herein in the description of the utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

Example 1

As shown in fig. 2-3, a first embodiment of the present utility model provides a radio frequency matching circuit, which in this embodiment includes a balun transformer T and a filter circuit.

The balun transformer T includes an unbalanced port and a balanced port, and it should be noted that the balun transformer T is a three-port device, or a wideband radio frequency transmission line transformer that realizes connection between a balanced transmission line circuit and an unbalanced transmission line circuit by converting a matched input signal into a differential output signal, and the balun transformer T has functions of making the system have different impedances or be compatible with differential/single-ended signaling, and can be used in modern communication systems such as a mobile phone and a data transmission network.

In this embodiment, the balanced port includes an input end and an output end respectively grounded, and a phase difference of 180 ° is provided between signals between the input end and the output end of the balanced end, so that the balun can receive the input or output of the transmission line and convert the input or output into a single-ended signal with ground instead of the reverse current in the transmission line as a reference. In addition, the center tap of the balance port is grounded through an isolation circuit.

In this embodiment, the specific circuit structure of the balun transformer T with the balanced port grounded is:

the input end of the balance port of the balun transformer T is grounded through a first filter capacitor C1, and is also connected with a first electrode terminal in parallel, and the first electrode terminal is used for being connected with an external lead; the output end of the balance port of the balun transformer T is grounded through a second filter capacitor C2, and the output end of the balance port is also connected with a second electrode terminal in parallel, and is also used for connecting an external lead.

In addition, the center tap of the balanced port of the balun transformer T is grounded as well, but unlike the input terminal and the output terminal, the center tap is connected to the unbalanced port, specifically, the center tap is connected to the unbalanced port and grounded, and a third filter capacitor C3 is further provided at the front end of the center tap connected to the unbalanced port.

In this embodiment, the balun transformer T is a filter circuit connected to the unbalanced port, and the filter circuit includes a stabilizing inductor L1 and a filter module connected to the stabilizing inductor L1, where the stabilizing inductor L1 is used for preventing current from suddenly changing after flowing through the inductor to generate impedance for alternating current, and the filter module is used for filtering the current to filter alternating current components in the current.

Specifically, the filter module comprises two filter capacitors, wherein one filter capacitor and the stabilizing inductor L1 are arranged in parallel, the other filter capacitor is arranged in series with the stabilizing inductor L1 and the filter capacitor which are arranged in parallel, and the stabilizing inductor L1 and the filter module which are arranged in series are grounded.

In some embodiments, for convenience of description, the filter module includes a fourth filter capacitor C4 and a fifth filter capacitor C5, where the fourth filter capacitor C4 is disposed in parallel with the stabilizing inductor L1, and the fifth filter capacitor C5 is disposed in series with the stabilizing inductor L1 and the fourth filter capacitor C4 disposed in parallel, and is grounded after being connected in series.

It should be further noted that, in this embodiment, by setting the stabilizing inductor L1 and the filtering module at the unbalanced end of the balun transformer T, the balun transformer T can have a filtering function, and the filtering network formed by the stabilizing inductor L1 and the filtering module can simultaneously perform matching and low-frequency notch functions by replacing the matching capacitor in the prior art.

In this embodiment, the layout area of the balun transformer T is 660um x 800um, which is 200um increased in width compared with the area of the conventional balun transformer T of 660um x 600 um.

In summary, by providing the balun transformer T of the network to be filtered, in the practical layout simulation result, the S21 curve is shown to have notch points at 1.8-1.9GHz, 6.7-6.8GHz and 13-13.1 GHz. The scheme realizes the dual functions of impedance transformation and filtering with a smaller area, and has lower manufacturing cost. In the final layout simulation result of the scheme, the in-band interpolation loss is smaller than 1.55dB, the out-of-band suppression is smaller than-12 dB at 1.8-1.9GHz, the out-of-band suppression is smaller than-21 dB at 6.7-6.8GHz, and the out-of-band suppression is smaller than-42 dB at 13-13.1 GHz.

the input end, the output end and the center tap of the balance port of the balun transformer T are respectively grounded, each port is provided with a corresponding filter capacitor to realize a filtering effect, the wave stabilizing inductor L1 and a filter module are arranged on the unbalanced port of the balun transformer T to form a filter network, the filter module comprises two filter capacitors, one filter capacitor is connected with the wave stabilizing inductor L1 in parallel, the other filter capacitor is connected with the wave stabilizing inductor L1 arranged in parallel in series with the filter capacitor and is grounded, so that the balun transformer T has the dual functions of impedance transformation and filtering, the manufacturing cost is low, and the balun transformer T can be popularized and manufactured in mass production.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means 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 of the present utility model. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. 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 foregoing examples illustrate only a few embodiments of the utility model and are described in detail herein without thereby limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.

Claims

1. A radio frequency matching circuit, comprising:

a filter circuit connected to the unbalanced port of the balun transformer;

2. The rf matching circuit of claim 1, wherein the input of the balanced port is grounded through a first filter capacitor and the output of the balanced port is grounded through a second filter capacitor.

3. The radio frequency matching circuit of claim 2, wherein the input of the balanced port is further connected in parallel to a first electrode terminal and the output of the balanced port is further connected in parallel to a second electrode terminal.

4. The radio frequency matching circuit of claim 1, wherein a center tap of said balanced port is connected in parallel to said unbalanced port and to a ground arrangement.

5. The radio frequency matching circuit of claim 4, wherein the front end of the center tap connected to the unbalanced port is further provided with a third filter capacitor.

6. The rf matching circuit of claim 1, wherein the filter module comprises a fourth filter capacitor and a fifth filter capacitor, the fourth filter capacitor being connected in parallel with the surge inductor, the fifth filter capacitor being connected in series to the surge inductor and the fourth filter capacitor being connected in parallel.

7. The radio frequency matching circuit of claim 6, wherein the unbalanced port is further connected in parallel to a third electrode terminal.

8. The radio frequency matching circuit according to any of claims 1-7, wherein the balun transformer has a layout area of 660um x 800um.