Frequency hopping band elimination filter

Abstract

The invention provides a frequency hopping band elimination filter which comprises a coaxial resonant cavity, a metal resonant column arranged in the coaxial resonant cavity and a digital capacitor array used for frequency tuning. The digital capacitor array comprises a plurality of capacitor chip sets, each capacitor chip set comprises a plurality of capacitor chips, each capacitor chip comprises an upper electrode and a lower electrode which are oppositely arranged, the lower electrodes are directly welded on the end surfaces of the metal resonant columns, the upper electrodes are connected with bonding wires, and the bonding wires are connected with the metal resonant columns. The bonding wire is used for being electrically connected with a control circuit. The digital capacitor is connected with the metal resonance column and the control circuit in a direct welding and gold wire bonding mode, lower and more stable insertion loss is achieved in the aspect of electrical performance, and extremely high connection consistency is ensured in the aspect of mechanical reliability; and a solid physical foundation is laid for the frequency hopping stop-band filter to realize high-Q-value, high-precision and high-reliability frequency tuning in the S wave band.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and more specifically, to a frequency-hopping bandstop filter. Background Technology

[0002] A band-stop filter is a circuit specifically designed to suppress signals within a specific frequency band while allowing signals outside that band to pass through. This type of circuit can combat interference within a specific frequency band. Fixed-band band-stop filters cannot effectively combat strong interference signals that change with time and rapidly. When electronic equipment faces such electronic warfare environments, its performance will deteriorate sharply, and in severe cases, it may even lose its ability to function.

[0003] Fixed-band band-stop filters cannot cope with enemy or sudden, rapid frequency-hopping interference. Therefore, developing a band-stop filter capable of real-time tracking and rapid switching of the stopband center frequency is imperative. This is not only the core of achieving dynamic spectrum access and management, but also an essential technological path to improve the survivability, reliability, and agility of key equipment such as radar and communications in electronic warfare. It is a strategic requirement that must be overcome in the current microwave technology field.

[0004] The core value of frequency-hopping bandstop filters lies in upgrading the function of filters from "static setting" to "dynamic response". Through its core characteristic that the center frequency of the stopband can be quickly reconstructed according to external commands (such as frequency hopping sequences), it has become a key enabling technology for dealing with intelligent interference and managing congested spectrum. Frequency-hopping bandstop filters have key value in the following high-demand scenarios: (1) Electronic countermeasures and military equipment: applied to radar systems and military communication equipment, by dynamically and quickly adjusting the center frequency of the filter's stopband, it can accurately "shield" frequency-hopping interference, significantly improving the survivability, detection reliability and communication confidentiality of equipment in strong confrontation environments; (2) Dynamic spectrum management and cognitive radio: used in civilian or tactical communications to realize intelligent spectrum access and sharing. The system can sense and avoid authorized frequency bands or sudden interference in real time, and quickly reconstruct the passband in commonly used frequency bands, thereby maximizing spectrum utilization efficiency and communication reliability; (3) High-performance testing and protection of complex electromagnetic environments: providing an active and programmable frequency domain protection barrier for important electronic equipment, used for laboratory testing or cutting-edge equipment to cope with increasingly complex and dense electromagnetic signal environments.

[0005] Frequency-hopping bandstop filters provide radars, especially phased array radars and electronic warfare radars, with powerful adaptive anti-jamming capabilities. When the radar's main lobe or side lobes are subjected to narrowband blocking interference from enemy devices targeting its operating frequency, the radar control system can sense the interfering frequency in real time and instruct the filter to quickly "switch" the stopband to that frequency, forming a precise "spectrum barrier." This effectively suppresses interference energy from entering the receiving channel, significantly improving the radar's signal-to-interference-plus-noise ratio and target detection capability in jammed environments, without affecting the radar's own signal transmission and reception. During frequency agility, the filter can synchronously switch, consistently suppressing tracking interference emitted by enemy reconnaissance or jamming equipment on specific frequency bands. This ensures that the receiver remains "clean" during frequency hopping, improving the overall low probability of intercept and survivability of the radar system. In electronic support and anti-radiation operations, this technology can also be used to protect friendly receiving equipment from damage caused by high-power enemy signals.

