Image rejection mixer

Abstract

[Problem] The purpose of the present invention is to provide an image rejection mixer with which it is possible to easily detect and correct any amplitude error and any phase shift error, and which has a high image wave suppression amount. [Solution] This orthogonal mixer comprises a first input terminal and a distributor to which a first frequency is inputted, a second input terminal to which a second frequency is inputted, a third input terminal to which a frequency that has a 90° phase difference from the second frequency is inputted, and an output terminal from which a mixed wave of the first and second frequencies is outputted, wherein the orthogonal mixer is characterized by having: a detection circuit that applies a signal composed of a prescribed combination to the second and third input terminals and detects the mixed wave outputted from the output terminal; a waveform control unit that, by using a detection voltage detected by the detection circuit, detects an amplitude error and a phase shift error in a path from the second and third input terminals to the output terminal; and a waveform generation unit that, on the basis of the amplitude and the phase control signal from the waveform control unit, controls the second frequency inputted to the second and third input terminals.

Description

Image Rejection Mixer

[0001] The present invention relates to an image rejection mixer that suppresses image waves, and relates to an image rejection mixer that detects amplitude and phase errors before operating as a mixer and controls the input waveform based on this information, thereby improving the amount of image wave suppression when operating as a mixer.

[0002] High-frequency mixers are known that mix two input waves to generate a desired mixed wave. Because multiple mixed waves are generated in this case, unwanted image waves other than the desired frequency must be suppressed using a filter or other device. However, insufficient image wave suppression can lead to a deterioration in the error rate in the field of communications and to errors in quantum computation in the field of quantum computers. Therefore, image rejection mixers (IRMs) are sometimes used, which utilize phase relationships to suppress the output of image waves.

[0003] For example, an example of the configuration of an IRM is shown in Figure 10. Two unit mixers and a first input wave f １ The second input wave f is divided into two input waves, and the power combiner combines the mixed waves generated by the two unit mixers. ２ is also a quadrature mixer in which f is input to the unit mixer with a phase difference of 90°, and when a specific phase relationship is given between the divider and the combiner, the image wave is suppressed. １ -f ２ is the desired frequency, and f １ +f ２ However, there is a problem that the suppression of the image wave decreases due to variations in the conversion loss and phase shift amount in the two unit mixers, and variations in the terminal-to-terminal transmission loss and phase shift amount in the divider and power combiner.

[0004] For example, FIG. 11 shows an explanatory diagram of the phase relationship when a phase shift error occurs. In FIG. 11, φ ｄΔ : Phase error caused by the distributor, φ ｍΔ : Phase shift error caused by unit mixer, φ ｃΔ : the phase error generated by the synthesizer, the desired frequency f１ -f ２ can be synthesized almost in phase, but the image wave f １ +f ２ Since perfect antiphase synthesis is not performed, the amount of suppression decreases. ｄΔ +φ ｍΔ +φ ｃΔ If it were possible to correct this, the amount of image wave suppression could be improved, but in actual implementation, it is difficult to detect image waves with very low output power levels and determine minute amplitude and phase errors. Therefore, research into whether it is possible to detect the amplitude and phase differences required to correct the input wave led to the present invention.

[0005] Patent Document 1 discloses an image rejection mixer that aims to achieve a high image rejection ratio over a wide frequency range, but does not detect and correct amplitude errors and phase shift errors.

[0006] Japanese Patent Publication No. 2016-5026

[0007] An object of the present invention is to provide an image rejection mixer that allows easy detection and correction of amplitude errors and phase shift errors and has a high degree of image wave suppression.

[0008] The image rejection mixer according to the present invention is a quadrature mixer comprising a first input terminal and a distributor for inputting a first frequency, a second input terminal for inputting a second frequency, a third input terminal for inputting a frequency having a phase difference of 90° from the second frequency, and an output terminal for outputting a mixed wave of the first frequency and the second frequency, and is characterized by comprising: a detection circuit that applies a predetermined combination of signals to the second and third input terminals and detects the mixed wave output from the output terminal; a waveform control unit that detects amplitude errors and phase shift errors in the paths from the second and third input terminals to the output terminal using the detection voltage detected by the detection circuit; and a waveform generation unit that controls the second frequency input to the second and third input terminals based on the amplitude and phase control signals from the waveform control unit.

[0009] The present invention is characterized by the voltage relationship between the DC or second frequency input to the second and third input terminals, and by utilizing a relatively high-power high-frequency signal other than the image wave to detect minute amplitude errors and phase shift errors. Based on the detection results, waveforms with amplitude differences and phase differences that correct the amplitude errors and phase shift errors are generated, thereby improving the amount of image wave suppression.

