Tunable filter bank for enhancing out-of-band rejection

Abstract

The invention relates to a tunable filter bank for enhancing out-of-band rejection. The tunable filter bank comprises a first path switching module, a first filter bank, a second path switching module, a third path switching module, a second filter bank and a fourth path switching module, the first path switching module, the second path switching module, the third path switching module and the fourth path switching module are sequentially connected, and the first filter bank is connected between the first path switching module and the second path switching module. And the second filter bank is connected between the third path switching module and the fourth path switching module. The circuit can be equivalent to one or more of a high-pass filter, a low-pass filter, a transmission line and a band-pass filter, can process signal waveforms in different frequency band ranges, and has the characteristics of high control precision and high reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of analog integrated circuits, and in particular relates to a tunable filter group for enhancing out-of-band suppression. Background Art

[0002] In the field of radio systems such as communications and radar, filters are often used to filter out specific frequency components in the signal to greatly attenuate or suppress noise interference and obtain a signal that meets the expected signal-to-noise wave. For example, a low-pass filter allows low-frequency signals to pass through, while high-frequency signals are attenuated; a high-pass filter, on the contrary, allows high-frequency signals to pass through and attenuates low-frequency signals; a band-pass filter only allows frequency signals within a specific range to pass through, while a band-stop filter blocks frequency signals within a specific range from passing through. In addition, filters can also separate signals of different frequencies to achieve multiplexing, as well as trim the signal waveform to ensure that the signal maintains a good shape and stability during transmission, which is particularly important in data communications and audio applications.

[0003] Nowadays, as radio systems such as communications and radars develop towards high frequency, broadband and miniaturization, filters are required to be able to process signal waveforms in different frequency bands, which may include: low-frequency signals, high-frequency signals and frequency signals in a specific range. However, existing filters cannot meet the needs of processing signal waveforms in different frequency bands. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a tunable filter group with enhanced out-of-band suppression. The technical problem to be solved by the present invention is achieved by the following technical solution:

[0005] The present invention provides a tunable filter group for enhancing out-of-band suppression, comprising: a first path switching module, a first filter group, a second path switching module, a third path switching module, a second filter group and a fourth path switching module; the first path switching module, the second path switching module, the third path switching module and the fourth path switching module are connected in sequence, the first filter group is connected between the first path switching module and the second path switching module, and the second filter group is connected between the third path switching module and the fourth path switching module; the first path switching module is used to control the conduction or disconnection of an internal channel circuit based on the frequency band range of a received radio frequency signal so that the received radio frequency signal flows into the first filter group, so as to perform high-pass filtering on the radio frequency signal to obtain a first high-pass filtered signal, or so that the radio frequency signal passes through the second path switching module, the third path switching module and the fourth path switching module in sequence. Output; the second path switching module is also used to transmit the first high-pass filtered signal to the third path switching module; the third path switching module is also used to control the conduction or shutdown of the internal channel circuit based on the frequency band range of the RF signal or the first high-pass filtered signal, so as to allow the RF signal or the first high-pass filtered signal to enter the second filter group or the fourth path switching module; the second filter group is also used to perform out-of-band suppression processing and low-pass filtering processing on the RF signal or the first high-pass filtered signal in sequence to obtain the corresponding first low-pass filtered signal or first band-pass signal, or to perform low-pass filtering processing on the RF signal or the first high-pass filtered signal to obtain a second low-pass filtered signal or a second band-pass signal; the fourth path switching module is also used to output one of the RF signal, the first high-pass filtered signal, the first low-pass filtered signal, the second low-pass filtered signal, the first band-pass signal and the second band-pass signal.

[0006] Compared with the prior art, the present invention has the following beneficial effects:

[0007] In view of the problem that the existing filters cannot meet the needs of processing signal waveforms in different frequency bands, the present invention proposes a tunable filter group with enhanced out-of-band suppression. The architecture is based on the frequency band of the radio frequency signal. The first path switching module selects the path that the radio frequency signal is to pass through, so that the radio frequency signal directly enters the second path switching unit, or enters the first filter group for high-pass filtering to obtain a first high-pass filtered signal. Then the second path switching unit transmits the signal to the third path switching unit, so that the third path switching unit again determines the path that the signal is to pass through according to the frequency band of the received signal, so that the signal is directly output, or the signal is low-pass filtered. The path passed is different, and the processing method to be faced by the signal is also different. In this way, the tunable filter group with enhanced out-of-band suppression provided by the embodiment of the present invention can be equivalent to one or more of a high-pass filter, a low-pass filter, a transmission line and a bandpass filter, and can process signal waveforms in different frequency bands, with the characteristics of high control accuracy and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a structural block diagram of a tunable filter bank for enhancing out-of-band suppression provided by the present invention;

[0009] Figure 2 It is a circuit connection diagram of a tunable filter group for enhancing out-of-band suppression provided by an embodiment of the present invention;

[0010] Figure 3 is a circuit connection diagram of each high-pass filter in the first filter group provided by an embodiment of the present invention;

