CN103873157A - Spectrum analyzer having zero frequency inhibition function - Google Patents
Spectrum analyzer having zero frequency inhibition function Download PDFInfo
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- CN103873157A CN103873157A CN201210530318.1A CN201210530318A CN103873157A CN 103873157 A CN103873157 A CN 103873157A CN 201210530318 A CN201210530318 A CN 201210530318A CN 103873157 A CN103873157 A CN 103873157A
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Abstract
The invention relates to the field of detection, specifically to a spectrum analyzer having a zero frequency inhibition function. The spectrum analyzer has a frequency conversion device, and the frequency conversion device comprises a local oscillator signal generation circuit, a frequency mixing circuit, a phase shift circuit and an intermediate frequency amplification and filtering circuit; the frequency mixing circuit is used for performing frequency mixing on a local oscillator signal generated by the local oscillator signal generation circuit and a radio frequency signal and then outputting to an intermediate frequency output end; the phase shift circuit includes a phase shifter, a first directional coupler and a second directional coupler; and the first directional coupler enables the local oscillator signal to be coupled to the phase shifter, after the phase shifter outputs a reverse local oscillator signal, the second directional coupler enables the reverse local oscillator signal to be coupled to the intermediate frequency output end. The spectrum analyzer provided by an embodiment of the invention eliminates or reduces local oscillator leakage signals, thereby reducing leakage of the local oscillator, and improving bottom noise near zero frequency. An intermediate frequency amplifier in the subsequent intermediate frequency amplification and filtering circuit does not generate compression, and spill of an analog digital collector (ADC) located at a rear stage does not occur.
Description
Technical field
The present invention relates to measure technical field of measurement and test, be specifically related to a kind of spectrum analyzer with zero-frequency inhibit feature.
Background technology
Spectrum analyzer is a kind of receiver that is used for measured signal to carry out spectrum analysis, can measure frequency, the amplitude of unknown signaling, and the relevant parameters such as distortion, have very wide frequency measurement scope, and very low amplitude monitoring sensitivity.Be mainly used in the fields such as base station maintenance, electronic product research and development, production.Existing spectrum analyzer adopts superhet structure, input signal is passed through to repeatedly frequency conversion, become lower intermediate-freuqncy signal, then deliver to ADC sampling, the digital medium-frequency signal that sampling is obtained passes through digital IF filter, wave detector and video filter again, finally delivers to display the frequency spectrum obtaining is observed and analyzed.
As shown in Figure 1, be the annexation schematic diagram of prior art intermediate frequency spectrum analyzer down-conversion link.In prior art spectrum analyzer down-conversion link, conventionally use high potential barrier frequency mixer 101, its superior performance.But local oscillator driving power is had relatively high expectations (greatly between 15-20dBm), the isolation of frequency mixer LO-IF end is limited, conventionally be about 20dB left and right, and to obtain good distortion index, the best be conventionally less than-10dBm of incoming level of frequency mixer, therefore frequency mixer intermediate frequency port place, local oscillator leakage signal amplitude will exceed intermediate-freuqncy signal, after intermediate frequency amplifier 102 compressions via rear class, there is distortion; The ADC103 of same rear class also has a full scale voltage, in the time that local oscillator leakage signal is excessive, can overflow.
Meanwhile, when local oscillator frequency sweep is when minimum, frequency is identical with intermediate-freuqncy signal or approaching, within local oscillator leakage signals falls into intermediate-frequency bandwidth, is shown on display screen, the zero frequency signal of Here it is spectrum analyzer.In the time that zero frequency signal amplitude is larger, its sideband noise is also higher, causes near the end of low-frequency range (zero-frequency) to be made an uproar and is elevated.
Summary of the invention
The embodiment of the present invention provides, be used for solving prior art in the time that zero frequency signal amplitude is larger, its sideband noise is also higher, causing near the end of low-frequency range (zero-frequency) to be made an uproar is elevated, the local oscillator leakage signal amplitude that is simultaneously leaked to medium frequency output end will exceed intermediate-freuqncy signal, after intermediate frequency amplifier compression via rear class, there is distortion; The ADC of same rear class can produce and overflow.