[0010] Therefore, in the present invention, the signals having a predetermined combination applied to the second and third input terminals to detect the amplitude error and the phase shift error are DC voltages only, and the first DC voltage of the second input terminal is V ｄｃ１ , the second DC voltage of the third input terminal is V ｄｃ２ Then, V ｄｃ１ and V ｄｃ２ The combination with {V ｉｎ , 0}, {0, V ｉｎ}, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2,-V ｉｎ / √2}(V ｉｎ is any value except 0), and the detection in the detection circuit is a combination of the first frequency or a harmonic of the first frequency output from the output terminal and the V ｄｃ１ , V ｄｃ２ For example, a mixed wave of

[0011] The present invention also provides a method for detecting an amplitude error and a phase error by applying a predetermined combination of signals to the second and third input terminals, the signals being only high frequency signals of a second frequency, and the first high frequency voltage of the second input terminal being V ｉｆ１ , the second high frequency voltage of the third input terminal is V ｉｆ２ Then, V ｉｆ１ and V ｉｆ２ The combination with {V ｉｎ , 0}, {0, V ｉｎ}, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2,-V ｉｎ / √2}(V ｉｎis any value except 0), and the detection in the detection circuit is a mixed wave of the first frequency or a harmonic of the first frequency output from the output terminal and the second frequency.

[0012] For example, if there is leakage of the first frequency before the DC voltage is applied, an offset may occur in the detection voltage, resulting in a detection error. In that case, the mixer may be an even harmonic quadrature mixer that outputs a mixed wave of an even-order harmonic of the first frequency and the second frequency and suppresses the mixed wave of the even-order harmonic. Also, an offset voltage for suppressing leakage of the first frequency may be applied to the second and third input terminals, separately from the combination of the DC voltages input to the second and third input terminals.

[0013] If an unnecessary frequency is input to the detection circuit, it may lead to a detection error. In such a case, a band-pass filter having a passband including the first frequency output from the output terminal or a harmonic of the first frequency may be provided between the output terminal and the detection circuit. Also, a band-pass filter having a passband including the mixed wave output from the output terminal may be provided between the output terminal and the detection circuit. Furthermore, the power combiner on the output terminal side that combines the outputs of the two unit mixers that make up the quadrature mixer may be an in-phase combiner.

[0014] In the image rejection mixer according to the present invention, amplitude errors and phase errors inherent in the quadrature mixer can be detected using a relatively high-power signal, and a corrected input waveform can be generated, thereby improving the amount of image wave suppression. This contributes to improving signal quality and reducing the size of the filter installed downstream of the mixer, thereby enabling the overall device to be made more compact.

[0015] 1 shows an example of the configuration of an image rejection mixer according to the present invention; 2 shows an example of detecting amplitude error and phase error using a DC voltage; 3 shows an example of detecting amplitude error and phase error using a high frequency; 4 shows IQ plane coordinates when there is an amplitude error and when there is a phase error; 5 shows an explanatory diagram of when an offset occurs in the detection voltage; 6 shows an explanatory diagram of when an offset voltage is applied to the second and third input terminals; 7 shows an example of providing a filter between the output terminal and the detection circuit; 8 shows an example of providing a filter between the output terminal and the detection circuit when detecting at a high frequency; 9 shows a comparison example between a 90-degree combiner and an in-phase combiner; 10 shows an example of the configuration of a general image rejection mixer; 11 shows an explanatory diagram of when a phase shift error occurs;

[0016] 1 shows an example of the configuration of an image rejection mixer according to the present invention. It has two unit mixers 11a and 11b and a divider 12 connected thereto. The divider 12 is connected to a first frequency f １ A first input terminal is connected to which a second frequency f ２ A second input terminal to which a second frequency f (0°) is input is connected to the unit mixer 11b, and a second frequency f ２ A third input terminal to which (90°) is input is connected to the unit mixer 11a.

[0017] In order to detect the amplitude error and the phase error, a first DC voltage V is applied to the second input terminal and a third input terminal as shown in FIG. ｄｃ１ Only the third input terminal is connected to the second DC voltage V ｄｃ２ Only V is applied in the following combination: ｄｃ１ , V ｄｃ２ = {V ｉｎ , 0}, {0, V ｉｎ}, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2,-V ｉｎ 3, only a first high frequency wave of a second frequency is applied to the second input terminal, and only a second high frequency wave of a second frequency is applied to the third input terminal, with the following combination of voltage values: V ｉｆ１ , V ｉｆ２ = {V ｉｎ , 0}, {0, Vｉｎ}, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2,-V ｉｎ / √2} where V ｉｎ is any value except 0. Each time the above combinations are applied, a mixed wave of the first frequency or its harmonics generated in the unit mixers 11 a, 11 b and the first and second DC voltages or high frequency signals is detected by the detection circuit 16 via the power combiner 14, output terminal, and filter 15. The image wave is roughly out-of-phase combined in the power combiner and has a low output power level, making it difficult to detect by the detection circuit. However, the output power level of the mixed wave of the DC voltage and high frequency voltage signals applied as described above is relatively high, making it possible to detect it, and the amplitude error and phase error between the path from the second input terminal to the output terminal and the path from the third input terminal to the output terminal can be calculated by the waveform control 17.

