技术领域technical field
本发明涉及频谱分析仪技术领域，特别涉及一种频谱分析仪的校准方法。The invention relates to the technical field of spectrum analyzers, in particular to a calibration method for a spectrum analyzer.
背景技术Background technique
频谱分析仪是一种用来对被测信号进行频谱分析的接收机，可以测量未知信号的频率、幅值、失真等相关参数，通常具有很宽的频率和幅值测量范围。主要应用于基站维护、电子产品研发、生产等领域。频谱分析仪又可称为频域示波器、跟踪示波器、分析示波器、谐波分析器、频率特性分析仪或傅里叶分析仪等。频谱分析仪的主要技术指标有频率范围、分辨力、扫频速度、灵敏度、显示方式和假响应、幅度精度等。A spectrum analyzer is a receiver used to perform spectrum analysis on the signal under test. It can measure the frequency, amplitude, distortion and other related parameters of unknown signals, and usually has a wide frequency and amplitude measurement range. Mainly used in base station maintenance, electronic product research and development, production and other fields. Spectrum analyzers can also be called frequency domain oscilloscopes, tracking oscilloscopes, analytical oscilloscopes, harmonic analyzers, frequency characteristic analyzers or Fourier analyzers. The main technical indicators of the spectrum analyzer include frequency range, resolution, sweep speed, sensitivity, display mode, false response, amplitude accuracy, etc.
如图1所示，为传统的频谱分析仪的工作原理图。输入射频信号经过多次变频将频率较高的信号改变为数字中频模块可处理的低频信号。由于是多次混频，所以必然要求提供多个本振信号。在这一转变过程中，由于混频器本身的特性决定，会产生无用边频及非线性杂散等，为了保证信号频谱的纯度，就需要用滤波器将不需要的信号滤除。As shown in Figure 1, it is a working principle diagram of a traditional spectrum analyzer. The input radio frequency signal undergoes multiple frequency conversions to change the higher frequency signal into a low frequency signal that can be processed by the digital intermediate frequency module. Because of multiple frequency mixing, it is necessary to provide multiple local oscillator signals. In this conversion process, due to the characteristics of the mixer itself, unwanted side frequencies and nonlinear spurs will be generated. In order to ensure the purity of the signal spectrum, it is necessary to use a filter to filter out unnecessary signals.
如图2所示，改进型频谱分析仪的工作原理图。频谱分析仪100采用超外差式结构，对通过射频前端模块101引入的输入信号、中频通道模块102对其进行多次变频，使之变成中频信号，然后送至包含ADC采样单元、数字中频滤波器单元、检波器单元，控制单元及显示器单元的显示模块103进行输出和显示。在射频前端模块101中，被测信号从输入端口进入，用单刀双掷开关1来选通前端链路104或者选通功率负载2，单刀双掷开关1有可能要承受较大功率，因此经常采用大功率单刀双掷开关或继电器来构成。单刀双掷开关4用于选通将被测信号输入前端链路104还是将校准信号输出单元3接入前端链路104从而进行自校准，校准信号输出单元3通常由频谱分析仪100的内部电路产生。单刀双掷开关5与单刀双掷开关7共同配合选通固定衰减器6是否接入前端链路104。固定衰减器6可以承受较大的输入功率，当用频谱分析仪100测量较大功率的信号时，为了保证混频器13工作在线性区域，需要先将输入信号进行衰减；固定衰减器6通常具有较高的压缩点，以确保到达混频器13的被测信号不会被压缩。步进衰减器8是一个衰减量可调的衰减器，而且具有较宽的衰减范围，可将输入的被测信号继续衰减至混频器13的最佳混频电平。单刀双掷开关9和单刀双掷开关11共同配合选通前置放大器10，前置放大器10用于小信号的测量，当被测量的信号幅值比较小且接近频谱分析仪100的低噪时，打开前置放大器10，将减小前端链路104的噪声系数，即降低了噪声，这样小信号可以被准确的测量。滤波器12是一个低通滤波器，其作用是对混频器13的镜像频率进行抑制。As shown in Figure 2, the working principle diagram of the improved spectrum analyzer. The spectrum analyzer 100 adopts a superheterodyne structure. The input signal introduced through the radio frequency front-end module 101 and the intermediate frequency channel module 102 perform multiple frequency conversions to make it into an intermediate frequency signal, and then send it to a signal containing an ADC sampling unit, a digital intermediate frequency The filter unit, the wave detector unit, the control unit and the display module 103 of the display unit perform output and display. In the radio frequency front-end module 101, the signal to be measured enters from the input port, and the front-end link 104 