[0006] Frequency-hopping bandstop filters can also be applied to high-reliability, high-security communications. In frequency-hopping communication, although the carrier frequency changes continuously, it may still encounter high-intensity suppression interference at each instantaneous frequency point. By integrating this filter into the receiver front end and synchronizing its stopband with the communication frequency-hopping sequence but slightly lagging behind, or by changing it according to reconnaissance results, interference at the current operating frequency point can be precisely "eliminated," thereby protecting the vulnerable receiver low-noise amplifier and ensuring that the communication link is not interrupted. This is crucial for data links and tactical radios. Improving spectrum coexistence and utilization efficiency: In shared environments with scarce spectrum resources (such as military-civilian shared frequency bands), when a communication system senses a strong radar pulse or other system signal in the same frequency band within the communication band, the filter's stopband center can be instantly adjusted to the carrier frequency of that pulse, effectively suppressing this instantaneous strong interference, avoiding receiver saturation and blocking, achieving dynamic spectrum sharing, and improving the intelligence and flexibility of overall spectrum utilization.

[0007] The basic circuit form of a band-stop filter is usually as follows: Figure 1 As shown, its core structure consists of a straight main radio frequency transmission line and several resonators 12 coupled to this line. The signal enters from the input port 10 of the filter and is transmitted along the main transmission line to the output port 11. The key point here is that each parallel-coupled resonator 12 corresponds to a specific characteristic frequency (resonant frequency).

[0008] When the frequency of the input signal happens to coincide with the characteristic frequency of a resonator, parallel resonance occurs. In this case, the resonator exhibits extremely low electrical impedance, effectively providing an efficient short-circuit branch to ground for that frequency component in the signal transmission path. According to circuit theory, the signal energy at this frequency is primarily absorbed and dissipated by the resonator (or reflected back to the source), and cannot continue to propagate to the output port, thus forming a steep stopband (attenuation pole) on the frequency response curve.

[0009] Conversely, when the signal frequency differs from the resonator's characteristic frequency, the resonator is detuned and exhibits high impedance. It is almost "invisible" to the main transmission line, allowing the signal to pass through directly with virtually no loss, forming a passband. By carefully designing and arranging multiple resonators, the width and suppression depth of the stopband can be combined, widened, or shaped to achieve specific filtering characteristics.

[0010] Therefore, this structure essentially utilizes the frequency-selective short-circuit mechanism of the resonator to precisely "carve out" one or more narrow stopbands within a wide bandwidth, achieving a filtering function where "specific frequencies are blocked while other frequencies are unobstructed." Its performance directly depends on the resonator's quality factor (Q value)—a higher Q value results in a sharper resonance curve, lower insertion loss, steeper stopband edges (better shape factor), and stronger frequency selectivity.

[0011] In applications with extremely high requirements (such as radar receiver anti-jamming), high-Q resonators such as coaxial cavity resonators are often used to achieve performance far exceeding that of microstrip planar structures. This type of band-stop filter replaces the LC resonator with a coaxial cavity resonator, such as… Figure 2 As shown, 121 is a coaxial cavity resonator, 122 is a coupling input terminal, and 123 is a metal resonant pillar.

[0012] To achieve tuning of the filter's characteristic frequency, a method is to add a tunable capacitor to the resonator, such as... Figure 3 As shown. Tuning capacitors can be implemented in various ways, such as varactor diodes, and dynamic numerically controlled loading of capacitor arrays using electronic switches. Capacitor arrays that achieve capacitor adjustment through numerical control loading are also called digital capacitor arrays 13. This capacitor tuning method has a very large capacitance adjustment range and fine adjustment steps, which is difficult for varactor diodes to match.

[0013] The basic structure of a coaxial cavity bandstop filter is as follows: Figure 4 As shown, the filter body consists of five parts: a coaxial resonant cavity 120, an input port 10, an output port 11, a main transmission line, and a parallel resonant unit (the main structure of which is a metal resonant pillar 123). Both the input and output ports are coaxial transmission lines, which can be connected to standard coaxial connectors (such as N-type or SMA). A precision-machined coaxial cable forms the main signal transmission channel between the two ports, responsible for low-loss transmission of RF energy within the passband.

[0014] The key functional unit consists of two (or more) independent high-Q coaxial resonant cavities 120, which are arranged in parallel outside the main transmission line. Each resonant cavity is energy coupled to the main transmission line through a metal probe called a "coupling link 122". One end of the link is coupled to the inner conductor of the main transmission line in a capacitive or inductive manner, and the other end extends into the resonant cavity and connects to the metal resonant post 123, forming a window for electromagnetic energy exchange.

