X-band voltage-controlled dielectric oscillator

Abstract

The present invention discloses an X-band voltage-controlled dielectric oscillator (VCO). The VCO includes an active amplifier network, a frequency-selective network, a voltage-tuning structure, a buffer amplifier, and a power supply module. The output of the active amplifier network is connected to the input of the frequency-selective network and the input of the buffer amplifier, respectively. The output of the frequency-selective network is connected to another input of the active amplifier network. The input of the voltage-tuning structure is connected to a tuning voltage, and the output is connected to another input of the frequency-selective network. The output of the buffer amplifier is a signal output. The power supply module is connected to the active amplifier network and the buffer amplifier, respectively. This VCO has a larger voltage-tuning bandwidth and lower output phase noise, providing better load-pull suppression. Furthermore, its compact size meets the requirements of system miniaturization.

Description

Technical Field

[0001] The present invention relates to the field of microwave hybrid integrated circuits, and in particular to an X-band voltage-controlled dielectric oscillator. Background Art

[0002] Microwave oscillators are widely used in radar, communication, navigation, electronic countermeasures and other fields. They provide local oscillator signals in microwave systems and are one of the core components of the entire system. Their performance directly affects the overall performance indicators of the system.

[0003] Phase noise is one of the most important specifications of microwave oscillators. Its magnitude directly affects receiver sensitivity. In digital communication systems, excessive phase noise can lead to increased bit error rates. With the continuous advancement of modern communication technology, requirements for oscillator stability, phase noise, and size are becoming increasingly stringent. Furthermore, in modern communication equipment, oscillators are generally required to have voltage-modulated frequency capabilities to facilitate data signal insertion or the use of phase-locked systems.

[0004] Among existing solutions, dielectric oscillators (DSOs), which use high-quality dielectric resonators as frequency stabilization devices, are widely used in various microwave frequency integrated systems due to their high stability, low phase noise, simple structure, and compact size. Dielectric resonators are composed of microwave ceramic materials with a high dielectric constant, which can confine most electromagnetic energy within the dielectric block, acting as a resonant frequency-selective network in the circuit. Within the same frequency band, the volume of a dielectric resonator is much smaller than that of a metal resonant cavity, and dielectric resonators can be easily incorporated into microwave hybrid integrated circuits through coupling, offering significant advantages in miniaturized designs. In practical applications, common dielectric resonators include cylindrical and coaxial DSOs. Coaxial DSOs generally operate below the L-band, requiring frequency multiplication of the output signal in high-frequency applications, which places a heavy load on the system architecture. Cylindrical DSOs, on the other hand, operate up to the millimeter-wave band, allowing for direct output of the oscillation signal and simplifying the system.

[0005] However, due to the high quality factor of the dielectric resonator, the voltage tuning bandwidth of the dielectric oscillator is generally low. Currently, the tuning bandwidth of the dielectric oscillator operating in the X-Ku band is only about 10MHz-20MHz. The low electrical tuning bandwidth increases the risk of the dielectric phase-locked source losing lock in harsh environments and is not conducive to the full use of the spectrum. Summary of the Invention

[0006] The present invention aims to provide an X-band voltage-controlled dielectric oscillator (VCO) with a larger voltage tuning bandwidth, lower output phase noise, and better load-pull suppression. Furthermore, the VCO is compact, meeting the requirements of system miniaturization.

[0007] In order to achieve the above object, the present invention provides an X-band voltage-controlled dielectric oscillator, which includes an active amplifier network, a frequency selection network, a voltage tuning structure, a buffer amplifier and a power supply module, wherein:

[0008] The output end of the active amplifying network is connected to the input end of the frequency selection network and the input end of the buffer amplifier respectively; the output end of the frequency selection network is connected to the other input end of the active amplifying network; the input end of the voltage tuning structure is connected to the tuning voltage, and the output end is connected to the other input end of the frequency selection network; the output end of the buffer amplifier is the signal output end, and the power supply module is connected to the active amplifying network and the buffer amplifier respectively.

[0009] Preferably, the active amplification network is formed by GaAsFET transistors.

[0010] Preferably, the frequency selection network includes a drain microstrip line, a gate microstrip line and a cylindrical dielectric resonator located between the two microstrip lines, the other terminal of the gate microstrip line is connected to a matching impedance and then grounded, and the other terminal of the drain microstrip line is open; wherein, the relative dielectric constant of the dielectric resonator is 37.5, and the dielectric substrate of the dielectric resonator is a ceramic plate with a relative dielectric constant of 9.9.