or the power load 2 is selected by using the single-pole double-throw switch 1. The single-pole double-throw switch 1 may have to bear relatively large power, so often It is composed of high-power single-pole double-throw switch or relay. The SPDT switch 4 is used to select whether the signal under test is input to the front-end link 104 or the calibration signal output unit 3 is connected to the front-end link 104 to perform self-calibration. The calibration signal output unit 3 is usually controlled by the internal circuit of the spectrum analyzer 100 produce. The SPDT switch 5 cooperates with the SPDT switch 7 to select whether the fixed attenuator 6 is connected to the front-end link 104 . The fixed attenuator 6 can withstand relatively large input power. When using the spectrum analyzer 100 to measure a relatively high-power signal, in order to ensure that the mixer 13 works in the linear region, the input signal needs to be attenuated first; the fixed attenuator 6 usually It has a higher compression point to ensure that the signal under test reaching the mixer 13 will not be compressed. The step attenuator 8 is an attenuator with adjustable attenuation, and has a wide attenuation range, which can continuously attenuate the input signal under test to the optimum mixing level of the mixer 13 . The single pole double throw switch 9 and the single pole double throw switch 11 cooperate with the gating preamplifier 10, the preamplifier 10 is used for the measurement of small signals, when the signal amplitude to be measured is relatively small and close to the low noise of the spectrum analyzer 100 , turning on the preamplifier 10 will reduce the noise figure of the front-end chain 104, that is, reduce the noise, so that small signals can be accurately measured. Filter 12 is a low-pass filter whose function is to suppress the image frequency of mixer 13 .
该方案的校准方法是频谱分析仪100对点频的校准信号进行测量，将其通过测量得到的校准信号的幅值与校准信号的实际幅值做差值，显示模块203中的控制单元将所述差值保存起来，在频谱分析仪100以后的测量结果中，自动加上该差值，以减少测量结果的误差。The calibration method of this scheme is that the spectrum analyzer 100 measures the calibration signal of the point frequency, and makes a difference between the amplitude of the calibration signal obtained by the measurement and the actual amplitude of the calibration signal, and the control unit in the display module 203 converts the The above-mentioned difference is saved, and the difference is automatically added to the measurement results after the spectrum analyzer 100, so as to reduce the error of the measurement results.
从显示模块103中的数字中频滤波单元后处理的信号是有一定带宽的，信号带宽等于当前设置RBW(分辨率滤波器带宽)，而现有方案的校准方法并不能对中频通道模块电路在RBW带宽内引入的频率响应进行校准，因此中频通道模块电路引入的频率响应平坦度会影响测试信号幅度的准确性(3dB带宽内)，设备幅度测试准确度降低。The post-processed signal from the digital intermediate frequency filter unit in the display module 103 has a certain bandwidth, and the signal bandwidth is equal to the current setting RBW (resolution filter bandwidth), and the calibration method of the existing solution cannot correct the intermediate frequency channel module circuit in the RBW. The frequency response introduced in the bandwidth is calibrated, so the flatness of the frequency response introduced by the IF channel module circuit will affect the accuracy of the test signal amplitude (within the 3dB bandwidth), and the accuracy of the equipment amplitude test will be reduced.