The spectrum analyzer that the embodiment of the present invention provides has converter plant; Described converter plant comprises: local oscillation signal produces circuit, mixting circuit, phase-shift circuit and intermediate frequency filtering and amplifying circuit;
Described mixting circuit comprises frequency mixer, for described local oscillation signal is produced after the local oscillation signal and radiofrequency signal mixing of circuit generation, exports medium frequency output end to;
Described phase-shift circuit comprises: phase shifter, the first directional coupler and the second directional coupler; Described local oscillation signal is coupled to phase shifter by described the first directional coupler, exported after reverse local oscillation signal by described phase shifter, and described reverse local oscillation signal is coupled to described medium frequency output end by described the second directional coupler;
The input of described intermediate frequency filtering and amplifying circuit connects described medium frequency output end.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, described phase-shift circuit also comprises: control unit, for regulate the phase place of described reverse local oscillation signal by preset signal.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, by detecting the amplitude of output local oscillator leakage signal of described intermediate frequency filtering and amplifying circuit, obtains described preset signal.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, described phase-shift circuit also comprises: amplifier, the insertion loss producing for compensating the degree of coupling of described the first directional coupler and described the second directional coupler.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, described amplifier is determined gain according to formula: G=C1+C2-C3, wherein, G is the gain of described amplifier, and C1, C2 are respectively the degree of coupling of described the first coupler and described the second coupler, the isolation that C3 is described frequency mixer.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, described spectrum analyzer comprises multistage described converter plant.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, described converter plant is arranged on the printed circuit board (PCB) with shielding cavity.
The above-mentioned spectrum analyzer with zero-frequency inhibit feature, wherein, on described printed circuit board (PCB), also there is isolation channel, described isolation channel is between described the first directional coupler and described frequency mixer, phase shifter, amplifier, and between described the second directional coupler and described phase shifter, amplifier.
A kind of spectrum analyzer with zero-frequency inhibit feature that the embodiment of the present invention provides, will eliminate or reduce local oscillator leakage signal by increase phase-shift circuit in converter plant, thereby reduces local oscillator leakage, has improved near the end of zero-frequency and has made an uproar.Make the intermediate frequency amplifier in follow-up intermediate frequency filtering and amplifying circuit can not produce compression, the analog digital collector (ADC) that is positioned at rear class also can not overflow.
Brief description of the drawings
Accompanying drawing described herein is used to provide a further understanding of the present invention, forms the application's a part, does not form limitation of the invention.In the accompanying drawings:
Fig. 1 is the spectrum analyzer down-conversion link schematic diagram of prior art;
Fig. 2 is the converter plant link schematic diagram in the embodiment of the present invention;
Fig. 3 is another converter plant link schematic diagram in the embodiment of the present invention;
Fig. 4 is the printed circuit board layout schematic diagram of the converter plant in the embodiment of the present invention.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the embodiment of the present invention is described in further detail.At this, schematic description and description of the present invention is used for explaining the present invention, but not as a limitation of the invention.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, as shown in Figure 2, has converter plant 20 in described spectrum analyzer; Described converter plant 20 comprises: local oscillation signal produces circuit 201, mixting circuit 202, phase-shift circuit 203 and intermediate frequency filtering and amplifying circuit 204;
Described mixting circuit 202 comprises frequency mixer 2021, for received RF signal and local oscillation signal, and by after described local oscillation signal and radiofrequency signal mixing, exports medium frequency output end 205 to.
