CN202856715U - System for realizing spectrum analyzer down-conversion with broadband local oscillators and high-frequency phase demodulation - Google Patents
System for realizing spectrum analyzer down-conversion with broadband local oscillators and high-frequency phase demodulation Download PDFInfo
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- CN202856715U CN202856715U CN 201220568779 CN201220568779U CN202856715U CN 202856715 U CN202856715 U CN 202856715U CN 201220568779 CN201220568779 CN 201220568779 CN 201220568779 U CN201220568779 U CN 201220568779U CN 202856715 U CN202856715 U CN 202856715U
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Abstract
The utility model discloses a system for realizing spectrum analyzer down-conversion with broadband local oscillators and high-frequency phase demodulation. A radio frequency signal enters a radio frequency front end channel and then is subjected to image frequency filtering through a first filter, and then is sent to a first mixer and is subjected to frequency mixing with a first local oscillator to generate a first intermediate frequency, the first intermediate frequency is subjected to filtering through a second filter and then is sent to a second mixer and is subjected to frequency mixing with a second local oscillator to generate a second intermediate frequency, the second intermediate frequency is subjected to filtering through a third filter and then is sent to a third mixer and is subjected to frequency mixing with a third local oscillator to generate a third intermediate frequency, after the radio frequency down-conversion is completed, the third intermediate frequency is outputted to a digital intermediate frequency processing portion to undergo corresponding spectral analysis, and a first local oscillator phase-locked loop is composed of a broadband voltage-controlled oscillator, a frequency divider, a high-frequency phase demodulator, a high-frequency phase demodulation reference and a loop filter. The broadband voltage-controlled oscillator is subjected to frequency division through the frequency divider and then is subjected to phase demodulation with the high-frequency phase demodulation reference in the high-frequency phase demodulator, and an error signal is subjected to integral computation and filtering through the loop filter and then an error voltage is output, wherein the error voltage is fed back to the broadband voltage-controlled oscillator.
Description
Technical field
The present invention relates to the communication test field, especially the system of Spectrum Analyzer radiofrequency signal down-conversion is specially the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion.
Background technology
Spectrum Analyzer now is when carrying out down-converted to radiofrequency signal, basically all be to take the superhet technology, " heterodyne " namely is frequency spectrum shift, the radio-frequency input signals of certain limit respectively with what local oscillator mixing after, obtain the analog if signal of a fixed frequency, this fixing analog intermediate frequency is generally tens000000 to tens, is convenient to satisfy the requirement of ADC sampling and follow-up Digital Signal Processing, and intermediate-freuqncy signal carries out finishing corresponding spectrum analysis after the digitlization.And realize that radio frequency down-conversion generally has two kinds of methods: the one, adopt two wave bands of height to realize down-conversion, low band adopts the scheme of high intermediate frequency, high band adopts the mode that down is mixed to Low Medium Frequency, this mode the first local oscillator initial frequency is low, coverage does not need to reach the radio frequency input range yet, but the obvious shortcoming of this scheme is that when working in high band the realization of band pass filter and full frequency band switch the complexity that seems, and affect the entire scan time; The 2nd, the implementation of overall height intermediate frequency, the i.e. selection of the first intermediate frequency is higher than the upper limit of radio-frequency input signals scope, therefore the initial frequency of the first local oscillator is the first intermediate frequency, coverage is the radiofrequency signal input range, the phase demodulation frequency of the first local oscillator phase-locked loop generally only has 10,000,000 to tens, limited like this bandwidth of phase-locked loop, and the phase noise of the first local oscillator has directly determined the phase noise index of frequency spectrograph, if use the broadband local oscillator of first overtone journey, be subjected to the restriction of local oscillator noise, the outer phase noise of bandwidth then is difficult to reach requirement, so generally broadband local oscillator is decomposed into several narrow-band local oscillations, as shown in Figure 1, to improve the phase noise index, but the shortcoming that this mode is brought is that the switching controls of several narrow-band local oscillations is complicated, affects equally sweep speed.
Summary of the invention
Technical problem to be solved: the invention provides a kind of system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion for above problem, by improving phase demodulation frequency, the broadband local oscillator single pass is finished and is entirely swept wide covering, solve complicated, the slow problem of sweep speed of traditional down conversion method control, and can improve the index such as complete machine phase noise.
