CN108964612B - Low-noise distributed amplitude modulation circuit and modulation method, and microwave signal generator - Google Patents
Low-noise distributed amplitude modulation circuit and modulation method, and microwave signal generator Download PDFInfo
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- CN108964612B CN108964612B CN201810663286.XA CN201810663286A CN108964612B CN 108964612 B CN108964612 B CN 108964612B CN 201810663286 A CN201810663286 A CN 201810663286A CN 108964612 B CN108964612 B CN 108964612B
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Abstract
The invention provides a distributed amplitude modulation circuit, and belongs to the technical field of microwave signal generators. The distributed amplitude modulation circuit is used for a microwave signal generator and comprises a plurality of cascaded amplitude modulation units, each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of the microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit. By adopting the distributed amplitude modulation circuit, under the condition that a signal source outputs low power, a proper amount of attenuation can be carried out on the signal by the multi-level distributed amplitude modulator, and a higher signal-to-noise ratio can be realized; the rise of the noise bottom and the deterioration of the phase noise are avoided, thereby improving the signal quality. The invention also discloses a low-noise distributed amplitude modulation method and a microwave signal generator.
Description
Technical Field
The invention relates to the field of signal generators, in particular to a low-noise distributed amplitude modulation circuit, a modulation method and a microwave signal generator.
Background
The universal microwave signal generator is one of commonly used microwave measuring instruments, and can output signals with specified frequency, specified power and specified modulation types according to test requirements, and is used for simulating various test scenes; under the condition of not using an external fixed attenuation unit, the dynamic range of the output power of the microwave signal generator can reach 50dB or even higher, so that great challenge is brought to the signal quality, when the output power of the microwave signal generator changes, the bottom of signal noise also changes, specifically, when the microwave signal generator outputs low power, the bottom of the output signal noise is raised, the phase noise is also deteriorated, the dynamic range is larger, the noise bottom is higher, the phase noise deterioration is more serious, and the problem seriously influences various noise indexes of the output signal of the microwave signal generator.
Fig. 1 shows a typical circuit of a microwave signal generator, which employs an Automatic Level Control (ALC) technique, which mainly functions to precisely control the output power of a signal, and an amplitude modulation technique, which mainly functions to modulate amplitude information onto a carrier wave for transmission. Because the amplitude control circuit in the ALC circuit and the amplitude modulation circuit in the signal generator both regulate the amplitude of the signal, in order to simplify the scheme of the microwave signal generator, the amplitude control circuit and the amplitude modulation circuit in the ALC loop usually share the same circuit, namely the amplitude modulation circuit shown in fig. 1, and the rear end of the amplitude modulation circuit is a multi-stage cascade amplifier and is used for amplifying the microwave signal. The output signal of the signal generator is coupled with a path of signal through the directional coupler to detect to obtain detection voltage corresponding to power, the detection voltage is amplified and then compared with reference voltage corresponding to preset power, the comparator outputs the amplified voltage difference, the attenuation of the amplitude modulator is adjusted after the voltage difference is converted through the driver, the output power of the microwave signal generator is changed, and the loop repeats the above dynamic adjustment state until the detection voltage is equal to the reference voltage, namely the signal output power is stable when reaching the preset power.
At present, the existing microwave signal generator adopts a single-stage amplitude modulation circuit, i.e. an amplitude modulation circuit shown in a dashed line frame in fig. 1, the amplitude modulator is a single-stage modulator, the dynamic range of the output power of the signal generator is the maximum attenuation of the amplitude modulator, and the rear end of the amplitude modulator is a multi-stage cascade amplifier for amplifying and outputting the microwave signal power.
In the state of the minimum output power of the microwave signal generator, the amplitude modulator (amplitude controller) reaches the maximum attenuation, for example, the dynamic range of the signal generator is 50dB or even higher, the attenuation of the amplitude modulation circuit can reach 50dB or even higher, theoretically, the bottom of the signal noise is-174 dBm/Hz, under the condition of low-power signal output, the signal attenuation is 50dB or even higher, but the bottom of the noise already reaches the limit theoretical value, the signal-to-noise ratio is seriously deteriorated, after the signal is amplified by a rear-end amplifier, the bottom of the noise is raised along with the signal amplification, the phase noise is deteriorated, and the signal quality is reduced.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a low-noise distributed amplitude modulation circuit, a modulation method and a microwave signal generator.