[0011] Preferably, the voltage tuning structure includes a tuning microstrip line and a varactor diode connected to each other, and the voltage tuning structure is located at a side of the dielectric resonator.

[0012] Preferably, a gasket is provided below the dielectric resonator, and the gasket is a quartz plate.

[0013] Preferably, a low-impedance microstrip line segment is provided above a position of the tuning microstrip line close to the dielectric resonator.

[0014] Preferably, a microstrip interruption structure is added to the terminal of the tuning microstrip line, wherein the spacing between the microstrip terminals is 0.2 mm.

[0015] Preferably, the modulation voltage loaded on the voltage tuning structure is 0-20V DC.

[0016] Preferably, the gain of the buffer amplifier near the resonance point is +18 dB, and the input end return loss is less than -15 dB.

[0017] Preferably, the power module includes two three-terminal regulators, namely 7809 and 7805.

[0018] According to the above technical solution, the present invention connects the output of the active amplifier network to the input of the frequency-selective network and the input of the buffer amplifier, respectively; the output of the frequency-selective network is connected to the other input of the active amplifier network; the input of the voltage-tuning structure is connected to the tuning voltage, and the output is connected to the other input of the frequency-selective network; the output of the buffer amplifier serves as a signal output, and the power supply module is connected to the active amplifier network and the buffer amplifier, respectively. By improving the dielectric resonator voltage-tuning structure, greater coupling is achieved between the varactor diode and the dielectric resonator, thereby increasing the voltage-tuning bandwidth of the voltage-controlled dielectric oscillator. Furthermore, by using a high-quality dielectric resonator, the loop gain and coupling degree of the frequency-selective network are optimized, effectively improving the loaded quality factor of the frequency-selective network, resulting in an oscillator output with excellent phase noise performance and providing a pure local oscillator source. Furthermore, thanks to the excellent properties of the dielectric oscillator, this design has a simple circuit structure and high stability. It can directly generate the required frequency signal in the X-band without frequency multiplication, and the overall device is compact, meeting the requirements of system miniaturization and integrated design.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 This is a principle block diagram of the X-band voltage-controlled dielectric oscillator provided by the present invention;

[0022] Figure 2 This is the circuit structure principle diagram of the parallel feedback dielectric oscillator;

[0023] Figure 3 It is a schematic diagram of the principle of the improved voltage tuning structure;

[0024] Figure 4 This is the circuit schematic diagram of the power module.

[0025] Description of Reference Numerals

[0026] 1- Active amplification network 2- Frequency selection network

[0027] 3-Voltage Tuning Structure 4-Buffer Amplifier

[0028] 5-Power module 11-Drain microstrip line

[0029] 12-Gate microstrip line 13-Dielectric resonator

[0030] 14-Tuned microstrip line 15-Varactor diode

[0031] 16-GaAsFET transistor 17-gasket

[0032] 18-Low impedance microstrip line segment 19-Microstrip interruption structure DETAILED DESCRIPTION

[0033] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0034] In the present invention, unless otherwise stated, directional words such as "far, near, up, down" contained in a term merely represent the direction of the term in normal usage, or are common names understood by those skilled in the art, and should not be regarded as limitations on the term.

[0035] See also Figures 1 to 4 The present invention provides an X-band voltage-controlled dielectric oscillator, which includes an active amplifier network 1, a frequency selection network 2, a voltage tuning structure 3, a buffer amplifier 4 and a power supply module 5, wherein:

[0036] The output end of the active amplifying network 1 is respectively connected to the input end of the frequency selection network 2 and the input end of the buffer amplifier 4; the output end of the frequency selection network 2 is connected to the other input end of the active amplifying network 1; the input end of the voltage tuning structure 3 is connected to the tuning voltage, and the output end is connected to the other input end of the frequency selection network 2; the output end of the buffer amplifier 4 is the signal output end, and the power supply module 5 is respectively connected to the active amplifying network 1 and the buffer amplifier 4.

[0037] In this embodiment, the active amplifier network 1 is formed by GaAsFET transistors 16 .

