Broadband Fully Differential Double-Sided Parallel Strip Line to Coplanar Waveguide Transducer and RF Circuit

Abstract

The present invention discloses a broadband fully differential double-sided parallel strip line to coplanar strip line adapter and a radio frequency circuit. The adapter includes a dielectric substrate, on which a double-sided parallel strip line is provided. A first conductor is etched on the upper surface of the dielectric substrate, and a second conductor is etched on the lower surface of the dielectric substrate. The first conductor includes a first arm and a second arm. The first end of the first arm and the first end of the second conductor are respectively connected to the upper and lower conductors of the double-sided parallel strip line. The first end of the first arm is flush with the first end of the second conductor. The first end of the second arm is flush with the second end of the second conductor. The second ends of the first arm and the second arm converge without intersecting and extend in a parallel structure to form a coplanar strip line. The present invention does not require the use of vias and can achieve conversion only through the coupling of the upper and lower metal lines of the dielectric substrate, and maintain the differential performance after conversion.

Description

Technical Field

[0001] The present invention relates to a broadband fully differential double-sided parallel strip line to coplanar strip line adapter and a radio frequency circuit, belonging to the technical field of radio frequency circuits for wireless communication. Background Art

[0002] Both the double-sided parallel strip line and the coplanar strip line are common transmission lines in the radio frequency field. They have simple structures, low costs, and are easy to integrate. They are widely used in antenna and circuit structures. Their common feature is that there is a differential characteristic between the two conductors, that is, the currents always maintain equal amplitude and opposite directions. Among them, the double-sided parallel strip line can be used to provide a differential feeding signal for a double-sided designed antenna, so as to obtain a stable and symmetric radiation pattern; while the coplanar strip line, as a traditional two-wire circuit structure, can bridge components such as capacitors, inductors, and diodes on the same plane.

[0003] In the existing reports on double-sided parallel strip line to coplanar strip line, the most common structure is to directly drill vias to conduct the strip lines on different surfaces to the same surface to achieve structural conversion. However, the size of the vias will affect the current distribution, and drilling the vias itself will further introduce processing errors. At the same time, the vias will increase the processing complexity and cost. Therefore, it is very important to design a via-free adapter. However, the via-free design also needs to consider the bandwidth problem. With the development of current wireless communication, the demand for broadband characteristics increases, so the bandwidth of the structure needs to be expanded. At present, although the return loss of some structures is below -10 dB in a relatively wide frequency band, it is difficult to guarantee the current differential performance in the whole frequency band. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned disadvantages and deficiencies of the prior art, and provide a broadband fully differential double-sided parallel strip line to coplanar strip line adapter. This adapter does not need to use vias and can achieve conversion only through the coupling of the metal wires on the upper and lower layers of the dielectric substrate, and maintain the differential performance after conversion.

[0005] Another purpose of the present invention is to provide a radio frequency circuit.

[0006] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0007] A broadband fully differential double-sided parallel strip line to coplanar strip line adapter includes a dielectric substrate. The dielectric substrate is provided with a double-sided parallel strip line. The upper surface of the dielectric substrate is etched with a first wire, and the lower surface of the dielectric substrate is etched with a second wire. The first wire includes a first arm and a second arm. The first end of the first arm and the first end of the second wire are respectively connected to the upper and lower wires of the double-sided parallel strip line. The first end of the first arm is flush with the first end of the second wire. The first end of the second arm is flush with the second end of the second wire. The second ends of the first arm and the second arm converge and do not intersect, and extend in a parallel structure to form a coplanar strip line.

[0008] Further, the second wire is folded into a rectangle, and the second end of the second wire is located near the first end of the second wire.

[0009] Further, the width of the second end of the first arm, the width of the second end of the second arm, and the width of the second wire at the corresponding positions of the second ends of the first arm and the second arm are the same as the width of the coplanar strip line.

[0010] Further, a rectangular loop is formed between the first arm and the second arm, and the first end of the second arm is located near the first end of the first arm.

[0011] Further, the first ends of the first arm, the second arm, the first end of the second wire, and the second end of the second wire are widened outward and chamfered near the double-sided parallel strip line, and the width gradually decreases along the direction of the coplanar strip line.

[0012] Further, the second ends of the first arm and the second arm are chamfered near the coplanar strip line.

[0013] Further, the total length of the second wire is half a wavelength at the center frequency.

[0014] Further, the first end of the first arm and the first end of the second wire have the same width and the same direction, and the length of the first arm is 1 / 2 of the total length of the second wire.

[0015] Further, the first end of the second arm and the second end of the second wire have the same width and the same direction, and the length of the second arm is 1 / 2 of the total length of the second wire.

[0016] Another object of the present invention can be achieved by adopting the following technical solutions:

[0017] A radio frequency circuit includes the above-mentioned broadband fully differential double-sided parallel strip line to coplanar strip line adapter.

