SAW (Surface Acoustic Wave) filter circuit compatible with multi-package communication RF (Radio Frequency)

Abstract

The utility model relates to the technical field of wireless communication RF signal transmission and filtering, and provides a SAW filter circuit compatible with multi-package communication RF, which comprises an input matching Pi-attenuation circuit, an input compatible circuit, a switchable package, an output compatible circuit and an output matching Pi-attenuation circuit, the input matching pi attenuation circuit is used for matching and attenuating an input signal; the input compatible circuit is used for transmitting an input signal; the switchable package is used for switching different packages or filter resistors of the SAW filter and filtering an input signal; the output compatible circuit is used for transmitting an output signal; the output matching Pi attenuation circuit is used for matching and attenuating the output signal; the switchable package comprises an S4 package of the SAW filter, an S5 package of the SAW filter or a resistor R53. By adopting the input matching Pi-decay circuit, the input compatible circuit, the switchable package, the output compatible circuit and the output matching Pi-decay circuit, compatibility of SAW filters of different packages is achieved, three different packages of the switchable package are used for switching, mounting of different SAW filters is achieved through the same circuit and the same PCB, and the compatibility of the SAW filters is improved. And the development cost and the development period are greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of wireless communication radio frequency signal transmission and filtering, in particular to a SAW filter circuit for communication radio frequency RF that is compatible with multiple packages. Background Art

[0002] During the transmission of radio frequency signals in the communication field, signal filtering needs to be performed through a SAW filter for communication radio frequency RF. At present, due to various reasons such as manufacturer processes and frequency bands, there are many packages for SAW filters in the industry, mainly including 6 major categories of differences such as S4 (6 pins), S5 (8 pins), 3*3mm, 3.8*3.8mm, etc. Existing filters generally use a single package, that is, only one type of SAW filter can be mounted in one circuit. However, due to package differences, different PCBs and circuits are often required to meet the mounting requirements of different SAW filters.

[0003] Chinese Patent with publication number CN111201711A discloses an RF front-end module including a hybrid filter and an active circuit in a single package, which is packaged through the hybrid filter and the active circuit. However, this module cannot achieve the mounting of different SAW filters through the same circuit and the same PCB, resulting in a relatively high development cost and a long cycle. Summary of the Utility Model

[0004] In view of this, the utility model proposes a SAW filter circuit for communication radio frequency RF that is compatible with multiple packages. By adopting an input matching π attenuation circuit, an input compatibility circuit, a switchable package, an output compatibility circuit, and an output matching π attenuation circuit, the compatibility with different packages of SAW filters is realized. The three different packages of the switchable package are used for switching, and the mounting of different SAW filters is achieved through the same circuit and the same PCB, greatly reducing the development cost and the development cycle, and solving the problem of high development cost and long cycle caused by the need for different PCBs and circuit designs for different packages of SAW filters.

[0005] The technical solution of the utility model is realized as follows: A SAW filter circuit for communication radio frequency RF that is compatible with multiple packages includes an input matching π attenuation circuit, an input compatibility circuit, a switchable package, an output compatibility circuit, and an output matching π attenuation circuit:

[0006] The input matching π attenuation circuit is electrically connected to the input compatibility circuit and is used for matching and attenuating the input signal;

[0007] The input compatibility circuit is electrically connected to the switchable package and is used for transmitting the input signal;

[0008] The switchable package is electrically connected to the output compatibility circuit, which is used to switch different packages of the SAW filter or filter resistors to filter the input signal;

[0009] The output compatibility circuit is electrically connected to the output matching π attenuation circuit, which is used to transmit the output signal;

[0010] The output matching π attenuation circuit is electrically connected to the output compatibility circuit, which is used to match and attenuate the output signal;

[0011] The switchable package includes the S4 package of the SAW filter, the S5 package of the SAW filter, or the resistor R53.

[0012] Based on the above technical solutions, preferably, the input matching π attenuation circuit includes resistors R1, R2, and R3;

[0013] One end of resistor R1 and one end of resistor R2 are both connected to the RF_IN signal. The other end of resistor R1 is electrically connected to one end of resistor R3. The other end of resistor R2 and the other end of resistor R3 are both grounded.