[0011] Figure 4 It is a circuit connection diagram of a low-pass filter LPF1, a low-pass filter LPF2 or a low-pass filter LPF3 in a low-pass filter submodule provided in an embodiment of the present invention;

[0012] Figure 5 1 is a circuit connection diagram of a low-pass filter LPF4 in a low-pass filter submodule provided in an embodiment of the present invention;

[0013] Figure 6 is a circuit connection diagram of an adjustable capacitor provided in an embodiment of the present invention;

[0014] Figure 7 1 is a schematic diagram of circuit connections of each low-pass filter in the out-of-band suppression submodule provided by an embodiment of the present invention;

[0015] Figure 8 It is a schematic diagram of test results of the S21 parameter accompanying the change of the radio frequency signal in the tunable filter group with enhanced out-of-band suppression in the high-pass mode provided by an embodiment of the present invention;

[0016] Fig. 9 It is a schematic diagram of test results of the S21 parameter accompanying the change of the radio frequency signal in the tunable filter group with enhanced out-of-band suppression in the low-pass mode provided by an embodiment of the present invention;

[0017] Fig.10 It is a schematic diagram of test results of the S21 parameter in the tunable filter group with enhanced out-of-band suppression in the bandpass mode provided by an embodiment of the present invention accompanying the change of the radio frequency signal. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0019] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0020] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0021] Now, in conjunction with the accompanying drawings, the tunable filter group with enhanced out-of-band suppression provided by the present invention is described in detail.

[0022] Figure 1 : is a structural block diagram of a tunable filter bank for enhancing out-of-band suppression provided by the present invention. Figure 1As shown, it includes: a first path switching module, a first filter group, a second path switching module, a third path switching module, a second filter group and a fourth path switching module; the first path switching module, the second path switching module, the third path switching module and the fourth path switching module are connected in sequence, the first filter group is connected between the first path switching module and the second path switching module, and the second filter group is connected between the third path switching module and the fourth path switching module; the first path switching module is used to control the conduction or disconnection of the internal channel circuit based on the frequency band range of the received radio frequency signal so that the received radio frequency signal flows into the first filter group, so as to perform high-pass filtering on the radio frequency signal to obtain a first high-pass filtered signal, or so that the radio frequency signal is output through the second path switching module, the third path switching module and the fourth path switching module in sequence; the second path switching module is used to control the conduction or disconnection of the internal channel circuit based on the frequency band range of the received radio frequency signal so as to make the received radio frequency signal flow into the first filter group, so as to perform high-pass filtering on the radio frequency signal to obtain a first high-pass filtered signal, or so that the radio frequency signal is output through the second path switching module, the third path switching module and the fourth path switching module in sequence; The path switching module is also used to transmit the first high-pass filter signal to the third path switching module; the third path switching module is also used to control the conduction or shutdown of the internal channel circuit based on the frequency band range of the radio frequency signal or the first high-pass filter signal to allow the radio frequency signal or the first high-pass filter signal to enter the second filter group or the fourth path switching module; the second filter group is also used to perform out-of-band suppression processing and low-pass filtering processing on the radio frequency signal or the first high-pass filter signal in sequence to obtain the corresponding first low-pass filter signal or the first band-pass signal, or to perform low-pass filtering processing on the radio frequency signal or the first high-pass filter signal to obtain the second low-pass filter signal or the second band-pass signal; the fourth path switching module is also used to output one of the radio frequency signal, the first high-pass filter signal, the first low-pass filter signal, the second low-pass filter signal, the first band-pass signal and the second band-pass signal.

[0023] It should be noted that after the RF signal is processed by high-pass filtering and low-pass filtering in sequence, the signal finally generated is a bandpass signal. Specifically, after the first high-pass filtered signal is processed by out-of-band suppression and low-pass filtering in sequence, a first bandpass signal is generated; after the first high-pass filtered signal is processed by low-pass filtering, a second bandpass signal is generated.

[0024] Exemplarily, the RF signal (i.e., RF input) includes: a low frequency signal, a high frequency signal, and a frequency signal within a specific range. The paths that the RF signal can take in the filter bank provided in the embodiment of the present invention include: Figure 1 The paths shown are path 1-path 4, path 1-path 3, path 2-path 4 and path 2-path 3; different filtering functions can be achieved through different paths. Specifically:

[0025] The RF signal enters the first path switching module. When it is determined that there is no interference signal or it is not necessary to filter out the interference signal, the four path switching modules are controlled to make it flow out through path 1 to path 4, thereby realizing the transmission line function, or in other words, realizing the through filtering function.

[0026] When it is determined that the RF signal is lower than the upper cutoff frequency set by the second filter group, and the interference signal in the RF signal is higher than the upper cutoff frequency set by the second filter group, it enters the second filter group through path 1 and path 3 for low-pass filtering, and then outputs to realize the low-pass filtering function.

[0027] When it is determined that the RF signal is higher than the lower cutoff frequency set by the first filter group, and the interference signal in the RF signal is higher than the lower cutoff frequency set by the first filter group, it enters the first filter group through path 2 for high-pass filtering, and then is output through path 4 to realize the high-pass filtering function.

