CN111835312A - Radio frequency filter circuit - Google Patents

Abstract

A radio frequency filter circuit of the invention belongs to the technical field of radio frequency filtering. It includes a port one and a port two, a main branch MB is connected between the port one and the port two, the main branch MB is provided with two downwardly extending branches, and the two downwardly extending branches are respectively provided with a filter REA and filter REB, a matching network MNA is connected between the filter REA and port one, and a matching network MNB is connected between the filter REB and port B. The matching network MNA can provide impedance matching at one port, and the matching network MNB can provide impedance matching at the second port. The radio frequency filter circuit of the present invention has simple structure, small size and better performance.

Description

A radio frequency filter circuit

technical field

The invention belongs to the technical field of radio frequency filtering, in particular to a radio frequency filtering circuit.

Background technique

RF filters are widely used in the transceiver chain of RF terminals, allowing signals of a specific frequency or frequency band to pass through, while filtering out unwanted interference or spurious signals. It is composed of several resonance units, which are connected in different circuit forms to provide a filter circuit with a certain bandwidth.

Radio frequency (RF) filter circuits typically include multiple RF filter chains, each chain providing a different passband tuned in a different RF communication frequency band so that RF signals operating in the different RF communication frequency band can be transmitted to the appropriate downstream circuit. To prevent adjacent RF communication bands from interfering with each other (especially when RF communication bands are close to each other), it is often necessary to increase the roll-off of the passband to increase out-of-band rejection. This is usually accomplished by using a notch filter component that creates a notch near the passband, thereby increasing passband roll-off and out-of-band rejection. For passbands in the high frequency range, the roll-off provided by the LC filter is generally not sufficient to provide sufficient isolation between the passband in close proximity (about 100 MHz or less) and the high frequency range (frequency ranges above 1 GHz). Therefore, it would be desirable to provide radio frequency filter circuits capable of increasing out-of-band rejection in the high frequency range.

Filters constructed from discrete components can no longer meet the performance, size and cost requirements of today's products. However, acoustic wave filters such as SAW and BAW support the selection of the corresponding filter in a complete package like a monolith. The filter can operate at high and low frequencies (up to 6GHz), is one of the smallest physically and has the best performance and cost points for complex filtering requirements.

The LC filter can achieve excellent linear phase characteristics (group delay characteristics), but it is at the expense of the selectivity, and it is bulky, has poor stability, and is troublesome to debug.

The main working principle of the SAW surface acoustic wave element is to use the piezoelectric properties of piezoelectric materials, and use the input and output transducers to convert the input signal of the radio wave into mechanical energy. After processing, the mechanical energy is converted into an electrical signal to achieve filtering. Unnecessary signals and noise, the goal of improving the quality of reception. SAW filters and SAW resonators are widely used in various wireless communication systems. The main function is to filter out the noise, which is simpler to install and smaller than the traditional LC filter.

Another common new type of RF filter is the bulk acoustic wave filter. BAW is different from the SAW filter. The sound wave in the BAW filter propagates vertically. For the BAW resonator using quartz crystal as the substrate, the metal embedded on both sides of the top and bottom of the quartz substrate excites the sound wave, so that the sound wave bounces from the top surface to the bottom to form a standing sound wave. The slab thickness and electrode mass determine the resonant frequency.

SUMMARY OF THE INVENTION

1. The technical problem to be solved by the invention

The purpose of the present invention is to solve the problems of complex structure and poor performance of the existing radio frequency filter circuit.

2. Technical solutions

In order to achieve the above object, the technical scheme provided by the invention is:

A radio frequency filter circuit of the present invention includes a port 1 and a port 2, a main branch MB is connected between the port 1 and the port 2, and the main branch MB is provided with two downwardly extending branches, the two downwardly extending branches are The extended branches are respectively provided with a filter REA and a filter REB, a matching network MNA is connected between the filter REA and port one, and a matching network MNB is connected between the filter REB and port B.

Preferably, a notch network NWA coupled to the main branch MB is also included.

