Ultrahigh-frequency coupling structure giving consideration to electrostatic protection

Abstract

The invention relates to an ultrahigh frequency coupling structure giving consideration to electrostatic protection, which comprises an ESD protection circuit, a first coupler and a second coupler, the ESD protection circuit, the first coupler and the second coupler are connected in sequence, the ESD protection circuit receives an input low-frequency signal, and the second coupler is connected with an output port; the first coupler transmits a high-frequency signal to the main signal link, and the second coupler transmits the high-frequency signal to the output port. According to the ultrahigh-frequency coupling structure giving consideration to electrostatic protection, the straight-through design of the coupler is relatively simple, full-band signal passing can be easily achieved, it is often difficult to achieve that full-band coverage is achieved through the coupling end and the isolation end, different couplers can be combined at will, the design difficulty of the couplers is reduced, and the design cost of the couplers is reduced. And full coverage of higher frequency and even millimeter wave frequency bands is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of communication test instruments and meters, particularly to the radio frequency front-end field of a vector network analyzer, and specifically refers to an ultra-high frequency coupling structure that takes into account electrostatic protection. Background Art

[0002] The radio frequency front-end of a vector network analyzer usually has a directional coupler connected to a port to provide a radio frequency signal test interface. During use, external static electricity usually passes from the network analyzer port, through the coupler, and into the instrument, burning out the internal circuit and causing damage to the instrument.

[0003] With the development of millimeter-wave and even terahertz communication technologies, the frequency of vector network analyzers is getting higher and higher, and the radio frequency port frequency can reach above 100 GHz. Such a high frequency poses extremely high requirements for the port coupler. Taking a 110G network analyzer as an example, its operating frequency range is 10 MHz to 110 GHz, that is, the operating frequency range of the port coupler is also required to be 10 MHz to 110 GHz. Due to the structural characteristics of the coupler, it is very difficult to achieve such a wide octave, and there are almost no such wide coupler products on the market currently.

[0004] At the same time, with the increase in operating frequency, electrostatic protection of high-frequency signals becomes more difficult. Common anti-static measures such as shunting discharge devices, series impedance, and adding filter networks are used. Among them, shunting discharge devices such as TVS diodes are the most common. However, these common methods are mostly used for low-frequency and low-speed networks. For example, for a protection measure like a TVS diode, due to its structural process, its shunt-to-ground junction capacitance Cj will form a high-frequency-to-ground network, resulting in high-frequency signal mismatch, increased insertion loss, and deteriorated standing wave. Such measures usually cannot be applied to high-frequency links above 10G, making electrostatic protection of high-frequency links particularly difficult.

[0005] As Figure 1 , RFin is the signal input interface, RFout is the signal output interface, RFin reaches RFout through the coupler Coupler. Among them, the ESD protection circuit is shunted between RFin and the coupler Coupler and forms a shunt-to-ground capacitance Cj. Depending on the ESD scheme or device, Cj is usually between 0.1 pF and several hundred pF. According to the characteristics of capacitors passing high frequencies and blocking low frequencies, Cj provides a high-frequency signal path to the ground, thus causing high-frequency signal mismatch. Moreover, the internal electrostatic protection ability of high-frequency device chips is often weaker than that of low-frequency device chips, making high-frequency devices more easily damaged by static electricity. When operating in the high-frequency band, the internal high-frequency devices directly connect to the signal output port, and static electricity can also reach RFin along the signal path, thus burning out the internal circuit.

[0006] To solve this problem, the present invention proposes a novel coupling structure, which can not only solve the problem of port electrostatic protection but also not deteriorate the signal matching of the high-frequency link. Summary of the Invention

[0007] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a UHF coupling structure with electrostatic protection that features a simple structure, high reliability, and a wide range of applications.

[0008] To achieve the above object, the UHF coupling structure with electrostatic protection of the present invention is as follows:

[0009] The UHF coupling structure with electrostatic protection mainly includes an ESD protection circuit, a first coupler, and a second coupler. The ESD protection circuit, the first coupler, and the second coupler are connected in sequence. The ESD protection circuit receives the input low-frequency signal, and the second coupler is connected to the output port. The first coupler transmits the transmitted high-frequency signal to the main signal link, and the second coupler transmits the high-frequency signal to the output port.