The technical scheme of the invention is realized as follows:
a distributed amplitude modulation circuit is used for a microwave signal generator and comprises a plurality of cascaded amplitude modulation units, each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of the microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit.
Optionally, the setting of each level of amplitude modulation unit satisfies the following condition:
NGin+Gn-ATTn>NG+K
wherein NG is the lowest noise bottom of the whole signal link; NGin is the noise bottom corresponding to the input signal power of Pin; G1-Gn is the amplifier gain of each level of amplitude modulation unit; ATT1-ATTn are attenuation of amplitude modulators at each stage; k is a margin value.
Optionally, K is 5-10 dB.
Optionally, the distributed amplitude modulation circuit setting satisfies the following condition:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
wherein G is the total gain required by the signal path, ATT is the total attenuation required by the signal path,
G＝Pmax-Pin
ATT＝Pd
wherein, Pd is the dynamic range of the output power of the signal generator, and Pmax is the maximum output power of the signal generator.
The invention also proposes a microwave signal generator comprising a distributed amplitude modulation circuit as described above.
The invention also provides a distributed amplitude modulation method, the attenuation is distributed through a plurality of cascaded amplitude modulation units, each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of the microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit.
Optionally, the distributed amplitude modulation method includes:
determining a whole signal link lowest noise bottom NG;
determining input signal power Pin and corresponding noise bottom NGin;
determining the total gain G and the total attenuation ATT required by the signal path according to the dynamic range Pd and the maximum power Pmax of the output power of the signal generator, wherein,
G＝Pmax-Pin
ATT＝Pd
setting the amplifier gain of each level of amplitude modulation unit as G1-Gn, setting the attenuation of each level of amplitude modulator as ATT1-ATTn, and setting each level of amplitude modulation unit to meet the following conditions:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
NGin+Gn-ATTn>NG+K
wherein K is a margin value.
Optionally, K is 5-10 dB.
The invention has the beneficial effects that:
(1) the distributed amplitude modulation is adopted to improve the noise bottom, the single-stage amplitude modulation and the rear-end multi-stage cascade amplifier in the existing scheme are split and combined to form an amplitude modulation unit consisting of an amplitude modulator, a driver and an amplifier, and then a plurality of amplitude modulation units are cascaded to form a distributed amplitude modulator circuit;
(2) the rise of the noise bottom and the deterioration of the phase noise are avoided, thereby improving the signal quality.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic block diagram of a typical circuit of a conventional microwave signal generator;
FIG. 2 is a schematic block diagram of one embodiment of a microwave signal generator employing the distributed amplitude modulation circuit of the present invention;
FIG. 3 is an exemplary diagram of a prior art single-stage amplitude modulation circuit;
fig. 4 is a schematic block diagram of an alternative embodiment of the distributed amplitude modulation circuit of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The amplitude modulation circuit of the existing microwave signal generator is realized in the form of a single-stage amplitude modulator and a rear-end multistage cascade amplifier, the noise bottom can change along with the signal output power under the condition of large dynamic range of the output power, and the specific expression is that the noise bottom of the output signal is raised and the phase noise is deteriorated under the condition of low-power output, the larger the dynamic range of the signal output power is, the more serious the deterioration is, and the problem seriously affects the noise bottom of the output signal of the microwave signal generator and the phase noise index.
The invention provides a new implementation scheme of an amplitude modulation circuit, which adopts a brand-new architecture, a single-stage amplitude modulator and a rear-end multi-stage cascade amplifier of the existing amplitude modulation circuit are split and combined to form an amplitude modulation unit consisting of the amplitude modulator, a driver and an amplifier, and then a plurality of amplitude modulation units are cascaded to form a distributed amplitude modulation circuit.
The distributed amplitude modulation circuit and the specific embodiment in the microwave signal generator of the present invention will be described in detail with reference to the drawings in the specification.