Preferably, the filter MNA is a parallel resonator, one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are connected in parallel, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are all relative to The main branches MB are connected in parallel.

Preferably, the filter MNB is a parallel resonator, and one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are connected in parallel, and one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are all relative to The main branches MB are connected in parallel.

Preferably, the trap network NWA is a trap network provided with several capacitive elements CN in parallel with each other, and each capacitive element CN is coupled between the resonator REA and the resonator REB.

Preferably, the notch network NWA is a notch network provided with several acoustic resonators YN connected in parallel with each other, and each acoustic resonator YN is coupled between the resonator REA and the resonator REB.

Preferably, the notch network NWA is a notch network provided with a plurality of acoustic wave resonators YN and a plurality of capacitive elements CN in parallel with each other, and each acoustic wave resonator YN and each capacitive element CN are coupled to the resonator REA and resonator REB.

3. Beneficial effects

Adopting the technical scheme provided by the present invention, compared with the prior art, has the following beneficial effects:

A radio frequency filter circuit of the present invention includes a port 1 and a port 2, a main branch MB is connected between the port 1 and the port 2, and the main branch MB is provided with two downwardly extending branches, the two downwardly extending branches are The extended branches are respectively provided with a filter REA and a filter REB, a matching network MNA is connected between the filter REA and port one, and a matching network MNB is connected between the filter REB and port B. The matching network MNA can provide impedance matching at one port, and the matching network MNB can provide impedance matching at the second port. The radio frequency filter circuit of the present invention has simple structure, small size and better performance.

Description of drawings

1 is a schematic structural diagram of a radio frequency filter circuit of the present invention;

Fig. 2 is the structural representation of the filter REA of the present invention;

Fig. 3 is the structural representation of filter REB of the present invention;

4 is a schematic structural diagram of the notch network NWA of Embodiment 1;

5 is a schematic structural diagram of a notch network NWA in Embodiment 2;

FIG. 6 is a schematic structural diagram of a notch network NWA in Embodiment 3. As shown in FIG.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be more fully described below with reference to the related drawings, in which several embodiments of the present invention are given, however, the present invention can be implemented in many different forms and is not limited to this The described embodiments are, rather, provided so that this disclosure will be thorough and complete.

It should be noted that when an element is referred to as being "fixed" to 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 may be be directly connected to another element or intervening elements may be present; the terms "vertical", "horizontal", "left", "right" and similar expressions are used herein for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the present invention; the terms used herein in the description of the present invention are only used to describe specific embodiments is not intended to limit the invention; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

Referring to FIGS. 1 to 4 , a radio frequency filter circuit of this embodiment includes a port 1 and a port 2, a main branch MB is connected between the port 1 and the port 2, and two downward extending branches are arranged on the main branch MB. Branches, the two downwardly extending branches are respectively provided with a filter REA and a filter REB, a matching network MNA is connected between the filter REA and port one, and a matching network MNA is connected between the filter REB and port B Match the network MNB. The matching network MNA may provide impedance matching at port one. The matching network MNB may provide impedance matching at port two.

Also included is a notch network NWA coupled to the main branch MB. The notch network NWA is configured to define a stopband within the passband of the transmission response without significantly increasing the ripple variation within the passband defined by the transmission response. Thus, although the notch network NWA is coupled to the main branch MB, the transmission response passband between port one and port two is substantially unaffected by the notch network NWA. Therefore, the notch network NWA is sufficiently isolated from the resonators REA, REB so that the interaction between the notch network NWA and the resonators REA, REB does not increase the variation within the passband.

The filter MNA is a parallel resonator, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are connected in parallel, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The filter MNB is a parallel resonator, one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are connected in parallel, and one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The trap network NWA of this embodiment is a trap network provided with a plurality of capacitive elements CN in parallel with each other, and each capacitive element CN is coupled between the resonator REA and the resonator REB.