[0018] The operation will be explained using the IQ plane coordinates shown in Fig. 4. When there is an amplitude error and a phase shift error between the path from the second input terminal to the output terminal and the path from the third input terminal to the output terminal, the IQ plane coordinates shown in Fig. 4 are obtained. ｉｎ , 0), (0, V ｉｎ ), (V ｉｎ / √2,V ｉｎ / √2), (V ｉｎ / √2,-V ｉｎ / √2) corresponds to points A, B, C, and D, respectively. The amplitude error can be calculated from the ratio of the power obtained at points A and B, and the phase error is expressed as the amplitude error and the power difference between points C and D normalized by the power at point A. By inputting the first frequency to the first input terminal and the combination of DC voltages to the second and third terminals, a mixed wave of the first frequency and DC voltage, i.e., the power at points A, B, C, and D, is obtained from the output terminal. This mixed wave is extracted through a filter and converted into a DC voltage corresponding to the power level of the first frequency by a detection circuit, thereby calculating the amplitude error and phase error. According to the calculated amplitude error and phase error, the waveform generation unit 13 generates a waveform that imparts an amplitude difference and a phase difference to the second frequency input to the second and third input terminals, thereby correcting the amplitude error and phase error and improving the image suppression amount.

[0019] An example of calculation is shown below. <Calculation formula when DC is used> Amplitude error (amplitude ratio) of the path from the third input terminal to the output terminal relative to the amplitude of the path from the second input terminal to the output terminal: k ｑｉ Phase shift error of the path from the third input terminal to the output terminal relative to the phase shift of the path from the second input terminal to the output terminal: φ ｑｉ P ｏｕｔ_０ : First frequency output power at A P ｏｕｔ_９０ : First frequency output power P when B ｏｕｔ_４５ : First frequency output power at C P ｏｕｔ_１３５ : First frequency output power when D <Calculation formula when high frequency is used> Amplitude error (amplitude ratio) of the path from the third input terminal to the output terminal relative to the amplitude of the path from the second input terminal to the output terminal: k ｑｉ P ｏｕｔ+_０ : Mixed wave at A (f １ +f ２ ) output power P ｏｕｔ+_９０ : Mixed wave at B (f １ +f ２ ) output power P ｏｕｔ+_４５ : Mixed wave at C (f １ +f ２ ) output power Pｏｕｔ+_１３５ : Mixed wave at D (f １ +f ２ ) output power P ｏｕｔ-_０ : When A (f １ -f ２ ) output power P ｏｕｔ-_９０ : When B (f １ -f ２ ) output power P ｏｕｔ-_４５ : When C (f １ -f ２ ) output power P ｏｕｔ-_１３５ :D (f １ -f ２ ) output power Phase shift error of the path from the third input terminal to the output terminal relative to the phase shift of the path from the second input terminal to the output terminal: φ ｑｉ φ 2ｑｉｃｔ : Phase difference between the second frequency input to the third input terminal and the second input terminal P φｑｉｃｔ_ｍａｘ :φ 2ｑｉｃｔ When P is changed φｑｉｃｔ Maximum value of φ 2ｑｉｃｔ０ :P φｑｉｃｔ =P φｑｉｃｔ_ｍａｘ When φ 2ｑｉｃｔ At this time, it is possible to correct the amplitude and phase shift errors from the waveform generating unit to the second input terminal and the third input terminal. １ -ω ２ and ω １ +ω ２ ω ２ is a high frequency.> Amplitude error (amplitude ratio) of the path from the third input terminal to the output terminal relative to the amplitude of the path from the second input terminal to the output terminal: k ｑｉ Phase shift error of the path from the third input terminal to the output terminal relative to the phase shift of the path from the second input terminal to the output terminal: φ ｑｉ

[0020] For example, if the first frequency leaks before the DC voltage is applied, an offset occurs in the detected voltage, resulting in a detection error. In this case, a mixed wave of an even-order harmonic and the second frequency may be used as shown in Figure 5. Alternatively, an offset voltage may be applied to the second and third input terminals to suppress leakage of the first frequency as shown in Figure 6.