[0015] Its working principle is as follows: when the signal frequency on the main transmission line is out of tune with the natural frequency of a certain resonant cavity, the energy passes through almost unaffected; when the signal frequency matches the resonant frequency, the cavity resonates strongly and presents an extremely low impedance, almost a short circuit, on the main transmission line through the coupling link 122, thereby efficiently absorbing and reflecting the energy of that frequency, forming a deep stopband. By independently adjusting the resonant frequency of each cavity (for example, through an internally loaded digital capacitor array), a rapid and precise jump in the stopband center frequency can be achieved.

[0016] Traditional methods solder digital capacitors to a separate circuit board and then mechanically press them into the housing. This approach introduces multiple layers of pads, vias, and unstable contact interfaces. More seriously, the unstable press-fit causes these parasitic parameters to fluctuate randomly, directly compromising the consistency between the filter's resonant frequency and Q value.

[0017] like Figure 5 As shown, the digital capacitor chip is surface-mounted onto a separate control circuit board 15. This circuit board is electrically connected to the metal resonant post 123 led out from inside the coaxial resonant cavity via mechanical crimping.

[0018] Specifically, to achieve the connection, the bottom of the control circuit board 15 is designed with a metal pad 152, which is connected to another metal pad 151 on the top layer of the board through a metallized via 150. The digital capacitor 139 is soldered to this top layer metal pad 151. During installation, the metal resonant post 123 of the cavity is directly pressed into the pad hole at the bottom of the control circuit board 15, and physical contact is maintained by spring force or screw pressure.

[0019] The main drawback of this approach is the introduction of significant additional losses and unreliability. First, the signal path lengthens, requiring passage through pads, vias, top-mount pads, and multiple interconnects. These structures introduce non-negligible series resistance and parasitic inductance at radio frequency, increasing insertion loss. Second, the contact resistance of mechanically crimped connections is significantly affected by pressure, oxidation, and thermal expansion and contraction, easily leading to contact instability and causing filter insertion loss and center frequency drift. Ultimately, these problems directly result in poor filter performance consistency during mass production, making it difficult to guarantee tuning accuracy and long-term reliability, thus becoming a key bottleneck restricting the development of high-performance frequency-hopping filters. Summary of the Invention

[0020] The purpose of this invention is to provide a frequency-hopping bandstop filter with lower insertion loss, greater stability, and higher mechanical reliability.

[0021] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a frequency-hopping bandstop filter, including a coaxial resonant cavity, a metal resonant pillar disposed inside the coaxial resonant cavity, and a digital capacitor array for frequency tuning; the digital capacitor array includes multiple capacitor chip groups, each capacitor chip group includes multiple capacitor chips, each capacitor chip includes an upper electrode and a lower electrode disposed opposite to each other, the lower electrode is directly soldered to the end face of the metal resonant pillar, and the upper electrode is connected to a bonding wire for electrical connection with a control circuit.

[0022] In one embodiment, the capacitance values ​​of each group of capacitor chips form a geometric sequence with a common ratio of n, where n is an integer greater than 1.

[0023] In one embodiment, when n is 2, the digital capacitor array is composed of four types of capacitor chips whose capacitance values ​​are in a geometric sequence with a common ratio of 4. Each type of capacitor chip is provided in three, with two capacitor chips connected in parallel to form a capacitor chip group, and the other capacitor chip forming an independent capacitor chip group.

[0024] In one embodiment, multiple capacitor chips of each type are distributed close to each other, and the four types of capacitor chips are arranged at intervals along the circumferential direction of the metal resonant pillar.

[0025] In one embodiment, the capacitor chip is a single-layer dielectric plate capacitor, which includes a dielectric plate, and the upper electrode and the lower electrode are respectively disposed on the upper and lower surfaces of the dielectric plate.

[0026] Furthermore, the frequency hopping bandstop filter also includes a control circuit, which is connected to the bonding wire to control whether the corresponding capacitor chip is connected to the resonant circuit.

[0027] In one embodiment, multiple control circuits are provided, and each control circuit is connected to a capacitor chip group in a corresponding manner.