[0014] Based on the above technical solutions, preferably, the input compatibility circuit includes resistors R4, R5, R6, and R7;

[0015] One end of resistor R4 and one end of resistor R5 are both electrically connected to the other end of resistor R1. The other end of resistor R5 is electrically connected to one end of resistor R7. The other end of resistor R7 is grounded. The other end of resistor R4 is electrically connected to one end of resistor R6. The other end of resistor R6 is grounded.

[0016] Based on the above technical solutions, preferably, the output compatibility circuit includes resistors R8, R9, R10, and R12;

[0017] One end of resistor R8 is electrically connected to one end of resistor R9. The other end of resistor R8 is grounded. One end of resistor R10 is electrically connected to one end of resistor R12. The other end of resistor R12 is grounded.

[0018] Based on the above technical solutions, preferably, the output matching π attenuation circuit includes resistors R11, R13, and R52;

[0019] One end of resistor R11 is respectively electrically connected to one end of resistor R13, the other end of resistor R9, and the other end of resistor R10. The other end of resistor R13 is grounded. The other end of resistor R11 and the other end of resistor R52 both output the RF_OUT signal. The other end of resistor R13 and the other end of resistor R52 are both grounded.

[0020] Based on the above technical solutions, preferably, when the switchable package is the S4 package of the SAW filter, the switchable package includes the SAW filter U1;

[0021] Pin 1 of the SAW filter U1 is electrically connected to the other end of the resistor R4 and one end of the resistor R6 respectively. Pin 2 of the SAW filter U1 is electrically connected to one end of the resistor R9 and one end of the resistor R8 respectively. Pins 3, 4, 7, and 8 of the SAW filter U1 are all grounded. Pin 5 of the SAW filter U1 is electrically connected to one end of the resistor R10 and one end of the resistor R12 respectively. Pin 6 of the SAW filter U1 is electrically connected to the other end of the resistor R5 and one end of the resistor R7 respectively;

[0022] Resistors R5, R6, R9, and R12 are all attached with 0-ohm resistors, and resistors R4, R7, R8, and R10 are all attached with empty pads.

[0023] Based on the above technical solutions, preferably, when the switchable package is the S5 package of the SAW filter, the switchable package includes the SAW filter U1;

[0024] Pin 1 of the SAW filter U1 is electrically connected to the other end of the resistor R4 and one end of the resistor R6 respectively. Pin 2 of the SAW filter U1 is electrically connected to one end of the resistor R9 and one end of the resistor R8 respectively. Pins 3, 4, 7, and 8 of the SAW filter U1 are all grounded. Pin 5 of the SAW filter U1 is electrically connected to one end of the resistor R10 and one end of the resistor R12 respectively. Pin 6 of the SAW filter U1 is electrically connected to the other end of the resistor R5 and one end of the resistor R7 respectively;

[0025] Resistors R4, R7, R8, and R12 are all attached with 0-ohm resistors, and resistors R5, R6, R9, and R12 are all attached with empty pads.

[0026] Based on the above technical solutions, preferably, when the switchable package is the resistor R53;

[0027] One end of the resistor R53 is electrically connected to the other end of the resistor R5 and one end of the resistor R7 respectively, and the other end of the resistor R53 is electrically connected to one end of the resistor R8 and one end of the resistor R9 respectively;

[0028] Resistors R1, R5, R9, and R11 are all attached with 0-ohm resistors, resistors R2, R3, R4, R6, R7, R8, R10, R12, R13, and R52 are all attached with empty pads, and the resistor R53 uses a 0-ohm resistor with a 0850 package.

[0029] A SAW filter circuit for communication radio frequency RF that is compatible with multiple packages provided by the present utility model has the following beneficial effects compared with the prior art:

[0030] (1) By adopting an input matching π attenuation circuit, an input compatibility circuit, a switchable package, an output compatibility circuit, and an output matching π attenuation circuit, compatibility with SAW filters of different packages is achieved.