[0021] For example, as shown in Figure 7, if an unnecessary frequency is input to the detection circuit, it will lead to a detection error. When the input to the second and third input terminals is DC, a band-pass filter 15 is installed so that only the first frequency (in the case of an even harmonic quadrature mixer, only the second harmonic of the first frequency) is input to the detection circuit, and other spurious signals are suppressed. Also, when the input to the second and third input terminals is the second frequency, as shown in Figure 8, (f １ -f ２ ) is the desired wave, (f １ +f ２ ) is an image wave, f ２ When is a low frequency (f １ +f ２ ) and (f １ -f ２ ) is provided as a passband of the filter 15. ２ When is high frequency (f １ +f ２ ) alone is sufficient. Other spurious signals are suppressed. In the case of an even harmonic quadrature mixer, (2f １ -f ２ ) is the desired wave, (2f １ +f ２ ) is an image wave, 2f １ +f ２ and 2f １ -f ２ is the passband. ２ When is high frequency (2f １ +f ２ ) alone is sufficient. Other spurious signals should be suppressed.

[0022] The power combiner 14 used in the present invention preferably uses an in-phase combiner as shown in Fig. 9. This is because if the power combiner is a 90-degree combiner, the phase shift error will have frequency characteristics due to the frequency characteristics, making it difficult to correct over a wide band.

[0023] The mixer according to the present invention is excellent in suppressing image waves, and is therefore useful for improving signal quality and reducing the size of filters and the like provided downstream of the mixer.

Claims

1. An image rejection mixer comprising: a first input terminal and a distributor to which a first frequency is input; a second input terminal to which a second frequency is input; a third input terminal to which a frequency having a phase difference of 90° from the second frequency is input; and an output terminal to which a mixed wave of the first frequency and the second frequency is output, characterized in that it has: a detection circuit that applies a predetermined combination of signals to the second and third input terminals and detects the mixed wave output from the output terminal; a waveform control unit that detects amplitude errors and phase shift errors in the paths from the second and third input terminals to the output terminal using the detection voltage detected by the detection circuit; and a waveform generation unit that controls the second frequency input to the second and third input terminals based on the amplitude and phase control signals from the waveform control unit.

2. The signal consisting of a predetermined combination applied to the second and third input terminals for detecting the amplitude error and the phase shift error is only a DC voltage, and the first DC voltage of the second input terminal is V ｄｃ１ , the second DC voltage of the third input terminal is V ｄｃ２ Then, V ｄｃ１ and V ｄｃ２ The combination with {V ｉｎ , 0}, {0, V ｉｎ }, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2, -V ｉｎ / √2}(V ｉｎ is any value except 0), and the detection in the detection circuit is a combination of the first frequency or a harmonic of the first frequency output from the output terminal, and the V ｄｃ１ , V ｄｃ２ 2. The image rejection mixer according to claim 1, wherein the image rejection is performed on a mixed wave of a light having a wavelength of 100 nm and a wavelength of 100 nm.

3. The signal consisting of a predetermined combination applied to the second and third input terminals for detecting the amplitude error and the phase shift error is only a high frequency of the second frequency, and the first high frequency voltage of the second input terminal is V ｉｆ１ , the second high frequency voltage of the third input terminal is V ｉｆ２ Then, V ｉｆ１ and V ｉｆ２ The combination with {V ｉｎ , 0}, {0, V ｉｎ }, {V ｉｎ / √2,V ｉｎ / √2}, {V ｉｎ / √2, -V ｉｎ / √2}(V ｉｎ 2. The image rejection mixer according to claim 1, wherein the first frequency is a combination of the first and second frequencies (wherein the first and second frequencies are any value except 0), and detection in the detection circuit is performed on a mixed wave of the first frequency or a harmonic of the first frequency output from the output terminal and the second frequency.

4. An image rejection mixer as claimed in claim 1, characterized in that said quadrature mixer is an even harmonic quadrature mixer which outputs a mixed wave of an even harmonic of said first frequency and said second frequency and suppresses the even-order mixed wave.

5. An image rejection mixer as claimed in claim 2, further comprising an offset voltage application means for applying an offset voltage to said second and third input terminals for suppressing leakage of said first frequency separately from the combination of said DC voltages input to said second and third input terminals.

6. An image rejection mixer as claimed in claim 2, further comprising a bandpass filter between said output terminal and said detection circuit, said bandpass filter having a passband including the first frequency or a harmonic of the first frequency output from said output terminal.

7. An image rejection mixer according to claim 3, further comprising a band-pass filter, between said output terminal and said detection circuit, the band of which is the mixed wave output from said output terminal.

8. The image rejection mixer according to claim 1, wherein a power combiner on the output terminal side for combining the outputs of the two unit mixers constituting said quadrature mixer is an in-phase combiner.

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