CN114337546A - A Low Phase Noise Oscillator Based on Substrate Integrated Waveguide Filter Hybrid Network - Google Patents

Abstract

The invention discloses a low-phase noise oscillator based on a substrate integrated waveguide filter hybrid network, which comprises a substrate integrated waveguide filter hybrid network, an active amplification unit and a loop phase modulation microstrip line, wherein the active amplification unit is connected with the substrate integrated waveguide filter hybrid network; the substrate integrated waveguide filter hybrid network comprises a top feed layer, a middle air substrate integrated waveguide resonant cavity and a bottom metal structure; the in-phase input port of the substrate integrated waveguide filter hybrid network is connected with the input end of the active amplification unit, the first output port of the substrate integrated waveguide filter hybrid network is connected with the output end of the active amplification unit, the second output port of the substrate integrated waveguide filter hybrid network is connected with the signal output port of the oscillator, the out-phase input port of the substrate integrated waveguide filter hybrid network is connected with the matched load, and the loop phase modulation microstrip line is connected with the substrate integrated waveguide filter hybrid network and the active amplification unit. The invention not only can effectively improve the quality factor and reduce the phase noise of the oscillator, but also can realize good impedance matching and compact circuit size.

Description

A Low Phase Noise Oscillator Based on Substrate Integrated Waveguide Filtering Hybrid Network

technical field

The invention relates to the field of microwave and millimeter-wave substrate integrated waveguide active devices, in particular to a low phase noise oscillator based on a filter function substrate integrated waveguide hybrid network.

Background technique

With the rapid development of the fifth-generation mobile communication (5G) system, the microwave and millimeter-wave frequency band mobile communication systems with high integration and high data transmission capacity have received extensive attention from all walks of life. 5G communication technology will have more spectrum resources, higher spectrum utilization and denser network deployment. The oscillator is the core device in the communication system, and its performance directly determines the performance of the entire system. Among them, phase noise and circuit size are two key indicators of oscillators. Traditional oscillators include dielectric oscillators, metal waveguide oscillators, etc. Although they have a very high quality factor and obtain good phase noise characteristics, the above oscillators all have problems such as large size and weight, difficult to assemble and debug, and difficult to integrate with planar circuits. Realize miniaturization and integrated integrated design. In order to solve the above problems, some oscillators with planar transmission structures have gradually attracted extensive attention from all walks of life.

Substrate-integrated waveguide (SIW) is a new type of planar transmission structure, which is widely used in various device designs due to its advantages of low loss, high quality factor, good shielding properties, large power capacity, and easy planar integration. SIW is much lower than traditional metal waveguides in terms of weight, volume, processing cost, production cycle, etc., especially in the microwave and millimeter-wave frequency bands with higher frequencies, SIW can effectively solve the problems of microstrip conductor loss and large radiation loss. The signal transmission loss is smaller, and it is not sensitive to processing errors, and it is not easy to introduce alien crosstalk signals, resulting in a sharp deterioration of system performance. Therefore, SIW becomes a powerful choice to replace traditional microstrip and metal waveguide devices.

In recent years, feedback oscillators based on SIW resonators have been reported in the literature, and their phase noise performance is excellent. However, there are two problems with SIW oscillators. On the one hand, it is difficult to realize an oscillator with low phase noise at high frequency, so it is necessary to construct a planar resonant unit with a higher quality factor. On the other hand, cascade couplers are often required in the loop of the feedback oscillator, which leads to a significant increase in the size of the oscillator circuit, and also introduces large losses in the loop, which cannot meet future miniaturization, integration, and integration. communication system needs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an oscillator based on a substrate-integrated waveguide filter coupling network capable of simultaneously reducing phase noise and reducing circuit size.

To achieve this purpose, the technical scheme adopted in the present invention is as follows:

A low phase noise oscillator based on a substrate integrated waveguide filtering hybrid network, comprising a substrate integrated waveguide filtering hybrid network, an active amplifying unit and a loop phase modulation microstrip line; the substrate integrated waveguide filtering hybrid network includes The top feeding layer, the middle air substrate integrated waveguide resonant cavity and the bottom metal structure; the non-inverting input port of the substrate integrated waveguide filtering hybrid network is connected to the input end of the active amplifying unit, and the substrate integrated waveguide filtering hybrid network The first output The port is connected to the output end of the active amplifying unit, the second output port of the substrate-integrated waveguide filtering hybrid network is connected to the signal output port of the oscillator, the inverting input port of the substrate-integrated waveguide filtering hybrid network is connected to the matching load, and the loop adjustment The phase microstrip line connects the substrate integrated waveguide filtering hybrid network and the active amplifying unit.