[0028] When it is determined that the RF signal is higher than the lower cutoff frequency set by the first filter group and lower than the upper cutoff frequency set by the second filter group, and when interference signals exist below the lower cutoff frequency set by the first filter group and above the upper cutoff frequency set by the second filter group, the first high-pass filtered signal passes through the second and third path switching modules, and then enters the second filter group through path 3 for processing, and is then output through the fourth path switching module to realize high-pass filtering, out-of-band suppression and low-pass filtering functions.

[0029] Figure 2 FIG. 1 is a circuit connection diagram of a tunable filter group for enhancing out-of-band suppression provided by an embodiment of the present invention. Figure 2 As shown, the first path switching module is a single-pole five-throw switch S1. Exemplarily, the single-pole five-throw switch S1 is a broadband high-isolation single-pole five-throw switch, including a first inductor, a first switch, a second switch, a third switch, a fourth switch and a fifth switch; wherein the first end of the first inductor is used as the input end of the RF signal to input the RF input signal; the first switch, the second switch, the third switch, the fourth switch and the fifth switch are connected in parallel to form a five-way channel circuit; the second end of the first inductor is respectively connected to the input end of each channel circuit. In the actual operation process, by controlling the control voltage corresponding to the five switches in the single-pole five-throw switch S1, one of the five channel circuits is turned on, and the other four channel circuits are turned off, which has the characteristics of small insertion loss, high bandwidth and high isolation.

[0030] Please continue to refer to Figure 1The first filter group includes: a high-pass filter HPF1, a high-pass filter HPF2, a high-pass filter HPF3 and a high-pass filter HPF4 whose bandwidth ranges do not overlap; the input end of the high-pass filter HPF2 is connected to the first output end of the single-pole five-throw switch S1, and the output end is connected to the first input end of the second path switching module; the input end of the high-pass filter HPF4 is connected to the second output end of the single-pole five-throw switch S1, and the output end is connected to the second input end of the second path switching module; the input end of the high-pass filter HPF3 is connected to the fourth output end of the single-pole five-throw switch S1, and the output end is connected to the fourth input end of the second path switching module; the input end of the high-pass filter HPF1 is connected to the fifth output end of the single-pole five-throw switch S1, and the output end is connected to the fifth input end of the second path switching module; the third output end of the single-pole five-throw switch S1 is connected to the third input end of the second path switching module.

[0031] In a possible implementation, high-pass filter HPF1, high-pass filter HPF2, high-pass filter HPF3 and high-pass filter HPF4 are all seventh-order tunable high-pass elliptical filters, which have the effects of occupying a small area and high out-of-band suppression, and have the fastest roll-off speed compared to other architectures, providing higher frequency band selectivity at the same area. Among them, the high-pass filter HPF1 can achieve a cutoff frequency range of 2GHz to 3.9GHz, the high-pass filter HPF2 can achieve a cutoff frequency range of 3.7GHz to 6.7GHz, the high-pass filter HPF3 can achieve a cutoff frequency range of 6.6GHz to 11.2GHz, and the high-pass filter HPF4 can achieve a cutoff frequency range of 11.3GHz to 17.2GHz. In other words, the first filter group can process high-frequency signals of 2GHz to 17.2GHz.

[0032] Figure 3 Schematic diagram of the circuit connection of each high-pass filter in the first filter group provided by the embodiment of the present invention. Figure 3As shown, each high-pass filter includes: an adjustable capacitor C1, an adjustable capacitor C2, an adjustable capacitor C3, an adjustable capacitor C4, an adjustable capacitor C5, an inductor L1, an inductor L2, an inductor L3 and an inductor L4; the adjustable capacitor C1, the adjustable capacitor C2 and the adjustable capacitor C3 are connected in sequence, the adjustable capacitor C1 is connected to the single-pole five-throw switch S1, and the adjustable capacitor C3 is connected to the second path switching module; one end of the inductor L1 is arranged between the adjustable capacitor C1 and the single-pole five-throw switch S1, and the other end is grounded; one end of the inductor L2 is arranged between the adjustable capacitor C1 and the adjustable capacitor C2, and the other end is connected to one end of the adjustable capacitor C4, and the other end of the adjustable capacitor C4 is grounded; one end of the inductor L3 is arranged between the adjustable capacitor C2 and the adjustable capacitor C3, and the other end is connected to one end of the adjustable capacitor C5, and the other end of the adjustable capacitor C5 is grounded; one end of the inductor L4 is arranged between the adjustable capacitor C3 and the second path switching module, and the other end is grounded.

[0033] Please continue to refer to Figure 2 , the second path switching module is a single-pole five-throw switch S2, and the third path switching module is a single-pole five-throw switch S3; the single-pole five-throw switch S2 is respectively connected to the first path switching module and the first filter group, and the single-pole five-throw switch S3 is respectively connected to the second filter group and the fourth path switching module. It should be noted that the single-pole five-throw switch S2 and the single-pole five-throw switch S3 have the same structure and the same working principle as the single-pole five-throw switch S1. For the sake of brevity, it will not be repeated here.

