Quadrature mixer with excellent image wave suppression

Abstract

An object of the present invention is to provide a quadrature mixer that can suppress the generation of image waves. [Solution] A quadrature mixer consisting of first and second unit mixers that uses the mth order (m is a natural number) of an LO wave as a carrier wave, has an LO distribution section that equally distributes the LO wave and gives it a phase difference of π / 2m and outputs it to the LO terminals of the first and second unit mixers, has a power combiner that combines the output wave from the first unit mixer and the output wave from the second unit mixer, and is characterized by having LO harmonic suppression sections with the same characteristics that suppress higher-order harmonics of the LO wave, located symmetrically at the same electrical length from the output terminals of the LO distribution section between the output terminal of the LO distribution section and the input terminal of the power combiner.

Description

[Technical Field]

[0001] The present invention relates to a high-frequency mixer, and more particularly to a quadrature mixer capable of suppressing the output of unwanted waves (image waves) other than the desired wave. [Background technology]

[0002] For example, as shown in Figure 5, a first input wave (f2) having a phase difference of 90° from each other is input to two unit mixers, and in an orthogonal mixer that inputs a second input wave (f1) with a phase difference of 90° at a divider, only the desired frequency (f1-f2) is output by a power combiner, and the output of the image wave, which is an unwanted wave (f1+f2), can be suppressed. However, as shown in Fig. 4, when reflected waves or leaky waves occur, interference occurs in the first and second unit mixers, and the amplitude and phase difference relationship of the LO waves after interference that are input to the first and second unit mixers deviates from the original equal amplitude and 90°, resulting in a technical issue in which the out-of-phase synthesis of the image waves in the in-phase power combiner becomes incomplete.

[0003] If such interference results in insufficient suppression of image waves, it may lead to communication errors in the field of communications technology, or to errors in quantum operations in the field of quantum computers.

[0004] An image rejection mixer (IRM) that uses such a phase relationship to suppress the output of an image wave has been reported, for example, in Patent Document 1. However, the technology disclosed in this publication is not intended to suppress image waves caused by interference due to reflected waves or leaky waves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2016-005026 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a quadrature mixer that can suppress the generation of image waves. [Means for solving the problem]

[0007] The quadrature mixer of the present invention is a quadrature mixer consisting of first and second unit mixers that use the mth order (m is a natural number) of an LO wave as a carrier wave, and is characterized in that it has an LO distribution section that equally distributes the LO wave and gives a phase difference of π / 2m (for example, 90° when m=1, and 45° when m=2) and outputs the LO wave to the LO terminals of the first and second unit mixers, a power combiner that combines the output waves from the first and second unit mixers, and has LO harmonic suppression sections with the same characteristics that suppress higher-order harmonics of the LO wave, located symmetrically at the same electrical length from the output terminals of the LO distribution section, between the output terminals of the LO distribution section and the input terminals of the power combiner.

[0008] This suppresses interference of the higher harmonics of the LO wave in the first unit mixer and the second unit mixer, and suppresses the generation of image waves generated by mixing of these higher harmonics of the LO wave with the LO wave before interference or higher mixing products, thereby improving image wave suppression. Furthermore, there is no need to provide a large circuit that suppresses the LO to n-th order LO over a wide band, which contributes to miniaturization of the circuit.

[0009] In the present invention, the quadrature mixer is comprised of first and second unit mixers that use the mth order (m is a natural number) of an LO wave as a carrier wave, and has an LO distribution section that equally distributes the LO wave and gives a phase difference of π / 2m (for example, 90° when m=1, and 45° when m=2) and outputs the result to the LO terminals of the first and second unit mixers, and has a power combiner that combines the output wave from the first unit mixer and the output wave from the second unit mixer, and may have LO harmonic suppression sections with the same characteristics that suppress higher-order harmonics of the LO wave between the LO distribution section and the LO terminals of the first and second unit mixers, or may have LO harmonic suppression sections with the same characteristics that suppress higher-order harmonics of the LO wave between the output terminals of the first and second unit mixers and the input terminal of the power combiner.

