Self-adaptive amplitude limiter and amplitude limiting method thereof

Abstract

According to the self-adaptive amplitude limiter, a PIN diode is additionally arranged on a defected ground structure to form parallel LC resonance and generate the effect of a band elimination filter, the state of the PIN diode changes along with input power so as to change the resonant frequency of the parallel LC resonance, normal working signals are not affected, and meanwhile the amplitude limiting effect of the band elimination filter is achieved. The self-adaptive working state is changed, the electromagnetic protection of high-power signals is realized, and the safety of electronic equipment is protected. Meanwhile, the amplitude limiting threshold can be increased by cascading the amplitude limiters, and the threshold power can be adjusted by adding bias current so as to adapt to different application scenes; besides, the structure parameters of the amplitude limiter are changed, so that the amplitude limiter can work in different frequency bands, and the universality of the amplitude limiter is improved. Compared with a traditional amplitude limiter, the amplitude limiter has the advantages that insertion loss is low in passband, and high isolation performance is achieved under high power.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic devices, and in particular relates to an adaptive limiter. Background Art

[0002] With the continuous development of electronic information technology, the integration of electronic equipment is getting higher and higher, and the size of devices is gradually getting smaller, which makes electronic equipment more sensitive to energy changes. High-power electromagnetic waves can interfere with or even damage sensitive receivers, sensors and other equipment in communication or radar systems. Therefore, it is necessary to perform electromagnetic strengthening on electronic systems.

[0003] A limiter is an attenuator that can control the attenuation amount according to the input power. For RF electronic systems, the limiter not only needs to attenuate or isolate the incident wave that exceeds the power threshold, but also needs to achieve low insertion loss when transmitting signals that do not reach the power threshold.

[0004] At present, the limiters are mainly divided into ferrite-based limiters and diode-based limiters; the following are four types of ferrite-based and diode-based limiters: (1) A frequency selective limiter is realized using a stripline structure made of epitaxially grown magnetized ferrite film.

[0005] like Figure 1 As shown, using nonlinear excitation of magnetic spin waves in magnetized ferrite, a microwave signal coupled to a magnetized ferrite sample produces a substantially linear, low-loss response in the ferrite at low signal levels, and above a critical RF magnetic field strength, the nonlinearity of the precession of magnetic dipoles in the ferrite becomes strong enough to overcome natural losses, and energy begins to be transferred exponentially to short-wavelength subharmonic spin waves. These half-frequency spin waves can easily transfer energy to the lattice, so that the excess RF power is dissipated in the ferrite as heat to achieve the function of a limiter.

[0006] (2) Microwave frequency-selective limiter using electron paramagnetic resonance (EPR) By applying an inhomogeneous static magnetic field to the EPR material, the resonant lines can be widened to allow independent limiting of frequency components within a bandwidth much larger than the intrinsic EPR linewidth. For the EPR limiter, two identical cavities containing paramagnetic material are arranged as alternating arms in a microwave bridge. One cavity is immersed in an inhomogeneous static magnetic field. The field is adjusted so that the Larmor resonant frequency lies within the bandwidth of the loaded cavity, thereby unbalancing the bridge circuit. If the input power exceeds the saturation power level of the paramagnetic material, the bridge is driven to a state closer to equilibrium and the output power is limited.

[0007] If low saturation power levels are to be achieved, EPR materials with long relaxation times must be used for limiter applications. The transverse relaxation time is related to the EPR linewidth and determines the minimum frequency separation (selectivity) at which independent limiting of two simultaneously incident signals occurs.

[0008] (3) Frequency-selective limiting circuit based on nonlinear matching reflection mode band-stop resonator like Figure 2 As shown, a passive band-stop resonator loaded with a nonlinear semiconductor device is used. Since the resistance of the diode can be controlled by the input RF power level, its response can change from full pass to band stop according to the RF power. The diode enables the resonator's stop-band attenuation to vary with RF power, thereby determining the limiting threshold of the band-stop limiter.

[0009] (4) Three-port absorptive limiter This circuit uses the switching characteristics of ordinary diodes to switch between non-limiting and absorbing limiting states. In this design, the limiting state occurs when both diodes are on, and the full-on state occurs when the diodes are off.