In embodiment, the input of described intermediate frequency filtering and amplifying circuit 204 connects described medium frequency output end 205; Be that described medium frequency output end 205 is positioned in the intermediate-frequency channel that mixting circuit 202 and intermediate frequency filtering and amplifying circuit 204 form; Concrete, described medium frequency output end 205 is between the output of described mixting circuit 202 and the input of intermediate frequency filtering and amplifying circuit 204; The main component of the signal of now, being exported by mixting circuit 202 comprises: intermediate-freuqncy signal and local oscillator leakage signal;
Described phase-shift circuit 203 comprises: phase shifter 2031, the first directional coupler 2032 and the second directional coupler 2033; Described local oscillation signal is coupled to phase shifter 2031 by described the first directional coupler 2032, exported after reverse local oscillation signal by described phase shifter 2031, and described reverse local oscillation signal is coupled to described medium frequency output end 205 by described the second directional coupler 2033.Preferably, the local oscillation signal that local oscillation signal generation unit 201 produces is delivering to before mixting circuit 202, the first directional coupler 2032 is first coupled out local oscillation signal one tunnel and delivers in phase-shift circuit 203, this local oscillation signal is after phase-shift circuit 203 phase shifts, the phase place of local oscillation signal will be offset, generate identical with local oscillation signal frequency, the reverse local oscillation signal that phase phasic difference is 180 °, and then be coupled to the medium frequency output end 205 of mixting circuit 202 by the second directional coupler 2033, to export the reverse local oscillation signal of medium frequency output end 205 to identical with the local oscillator leakage signal frequency that mixting circuit 202 exports medium frequency output end 205 to for phase shifter 2031 like this, 180 ° of phase phasic differences, can cancel out each other to a great extent.
In above-described embodiment, the earth terminal of described two couplers is connected with respectively matched load.
Will eliminate or reduce local oscillator leakage signal by increase phase-shift circuit in above-described embodiment in the converter plant of spectrum analyzer, thereby reduce local oscillator leakage, improve near the end of zero-frequency and made an uproar.Make the intermediate frequency amplifier in follow-up intermediate frequency filtering and amplifying circuit can not produce compression, the analog digital collector (ADC) that is positioned at rear class also can not overflow.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, and preferably, described phase-shift circuit 303 also comprises: control unit 3034, and for regulate the phase place of described reverse local oscillation signal by preset signal.
Concrete, as shown in Figure 3, due to the incoming frequency difference of phase-shift circuit 303 own, therefore the phase deviation of its output also has difference, by control unit 3034, it is carried out the anti-phase local oscillation signal of exporting the modulation of phase deviation at this, while making the first local oscillator frequency sweep, the upper phase shift of phase shifter 3031 respective frequencies points is 180 ° or approaches 180 °, so reaches best neutralization effect.Preferably, the prefabricated value of control unit can be calibrated in advance.
Preferably, described control unit is specifically as follows a digital simulation controller (DAC).
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, preferably, by detecting the amplitude of output local oscillator leakage signal of described intermediate frequency filtering and amplifying circuit, obtains described preset signal.
Concrete, first make in mixting circuit not incoming radio frequency signal, measure the power of local oscillator leakage signal at some place of the output of intermediate frequency filtering and amplifying circuit, judge the phase shift situation of phase shifter.Regulation unit obtains the value of a prefabricated signal subsequently, and this prefabricated signal makes the local oscillator leakage signal minimum under this frequency, because local oscillator leakage signal amplitude preset signal hour is best.The value record of this prefabricated signal is got off, as the prefabricated signal under this frequency.Then change local frequency, from low to high, whole frequency range is all tested, and write down the value of the corresponding prefabricated signal of all frequencies.In the time that spectrum analyzer is worked, call this prefabricated signal according to local frequency at that time.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, preferably, as shown in Figure 3, described phase-shift circuit 303 also comprises: amplifier 3035, the insertion loss producing for compensating described the first directional coupler 3032 and the degree of coupling of described the second directional coupler 3033.Concrete, when the first directional coupler 3032 and the second directional coupler 3033 are coupled to signal, all can be because the reason of the degree of coupling produces insertion loss, therefore need to couple a signal to before medium frequency output end at the second directional coupler 3032, reverse local oscillation signal is amplified, and the gain of amplifier 3035 is decided by the size of the differential loss that is coupled.After finally making reverse local oscillation signal be amplified by amplifier 3035, the signal amplitude that arrives medium frequency output end through the second directional coupler 3033 approximate greatly local oscillation signal through mixting circuit 302 amplitude in the local oscillator leakage signals of medium frequency output end, now both can reach counteracting substantially.