[0034] In a possible implementation, the second filter group includes an out-of-band suppression submodule and a low-pass filter submodule; the first input end and the second input end of the out-of-band suppression submodule are respectively connected to the first output end and the fifth output end of the third path switching module; the second input end and the third input end of the low-pass filter submodule are respectively connected to the second output end and the fourth output end of the third path switching module; the third output end of the third path switching module is connected to the third input end of the fourth path switching module; the two output ends of the out-of-band suppression submodule are respectively connected to the first input end and the fourth input end of the low-pass filter submodule, and the four output ends of the low-pass filter submodule are respectively connected to the first output end and the fourth output end of the fourth path switching module. An input terminal, a second input terminal, a fourth input terminal and a fifth input terminal are connected; an out-of-band suppression submodule is used to perform out-of-band suppression processing on the radio frequency signal to obtain a first filtered signal, or to perform out-of-band suppression processing on the first high-pass filtered signal to obtain a second filtered signal; a low-pass filtering submodule includes multiple groups of low-pass filters with non-overlapping bandwidth ranges, and is used to match a low-pass filter in the multiple groups of high-pass filters based on the bandwidth range of the signal to be filtered, so as to perform low-pass filtering processing on the signal to be filtered, and obtain a first low-pass filtered signal or a second low-pass filtered signal, wherein the signal to be filtered is one of the radio frequency signal, the first high-pass filtered signal, the first filtered signal and the second filtered signal.

[0035] Here, the low-pass filter submodule includes: low-pass filter LPF1, low-pass filter LPF2, low-pass filter LPF3, and low-pass filter LPF4; the input end of the low-pass filter LPF2 is connected to the first input end of the out-of-band suppression submodule, and the output end is connected to the first input end of the fourth path switching module; the input end of the low-pass filter LPF4 is connected to the second output end of the third path switching module, and the output end is connected to the second input end of the fourth path switching module; the input end of the low-pass filter LPF3 is connected to the fourth output end of the third path switching module, and the output end is connected to the fourth input end of the fourth path switching module; the input end of the low-pass filter LPF1 is connected to the second input end of the out-of-band suppression submodule, and the output end is connected to the fifth input end of the fourth path switching module.

[0036] Exemplarily, low-pass filter LPF1, low-pass filter LPF2, low-pass filter LPF3, and low-pass filter LPF4 are all seventh-order tunable low-pass elliptical filters, which have the effect of occupying a small area and high out-of-band suppression. Among them, the cut-off frequency range that can be achieved by low-pass filter LPF1 is 2GHz to 4.2GHz, the cut-off frequency range that can be achieved by low-pass filter LPF2 is 3.2GHz to 6.6GHz, the cut-off frequency range that can be achieved by low-pass filter LPF3 is 5.8GHz to 11.3GHz, and the cut-off frequency range that can be achieved by low-pass filter LPF4 is 9.5GHz to 18GHz. In other words, the second filter group can process high-frequency signals of 2GHz to 18GHz.

[0037] Here, when the RF signal passes through path 2-path 3, the high-pass filter can work with the low-pass filter to achieve band-pass filtering in the range of 2GHz to 18GHz, covering almost the entire frequency band. For example, the high-pass filter HPF1 and the low-pass filter LPF2 can work together to perform band-pass filtering on RF signals in the range of 2GHz to 6.6GHz, and the high-pass filter HPF3 and the low-pass filter LPF4 can work together to perform band-pass filtering on RF signals in the range of 6.6GHz to 18GHz. Whether using a high-pass filter alone, a low-pass filter, or both in combination, the signal processing requirements of different frequency bands can be met.

[0038] Here, the structures of the low-pass filters LPF1, LPF2 and LPF3 are the same, which is a series-first architecture. In order to further enhance out-of-band suppression, the LPF4 with the highest frequency band adopts a parallel-first architecture to improve the design accuracy of the overall filter bank.

[0039] Figure 4 Schematic diagram of the circuit connection of the low-pass filter LPF1, the low-pass filter LPF2 or the low-pass filter LPF3 in the low-pass filter submodule provided in the embodiment of the present invention. Figure 4 As shown, each low-pass filter includes: an inductor L5, an inductor L6, an inductor L7, an inductor L8, an adjustable capacitor C6, an adjustable capacitor C7, an adjustable capacitor C8, an adjustable capacitor C9 and an adjustable capacitor C10; one end of the inductor L5 is connected to the out-of-band suppression submodule or the third path switching module, and the other end is connected to one end of the inductor L6 and one end of the adjustable capacitor C6 respectively, and the other end of the inductor L6 and the other end of the adjustable capacitor C6 are connected to one end of the inductor L7 and one end of the adjustable capacitor C10 respectively. The fourth path switching module is connected to one end of the inductor L7, the other end of the inductor L7 is connected to the other end of the adjustable capacitor C7 and one end of the inductor L8, and the other end of the inductor L8 is connected to the fourth path switching module; the adjustable capacitor C8 is arranged between the inductor L5 and the inductor L6, the adjustable capacitor C9 is arranged between the inductor L6 and the inductor L7, and the adjustable capacitor C10 is arranged between the inductor L7 and the inductor L8; and one end of the adjustable capacitor C8, one end of the adjustable capacitor C9 and one end of the adjustable capacitor C10 are grounded.