频谱分析仪100的中频通道模块中的模拟中频滤波器带宽须大于频谱分析仪的最大可设RBW，如1MHz。经过显示模块103中ADC采样、数字中频滤波处理后的信号带宽等于当前设置的RBW带宽。因为数字中频处理的信号并不是理想的单频点信号，而是带宽为RBW的信号，现有方案校准只进行单点校准，并没有考虑中频通道电路在信号带宽内的频率响应平坦度，测得的信号峰值准确度比较高，但是3dB带宽内的幅度与实际值误差可能会较大，无法校准。The bandwidth of the analog IF filter in the IF channel module of the spectrum analyzer 100 must be greater than the maximum settable RBW of the spectrum analyzer, such as 1 MHz. The signal bandwidth after being sampled by the ADC in the display module 103 and processed by digital intermediate frequency filtering is equal to the currently set RBW bandwidth. Because the signal processed by the digital IF is not an ideal single-frequency point signal, but a signal with a bandwidth of RBW, the existing scheme calibration only performs single-point calibration, and does not consider the frequency response flatness of the IF channel circuit within the signal bandwidth. The peak accuracy of the obtained signal is relatively high, but the error between the amplitude and the actual value within the 3dB bandwidth may be large, which cannot be calibrated.
实时频谱分析仪是同时采样分析带宽内的信号，分析带宽通常较宽，分析带宽内中频通道的频率响应平坦度对测试的准确性影响是无法忽略的，若应用现有方案的校准方法，校准信号须是带宽等于分析带宽的宽带信号。为了完成校准，需要增加宽带信号产生电路作为校准信号源，增加了电路成本，且保证全工作温度范围内宽带校准信号幅度精度高，实现难度也比较大。The real-time spectrum analyzer samples the signals within the analysis bandwidth at the same time. The analysis bandwidth is usually wide. The impact of the frequency response flatness of the IF channel within the analysis bandwidth on the accuracy of the test cannot be ignored. If the calibration method of the existing scheme is used, the calibration The signal shall be a broadband signal with a bandwidth equal to the analysis bandwidth. In order to complete the calibration, it is necessary to add a broadband signal generating circuit as a calibration signal source, which increases the circuit cost, and ensures high accuracy of the broadband calibration signal amplitude within the full operating temperature range, which is also relatively difficult to implement.
发明内容Contents of the invention
为解决现有技术的问题，本发明提出一种频谱分析仪的校准方法，在现有方案电路的基础上可以不增加额外电路就能实现对中频通道电路的带内频率响应进行校准，减小中频通道电路的带内频率响应对幅度测量的影响。In order to solve the problems of the prior art, the present invention proposes a calibration method of a spectrum analyzer, which can realize the calibration of the in-band frequency response of the intermediate frequency channel circuit without adding additional circuits on the basis of the existing scheme circuit, reducing The effect of the in-band frequency response of the IF channel circuit on the magnitude measurement.
为实现上述目的，本发明提供了一种频谱分析仪的校准方法，包括：To achieve the above object, the invention provides a calibration method for a spectrum analyzer, comprising:
确定中频通道电路需校准的频率点；Determine the frequency point to be calibrated for the intermediate frequency channel circuit;
利用每个校准频率点对应的频率，确定每个校准频率点对应的第一本振信号的扫频频率和数控振荡器的扫频频率；Using the frequency corresponding to each calibration frequency point, determine the sweep frequency of the first local oscillator signal and the sweep frequency of the digitally controlled oscillator corresponding to each calibration frequency point;
每一次校准时，根据每个校准频率点对应的第一本振信号的扫频频率和所述频谱分析仪的数控振荡器的扫频频率，设置第一本振的工作频率和数控振荡器的工作频率；During each calibration, according to the sweep frequency of the first local oscillator signal corresponding to each calibration frequency point and the sweep frequency of the numerically controlled oscillator of the spectrum analyzer, the operating frequency of the first local oscillator and the numerically controlled oscillator are set. working frequency;
每个校准频率点对应的校准信号依此经过射频前端、中频通道电路、采样之后，输入至所述数控振荡器，经所述数控振荡器混频处理，将每个校准信号变频成零中频信号；The calibration signal corresponding to each calibration frequency point passes through the RF front-end, the intermediate frequency channel circuit, and the sampling, and then is input to the numerically controlled oscillator. After being mixed by the numerically controlled oscillator, each calibration signal is frequency-converted into a zero-IF signal. ;
所述频谱分析仪利用每个校准信号对应的零中频信号获得相应校准信号的测量幅度；The spectrum analyzer utilizes the zero-IF signal corresponding to each calibration signal to obtain the measurement amplitude of the corresponding calibration signal;
每个校准信号的测量幅度与实际幅度比较，获得每个校准信号的差值，该差值为中频通道电路在对应频率点的频率响应；The measured amplitude of each calibration signal is compared with the actual amplitude to obtain the difference of each calibration signal, which is the frequency response of the intermediate frequency channel circuit at the corresponding frequency point;
利用中频通道电路在对应频率点的频率响应实现频谱分析仪的校准。The frequency response of the intermediate frequency channel circuit at the corresponding frequency point is used to calibrate the spectrum analyzer.