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, preferably, described amplifier is determined gain according to formula: G=C1+C2-C3, wherein, G is the gain of described amplifier, C1, C2 are respectively the degree of coupling of described the first coupler and described the second coupler, the isolation that C3 is described frequency mixer.At this, the isolation of frequency mixer refers to the mutual isolation between each frequency ports, comprises local oscillator and radio frequency, local oscillator and intermediate frequency, and isolation between radio frequency and intermediate frequency.Preferably, the setting of this amplifier magnification ratio makes as do not reached in situation that two paths of signals offsets completely, at least should be lower than the compression point of intermediate frequency amplifier, and ensure that the ADC of rear class can not overflow and be as the criterion.Can farthest offset like this local oscillator leakage signal.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, and preferably, described spectrum analyzer comprises multistage described converter plant.Concrete, be added or subtract each other because mixting circuit mixing exists radiofrequency signal (RF) and local oscillation signal (LO), and producing image frequency, image frequency may produce spurious signal with the harmonic wave of local oscillator or local oscillator, and fall in analysis bandwidth, finally on display screen, be shown as spuious.Therefore in order to suppress image frequency, conventionally need to adopt multistage frequency conversion, repeatedly filtering, by image frequency filtering.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, and preferably, described converter plant is arranged on the printed circuit board (PCB) with shielding cavity.Preferably, each circuit in described converter plant is arranged at respectively in multiple shielding cavities.Concrete, if shielding isolation is not, local oscillation signal can be directly coupled to medium frequency output end by phase-shift circuit, does not so not only have negative function, can make the signal of leakage larger.As shown in Figure 4, it can arrange separately respectively in different shielding cavity 401 from the combinational circuit 407 of amplifier at described frequency mixer 402, the first coupler 403, the second coupler 404, intermediate frequency amplifier 405, control unit 406 and phase shifter.Therefore adopt converter plant shielding cavity is isolated, prevent that local oscillation signal from crossing mixting circuit or phase-shift circuit, direct-coupling or be radiated input or the output of intermediate frequency amplifier.
The embodiment of the present invention provides a kind of spectrum analyzer with zero-frequency inhibit feature, preferably, as shown in Figure 4, on described printed circuit board (PCB), also there is isolation channel 408, described isolation channel 408 is between described the first directional coupler 403 and described frequency mixer 402, phase shifter 407, amplifier 409, and between described the second directional coupler 404 and described phase shifter 407, amplifier 409.In local oscillation signal and the approaching region of intermediate-frequency channel location comparison, also adopt the mode of opening isolation channel on pcb board, further prevent physically local oscillation signal from coupling between pcb board or be radiated intermediate-frequency channel.In a word, by the pcb board fluting isolation of Fig. 4, can make signal propagate according to the route of design, improve the validity of phase-shift circuit.
Above-described embodiment; object of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the foregoing is only the specific embodiment of the present invention; the protection range being not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (8)
1. a spectrum analyzer with zero-frequency inhibit feature, is characterized in that, in described spectrum analyzer, has converter plant; Described converter plant comprises: local oscillation signal produces circuit, mixting circuit, phase-shift circuit and intermediate frequency filtering and amplifying circuit;
Described mixting circuit comprises frequency mixer, for described local oscillation signal is produced after the local oscillation signal and radiofrequency signal mixing of circuit generation, exports medium frequency output end to;
Described phase-shift circuit comprises: phase shifter, the first directional coupler and the second directional coupler; Described local oscillation signal is coupled to phase shifter by described the first directional coupler, exported after reverse local oscillation signal by described phase shifter, and described reverse local oscillation signal is coupled to described medium frequency output end by described the second directional coupler;
The input of described intermediate frequency filtering and amplifying circuit connects described medium frequency output end.
2. the spectrum analyzer with zero-frequency inhibit feature according to claim 1, is characterized in that, described phase-shift circuit also comprises: control unit, and for regulate the phase place of described reverse local oscillation signal by preset signal.
3. the spectrum analyzer with zero-frequency inhibit feature according to claim 2, is characterized in that, by detecting the amplitude of output local oscillator leakage signal of described intermediate frequency filtering and amplifying circuit, obtains described preset signal.
4. the spectrum analyzer with zero-frequency inhibit feature according to claim 1, it is characterized in that, described phase-shift circuit also comprises: amplifier, the insertion loss producing for compensating the degree of coupling of described the first directional coupler and described the second directional coupler.
