Solid-state noise source device

Abstract

The present invention discloses a solid-state noise source device, comprising a constant current source, a microstrip low-pass filter, a noise diode, an attenuator and a waveguide-coaxial-microstrip converter which are electrically connected in sequence, wherein the noise diode is used to generate an original noise signal, the original noise signal passes through the attenuator to stabilize the noise power, the microstrip low-pass filter is placed at the input end of the noise diode to suppress the leakage of the noise power; the waveguide-coaxial-microstrip converter is used to convert the noise signal from the waveguide to the microstrip output, and its output end is used as the output of the solid-state noise source device; the attenuator and the waveguide-coaxial-microstrip converter jointly coordinate the impedance matching of the circuit, and the constant current source provides a stable power supply for the device. The solid-state noise source device of the present invention operates in the Ka band, has high output power, high super-noise ratio, and also has a low standing wave coefficient.

Description

Technical Field

[0001] The invention relates to a solid-state noise source, in particular to a solid-state noise source device operating in the Ka band. Background Art

[0002] At present, noise interference in the signal transmission process has become the main interference of modern radio transmission and processing links. Therefore, the noise resistance coefficient of the device is a must-test item. Since solid-state noise sources have the advantages of wide bandwidth, fast switching, low power consumption and high reliability, they are often used for noise testing in the microwave radio frequency field. In recent years, with the development of modern communication technology, especially satellite communication services, C, Ku and Ka bands have become common frequency bands for satellite live broadcast, news gathering and other services. Various devices have higher requirements for noise coefficients. The operating frequencies of existing noise sources are mostly concentrated in low-frequency bands and narrow-band noise outputs, which can no longer meet the operating frequencies of some devices under test. In the project of Zhang Yonghong et al. in 2018, a broadband noise source with a frequency range of 22-32GHz in the K band was studied; in two papers published by Dong Shuai et al. in the Journal of Electronics in 2018 and 2016, the working frequency bands of the developed noise sources were only concentrated in the L / C band. Therefore, how to design and implement a noise source that works in a higher frequency band (Ka band), has a high bandwidth, uniform spectrum density, high output power and is easy to implement is an important task. Summary of the invention

[0003] Purpose of the invention: In view of the above problems, the present invention proposes a solid-state noise source device that operates in the Ka band and has a high super-noise ratio, a low standing wave coefficient and a wide bandwidth.

[0004] Technical solution: The technical solution adopted by the present invention is a solid-state noise source device, including a constant current source, a microstrip low-pass filter, a noise diode, an attenuator and a waveguide-coaxial-microstrip converter electrically connected in sequence, the noise diode is used to generate an original noise signal, the original noise signal passes through the attenuator to stabilize the noise power, the microstrip low-pass filter is placed at the input end of the noise diode to suppress the leakage of noise power; the waveguide-coaxial-microstrip converter is used to convert the noise signal from the waveguide to the microstrip output, and its output end serves as the output of the solid-state noise source device; the attenuator and the waveguide-coaxial-microstrip converter jointly coordinate the impedance matching of the circuit, and the constant current source provides a stable power supply for the device.

[0005] The waveguide-coaxial-microstrip converter includes a waveguide, a first microstrip line integrated on a dielectric substrate, and a coaxial line connecting the two; the coaxial line includes a probe buried in the waveguide, a central conductor connected to the probe, and an insulating sleeve wrapped around the central conductor. The probe, the central conductor, and the first microstrip line are all made of copper and welded together. An air gap is left between the insulating sleeve and the waveguide (from the lower edge of the insulating sleeve to the upper surface of the waveguide), and the wave impedance is changed by adjusting the length of the air gap. The surface of the waveguide is gold-plated. The radius of the central conductor is preferably 0.5 to 0.6 mm.

[0006] The microstrip low-pass filter is composed of a quarter-wavelength impedance line integrated on a dielectric substrate and two quarter-wavelength double-sector microstrip lines in parallel structure. The double-sector microstrip line is connected to the middle section of the impedance line and is composed of two opposite fan-shaped branches with the impedance line as the central axis. In order to save device space and obtain a wider frequency band, the length of the microstrip low-pass filter along the impedance line direction is less than 5mm. The impedance line and the double-sector microstrip line are made of copper foil, and the thickness of the copper foil is 0.01-0.02mm.

[0007] Preferably, the solid-state noise source of the above circuit structure is adopted, and the attenuator is preferably a fixed gain attenuator using a balanced three-way thin film resistor process, and a DC isolation circuit is also provided at both ends of the attenuator. The model of the noise diode adopts the WZ0003H series. The constant current source adopts an integrated three-terminal regulator LM317 with a variable output voltage as a regulated output.

[0008] In order to control the on and off of the noise source, the device also includes a switch driving circuit for controlling the on and off of the circuit, which is connected in series between the fixed gain attenuator and the waveguide-coaxial-microstrip converter. Preferably, the switch driving circuit includes a PIN diode and a PIN diode switch driver, and the PIN diode switch driver sends a driving signal to control the on and off of the PIN diode.