优选地，所述数控振荡器的扫频频率与所述中频通道电路输出的中频信号的频率相等。Preferably, the sweep frequency of the numerically controlled oscillator is equal to the frequency of the intermediate frequency signal output by the intermediate frequency channel circuit.
上述技术方案具有如下有益效果：本技术方案简单易实现，且不额外增加电路成本，用以校准中频通道电路分析带宽内的频率响应，以减小其对幅度测量准确度的影响。The above-mentioned technical solution has the following beneficial effects: the technical solution is simple and easy to implement without additional circuit cost, and is used to calibrate the frequency response within the analysis bandwidth of the intermediate frequency channel circuit to reduce its impact on the accuracy of amplitude measurement.
附图说明Description of drawings
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.
图1为传统的频谱分析仪的工作原理图；Fig. 1 is the working principle diagram of traditional spectrum analyzer;
图2为改进型频谱分析仪的工作原理图；Fig. 2 is the working principle diagram of the improved spectrum analyzer;
图3为本发明提出的一种频谱分析仪的校准方法流程图；Fig. 3 is the calibration method flow chart of a kind of spectrum analyzer that the present invention proposes;
图4为本实施例需要校准的频谱分析仪的电路图。FIG. 4 is a circuit diagram of a spectrum analyzer to be calibrated in this embodiment.
具体实施方式detailed description
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.
本技术方案的工作原理：现有技术通常采用宽带信号作为校准信号的方法，需要增加宽带信号产生电路，增加了电路成本，占用PCB面积也会相应增加，且幅度精准的宽带信号产生电路实现难度也是比较大的。基于此，本技术方案为了校准中频通道的宽带频率响应，没有增加一个宽带的校准信号产生电路，当进行校准时，校准信号不变，第一本振频率和数振荡器频率同步变化，可测试得到校准信号变频至中频通道带内任意位置后进行采样处理的幅度，与校准信号实际幅度值比较得到的差值，保存下来，作为输出该中频频率时中频通道频率响应的校准数据。频谱分析仪进行测量时，自动加上相应的差值。实现频谱分析仪的校准，不需要为了配合校准增加额外的电路。The working principle of this technical solution: in the prior art, broadband signals are usually used as the method of calibrating signals, and it is necessary to increase the broadband signal generation circuit, which increases the circuit cost, and the occupied PCB area will increase accordingly, and it is difficult to realize the broadband signal generation circuit with accurate amplitude. It is also relatively large. Based on this, in order to calibrate the broadband frequency response of the intermediate frequency channel, this technical solution does not add a broadband calibration signal generation circuit. When performing calibration, the calibration signal remains unchanged, and the first local oscillator frequency and the digital oscillator frequency change synchronously, which can be tested The amplitude obtained after the calibration signal is converted to any position in the intermediate frequency channel band for sampling processing, and the difference obtained by comparing the actual amplitude value of the calibration signal is saved as the calibration data of the frequency response of the intermediate frequency channel when the intermediate frequency frequency is output. When the spectrum analyzer is measuring, it will automatically add the corresponding difference. To realize the calibration of the spectrum analyzer, no additional circuits are needed to cooperate with the calibration.