[0010] The limiter based on magnetized ferrite is large in size, relatively expensive, and has limited restrictions on high-power signals; while the limiter based on diode is difficult to adjust the limiter threshold voltage. 2.45GHz is one of the commonly used ISM bands and one of the bands for wireless energy transmission. Wireless energy transmission is a way to wirelessly power electronic devices and often requires higher power. Therefore, it is necessary to design an electromagnetic protection device that works at 2.45GHz and has low insertion loss characteristics at low power and high isolation characteristics at high power. Summary of the invention

[0011] The object of the present invention is to provide an adaptive limiter and a limiting method thereof, so as to solve the problems of low power bearing and complex structure of the existing limiter.

[0012] In the first aspect, the present invention provides an adaptive limiter, which includes a dielectric layer, and a metal defect ground structure and a microstrip line printed on both sides of the dielectric layer. The metal defect ground structure includes an annular metal unit in the outer circle and a rectangular metal unit in the inner circle; an annular gap is formed between the annular metal unit and the rectangular metal unit; a PIN diode and a lumped capacitor are provided in the annular gap. The anode of the PIN diode is connected to the rectangular metal unit; the cathode of the PIN diode is connected to the annular metal unit; and the two ends of the lumped capacitor are connected to the rectangular metal unit and the annular metal unit, respectively.

[0013] Preferably, the structural parameters and lumped capacitance of the metal defect ground structure are adjusted according to the target frequency so that the operating frequency of the adaptive limiter is equal to the target frequency. The structural parameters of the metal defect ground structure include the length of each side of the metal defect ground structure and the width of the annular gap.

[0014] Preferably, the dielectric layer adopts a planar substrate. The metal defect ground structure and the microstrip line are respectively arranged on two side planes of the dielectric layer, and the microstrip line is aligned with the rectangular metal unit.

[0015] Preferably, the dielectric layer is in a ring structure; the microstrip line is arranged on the inner side of the dielectric layer; and the metal defect structure is arranged on the outer side of the dielectric layer.

[0016] Preferably, the operating frequency of the adaptive limiter is 2.45GHz; the structural parameters of the metal defect structure are: the length of the outer long side of the annular metal unit is 25mm, and the length of the outer short side is 20mm; the length of the rectangular metal unit is 6.87mm, the width is 5.34mm, and the long side of the rectangular metal unit is parallel to the short side of the annular metal unit. The length of the outer long side of the annular gap is 9.72mm, and the length of the outer short side is 6.89mm; the width of the wider long side of the annular gap is 0.92mm, and the width of the narrower long side is 0.63mm; the long side of the annular gap is parallel to the short side of the annular metal unit, the width of the short side of the annular gap is equal, and the spacing between the outer short side and the outer long side of the annular metal unit is the same; the spacing between the wider outer long side of the annular gap and the outer short side of the annular metal unit is 6.98mm, and the spacing between the narrower outer long side and the outer short side of the annular metal unit is 11.13mm; through the above structural parameters. The length of the microstrip line is 25 mm and the width is 1.88 mm.

[0017] Preferably, the PIN diode and the lumped capacitor are respectively arranged on two opposite sides of the annular gap.

[0018] Preferably, the annular gap is formed by two long sides and two short sides arranged opposite to each other, which are connected alternately in sequence. The widths of the two long sides are not equal. The PIN diode is arranged at the center of the longer side with a larger width in the annular gap, and the lumped capacitor is arranged at the center of the narrower longer side of the annular gap.

[0019] In a second aspect, the present invention provides an adaptive limiting device, which includes a plurality of the aforementioned adaptive limiters. The microstrip lines in each adaptive limiter are connected in series in sequence; the rectangular metal units in each adaptive limiter are connected to the same voltage. The plurality of adaptive limiters connected in series can increase the limiting threshold of the adaptive limiting device.

[0020] Preferably, each adaptive limiter shares a same dielectric layer; and the microstrip lines in each adaptive limiter are different parts of the same rectangular microstrip line.