[0028] Furthermore, the frequency hopping bandstop filter also includes a control circuit board disposed within the coaxial resonant cavity. The control circuit board is positioned above the metal resonant pillar, and each of the control circuits is disposed on the control circuit board and surrounds the digital capacitor array.

[0029] In one embodiment, the control circuit includes a switching diode, which is a flat cylindrical bare chip. The two electrodes of the diode are respectively disposed on the upper and lower sides of the cylinder. One electrode is directly soldered to the pad of the control circuit board, and the other electrode is connected to another pad of the control circuit board through a bonding wire.

[0030] Preferably, the bonding wire is a bonding alloy wire.

[0031] The beneficial effects of the technical solution provided by this invention are as follows: This invention connects digital capacitors to metal resonant pillars and control circuits through "direct welding + gold wire bonding", which achieves lower and more stable insertion loss in terms of electrical performance and ensures extremely high connection consistency in terms of mechanical reliability. This lays a solid physical foundation for frequency hopping stopband filters to achieve high Q value, high precision and high reliability frequency tuning in the S-band. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below.

[0033] Figure 1 This is a schematic diagram of the circuit structure of an existing band-stop filter; Figure 2 This is a schematic diagram of an existing band-stop filter that uses a coaxial cavity resonator. Figure 3 A schematic diagram of an existing bandstop filter with adjustable notch frequency; Figure 4 This is a schematic diagram of an existing coaxial cavity bandstop filter. Figure 5 This is a schematic diagram of the connection structure between an existing digital capacitor and a coaxial cavity metal resonant pillar. Figure 6 This is a schematic diagram of the structure of a single-layer dielectric parallel plate capacitor provided in one embodiment of the present invention; Figure 7 This is a schematic diagram of the connection structure between a digital capacitor and a metal resonant pillar provided in one embodiment of the present invention; Figure 8 This is a schematic diagram of the connection structure between a digital capacitor array and a metal resonant pillar according to an embodiment of the present invention; Figure 9 A schematic diagram of the circuit structure connecting a set of digital capacitors and a control circuit according to an embodiment of the present invention; Figure 10 A three-dimensional structural diagram illustrating the connection between a set of digital capacitors and a control circuit according to an embodiment of the present invention; Figure 11 This is a schematic diagram of the overall structure of a capacitor loading control circuit board provided in one embodiment of the present invention; Figure 12 This is a schematic diagram of the circuit structure of a digitally capacitor-loaded resonant cavity with an adjustable notch frequency, according to an embodiment of the present invention. Detailed Implementation

[0034] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0035] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0036] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to". The term "connection" can refer to a direct connection or an indirect connection via intermediate components (elements). The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the following description.

[0037] Please combine Figures 4-12 This invention provides a frequency-hopping band-stop filter, which is an improvement on existing coaxial cavity band-stop filters. It has the basic structure of a coaxial cavity band-stop filter, namely, the filter body consists of five parts: a coaxial resonant cavity 120, an input port 10, an output port 11, a main transmission line, and parallel resonant units. Additionally, please refer to... Figure 7 The frequency hopping bandstop filter also has a digital capacitor array 13 and a control circuit 14 for controlling whether the capacitors in the capacitor array are connected to the resonant network.

[0038] To achieve the wide-range and high-precision tuning required for the frequency-hopping filter in the S-band (2~4GHz), this embodiment, as an example, employs a digital capacitor array based on a binary sequence as the core tuning unit. This array consists of a series of independent, directly digitally controlled miniature capacitor units connected in parallel. Its key design feature is that the capacitance values ​​of each unit strictly follow a binary geometric sequence, meaning that the capacitance value of each subsequent capacitor is twice that of the previous one; for example, the capacitance value sequence could be C, 2C, 4C, 8C, etc.

[0039] It should be noted that the digital capacitor array 13 is composed of multiple groups of capacitor chips, and the capacitance values ​​of each group of capacitor chips form a geometric sequence with a common ratio of n, where n is an integer greater than 1, all of which can achieve the purpose of the present invention.

[0040] The core advantage of the above design lies in its superior tuning capability and digital control characteristics. First, it achieves an extremely wide capacitance adjustment range: the theoretical upper limit of the total capacitance can be obtained by connecting all units in parallel, while the lower limit is determined by the smallest capacitance unit (the basic capacitance C). The ratio between the two (i.e., the tuning ratio) can reach hundreds or even thousands, far superior to traditional varactor diodes. Second, it ensures precise tuning steps: by combining capacitors with different binary bits for switching, continuous and precise discrete capacitance adjustment from the minimum capacitance C to the maximum value can be achieved, using the minimum capacitance C as the basic step size.