[0038] The frequency selection network 2 includes a drain microstrip line 11, a gate microstrip line 12, and a cylindrical dielectric resonator 13 located between the two microstrip lines. The other terminal of the gate microstrip line 12 is connected to a matching impedance and then grounded, and the other terminal of the drain microstrip line 11 is open. The relative dielectric constant of the dielectric resonator 13 is 37.5, and the dielectric substrate of the dielectric resonator 13 is a ceramic plate with a relative dielectric constant of 9.9.

[0039] The voltage tuning structure 3 includes a tuning microstrip line 14 and a varactor diode 15 connected to each other. The voltage tuning structure 3 is located on the side of the dielectric resonator 13 .

[0040] A gasket 17 is provided below the dielectric resonator 13 , and the gasket 17 is a quartz plate.

[0041] A low-impedance microstrip line segment 18 is provided above the tuning microstrip line 14 near the dielectric resonator 13 .

[0042] A microstrip interruption structure 19 is added to the terminal of the tuning microstrip line 14, wherein the spacing between the microstrip terminals is 0.2 mm.

[0043] The modulation voltage loaded on the voltage tuning structure 3 is 0-20V DC.

[0044] The gain of the buffer amplifier 4 near the resonance point is +18 dB, and the input end return loss is less than -15 dB.

[0045] The power module 5 includes two three-terminal voltage regulators, namely 7809 and 7805.

[0046] Through the above technical solution, the voltage-controlled dielectric oscillator provided by the present invention adopts the circuit structure of a parallel feedback dielectric oscillator. The parallel feedback circuit structure has the characteristics of easy oscillation and large tuning bandwidth. The active device selects GaAsFET, which is commonly used in the X-band, with a low flicker corner frequency and noise figure, which can meet the requirements of low-noise output of the oscillator. In order to improve the oscillator's suppression of load pulling, the parallel feedback dielectric oscillator of this design selects the source as the output end, and places a dielectric resonator between the gate and drain microstrips as a frequency selection network. The dielectric resonator and the microstrip lines coupled on both sides together form a high-Q bandpass filter, forming a sharp and narrow passband at the resonant frequency. When the circuit is powered on, a noise signal with a rich spectrum appears in the circuit. The frequency selection network selects the signal at the resonant frequency and returns it to the input end of the active amplification network. After continuous amplification by the amplifier circuit, stable oscillation is achieved.

[0047] This design optimizes the oscillator phase noise based on the Leeson phase noise model. The Leeson formula is:

[0048]

[0049] Among them, P s is the effective signal power at the input of the active device, Q L is the loaded quality factor of the frequency selection network, F is the noise coefficient, k is the Boltzmann constant, T is the absolute temperature, f m is the frequency offset from the carrier, f0 is the carrier frequency, f c is the flicker noise corner frequency. According to formula (1), increasing P s With Q L By selecting high-gain medium-power field-effect transistors as active devices and adding appropriate matching structure pairs at the input and output ends, a higher gain of the active amplification network near the resonant frequency is achieved, thereby improving P sAt the same time, the distance between the dielectric resonator and the microstrip line in the frequency selection network is appropriately increased, and a low dielectric constant gasket is added under the dielectric resonator to achieve weak coupling of the dielectric resonator and improve the Q of the frequency selection network. L Since the active amplifier network has sufficient gain, the oscillator can still meet the starting conditions under weak coupling conditions.

[0050] According to the dielectric oscillator principle, the maximum tuning bandwidth of the voltage-controlled dielectric oscillator with a varactor diode is given by the following formula:

[0051]

[0052] Where β is the coupling degree between the dielectric resonator and the tuning microstrip, Q0 is the unloaded quality factor of the dielectric resonator, C d is the maximum capacitance of the varactor diode, and Z0 is the characteristic impedance of the tuning microstrip line. To achieve a larger voltage tuning bandwidth, the present invention selects a GaAs hyperabrupt junction varactor diode with a larger capacitance ratio. At the same time, the varactor diode also has a high Q value, which can minimize the impact on the oscillator phase noise. In addition, the present invention also proposes an improved electrical tuning structure that adds a low-impedance microstrip line segment to the tuning microstrip line, such as Figure 4 This structure increases the distributed inductance of the tuned microstrip line, thereby improving the coupling degree β between the coupled microstrip line and the dielectric resonator. To enhance the circuit's adjustability, the low-impedance microstrip line segment is implemented by adding a metal brass sheet. The position of the brass sheet can be adjusted to achieve optimal coupling. A microstrip interruption structure is added near the terminal of the electrically tuned microstrip line to allow fine-tuning of the frequency selection network's phase delay during debugging to ensure oscillator start-up.

