CN203661076U - Circuit for measuring emergency mode radio-frequency signal - Google Patents
Circuit for measuring emergency mode radio-frequency signal Download PDFInfo
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- CN203661076U CN203661076U CN201320629698.4U CN201320629698U CN203661076U CN 203661076 U CN203661076 U CN 203661076U CN 201320629698 U CN201320629698 U CN 201320629698U CN 203661076 U CN203661076 U CN 203661076U
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Abstract
The utility model discloses a circuit for measuring an emergency mode radio-frequency signal. The circuit comprises a phase-locked loop (PLL) circuit (U1), a frequency mixer (U2), an amplification circuit (U3), a band pass filter (U4), a radio-frequency detector (U5), a peak value detector (U8), an AD sampling circuit (U9) and a CPU (U11) which are sequentially electrically connected. The circuit is characterized in that a control switch (U7) is disposed between the radio-frequency detector (U5) and the peak value detector (U8); a comparator (U6) is disposed between the radio-frequency detector (U5) and the control switch (U7); an output end of the comparator (U6) is connected with the CPU (U11); and a reset switch (U10) is disposed between the peak value detector (U8) and the CPU (U11). The beneficial effects of the circuit for measuring the emergency mode radio-frequency signal are that low-cost conventional devices are utilized, and detection of the emergency radio-frequency signal or power detection of noise in a microsecond-scale time of duration is realized.
Description
Technical field
The utility model belongs to a kind of circuitry for signal measurement, relates to specifically a kind of measuring circuit for burst mode radiofrequency signal.
Background technology
Cable TV network, be called for short the hfc plant (abbreviation of Fiber Coax, the Chinese meaning is hybrid fiber coax) be such network: there is headend equipment to carry out the bridge joint of cable TV signal processing and data-signal at local side, basic routing line uses optical fiber or loss coaxial cables transportation simulator and digital carrier signal, use Coaxial distribution network network allocation of downlink carrier signal in user community, converge upstream data carrier signal.
By sense, in hfc plant, there are two kinds of signals of uplink and downlink, downstream signal is transferred to each user family from front end with the form of broadcast, and upward signal is that point-to-point form passes back to local side from user.Downstream signal is also forward signal, and upward signal is also reverse signal.
At present, the data service of progressively carrying out in hfc plant is interactive service, not only has the downstream signal that is sent to user from front end, the upward signal of uploading from user in addition.Data-signal need to be modulated onto on radio-frequency carrier and just be conducive to transmit in hfc plant, and uplink and downlink carrier signal is multiplexing in hfc plant in the mode of frequency division.The existing access way of utilizing hfc plant has DOCSIS, the technology such as the EOC of various systems.No matter use which kind of technology, upward signal is all to use burst mode to transmit radio-frequency carrier, only in just transmitted signal of specific moment.
In addition, the up-downgoing transmission channel of CATV HFC Network is asymmetrical, because the transmission means of its down channel is broadcast mode, therefore has good transmission characteristic and higher signal to noise ratio, can reach the technical requirement of communications completely.The subject matter that affects HFC system transmission quality is the noise that comes from up channel.In two-way HFC system, because cable transmission part in hfc plant is generally dendritic topological structure, user uses upstream bandwidth jointly to optical node signal return, therefore the noise of being introduced by user terminal and cable machinery produces serious converging in up-link, cause so-called " funneling effect ", thereby have a strong impact on the performance of up channel.
Funneling effect is to be determined by the structure of its network, in tree network structure, disturb the front end at cable system from noise and the invasion of user and network internal generation, the tree root place that is network is gathered together, for data feedback channel, the noise contribution that each amplifier produces all converges in the front end of system, and this noise contribution is proportional to the scale of system, is proportional to the quantity of upstream amplifier in same tree network.Moreover, the various noise contributions that each user terminal produces and picks up also will converge to through data feedback channel the front end of system, and this part noise contribution is proportional to the number of users of the same tree network of access.The converging phenomenon of this noise is just called as noise funneling effect.