5. the spectrum analyzer with zero-frequency inhibit feature according to claim 4, it is characterized in that, described amplifier is determined gain according to formula: G=C1+C2-C3, wherein, G is the gain of described amplifier, C1, C2 are respectively the degree of coupling of described the first coupler and described the second coupler, the isolation that C3 is described frequency mixer.
6. the spectrum analyzer with zero-frequency inhibit feature according to claim 1, is characterized in that, described spectrum analyzer comprises multistage described converter plant.
7. the spectrum analyzer with zero-frequency inhibit feature according to claim 1, is characterized in that, described converter plant is arranged on the printed circuit board (PCB) with shielding cavity.
8. the spectrum analyzer with zero-frequency inhibit feature according to claim 7, it is characterized in that, on described printed circuit board (PCB), also there is isolation channel, described isolation channel is between described the first directional coupler and described frequency mixer, phase shifter, amplifier, and between described the second directional coupler and described phase shifter, amplifier.
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Cited By (11)
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| CN104300996A (en) * | 2014-10-23 | 2015-01-21 | 中国电子科技集团公司第四十一研究所 | Active residual response suppression method based on hardware circuit |
| CN105242090A (en) * | 2015-10-27 | 2016-01-13 | 中国电子科技集团公司第四十一研究所 | Zero frequency suppression circuit and method for super-heterodyne signal receiving and analyzing instrument |
| CN105319441A (en) * | 2014-07-08 | 2016-02-10 | 苏州普源精电科技有限公司 | Spectrum analyzer having zero frequency suppression function |
| CN106301625A (en) * | 2016-08-26 | 2017-01-04 | 北京信维科技股份有限公司 | A kind of antenna feeder test and arrangements for analyzing frequency |
| WO2017008302A1 (en) * | 2015-07-16 | 2017-01-19 | 华为技术有限公司 | Method for suppressing frequency-mixing spurious emissions, and receiver |
| CN106385270A (en) * | 2016-08-31 | 2017-02-08 | 成都九洲迪飞科技有限责任公司 | Self-calibrating device and method for reducing local oscillation leakage of broadband frequency mixer |
| CN109557370A (en) * | 2019-01-22 | 2019-04-02 | 上海创远仪器技术股份有限公司 | Realize the spectrum analyzer circuit structure without zero-frequency function |
| CN110649930A (en) * | 2019-10-09 | 2020-01-03 | 河南理工大学 | Method and system for inhibiting local oscillator leakage in large-scale antenna |
| CN113258947A (en) * | 2021-07-15 | 2021-08-13 | 成都玖锦科技有限公司 | Device and method for reducing false signal amplitude of receiver |
| CN115173871A (en) * | 2022-07-04 | 2022-10-11 | 合肥浩星科技有限公司 | Carrier suppression circuit and suppression method for spectrum shifting circuit |
| CN115833859A (en) * | 2023-02-20 | 2023-03-21 | 深圳市鼎阳科技股份有限公司 | Differential mixing circuit, spectrum analyzer, differential mixing method and medium |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105319441A (en) * | 2014-07-08 | 2016-02-10 | 苏州普源精电科技有限公司 | Spectrum analyzer having zero frequency suppression function |
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| CN106385270A (en) * | 2016-08-31 | 2017-02-08 | 成都九洲迪飞科技有限责任公司 | Self-calibrating device and method for reducing local oscillation leakage of broadband frequency mixer |
| CN109557370A (en) * | 2019-01-22 | 2019-04-02 | 上海创远仪器技术股份有限公司 | Realize the spectrum analyzer circuit structure without zero-frequency function |
| CN110649930A (en) * | 2019-10-09 | 2020-01-03 | 河南理工大学 | Method and system for inhibiting local oscillator leakage in large-scale antenna |
| CN113258947A (en) * | 2021-07-15 | 2021-08-13 | 成都玖锦科技有限公司 | Device and method for reducing false signal amplitude of receiver |
| CN115173871A (en) * | 2022-07-04 | 2022-10-11 | 合肥浩星科技有限公司 | Carrier suppression circuit and suppression method for spectrum shifting circuit |
| CN115833859A (en) * | 2023-02-20 | 2023-03-21 | 深圳市鼎阳科技股份有限公司 | Differential mixing circuit, spectrum analyzer, differential mixing method and medium |
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