CN202210799U - Single-sideband baseband convertor - Google Patents
Single-sideband baseband convertor Download PDFInfo
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- CN202210799U CN202210799U CN2011201603578U CN201120160357U CN202210799U CN 202210799 U CN202210799 U CN 202210799U CN 2011201603578 U CN2011201603578 U CN 2011201603578U CN 201120160357 U CN201120160357 U CN 201120160357U CN 202210799 U CN202210799 U CN 202210799U
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- sideband
- frequency electric
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Abstract
The utility model provides a single-sideband baseband convertor which comprises an orthogonal demodulator and a mid-frequency electric bridge, wherein the orthogonal demodulator comprises a radio frequency signal input end, a local oscillation signal input end, and two output ends; and the mid-frequency electric bridge comprises two input ends and two output ends, and the two input ends are connected with the two output ends of the orthogonal demodulator respectively. The single-sideband baseband convertor performs single-sideband frequency mixing to enable the two output ends of the mid-frequency electric bridge to output the upper and lower sideband signals of the local oscillation signal respectively. Compared with the conventional baseband convertor, the convertor provided by the utility model makes improvement on the basis of commercial devices, so as to realize single sideband signals (the initial frequency of the general commercial single-sideband baseband is dozens of MHz) very close to DC (zero-frequency), realize a very wide baseband bandwidth (20 MHz), enlarge the use range of the baseband, and lower the following-up digitization cost and design difficulty.
Description
Technical field
The utility model relates to radio telescope holographic measurement system, relates more specifically to a kind of monolateral tape base tape switching unit that is used for this holographic measurement system.
Background technology
At present; Existing radio telescope holographic measurement system, for example She Shan 25 meter radio telescope holographic measurement systems mainly adopt Sinosat-1 12.26GHz beacon as signal source; The equipment of using has: test antenna (25m); Reference antenna (1.8 meters), two DVBs, two passages shut down mutually.Fig. 1 is seen in the connection of the various piece of this holographic measurement system in measuring process.The binary channels receiving system that test antenna and reference antenna are formed, two receive paths just the same (except antenna different), antenna receives the Ku wave band (microwave signal of 12.2GHz～12.75GHz); Be input to central tube; Central tube mainly is made up of LNB (Low Noise Block, low noise amplifier module), realizes the amplification to Ku band signal 65dB; In addition signal filtering and Frequency mixing processing have been advanced; The intermediate-freuqncy signal frequency range of the output after the mixing is 900MHz～1450MHz, and the local oscillation signal that mixing is used is to be provided by 10MHz lock phase local vibration source (PLO) as a reference, and frequency is 11.3GHz.Central tube is installed on the antenna, at last the intermediate-freuqncy signal of output (900MHz～1450MHz) through long-distance transmissions, deliver to the baseband converter that is positioned at machine room.Baseband converter mainly realizes double conversion, gain adjustment and filtering; Double conversion is to provide different local oscillation signal and 900MHz～1450MHz to carry out mixing through synthesizer (or being synthesizer), just can wherein arbitrarily the 20MHz frequency band move DC (be direct current 0 frequently)～20MHz.The gain adjustment realizes through the Programmable and Variable attenuator.Filter realizes that the scope of input base band is DC～20MHz.The signal of last base band output is defeated by shutdown mutually simultaneously, and shutdown realizes digitlization and cross-correlation, the auto-correlation processing of signal mutually, calculates the amplitude and the phase difference of two channel signals.
The reception signal that can find out reference antenna and main antenna (test antenna) by Fig. 1 obtains the intermediate-freuqncy signal of 0-20MHz after through twice mixing, and has got into shutdown mutually simultaneously, and real-time processing data in this shuts down mutually is finally with one second fan-out data at interval.
Shutdown mainly realizes function as shown in Figure 2 mutually:
Sampling quantizes the intermediate-freuqncy signal of two passages through 40MHz respectively; Carry out the discrete fast fourier transform (DFFT) of 4096 points then, multiplication cross again obtains the real part and the imaginary part (Re of auto-correlation and cross-correlation; Im), obtain the amplitude and the phase place of the whole baseband signal of 0～20MHz thus:
Because the data volume of handling output in real time from shutting down mutually is big (the auto-correlation phase place and the amplitude that comprise test antenna, the auto-correlation phase place and the amplitude of reference antenna, the cross-correlation phase place and the amplitude of test antenna and reference antenna) very.The whole design of shutdown mutually is on a pci card that has a FPGA, to realize, no longer launches here, detailed design can list of references (Wang Jinqing etc. the realization [C] of shutdown mutually during microwave holography is measured, astronomical research and technology, 2010 the 7th volume first phases).