[0021] In a third aspect, the present invention provides an adaptive clipping method, which uses the above-mentioned adaptive clipper. The clipping method is as follows: If the input electromagnetic signal strength is less than the threshold power, the limiter is in the transmission state, the PIN diode is in the disconnected state, and the equivalent capacitance C of the PIN diode, the lumped capacitance, and the metal defect ground structure G and inductor L G A parallel resonator is formed; the resonance frequency of the parallel resonator is higher than the operating frequency, the limiter does not attenuate the input electromagnetic signal strength, and the output power increases linearly with the increase of the input signal; If the input electromagnetic signal strength is greater than or equal to the threshold power and less than or equal to the limiting threshold, the limiter is in an isolated state, the PIN diode is in a conducting state, the annular metal unit and the rectangular metal unit are in a connected state, and the equivalent capacitance C of the metal defect ground structure is G Increases, the resonant frequency moves to the operating frequency, the limiter limits the input electromagnetic signal to the threshold power, and the output power remains basically unchanged.

[0022] If the input electromagnetic signal strength is greater than the limiting threshold, the limiter's attenuation of the input signal remains unchanged, and the output power increases linearly as the input signal increases.

[0023] Preferably, if the input electromagnetic signal strength is less than the threshold power, the resonant frequency is determined by the lumped capacitance value, the junction capacitance value of the diode, and the lengths and widths of the sides of the annular gap in the metal defect ground structure.

[0024] As a preference, when the input electromagnetic signal strength is greater than the threshold power and less than the limiting threshold, as the input electromagnetic signal strength increases, the forward resistance R in the PIN diode increases. F As the current flowing through the PIN diode increases, it gradually decreases, the resonance strength of the parallel resonance increases, and the suppression of the signal gradually increases.

[0025] Preferably, a DC bias is added to the rectangular metal unit, and the threshold power of the limiter is changed by changing the DC power required to turn on the diode through the DC bias.

[0026] The present invention has the following beneficial effects: 1. The present invention adds a PIN diode to the defective ground structure to form a parallel LC resonance, which produces a band-stop filter effect. The state of the PIN diode changes with the input power to change the resonant frequency of the parallel LC resonance. Without affecting the normal working signal, the working state of the PIN diode is adaptively changed to achieve electromagnetic protection against high-power signals and protect the safety of electronic equipment.

[0027] 2. The present invention can increase the limiting threshold by cascading the limiters, and can adjust the threshold power by adding a bias current to adapt to different application scenarios; at the same time, by changing the limiter structure parameters, the limiter can operate in different frequency bands, thereby improving the versatility of the present invention.

[0028] 3. Compared with the traditional limiter, the present invention has lower insertion loss in the passband and higher isolation performance at high power. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a limiter based on magnetized ferrite film.

[0030] Figure 2 Schematic diagram of the frequency selection limiting circuit based on nonlinear matching reflection mode band-stop resonator.

[0031] Figure 3 It is a schematic diagram of the overall structure of the present invention.

[0032] Figure 4 It is a schematic diagram of an equivalent circuit model of the present invention.

[0033] Figure 5 It is a working state flow chart of the present invention.

[0034] Figure 6 It is a schematic diagram of the power change of the input signal after passing through the limiter in the present invention.

[0035] Figure 7 Schematic diagram of the limiter of the present invention in an isolated state; wherein, (a) is a schematic diagram of the spectrum of the input signal before passing through the limiter; (b) is a schematic diagram of the transmission parameters of the limiter; and (c) is a schematic diagram of the spectrum of the signal after being limited by the limiter.

[0036] Figure 8 It is a schematic diagram of transmission parameters of the limiter under different input powers in the present invention.

[0037] Fig. 9 The schematic diagram of the cascade limiter after adding DC bias in the present invention.

[0038] Fig.10 It is a schematic diagram of transmission parameters of the limiter in different working states in the present invention.

[0039] Fig.11 The following is a comparison chart of output power with and without limiter as a function of signal source power.