[0031] (2) By switching among three different packages of the switchable package, the mounting of different SAW filters is realized through the same circuit and the same PCB, greatly reducing the development cost and development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a structural diagram of a SAW filter circuit for a communication radio frequency (RF) that is compatible with multiple packages according to the present invention.

[0034] Figure 2 It is a wiring diagram when the switchable package is the S4 package of the filter according to the present invention.

[0035] Figure 3 It is the pin definition of the S4 package of the SAW filter according to the present invention.

[0036] Figure 4 It is a wiring diagram when the switchable package is the S5 package of the filter according to the present invention.

[0037] Figure 5 It is the pin definition of the S5 package of the SAW filter according to the present invention.

[0038] Figure 6 It is a wiring diagram when the switchable package is a filter resistor according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0040] Please refer to Figure 1, this embodiment provides a SAW filter circuit for communication radio frequency (RF) that is compatible with multiple packages, including an input matching π attenuation circuit 1, an input compatibility circuit 2, a switchable package 3, an output compatibility circuit 4, and an output matching π attenuation circuit 5:

[0041] The input matching π attenuation circuit 1 is electrically connected to the input compatibility circuit 2 and is used to match and attenuate the input signal;

[0042] The input compatibility circuit 2 is electrically connected to the switchable package 3 and is used to transmit the input signal;

[0043] The switchable package 3 is electrically connected to the output compatibility circuit 4 and is used to switch different packages of the SAW filter or filter resistors to filter the input signal;

[0044] The output compatibility circuit 4 is electrically connected to the output matching π attenuation circuit 5 and is used to transmit the output signal;

[0045] The output matching π attenuation circuit 5 is electrically connected to the output compatibility circuit 4 and is used to match and attenuate the output signal;

[0046] The switchable package 3 includes the S4 package of the SAW filter, the S5 package of the SAW filter, or the resistor R53.

[0047] The SAW filter circuit for communication RF that is compatible with multiple packages in this embodiment uses the input matching π attenuation circuit 1, the input compatibility circuit 2, the switchable package 3, the output compatibility circuit 4, and the output matching π attenuation circuit 5 to achieve compatibility with SAW filters of different packages. By switching among three different packages included in the switchable package 3, the mounting of different SAW filters is realized on the same circuit and the same PCB, greatly reducing the development cost and development cycle.

[0048] The input matching π attenuation circuit 1 includes resistors R1, R2, and R3;

[0049] One end of resistor R1 and one end of resistor R2 are both connected to the RF_IN signal. The other end of resistor R1 is electrically connected to one end of resistor R3. The other ends of resistor R2 and resistor R3 are both grounded.

[0050] The input compatibility circuit 2 includes resistors R4, R5, R6, and R7;

[0051] One end of resistor R4 and one end of resistor R5 are both connected to the other end of resistor R1. The other end of resistor R5 is connected to one end of resistor R7. The other end of resistor R7 is grounded. The other end of resistor R4 is connected to one end of resistor R6. The other end of resistor R6 is grounded.

[0052] The output compatibility circuit 4 includes resistors R8, R9, R10, and R12;

[0053] One end of resistor R8 is electrically connected to one end of resistor R9, the other end of resistor R8 is grounded, one end of resistor R10 is electrically connected to one end of resistor R12, and the other end of resistor R12 is grounded.

[0054] The output matching π attenuation circuit 5 includes resistors R11, R13, and R52;

[0055] One end of resistor R11 is electrically connected to one end of resistor R13, the other end of resistor R9, and the other end of resistor R10 respectively. The other end of resistor R13 is grounded. The other end of resistor R11 and the other end of resistor R52 both output the RF_OUT signal, and the other end of resistor R13 and the other end of resistor R52 are both grounded.

[0056] Specifically, the input compatibility circuit 2 includes resistors R4, R5, R6, and R7. The output signals of the input matching π attenuation circuit 1 are respectively connected to resistors R4 and R5. Resistor R4 and resistor R6 are connected in series to ground with a common pad, and resistor R5 and resistor R7 are connected in series to ground with a common pad.