In measuring process, main antenna carries out grid type scanning with different angles to signal source around the direction of signal source, the grid that NxN as shown in Figure 3 is ordered (how much relation being arranged of scanning grid) with certainty of measurement, and reference antenna is all the time facing to signal source.Variation along with scanning angle; Test antenna will produce phase difference with fixing reference antenna; Be collected in phase place and amplitude information (just having obtained the far field " hologram " of antenna) on each location point, just can release the surface deformation of main antenna then through formula.
Certainly in the holographic measurement system of reality, on data processing, to do a large amount of work, may be summarized to be following flow process, as shown in Figure 4.Cross-correlation phase place, amplitude that relevant back data message shuts down mutually and exports from hardware, and the auto-correlation amplitude information of two antennas.Main antenna points to data, refers to time, orientation and the pitching information of main antenna real time record when doing scanning around satellite, and state information.Through above two data; Cross-correlation phase information in the time of just can be the network scanning state accurately extracts (far-field information that this information is exactly main antenna); Also just can provide the record data of data quality accessment this time; After the grid data calibration is good; According to the mathematical relationship of antenna far field and aperture field, just can find the solution the aperture field information of antenna out from far-field information through two-dimentional inverse Fourier transform, so just known the deformation situation (being exactly the gradient search of face shape, the reconstruct of face shape) of bore face in mapping process.Be the statistical information and the output of drawing at last.Relevant back data message is seen off by shutdown mutually, has comprised the information such as amplitude, phase place, time of binary channels inband signaling, and main antenna points to information such as position that data have comprised antenna, time, state, and these two files can connect through temporal information.
In this holographic measurement system, baseband converter need realize that 500MHz～4000MHz moves function to the monolateral band of base band, and the initial frequency of base band is DC.
It is most important index that the bandwidth of base band, mirror image suppress.Mixing can realize moving of frequency spectrum through inserting local oscillator and radiofrequency signal, moves base band to the signal about local frequency, is positioned at that signal is called upper side band signal above the local oscillator, is positioned at the lower sideband signal that is called below the local oscillator.But directly the mixing meeting is moved the last lower sideband of local oscillator simultaneously and is got off to become baseband signal, and can't differentiate upper sideband or lower sideband.Can realize after the separation of lower sideband exporting respectively the last lower sideband signal of base band from two ports through particular processing; But; Because factors such as device; The signal of two sidebands is always isolated halfway phenomenon, and the signal that in other words is exactly upper sideband has drained to the lower sideband port, has become the image signal of lower sideband; And lower sideband signal has drained to the image signal that the upper sideband port has become upper sideband, and it is more little good more that this leaks signal in the past, and this just comes quantitative appraisal with mirror image inhibition ability.Existing baseband converter adopts quadrature demodulator and simulation phase shift electric bridge to realize; Generally; The baseband converter that designs in this way is difficult to take into account low-frequency range (because the broad band low frequency electric bridge is difficult to design), broadband character (general low frequency electric bridge is difficult to accomplish 20KHz～20MHz bandwidth), the well mirror image suppression characteristic, and cheap price of base band.
The conventional design of monolateral tape base tape switching unit is as shown in Figure 5.Mainly containing quadrature demodulator and intermediate frequency electric bridge among Fig. 5 forms; Whole process is exactly in order to realize the mixing of monolateral band; LO is a local oscillation signal, and RF is a radiofrequency signal, can know through relevant mathematical analysis; The G of output and H end is exported the last lower sideband signal of Lo respectively at last, and does not have the image frequency composition.Electric bridge realizes that mainly 90 degree phase shifts and power of signal are synthetic, synthesizes at the G point through meeting behind the intermediate frequency electric bridge such as the signal of E point and F electricity, and the signal of E does not have phase shift in the building-up process, and the signal phase shift of F point 90 spend; Same H point also has the signal after synthesizing, but the signal of H point output is E point phase shift 90 degree, and the F point does not have phase shift.Adjustable attenuator and amplifier have been omitted in front and back, because this is to adopt commercial component to realize.It is exactly upper and lower single sideband singal that G point and H point come out.But the initial frequency that common G point and H are ordered is difficult to reach DC, generally all is tens MHz.Just on the intermediate frequency electric bridge, present commercial intermediate frequency electric bridge does not still have to reach the 50KHz initial frequency difficult point of all designs, reaches 20MHz's with Time Bandwidth.And the performance of intermediate frequency electric bridge has determined the mirror image rejection of last base band to a great extent.
The utility model content
The utility model technical problem to be solved is to provide a kind of monolateral tape base tape switching unit that can improve the mirror image rejection.