基于上述工作原理，本发明提出一种频谱分析仪的校准方法，如图3所示。包括：Based on the above working principle, the present invention proposes a calibration method for a spectrum analyzer, as shown in FIG. 3 . include:
步骤301)确定中频通道电路需校准的频率点；Step 301) Determine the frequency point to be calibrated for the intermediate frequency channel circuit;
步骤302)：利用每个校准频率点对应的频率，确定每个校准频率点对应的第一本振信号的扫频频率和数控振荡器的扫频频率；其中，所述数控振荡器的扫频频率与所述中频通道电路输出的中频信号的频率相等。Step 302): Using the frequency corresponding to each calibration frequency point, determine the sweep frequency of the first local oscillator signal corresponding to each calibration frequency point and the sweep frequency of the numerically controlled oscillator; wherein, the sweep frequency of the numerically controlled oscillator The frequency is equal to the frequency of the intermediate frequency signal output by the intermediate frequency channel circuit.
步骤303)：每一次校准时，根据每个校准频率点对应的第一本振信号的扫频频率和所述频谱分析仪的数控振荡器的扫频频率，设置第一本振的工作频率和数控振荡器的工作频率；Step 303): During each calibration, according to the sweep frequency of the first local oscillator signal corresponding to each calibration frequency point and the sweep frequency of the digitally controlled oscillator of the spectrum analyzer, the operating frequency and The operating frequency of the numerically controlled oscillator;
步骤304)：每个校准频率点对应的校准信号依此经过射频前端、中频通道电路、采样之后，输入至所述数控振荡器，经所述数控振荡器混频处理，将每个校准信号变频成零中频信号；Step 304): The calibration signal corresponding to each calibration frequency point passes through the RF front-end, the intermediate frequency channel circuit, and is sampled accordingly, and then input to the numerically controlled oscillator, and undergoes frequency mixing processing by the numerically controlled oscillator to convert the frequency of each calibration signal into a zero-IF signal;
步骤305)：所述频谱分析仪利用每个校准信号对应的零中频信号获得相应校准信号的测量幅度；Step 305): The spectrum analyzer uses the zero-IF signal corresponding to each calibration signal to obtain the measurement amplitude of the corresponding calibration signal;
步骤306)：每个校准信号的测量幅度与实际幅度比较，获得每个校准信号的差值，该差值为中频通道电路在对应频率点的频率响应；Step 306): The measured amplitude of each calibration signal is compared with the actual amplitude to obtain the difference of each calibration signal, which is the frequency response of the intermediate frequency channel circuit at the corresponding frequency point;
步骤307)：利用中频通道电路在对应频率点的频率响应实现频谱分析仪的校准。Step 307): Using the frequency response of the IF channel circuit at the corresponding frequency point to calibrate the spectrum analyzer.
如图4所示，为本实施例需要校准的频谱分析仪的电路图。是实时频谱分析仪的电路结构，设备实时分析带宽为10MHz。As shown in FIG. 4 , it is a circuit diagram of a spectrum analyzer to be calibrated in this embodiment. It is the circuit structure of the real-time spectrum analyzer, and the real-time analysis bandwidth of the device is 10MHz.