[0057] As Figures 2-3 shown, when the switchable package 3 is the S4 package of the SAW filter, the switchable package 3 includes a SAW filter U1;

[0058] Pin 1 of the SAW filter U1 is electrically connected to the other end of resistor R4 and one end of resistor R6 respectively. Pin 2 of the SAW filter U1 is electrically connected to one end of resistor R9 and one end of resistor R8 respectively. Pins 3, 4, 7, and 8 of the SAW filter U1 are all grounded. Pin 5 of the SAW filter U1 is electrically connected to one end of resistor R10 and one end of resistor R12 respectively. Pin 6 of the SAW filter U1 is electrically connected to the other end of resistor R5 and one end of resistor R7 respectively;

[0059] Resistors R5, R6, R9, and R12 are all mounted with 0-ohm resistors, and resistors R4, R7, R8, and R10 are all mounted without components.

[0060] When the switchable package 3 is the S4 or S5 package of the filter, the common pad connection point of resistors R4 and R6 is connected to the upper left input pin of the switchable package 3, and the common pad connection point of resistors R5 and R7 is connected to the middle input pin of the switchable package 3; As Figure 3 shown, when the switchable package 3 is the S4 package of the SAW filter, resistor R4 is mounted, resistor R6 is not mounted, resistor R5 is not mounted, and resistor R7 is mounted.

[0061] Specifically, as Figures 2-3As shown in the figure, this embodiment provides an application of a SAW filter with an S4 package. Among them, 0-ohm resistors are soldered to the input terminals R5 and R6, and no components are soldered to R4 and R7. 0-ohm resistors are soldered to the output terminals R9 and R12, and no components are soldered to R10 and R8. The signal is input from port 1, passes through the 1dBm π attenuation matching network composed of R1, R2, and R3, and then is connected to the input pin 6 (the middle pin) of the SAW filter in the S4 package through the 0-ohm resistor R5, and reaches the output pin 2 (the middle pin) and then passes through the 0-ohm resistor R9 to the 1dBm π attenuation matching network composed of R11, R52, and R13 for output.

[0062] As Figures 4-5 shown, when the switchable package 3 is an S5 package of the SAW filter, the switchable package 3 includes a SAW filter U1;

[0063] One end of the pin 1 of the SAW filter U1 is electrically connected to the other end of the resistor R4 and one end of the resistor R6 respectively. One end of the pin 2 of the SAW filter U1 is electrically connected to one end of the anti-phase R9 and one end of the resistor R8 respectively. The pins 3, 4, 7, and 8 of the SAW filter U1 are all grounded. One end of the pin 5 of the SAW filter U1 is electrically connected to one end of the resistor R10 and one end of the resistor R12 respectively. One end of the pin 6 of the SAW filter U1 is electrically connected to the other end of the resistor R5 and one end of the resistor R7 respectively;

[0064] 0-ohm resistors are soldered to the resistors R4, R7, R8, and R12, and no components are soldered to the resistors R5, R6, R9, and R12.

[0065] Specifically, as Figures 4-5 shown, when the switchable package 3 is an S5 package of the SAW filter, the resistor R4 is not soldered, the resistor R6 is soldered, the resistor R5 is soldered, and the resistor R7 is not soldered.

[0066] As Figures 4-5 shown, this embodiment provides an application of a SAW filter with an S5 package. Among them, 0-ohm resistors are soldered to the input terminals R4 and R7, and no components are soldered to R5 and R6. 0-ohm resistors are soldered to the output terminals R10 and R8, and no components are soldered to R9 and R12. The signal is input from port 1, passes through the 1dBm π attenuation matching network composed of R1, R2, and R3, and then is connected to the input pin 1 (the upper left pin) of the SAW filter in the S4 package through the 0-ohm resistor R4, and reaches the output pin 5 (the lower right pin) and then passes through the 0-ohm resistor R10 to the 1dBm π attenuation matching network composed of R11, R52, and R13 for output;

[0067] As Figure 6 shown, when the switchable package 3 is the resistor R53;

[0068] One end of resistor R53 is electrically connected to the other end of resistor R5 and one end of resistor R7 respectively, and the other end of resistor R53 is electrically connected to one end of resistor R8 and one end of resistor R9 respectively;

[0069] Resistors R1, R5, R9 and R11 are all mounted with 0-ohm resistors, resistors R2, R3, R4, R6, R7, R8, R10, R12, R13 and R52 are all empty-mounted, and resistor R53 is a 0-ohm resistor with 0850 package.