[0041] Furthermore, this architecture exhibits excellent linearity and controllability. The capacitance value and the input digital control code have a linear weighted relationship, which directly translates into a near-linear response between the resonant frequency and the digital control code. This greatly simplifies the driving algorithm and enables fast, hysteresis-free frequency transitions. Simultaneously, this structure offers greater tolerance for component manufacturing tolerances, and by increasing the number of array bits (capacitor types), the tuning range and accuracy can be linearly extended, providing an ideal and reliable tuning solution for high-performance S-band frequency hopping filters.

[0042] In this embodiment, the digital capacitors used are divided into four specifications: 0.25fF, 1fF, 4fF, and 16fF. Three of each type of capacitor are used. Taking the 0.25fF capacitor as an example, one capacitor has a capacitance of 0.25fF, and the other two are connected in parallel to form two capacitor chip groups with a capacitance of 0.5fF. Similarly, three 1fF capacitors can form two capacitor chip groups with capacitance values ​​of 1fF and 2fF; three 4fF capacitors can form two capacitor chip groups with capacitance values ​​of 4fF and 8fF; and three 16fF capacitors can form two capacitor chip groups with capacitance values ​​of 16fF and 32fF. Thus, the 12 digital capacitors form eight chip capacitor groups 131~138, forming an 8-bit binary capacitor array with capacitance values ​​ranging from 0.25fF to 32fF. Depending on whether capacitors are connected, an adjustable capacitor array with a range of 0~63.75fF and increments of 0.25fF can be achieved.

[0043] When digital capacitors are connected to a resonator circuit, the resonant frequency decreases; the larger the capacitance, the lower the frequency drop. When no digital capacitors are connected, the resonator's resonant frequency is at its highest, and correspondingly, the band-stop filter has the highest notch frequency. When all capacitors are connected, the harmonic frequencies of the band-stop filter drop to the lower limit.

[0044] Four types of digital capacitors, totaling twelve, are uniformly soldered onto the outer periphery of the upper surface of the coaxial resonator's metal pillars. Three capacitor chips of each type are arranged close together, and the four types of capacitor chips are spaced apart along the circumference of the metal resonator pillars, as shown below. Figure 8 As shown.

[0045] The advantages of the design, which involves welding 12 digital capacitors in a circular pattern onto the surface of a metal resonant pillar and then centrally connecting them via gold wire bonding, are as follows: (1) The structure is compact and symmetrical, minimizing and uniformly dispersing the electromagnetic field of the resonant cavity by the tuning unit, which is beneficial for maintaining the purity and high Q value of the resonant mode. (2) The centralized bonding area facilitates automated production, improving manufacturing efficiency and consistency, and reducing costs. (3) All control circuits are concentrated in one place, simplifying the internal wiring of the resonant cavity and improving the overall reliability and maintainability of the structure.

[0046] like Figure 6 As shown, the digital capacitor of the present invention is a single-layer dielectric plate capacitor 130, which includes a dielectric plate 1301, an upper electrode 1302, and a lower electrode 1303. The upper and lower electrodes are respectively disposed on the upper and lower surfaces of the dielectric plate. The lower electrode of the digital capacitor is directly soldered to the end face of the metal resonant pillar 123. The upper electrode is connected to a bonding wire 18, and the other end of the bonding wire 18 is used for electrical connection with the control circuit, such as... Figure 7 As shown in the figure. The bonding wire is a bonding alloy wire, integrating the advantages of gold wire connections, such as good flexibility, low parasitic parameters, and high consistency. This structure fundamentally avoids the inherent problems of contact stress relaxation, oxidation, and fretting wear in mechanical crimping, thus ensuring the absolute stability of the long-term electrical connection.

[0047] This invention connects digital capacitors to metal resonant pillars and control circuits through "direct welding + gold wire bonding," achieving lower and more stable insertion loss in electrical performance and ensuring extremely high connection consistency in mechanical reliability. This lays a solid physical foundation for frequency hopping stopband filters to achieve high Q value, high precision, and high reliability frequency tuning in the S-band.

