Second harmonic image frequency rejection mixer for DGS filtering

Abstract

The invention relates to a design of a DGS filtering second harmonic image frequency rejection mixer, and belongs to the technical field of microwave circuits. The mixer comprises two Wilkinson power divider modules, a phase shift line module, two DGS filtering second harmonic mixing modules and an intermediate frequency lumped LC phase shift module. The Wilkinson power divider module at the radio frequency input end is divided into two paths to be supplied to the phase shift line module and the second harmonic frequency mixing module for DGS filtering; the output end of the phase shift line is connected with the input end of the DGS filtering second harmonic frequency mixing module; the Wilkinson power divider module at the input end of the local oscillator is divided into two parts to be supplied to the second harmonic frequency mixing module of two DGS filtering; the two input ends of the intermediate frequency lumped LC phase shift module are connected with the output ends of the two DGS filtering second harmonic frequency mixing modules respectively. The output end of the intermediate frequency lumped LC phase shift module is a total output end. According to the invention, the interference of the image frequency signal can be effectively suppressed, the system cost is saved, and an important technical support is provided for realizing a high-performance communication system.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave circuits and relates to the design of a second-harmonic image-rejection mixer with DGS filtering. Background Art

[0002] Frequency conversion, as one of the key technologies for processing radio frequency (RF) signals, is widely used in many microwave systems such as wireless communication, remote sensing, radar, and navigation. A mixer is the core device for realizing frequency conversion and can perform up- and down-frequency conversion on RF signals.

[0003] Modern communication systems widely adopt superheterodyne receivers. When receiving single-sideband signals, superheterodyne receivers are extremely vulnerable to the interference of image-frequency signals, which can lead to signal distortion and performance degradation, and damage the reliability of the communication system. Therefore, image-frequency rejection is very important.

[0004] Introducing a DGS filtering structure into the mixer can optimize the performance and characteristics of the filter by changing the shape and parameters of the defects. It not only has a small volume and is easy to integrate, but also obtains good harmonic suppression effects in high-frequency applications. The application of harmonic technology can reduce the frequency of the local oscillator signal to a very low level, reducing the cost of using a high-frequency local oscillator source. Secondly, using the phase difference between two signals to achieve image-frequency rejection, it does not require an image-frequency rejection filter and does not require multiple frequency conversions. Therefore, it obtains good performance in systems with high signal frequencies and low intermediate frequencies. And when the signal frequency changes, the image-rejection mixer can also automatically identify the corresponding image frequency. Thus, it can be used in broadband systems and can effectively suppress the interference of image-frequency signals.

[0005] In summary, combining the image-rejection mixer structure with the harmonic mixing technology of DGS filtering and applying it to systems with high-frequency bands and low intermediate frequencies can effectively suppress the interference of image-frequency signals, save system costs, obtain the intermediate-frequency signals required for the best output, and provide an important technical support for realizing high-performance communication systems. Therefore, researching an image-rejection harmonic mixer with excellent performance of DGS filtering has important value and significance. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a second-harmonic image-rejection mixer with DGS filtering, improve the port isolation of the mixer, obtain a high image-rejection ratio, and reduce the cost of the system.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A second-harmonic image rejection mixer with DGS filtering, comprising a radio frequency Wilkinson power divider module 1, a phase-shifting line module 2, DGS-filtered second-harmonic unit mixer modules 3 and 4, a local oscillator Wilkinson power divider module 5, and an intermediate frequency lumped LC phase-shifting module 6.

[0009] Further, the DGS-filtered second-harmonic mixer modules 3 and 4 include Schottky diodes SD1, SD2, a ground GND, dumbbell-shaped defect ground structures DGS, microstrip transmission lines 7, 8, 9, 10, 11, 12, 13, 15, 19, open-circuit microstrip stub lines 14, 16, 18, and short-circuit microstrip stub lines 17. The left end of the microstrip transmission line 7 serves as the radio frequency input terminal of the unit mixer, the right end of the microstrip transmission line 19 serves as the local oscillator input terminal of the unit mixer, and the upper end of the microstrip transmission line 13 serves as the intermediate frequency total output terminal of the unit mixer.