The classification of noise is divided into internal noise and the large class of external noise two.Internal noise is by unwanted vibration, and hum and microphone effect cause, are mainly that thermal noise and Johnson noise disturb, and wherein take thermal noise as main, and cannot eliminate, and are called construct noise.External noise, we are called invasion noise, and the generation source of invasion noise is impulse disturbances noise, three kinds of radiated noise and induced noises, the source of upstream noise is a lot, conventionally can be divided into four kinds:
Impulse disturbances noise: impulse disturbances noise is a kind of random in the noise floor of cable television system of superposition, uncertain radio noise is general only to be continued less than centisecond, this typical random disturbances has artificial source to produce, as the arc light that household electrical appliance switch, spark, the motor rotor of family expenses apparatus, electric saw, automobile igniter, vacuum cleaner, cellular momentary pulse etc., or the electromagnetic energy that on live wire, abnormal switching device etc. produces.These disturb the infra-low frequency section that all may occur in lower than 5MHz, but their harmonic wave will extend to the frequency range of backward channel, because these interference generally can not occur simultaneously, so be random on the impact of system, impact may be not too large, once affect while occurring very large simultaneously.
Wideband pulse noise come from all can arc discharges or the electric equipment generating an electromagnetic field and natural noise source, change fast in time, its impact is that to make be that the error rate raises.Although the frequency spectrum of impulsive noise is not necessarily in backward channel, because its amplitude is higher, its each harmonic also exerts an influence to backward channel.
Radiated noise disturbs: radiated noise disturb have artificial with unartificial two kinds, as short-wave radio set, amateur radio station, the two-way communication of taxi, the interference of the single-frequency continuous wave of various interactive type communication equifrequents in 5～30MHz, they are coupled in up channel by user terminal and distribution facility in the time of atmospheric propagation, and are in time slow variation, cause the decline of channel capacity.In the frequency range of 5～40MHz, it is main interference source that shortwave disturbs.Radiated interference is the main source of return path noise.
Inductive interference noise: induced noise is generally in 2kHz～50kHz scope.The most obvious example is lightning, the electromagnetic interference and the bad electric discharge phenomena of electric equipment that also have high-voltage line and power distribution station to produce.This interference spectrum is narrow, although may feed through to return path, impact is not returned very large.
Internal noise disturbs: internal noise disturbs and directly comes from cable television system part, as subscriber terminal equipment, and faulty equipment, defective joint and mains switch etc.Because each user's situation varies, in the time using various electrical equipment, can by mistake produce intentionally interference signal and the noise of channel below 30MHz, once these interference signals and noise are coupled into backward channel, just can produce interference, these noises are often difficult to control, and have very large randomness and persistence.
Above-mentioned upward signal or noise all show the characteristic of burst.At present how handheld test instrument is on the market measured by the mode of frequency conversion, as the principle framework figure (Fig. 1) of traditional radiofrequency signal measuring circuit.Radio-frequency input signals and pll output signal mixing are exported intermediate-freuqncy signal after amplifying, through band pass filter laggard enter radio frequency wave detector output voltage signal, after peak detection, through AD sample circuit, analog voltage signal is converted to digital signal, after CPU processes, can be sent to display device.Change PLL phase-locked loop frequency by CPU, can realize different frequency signals and measure.For improving test performance, can be by selecting high-speed AD sampling device to improve field scan speed, thus detecting uplink burst signal or random noise disturbance.
At present, for saving cost, conventional hand-hold type instrument on the market adopts common low speed devices to realize.The defect of its existence is: one, and the feature of uplink burst burst or noise is random, the process of short time, before AD has sampled, may disappear through the voltage signal of peak-detector circuit output, is therefore difficult for capturing this class signal.Its two, by adopting high-speed AD device to improve peak detection frequency, can increase the acquisition probability of burst or noise, but high speed device relative cost is high simultaneously, and must brings power consumption to increase.
Utility model content
The deficiency existing in order to overcome above technology, the utility model provides the measuring circuit for burst mode radiofrequency signal of a kind of handheld test instrument low cost, low-power consumption requirement.
The purpose of this utility model is under the prerequisite of not obvious increase cost, uses commonplace components to solve the problem of uplink burst signal or random noise disturbance test.
A kind of measuring circuit for burst mode radiofrequency signal, it comprises the PLL phase-locked loop circuit, frequency mixer, amplifying circuit, band pass filter, radio frequency wave detector, peak detector, AD sample circuit, the CPU that are electrically connected successively, it is characterized in that: between radio frequency wave detector and peak detector, be provided with control switch, between radio frequency wave detector and control switch, be provided with comparator, it is upper that described comparator output terminal is connected in CPU, between peak detector and CPU, is provided with reset switch;
Described comparator, for triggering the burst radiofrequency signal or the noise that come from input, produces burst and detects interrupt signal, thereby cause that CPU produces interruption, after time delay, CPU disconnects control switch, thereby close peak detector input, make peak detector enter peak value and keep the stage.
