CN115764260A - Butterfly antenna suitable for embedding meander line of superconducting series Josephson double-crystal junction - Google Patents

Abstract

The invention discloses a bowtie antenna embedded with a meandering line suitable for a superconducting series Josephson double crystal junction, which includes a plurality of low-impedance mixers, and a meandering line metal layer is connected between the plurality of low-impedance mixers; The meandering line metal layers on the left and right edges are connected with a bent line metal layer; one side of the bent line metal layer is connected with a butterfly metal layer; the low impedance mixer is located on the same vertical line, and the vertical line The formed grain boundary line forms a Josephson junction at the superconducting thin film; the grain boundary line is perpendicular to the parallel line formed by the left and right butterfly metal layers. The present invention can complete the low-impedance matching between a single antenna and each series junction, and also prevents the main body of the antenna from being distributed on the double crystal grain boundary with superconducting material so as to avoid the influence of the grain boundary on the Josephson junction mixer connected in series. Reduce water damage to the YBCO film during multiple photolithographic developments in the preparation process.

Description

A Bowie Antenna Embedded with Serpentine Wires Applicable to Superconducting Series Josephson Twin Junctions

technical field

The invention relates to a bowtie antenna embedded with meandering lines suitable for superconducting series Josephson double crystal junctions, which belongs to the field of superconducting and terahertz communication.

Background technique

Superconducting Josephson junctions have great potential for fabricating high-frequency devices such as terahertz emission sources, voltage standards, sensitive detectors, and mixers. The most attractive development currently is the terahertz receiver in terahertz communication. Due to the severe atmospheric attenuation in the terahertz band, the effective detection of ultra-sensitive terahertz receivers faces great challenges. High-temperature superconducting mixers are ideal for THz receiver front-ends because of their high mixing harmonic number, high sensitivity, wide bandwidth, and local oscillator power compared to mixers used to cool low-temperature superconducting devices. Low requirements and low cryogenic cost.

Unlike opto-electronic mixers, which have high resistance, superconducting Josephson junction mixers have fairly low impedance. For example, the typical value of the normal-state resistance of a superconducting Josephson junction made of YBa ₂ Cu ₃ O _7-δ (YBCO) is about 1–40 ohms. The terahertz antenna applied to the mixer should be combined with the mixer A conjugate match is achieved for maximum power transfer. However, conventional antennas do not have such low impedance. For opto-electric hybrids, the impedance of the coupled antenna should be raised to kilo ohms for good impedance matching. In contrast, for superconducting Josephson junction mixers, the coupled antenna impedance should be greatly reduced. There have been reports on reducing the input impedance of coupled antennas to match superconducting Josephson junction mixers. Experiments show that the mixing performance is greatly improved.

On the other hand, a series Josephson junction can improve the impedance of the device, thereby achieving impedance matching with the coupled antenna. Enough series junctions can achieve the impedance of common types of antennas. However, many Josephson junctions in series are difficult to achieve the consistency of processing technology and work in the same phase, and the good mixing performance cannot be improved. The maximum harmonic number of 3 Josephson junction mixers connected in series has been increased to 154. However, the impedance mismatch between the antenna and each series junction still exists. For Josephson junction devices in series, novel antennas with input resistance lower than that of common antenna types under multi-source excitation should be investigated. In particular, for the Josephson junction of the twin crystal structure, because of the fixed position of the grain boundary, the Josephson junction in series must be on the straight line of the grain boundary to form the characteristics of the Josephson junction. In order to reduce the complexity of the preparation process and avoid The main body of the antenna is distributed on the double crystal grain boundary, which causes the influence of the superconducting material at the grain boundary on the Josephson junction mixer in series. The antenna suitable for the series Josephson junction mixer needs to achieve the transmission between a single antenna and each series junction Matching characteristics, and the position of placing the series junction needs to be considered, that is, the incoherence between the antenna body and the connection line of the series junction.

The reported superconducting series Josephson junction mixer is embedded in a meandering line, as shown in Figure 1. In order to maintain the symmetry of the topological network, no excitation source is placed at the central point. The superconducting twin-crystal Josephson junction is formed at the grain boundary. The narrower the superconducting film passing through the junction, the smaller the critical current and the more sensitive the device. If the reported antenna is used in a series double crystal junction mixer, where the grain boundary passes through the antenna (Au layer), the YBCO film under the antenna needs to be etched away, otherwise the supercurrent will be too large and the performance of the device will be damaged. The preparation process is as follows Figure 2 shows. Except for the 4 positions on the center line where the YBCO film is left, the other positions need to be etched away, see step ④. The preparation of the entire chip requires two photolithographic developments. The YBCO film is afraid of water, and the performance of the device will be reduced due to repeated contact with water.

