A radio frequency current probe based on a coplanar waveguide structure with high flatness

Abstract

The application provides a radio frequency current probe with high flatness based on a coplanar waveguide structure, also called a 1Ω probe. The probe directly contacts a ground pin of a chip, collects a radio frequency (RF) current signal generated in a ground plane and returned by a circuit, and then transmits the signal to a spectrum analyzer or an EMI receiver to measure a corresponding RF voltage value. According to a conversion coefficient R, the voltage value can be converted into a corresponding current value. The radio frequency current probe can directly contact a chip pin, 1Ω input impedance is realized by using a multi-resistance parallel technology, current resistance of the probe is improved, and the influence of a lumped resistance parasitic effect is reduced, so that a probe insertion loss S21 fluctuates by not more than ±2dB in a frequency range of 150kHz-1GHz. The design process adopted by the application is a mature printed circuit board and CNC process, and has the advantages of portability, replicability, low cost, short development cycle and the like for batch production requirements.

Description

Technical Field

[0001] This invention relates to a radio frequency current probe with high flatness based on a coplanar waveguide structure, used for conducting emission measurement of chip pins, evaluating the conducted emission level of the chip, and belonging to the field of chip electromagnetic compatibility testing. Background Technology

[0002] As integrated circuit manufacturing processes continue to evolve towards the nanoscale, chip integration density has significantly increased, with the number of transistors within a single chip growing exponentially. This high-density integration generates a large amount of transient current within the chip during high-speed switching of digital circuits. When multiple transistors flip simultaneously at the clock edge, the amplitude of their superimposed transient current increases dramatically and couples to the power distribution network (PDN) of the printed circuit board via the chip's power and ground pins. These rapidly changing currents form complex high-frequency current loops in the PDN. The radio frequency current flowing in these loops causes voltage fluctuations, power integrity degradation, and ground bounce noise, resulting in interference to the chip's power ports and adjacent devices. Furthermore, due to the high-frequency components in the current loops, their radiation effects generate electromagnetic fields in space, becoming potential sources of radiated emissions that may cause system-level electromagnetic interference (EMI), affecting the normal operation of other circuit modules or chips. Therefore, to effectively assess the conducted radio frequency current levels generated by the chip during operation, it is necessary to establish corresponding testing and analysis methods. This invention proposes a radio frequency current probe with high flatness based on a coplanar waveguide structure, which can quantitatively evaluate the radio frequency current characteristics of a chip under different operating conditions, providing data support for PDN design, power supply decoupling, filter selection and electromagnetic protection measures.

[0003] Existing technology involves placing the RF current test coupling network on the test board. This requires adding a test network to each pin of the chip, which increases the fabrication complexity and cost of the test board. Summary of the Invention

[0004] This invention proposes a high-flatness radio frequency (RF) current probe based on a coplanar waveguide structure, also known as a 1Ω probe. The probe directly contacts the ground pin of the chip to acquire the RF current signal generated and returned by circuit activity in the ground plane; this signal is then transmitted to a spectrum analyzer or EMI receiver to measure the corresponding RF voltage value. Using the conversion factor R (unit: dBΩ), the voltage value can be converted into the corresponding current value, such as... Figure 1 As shown.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention discloses a radio frequency current probe with high flatness based on a coplanar waveguide structure, which consists of at least a probe, a circuit board, an SMA connector, a metal base plate, and a metal housing.

[0006] The circuit board described uses a two-layer design, with the bottom layer serving as the ground layer and the top layer as the signal layer, such as... Figure 2 As shown. Signal island 2-1, lumped resistors 2-2, lumped resistors 2-3, lumped resistors 2-4, and coplanar waveguide 2-5 are arranged on the top layer. The probe is soldered to signal island 2-1; one end of lumped resistor 2-2 is connected to signal island 2-1, and the other end is connected to the upper ground of coplanar waveguide 2-5; one end of lumped resistor 2-3 is connected to signal island 2-1, and the other end is connected to the lower ground of coplanar waveguide 2-5; one end of lumped resistor 2-4 is connected to signal island 2-1, and the other end is connected to coplanar waveguide 2-5; the coplanar waveguide is used for signal transmission and to achieve 50Ω impedance matching, and coplanar waveguide 2-5 is connected to a receiver or spectrum analyzer via SMA connector 2-6.