Described amplifying circuit is intermediate frequency amplifier circuit;
Described comparator is high-speed comparator.
The concrete beneficial effect of the utility model is: produce interruption by high-speed comparator, thereby CPU catches this interruption closing control switch, make peak-detector circuit enter peak value and keep the stage, then AD sample circuit work, thus complete burst mode signal or noise measuring; Utilize conventional device cheaply, realize the burst radiofrequency signal of Microsecond grade duration or the power detection of noise.
Accompanying drawing explanation
Below in conjunction with drawings and Examples of the present utility model, the utility model is further described in detail.
Fig. 1 is the principle framework figure of traditional radiofrequency signal measuring circuit;
Fig. 2 is principle framework figure of the present utility model;
Fig. 3 is local circuit schematic diagram of the present utility model.
In figure: U1.PLL phase-locked loop circuit, U2. frequency mixer, U3. amplifying circuit, U4. band pass filter, U5. radio frequency wave detector, U6. comparator, U7. control switch, U8. peak detector, U9.AD sample circuit, U10. reset switch, U11.CPU.
Embodiment
As shown in Figure 2, for a measuring circuit for burst mode radiofrequency signal, it comprises PLL phase-locked loop circuit U1, the frequency mixer U2, amplifying circuit U3, band pass filter U4, radio frequency wave detector U5, peak detector U8, AD sample circuit U9, the CPUU11 that are electrically connected successively.Between radio frequency wave detector U5 and peak detector U8, be provided with control switch U7, between radio frequency wave detector U5 and control switch U7, be provided with comparator U6, it is upper that described comparator U6 output is connected in CPUU11, is provided with reset switch U10 between peak detector U8 and CPUU11; Described amplifying circuit U3 is intermediate frequency amplifier circuit; Described comparator U6 is high-speed comparator.
PLL phase-locked loop circuit U1 function: it can produce the oscillator signal of characteristic frequency under the control of CPUU11.CPUU11 can communicate by IIC communication mode and PLL phase-locked loop circuit U1, and then changes frequency of oscillation.
Frequency mixer U2 function: the oscillator signal that radio-frequency input signals and PLL phase-locked loop produce enters after frequency mixer U2, produces and frequency and difference frequency frequency, can be fixed the intermediate-freuqncy signal of frequency by suitable filtering.
Amplifying circuit U3 is an intermediate frequency amplifier circuit, and its function is for amplifying the intermediate-freuqncy signal after mixing, to improve the detectability of radio frequency wave detector U5.
Band pass filter U4 function: for suppressing the radiofrequency signal outside intermediate frequency, improve signal to noise ratio.
Radio frequency wave detector U5 function: for intermediate frequency radiofrequency signal is converted to voltage signal.
High-speed comparator U6 function: for triggering the burst radiofrequency signal or the noise that come from input, produce burst and detect interrupt signal, this interrupt signal is connected to CPUU11 external interrupt pin, thereby cause that CPUU11 produces interruption, after suitable time delay, CPUU11 disconnects control switch U7, thereby closes peak detector U8 input, makes peak detector U8 enter peak value and keeps the stage.
Peak detector U8 entered after the peak value maintenance stage, and under the control of CPUU11, AD sample circuit U9 starts working, and peak voltage signal is converted to digital signal, delivers to CPUU11 and carry out subsequent treatment after having sampled.CPUU11 handles after this sampling, controls reset switch U10 and discharges peak holding circuit voltage, makes it to accept new input signal.Then Closed control switch U7, to test next time.
As shown in Figure 2 and Figure 3, PLL phase-locked loop circuit U1, the function that it is realized is the output of PLL phase-locked loop, signal mixing and amplification, and then output 36MHz or 44MHz intermediate-freuqncy signal, intermediate-freuqncy signal, after band pass filter U4, enters radio frequency wave detector U5, and intermediate-freuqncy signal is output voltage signal after double conversion again.CPUU11 has built-in high-speed comparator, and the voltage signal of radio frequency wave detector U5 output is connected to CPUU11, when magnitude of voltage is greater than after the value of setting, produces external interrupt.CPUU11 produces after external interrupt, by program control suitable time-delay, then disconnects control switch U7, makes the peak detector being made up of D801 and C831 enter peak value sampling hold mode.Then carry out voltage sample by the CPUU11 of built-in AD sampling functions, obtain burst radiofrequency signal sampled voltage.CPUU11 handles after this sampling, controls reset switch U10 and discharges peak holding circuit voltage, makes it to accept new input signal.Then Closed control switch U7, to test next time.