Technical scheme: the invention provides a kind of system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion for above deficiency, comprise the first filter, the first frequency mixer, the first local oscillator, the second frequency mixer, the second filter, the second local oscillator, three-mixer, the 3rd filter, the 3rd local oscillator, digital intermediate frequency; Radiofrequency signal enters behind the radio-frequency front-end passage through the first filter filtering image frequency, deliver to the first frequency mixer and produce the first intermediate frequency with the first local oscillator mixing, deliver to after the filtering of the first intermediate frequency through the second filter the second frequency mixer and with the second local oscillator mixing after produce the second intermediate frequency, deliver to after the second intermediate frequency is processed through the 3rd filter filtering three-mixer and with the 3rd local oscillator mixing after produce the 3rd intermediate frequency, after finishing radio frequency down-conversion, the 3rd intermediate frequency exports Digital IF Processing to and partly finishes corresponding spectrum analysis, it is characterized in that: described the first local oscillator phase-locked loop is by wideband voltage controlled oscillator, frequency divider, the high frequency phase discriminator, the reference of high frequency phase demodulation and loop filter form; Wideband voltage controlled oscillator through behind the frequency divider frequency division in the high frequency phase discriminator with the high frequency phase demodulation with reference to phase demodulation, error signal through loop filter integration, filtering after output error voltage and feed back to wideband voltage controlled oscillator.
The high frequency phase demodulation of described the first local oscillator phase-locked loop is with reference to selecting OCXO " constant-temperature crystal oscillator ".
Described loop filter adopts output voltage range to surpass 20 volts multistage active loop filter.
The loop bandwidth of described the first local oscillator phase-locked loop is 200kHz.
Described the first filter, the second filter, the 3rd filter are low pass filter.
Described the first intermediate frequency is the high intermediate frequency of 4000MHz.
The output of described the first local oscillator phase-locked loop is controlled by the control system based on ARM.
Beneficial effect: 1. because the first local oscillator is selected the broadband local oscillator of disposable tuning covering radio frequency input range, do not need to be divided into several narrow-band local oscillations and realize full frequency band scanning by switching, simplified control procedure, solved simultaneously the problem of the increase sweep time that is brought by the control handoff procedure, a because local oscillator with a broadband, so that also be simplified on the circuit design, for condition has been created in the miniaturization of radio-frequency front-end; 2. the phase noise of the first local oscillator phase-locked loop output, phase noise by reference frequency in loop bandwidth plays a leading role, take as the leading factor with the phase noise of voltage controlled oscillator beyond the loop bandwidth, and wideband voltage controlled oscillator phase noise near at hand is not ideal enough, after having improved the first local oscillator phase demodulation frequency, the loop bandwidth design increases, the nearby phase noise of broadband local oscillator reduces the phase noise impact of loop output, thereby so that pll output signal nearby and the phase noise of far-end all be guaranteed, thereby improved the phase noise index of complete machine.
Description of drawings
Fig. 1: several narrow-band local oscillations consist of the theory diagram of the first local oscillator;
Fig. 2: utilize broadband local oscillator and high frequency phase demodulation to realize the theory diagram of down-conversion.
Embodiment
The below is described in more detail the present invention.
As shown in Figure 2, utilize broadband local oscillator and high frequency phase demodulation to realize the system of frequency spectrograph down-conversion, comprise the first filter, the first frequency mixer, the first local oscillator, the second frequency mixer, the second filter, the second local oscillator, three-mixer, the 3rd filter, the 3rd local oscillator, digital intermediate frequency; Described the first filter, the second filter, the 3rd filter are low pass filter.
Three grades of local oscillators and three grades of frequency mixers form three grades of down-conversion passages, in order to suppress image frequency, the radiofrequency signal of 9kHz-3000MHz enters behind the radio-frequency front-end passage through the first filter filtering image frequency, deliver to the first frequency mixer and produce the first intermediate frequency with the first local oscillator mixing, the first intermediate frequency is the high intermediate frequency about 4000MHz, deliver to after the filtering of the first intermediate frequency through the second filter the second frequency mixer and with the second local oscillator mixing after produce the second intermediate frequency, deliver to after the second intermediate frequency is processed through the 3rd filter filtering three-mixer and with the 3rd local oscillator mixing after produce the 3rd intermediate frequency, after finishing radio frequency down-conversion, the 3rd intermediate frequency exports Digital IF Processing to and partly finishes corresponding spectrum analysis.
Described the first local oscillator adopts the mode of broadband local oscillator, and adopts the high frequency phase demodulation in the first local oscillator phase-locked loop.
Described the first local oscillator phase-locked loop is comprised of wideband voltage controlled oscillator, frequency divider, high frequency phase discriminator, the reference of high frequency phase demodulation and loop filter; Wideband voltage controlled oscillator through behind the frequency divider frequency division in the high frequency phase discriminator with the high frequency phase demodulation with reference to phase demodulation, error signal through loop filter integration, filtering after output error voltage and feed back to wideband voltage controlled oscillator.