Further, the top feeding part of the substrate-integrated waveguide filtering hybrid network adopts a slot coupling structure.

Further, the air resonant cavity in the middle layer of the substrate-integrated waveguide filtering hybrid network is square.

Further, the high-order mode in the intermediate layer air resonant cavity of the substrate-integrated waveguide filtering hybrid network is set at the operating frequency of the oscillator.

Further, the active amplifying unit includes an ultra-low noise transistor, an input/output matching circuit and a bias circuit.

Compared with the prior art, the present invention has the following significant advantages: the present invention adopts the substrate integrated waveguide filtering hybrid network as the frequency selection unit and matching network of the oscillator, and saves additional cascaded couplers or power dividers in the loop. , which not only effectively reduces the circuit size and loss, but also achieves low phase noise characteristics; the substrate-integrated waveguide filtering hybrid network utilizes a high-order mode air substrate integrated waveguide cavity, which is integrated with other traditional microstrip and substrate integrated waveguides. Compared with the circuit, it has higher quality factor value and lower insertion loss.

Description of drawings

1 is a structural diagram of a substrate-integrated waveguide filtering hybrid network oscillator in a specific embodiment of the present invention;

2 is a three-dimensional structural diagram of a substrate-integrated waveguide filtering hybrid network in a specific embodiment of the present invention;

3 is an amplitude frequency response curve of a substrate integrated waveguide filtering hybrid network oscillator in a specific embodiment of the present invention;

FIG. 4 is a phase noise curve of a substrate-integrated waveguide filtering hybrid network oscillator in a specific embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be further introduced below with reference to the specific embodiments and the accompanying drawings.

This specific embodiment discloses a low phase noise oscillator based on a substrate integrated waveguide filtering hybrid network, as shown in FIG. 1 , including a substrate integrated waveguide filtering hybrid network 1 , an active amplifying unit 2 and a loop phase modulation micro Strip line 3. The substrate-integrated waveguide filtering hybrid network 1 includes a top feeding layer 4 , a middle air substrate-integrated waveguide resonant cavity 5 and a bottom metal structure 6 , and the three-dimensional structure is shown in FIG. 2 . Among them, the upper surface of the top feeding layer includes four feeding ports, namely the non-inverting input port 7, the first output port 8, the second output port 9 and the inverting input port 10, and the non-inverting input port 7 passes through the loop The phase modulation microstrip line 3 is connected to the input end of the active amplifier unit 2, the first output port 8 is connected to the output end of the active amplifier unit 2, the second output port 9 is connected to the signal output port of the oscillator, and the inverting input port 10 Connect matching load 11.

In a further embodiment, the lower surface of the top feeding layer adopts a slot coupling structure 17 .

In a further embodiment, the intermediate air-substrate integrated waveguide resonant cavity 16 is a square, including an array of metallized vias 18 around it and a dielectric portion hollowed out in the middle. The higher-order modes in the air-substrate integrated waveguide resonator are set at the operating frequency of the oscillator.

In order to ensure that the energy leaking from the through holes in the microwave and millimeter wave frequency bands is as small as possible, in the flat printed circuit board process, the spacing d of the metallized through holes is usually selected as 0.3-1mm, and the through-hole spacing p is usually selected as 0.6- 2mm, the side lengths of the equivalent metal rectangular waveguide resonator are W _eff and L _eff respectively, and the side lengths of the air-substrate integrated waveguide resonator 16 in the present invention are W and L respectively. When the resonator is in the working condition of high-order mode, its resonant frequency can be calculated by the following formula:

和

表示高次模谐振频率，c表示光在真空中传播速度，μ_r表示介质基板的相对磁导率，ε_r表示介质基板相对介电常数。in

and

Represents the high-order mode resonance frequency, c represents the propagation speed of light in a vacuum, μ _r represents the relative permeability of the dielectric substrate, and ε _r represents the relative permittivity of the dielectric substrate.

In this specific embodiment, the top dielectric substrate of the substrate-integrated waveguide filtering 180° hybrid network is Taconic TLY-5, with a thickness of 0.508mm, the middle layer dielectric substrate is Taconic TLY-5, and the hollowed-out dielectric is partially replaced by air, with a thickness of 0.508 mm. It is 1.016mm, the bottom layer is made of silver-plated aluminum structure, and the thickness is 5mm. Using the mechanism of high-order mode air cavity with high quality factor, and integrating the filter and 180° hybrid network, a multifunctional device with high integration and high quality factor is realized, which is used for frequency selection in oscillator design, Impedance matching and signal output.