As shown in fig. 2, the distributed amplitude modulation circuit of the present invention comprises a plurality of amplitude modulation units (2-4, 2-8, … … 2-9) cascaded, each amplitude modulation unit comprising an amplitude modulator, a driving circuit and an amplifier, for example, amplitude modulation unit 1(2-4) comprises amplitude modulator 2-1, driving circuit 2-2 and amplifier 2-3, amplitude modulation unit 2(2-8) comprises amplitude modulator 2-5, driving circuit 2-6 and amplifier 2-7, … …, amplitude modulation unit N (2-9) comprises amplitude modulator, driving circuit and amplifier, the microwave signal generator output power is changed by adjusting the attenuation amount of the amplitude modulator in each amplitude modulation unit, the ALC loop repeats the above dynamic adjustment state all the time, until the detection voltage is equal to the reference voltage, that is, the signal output power is stable when reaching the preset power.
The attenuation of the amplitude modulation unit and the gain of the amplifier can be distributed and adjusted according to specific requirements, 50dB or even larger attenuation of a single-stage amplitude modulator in the existing scheme is distributed through a distributed amplitude modulation circuit, the attenuation of a single amplitude modulation unit is reduced, the attenuation of each stage of amplitude modulation unit is preferably up to a critical point of deteriorating the signal-to-noise ratio, a post-stage amplifier of the amplitude modulator amplifies the signal and the noise at the bottom, the serious deterioration of the signal-to-noise ratio can be effectively avoided, and the noise bottom and phase noise index can be improved under the condition of low power output.
Fig. 2 shows an alternative embodiment of the distributed amplitude modulation circuit of the present invention in a microwave signal generator using ALC technology, which should not be construed as a limitation to the scope of the present invention, and the distributed amplitude modulation circuit of the present invention can also be applied to other circuit forms of the microwave signal generator, and any other circuits that require the application of amplitude modulation, to implement the function of amplitude information modulation.
Optionally, the setting of each level of amplitude modulation unit needs to satisfy the following condition:
NGin+Gn-ATTn>NG+K
wherein NG is the lowest noise bottom of the whole signal link, for example, the noise bottom is-174 dBm/Hz under the ideal condition of room temperature (27 ℃), but the noise bottom of partial devices, such as active devices of frequency dividers, amplifiers and the like, may be higher; NGin is the noise bottom corresponding to the input signal power of Pin; G1-Gn is the amplifier gain of each amplitude modulation unit, and ATT1-ATTn is the attenuation of each amplitude modulator; k is a margin value, each amplitude modulation unit takes the bottom of the undestroyed noise as a principle, and a certain margin is reserved, wherein the K is 5-10 dB.
The distributed amplitude modulation circuit setting needs to satisfy the following conditions:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
wherein G is the total gain required by the signal path, ATT is the total attenuation required by the signal path,
G＝Pmax-Pin
ATT＝Pd
wherein, Pd is the dynamic range of the output power of the signal generator, and Pmax is the maximum output power of the signal generator.
The advantages of the distributed amplitude modulation circuit are further explained below in connection with specific embodiments.
Fig. 3 shows an example of a conventional single-stage amplitude modulation circuit.
In the example, taking an output power dynamic range of 50dB as an example, the maximum power of an output signal 3-5 is +30dBm, the minimum power of the output signal 3-5 is-20 dBm, and assuming that the power of an input microwave signal 3-1 is 0dBm, the bottom of the signal noise is-150 dBm/Hz, then the single-side phase noise far end (frequency offset of 30MHz) is-150 dBc/Hz, in the existing scheme, the maximum power of the output signal is required to be ensured under the ideal condition of neglecting the insertion loss of an amplitude modulator, a directional coupler and a channel, and the fixed gain of a multi-stage cascade amplifier 3-4 is required to be 30 dB; when the output power is-20 dBm, the amplitude modulator 3-2 needs to reach the maximum attenuation amount of 50dB, after 50dB attenuation, the power of the output signal 3-3 of the amplitude modulator in FIG. 3 is-50 dBm, the noise bottom is also attenuated by 50dB, the noise with the noise absolute power of-150 dBm in the 1Hz bandwidth is attenuated by 50dB, but under the ideal condition, the noise bottom is-174 dBm/Hz (actually higher than-174 dBm/Hz), therefore, the noise bottom cannot become-200 dBm/Hz but-174 dBm/Hz; and then amplifying by 30dB through a multi-stage cascade amplifier 3-4, amplifying by 30dB at the bottom of the noise, wherein the power of an output signal 3-5 is-20 dBm, but the bottom of the noise is changed to-144 dBm/Hz, the single-side phase noise frequency offset is 30MHz, the phase noise is degraded to-124 dBc/Hz, the absolute power of the bottom of the noise is degraded to 6dB, and the phase noise is degraded to 26 dB.
