TW202416497A - Esd protection circuit for rf transmission - Google Patents

Abstract

ESD Protection Circuit for RF Transmission is suitable for connecting a radio frequency transmission line. It includes a signal connection end and an electrostatic protection module. The signal connection end is arranged in the radio frequency transmission line. The electrostatic protection module includes an electrostatic protection element and an inductance element. The electrostatic protection element has a PN junction structure. One end of the electrostatic protection element and the inductance element is electrically connected to the signal connection end. The electrostatic protection element and the other end of the inductance element are grounded. The electrostatic protection element and the inductance element are one of impedance matching or filtering functional elements, thereby preventing the anti-static protection circuit from generating an equivalent capacitance, so as to further maintain the gain of the radio frequency signal in the circuit.

Description

Anti-static protection circuit for RF transmission

The present invention relates to an anti-static protection circuit, in particular to an anti-static protection circuit used for radio frequency transmission in a single crystal microwave integrated circuit (MMIC).

Traditional anti-static protection circuits mainly use PN junctions to achieve electrostatic discharge (ESD) damage, which can effectively avoid static leakage current and have a static discharge path. Please refer to Figure 1, which is the Republic of China Patent I766656, which describes an electrostatic discharge protection circuit. One end of a data line 111 and a ground line 112 are respectively a connection end 121 and a connection end 122. The connection end 121 and the connection end 122 are used to connect an electronic component (such as a USB transmission port). The other end of the data line 111 and the ground line 112 are respectively a connection end 131 and a connection end 132. The terminal 131 and the connection terminal 132 are used to connect to another electronic component (such as the transmission pin of an IC). A series protection circuit 141 is set on the data line 111, and a PN junction electronic component 151 is set between the connection terminal 121 and the connection terminal 122. When the device works normally, the state of the series protection circuit 141 is short-circuited, and the state of the PN junction electronic component 151 is open-circuited (disconnected or having a large resistance value), which enables the data of the connection terminal 121 to be transmitted to the connection terminal 131. When electrostatic discharge (Electrostatic discharge) occurs, When an ESD event occurs, the state of the PN junction electronic element 151 changes to a conducting state, and its resistance value is greatly reduced to allow the ESD current to be conducted to the ground line 112, and the state of the series protection circuit 141 changes to an open circuit to protect the USB-connected device or IC from being damaged by ESD.

Although conventional technology provides an ESD protection circuit, in order for an ESD protection circuit formed using a PN junction to have better electrostatic protection, the area of the PN junction must be large enough to conduct sufficient electrostatic discharge current when in the on state. However, when the area of the PN junction increases, it will cause a capacitive effect in the off state. In addition, traditional ESD protection circuits only consider the charging and discharging of charges, and do not consider impedance matching on the radio frequency (RF) path.

In a single crystal microwave integrated circuit (MMIC), the radio frequency (RF) signal transmitted in the circuit is very sensitive to the capacitance generated in the circuit, which will cause RF attenuation. Therefore, the equivalent capacitance of the anti-static circuit structure of the PN junction set on the path of transmitting the RF signal cannot be too large. If the equivalent capacitance of the PN junction is larger, the influence on the characteristics of the RF signal will be greater. This effect will also be greater as the frequency of the RF signal increases, for example, it will cause a greater reduction in gain.

Therefore, how to provide basic electrostatic discharge without causing excessive attenuation of the transmitted signal is a goal that relevant technical personnel urgently need to work hard on.

In view of this, the purpose of the present invention is to provide an anti-static protection circuit for radio frequency transmission, which is suitable for connecting a radio frequency transmission line, and the main purpose is to prevent the radio frequency signal in the radio frequency transmission line from attenuating.

The anti-static protection circuit for radio frequency transmission includes a signal connection terminal and an electrostatic protection module.

The signal connection end is arranged in the radio frequency transmission line.

The electrostatic protection module includes an electrostatic protection element and an inductor element. The electrostatic protection element has a PN junction structure. One end of the electrostatic protection element and the inductor element is electrically connected to the signal connection end. The other end of the electrostatic protection element and the inductor element is grounded. The electrostatic protection element and the inductor element are used for one of impedance matching or filtering.

Another technical means of the present invention is that the electrostatic protection element and the inductor element are connected in parallel.

Another technical means of the present invention is that the anti-static protection circuit for radio frequency transmission further includes a DC isolation capacitor, the DC isolation capacitor and the inductor element are in series connection, and the DC isolation capacitor and the inductor element form a parallel connection with the electrostatic protection element.