The active amplifying unit is shown in FIG. 1 and includes an active transistor (12), an input matching network (13), an output matching network (14) and two bias circuits (15). The active amplifying unit is arranged on the top dielectric substrate. In order to compensate the loss of the filter hybrid network as a frequency selective device, the gain required by the loop is provided so that it can satisfy the start-up condition that the amplitude is greater than 1 in the Barkhausen criterion.

According to the substrate-integrated waveguide filtering hybrid network and the active amplifying unit designed above, the oscillator in this specific embodiment is implemented by adopting a parallel feedback topology. The loop phase of the oscillator is adjusted by adjusting the length of the phase-shifted microstrip line (3), so that it satisfies the start-up condition that the loop phase is equal to 0° or an integer multiple of 360° in the Barkhausen criterion.

In the present invention, the substrate-integrated waveguide filtering hybrid network (1), the active amplifying unit (2), and the phase-modulated microstrip line (3) form a feedback oscillator loop. The signal is amplified by the active amplifying unit (2), input from the port (8) of the substrate-integrated waveguide filtering hybrid network (1), and output from the port (7) to the phase modulation microstrip (3) after passing through the multifunctional frequency selection device The lines form a closed loop. When the oscillator satisfies the Barkhausen criterion, that is, the gain in the entire feedback loop is 1 and the phase satisfies 0° or an integer multiple of 360°, the desired oscillator signal is output from port (9).

FIG. 3 is a frequency response curve of the specific embodiment. In this example, the output frequency of the oscillator is 10GHz, and the output power is -0.5dBm; the frequency of the second harmonic is 20GHz, and the output power is -75.2dBm. FIG. 4 is a phase noise curve in an embodiment, the phase noise at 100 kHz off the center frequency is -122.5dBc/Hz, and the phase noise at 1 MHz off the center frequency is -142.6dBc/Hz.

Claims (6)

1. A low phase noise oscillator based on a substrate integrated waveguide filter hybrid network is characterized in that: the device comprises a substrate integrated waveguide filtering hybrid network (1), an active amplification unit (2) and a loop phase modulation microstrip line (3); the substrate integrated waveguide filter hybrid network comprises a top feed layer (4), a middle air substrate integrated waveguide resonant cavity (5) and a bottom metal structure (6); the in-phase input port (7) of the substrate integrated waveguide filter hybrid network is connected with the input end of the active amplification unit (2) through the loop phase modulation microstrip line (3), the first output port (8) of the substrate integrated waveguide filter hybrid network is connected with the output end of the active amplification unit (2), the second output port (9) of the substrate integrated waveguide filter hybrid network is used as a signal output port of the oscillator, the reverse phase input port (10) of the substrate integrated waveguide filter hybrid network is connected with the matched load (11), and the loop phase modulation microstrip line is connected with the substrate integrated waveguide filter hybrid network and the active amplification unit.

2. The substrate integrated waveguide filter hybrid network based low phase noise oscillator according to claim 1, wherein: and a feed layer (4) of the substrate integrated waveguide filter hybrid network adopts a gap coupling structure.

3. The substrate integrated waveguide filter hybrid network based low phase noise oscillator according to claim 1, wherein: the air substrate integrated waveguide resonant cavity (5) of the substrate integrated waveguide filter hybrid network is square.

4. The substrate integrated waveguide filter hybrid network based low phase noise oscillator according to claim 1, wherein: the high-order mode of an air substrate integrated waveguide resonant cavity (5) of the substrate integrated waveguide filter hybrid network is set at the working frequency point of the oscillator.

5. The substrate integrated waveguide filter hybrid network based low phase noise oscillator according to claim 1, wherein: the active amplification unit comprises an input matching circuit, a bias circuit, an ultra-low noise transistor, a bias circuit and an output matching circuit which are connected in sequence.

6. The substrate integrated waveguide filter hybrid network based low phase noise oscillator according to claim 1, wherein: the loop phase is adjusted by adjusting the length of the phase-shifting microstrip line (3), and the oscillation starting condition that the loop phase is equal to 0 degree or integral multiple of 360 degrees in the Barkhausen criterion is met.

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