[0040] Figure 5 FIG. 1 is a circuit connection diagram of the low-pass filter LPF4 in the low-pass filter submodule provided in an embodiment of the present invention. Figure 5 As shown, the low-pass filter LPF4 includes: an inductor L9, an inductor L10, an inductor L11, an inductor L12, an inductor L13, an adjustable capacitor C11, an adjustable capacitor C12, an adjustable capacitor C13 and an adjustable capacitor C14; the inductor L9, the inductor L10 and the inductor L11 are connected in series, the inductor L9 is connected to the second output end of the third path switching module, and the inductor L11 is connected to the second input end of the fourth path switching module; the adjustable capacitor C11 is arranged between the inductor L9 and the third path switching module The inductor L12 and the adjustable capacitor C12 are connected in series, one end of the inductor L12 is arranged between the inductor L9 and the inductor L10, and one end of the adjustable capacitor C12 is grounded; the inductor L13 and the adjustable capacitor C13 are connected in series, one end of the inductor L13 is arranged between the inductor L10 and the inductor L11, and one end of the adjustable capacitor C13 is grounded; the adjustable capacitor C14 is arranged between the inductor L11 and the fourth path switching module, and one end of the adjustable capacitor C14 is grounded.

[0041] Here, in order to improve the control accuracy, all the adjustable capacitors in the embodiments of the present invention are digital adjustable capacitors, which are designed with six-bit control coding values. Through digital coding, they have the characteristics of high control accuracy and high sensitivity.

[0042] Specifically, Figure 6 FIG. 1 is a schematic diagram of a circuit connection of an adjustable capacitor provided in an embodiment of the present invention. Figure 6As shown, an adjustable capacitor includes six MOS tubes MN1 to MN6 and six capacitors C18 to C23; wherein, a MOS tube and a capacitor are connected in series to form a small unit, and the six small units are connected in parallel; the drains of the six MOS tubes MN1 to MN6 serve as the maximum capacitance output terminal PLUS of the adjustable capacitor, and the sources of the six MOS tubes MN1 to MN6 serve as the minimum capacitance output terminal MINUS of the adjustable capacitor; and the gates of the MOS tubes MN1 to MN6 are connected to the control level. When the control level is a high level signal, the corresponding small unit is turned on, and when the control level is a low level signal, the corresponding small unit is turned off.

[0043] Here, the capacitance is expressed in C as the minimum capacitance unit. The capacitance of capacitor C18 is C, the capacitance of capacitor C19 is 2C, the capacitance of capacitor C20 is 4C, the capacitance of capacitor C21 is 8C, the capacitance of capacitor C22 is 16C, and the capacitance of capacitor C23 is 32C. Ideally, when all 6 MOS tubes are turned on, the capacitance of the adjustable capacitor is the largest, which is 63C; when all 6 MOS tubes are turned off, the capacitance of the adjustable capacitor is the smallest, which is 0; when some of the 6 MOS tubes are turned on, the capacitance of the adjustable capacitor is the sum of the capacitances of multiple capacitors in the on state. Exemplarily, when only MOS tube MN1 and MOS tube MN6 are turned on, the capacitance of the adjustable capacitor is 33C.

[0044] It should be noted that in the high-pass filters HPF1-HPF4 and the low-pass filters LPF1-LPF3, the adjustable capacitors in series state share a set of code values, and the parallel capacitors share a set of code values. Figure 3 Taking a high-pass filter in the example, the first adjustable capacitor, the second adjustable capacitor and the third adjustable capacitor are connected in series, then the MOS tubes in the first adjustable capacitor, the second adjustable capacitor and the third adjustable capacitor are synchronously turned on or off, and the capacitances of the three adjustable capacitors are equal; the fourth adjustable capacitor and the fifth adjustable capacitor are synchronously turned on or off, and the capacitances are equal.

[0045] It should be noted that in the low-pass filter LPF4, the two capacitors connected in series with the inductor share a set of code values, and the other two parallel capacitors share a set of code values. Figure 5 For example, the twelfth adjustable capacitor and the thirteenth adjustable capacitor are turned on or off synchronously, and have the same capacitance; the eleventh adjustable capacitor and the fourteenth adjustable capacitor are turned on or off synchronously, and have the same capacitance.

[0046] It should be understood that in actual use, in order to better increase the voltage resistance effect of the MOS tube, the number of MOS tubes in each small unit can be increased. Exemplarily, a small unit includes two MOS tubes connected in series and a capacitor.

[0047] Please continue to refer to Figure 1In order to better enhance the out-of-band suppression effect and improve the order of the second filter group, the out-of-band suppression submodule includes: a low-pass filter LPF5 and a low-pass filter LPF6; the input end of the low-pass filter LPF5 is connected to the first output end of the third path switching module, and the output end is connected to the first input end of the low-pass filtering submodule; the input end of the low-pass filter LPF6 is connected to the fifth output end of the third path switching module, and the output end is connected to the fourth input end of the low-pass filtering submodule.