A kind of monolateral tape base tape switching unit comprises: quadrature demodulator, comprise RF signal input end and local oscillation signal input, and two outputs; The intermediate frequency electric bridge comprises two inputs and two outputs, and said two inputs link to each other respectively with two outputs of said quadrature demodulator; Said monolateral tape base tape switching unit carries out single sideband mixing so that two outputs of said intermediate frequency electric bridge are exported the upper and lower sideband signals of said local oscillation signal respectively.
Said intermediate frequency electric bridge comprises phase shifting part and signal composite part, and said phase shifting part is used to make the signal from two inputs of said intermediate frequency electric bridge to carry out 90 degree phase shifts, and said signal composite part is used to make the signal of said phase shifting part output to synthesize.
Said phase shifting part comprises the two-way phase-shift circuit that links to each other with two inputs of said intermediate frequency electric bridge respectively and be made up of the all-pass filter cascade.
Said signal composite part comprises the adder that is made up of operational amplifier that links to each other with the output of said two-way phase-shift circuit.
Said signal composite part also comprises the subtracter that is made up of operational amplifier that links to each other with the output of said two-way phase-shift circuit.
The monolateral tape base tape switching unit of the utility model is compared with existing baseband converter on the basis of commercial devices, to have done and is improved design; Can realize the single sideband singal (general commercial monolateral tape base take up beginning frequency all from tens MHzs initial) of ten minutes near DC (0 frequently); Realize relatively very wide baseband bandwidth (20MHz), enlarged the usable range of base band.Back digitlization ground cost and design difficulty (because the 100MHz sampling is very cheap with interior digital system) have been alleviated.
Description of drawings
Fig. 1 shows the system block diagram of existing holographic measurement system;
Fig. 2 shows the schematic diagram of shutdown mutually in this holographic measurement system;
Fig. 3 shows the grid type scintigram that the NxN of main antenna in this holographic measurement system is ordered;
Fig. 4 shows the flow chart of data processing figure in this holographic measurement system;
Fig. 5 shows the sketch map of the baseband converter in this holographic measurement system;
Fig. 6 shows the simple model figure of the single-stage all-pass filter in the monolateral tape base tape switching unit of the utility model;
Fig. 7 shows the single-point frequency phase shifts sketch map when f changes in the model shown in Figure 6;
Fig. 8 shows amplifier add operation sketch map;
Fig. 9 shows 90 degree phase-shift circuits of the intermediate frequency electric bridge in the monolateral tape base tape switching unit of the utility model;
Figure 10 shows the emulation of 90 degree phase-shift circuits shown in Figure 9;
Figure 11 shows the signal synthesis circuit of the intermediate frequency electric bridge in the monolateral tape base tape switching unit of the utility model.
Embodiment
Below in conjunction with accompanying drawing the utility model is described in detail.
The major function of the application's monolateral tape base tape switching unit is to realize that 500MHz～4000MHz moves function to the monolateral band of base band, and the initial frequency of base band is DC.
The monolateral tape base tape switching unit of the utility model and the difference of existing baseband converter not only are the design of intermediate frequency electric bridge, have also adopted the part of commercial IQ demodulation as baseband converter, and be more excellent than existing baseband-converted performance.
In the monolateral tape base tape switching unit of the utility model, multistage (10 grades) all-pass filter that the intermediate frequency electric bridge adopts broadband operational amplifier to form is accomplished, and is synthetic then adopt the addition and the subtraction function realization of amplifier.
Arrowed radio-frequency bridge (being positioned at quadrature demodulator inside) is the same among the function of intermediate frequency electric bridge and Fig. 5, mainly realizes the function of 90 degree phase shifts and addition, and the signal of order such as G is that addition result are afterwards spent in signal and the F point signal phase shift 90 of E; The signal that H is ordered is F point signal and E point signal phase shift 90 degree back addition result.
The single-stage all-pass filter can be realized the function of single-point frequency displacement phase, comprises 90 degree phase shifts, but can not realize (0～20MHz) phase shift of the desired broadband of intermediate frequency electric bridge.The simple model of single-stage all-pass filter is as shown in Figure 6.
When R1=RF; Can obtain output voltage and input voltage ratio A
uFor:
And phase place is
Wherein
Therefore, work as f=f
0The time, can realize the phase shifts of 90 degree, f wherein
0Be the resonance frequency of RC, f is the achievable signal frequency will of entering system.Just can realize single-point as shown in Figure 7 phase shifts frequently and change f.
Based on above single-stage characteristic, because f
0Confirm by RC decision, therefore, change RC and just can realize different f
0On 90 the degree phase shifts, if get up multi-stage cascade just can realize the phase shift in broadband.