[0010] The above-mentioned microstrip transmission lines 7 and 8, and microstrip transmission lines 11 and 12 are respectively connected in parallel, and have equal length and width; the microstrip transmission lines 9 and 10 are connected in parallel, and have equal length and width; they have radio frequency band-pass filtering functions.

[0011] Further, the dumbbell-shaped defect ground structure DGS is on the ground plane of the microstrip transmission line 13, and by changing the shape and parameters of the defect, good suppression effects are achieved in high-frequency applications.

[0012] The line length of the above-mentioned dumbbell-shaped defect ground structure DGS is L4 = 5.00 mm, and the line width is W4 = 3.00 mm.

[0013] Further, the phase-shifting line module and the intermediate frequency lumped LC phase-shifting module have a 90° phase shift.

[0014] Preferably, this mixer uses a Rogers5880 dielectric substrate with a thickness of 0.254 mm and a dielectric constant of 2.2.

[0015] Preferably, this mixer uses a GaAs process Schottky diode DMK2308.

[0016] Preferably, the Schottky diodes SD1 and SD2 are connected in reverse parallel and are used as frequency conversion devices.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention introduces a phase-balanced image frequency rejection structure, harmonic technology, and DGS filtering structure into a mixer. By changing the shape and parameters of the defects, the performance and characteristics of the filter can be optimized. It not only has a small volume and is easy to integrate, but also achieves good harmonic suppression effects in high-frequency applications. The application of harmonic technology can reduce the frequency of the local oscillator signal to a very low level, reducing the cost of using a high-frequency local oscillator source. Secondly, by using the phase difference between two signals to achieve image frequency rejection, it does not require an image frequency rejection filter or multiple frequency conversions. Therefore, it can obtain good performance in systems with high signal frequencies and low intermediate frequencies. Moreover, when the signal frequency changes, the image frequency rejection mixer can automatically identify the corresponding image frequency. Thus, it can be used in broadband systems and effectively suppress the interference of image frequency signals.

[0019] In summary, the entire mixer achieves a high image frequency rejection ratio in high-frequency applications, good port isolation, and also reduces the system cost, providing an important technical support for the realization of high-performance communication systems, and having strong practicability and application prospects.

[0020] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail with reference to the accompanying drawings, where:

[0022] Figure 1 is the overall structure diagram of a second-harmonic image frequency rejection mixer with DGS filtering according to the present invention;

[0023] Figure 2 is the specific structure diagram of the second-harmonic unit mixing module with DGS filtering;

[0024] Figure 3 is the specific dimension marking diagram of the second-harmonic unit mixing module with DGS filtering in this embodiment;

[0025] Figure 4 is the result diagram of the image frequency rejection ratio IRR versus the RF input in this embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0026] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0027] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0028] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0029] Please refer to Figures 1 to 3 , Figure 1Shown is a second-harmonic image rejection mixer with DGS filtering. The mixer specifically includes: a radio frequency Wilkinson power divider module 1, a phase shifter line module 2, second-harmonic unit mixer modules 3 and 4 with DGS filtering, a local oscillator Wilkinson power divider module 5, and an intermediate frequency lumped LC phase shifter module 6. Among them, the radio frequency input Wilkinson power divider module divides into two paths to supply the phase shifter line module and the second-harmonic mixer module with DGS filtering; the output end of the phase shifter line is connected to the input end of the second-harmonic mixer module with DGS filtering; the local oscillator input Wilkinson power divider module divides into two paths to supply two second-harmonic mixer modules with DGS filtering; the two input ends of the intermediate frequency lumped LC phase shifter module are respectively connected to the output ends of the two second-harmonic mixer modules with DGS filtering; the output end of the intermediate frequency lumped LC phase shifter module is the total output end; at the input end, a Wilkinson power divider and a 1 / 4 radio frequency wavelength microstrip line are used to replace the traditional 3 dB quadrature coupler, and the 1 / 4 radio frequency wavelength microstrip line generates a 90° phase difference between the two input radio frequency signals. At the intermediate frequency output end, a lumped parameter LC network is used to implement a phase-balanced image rejection structure with 90° phase shift.