[0053] There are two common power supply methods for FETs: single-supply and dual-supply. Single-supply requires only one positive voltage path, resulting in a simpler structure. Dual-supply requires an additional negative voltage path for the gate, requiring the addition of a negative voltage conversion chip to the DC bias circuit, increasing the circuit size and complexity. Therefore, this design uses a single 9V positive voltage path to power the transistor.

[0054] A drawback of parallel feedback dielectric oscillators is their sensitivity to load pull. A common approach to improve load-pull suppression is to add an isolator to the oscillator output. However, X-band isolators are typically large and do not meet the requirements of miniaturization. This invention employs a buffer amplifier to improve the oscillator's load-pull suppression. The buffer amplifier consists of a monolithic amplifier and operates near the operating frequency. The input reflection coefficient is less than -15dB, which does not affect oscillator operation.

[0055] The power module contains two three-terminal voltage regulators, 7809 and 7805, and bypass filter capacitors, which convert the input 12V voltage into 9V required by the dielectric oscillator and 5V required by the buffer amplifier, minimizing the impact of power supply fluctuations on the operation of the dielectric oscillator and ensuring low phase noise output.

[0056] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0057] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0058] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An X-band voltage-controlled dielectric oscillator, characterized in that: The X-band voltage-controlled dielectric oscillator comprises an active amplification network (1), a frequency selection network (2), a voltage tuning structure (3), a buffer amplifier (4) and a power supply module (5), wherein: The output end of the active amplifying network (1) is respectively connected to the input end of the frequency selection network (2) and the input end of the buffer amplifier (4); the output end of the frequency selection network (2) is connected to the other input end of the active amplifying network (1); the input end of the voltage tuning structure (3) is connected to the tuning voltage, and the output end is connected to the other input end of the frequency selection network (2); the output end of the buffer amplifier (4) is a signal output end, and the power supply module (5) is respectively connected to the active amplifying network (1) and the buffer amplifier (4); The frequency selection network (2) includes a drain microstrip line (11), a gate microstrip line (12) and a cylindrical dielectric resonator (13) located between the two microstrip lines, the other terminal of the gate microstrip line (12) is connected to a matching impedance and then grounded, and the other terminal of the drain microstrip line (11) is open; wherein the relative dielectric constant of the dielectric resonator (13) is 37.5, and the dielectric substrate of the dielectric resonator (13) is a ceramic plate and has a relative dielectric constant of 9.

9.

2. The X-band voltage-controlled dielectric oscillator according to claim 1, wherein: The active amplification network (1) is composed of GaAsFET transistors (16).

3. The X-band voltage-controlled dielectric oscillator according to claim 1, wherein: The voltage tuning structure (3) comprises a tuning microstrip line (14) and a varactor diode (15) connected to each other, and the voltage tuning structure (3) is located on the side of the dielectric resonator (13).

4. The X-band voltage-controlled dielectric oscillator according to claim 1 or 3, characterized in that: A gasket (17) is provided below the dielectric resonator (13), and the gasket (17) is a quartz plate.

5. The X-band voltage-controlled dielectric oscillator according to claim 3, wherein: A low-impedance microstrip line segment (18) is provided above a position of the tuning microstrip line (14) close to the dielectric resonator (13).

6. The X-band voltage-controlled dielectric oscillator according to claim 5, characterized in that: A microstrip interruption structure (19) is added to the terminal of the tuning microstrip line (14), wherein the spacing between the microstrip terminals is 0.2 mm.

7. The X-band voltage-controlled dielectric oscillator according to claim 1, wherein: The modulation voltage loaded on the voltage tuning structure (3) is 0-20V DC.

8. The X-band voltage-controlled dielectric oscillator according to claim 1, wherein: The gain of the buffer amplifier (4) near the resonance point is +18dB, and the input end return loss is less than -15dB.

9. The X-band voltage-controlled dielectric oscillator according to claim 1, wherein: The power supply module (5) includes two three-terminal voltage regulators, namely 7809 and 7805.

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