Above disclosed is only preferred embodiment of the present utility model, certainly can not limit the utility model practical range with this.All do according to the utility model application range equalization change with improve, within all should still belonging to patent covering scope of the present utility model.
Claims (3)
1. the measuring circuit for burst mode radiofrequency signal, it comprises the PLL phase-locked loop circuit (U1) of electrical connection successively, frequency mixer (U2), amplifying circuit (U3), band pass filter (U4), radio frequency wave detector (U5), peak detector (U8), AD sample circuit (U9), CPU(U11), it is characterized in that: between radio frequency wave detector (U5) and peak detector (U8), be provided with control switch (U7), between radio frequency wave detector (U5) and control switch (U7), be provided with comparator (U6), described comparator (U6) output is connected in CPU(U11) on, peak detector (U8) and CPU(U11) between be provided with reset switch (U10),
Described comparator (U6), for triggering the burst radiofrequency signal or the noise that come from input, produce burst and detect interrupt signal, thereby cause CPU(U11) produce and interrupt, after time delay, CPU(U11) disconnect control switch (U7), thereby close peak detector (U8) input, make peak detector (U8) enter peak value and keep the stage.
2. a kind of measuring circuit for burst mode radiofrequency signal according to claim 1, is characterized in that: described amplifying circuit (U3) is intermediate frequency amplifier circuit.
3. a kind of measuring circuit for burst mode radiofrequency signal according to claim 1, is characterized in that: described comparator (U6) is high-speed comparator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320629698.4U CN203661076U (en) | 2013-10-12 | 2013-10-12 | Circuit for measuring emergency mode radio-frequency signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201320629698.4U CN203661076U (en) | 2013-10-12 | 2013-10-12 | Circuit for measuring emergency mode radio-frequency signal |
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| CN203661076U true CN203661076U (en) | 2014-06-18 |
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| CN201320629698.4U Expired - Fee Related CN203661076U (en) | 2013-10-12 | 2013-10-12 | Circuit for measuring emergency mode radio-frequency signal |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106301371A (en) * | 2016-08-15 | 2017-01-04 | 四川华索自动化信息工程有限公司 | A kind of calcining kiln flue temperature monitoring device phase-locked ring type signal processing system |
| CN106325123A (en) * | 2016-08-15 | 2017-01-11 | 四川华索自动化信息工程有限公司 | Multi-circuit hybrid signal processing system for flue temperature monitoring device |
| CN106353591A (en) * | 2016-10-21 | 2017-01-25 | 成都前锋电子仪器有限责任公司 | Average burst power measurement circuit |
| CN106569020A (en) * | 2016-10-20 | 2017-04-19 | 成都前锋电子仪器有限责任公司 | Power sensor for radio frequency power reflectometer |
-
2013
- 2013-10-12 CN CN201320629698.4U patent/CN203661076U/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106301371A (en) * | 2016-08-15 | 2017-01-04 | 四川华索自动化信息工程有限公司 | A kind of calcining kiln flue temperature monitoring device phase-locked ring type signal processing system |
| CN106325123A (en) * | 2016-08-15 | 2017-01-11 | 四川华索自动化信息工程有限公司 | Multi-circuit hybrid signal processing system for flue temperature monitoring device |
| CN106569020A (en) * | 2016-10-20 | 2017-04-19 | 成都前锋电子仪器有限责任公司 | Power sensor for radio frequency power reflectometer |
| CN106353591A (en) * | 2016-10-21 | 2017-01-25 | 成都前锋电子仪器有限责任公司 | Average burst power measurement circuit |
| CN106353591B (en) * | 2016-10-21 | 2023-05-16 | 成都前锋电子仪器有限责任公司 | Average burst power measuring circuit |
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| Date | Code | Title | Description |
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| 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: 20140618 Termination date: 20151012 |
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| EXPY | Termination of patent right or utility model |