[0009] Beneficial effects: Compared with the prior art, the present invention has the following advantages: the present invention is based on the chip-packaged diode WZ0003H series, combined with the waveguide-coaxial-microstrip converter to meet the requirement that the noise source works in the Ka band; the constant current source circuit is combined with a fixed gain attenuator to stabilize the output power of the noise source; the waveguide-coaxial-microstrip converter adopts an insulator probe transition method, and together with the attenuator, realizes the impedance matching of the circuit to reduce power loss and reduce the standing wave coefficient; the microstrip low-pass filter plays a role in preventing signal leakage, and the structure adopts a double-sector microstrip to increase the bandwidth; the structure of the double-sector microstrip low-pass filter can well avoid signal leakage and save space for the noise source system. The final switch-type circuit structure design is convenient for controlling the switch of the noise source in actual use, and provides convenience for the integrated design and related parameter testing based on the present invention. All circuit units in the noise source proposed by the present invention are realized on a dielectric substrate through PCB technology, with higher processing accuracy and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a circuit module diagram of the solid-state noise source of the present invention.

[0011] Figure 2 It is a schematic diagram of the appearance structure of the present invention.

[0012] Figure 3 It is the constant current source circuit diagram of the present invention.

[0013] Figure 4 It is a diagram of the internal structure of the microstrip low-pass filter described in the present invention.

[0014] Figure 5 This is a structural diagram of the waveguide-coaxial-microstrip conversion described in the present invention.

[0015] Figure 6 This is the standing wave coefficient test chart described in the present invention.

[0016] Figure 7 This is a physical picture of the solid-state noise source product described in the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0018] The circuit module schematic diagram of the solid-state noise source of the present invention is as follows Figure 1As shown, the utility model provides a solid-state noise source, including a WZ0003H series noise diode, a constant current source circuit, a microstrip low-pass filter, an attenuator, a switch drive circuit and a waveguide-coaxial-microstrip converter. The constant current source circuit supplies power to the noise diode, and the noise signal generated by the noise diode has a stable output power after passing through the attenuator. Under the switch control of the drive circuit, the noise signal is output through the waveguide-coaxial-microstrip converter. Both ends of the attenuator are provided with a DC isolation circuit, and two DC isolation capacitors C1 and C2 are used in this example.

[0019] The schematic diagram of the appearance structure of the present invention is as follows Figure 2 As shown. The overall component is 6.5cm long, 4cm wide and 1.2cm high. The noise diode, constant current source, switch drive circuit and matching circuit are integrated on a PCB board 201. The constant current source 202 and the matching circuit are both placed in a closed cavity 203. In actual use, the resistor R is set to 68Ω, the LOAD terminal is connected to the noise diode, and the +12V voltage is connected to the Vin terminal 204 of the metal cavity shell of the noise source to provide a constant working current for the noise tube. The actual current measured by this system is 19mA, which meets the power supply requirement of the noise source +24V. In addition, the ATN3580 series 2dB fixed gain attenuator adopts a balanced three-way thin film resistor process, which is integrated between the output end of the noise diode and the drive switch 205, and plays a role in output impedance matching. The present invention uses a PIN diode switch MA4AGSW1 to control the output of the noise source. The noise diode is connected to the inductor and capacitor network through an external PIN tube driver BHD-2P2 to form a switch circuit 205 to prevent signal leakage. The drive switch circuit is powered by the ±5V power supply terminal 206 outside the metal cavity, and the drive signal terminal 207 is connected to the integrated PCB board 201 and the drive switch chip pin through the small hole of the shell to connect the external working signal.

[0020] The constant current source circuit diagram of the present invention is as follows Figure 3 As shown, an integrated three-terminal voltage regulator of model LM317-N is selected, the packaging model is SOT-223(4), and the overall volume is 6.5mm*3.5mm. By adding a fixed resistor to connect to the load, the LM317 integrated three-terminal voltage regulator can be used as a precise constant current source, and the design is simple, and the output constant current power supply is easy to control.

[0021] The microstrip low-pass filter designed in this system is Figure 4As shown, it is composed of a quarter-wavelength impedance line (inductance characteristics) and a quarter-wavelength parallel structure double fan-shaped microstrip line (capacitance characteristics), which are connected between the output end of the constant current source and the input end of the noise diode. The front port 401 of the microstrip filter is connected to the external circuit (the output end of the constant current source), and the middle section 402 of the impedance line is connected to two parallel structure double fan-shaped microstrip lines 403, and the double fan-shaped microstrip line 403 is composed of two opposite fan-shaped branches, and the two opposite fan-shaped branches are centered on the impedance line. The above structure is integrated on a Rogers 5880 dielectric substrate 404 with a thickness of 0.127mm and a dielectric constant of 2.2. The impedance line and the double fan-shaped microstrip line are both made of copper foil, and the thickness of the copper foil is 0.017mm. The length from the left port to the right port is 4.95mm, the frequency band is wide and space-saving. The noise diode bias low-pass filter structure can suppress the leakage of noise power.