[0018] The present invention has the following beneficial effects compared with the prior art:

[0019] The present invention only uses the upper and lower surfaces of the dielectric substrate. By arranging wires on the upper and lower surfaces, no vias need to be drilled during processing. The frequency range that can be covered with a return loss within -10 dB is 1.85 GHz - 2.45 GHz, and the relative bandwidth is 27%. The insertion loss remains within 0.5 dB; after conversion by the adapter, the current of the coplanar strip line remains fully differential, that is, equal amplitude and opposite direction. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0021] Figure 1 Stereogram of the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0022] Figure 2 Top view of the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0023] Figure 3 Bottom view of the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0024] Figure 4 S-parameter simulation result diagram of the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0025] Figure 5 Simulation result diagram of the surface current direction of the first conductor in the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0026] Figure 6 Simulation result diagram of the surface current direction of the second conductor in the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0027] Figure 7 Simulation result diagram of the surface current density of the coplanar waveguide in the broadband fully differential double-sided parallel strip line to coplanar waveguide adapter according to an embodiment of the present invention.

[0028] Wherein, 1 - dielectric substrate, 2 - double-sided parallel strip line, 3 - coplanar waveguide, 4 - first arm, 5 - second arm, 6 - second conductor. Specific embodiments

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] Embodiment:

[0031] As Figures 1 to 3As shown in the figure, this embodiment provides a broadband fully differential double-sided parallel strip line to coplanar waveguide adapter, which can be applied to the radio frequency circuits of various wireless communication devices. It includes a dielectric substrate 1, on which a double-sided parallel strip line 2 is provided. The upper surface of the dielectric substrate 1 is etched with a first conductor, and the lower surface of the dielectric substrate 1 is etched with a second conductor 6. The first conductor includes a first arm 4 and a second arm 5, where the first arm 4 is the left arm and the second arm 5 is the right arm. The currents of the first arm 4 and the second arm 5 are equal in amplitude and opposite in direction. The first conductor and the second conductor 6 serve as a conversion structure.

[0032] In this embodiment, the first arm 4, the second arm 5, and the second conductor 6 all have a first end and a second end, where the first end is the starting end and the second end is the ending end. The first end of the first arm 4 and the first end of the second conductor 6 are respectively connected to the upper and lower conductors of the double-sided parallel strip line 2, and electromagnetic waves are fed into the double-sided parallel strip line 2. The first end of the first arm 4 is flush with the first end of the second conductor 6, the first end of the second arm 5 is flush with the second end of the second conductor 6, and the second end of the first arm 4 converges with the second end of the second arm 5 without intersecting, and extends in a parallel structure to form a coplanar waveguide 3.

[0033] Further, the second conductor 6 is folded into a rectangle, that is, a rectangular loop is formed in the middle of the second conductor 6, and the second end of the second conductor 6 is located near the first end of the second conductor 6; a rectangular loop is formed between the first arm 4 and the second arm 5, and the first end of the second arm 5 is located near the first end of the first arm 4.

[0034] To achieve a larger bandwidth, the first end of the first arm 4, the first end of the second arm 5, the first end of the second conductor 6, and the second end of the second conductor 6 are widened outward and chamfered near the double-sided parallel strip line, and the width gradually decreases along the direction of the coplanar waveguide 3, forming a fan-shaped structure; at the same time, the second end of the first arm 4 and the second end of the second arm 5 are chamfered near the coplanar waveguide, which can make the overall current smoother and the matching better.

[0035] Further, the total length of the second conductor 6 is half a wavelength at the center frequency, which can ensure that the currents of the first arm 4 and the second arm 5 are equal in amplitude and opposite in direction, so as to maintain the differential characteristics of the coplanar waveguide 3; the first end of the first arm 4 and the first end of the second conductor 6 are of equal width and have the same orientation, and the length of the first arm 4 is 1 / 2 of the total length of the second conductor 6; the first end of the second arm 5 and the second end of the second conductor 6 are of equal width and have the same orientation, and the length of the second arm 5 is 1 / 2 of the total length of the second conductor.

[0036] In this embodiment, the material of the dielectric substrate 1 is Rogers 5880, with a dielectric constant of 2.2, a loss tangent of 0.0009, and dimensions of 24 mm * 15 mm * 0.762 mm. The input impedance of the double-sided parallel strip line 2 is set to 180 Ohm, that is, the width of the upper and lower conductors of the double-sided parallel strip line 2 is 0.38 mm. The input impedance of the coplanar strip line 3 is 180 Ohm, that is, the width of the left and right conductors of the coplanar strip line 3 is 0.38 mm, and the spacing is 0.3 mm. The width of the widest part of the first end where the first arm 4, the second arm 5, and the second conductor 6 are connected to the double-sided parallel strip line 2 is 1.2 mm, and the chamfer length is 2 mm. When the width and chamfer length are too large, it will affect the matching. The width of the second end where the first arm 4 and the second arm 5 are connected to the coplanar strip line 3 is the same as the width of the coplanar strip line 3. Similarly, the width of the second conductor 6 at the corresponding positions of the second ends of the first arm 4 and the second arm 5 is also the same as the width of the coplanar strip line 3 to ensure smooth transition. The sizes of the rectangular loops formed between the first arm 4 and the second arm 5 and the rectangular loop formed in the middle of the second conductor 6 are both 1.6 mm * 19 mm. This size perimeter is approximately half of the wavelength of the working center frequency. When working at high frequencies, the length of the rectangular loop can be reduced. In addition, the adapter in this embodiment does not involve vias, which can greatly reduce the processing complexity and error introduction.