[0048] This invention uses a single-layer parallel-plate capacitor with uniform dielectric as the basic unit. Its structure determines that it has extremely low parasitic inductance (suitable for high frequencies), extremely high capacitance accuracy, and temperature stability, which provides the physical possibility for achieving precise and stable minimum tuning steps. Secondly, it innovatively uses four base values—0.25fF, 1fF, 4fF, and 16fF—in binary combinations. The ingenuity of this design lies in using 0.25fF, a small capacitance value achievable with a single-layer capacitor, as the minimum tuning step (LSB). Through parallel combinations of different base values, it can theoretically continuously cover a wide range from 0 to (16+4+1+0.25)*3=63.75fF with a 0.25fF step, achieving an ultra-wide tuning range sufficient to cover the requirements of S-band sub-bands. Secondly, it ensures extremely high tuning resolution (0.25fF step), meeting the requirements of radar and high-density communication for precise frequency positioning; thirdly, the tuning characteristics are essentially digital and linear, because the capacitance value is a weighted sum of control codes, which makes the frequency and control codes highly linear, simplifying the driving algorithm and realizing fast, lag-free frequency switching.

[0049] As described above, the digital capacitor of this invention is connected to the resonator network via control circuit 14. See also... Figure 9 Taking a set of digital capacitors 131 connected to a control circuit 141 as an example, the control circuit 141 mainly consists of a switching diode, a choke inductor, and a coupling capacitor. The core of the control circuit 141 is the switching diode, which controls whether the digital capacitors are connected to the resonator network. The choke inductor is used for voltage biasing of the diodes; its inductive reactance needs to be sufficiently large (usually making its self-resonant frequency much higher than the operating frequency) to ensure that the RF signal does not flow back into the control power supply. Simultaneously, its DC resistance should be sufficiently small to avoid excessive bias voltage drop. The coupling capacitor has a large capacitance (much larger than the fixed capacitance of the tuning filter frequency). Its main function is to provide effective DC blocking, while presenting an extremely low impedance to the RF signal, almost like a short circuit. Therefore, the coupling capacitor hardly affects the loading of the fixed capacitance. Furthermore, its self-resonant frequency must be much higher than the S-band operating frequency to prevent it from becoming inductive in the application frequency band, thus losing its coupling function and introducing additional losses. When the control voltage Vt is 0V, the two reverse-connected diodes conduct, and the fixed capacitance is connected to the circuit. When the control voltage is 100V (this voltage value is related to the power capacity of the filter; the greater the power passed through the filter, the greater this control voltage), both diodes are cut off, the switch is open, and the fixed-value capacitor is not connected to the resonator circuit.

[0050] Because the control circuit requires high-speed, low-loss switching of the capacitor's input state, traditionally packaged diodes, due to their large package parasitic parameters, will degrade high-frequency switching performance. Please refer to... Figure 10The diode used in this invention is a flat cylindrical bare chip. The electrodes of the diode are on the top and bottom sides of the cylinder. One electrode is directly soldered to a pad 1405 of the control circuit board 15, and the other electrode is connected to another pad 1407 of the circuit board via a gold wire bonding, forming a low-inductance circuit. This integration method, which combines direct soldering of the bare chip of the switching diode with gold wire bonding, not only results in a compact structure but, more importantly, minimizes the parasitic inductance and encapsulation capacitance associated with traditional packaged diodes. This allows the switch to have a faster response speed and better RF performance in the S-band.

[0051] according to Figure 9 The control circuit shown uses two switching diodes, 1401 and 1402, connected in parallel back-to-back with opposite polarities. The upper pads of the two diodes are connected to the bias voltage (3.3V) 1408 and the switching control voltage (Vt) 1409 respectively via a choke inductor 1403 and bonding wires 1400 and 1406. The choke inductor 1403 is made of wire wound metal and presents extremely high impedance to RF signals, thus it can be considered an open circuit. The coupling capacitor 1404 is a lumped capacitor in a 0201 package (imperial units), with a capacitance in the nF range, much larger than that of a digital capacitor. It is used for bias voltage isolation and presents very low impedance to RF signals, thus it can be considered a short circuit.