[0022] The internal structure diagram of the waveguide-coaxial-microstrip converter is shown in Figure 5 As shown, the impedance matching is achieved by using the insulator probe transition method. The signal enters from the port of the waveguide 501, is finally converted into a microstrip output through the coaxial line, and is output by the first microstrip line 505. The first microstrip line 505 is integrated on a dielectric substrate 506 of Rogers 5880 with a dielectric constant of 2.2. Among them, the coaxial line is composed of a probe 502 buried in the waveguide, a center conductor 503 and an insulating sleeve 504. The center conductor 503 passes through the dielectric substrate 506 and is connected to the first microstrip line 505 with an impedance of 50Ω on the upper part by welding, which has the advantages of low loss, compact structure, good sealing and easy processing and manufacturing. The surface of the waveguide 501 is covered with gold, and the insulating sleeve 504 is a hollow cylinder, which is wrapped around the center conductor 503 with a radius of 0.55mm, with a relative dielectric constant of 4.1 and an outer radius of 0.975mm. The probe 502, the center conductor 503, and the first microstrip line 505 are all made of copper and welded together. An air gap is left between the lower edge of the insulating sleeve 504 and the upper surface of the waveguide 501 . The wave impedance can be changed and the standing wave coefficient can be reduced by adjusting the length of the air gap.

[0023] The present invention adopts direct test method to measure standing wave coefficient. Figure 6 It can be seen that in the frequency band of 25-40GHz, the output noise standing wave ratio at 40GHz is about 1.5:1, and the performance is good in the high frequency band.

[0024] The final product of the present invention is shown in the figure Figure 7 As shown, the technical indicators achieved are as follows:

[0025] Noise frequency band output by the noise source: 25-40GHz;

[0026] Output noise signal over-noise ratio: 21±2dB;

[0027] Standing wave coefficient of noise source: <1.5:1;

[0028] Interface specifications: WR-28 standard rectangular waveguide;

[0029] Noise source power supply voltage: +24V.

[0030] It can be seen that the present invention can provide the system with an ultra-noise ratio of up to 21±2dB and a wider frequency band, while the standing wave coefficient of the noise source is lower than 1.5.

Claims

1. A solid-state noise source device, characterized in that: The invention is composed of a constant current source, a microstrip low-pass filter, a noise diode, an attenuator, a switch driving circuit and a waveguide-coaxial-microstrip converter which are electrically connected in sequence. The noise diode is used to generate an original noise signal. The original noise signal passes through the attenuator to stabilize the noise power. The microstrip low-pass filter is placed at the input end of the noise diode to suppress the leakage of the noise power. The waveguide-coaxial-microstrip converter is used to convert the noise signal from the waveguide to a microstrip output, and its output end is used as the output of the solid-state noise source device. The attenuator and the waveguide-coaxial-microstrip converter jointly coordinate the impedance matching of the circuit, and the constant current source provides a stable power supply for the device. The waveguide-coaxial-microstrip converter comprises a waveguide, a first microstrip line integrated on a dielectric substrate, and a coaxial line connecting the two; the coaxial line comprises a probe buried in the waveguide, a central conductor connected to the probe, and an insulating sleeve wrapped outside the central conductor, the probe, the central conductor and the first microstrip line are all made of copper and welded together, an air gap is left between the insulating sleeve and the waveguide, and the wave impedance is changed by adjusting the length of the air gap; The attenuator is a fixed gain attenuator using a balanced three-way thin film resistor process, and both ends of the attenuator are provided with a DC isolation circuit.

2. The solid-state noise source device according to claim 1, characterized in that: The surface of the waveguide is gold-plated, and the radius of the central conductor is 0.5-0.6 mm.

3. The solid-state noise source device according to claim 1, characterized in that: The microstrip low-pass filter is composed of a quarter-wavelength impedance line integrated on a dielectric substrate and two quarter-wavelength double-fan-shaped microstrip lines in parallel structure. The double-fan-shaped microstrip line is connected to the middle section of the impedance line and consists of two opposite fan-shaped branches with the impedance line as the central axis.

4. The solid-state noise source device according to claim 3, characterized in that: The length of the microstrip low-pass filter along the impedance line direction is less than 5 mm, and the impedance line and the double-sector microstrip line are made of copper foil, and the thickness of the copper foil is 0.01-0.02 mm.

5. The solid-state noise source device according to claim 1, characterized in that: The model of the noise diode is WZ0003H series.

6. The solid-state noise source device according to claim 1, characterized in that: The constant current source uses an integrated three-terminal voltage regulator LM317 with variable output voltage as a regulated voltage output.

7. The solid-state noise source device according to claim 1, characterized in that: The switch driving circuit is used to control the on and off of the circuit.

8. The solid-state noise source device according to claim 7, characterized in that: The switch driving circuit includes a PIN diode and a PIN diode switch driver, and the PIN diode switch driver sends a driving signal to control the switching of the PIN diode.

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