[0048] Here, the low-pass filter LPF5 and the low-pass filter LPF6 are fixed-band filters. Figure 7 Schematic diagram of the circuit connection of each low-pass filter in the out-of-band suppression submodule provided by the embodiment of the present invention. Figure 7 As shown, each low-pass filter in the out-of-band suppression submodule includes: an inductor L14, an inductor L15, a capacitor C15, a capacitor C16 and a capacitor C17; the inductor L14 and the inductor L15 are connected in series between the third path switching module and the low-pass filtering submodule; the capacitor C15 is arranged between the inductor L14 and the third path switching module, and one end of the capacitor C15 is grounded; the capacitor C16 is arranged between the inductor L14 and the inductor L15, and one end of the capacitor C16 is grounded; the capacitor C17 is arranged between the inductor L15 and the low-pass filtering submodule, and one end of the capacitor C17 is grounded.

[0049] In view of the problem that the existing filters cannot meet the needs of processing signal waveforms in different frequency bands, the present invention proposes a tunable filter group with enhanced out-of-band suppression. The architecture is based on the frequency band of the radio frequency signal. The first path switching module selects the path that the radio frequency signal is to pass through, so that the radio frequency signal directly enters the second path switching unit, or enters the first filter group for high-pass filtering to obtain a first high-pass filtered signal. Then the second path switching unit transmits the signal to the third path switching unit, so that the third path switching unit again determines the path that the signal is to pass through according to the frequency band of the received signal, so that the signal is directly output, or the signal is low-pass filtered. The paths passed are different, and the processing methods to be faced by the signal are also different. In this way, the tunable filter group with enhanced out-of-band suppression provided by the embodiment of the present invention can be equivalent to a high-pass filter, a low-pass filter, a transmission line and a band-pass filter, and can process signal waveforms in different frequency bands, with the characteristics of high control accuracy and high reliability.

[0050] In order to verify the effect of the tunable filter group with enhanced out-of-band suppression provided by the embodiment of the present invention, a circuit chip including the tunable filter group with enhanced out-of-band suppression provided by the embodiment of the present invention is manufactured and soldered on a test fixture PCB, and an S parameter test is performed on the circuit chip using a vector network analyzer. Figure 8It is a schematic diagram of test results of the S21 parameter accompanying the change of the radio frequency signal in the tunable filter group with enhanced out-of-band suppression in the high-pass mode provided by an embodiment of the present invention; Fig. 9 It is a schematic diagram of test results of the S21 parameter accompanying the change of the radio frequency signal in the tunable filter group with enhanced out-of-band suppression in the low-pass mode provided by an embodiment of the present invention; Fig.10 It is a schematic diagram of test results of the S21 parameter in the tunable filter group with enhanced out-of-band suppression in the bandpass mode provided by an embodiment of the present invention accompanying the change of the radio frequency signal.

[0051] like Figure 8 As shown, the horizontal axis is the frequency of the RF signal, expressed as Freq, in GHz, and the vertical axis is the insertion loss (S21 parameter), in dB; the cutoff frequency of the tunable filter bank architecture in high-pass mode is adjustable in the range of 2GHz to 18GHz, and the S21 parameter is less than 5dB. Fig. 9 As shown in FIG. 1 , the S21 parameter is low-pass, indicating that the cutoff frequency of the tunable filter bank architecture in the low-pass mode is adjustable within the range of 2 GHz to 18 GHz; Fig.10 As shown, the curve HPF1 AND LPF2 can be understood as using the combination of high-pass filter HPF1 and low-pass filter LPF2 to achieve a bandwidth of 2GHz to 6GHz; the curve HPF2 AND LPF3 can be understood as using the combination of high-pass filter HPF2 and low-pass filter LPF3 to achieve a bandwidth of 6GHz to 10GHz; the curve HPF3 AND LPF4 can be understood as using the combination of high-pass filter HPF3 and low-pass filter LPF4 to achieve a bandwidth of 9GHz to 13GHz; the curve HPF4 AND LPF4 can be understood as using the combination of high-pass filter HPF4 and low-pass filter LPF4 to achieve a bandwidth of 14GHz to 18GHz. Fig.10 It can be seen from the figure that under these four curves, the S21 parameter is all bandpass, indicating that the center frequency of the tunable filter bank architecture can be switched in the bandpass mode, ranging from about 3GHz to 16GHz. Figure 8 to Figure 10 It can be explained that the tunable filter group with enhanced out-of-band suppression provided by the embodiment of the present invention can process signal waveforms in different frequency bands and has the characteristics of high control accuracy and high reliability.