[0010] Preferably, the ESD protection circuit includes a junction capacitance Cj, and the junction capacitance Cj conducts the electrostatic energy to the ground.

[0011] Preferably, the first coupler is a high-frequency band coupler that couples the working high-frequency band signal and attenuates the low-frequency band signal.

[0012] Preferably, the second coupler is a full-band working coupler, and the second coupler transmits both the low-frequency band signal directly connected to the main signal link and the high-frequency band signal coupled to the main signal link by the first coupler to the output port.

[0013] Preferably, the second coupler includes a low-frequency second coupler and a high-frequency third coupler. The low-frequency second coupler and the high-frequency third coupler are connected. The low-frequency second coupler is connected to the first coupler, and the high-frequency third coupler is connected to the output port. The low-frequency second coupler is used to couple out the low-frequency band signal for use by the subsequent circuit, and the high-frequency third coupler is used to couple out the high-frequency band signal for use by the subsequent circuit.

[0014] Preferably, the ESD protection circuit receives the low-frequency signal, the first coupler combines the low-frequency signal with the high-frequency signal coupled to the main signal link into a full-band signal, and the low-frequency second coupler and the high-frequency third coupler transmit the full-band signal to the signal output port.

[0015] Adopting the ultra-high frequency coupling structure with electrostatic protection of the present invention, the through design of the coupler is relatively simple, and it is relatively easy to achieve the passing of signals in the full frequency band. What is often difficult to achieve is the full-frequency coverage of the coupling end and the isolation end. Different couplers can be arbitrarily combined to reduce the design difficulty of the coupler and achieve full coverage in higher frequency and even millimeter wave frequency bands. The present invention is not limited to being only used in the RF front end of a vector network analyzer, but can also be used in the RF front ends of test and measurement instruments such as signal sources / signal analyzers. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of a common coupler and an electrostatic protection structure in the prior art.

[0017] Figure 2 It is a schematic diagram of the structure of the ultra-high frequency coupling structure with electrostatic protection of the present invention.

[0018] Figure 3 It is a schematic diagram of the structure of an embodiment of the ultra-high frequency coupling structure with electrostatic protection of the present invention. Detailed Embodiments

[0019] In order to be able to more clearly describe the technical content of the present invention, the following will be further described in conjunction with specific embodiments.

[0020] The ultra-high frequency coupling structure with electrostatic protection of the present invention includes an ESD protection circuit, a first coupler, and a second coupler. The ESD protection circuit, the first coupler, and the second coupler are connected in sequence. The ESD protection circuit receives the input low-frequency band signal, and the second coupler is connected to the output port; the first coupler transmits the transmitted high-frequency signal to the main signal link, and the second coupler transmits the high-frequency signal to the output port.

[0021] As a preferred embodiment of the present invention, the ESD protection circuit includes a junction capacitance Cj, and the junction capacitance Cj conducts the electrostatic energy to the ground.

[0022] As a preferred embodiment of the present invention, the first coupler is a high-frequency band coupler, which couples the working high-frequency band signal and attenuates the low-frequency band signal.

[0023] As a preferred embodiment of the present invention, the second coupler is a full-frequency band working coupler, and the second coupler transmits both the low-frequency band signal directly connected to the main signal link and the high-frequency band signal coupled to the main signal link by the first coupler to the output port.

[0024] As a preferred embodiment of the present invention, the second coupler includes a low-frequency second coupler and a high-frequency third coupler. The low-frequency second coupler and the high-frequency third coupler are connected. The low-frequency second coupler is connected to the first coupler, and the high-frequency third coupler is connected to the output port. The low-frequency second coupler is used to couple out low-frequency signals for use by the subsequent circuit, and the high-frequency third coupler is used to couple out high-frequency signals for use by the subsequent circuit.

[0025] As a preferred embodiment of the present invention, the ESD protection circuit receives low-frequency signals, and the first coupler combines the low-frequency signals with the high-frequency signals coupled to the main signal link into full-band signals. The low-frequency second coupler and the high-frequency third coupler transmit the full-band signals to the signal output port.

[0026] In the specific embodiment of the present invention, the ultra-high-frequency coupling structure that takes into account electrostatic protection improves the traditional coupler structure, combines low-frequency electrostatic protection measures, and cuts off the high-frequency electrostatic path, which can not only achieve electrostatic protection in the full band but also not deteriorate the high-frequency signal quality, thus ensuring the reliability of the full-band operation of the RF port.