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention provides a bowtie antenna embedded with meandering lines suitable for superconducting series Josephson twin junctions, so as to prevent the main body of the antenna from being distributed on the twin crystal grain boundaries with superconducting materials to avoid The influence of the grain boundary on the Josephson junction mixer connected in series reduces the damage of water to the YBCO film during multiple photolithographic developments in the preparation process.

In order to achieve the above object, the technical solution adopted in the present invention is: a bowtie antenna embedded in a meandering line suitable for superconducting series Josephson twin junctions, including a plurality of low-impedance mixers, a plurality of low-impedance mixers A meandering line metal layer is connected between them; the meandering line metal layer on the left and right edges is connected with a bent line metal layer; one side of the bent line metal layer is connected with a butterfly metal layer; the low impedance mixer is located at On the same vertical line, the grain boundary line formed by the vertical line forms a Josephson junction at the superconducting thin film; the grain boundary line is perpendicular to the parallel line formed by the left and right butterfly metal layers.

Further, the impedance of the low-impedance mixer is 15 ohms; the length and spacing of metal layers of meandering lines connected in series to multiple low-impedance mixers can be different, so as to adjust the size of the active impedance.

Further, the bowtie antenna embedded in the meandering wire operates in traveling wave mode.

Furthermore, the base surface wave effect of the bowtie antenna is eliminated by placing a silicon hyper-hemispherical lens on the back.

Further, the bowtie antenna structure is symmetrical about the central origin.

The beneficial effects of the present invention are: the present invention designs a terahertz antenna with multi-source excitation and low input impedance for the Josephson double junction in series, and embeds a plurality of low-impedance mixers in the terahertz antenna to complete impedance matching and Does not affect antenna performance. At the same time, except for the Josephson junction mixer embedded in the antenna, the main body of the antenna cannot be at the grain boundary forming the Josephson junction, so as to reduce the complexity of the preparation process and improve the sample yield. The meandering lines embedded in the butterfly can be connected to multiple low-impedance mixers to complete impedance matching without affecting the performance of the antenna; the length and spacing of the meandering lines can be adjusted arbitrarily to adjust the active impedance and complete the mixing The low impedance matching of the device; the embedded low impedance mixer can be increased or decreased according to the actual application requirements; the connection line of the series junction is perpendicular to the connection line of a pair of butterfly; the structure is symmetrical about the central origin; the butterfly embedded in the meandering line The shape works in a traveling wave working mode; the invention is applicable to other low-impedance terahertz detectors.

Description of drawings

FIG. 1 is a schematic structural diagram of an existing bow-shaped loaded meander antenna that can be used in series with Josephson junctions;

Fig. 2 is a schematic diagram of the preparation process of an existing antenna used in a superconducting series double crystal junction mixer;

Fig. 3 is a structural diagram of a bowtie antenna connected with meandering lines embedded with seven low-impedance mixers in an embodiment of the present invention;

FIG. 4 is a schematic diagram of the parameters of each component part of the antenna according to the embodiment of the present invention;

Fig. 5 is a simulation comparison diagram of active reflection coefficients of (a) 7 and (b) 5 low-impedance mixers embedded in the meandering line of the embodiment of the present invention;

Fig. 6 is a simulation comparison diagram of far-field radiation directions at (a) 216 GHz and (b) 226 GHz respectively embedded in the serpentine line of the embodiment of the present invention (a) 7 and (b) 5 low-impedance mixers.

In the figure: 1. Low-impedance mixer, 2. Serpentine line metal layer, 3. Bend line metal layer, 4. Butterfly-shaped metal layer, 5. Grain boundary line.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described here are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention, and the terms used in the description of the present invention herein are only to describe specific implementations The purpose of the example is not intended to limit the present invention.

In this embodiment, the design of the present invention is a bowtie antenna embedded with multiple low-impedance mixers connected by meandering lines, and its structure is shown in FIG. 3 . It mainly includes seven low-impedance mixers 1 , a meander metal layer 2 and a bent-line metal layer 3 connecting the low-impedance mixers 1 , and a butterfly metal layer 4 . The impedance of the mixer is about 15 ohms, and the length and spacing of the meandering lines connected to the mixer can vary to adjust the size of the active impedance. The length of the meandering line can be adjusted freely to place the required number of mixers. The grain boundary line 5 of the superconducting material on the substrate, that is, the center line of the meandering line, forms a Josephson junction.