[0052] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A tunable filter bank with enhanced out-of-band suppression, characterized in that: include: A first path switching module, a first filter group, a second path switching module, a third path switching module, a second filter group, and a fourth path switching module; The first path switching module, the second path switching module, the third path switching module and the fourth path switching module are connected in sequence, the first filter group is connected between the first path switching module and the second path switching module, and the second filter group is connected between the third path switching module and the fourth path switching module; The first path switching module is used to control the on or off of the internal channel circuit based on the frequency band range of the received radio frequency signal so that the radio frequency signal flows into the first filter group to perform high-pass filtering on the radio frequency signal to obtain a first high-pass filtered signal, or to output the radio frequency signal through the second path switching module, the third path switching module, and the fourth path switching module in sequence; The second path switching module is further used to transmit the first high-pass filtered signal to the third path switching module; The third path switching module is further used to control the on or off of the internal channel circuit based on the frequency band range of the radio frequency signal or the first high-pass filter signal, so as to allow the radio frequency signal or the first high-pass filter signal to enter the second filter group or the fourth path switching module; The second filter group is further used to perform out-of-band suppression processing and low-pass filtering processing on the radio frequency signal or the first high-pass filtered signal in sequence to obtain a corresponding first low-pass filtered signal or a first band-pass signal, or to perform low-pass filtering processing on the radio frequency signal or the first high-pass filtered signal to obtain a second low-pass filtered signal or a second band-pass signal; The fourth path switching module is further used to output one of the RF signal, the first high-pass filter signal, the first low-pass filter signal, the second low-pass filter signal, the first band-pass signal, and the second band-pass signal.

2. The tunable filter bank with enhanced out-of-band suppression according to claim 1, characterized in that: The second filter bank includes an out-of-band suppression submodule and a low-pass filtering submodule; The first input end and the second input end of the out-of-band suppression submodule are respectively connected to the first output end and the fifth output end of the third path switching module; the second input end and the third input end of the low-pass filtering submodule are respectively connected to the second output end and the fourth output end of the third path switching module; the third output end of the third path switching module is connected to the third input end of the fourth path switching module; the two output ends of the out-of-band suppression submodule are respectively connected to the first input end and the fourth input end of the low-pass filtering submodule, and the four output ends of the low-pass filtering submodule are respectively connected to the first input end, the second input end, the fourth input end and the fifth input end of the fourth path switching module; The out-of-band suppression submodule is used to perform out-of-band suppression processing on the radio frequency signal to obtain a first filtered signal, or to perform out-of-band suppression processing on the first high-pass filtered signal to obtain a second filtered signal; The low-pass filtering submodule includes multiple groups of low-pass filters with non-overlapping bandwidth ranges, which are used to match a low-pass filter among the multiple groups of high-pass filters based on the bandwidth range of the signal to be filtered, so as to perform low-pass filtering on the signal to be filtered to obtain the first low-pass filtered signal or the second low-pass filtered signal, wherein the signal to be filtered is one of the RF signal, the first high-pass filtered signal, the first filtered signal and the second filtered signal.

3. The tunable filter bank with enhanced out-of-band suppression according to claim 1, characterized in that: The first path switching module is a single-pole five-throw switch S1; the first filter group includes: a high-pass filter HPF1, a high-pass filter HPF2, a high-pass filter HPF3 and a high-pass filter HPF4 with non-overlapping bandwidth ranges; The input end of the high-pass filter HPF2 is connected to the first output end of the single-pole five-throw switch S1, and the output end is connected to the first input end of the second path switching module; the input end of the high-pass filter HPF4 is connected to the second output end of the single-pole five-throw switch S1, and the output end is connected to the second input end of the second path switching module; the input end of the high-pass filter HPF3 is connected to the fourth output end of the single-pole five-throw switch S1, and the output end is connected to the fourth input end of the second path switching module; the input end of the high-pass filter HPF1 is connected to the fifth output end of the single-pole five-throw switch S1, and the output end is connected to the fifth input end of the second path switching module; The third output terminal of the single-pole five-throw switch S1 is connected to the third input terminal of the second path switching module.

4. The tunable filter bank with enhanced out-of-band suppression according to claim 3, characterized in that: The high-pass filter HPF1, the high-pass filter HPF2, the high-pass filter HPF3 and the high-pass filter HPF4 have the same structure; each high-pass filter includes: an adjustable capacitor C1, an adjustable capacitor C2, an adjustable capacitor C3, an adjustable capacitor C4, an adjustable capacitor C5, an inductor L1, an inductor L2, an inductor L3 and an inductor L4; The adjustable capacitor C1, the adjustable capacitor C2, and the adjustable capacitor C3 are connected in sequence, the adjustable capacitor C1 is connected to the single-pole five-throw switch S1, and the adjustable capacitor C3 is connected to the second path switching module; One end of the inductor L1 is arranged between the adjustable capacitor C1 and the single-pole five-throw switch S1, and the other end is grounded; One end of the inductor L2 is arranged between the adjustable capacitor C1 and the adjustable capacitor C2, and the other end is connected to one end of the adjustable capacitor C4, and the other end of the adjustable capacitor C4 is grounded; One end of the inductor L3 is arranged between the adjustable capacitor C2 and the adjustable capacitor C3, and the other end is connected to one end of the adjustable capacitor C5, and the other end of the adjustable capacitor C5 is grounded; One end of the inductor L4 is disposed between the adjustable capacitor C3 and the second path switching module, and the other end is grounded.