Described wideband voltage controlled oscillator is as the oscillator in the first local oscillator phase-locked loop, owing to adopt the scheme of high intermediate frequency, high intermediate frequency is chosen for about 4000MHz, and the radio-frequency input signals scope is 9kHz-3000MHz, the first local oscillator tuning range is since the first intermediate frequency, continuous tuning covers whole radiofrequency signal input range, does not need to be divided into several sections and finishes covering by switching.Therefore the wideband voltage controlled oscillator in the first local oscillator phase-locked loop covers this scope of 4000MHz to 7000MHz at least, and it is that the wideband voltage controlled oscillator of 4000MHz to 8000MHz is to satisfy condition that the present invention selects hunting range.
The present invention is increased to 100MHz with the high frequency phase discriminator reference frequency in the first local oscillator phase-locked loop, selecting frequency of oscillation is that the OCXO " constant-temperature crystal oscillator " of 100MHz is as the high frequency phase demodulation reference of the first local oscillator phase-locked loop, constant-temperature crystal oscillator has stability height, the good characteristics of phase noise index, position at skew 1KHz, phase noise can reach-more than the 145dBc, in the position of skew 10KHz, phase noise can reach-more than the 155dBc.The first local oscillator phase-locked loop has guaranteed the nearby phase noise index of the first local oscillator output frequency by the high frequency phase demodulation.
The first local oscillator phase-locked loop adopts the phase-locked mode in broadband, because the phase demodulation reference frequency of the first local oscillator cycle of phase-locked loop medium-high frequency phase discriminator is provided by the constant-temperature crystal oscillator of 100MHz, under the condition that phase-locked loop phase demodulation reference frequency is largely increased, prerequisite is provided for the raising of the loop bandwidth of the first local oscillator phase-locked loop, the loop bandwidth that the present invention designs the first local oscillator phase-locked loop is about 200kHz, because very wide as the voltage controlled oscillator tuning range of the first local oscillator, the many volts of tuning voltage scope height to 20, the loop filter of the first local oscillator adopts output voltage range to surpass 20 volts multistage active loop filter, voltage controlled gain in conjunction with voltage controlled oscillator in the loop, the parameters such as high frequency phase discriminator phase demodulation electric current, by the parameter of loop filter is set, the first local oscillator PLL loop bandwidth is set to about 200kHz.Because the phase noise of cycle of phase-locked loop output frequency is mainly determined by the characteristic of making an uproar mutually of high frequency phase demodulation reference in loop bandwidth, and outside loop bandwidth, mainly determined by wideband voltage controlled oscillator, and the selected wideband voltage controlled oscillator of the present invention phase noise of (outside the loop bandwidth) beyond offset carrier 200kHz is fine, therefore, the phase-locked far-end phase noise index that guarantees the first local oscillator output frequency in broadband.
Utilize broadband local oscillator and high frequency phase demodulation, and take the phase-locked mode in broadband, both guaranteed the nearby phase noise of the first local oscillator, guaranteed again the phase noise of far-end, thereby improved the phase noise index of frequency spectrograph complete machine; Under the condition that increases loop bandwidth, shorten the locking time of the first local oscillator cycle of phase-locked loop simultaneously, thereby improved the speed of complete machine.
The output of the first local oscillator phase-locked loop is controlled by the control system based on ARM, be actually the output frequency of recently realizing the first local oscillator by the frequency division of control wideband voltage controlled oscillator in frequency divider, the output frequency of the first local oscillator is the product of frequency dividing ratio and phase demodulation reference frequency, because what adopt is the broadband local oscillator of continuous tuning, the frequency dividing ratio that only needs to change the first local oscillator just can change the output frequency of the first local oscillator, and does not need other control command.
The frequency spectrograph complete machine is being set centre frequency, after the parameters such as scan width, the ARM control system is according to these parameters, again in conjunction with the tuning manner of realizing radio frequency down-conversion, calculate frequency that the first local oscillator should export (according to tuning manner, the first local oscillator output frequency is the frequency after the radio frequency incoming frequency adds the first intermediate frequency), then according to the first local oscillator output frequency and the phase demodulation reference frequency that adopts, calculate the frequency dividing ratio (frequency dividing ratio is namely calculated gained First vibration frequency divided by phase demodulation reference frequency gained) of the first local oscillator, frequency dividing ratio sends to RF front-end module by the control system based on ARM by data/address bus after being converted to binary data, after CPLD in the RF front-end module " programmable logic device " receives the upper strata and sends the serial data of getting off, send the data to again the frequency divider of the first local oscillator.By phase-locked loop control, the first local oscillator phase-locked loop is exported corresponding frequency, and finishes radio frequency down-conversion according to corresponding setting.