[0007] The metal probe is made of aluminum alloy and plated with gold, such as... Figure 3 As shown. The probe tip is a smooth, curved structure for contact and detection; immediately following it is a transitional cubic module; and at the very end extend two parallel rectangular protrusions for stable soldering onto the circuit board.

[0008] The metal base plate is made of aluminum alloy and gold-plated. Its main outline is an isosceles trapezoidal shape, strictly symmetrical along its longitudinal central axis. A groove is cut into the center of the base plate for placing a circuit board, such as... Figure 4 As shown.

[0009] The metal casing is made of aluminum alloy, such as Figure 5 As shown, the right half of the outer shell is a cube structure, while the left half is cut with bevels, causing the side walls and top wall to slope and converge towards the center and downwards respectively, forming a structure similar to a trumpet.

[0010] This RF current probe is calibrated using an open-circuit microstrip line structure. The open-circuit microstrip line has a two-layer board structure, such as... Figure 6 As shown: the bottom layer is a complete ground plane, the left end of the top layer is designed as an open-circuit microstrip line with a characteristic impedance of 50 Ω, and the right end is a copper-filled area, which is connected to the bottom ground plane by an array of vias to ensure good electrical connection and stable reference ground performance.

[0011] The advantages and beneficial effects of this invention are as follows: the RF current probe can directly contact the chip pins, and the use of multi-resistor parallel technology to achieve a 1Ω input impedance not only improves the probe's current tolerance but also reduces the impact of lumped resistance parasitic effects, ensuring that the probe's insertion loss S21 fluctuates by no more than ±2dB within the 150kHz~1GHz frequency band. The design process used in this invention is a mature printed circuit board and CNC process, offering advantages such as portability, reproducibility, low cost, and short development cycle for mass production needs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of an RF current probe.

[0013] Figure 2 This is a schematic diagram of the internal circuit board layout of an RF current probe.

[0014] Figure 3 This is a schematic diagram of the metal probe of an RF current probe.

[0015] Figure 4 This is a schematic diagram of the metal base plate of an RF current probe.

[0016] Figure 5 This is a schematic diagram of the metal casing of an RF current probe.

[0017] Figure 6 This is a schematic diagram of an open-circuit microstrip line, which is the calibration component for an RF current probe.

[0018] Figure 7 The result is shown in the insertion loss S21 diagram of the RF current probe.

[0019] Figure 8 This is a schematic diagram of the chip's conducted emission current measurement.

[0020] Explanation of icon numbers: 2-1: Signal island, 2-2: Lumped resistor, 2-3: Lumped resistor, 2-4: Lumped resistor 2-5: Coplanar waveguide; 2-6: SMA connector; 6-1: SMA connector; 6-2: Open-circuit microstrip line. 6-3: Via array. Detailed Implementation

[0021] With reference to the accompanying drawings, the specific structure, function, and positional relationship of each component of a radio frequency current probe with high flatness based on a coplanar waveguide structure are further explained.

[0022] Figure 1This invention illustrates the working principle of a radio frequency (RF) current probe with high flatness based on a coplanar waveguide structure. RF current from the chip pins flows into the probe probe, with most of the current shunted through a 1Ω resistor and flowing into ground. Since both the coaxial cable and the receiver have a characteristic impedance of 50Ω, directly connecting them in parallel with the 1Ω resistor to measure voltage would result in severe impedance mismatch, causing signal reflection and affecting measurement accuracy. Therefore, a 49Ω resistor needs to be introduced in the signal path to form an equivalent 50Ω impedance matching network with the 1Ω resistor, effectively preventing reflection.

[0023] Figure 2 This invention illustrates the layout of the internal circuit board of a radio frequency current probe with high flatness based on a coplanar waveguide structure. Lumped resistors 2-2 and 2-3 both have a resistance of 2Ω, one end connected to the signal island, and the other end connected to the upper and lower reference grounds of the coplanar waveguide, respectively, achieving an input impedance of 1Ω. Lumped resistor 2-4 has a resistance of 49Ω, one end connected to the signal island, and the other end connected to the coplanar waveguide. The coplanar waveguide has a characteristic impedance of 50Ω and is connected to a spectrum analyzer or receiver via an SMA connector.

[0024] Figure 3 , Figure 4 and Figure 5 The structure of the metal probe, metal base plate, and metal casing is shown in sequence, all made of aluminum alloy. To ensure good conductivity of the metal probe and metal base plate, they need to be gold-plated.