[0030] As Figure 2 shown, the second-harmonic mixer modules 3 and 4 with DGS filtering include Schottky diodes SD1, SD2, ground GND, dumbbell-shaped defect ground structure DGS, microstrip transmission lines 7, 8, 9, 10, 11, 12, 13, 15, 19, open-circuit microstrip stub lines 14, 16, 18, and short-circuit microstrip stub line 17. Among them, the left end of the microstrip transmission line 7 is used as the radio frequency input end of the unit mixer, the right end of the microstrip transmission line 19 is used as the local oscillator input end of the unit mixer, and the upper end of the microstrip transmission line 13 is used as the intermediate frequency total output end of the unit mixer; one end of the microstrip transmission line 8 is connected to one end of the microstrip transmission line 9; one end of the microstrip transmission line 10 is connected to one end of the microstrip transmission line 11; one end of the microstrip transmission line 12 is connected to one end of the microstrip transmission line 15; the microstrip transmission line and the open-circuit microstrip stub lines 14, 16 are perpendicularly connected to the microstrip transmission line 15; the short-circuit microstrip stub line 17 and the open-circuit microstrip stub line 18 are perpendicularly connected to the microstrip transmission line 19.

[0031] As a preferred embodiment, the microstrip transmission line 7 is parallelly connected to the microstrip transmission line 8, and the microstrip transmission line 11 is parallelly connected to the microstrip transmission line 12, and they have the same length and width. The line length is L1 = 2.50 mm, and the line width is W1 = 0.28 mm; the microstrip transmission line 9 is parallelly connected to the microstrip transmission line 10, and they have the same length and width. The line length is L2 = 2.50 mm, and the line width is W2 = 0.74 mm.

[0032] As Figure 3As shown, the length of the microstrip transmission line 15 is L5 = 5.06 mm, and the width is W5 = 0.74 mm; the length of the open microstrip stub line 14 is L6 = 2.09 mm, and the width is W6 = 0.15 mm; the length of the open microstrip stub line 16 is L7 = 5.57 mm, and the width is W7 = 0.30 mm; the length of the microstrip transmission line 19 is L8 = 1.00 mm, and the width is W8 = 0.74 mm; the length of the short - circuited microstrip stub line 17 is L9 = 5.40 mm, and the width is W9 = 0.33 mm; the length of the open microstrip stub line 18 is L10 = 6.30 mm, and the width is W7 = 0.16 mm.

[0033] As an alternative embodiment, the mixer uses a dielectric substrate of Rogers5880 with a thickness of 0.254 mm and a dielectric constant of 2.2.

[0034] As an alternative embodiment, the diodes of the second - harmonic mixing modules 3 and 4 with DGS filtering adopt GaAs - process transistors, and the diodes of the DMK2308 model produced by Alpha Company are selected. The cut - off frequency of this diode is 796.2 GHz, which is much higher than the operating frequency of the mixer.

[0035] As an alternative embodiment, the DGS structures of the second - harmonic mixing modules 3 and 4 with DGS filtering adopt traditional dumbbell - shaped structural units, with the length of each side being L4 = 5.00 mm and the width being W4 = 3.00 mm.

[0036] In this embodiment, the second - harmonic mixing unit with DGS filtering is introduced into the image - frequency rejection mixer. The frequency of the local oscillator signal can be reduced to half of the fundamental frequency, and a local oscillator source in the low - frequency band is used to replace the local oscillator source in the high - frequency band, reducing the cost of the system. By controlling the shape and parameters of the DGS defect, the idle and harmonic frequency signals are effectively suppressed, reducing the conversion loss of the system and bringing a higher image - frequency rejection ratio. In addition, the image - frequency rejection mixer itself can also automatically identify the corresponding image frequency and is applicable to broadband systems. In the range of 19.5 - 20.7 GHz for the RF input, the conversion loss can be less than 15 dB, and the isolation between the RF and IF ports and between the local oscillator and IF ports is greater than 60 dB; and a high image - frequency rejection ratio is obtained, which is greater than 40 dB in the range of 18.7 GHz - 21.5 GHz for the input frequency.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A DGS filtered second harmonic image suppression mixer, characterized in that: The mixer comprises a radio frequency Wilkinson power division module (1), a phase shift line module (2), a DGS filtering second harmonic mixing module (3, 4), a local oscillator Wilkinson power division module (5) and an intermediate frequency lumped LC phase shift module (6).