[0052] Furthermore, since the two diodes are connected in reverse parallel, both diodes conduct in the forward direction when the control voltage is 0V, providing a symmetrical low-impedance path for the RF signal and connecting the capacitor to the circuit. When a sufficiently high reverse voltage (such as 100V) is applied, both diodes reliably cut off, isolating the capacitor from the circuit. This design has two major advantages: first, it provides near-ideal RF switching characteristics, with extremely low and symmetrical impedance when conducting and high isolation when cut off; second, it completely eliminates the influence of diode junction capacitance nonlinearity on the resonator, because regardless of the state, the RF voltage applied across a single diode is clamped to a very low value, thereby significantly improving the linearity and power capacity of the filter.

[0053] This invention employs eight independent capacitor chip groups 131-138, and the loading method of each capacitor chip group and eight control circuits 141-148, as follows: Figure 11 and Figure 12 As shown. The eight control voltages Vt1 to Vt8 constitute the digital control combination of the frequency hopping bandstop filter, which can realize 256 filtering waveforms.

[0054] Additionally, see Figure 11 and combined Figure 7The frequency-hopping bandstop filter also includes a control circuit board 15 with a central cutout, which is embedded in the coaxial resonant cavity and positioned above the metal resonant pillar without protruding from the coaxial resonant cavity. Each of the control circuits 141-148 is disposed on the control circuit board 15 and surrounds the digital capacitor array 13. A grounding metal disk 16 is disposed on the outer edge of the control circuit board 15 and surrounds the control circuit 14. The bias voltage and switching control voltage are embedded in a pre-set notch on the grounding metal disk 16, making the structure more compact.

[0055] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions as those in the present invention.

[0056] Although the subject matter has been described using language specific to structural features and / or methodological logic, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are merely illustrative examples of implementing the claims.

Claims

1. A frequency-hopping bandstop filter, characterized in that, include: A coaxial resonant cavity, a metal resonant pillar disposed inside the coaxial resonant cavity, and a digital capacitor array for frequency tuning; The digital capacitor array includes multiple capacitor chip groups, each capacitor chip group includes multiple capacitor chips, and each capacitor chip includes an upper electrode and a lower electrode arranged opposite to each other. The lower electrode is directly soldered to the end face of the metal resonant pillar, and the upper electrode is connected to a bonding wire for electrical connection with the control circuit.

2. The frequency-hopping bandstop filter according to claim 1, characterized in that, In the multiple sets of capacitor chips, the capacitance values ​​of each set of capacitor chips form a geometric sequence with a common ratio of n, where n is an integer greater than 1.

3. The frequency-hopping bandstop filter according to claim 2, characterized in that, When n is 2, the digital capacitor array is composed of four types of capacitor chips with a common ratio of 4. Each type of capacitor chip is provided in three, with two capacitor chips connected in parallel to form a capacitor chip group, and the other capacitor chip forming an independent capacitor chip group.

4. The frequency-hopping bandstop filter according to claim 3, characterized in that, Multiple capacitor chips of each type are distributed close to each other, and the four types of capacitor chips are arranged at intervals along the circumference of the metal resonant pillar.

5. The frequency-hopping bandstop filter according to claim 1, characterized in that, The capacitor chip is a single-layer dielectric plate capacitor, which includes a dielectric plate, and the upper electrode and the lower electrode are respectively disposed on the upper and lower surfaces of the dielectric plate.

6. The frequency-hopping bandstop filter according to claim 1, characterized in that, It also includes a control circuit, which is connected to the bonding wire and is used to control whether the corresponding capacitor chip is connected to the resonant circuit.

7. The frequency-hopping bandstop filter according to claim 6, characterized in that, The control circuit is provided in multiple ways, and each control circuit is connected to a capacitor chip group in a one-to-one correspondence.

8. The frequency-hopping bandstop filter according to claim 7, characterized in that, It also includes a control circuit board disposed within the coaxial resonant cavity, the control circuit board being positioned above the metal resonant pillar, and each of the control circuits being disposed on the control circuit board and surrounding the digital capacitor array.

9. The frequency-hopping bandstop filter according to claim 8, characterized in that, The control circuit includes a switching diode, which is a flat cylindrical bare chip. The two electrodes of the diode are respectively located on the upper and lower sides of the cylinder. One electrode is directly soldered to the pad of the control circuit board, and the other electrode is connected to another pad of the control circuit board through a bonding wire.

10. The frequency-hopping bandstop filter according to claim 9, characterized in that, The bonding wire is a bonding alloy wire.

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