The reason for the above problem in the example of fig. 3 is that the single-stage amplitude modulator attenuates the signal amplitude by a large attenuation amount to ensure the dynamic range of the output power of the signal generator, resulting in severe deterioration of the signal-to-noise ratio, deterioration of the noise floor, and deterioration of the phase noise.
Therefore, in order to solve the above problems, the distributed amplitude modulation circuit adopted in the present invention distributes the originally large attenuation amount in each level of modulator for proper attenuation, so as to effectively avoid the noise bottom and the deterioration of phase noise.
Fig. 4 shows an alternative embodiment of the distributed amplitude modulation circuit.
In this optional embodiment, according to the design conditions of the distributed amplitude modulation circuit and each amplitude modulation unit, the distributed amplitude modulation circuit employs 2-level amplitude modulation units, and with the same input/output signal requirements as those in the example of fig. 3, the dynamic range of output power is 50dB, the maximum power of an output signal 4-9 is +30dBm, the minimum power of the output signal is-20 dBm, assuming that the power of an input microwave signal 4-1 is 0dBm, the bottom of the signal noise is-150 dBm/Hz, then the far end of single-side phase noise (frequency offset 30MHz) is-150 dBm/Hz, and the number of amplitude modulation units is 2, that is, the amplitude modulation unit 1 and the amplitude modulation unit 2 in fig. 4; each amplitude modulation unit comprises an amplifier, an amplitude modulator and a driving circuit; the gain of the 1 st-level amplitude modulation unit amplifier 4-2 is set to be 15dB, and the attenuation of the amplitude modulator 4-4 is set to be 25 dB; the gain of the 2 nd-level amplitude modulation unit amplifier 4-6 is set to be 15dB, and the attenuation of the amplitude modulator 4-8 is set to be 25 dB; the signal and noise characteristics through each node are shown in table 1 below,
TABLE 1
| Node point | 4-1 | 4-3 | 4-5 | 4-7 | 4-9 |
| Signal power | 0dBm | 15dBm | -10dBm | +5dBm | -20dBm |
| Noise floor | -150dBm/Hz | -135dBm/Hz | -160dBm/Hz | -145dBm/Hz | -170dBm/Hz |
| Phase noise | -150dBc/Hz | -150dBc/Hz | -150dBc/Hz | -150dBc/Hz | -150dBc/Hz |
As can be seen from Table 1, the noise floor of the output signal is-170 dBm/Hz, the phase noise is-150 dBc/Hz, and neither the noise floor nor the phase noise is deteriorated.
In the embodiment, distributed amplitude modulation is adopted to improve the noise bottom, single-stage amplitude modulation and a rear-end multi-stage cascade amplifier in the existing scheme are split and combined to form an amplitude modulation unit consisting of an amplitude modulator, a driver and an amplifier, and then a plurality of amplitude modulation units are cascaded to form a distributed amplitude modulator circuit.
The invention also proposes a microwave signal generator comprising a distributed amplitude modulation circuit as described above.
The invention also provides a distributed amplitude modulation method, the attenuation is distributed through a plurality of cascaded amplitude modulation units, each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of the microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit.