Fig. 9 shows 90 degree phase-shift circuits of the intermediate frequency electric bridge in the monolateral tape base tape switching unit of the utility model.Wherein importing E and F is input port (E and the F of corresponding diagram 5 intermediate frequency electric bridges respectively), and M and N are output port (it is the input of signal composite part, sees below), have write out the f that RC at different levels produce among the figure
0
Figure 10 is the emulation to the phase-shift circuit of Fig. 9; Abscissa is a frequency, and ordinate is the signal difference of M and N, can see; The phase shift function (slightly poor at high band and low-frequency range effect) that in whole 20MHz bandwidth, all has 90 degree, this is a key index of realizing that good mirror image suppresses.
The intermediate frequency electric bridge also will be realized the synthetic of two paths of signals except phase shift, and just the power of two paths of signals is synthetic, and the add operation of the synthetic employing of signal amplifier is as shown in Figure 8.The signal synthesis circuit of the intermediate frequency electric bridge of the utility model is specifically seen shown in Figure 11; M and N are input port (delivery outlets of front phase-shift circuit just); G and H are output port (the intermediate frequency electric bridge delivery outlets among Fig. 5 just), export upper sideband and lower sideband signal respectively.The output of G realizes through being barricaded as adder to operational amplifier among the figure, and the output of H realizes through being barricaded as subtracter to operational amplifier.
In addition through changing the gain that R38 and R42 can also control G and H output respectively.
Be to adopt a arrangement of mirrors that the utility model baseband converter measures at last as the rejection form below:
Can see that from 100KHz to 20MHz going up mirror image suppresses all fine, though performance descends to some extent below 0.5MHz, but the inhibition ability of 7～8dB arranged, this is not easy very much.
The preferred embodiment that the above is merely the utility model is not the scope in order to qualification the utility model, and the foregoing description of the utility model can also be made various variations.Be that every simple, equivalence of doing according to the claims and the description of the utility model application changes and modification, all fall into the claim protection range of the utility model.
Claims (5)
1. a monolateral tape base tape switching unit is characterized in that, comprising:
Quadrature demodulator comprises RF signal input end and local oscillation signal input, and two outputs;
The intermediate frequency electric bridge comprises two inputs and two outputs, and said two inputs link to each other respectively with two outputs of said quadrature demodulator.
2. monolateral tape base tape switching unit as claimed in claim 1; It is characterized in that; Said intermediate frequency electric bridge comprises phase shifting part and signal composite part; Said phase shifting part is used to make the signal from two inputs of said intermediate frequency electric bridge to carry out 90 degree phase shifts, and said signal composite part is used to make the signal of said phase shifting part output to synthesize.
3. monolateral tape base tape switching unit as claimed in claim 2 is characterized in that, said phase shifting part comprises the two-way phase-shift circuit that links to each other with two inputs of said intermediate frequency electric bridge respectively and be made up of the all-pass filter cascade.
4. monolateral tape base tape switching unit as claimed in claim 3 is characterized in that, said signal composite part comprises the adder that is made up of operational amplifier that links to each other with the output of said two-way phase-shift circuit.
5. monolateral tape base tape switching unit as claimed in claim 4 is characterized in that, said signal composite part also comprises the subtracter that is made up of operational amplifier that links to each other with the output of said two-way phase-shift circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201603578U CN202210799U (en) | 2011-05-18 | 2011-05-18 | Single-sideband baseband convertor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201603578U CN202210799U (en) | 2011-05-18 | 2011-05-18 | Single-sideband baseband convertor |
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| Publication Number | Publication Date |
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| CN202210799U true CN202210799U (en) | 2012-05-02 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN2011201603578U Expired - Fee Related CN202210799U (en) | 2011-05-18 | 2011-05-18 | Single-sideband baseband convertor |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102820870A (en) * | 2011-06-10 | 2012-12-12 | 中国科学院上海天文台 | 90-degree active bridge with ultra-broad band |
| CN106788501A (en) * | 2017-02-21 | 2017-05-31 | 成都沃邦德科技有限公司 | A kind of receiver suppressed with mirror image high |
-
2011
- 2011-05-18 CN CN2011201603578U patent/CN202210799U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102820870A (en) * | 2011-06-10 | 2012-12-12 | 中国科学院上海天文台 | 90-degree active bridge with ultra-broad band |
| CN102820870B (en) * | 2011-06-10 | 2015-07-01 | 中国科学院上海天文台 | 90-degree active bridge with ultra-broad band |
| CN106788501A (en) * | 2017-02-21 | 2017-05-31 | 成都沃邦德科技有限公司 | A kind of receiver suppressed with mirror image high |
| CN106788501B (en) * | 2017-02-21 | 2022-06-21 | 成都沃邦德科技有限公司 | Receiver with high image rejection |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20120502 Termination date: 20190518 |
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| CF01 | Termination of patent right due to non-payment of annual fee |