被测信号频率范围为9kHz至3.2GHz，从设备输入端输入至射频前端电路，射频前端电路根据设置的参考电平对输入信号进行相应的幅度调整及滤波，以提供给第一混频器合适的输入幅度及滤除输入信号中的镜像频率成分；射频前端模块输出的信号与第一本振信号4GHz至7.2GHz混频，并经过第一中频放大器，第一中频滤波器，得到第一中频信号3995MHz至4005MHz。The frequency range of the signal to be tested is 9kHz to 3.2GHz, and it is input from the input terminal of the device to the RF front-end circuit. The RF front-end circuit adjusts and filters the input signal according to the set reference level, so as to provide a suitable signal for the first mixer. The input amplitude of the input signal and the image frequency component in the filtered input signal; the signal output by the RF front-end module is mixed with the first local oscillator signal 4GHz to 7.2GHz, and passed through the first intermediate frequency amplifier and the first intermediate frequency filter to obtain the first intermediate frequency Signal 3995MHz to 4005MHz.
第二混频器将第一中频滤波器输出的第一中频信号与第二本振混频，输出的信号经过第二中频放大器、第二中频滤波器进行幅度调整和滤波；第三混频器将第二中频滤波器输出的第二中频信号与第三本振混频，输出的信号经过第三中频放大器、第三中频滤波器进行幅度调整和滤波，得到频率范围为95MHz至105MHz的第三中频信号。The second mixer mixes the first intermediate frequency signal output by the first intermediate frequency filter with the second local oscillator, and the output signal is subjected to amplitude adjustment and filtering through the second intermediate frequency amplifier and the second intermediate frequency filter; the third mixer The second intermediate frequency signal output by the second intermediate frequency filter is mixed with the third local oscillator, and the output signal is adjusted and filtered through the third intermediate frequency amplifier and the third intermediate frequency filter to obtain the third intermediate frequency signal with a frequency range of 95MHz to 105MHz. IF signal.
第三中频信号输入至数字处理模块进行数字处理。数字处理模块主要包括ADC采样单元，数字下变频、数字处理，数字处理后的信号输出至显示屏显示。ADC采样单元主要作用是将第三中频信号数字化；数字下变频是将第三中频信号与数字振荡器输出的100MHz信号混频，将第三中频信号转换为基带信号；数字处理模块对基带信号经过滤波、检波等一系列处理。数字下变频、数控振荡器及数字处理模块用FPGA等器件实现。The third intermediate frequency signal is input to the digital processing module for digital processing. The digital processing module mainly includes ADC sampling unit, digital down-conversion, digital processing, and the digitally processed signal is output to the display screen for display. The main function of the ADC sampling unit is to digitize the third intermediate frequency signal; digital down-conversion is to mix the third intermediate frequency signal with the 100MHz signal output by the digital oscillator, and convert the third intermediate frequency signal into a baseband signal; the digital processing module processes the baseband signal A series of processing such as filtering and detection. The digital down-conversion, numerical control oscillator and digital processing module are implemented with devices such as FPGA.
设备设置为测量模式时，各处频率配置如下。假设输入频率为45至55MHz时，当前第一本振频率为4050MHz点频，经过第一混频、第一中频放大、滤波得到的第一中频信号为3995MHz至4005MHz，经过后级第二混频、放大、滤波及第三混频、放大、滤波得到的第三中频信号为95MHz至105MHz，该信号经过ADC采样后与数控振荡器输出的100MHz点频信号混频，得到基带信号，供后级数字处理、显示。When the device is set to measurement mode, the frequency configurations are as follows. Assume that when the input frequency is 45 to 55MHz, the current first local oscillator frequency is 4050MHz point frequency, and the first intermediate frequency signal obtained after the first mixing, first intermediate frequency amplification and filtering is 3995MHz to 4005MHz, after the second mixing in the subsequent stage , amplification, filtering, and third frequency mixing, amplification, and filtering to obtain a third intermediate frequency signal of 95MHz to 105MHz, which is sampled by the ADC and mixed with the 100MHz point frequency signal output by the numerically controlled oscillator to obtain a baseband signal for the subsequent stage Digital processing, display.