[0010] As a result, whether an LO harmonic suppression unit is provided in the LO system (between the LO terminals of the first and second unit mixers via the LO distribution unit) or in the RF system through which the output waves from the first and second unit mixers propagate (between the output terminals of the first and second unit mixers via the power combiner), the generation of image waves due to mixing with high-order LOs and high-order mixing products can be suppressed by suppressing interfering high-order LO waves. The LO harmonic suppression unit may be configured, for example, as a shunt LCR series resonant circuit that shorts out only the third harmonic of the LO, or as a series LCG parallel resonant circuit that opens only the third harmonic. In a differential circuit, the difference in the amount of attenuation between the differential mode and the common mode may be utilized to suppress high-order LO waves. [Effects of the Invention]

[0011] The quadrature mixer according to the present invention can suppress interference in the unit mixers due to reflected waves and leaky waves. More specifically, by suppressing the propagation of high-order LO waves between two unit mixers, the interfering LO waves generated by mixing the high-order LO wave in one unit mixer with the LO wave or high-order LO wave in the other unit mixer are suppressed, thereby improving the suppression of image waves. Furthermore, the filter installed downstream of the mixer can be made smaller, and the device can be made smaller. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows an example of the configuration of a quadrature mixer according to a first embodiment. [Figure 2] 2 is a diagram illustrating the operation of the quadrature mixer shown in FIG. [Figure 3] 10 shows an example of the configuration of a quadrature mixer according to a second embodiment. [Figure 4] 10A and 10B are diagrams illustrating interference with reflected waves or leaky waves in the first and second unit mixers. [Figure 5] 1 shows an explanatory diagram of image wave suppression in a quadrature mixer. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 shows a configuration example of a quadrature mixer as a first embodiment, which suppresses high-order LO waves interfering through an LO system and suppresses image waves. FIG. 2 shows an explanatory diagram of the operation. It has first and second unit mixers 11 and 12 and an LO distribution unit 21 that distributes the LO wave equally. A first LO harmonic suppression section 31 is arranged between the LO terminal provided in the first unit mixer 11 and the LO distribution section 21, and a second LO harmonic suppression section 32 is arranged between the LO terminal provided in the second unit mixer 12 and the LO distribution section 21. The LO wave having frequency f1 is equally divided by the LO distribution unit 21 and given a phase difference of 90°, and is input to the LO terminal of the first unit mixer 11 via the first LO harmonic suppression unit 31 and to the LO terminal of the second unit mixer 12 via the second LO harmonic suppression unit 32. Here, the first LO harmonic suppression unit 31 and the second LO harmonic suppression unit 32 have the same characteristics, are arranged in symmetrical positions with the same electrical length from the output terminal of the LO distribution unit 21 with the same layout, and therefore the amplitude difference and phase difference of the LO wave caused by the LO distribution unit 21 are maintained when input to the LO terminals of the first and second unit mixers 11 and 12. With respect to the high frequency f2 (IF signal) input to the first unit mixer 11, the high frequency f2 (IF signal) having a phase difference of 90° is input to the second unit mixer 12. As a result, the second unit mixer 12 outputs a desired wave (LO-IF) that is in phase with the output wave from the first unit mixer 11 and an image wave (LO+IF) that is out of phase with the output wave from the first unit mixer 11. By combining these signals by an in-phase power combiner, the desired wave is output from the quadrature mixer because it is an in-phase combination, and the image wave is suppressed because it is an out-of-phase combination. However, as shown in FIG. 2, higher harmonics of the LO wave (higher LO wave) generated in the second unit mixer 12 propagate from the LO terminal to the first unit mixer 11 via the LO system. If this propagation amount is large, the high-order LO wave (e.g., 2LO) from the second unit mixer 12 mixes with the LO wave input to the first unit mixer 11, the high-order LO wave generated in the first unit mixer 11, and a high-order mixing product (e.g., 3LO+IF), generating a large image wave (LO+IF). In this case, in the quadrature mixer according to the present invention, the LO harmonic suppression section attenuates the propagation of high-order LO waves from the second unit mixer 12 to the first unit mixer, and interference in the first unit mixer 11 is suppressed, thereby suppressing the generation of the image wave. This action also applies to the second unit mixer 12.