The above is the preferred embodiments of the present invention only, is not restricted to the present invention, and for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within the claim scope of the present invention.
Claims (7)
1. a system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion comprises the first filter, the first frequency mixer, the first local oscillator, the second frequency mixer, the second filter, the second local oscillator, three-mixer, the 3rd filter, the 3rd local oscillator, digital intermediate frequency; Radiofrequency signal enters behind the radio-frequency front-end passage through the first filter filtering image frequency, deliver to the first frequency mixer and produce the first intermediate frequency with the first local oscillator mixing, deliver to after the filtering of the first intermediate frequency through the second filter the second frequency mixer and with the second local oscillator mixing after produce the second intermediate frequency, deliver to after the second intermediate frequency is processed through the 3rd filter filtering three-mixer and with the 3rd local oscillator mixing after produce the 3rd intermediate frequency, after finishing radio frequency down-conversion, the 3rd intermediate frequency exports Digital IF Processing to and partly finishes corresponding spectrum analysis, it is characterized in that: described the first local oscillator phase-locked loop is by wideband voltage controlled oscillator, frequency divider, the high frequency phase discriminator, the reference of high frequency phase demodulation and loop filter form; Wideband voltage controlled oscillator through behind the frequency divider frequency division in the high frequency phase discriminator with the high frequency phase demodulation with reference to phase demodulation, error signal through loop filter integration, filtering after output error voltage and feed back to wideband voltage controlled oscillator.
2. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1, it is characterized in that: the high frequency phase demodulation of described the first local oscillator phase-locked loop is with reference to selecting the OCXO constant-temperature crystal oscillator.
3. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1 is characterized in that: the multistage active loop filter of described loop filter employing output voltage range above 20 volts.
4. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1, it is characterized in that: the loop bandwidth of described the first local oscillator phase-locked loop is 200kHz.
5. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1, it is characterized in that: described the first filter, the second filter, the 3rd filter are low pass filter.
6. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1, it is characterized in that: described the first intermediate frequency is the high intermediate frequency of 4000MHz.
7. the system that utilizes broadband local oscillator and high frequency phase demodulation to realize the frequency spectrograph down-conversion according to claim 1, it is characterized in that: the output of described the first local oscillator phase-locked loop is controlled by the control system based on ARM.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201220568779 CN202856715U (en) | 2012-11-01 | 2012-11-01 | System for realizing spectrum analyzer down-conversion with broadband local oscillators and high-frequency phase demodulation |
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| CN 201220568779 CN202856715U (en) | 2012-11-01 | 2012-11-01 | System for realizing spectrum analyzer down-conversion with broadband local oscillators and high-frequency phase demodulation |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102970030A (en) * | 2012-11-01 | 2013-03-13 | 南京国睿安泰信科技股份有限公司 | System for achieving spectrum analyzer down-conversion by using broadband local oscillator and high frequency phase discrimination |
| CN103209004A (en) * | 2013-04-07 | 2013-07-17 | 海能达通信股份有限公司 | Multi-slot transceiver |
| CN108418583A (en) * | 2018-03-20 | 2018-08-17 | 西安电子工程研究所 | The thin stepping frequency agility apparatus for frequency synthesizing in broadband and method based on cascade mixing |
| CN111220847A (en) * | 2019-05-21 | 2020-06-02 | 一诺仪器（中国）有限公司 | Frequency conversion system and spectrum analyzer |
-
2012
- 2012-11-01 CN CN 201220568779 patent/CN202856715U/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102970030A (en) * | 2012-11-01 | 2013-03-13 | 南京国睿安泰信科技股份有限公司 | System for achieving spectrum analyzer down-conversion by using broadband local oscillator and high frequency phase discrimination |
| CN103209004A (en) * | 2013-04-07 | 2013-07-17 | 海能达通信股份有限公司 | Multi-slot transceiver |
| CN103209004B (en) * | 2013-04-07 | 2015-08-12 | 海能达通信股份有限公司 | A kind of multi-time slot transceiver |
| CN108418583A (en) * | 2018-03-20 | 2018-08-17 | 西安电子工程研究所 | The thin stepping frequency agility apparatus for frequency synthesizing in broadband and method based on cascade mixing |
| CN108418583B (en) * | 2018-03-20 | 2021-07-16 | 西安电子工程研究所 | Broadband fine stepping frequency agility frequency synthesis device and method based on cascade frequency mixing |
| CN111220847A (en) * | 2019-05-21 | 2020-06-02 | 一诺仪器（中国）有限公司 | Frequency conversion system and spectrum analyzer |
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