[0027] Because port static electricity is everywhere, an electrostatic protection device must be provided. To avoid affecting high-frequency signals by adding an electrostatic protection device, the input full-band RF signal RFin is divided into a low-frequency signal (RF LF) and a high-frequency signal (RF HF) here, as Figure 2 . The RF LF to the output port RFout is the main signal link. The RF LF signal passes through the ESD protection circuit, the first coupler (Coupler1), and the second coupler (Coupler2) in sequence and reaches RFout.

[0028] According to the scheme of the ESD protection circuit or the size of the junction capacitance Cj of the selected ESD device, the input signal RFin can be frequency-band divided, and a suitable segmentation frequency point can be selected to separate the low-frequency signal RF LF and the high-frequency signal RF HF. The low-frequency signal reaches the signal output port RFout through the main signal link. At this time, the junction capacitance Cj in the ESD protection circuit presents a high impedance state to the low-frequency signal, thus having no influence on the low-frequency signal. At the same time, the electrostatic energy is conducted to the ground through the ESD protection circuit, playing a role in protecting the internal circuit.

[0029] The high-frequency signal RF HF passes through the first coupler (Coupler1) to the main signal link, then through the second coupler (Coupler2), and reaches the RF signal output port RFout. The main signal link is a full-band passable link, and only the insertion loss needs to be minimized as much as possible during design. Due to the reciprocity of the coupler, the high-frequency signal RF HF can be coupled to the main signal link, and the low-frequency signal on the main signal link can also be coupled to the high-frequency signal link. To reduce the influence of the low-frequency coupled signal on the high-frequency signal link, the first coupler (Coupler1) can be designed as a high-frequency band coupler, that is, it only couples the working high-frequency band signal and attenuates the low-frequency band signal. After attenuation, there will still be a weak signal of the low-frequency band coupled to the RF HF link and absorbed by the 50Ω load. At the same time, the remaining energy after the RF HF is coupled to the main signal link is also absorbed by the 50Ω load.

[0030] As a high-frequency band coupler rather than a full-band coupler, the first coupler (Coupler1) can not only reduce the design difficulty of the first coupler (Coupler1), but also disconnect the physical path of the electrostatic energy reaching the high-frequency signal device, playing a role in protecting the high-frequency device and ensuring the stability and reliability of the entire circuit.

[0031] The second coupler (Coupler2) is a full-band working coupler, and can pass the low-frequency band signal RF LF directly connected through the main signal link and the high-frequency band signal RF HF coupled to the main signal link through the first coupler (Coupler1). According to the design requirements, if the second coupler (Coupler2) can meet the full-band signal working requirements, only the second coupler (Coupler2) is needed. As the high-frequency frequency further increases, it is difficult for one coupler to cover the full band. At this time, the second coupler (Coupler2) needs to be split and designed, such as Figure 3 .

[0032] Such as Figure 3 , on the basis of Figure 2 , the second coupler (Coupler2) is split into a low-frequency second coupler (LF Coupler) and a high-frequency third coupler (HF Coupler). The segmentation frequency point 2 of the low-frequency second coupler (LF Coupler) and the high-frequency third coupler (HF Coupler) here can be different from the segmentation frequency point 1 of the low-frequency signal RF LF and the high-frequency signal RF HF. The segmentation frequency point 1 is determined based on the frequency that the ground capacitance Cj of the ESD protection circuit can affect; the segmentation frequency point 2 is determined based on the design difficulty of the low-frequency second coupler (LF Coupler) and the high-frequency third coupler (HF Coupler).

[0033] Such as Figure 3, after the low-frequency signal RF LF passes through the ESD protection circuit, it merges with the high-frequency signal RF HF coupled to the main signal link at the first coupler (Coupler1) to form a full-band signal RFall. The full-band signal RFall reaches the signal output port RFout through the low-frequency second coupler (LF Coupler) and the high-frequency third coupler (HF Coupler). At the same time, at the segmented frequency point 2, the low-frequency second coupler (LF Coupler) couples out the low-frequency band signal for use by the subsequent circuit, and the high-frequency third coupler (HF Coupler) couples out the high-frequency band signal for use by the subsequent circuit.