Another technical means of the present invention is that the electrostatic protection element and the inductor element are connected in series.

Another technical means of the present invention is that the anti-static protection circuit for radio frequency transmission further includes a DC isolation capacitor, and the electrostatic protection element and the inductor element are in parallel relationship with the DC isolation capacitor.

The beneficial effect of the present invention is that the electrostatic protection module can effectively provide circuit protection during electrostatic discharge, and the inductance value of the inductor element can match the equivalent capacitance value of the electrostatic protection element, so that the radio frequency signal in the radio frequency transmission line can be maintained to maintain the gain of the radio frequency signal.

The patent features and technical contents of the present invention are clearly presented in the following detailed description of four preferred embodiments with reference to the drawings. Before the detailed description, it should be noted that similar components are represented by the same numbers.

Referring to FIG. 2, a first preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention is shown. The anti-static protection circuit for radio frequency transmission is suitable for connecting a radio frequency transmission line 31, wherein the main purpose of the radio frequency transmission line 31 is to transmit radio frequency (RF) signals. Radio frequency is also called radio frequency, wireless radio frequency, and high frequency. It is an oscillation frequency in the range of 3kHz to 300GHz. This frequency is equivalent to the frequency of radio waves. Therefore, the radio frequency transmission line 31 is mainly connected to an integrated circuit (IC) via an antenna. In actual implementation, the RF transmission line 31 may be a transmission line structure in an integrated circuit, or a wire connecting the integrated circuit to other electronic components or electronic devices, but should not be limited thereto.

The anti-static protection circuit for RF transmission includes a signal connection terminal 32 and an electrostatic protection module 33. The signal connection terminal 32 is arranged in the RF transmission line 31. Preferably, the RF transmission line 31 is arranged on a circuit board (not shown in the figure). The signal connection terminal 32 is arranged on the circuit board and is located at a node (such as a solder joint or a shunt node) on the RF transmission line 31, and is then connected to other electronic components through a circuit.

The electrostatic protection module 33 includes an electrostatic protection element 331 and an inductor element 332, wherein the electrostatic protection element 331 has a PN junction structure, which is a diode structure. One end of the electrostatic protection element 331 and the inductor element 332 are electrically connected to the signal connection terminal 32. The electrical connection can be a direct electrical contact or a connection achieved by indirectly transmitting an electronic signal through other electronic elements. The other end of the element 332 is grounded, and the grounding can be direct grounding or indirect grounding. The electrostatic protection element 331 and the inductor element 332 are used for one of impedance matching and filtering. When the RF transmission line 31 transmits the RF signal normally, the gain of the RF signal transmission can be maintained, and electrostatic protection on the RF path can be provided. A small-area anti-static PN junction structure can be used to achieve a good anti-static effect without affecting the RF characteristics.

In the first preferred embodiment, the electrostatic protection element 331 and the inductor element 332 are in parallel relationship, the tops of the electrostatic protection element 331 and the inductor element 332 are directly electrically connected to the signal connection terminal 32, and the bottoms of the electrostatic protection element 331 and the inductor element 332 are grounded, wherein the electrostatic protection element 331 is a PN junction structure formed by a plurality of P-type semiconductors and a plurality of N-type semiconductors in a single crystal microwave integrated circuit (MMIC), also known as a bidirectional The breakdown diode is also called a transient voltage suppression diode (TVS). The inductor element 332 is a coil structure in a single crystal microwave integrated circuit (MMIC). Since it is a known technology to set a semiconductor element structure and a coil structure in an integrated circuit, they will not be described one by one here. In actual implementation, the electrostatic protection element 331 and the inductor element 332 can also be physical elements set on the outside of the single crystal microwave integrated circuit (MMIC), and should not be limited to this.

Please refer to FIG. 3, which is a second preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention. The second preferred embodiment is substantially the same as the first preferred embodiment, and the similarities are not described in detail here. The difference is that the anti-static protection circuit for radio frequency transmission further includes a DC isolation capacitor 34, and the DC isolation capacitor 34 is electrically connected to the signal connection terminal 32. The DC isolation capacitor 34 is first connected in series with the inductor element 332, and the DC isolation capacitor 34 and the inductor element 332 form a parallel relationship with the electrostatic protection element 331, wherein the top ends of the electrostatic protection element 331 and the inductor element 332 are electrically connected to the signal connection terminal 32, the bottom end of the inductor element 332 is electrically connected to the top end of the DC isolation capacitor 34, and the bottom ends of the electrostatic protection element 331 and the DC isolation capacitor 34 are grounded. In actual implementation, the arrangement positions of the DC isolation capacitor 34 and the inductor element 332 can be interchanged, and should not be limited to this.