[0040] Figure numerals: 1. dielectric layer; 2. metal defect ground structure; 3. microstrip line; 4. annular metal unit; 5. rectangular metal unit; 6. annular gap; 7. PIN diode; 8. lumped capacitor. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] like Figure 3 As shown, an adaptive limiter includes a dielectric layer 1 and a metal defect ground structure 2 and a microstrip line 3 respectively printed on two sides of the dielectric layer 1. The dielectric layer 1 is made of RO4350, the dielectric constant of the dielectric layer 1 is 3.66, and the thickness is 0.762mm; the metal defect ground structure 2 includes an annular metal unit 4 in the outer circle and a rectangular metal unit 5 in the inner circle; the length L of the outer long side of the annular metal unit 4 is 25mm, and the length W of the outer short side is 20mm; the long side of the rectangular metal unit 5 is parallel to the short side of the annular metal unit 4, the length W2 of the rectangular metal unit 5 is 6.87mm, and the width L2 is 5.34mm. An annular gap 6 is formed between the annular metal unit 4 and the rectangular metal unit 5, and the long side of the annular gap 6 is parallel to the short side of the annular metal unit 4; the length W1 of the outer long side of the annular gap 6 is 9.72 mm, and the length L1 of the outer short side is 6.89 mm; the short sides of the annular gap 6 have equal widths, and the long sides have different widths, the wider long side has a width of 0.92 mm, and the narrower long side has a width of 0.63 mm; the outer short side of the annular gap 6 has the same spacing as the outer long side of the annular metal unit 4, the spacing between the wider outer long side of the annular gap 6 and the outer short side of the annular metal unit 4 is 6.98 mm, and the spacing between the narrower outer long side and the outer short side of the annular metal unit 4 is 11.13 mm. A PIN diode 7 is provided at the center of the wider long side of the annular gap 6, and the anode of the PIN diode 7 is connected to the rectangular metal unit 5. The PIN diode 7 uses BAR6402. A lumped capacitor 8 is provided at the center of the narrower long side of the annular gap 6, and the two ends of the lumped capacitor 8 are respectively connected to the rectangular metal unit 5 and the annular metal unit 4. Through the structural parameters of the above-mentioned metal defect ground structure 2 and the lumped capacitor 8, the operating frequency of the limiter is 2.45GHz. The microstrip line 3 is rectangular, with a length of 25mm and a width W3 of 1.88mm, which is used to connect the input end, the output end and the limiter, and ensure the stable performance of the limiter.

[0043] In this embodiment, the dielectric layer 1 adopts a planar substrate; the metal defect ground structure 2 and the microstrip line 3 are respectively arranged on two side planes of the dielectric layer 1 .

[0044] In some embodiments, the dielectric layer 1 is in a ring structure; the microstrip line 3 is arranged on the inner side of the dielectric layer 1; and the metal defect ground structure 2 is arranged on the outer side of the dielectric layer 1 to form a coaxial line structure.

[0045] The equivalent circuit model of the adaptive limiter is as follows: Figure 4 As shown. PIN diode 7 is equivalent to a parallel junction resistance R j and junction capacitance Cj Connect a forward resistor R in series F ; Lumped capacitance C 1 and junction capacitance C j The capacitance value is different; the metal defect structure 2 is equivalent to the parallel inductance L G and capacitor C G The PIN diode 7 and the lumped capacitor 8 are connected in series, and the metal defect ground structure 2 is connected in parallel to the input and output respectively.

[0046] like Figure 5 and Figure 6 As shown, the limiting principle of the adaptive limiter is as follows: (1) When the input electromagnetic signal strength is less than the threshold power, the limiter is in the transmission state and the junction resistance R j Approaches infinity, and the PIN diode 7 is in the disconnected state. At this time, the PIN diode 7 can be simply regarded as a capacitor; the junction capacitance C j , Lumped capacitance C 1 , capacitor C G and inductor L G A parallel resonator is formed, the resonant frequency is much higher than the operating frequency, the input electromagnetic signal can pass freely, that is, the operating frequency is within the passband of the limiter, the limiter does not attenuate the input electromagnetic signal strength, the output power increases linearly with the input signal enhancement, and the electronic information system with the limiter can work normally; at this time, the position of the resonant frequency is jointly determined by the lumped capacitance value, the junction capacitance value of the diode, and the length and width of each side of the annular gap in the metal defect ground structure.