2. According to claim 1, the two output ends of the radio frequency Wilkinson power divider module (1) are respectively connected to the input ends of the phase shift line module (2) and the second harmonic mixing module (4) of the DGS filter; the output end of the local oscillator Wilkinson power divider module (5) is connected to the input end of the second harmonic mixing module (3, 4) of the DGS filter; the input end of the intermediate frequency lumped LC phase shift module (6) is connected to the output end of the second harmonic mixing module (3, 4) of the DGS filter; the input end of the radio frequency Wilkinson power divider module (1) and the local oscillator Wilkinson power divider module (5) is the total input end, and the output end of the intermediate frequency lumped LC phase shift module (6) is the total output end.

3. The second harmonic mixing module (3, 4) of the DGS filter according to claim 1 comprises Schottky diodes (SD1, SD2), a ground (GND) dumbbell-shaped ground defect (DGS), a microstrip transmission line (7, 8, 9, 10, 11, 12, 13, 15, 19), an open-circuit microstrip branch line (14, 16, 18), and a short-circuit microstrip branch line (17). The Schottky diodes (SD1, SD2) are connected in reverse parallel and are connected to the right end of the microstrip transmission line (12) and the left end of the microstrip transmission line (19); a dumbbell-shaped ground defect (DGS) is provided at the grounding plate of the microstrip transmission line (13); the left end of the microstrip transmission line (7) serves as the radio frequency input end of the unit mixer, the right end of the microstrip transmission line (19) serves as the local oscillator input end of the unit mixer, and the upper end of the microstrip transmission line (13) serves as the center oscillator input end of the unit mixer. The invention relates to a total frequency output end; one end of a microstrip transmission line (8) is connected to one end of a microstrip transmission line (9); one end of a microstrip transmission line (10) is connected to one end of a microstrip transmission line (11); one end of a microstrip transmission line (12) is connected to one end of a microstrip transmission line (15); the microstrip transmission line and the open-circuit microstrip branch line (14, 16) are vertically connected to the microstrip transmission line (15); the short-circuit microstrip branch line (17) and the open-circuit microstrip branch line (18) are vertically connected to the microstrip transmission line (19). The microstrip transmission line (7) is parallel to the microstrip transmission line (8) and the microstrip transmission line (11) is parallel to the microstrip transmission line (12), and the length and width are equal; the microstrip transmission line (9) is parallel to the microstrip transmission line (10), and the length and width are equal.

4. The DGS filtered image frequency suppression harmonic mixer according to claim 1, characterized in that: The microstrip transmission lines (7, 8, 11, 12) have a line length of L1=2.50 mm and a line width of W1=0.28 mm; the microstrip transmission lines (9, 10) have a line length of L2=2.50 mm and a line width of W2=0.74 mm; the microstrip transmission line (13) has a line length of L3=10.00 mm and a line width of W3=0.15 mm; the dumbbell-shaped ground defect (DGS) has a line length of L4=5.00 mm and a line width of W4=3.00 mm; the microstrip transmission line (15) has a line length of L5=5.06 mm and a line width of W5=0.74 mm The open-circuit microstrip branch line (14) has a line length of L6 = 2.09 mm and a line width of W6 = 0.15 mm; the open-circuit microstrip branch line (16) has a line length of L7 = 5.57 mm and a line width of W7 = 0.30 mm; the microstrip transmission line (19) has a line length of L8 = 1.00 mm and a line width of W8 = 0.74 mm; the short-circuit microstrip branch line (17) has a line length of L9 = 5.40 mm and a line width of W9 = 0.33 mm; the open-circuit microstrip branch line (18) has a line length of L10 = 6.30 mm and a line width of W7 = 0.16 mm.

5. The DGS filtered image frequency suppression harmonic mixer according to claim 1, characterized in that: The mixer uses a Rogers 5880 dielectric substrate with a thickness of 0.254 mm and a dielectric constant of 2.

2.

6. The DGS filtered image frequency suppression harmonic mixer according to claim 1, characterized in that: The mixer uses GaAs process Schottky anti-parallel diode pair DMK2308.

7. The DGS filtered image frequency suppression harmonic mixer according to claim 1, characterized in that: The second harmonic mixing modules (3, 4) of the DGS filter adopt a dumbbell-shaped DGS low-pass filter structure.

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