A bowtie antenna embedded in a meandering wire operates in a traveling wave pattern. In practical applications, the length and spacing of the meandering lines can be adjusted to determine the number of series mixers placed, and the length of the butterfly shape can be adjusted to determine the operating frequency; the basal surface wave effect of the terahertz antenna can be adjusted by placing Silicon hyper hemispherical lenses eliminate.

Steps ④-⑦ in Figure 2 can be shortened when preparing samples, and the entire chip layout can be formed together with the Josephson junction.

The key point of the present invention is to design a terahertz antenna with multi-source excitation and low input impedance for the series-connected Josephson double junction, and embed multiple low-impedance mixers in the terahertz antenna to complete impedance matching without affecting the performance of the antenna . At the same time, except for the Josephson junction mixer embedded in the antenna, the main body of the antenna cannot be at the grain boundary forming the Josephson junction, so as to reduce the complexity of the preparation process and improve the sample yield.

=135 μm,

=515 μm,

=30 μm,

=4 μm,

=10 μm, =

=

=4 μm,

=

=

=10 μm,

=17 μm时，7个端口在216 GHz，其 有源反射系数分别为-15 dB，-24 dB，-37 dB，-17 dB，-37 dB，-24 dB和 -15 dB，方向性系 数达7.42 dBi；5个端口激励，除去

和

参数部分的蜿蜒线长度，226 GHz处的有源反射系 数分别为-15 dB，-21 dB，-21 dB，-21 dB和 -15 dB，方向性系数达7.59 dBi。 A design case of the present invention, its schematic diagram is shown in Figure 4. In the CST simulation software, the antenna material is set as an ideal conductor, placed on a magnesium oxide (relative permittivity of 9.6) substrate, and the detectors are represented by discrete ports of 15 ohms, for multi-port active simulation, the meandering line The discrete ports can be increased or decreased according to the actual application, and its active reflection coefficient and far-field radiation pattern are shown in Figure 5 and Figure 6, respectively. When the antenna parameters

=135 μm,

=515 μm,

=30μm,

=4μm,

=10 μm, =

=

=4μm,

=

=

=10μm,

=17 μm, 7 ports at 216 GHz, their active reflection coefficients are -15 dB, -24 dB, -37 dB, -17 dB, -37 dB, -24 dB and -15 dB, directivity coefficient Up to 7.42 dBi; 5 port excitation, except

and

The length of the meander line in the parameter section, the active reflection coefficient at 226 GHz are -15 dB, -21 dB, -21 dB, -21 dB and -15 dB respectively, and the directivity coefficient reaches 7.59 dBi.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modification, equivalent replacement or improvement made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (5)

1. A butterfly antenna with embedded meander line suitable for superconducting serial Josephson double crystal junction is characterized in that the butterfly antenna comprises a plurality of low impedance mixers (1), a meander line metal layer (2) is connected between the low impedance mixers (1); the meander line metal layers (2) at the edges of the left side and the right side are connected with a meander line metal layer (3); one side of the bent line metal layer (3) is connected with a butterfly metal layer (4); the low-impedance mixers (1) are positioned on the same vertical line, and a grain boundary line (5) formed by the vertical line is formed into a Josephson junction at the superconducting thin film; the grain boundary line (5) is vertical to a parallel line formed by the left butterfly metal layer and the right butterfly metal layer (4).

2. A meander line embedded butterfly antenna applicable for superconducting serial josephson bicrystal junction according to claim 1, wherein the impedance of the low impedance mixer (1) is 15 Ω; the length and the spacing of the meander line metal layers (2) connecting the 7 low impedance mixers (1) in series can be different, so as to adjust the size of the active impedance.

3. The embedded meander line bowtie antenna adapted for a superconducting serial josephson twin junction as claimed in claim 1, wherein the embedded meander line bowtie antenna operates in a traveling wave mode.

4. The embedded meander line bowtie antenna for superconducting serial josephson twin junction as claimed in claim 1, wherein the substrate surface wave effect of bowtie antenna is eliminated by placing a silicon hyper-hemispherical lens on the back side.

5. The meander-line embedded bowtie antenna suitable for a superconducting serial josephson bicrystal junction as claimed in claim 1, wherein the bowtie antenna structure is symmetric about a central origin.

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