Example 2

Referring to FIGS. 1 to 3 and 5, a radio frequency filter circuit in this embodiment includes a port 1 and a port 2, and a main branch MB is connected between the port 1 and the port 2, and the main branch MB is provided with two direction A branch extending downward, the two downward extending branches are respectively provided with a filter REA and a filter REB, a matching network MNA is connected between the filter REA and the port one, and the filter REB and the port B are connected. There is a matching network MNB connected between them.

Also included is a notch network NWA coupled to the main branch MB.

The filter MNA is a parallel resonator, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are connected in parallel, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The filter MNB is a parallel resonator, one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are connected in parallel, and one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The trap network NWA of this embodiment is a trap network provided with a plurality of acoustic wave resonators YN in parallel with each other, and each acoustic wave resonator YN is coupled between the resonator REA and the resonator REB.

Example 3

Referring to FIGS. 1 to 3 and 6, a radio frequency filter circuit in this embodiment includes a port 1 and a port 2, and a main branch MB is connected between the port 1 and the port 2, and the main branch MB is provided with two direction A branch extending downward, the two downward extending branches are respectively provided with a filter REA and a filter REB, a matching network MNA is connected between the filter REA and the port one, and the filter REB and the port B are connected. There is a matching network MNB connected between them.

Also included is a notch network NWA coupled to the main branch MB.

The filter MNA is a parallel resonator, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are connected in parallel, and one or more inductive elements LA, capacitive elements CA and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The filter MNB is a parallel resonator, one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are connected in parallel, and one or more inductive elements LB, capacitive elements CB and acoustic wave resonators are all connected in parallel with respect to the main branch MB connect.

The trap network NWA of the present embodiment is a trap network provided with several acoustic wave resonators YN and several capacitive elements CN in parallel with each other, and each acoustic wave resonator YN and each capacitive element CN are coupled to the resonator REA and the between the vibrator REB.

The above-mentioned embodiment only expresses a certain embodiment of the present invention, and its description is more specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention; it should be pointed out that for those of ordinary skill in the art Said that, on the premise of not departing from the concept of the present invention, several modifications and improvements can be made, which all belong to the protection scope of the present invention; therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (7)

1. A radio frequency filter circuit, characterized by: the filter comprises a first port and a second port, a main branch MB is connected between the first port and the second port, two downward extending branches are arranged on the main branch MB, a filter REA and a filter REB are respectively arranged on the two downward extending branches, a matching network MNA is connected between the filter REA and the first port, and a matching network MNB is connected between the filter REB and the second port.

2. A radio frequency filter circuit according to claim 1, wherein: also included is a notch network NWA coupled to the main branch MB.

3. A radio frequency filter circuit according to claim 1, wherein: the filter MNA is a parallel resonator, and one or more of the inductance element LA, the capacitance element CA, and the acoustic wave resonator are connected in parallel, and the one or more of the inductance element LA, the capacitance element CA, and the acoustic wave resonator are connected in parallel with respect to the main branch MB.

4. A radio frequency filter circuit according to claim 1, wherein: the filter MNB is a parallel resonator, and one or more of the inductive element LB, the capacitive element CB, and the acoustic resonator are connected in parallel, and the one or more of the inductive element LB, the capacitive element CB, and the acoustic resonator are connected in parallel with respect to the main branch MB.

5. A radio frequency filter circuit according to claim 2, wherein: the trap network NWA is a trap network provided with several capacitive elements CN connected in parallel to each other, each capacitive element CN being coupled between the resonator REA and the resonator REB.

6. A radio frequency filter circuit according to claim 2, wherein: the trap network NWA is a trap network provided with a plurality of acoustic wave resonators YN connected in parallel, and each acoustic wave resonator YN is coupled between a resonator REA and a resonator REB.

7. A radio frequency filter circuit according to claim 2, wherein: the trap network NWA is a trap network provided with a plurality of acoustic wave resonators YN and a plurality of capacitance elements CN connected in parallel, and each acoustic wave resonator YN and each capacitance element CN are coupled between the resonator REA and the resonator REB.

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