[0037] As Figure 4 shown, it is the S-parameter simulation result diagram of the broadband fully differential double-sided parallel strip line to coplanar strip line adapter of the embodiment. It can be seen from the figure that the frequency range that can be covered when the return loss S(1,1) is within -10 dB is 1.85 GHz - 2.45 GHz, and the relative bandwidth is 27%, while the insertion loss S(2,1) remains within 0.5 dB.

[0038] As Figure 5 、 Figure 6 and Figure 7 shown, they are respectively the simulation result diagram of the surface current direction of the first conductor, the simulation result diagram of the surface current direction of the second conductor, and the simulation result diagram of the surface current density of the coplanar strip line in the broadband fully differential double-sided parallel strip line to coplanar strip line adapter of the embodiment of the present invention. It can be seen from the figure that after the conversion of the adapter, the current directions of the coplanar strip lines are opposite, and the current densities are almost equal, that is, it remains fully differential.

[0039] In summary, the present invention only uses the upper and lower surfaces of the dielectric substrate, and realizes the conversion by setting conductors on the upper and lower surfaces and performing coupling. Processing does not require vias. The frequency range that can be covered when the return loss is within -10 dB is 1.85 GHz - 2.45 GHz, and the relative bandwidth is 27%, while the insertion loss remains within 0.5 dB. After the conversion of the adapter, the current of the coplanar strip line remains fully differential, that is, equal amplitude and opposite direction.

[0040] As mentioned above, the above is only a preferred embodiment of the present invention patent, but the protection scope of the present invention patent is not limited thereto. Any person skilled in the art within the scope disclosed by the present invention patent, according to the technical solution and inventive concept of the present invention patent, makes equivalent substitutions or changes, and all belong to the protection scope of the present invention patent.

Claims

1. A broadband fully differential double-sided parallel stripline to coplanar stripline adapter, characterized in that: The invention comprises a dielectric substrate, wherein the dielectric substrate is provided with a double-sided parallel strip line, a first conductor is etched on the upper surface of the dielectric substrate, and a second conductor is etched on the lower surface of the dielectric substrate, wherein the first conductor comprises a first arm and a second arm, wherein the first end of the first arm and the first end of the second conductor are respectively connected to the upper conductor and the lower conductor of the double-sided parallel strip line, wherein the first end of the first arm is flush with the first end of the second conductor, and the first end of the second arm is flush with the second end of the second conductor, and the second end of the first arm is merged with the second end of the second arm without intersecting, and the two ends are transformed into a parallel structure and extended to form a coplanar strip line, wherein the total length of the second conductor is half a wavelength at the center frequency, so that the currents of the first arm and the second arm are equal in amplitude and opposite in direction, thereby maintaining the differential characteristics of the coplanar strip line.

2. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to claim 1, characterized in that: The second conductive wire is folded into a rectangle, and the second end of the second conductive wire is located near the first end of the second conductive wire.

3. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to claim 2, characterized in that: The width of the second end of the first arm, the width of the second end of the second arm, and the width of the second wire at the corresponding position of the second end of the first arm and the second end of the second arm are consistent with the width of the coplanar strip line.

4. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to claim 1, characterized in that: A rectangular circle is formed between the first arm and the second arm, and the first end of the second arm is located near the first end of the first arm.

5. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to claim 1, characterized in that: The first end of the first arm, the first end of the second arm, the first end of the second wire, and the second end of the second wire are widened outward and cut at angles near the double-sided parallel strip lines, and the width gradually decreases along the coplanar strip lines.

6. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to claim 1, characterized in that: The second end of the first arm and the second end of the second arm are chamfered near the coplanar strip line.

7. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to any one of claims 1 to 6, characterized in that: The first end of the first arm and the first end of the second wire have the same width and the same direction, and the length of the first arm is 1 / 2 of the total length of the second wire.

8. The broadband fully differential double-sided parallel stripline to coplanar stripline adapter according to any one of claims 1 to 6, characterized in that: The first end of the second arm and the second end of the second wire have the same width and the same direction, and the length of the second arm is 1 / 2 of the total length of the second wire.

9. A radio frequency circuit, characterized in that: A broadband fully differential double-sided parallel stripline to coplanar stripline adapter comprising any one of claims 1 to 8.

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