[0034] As Figure 3 , by segmenting the radio frequency signal into a low-frequency band signal RF LF and a high-frequency band signal HF, the physical path for static electricity to reach the high-frequency signal device is cut off, protecting the high-frequency signal from damage by static electricity energy. The ESD protection circuit is directly added to the low-frequency signal RF LF path, which can absorb most of the static electricity energy without affecting the signal quality. At the same time, since the internal static electricity protection ability of the chip of the low-frequency device is better than that of the chip of the high-frequency device, the static electricity protection ability of the full screen segment is qualitatively improved.

[0035] The technical solution of the present invention focuses on the millimeter-wave band. By separating the millimeter-wave signal through a millimeter-wave coupler, the millimeter-wave signal circuit is isolated from the low-frequency static circuit path materials, realizing low-frequency static electricity protection, solving the interference and deterioration of the low-frequency static electricity protection device to the millimeter-wave signal, and at the same time, through this solution, the working frequency band of the millimeter-wave signal can be extended to more than 100G.

[0036] For the specific implementation solution of this embodiment, reference can be made to the relevant descriptions in the above embodiments, which will not be elaborated here.

[0037] It can be understood that the same or similar parts in the above embodiments can be referred to each other, and the content not detailed in some embodiments can be referred to the same or similar content in other embodiments.

[0038] It should be noted that in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "a plurality" refers to at least two.

[0039] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0040] Adopting the ultra-high frequency coupling structure that takes into account electrostatic protection of the present invention, the through design of the coupler is relatively simple and it is relatively easy to achieve full-band signal passing. What is often more difficult to achieve is to cover the full frequency band at the coupling end and the isolation end. Different couplers can be arbitrarily combined to reduce the design difficulty of the coupler and achieve full coverage of higher frequencies and even millimeter wave bands. The present invention is not limited to being only used in the RF front end of a vector network analyzer, and can also be used in the RF front ends of test and measurement instruments such as signal sources / signal analyzers.

[0041] In this specification, the present invention has been described with reference to its specific embodiments. However, it is obvious that various modifications and transformations can still be made without departing from the spirit and scope of the present invention. Therefore, the specification and the drawings should be regarded as illustrative rather than restrictive.

Claims

1. An ultra-high frequency coupling structure taking into account electrostatic protection, characterized in that: The structure includes an ESD protection circuit, a first coupler and a second coupler, which are connected in sequence. The ESD protection circuit receives an input low-frequency signal, and the second coupler is connected to an output port; the first coupler transmits a high-frequency signal to a main signal link, and the second coupler transmits the high-frequency signal to the output port.

2. The ultra-high frequency coupling structure with electrostatic protection according to claim 1, characterized in that: The ESD protection circuit includes a junction capacitor Cj, and the junction capacitor Cj conducts the electrostatic energy to the ground.

3. The ultra-high frequency coupling structure with electrostatic protection according to claim 1, characterized in that: The first coupler is a high-frequency band coupler, which couples the working high-frequency band signal and attenuates the low-frequency band signal.

4. The ultra-high frequency coupling structure with electrostatic protection according to claim 1, characterized in that: The second coupler is a full-band working coupler, and the second coupler transmits both the low-band signal directly connected to the main signal link and the high-band signal coupled to the main signal link via the first coupler to the output port.

5. The ultra-high frequency coupling structure with electrostatic protection as claimed in claim 1, characterized in that: The second coupler includes a low-frequency second coupler and a high-frequency third coupler, the low-frequency second coupler and the high-frequency third coupler are connected, the low-frequency second coupler is connected to the first coupler, and the high-frequency third coupler is connected to the output port. The low-frequency second coupler is used to couple out a low-frequency band signal for use by a subsequent circuit, and the high-frequency third coupler is used to couple out a high-frequency band signal for use by a subsequent circuit.

6. The ultra-high frequency coupling structure with electrostatic protection as claimed in claim 4, characterized in that: The ESD protection circuit receives a low-frequency signal, the first coupler combines the low-frequency signal with the high-frequency signal coupled to the main signal link into a full-band signal, and the low-frequency second coupler and the high-frequency third coupler transmit the full-band signal to the signal output port.

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