[0070] Specifically, as Figure 6 shown, this embodiment provides an application of an empty-mounted SAW filter. Among them, the input terminal R5 is mounted with a 0-ohm resistor, R4, R7, and R6 are empty-mounted, the output terminal R9 is mounted with a 0-ohm resistor, R10, R8, and R12 are empty-mounted, the input matching terminal R1 is mounted with a 0-ohm resistor, R2 and R3 are empty-mounted, the output matching terminal R11 is mounted with a 0-ohm resistor, R13 and R52 are empty-mounted, and the signal is input from port 1, passes through the 0-ohm resistor R1, and then is connected to R53 (the middle pad of the SAW filter) through the 0-ohm resistor R5, and is output through the 0-ohm resistors R9 and R11; at this time, it should be noted that R53 must be a 0-ohm resistor with 0805 package, and the package size matches the size spacing of the middle pins of the SAW filter; in the case of a SAW filter circuit that is not required, the design requirements can also be met through 0 ohms.

[0071] Specifically, when the switchable package 3 is an empty-mounted SAW filter (resistor R53), resistor R4 is not mounted, resistor R6 is mounted, resistor R5 is mounted, resistor R7 is not mounted, and the SAW filter is mounted with a 0-ohm 0805 resistor R53 on the middle pins.

[0072] Specifically, the output compatibility circuit 4 includes resistors R8, R9, R10, and R12. The middle output pin of the switchable package 3 is connected to the common pad of resistor R8 and resistor R9. Resistor R8 and resistor R9 are connected in series to ground. The lower right output pin of the switchable package 3 is connected to the common pad of resistor R10 and resistor R12. Resistor R10 and resistor R12 are connected in series to ground. The other ends of resistors R9 and R10 are connected to the input of the output matching π attenuation circuit 5; when the switchable package 3 is the S4 package of the SAW filter, resistor R8 is mounted, resistor R9 is not mounted, resistor R10 is mounted, and resistor R12 is not mounted; when the switchable package 3 is the S5 package of the SAW filter, resistor R8 is not mounted, resistor R9 is mounted, resistor R10 is not mounted, and resistor R12 is mounted; when the switchable package 3 is an empty-mounted SAW filter, resistor R8 is not mounted, resistor R9 is mounted, resistor R10 is not mounted, resistor R12 is mounted, and the SAW filter is mounted with a 0-ohm 0805 package resistor R53 on the middle pins.

[0073] The working principle of a SAW filter circuit for a communication radio frequency (RF) that is compatible with multiple packages in this embodiment is as follows:

[0074] The signal is input from Port 1 for radio frequency. The input signal RF_IN passes through the input matching π attenuation circuit 1 and the input compatibility circuit 2 and then enters the SAW filters with different packages (switchable package 3). Then, through the output compatibility circuit 4 and the output matching π attenuation circuit 5, it reaches the radio frequency output port, and the RF_OUT signal is output.

[0075] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A SAW filter circuit compatible with multi-package communication radio frequency RF, characterized in that: It includes an input matching π-decay circuit (1), an input compatible circuit (2), a switchable package (3), an output compatible circuit (4) and an output matching π-decay circuit (5): The input matching π-attenuation circuit (1) is electrically connected to the input compatible circuit (2) and is used to match and attenuate the input signal; The input compatible circuit (2) is electrically connected to the switchable package (3) for transmitting input signals; The switchable package (3) is electrically connected to the output compatible circuit (4) and is used to switch different packages or filter resistors of the SAW filter to filter the input signal; The output compatible circuit (4) is electrically connected to the output matching π decay circuit (5) for transmitting the output signal; The output matching π-attenuation circuit (5) is electrically connected to the output compatible circuit (4) and is used to match and attenuate the output signal; The switchable package (3) includes an S4 package of a SAW filter, an S5 package of a SAW filter or a resistor R53.

2. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 1, characterized in that: The input matching π decay circuit (1) comprises resistors R1, R2 and R3; One end of the resistor R1 and one end of the resistor R2 are both connected to the RF_IN signal, the other end of the resistor R1 is electrically connected to one end of the resistor R3, and the other end of the resistor R2 and the other end of the resistor R3 are both grounded.

3. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 2, characterized in that: The input compatible circuit (2) comprises resistors R4, R5, R6 and R7; One end of the resistor R4 and one end of the resistor R5 are both electrically connected to the other end of the resistor R1, the other end of the resistor R5 is electrically connected to one end of the resistor R7, the other end of the resistor R7 is grounded, the other end of the resistor R4 is electrically connected to one end of the resistor R6, and the other end of the resistor R6 is grounded.

4. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 3, characterized in that: The output compatible circuit (4) comprises resistors R8, R9, R10 and R12; One end of the resistor R8 is electrically connected to one end of the resistor R9 , and the other end of the resistor R8 is grounded. One end of the resistor R10 is electrically connected to one end of the resistor R12 , and the other end of the resistor R12 is grounded.

5. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 4, characterized in that: The output matching π decay circuit (5) comprises resistors R11, R13 and R52; One end of the resistor R11 is electrically connected to one end of the resistor R13, the other end of the resistor R9 and the other end of the resistor R10 respectively, the other end of the resistor R13 is grounded, the other end of the resistor R11 and the other end of the resistor R52 both output the RF_OUT signal, and the other end of the resistor R13 and the other end of the resistor R52 are both grounded.

6. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 5, characterized in that: When the switchable package (3) is an S4 package of a SAW filter, the switchable package (3) comprises a SAW filter U1; Pin 1 of the SAW filter U1 is electrically connected to the other end of the resistor R4 and one end of the resistor R6, respectively; Pin 2 of the SAW filter U1 is electrically connected to one end of the resistor R9 and one end of the resistor R8, respectively; Pins 3, 4, 7 and 8 of the SAW filter U1 are grounded; Pin 5 of the SAW filter U1 is electrically connected to one end of the resistor R10 and one end of the resistor R12, respectively; Pin 6 of the SAW filter U1 is electrically connected to the other end of the resistor R5 and one end of the resistor R7, respectively; Resistors R5, R6, R9 and R12 are all 0 ohm resistors, and resistors R4, R7, R8 and R10 are all empty.

7. A SAW filter circuit compatible with multi-package communication radio frequency RF as claimed in claim 5, characterized in that: When the switchable package (3) is an S5 package of a SAW filter, the switchable package (3) comprises a SAW filter U1; Pin 1 of the SAW filter U1 is electrically connected to the other end of the resistor R4 and one end of the resistor R6, respectively; Pin 2 of the SAW filter U1 is electrically connected to one end of the resistor R9 and one end of the resistor R8, respectively; Pins 3, 4, 7 and 8 of the SAW filter U1 are grounded; Pin 5 of the SAW filter U1 is electrically connected to one end of the resistor R10 and one end of the resistor R12, respectively; Pin 6 of the SAW filter U1 is electrically connected to the other end of the resistor R5 and one end of the resistor R7, respectively; Resistors R4, R7, R8 and R12 are all 0 ohm resistors, and resistors R5, R6, R9 and R12 are all empty.

8. The SAW filter circuit of a multi-package communication radio frequency RF as claimed in claim 5, characterized in that: When the switchable package (3) is a resistor R53; One end of the resistor R53 is electrically connected to the other end of the resistor R5 and one end of the resistor R7, and the other end of the resistor R53 is electrically connected to one end of the resistor R8 and one end of the resistor R9; Resistors R1, R5, R9 and R11 are all 0 ohm resistors, resistors R2, R3, R4, R6, R7, R8, R10, R12, R13 and R52 are all empty, and resistor R53 uses a 0 ohm resistor in 0850 package.

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