5. The tunable filter bank with enhanced out-of-band suppression according to claim 2, characterized in that: The low-pass filter submodule includes: a low-pass filter LPF1, a low-pass filter LPF2, a low-pass filter LPF3, and a low-pass filter LPF4; The input end of the low-pass filter LPF2 is connected to the first input end of the out-of-band suppression submodule, and the output end is connected to the first input end of the fourth path switching module; the input end of the low-pass filter LPF4 is connected to the second output end of the third path switching module, and the output end is connected to the second input end of the fourth path switching module; the input end of the low-pass filter LPF3 is connected to the fourth output end of the third path switching module, and the output end is connected to the fourth input end of the fourth path switching module; the input end of the low-pass filter LPF1 is connected to the second input end of the out-of-band suppression submodule, and the output end is connected to the fifth input end of the fourth path switching module.

6. The tunable filter bank with enhanced out-of-band suppression according to claim 5, characterized in that: The low-pass filter LPF1, the low-pass filter LPF2 and the low-pass filter LPF3 have the same structure, and each low-pass filter includes: an inductor L5, an inductor L6, an inductor L7, an inductor L8, an adjustable capacitor C6, an adjustable capacitor C7, an adjustable capacitor C8, an adjustable capacitor C9 and an adjustable capacitor C10; One end of the inductor L5 is connected to the out-of-band suppression submodule or the third path switching module, and the other end is respectively connected to one end of the inductor L6 and one end of the adjustable capacitor C6, the other end of the inductor L6 and the other end of the adjustable capacitor C6 are respectively connected to one end of the inductor L7 and one end of the adjustable capacitor C7, the other end of the inductor L7 and the other end of the adjustable capacitor C7 are connected to one end of the inductor L8, and the other end of the inductor L8 is connected to the fourth path switching module; The adjustable capacitor C8 is arranged between the inductor L5 and the inductor L6, the adjustable capacitor C9 is arranged between the inductor L6 and the inductor L7, and the adjustable capacitor C10 is arranged between the inductor L7 and the inductor L8; and one end of the adjustable capacitor C8, one end of the adjustable capacitor C9 and one end of the adjustable capacitor C10 are grounded.

7. The tunable filter bank with enhanced out-of-band suppression according to claim 5, characterized in that: The low-pass filter LPF4 includes: an inductor L9, an inductor L10, an inductor L11, an inductor L12, an inductor L13, an adjustable capacitor C11, an adjustable capacitor C12, an adjustable capacitor C13 and an adjustable capacitor C14; The inductor L9, the inductor L10, and the inductor L11 are connected in series, the inductor L9 is connected to the second output end of the third path switching module, and the inductor L11 is connected to the second input end of the fourth path switching module; The adjustable capacitor C11 is arranged between the inductor L9 and the third path switching module, and one end of the adjustable capacitor C11 is grounded; The inductor L12 and the adjustable capacitor C12 are connected in series, one end of the inductor L12 is arranged between the inductor L9 and the inductor L10, and one end of the adjustable capacitor C12 is grounded; The inductor L13 and the adjustable capacitor C13 are connected in series, one end of the inductor L13 is arranged between the inductor L10 and the inductor L11, and one end of the adjustable capacitor C13 is grounded; The adjustable capacitor C14 is disposed between the inductor L11 and the fourth path switching module, and one end of the adjustable capacitor C14 is grounded.

8. The tunable filter bank with enhanced out-of-band suppression according to claim 2, characterized in that: The out-of-band suppression submodule includes: a low-pass filter LPF5 and a low-pass filter LPF6; The input end of the low-pass filter LPF5 is connected to the first output end of the third path switching module, and the output end is connected to the first input end of the low-pass filtering submodule; The input end of the low-pass filter LPF6 is connected to the fifth output end of the third path switching module, and the output end is connected to the fourth input end of the low-pass filtering submodule.

9. The tunable filter bank with enhanced out-of-band suppression according to claim 8, characterized in that: The low-pass filter LPF5 and the low-pass filter LPF6 have the same structure, and each low-pass filter in the out-of-band suppression submodule includes: an inductor L14, an inductor L15, a capacitor C15, a capacitor C16 and a capacitor C17; The inductor L14 and the inductor L15 are connected in series between the third path switching module and the low-pass filter submodule; The capacitor C15 is arranged between the inductor L14 and the third path switching module, and one end of the capacitor C15 is grounded; The capacitor C16 is arranged between the inductor L14 and the inductor L15, and one end of the capacitor C16 is grounded; The capacitor C17 is disposed between the inductor L15 and the low-pass filter submodule, and one end of the capacitor C17 is grounded.

10. The tunable filter bank with enhanced out-of-band suppression according to claim 3, characterized in that: The second path switching module is a single-pole five-throw switch S2, and the third path switching module is a single-pole five-throw switch S3; The single-pole five-throw switch S2 is connected to the first path switching module and the first filter group respectively, and the single-pole five-throw switch S3 is connected to the second filter group and the fourth path switching module respectively.

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