[0014] FIG. 3 shows a second embodiment in which a high-order LO wave interfering via an RF system is suppressed. In the second embodiment, a first LO harmonic suppression unit 31 is arranged between the output terminal of the first unit mixer 11 and the input terminal of the power combiner 41, and a second LO harmonic suppression unit 32 is arranged between the output terminal of the second unit mixer 12 and the input terminal of the power combiner 41. Here, the first LO harmonic suppression section 31 and the second LO harmonic suppression section 32 have the same characteristics, and are arranged with the same layout at symmetrical positions that are the same electrical length away from the output terminals of the first and second unit mixers 11 and 12 (at symmetrical positions that are the same electrical length away from the output terminal of the LO distribution section 21), so the amplitude and phase differences between the original desired wave and image wave output from the first and second unit mixers 11, 12 are maintained when they are input to the power combiner 41. This makes it possible to suppress image waves generated when higher-order LOs leaking from other unit mixers via the RF system or higher-order LOs reflected back by the power combiner mix with the original LO wave or higher-order mixing products.

[0015] In the present invention, the LO harmonic suppressor can use, for example, a shunt LCR series resonant circuit that shorts only the third harmonic of the LO, or a series LCG parallel resonant circuit that opens only the third harmonic. In a differential circuit, the difference in the amount of attenuation between the differential mode and the common mode may be used to suppress high-order LO waves.

[0016] The embodiments may be combined in any manner.

[0017] In addition, in the above embodiment, the case where m=1 has been described, but the same applies when m=2, 3, 4, . . . If m=2, the LO distribution unit 21 distributes the signals equally and gives a phase difference of 45°, so that the desired wave becomes 2LO-IF and the image wave becomes 2LO+IF. At this time, if a high-order LO wave (for example, 3LO) leaking from the other unit mixer is large, it mixes with the high-order mixing product (for example, LO-IF) to generate a large image wave (2LO+IF). This can also be said to be the case where the leaking 3LO mixes with the original LO wave to generate 2LO, which is different from the second harmonic of the original LO wave, and then mixes with the IF to generate an image wave (2LO+IF). In this case, in the quadrature mixer according to the present invention, the LO harmonic suppression section attenuates the propagation of high-order LO waves between unit mixers, suppressing interference and thereby suppressing the generation of the image waves.

Claims

1. a quadrature mixer including first and second unit mixers using an m-th order (m is a natural number) of an LO wave as a carrier wave, an LO distribution unit that equally distributes an LO wave and outputs it to the LO terminals of the first and second unit mixers with a phase difference of π / 2m; a power combiner for combining an output wave from the first unit mixer and an output wave from the second unit mixer; A quadrature mixer characterized in that LO harmonic suppression units with the same characteristics that suppress higher-order harmonics of the LO wave are provided at symmetrical positions, each at the same electrical length from the output terminal of the LO distribution unit, between the output terminal of the LO distribution unit and the input terminal of the power combiner.

2. 2. The quadrature mixer according to claim 1, further comprising: an LO harmonic suppression unit having the same characteristics for suppressing higher harmonics of an LO wave between the LO distribution unit and the LO terminals of the first and second unit mixers.

3. 2. The quadrature mixer according to claim 1, further comprising: an LO harmonic suppression unit having the same characteristics for suppressing higher harmonics of an LO wave between output terminals of the first and second unit mixers and an input terminal of the power combiner.

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