[0047] (2) If Figure 7 As shown in the figure, when the input electromagnetic signal strength is greater than the threshold power and less than the limiting threshold, the limiter is in the isolation state, R j Approaching zero, C j By R j The PIN diode 7 is in the on state, and the PIN diode 7 can be simply regarded as a small resistor; the annular metal unit 4 and the rectangular metal unit 5 are in the connected state, and the equivalent capacitance C of the metal defect structure G As the value increases, the resonant frequency moves to 2.45 GHz, and the operating frequency is within the stop band of the limiter. Figure 8 As shown in the figure, as the input electromagnetic signal strength increases, the forward resistance R F As the current flowing through the PIN diode 7 increases, it gradually decreases, the resonance strength of the parallel resonance increases, and the suppression of the signal gradually increases. The limiter limits the input electromagnetic signal to near the threshold power, and the output power remains basically unchanged.

[0048] In some embodiments, a DC bias is added to the rectangular metal unit 5 to control the voltage difference across the diode in a zero input state and change the DC power required to turn on the diode, that is, the threshold power of the limiter is changed by adding a DC bias.

[0049] (3) When the input electromagnetic signal strength exceeds the limiting threshold, the attenuation amplitude of the limiter on the input signal remains unchanged, and the output power increases linearly with the increase of the input signal.

[0050] like Fig. 9 As shown, in some embodiments, the microstrip lines 3 in multiple adaptive limiters are connected in series in sequence; the rectangular metal unit 5 in each adaptive limiter is connected to the same voltage to adjust the threshold power. Multiple adaptive limiters connected in series can increase the limiting threshold of the adaptive limiting device. Each adaptive limiter shares the same dielectric layer 1; the microstrip lines 3 in each adaptive limiter are different parts of the same rectangular microstrip line.

[0051] The transmission parameters of the limiter in the isolation state and the transmission state are as follows: Figure 8 As shown, the dotted line represents the transmission state and the solid line represents the isolation state. Fig.10 It can be seen that the difference between the transmission curve in the transmission state and the isolation state is at least 10dB, which can effectively control the strength of the transmission signal. When the limiter is in the transmission state, it is in the signal passband, and the transmission coefficient is greater than -1.5dB. At this time, the electromagnetic signal can pass normally. When the limiter is in the isolation state, the signal passband is closed, the transmission coefficient can reach less than -20dB, the electromagnetic wave is reflected, and the electronic equipment is effectively protected.

[0052] like Fig.11 As shown in the figure, the output power of the amplifier with and without the limiter is tested as the signal source power changes; the gain of the amplifier is 32dB; Fig.11 It can be seen that when there is no limiter, the output power and the signal source power are linearly related; when there is a limiter, the output power gradually reaches saturation at 38dBm.

[0053] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. An adaptive limiter, characterized in that: The invention comprises a dielectric layer (1), and a metal defect ground structure (2) and a microstrip line (3) respectively printed on two sides of the dielectric layer (1); the metal defect ground structure (2) comprises an annular metal unit (4) in an outer circle and a rectangular metal unit (5) in an inner circle; an annular gap (6) is formed between the annular metal unit (4) and the rectangular metal unit (5); a PIN diode (7) and a lumped capacitor (8) are arranged in the annular gap (6); the anode of the PIN diode (7) is connected to the rectangular metal unit (5); the cathode of the PIN diode (7) is connected to the annular metal unit (4); and the two ends of the lumped capacitor (8) are respectively connected to the rectangular metal unit (5) and the annular metal unit (4).

2. An adaptive limiter according to claim 1, characterized in that: The dielectric layer (1) adopts a planar substrate; the metal defect ground structure (2) and the microstrip line (3) are respectively arranged on two side planes of the dielectric layer (1); the microstrip line (3) is aligned with the rectangular metal unit (5).

3. The adaptive limiter according to claim 1, characterized in that: The dielectric layer (1) is in a ring structure; the microstrip line (3) is arranged on the inner side of the dielectric layer (1); and the metal defect structure (2) is arranged on the outer side of the dielectric layer (1).