Please refer to FIG. 4, which is a third preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention. The third preferred embodiment is substantially the same as the first preferred embodiment, and the similarities are not described in detail here. The difference is that the electrostatic protection element 331 and the inductor element 332 are in a series relationship. Preferably, the signal connection terminal 32, the electrostatic protection element 331 and the inductor element 332 are in the order of series connection. In actual implementation, the electrostatic protection element 331 and the inductor element 332 can be interchanged, and should not be limited to this.

Please refer to FIG. 5 , which is a fourth preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention. The fourth preferred embodiment is substantially the same as the third preferred embodiment, and the similarities are not described in detail here. The difference is that the anti-static protection circuit for radio frequency transmission further includes a DC isolation capacitor 34, and the DC isolation capacitor 34 is electrically connected to the signal connection terminal 32, and the DC isolation capacitor 34 and the electrostatic protection module 33 are in parallel.

It is worth mentioning that, since the inductor will cause static leakage current when grounded, the traditional electrostatic protection circuit will not use the inductor. However, the present invention is aimed at electrostatic protection of the RF transmission line 31 that transmits the RF signal. Therefore, the characteristics of the inductor can be used as an impedance matching element or a filtering element of the electrostatic protection element 331. When the RF signal is in the RF transmission line 31, the inductor element 332 will not generate static leakage current. When the RF transmission line 31 has an electrostatic discharge event, the electrostatic discharge current can be immediately directed to the ground.

In summary, the anti-static protection circuit for RF transmission has impedance matching characteristics or filtering characteristics, and will not affect the gain of the RF signal when it is transmitted on the RF transmission line 31. When the RF transmission line 31 transmits the RF signal normally, no static leakage current will be generated. When the RF transmission line 31 generates electrostatic discharge, the electrostatic protection element 331 can quickly conduct the electrostatic current to the ground, and can indeed protect the circuit to achieve electrostatic protection on the RF path. In addition, a small-area anti-static PN junction structure is used to achieve a good anti-static effect without affecting the RF signal characteristics, so the purpose of the present invention can indeed be achieved.

However, the above are only four preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention. In other words, all simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention description are still within the scope of the present patent.

111: Data line 112: Ground line 121: Connection terminal 122: Connection terminal 131: Connection terminal 132: Connection terminal 141: Series protection circuit 151: PN junction electronic component 31: RF transmission line 32: Signal connection terminal 33: Electrostatic protection module 331: Electrostatic protection component 332: Inductor component 34: DC isolation capacitor

FIG1 is a circuit diagram of the Republic of China Patent I766656, illustrating an electrostatic discharge protection circuit; FIG2 is a circuit diagram of a first preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention; FIG3 is a circuit diagram of a second preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention; FIG4 is a circuit diagram of a third preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention; and FIG5 is a circuit diagram of a fourth preferred embodiment of an anti-static protection circuit for radio frequency transmission of the present invention.

31: RF transmission line

32: Signal connection terminal

33: Electrostatic protection module

331: Electrostatic protection element

332: Inductor components

Claims (5)

An anti-static protection circuit for radio frequency transmission is suitable for connecting a radio frequency transmission line and comprises: A signal connection terminal, which is arranged in the radio frequency transmission line; and An electrostatic protection module, which comprises an electrostatic protection element and an inductor element. The electrostatic protection element has a PN junction structure. One end of the electrostatic protection element and the inductor element is electrically connected to the signal connection terminal. The other ends of the electrostatic protection element and the inductor element are grounded. The electrostatic protection element and the inductor element are used for one of impedance matching and filtering. An anti-static protection circuit for radio frequency transmission as described in claim 1, wherein the electrostatic protection element and the inductor element are in parallel relationship. The anti-static protection circuit for radio frequency transmission as described in claim 1 further includes a DC isolation capacitor, the DC isolation capacitor and the inductor element are in series connection, and the DC isolation capacitor and the inductor element are in parallel connection with the electrostatic protection element. An anti-static protection circuit for radio frequency transmission as described in claim 1, wherein the electrostatic protection element and the inductor element are in series connection. The anti-static protection circuit for radio frequency transmission as described in claim 4 further includes a DC isolation capacitor, and the electrostatic protection element and the inductor element are in parallel with the DC isolation capacitor.