The distributed amplitude modulation method specifically comprises the following steps:
determining a whole signal link lowest noise bottom NG;
determining input signal power Pin and corresponding noise bottom NGin;
determining the total gain G and the total attenuation ATT required by the signal path according to the dynamic range Pd and the maximum power Pmax of the output power of the signal generator, wherein,
G＝Pmax-Pin
ATT＝Pd
setting the amplifier gain of each level of amplitude modulation unit as G1-Gn, setting the attenuation of each level of amplitude modulator as ATT1-ATTn, and setting each level of amplitude modulation unit to meet the following conditions:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
NGin+Gn-ATTn>NG+K
wherein K is a margin value, and K is 5-10 dB.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. A distributed amplitude modulation circuit is used for a microwave signal generator and is characterized by comprising a plurality of cascaded amplitude modulation units, wherein each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of the microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit;
the setting of each level of amplitude modulation unit meets the following conditions:
NGin+Gn-ATTn>NG+K
wherein NG is the lowest noise bottom of the whole signal link; NGin is the noise bottom corresponding to the input signal power of Pin; G1-Gn is the amplifier gain of each level of amplitude modulation unit; ATT1-ATTn are attenuation of amplitude modulators at each stage; k is a margin value;
the distributed amplitude modulation circuit arrangement satisfies the following conditions:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
wherein G is the total gain required by the signal path, ATT is the total attenuation required by the signal path,
G＝Pmax-Pin
ATT＝Pd
wherein, Pd is the dynamic range of the output power of the signal generator, and Pmax is the maximum output power of the signal generator.
2. The circuit of claim 1, wherein K is 5-10 dB.
3. A microwave signal generator, characterized in that it comprises a distributed amplitude modulation circuit according to any one of claims 1 to 2.
4. A distributed amplitude modulation method is characterized in that attenuation is distributed through a plurality of cascaded amplitude modulation units, each amplitude modulation unit comprises an amplitude modulator, a driving circuit and an amplifier, and the output power of a microwave signal generator is changed by adjusting the attenuation of the amplitude modulator in each amplitude modulation unit;
the method comprises the following steps:
determining a whole signal link lowest noise bottom NG;
determining input signal power Pin and corresponding noise bottom NGin;
determining the total gain G and the total attenuation ATT required by the signal path according to the dynamic range Pd and the maximum power Pmax of the output power of the signal generator, wherein,
G＝Pmax-Pin
ATT＝Pd
setting the amplifier gain of each level of amplitude modulation unit as G1-Gn, setting the attenuation of each level of amplitude modulator as ATT1-ATTn, and setting each level of amplitude modulation unit to meet the following conditions:
G＝G1+G2+…+Gn
ATT＝ATT1+ATT2+…+ATTn
NGin+Gn-ATTn>NG+K
wherein K is a margin value.
5. The distributed amplitude modulation method of claim 4, wherein K is 5-10 dB.
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| CN1144422A (en) * | 1995-03-31 | 1997-03-05 | 株式会社日立制作所 | Output-controlled power amplifier, radio communication terminal and radio communication base station |
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| US6724524B1 (en) * | 2000-08-18 | 2004-04-20 | Corning Incorporated | Gain control in Raman amplifiers |
| EP1450479B1 (en) * | 2003-02-20 | 2012-03-28 | Sony Ericsson Mobile Communications AB | Efficient modulation of RF signals |
| US8126094B2 (en) * | 2009-01-07 | 2012-02-28 | Skyworks Solutions, Inc. | Circuits, systems, and methods for managing automatic gain control in quadrature signal paths of a receiver |
| US9537456B2 (en) * | 2012-10-30 | 2017-01-03 | Eta Devices, Inc. | Asymmetric multilevel backoff amplifier with radio-frequency splitter |
| US9166536B2 (en) * | 2012-10-30 | 2015-10-20 | Eta Devices, Inc. | Transmitter architecture and related methods |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1144422A (en) * | 1995-03-31 | 1997-03-05 | 株式会社日立制作所 | Output-controlled power amplifier, radio communication terminal and radio communication base station |
| CN102099999A (en) * | 2008-07-15 | 2011-06-15 | 日本电气株式会社 | Power amplifier, power amplifier nonlinear distortion correction method, and wireless communication device |
| CN106200751A (en) * | 2016-08-15 | 2016-12-07 | 中国电子科技集团公司第四十研究所 | A kind of intermediate-freuqncy signal Power auto-adjustment circuit and method |
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