[0025] Figure 6 The layout of the calibration component for the RF current probe—an open-circuit microstrip line—is shown. It adopts a two-layer board structure, with the bottom layer being a complete ground plane. The left end of the top layer is designed as an open-circuit microstrip line with a characteristic impedance of 50 Ω, and the right end is a copper-padded area, which is spaced at a certain distance from the microstrip line and has an array of vias added to ensure good electrical connection and stable reference ground performance.

[0026] Figure 7 The results of the insertion loss S21 of a radio frequency current probe with high flatness based on a coplanar waveguide structure, as shown in this invention, are presented. Within the frequency range of 150kHz to 1GHz, the fluctuation of S21 is very small, not exceeding ±2dB. This indicator is a requirement stipulated by standards, and currently there are no related probes of this type in China.

[0027] Figure 8This invention demonstrates an example of measuring the emitter current of a chip's ground pin. The probe tip directly contacts the pin of the chip under test, the probe's base plate contacts the test board, and the 1Ω coupling network inside the probe is connected between the pin and ground. The probe's output SMA connector is connected to the 50Ω input of a spectrum analyzer or oscilloscope via a coaxial cable. The RF voltage spectrum measured by the instrument can be converted to obtain the RF current spectrum of the pin, thus quickly acquiring the RF current intensity of different frequency components on the pin using a point-to-point method.

[0028] It should be noted that the technical means and design methods disclosed in this invention are not limited to this invention, but also applicable to other solutions, invention methods, and invention products derived from the design ideas, invention methods, technical means, and technical features described in this invention. Therefore, these other derived solutions, invention methods, and invention products should all be considered within the scope of protection of this invention.

Claims

1. A radio frequency current probe with high flatness based on a coplanar waveguide structure, characterized in that: It consists of at least a probe, a circuit board, an SMA connector, a metal base plate, and a metal housing; The circuit board is a two-layer board, with the bottom layer as the ground layer and the top layer as the signal layer. The signal island, the first lumped resistor, the second lumped resistor, the third lumped resistor and the coplanar waveguide are arranged on the top layer. The probe is soldered to the signal island; one end of the first lumped resistor is connected to the signal island, and the other end is connected to the upper ground of the coplanar waveguide; one end of the second lumped resistor is connected to the signal island, and the other end is connected to the lower ground of the coplanar waveguide; one end of the third lumped resistor is connected to the signal island, and the other end is connected to the coplanar waveguide. The probe has a smooth, curved front end for contact and detection; immediately following it is a transitional cubic module; and at the rear end extend two parallel rectangular protrusions for stable soldering onto the circuit board. The main outline of the metal base plate is an isosceles trapezoidal shape, strictly symmetrical along the longitudinal central axis; a groove is opened in the middle of the base plate for placing the circuit board; The metal shell has a cube-shaped right half and a horn-like structure on the left half, which is cut with bevels so that the side walls and top wall slope towards the center and downwards respectively.

2. The radio frequency current probe with high flatness based on a coplanar waveguide structure according to claim 1, characterized in that: Coplanar waveguides are used to transmit signals and achieve 50Ω impedance matching. Coplanar waveguides are connected to receivers or spectrum analyzers via SMA connectors.

3. The radio frequency current probe with high flatness based on a coplanar waveguide structure according to claim 1, characterized in that: The probe is made of aluminum alloy and gold-plated, the metal base plate is made of aluminum alloy and gold-plated, and the metal shell is made of aluminum alloy.

4. The radio frequency current probe with high flatness based on a coplanar waveguide structure according to claim 1, characterized in that: The RF current probe is calibrated using an open-circuit microstrip line structure. The open-circuit microstrip line has a two-layer board structure, with the bottom layer being a complete ground plane. The left end of the top layer is designed as an open-circuit microstrip line with a characteristic impedance of 50 Ω, and the right end is a copper-plated area connected to the bottom ground plane using an array of vias.

5. A method for operating a radio frequency current probe with high flatness based on a coplanar waveguide structure as described in any one of claims 1-4, characterized in that: The probe tip is directly contacted with the pin of the chip under test, and the probe base plate is in contact with the test board. The 1Ω coupling network inside the probe is then connected between the pin and ground. The probe output SMA connector is connected to the 50Ω input terminal of the spectrum analyzer or oscilloscope via a coaxial cable. At this time, the RF voltage spectrum measured by the instrument is converted to obtain the RF current spectrum of the pin, thereby quickly obtaining the RF current intensity of different frequency components on the pin in a point-to-point manner.

Images