4. The adaptive limiter according to claim 1, characterized in that: The structural parameters of the metal defect ground structure (2) and the lumped capacitance (8) are adjusted according to the target frequency so that the operating frequency of the adaptive limiter is equal to the target frequency; The structural parameters of the metal defect ground structure (2) include the length of each side of the metal defect ground structure (2) and the width of the annular gap (6); the annular gap (6) is formed by two long sides arranged opposite to each other and two short sides arranged opposite to each other, which are connected alternately in sequence; the widths of the two long sides are unequal; the PIN diode (7) is arranged at the center of the longer side with a larger width in the annular gap (6), and the lumped capacitor (8) is arranged at the center of the narrower long side of the annular gap (6).

5. An adaptive limiter according to claim 4, characterized in that: The operating frequency of the adaptive limiter is 2.45 GHz; the structural parameters of the metal defect ground structure (2) are as follows: the length of the outer long side L of the annular metal unit (4) is 25 mm, and the length of the outer short side is 20 mm; the length of the rectangular metal unit (5) is 6.87 mm, and the width is 5.34 mm, and the long side of the rectangular metal unit (5) is parallel to the short side of the annular metal unit (4); the length of the outer long side of the annular gap (6) is 9.72 mm, and the length of the outer short side is 6.89 mm; the width of the wider long side of the annular gap (6) is 0.92 mm m, the width of the narrower long side is 0.63 mm; the long side of the annular gap (6) is parallel to the short side of the annular metal unit (4), the short side of the annular gap (6) has the same width, and the outer short side has the same spacing as the outer long side of the annular metal unit (4); the spacing between the wider outer long side of the annular gap (6) and the outer short side of the annular metal unit (4) is 6.98 mm, and the spacing between the narrower outer long side and the outer short side of the annular metal unit (4) is 11.13 mm; through the above structural parameters; the length of the microstrip line (3) is 25 mm, and the width is 1.88 mm.

6. An adaptive limiting device, characterized in that: The invention comprises a plurality of adaptive limiters as claimed in claim 1; the microstrip lines (3) in each adaptive limiter are connected in series in sequence.

7. The adaptive limiting device according to claim 6, characterized in that: Each adaptive limiter shares the same dielectric layer (1); and the microstrip lines (3) in each adaptive limiter are different parts of the same rectangular microstrip line.

8. An adaptive limiting method, characterized in that: Using the adaptive limiter described in claim 1, the limiting method is as follows: If the input electromagnetic signal strength is less than the threshold power, the limiter is in the transmission state, the PIN diode (7) is in the disconnected state, and the equivalent capacitance C of the PIN diode (7), the lumped capacitor (8) and the metal defect ground structure (2) is G and inductor L G A parallel resonator is formed; the resonance frequency of the parallel resonator is higher than the operating frequency, the limiter does not attenuate the input electromagnetic signal strength, and the output power increases linearly with the increase of the input signal; If the input electromagnetic signal strength is greater than or equal to the threshold power and less than or equal to the limiting threshold, the limiter is in an isolated state, the PIN diode (7) is in a conducting state, the annular metal unit (4) and the rectangular metal unit (5) are in a connected state, and the equivalent capacitance C of the metal defect ground structure (2) is G Increase, the resonant frequency moves to the operating frequency, the limiter limits the input electromagnetic signal to the threshold power, and the output power remains basically unchanged; If the input electromagnetic signal strength is greater than the limiting threshold, the attenuation amplitude of the limiter on the input signal remains unchanged, and the output power increases linearly as the input signal increases.

9. The adaptive limiting method according to claim 8, characterized in that: If the input electromagnetic signal strength is less than the threshold power, the resonant frequency is determined by the lumped capacitance value, the junction capacitance value of the diode, and the lengths and widths of each side of the annular gap (6).

10. The adaptive limiting method according to claim 8, characterized in that: A DC bias is added to the rectangular metal unit (5), and the DC bias changes the DC power required to turn on the diode, thereby changing the threshold power of the limiter.

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