在校准时，设备提供基准校准信号为50MHz点频，当进行设备自校准时，校准信号50MHz经过射频前端，输入至第一混频器，当前第一本振设置为4045MHz至4055MHz范围内变化，经过中频通道模块传输后得到95MHz至105MHz的第三中频信号，数控振荡器输出的频率为95MHz至105MHz范围内变化，数控振荡器输出的频率改变与第一本振的频率改变配合，实现经过数字下变频后输出零中频信号，再进行后级数字处理。During calibration, the device provides a reference calibration signal with a point frequency of 50MHz. When the device is self-calibrating, the calibration signal 50MHz passes through the RF front end and is input to the first mixer. The current first local oscillator is set to change within the range of 4045MHz to 4055MHz. After being transmitted by the intermediate frequency channel module, the third intermediate frequency signal from 95MHz to 105MHz is obtained. The output frequency of the numerical control oscillator changes within the range of 95MHz to 105MHz. Output zero-IF signal after down-conversion, and then perform post-stage digital processing.
进一步详细说明为：It is further detailed as:
步骤1)：校准信号50MHz点频信号经过射频前端，输入至第一混频器，当前第一本振设置为4045MHz，第一中频信号为3995MHz，经过第二混频、放大、滤波及第三混频、放大、滤波后，第三中频信号频率为95MHz，与数控振荡器输出的95MHz信号混频得到零中频信号，经过后级数字处理后，得到50MHz校准信号由频谱分析仪测得的幅度，该幅度与50MHz校准信号的实际幅度比较，得到的差值即为中频通道模块输出为95MHz时对应的中频通道电路引入的频率响应；Step 1): The calibration signal 50MHz point frequency signal passes through the RF front end and is input to the first mixer. The current first local oscillator is set to 4045MHz, and the first intermediate frequency signal is 3995MHz. After the second mixing, amplification, filtering and third After frequency mixing, amplification and filtering, the frequency of the third intermediate frequency signal is 95MHz, which is mixed with the 95MHz signal output by the numerically controlled oscillator to obtain a zero intermediate frequency signal. After digital processing in the subsequent stage, the amplitude of the 50MHz calibration signal measured by the spectrum analyzer is obtained , the amplitude is compared with the actual amplitude of the 50MHz calibration signal, and the difference obtained is the frequency response introduced by the corresponding intermediate frequency channel circuit when the output of the intermediate frequency channel module is 95MHz;
步骤2)：将第一本振频率和数控振荡器频率都相应改变，重复步骤1；Step 2): Change the frequency of the first local oscillator and the frequency of the digitally controlled oscillator accordingly, and repeat step 1;
步骤3)：根据幅度精度要求确定中频通道电路需校准的频率点，对每个校准频率点重复步骤2。其中，如需校准中频通道输出102MHz时，即第一本振信号设置为4052MHz，数控振荡器频率设置为102MHz。Step 3): Determine the frequency points to be calibrated for the intermediate frequency channel circuit according to the amplitude accuracy requirements, and repeat step 2 for each calibration frequency point. Among them, if it is necessary to calibrate the IF channel to output 102MHz, that is, the first local oscillator signal is set to 4052MHz, and the frequency of the numerically controlled oscillator is set to 102MHz.
步骤4)：将得到的差值都保存下来，即为中频通道输出为95MHz至105MHz时，中频通道电路引入的频率响应。测量时将测量结果自动加上该差值，即可减小中频通道电路的频率响应对测量幅度准确度的影响，提高测量精度。Step 4): Save all the obtained differences, that is, the frequency response introduced by the intermediate frequency channel circuit when the output of the intermediate frequency channel is 95 MHz to 105 MHz. The difference is automatically added to the measurement result during measurement, which can reduce the influence of the frequency response of the intermediate frequency channel circuit on the accuracy of the measurement range and improve the measurement accuracy.
由上述实施例克制，本技术方案可以不增加额外电路就能实现对中频通道电路的带内频率响应进行校准，减小中频通道电路的带内频率响应对幅度测量的影响。Restrained by the above embodiments, the technical solution can realize the calibration of the in-band frequency response of the intermediate frequency channel circuit without adding additional circuits, and reduce the influence of the in-band frequency response of the intermediate frequency channel circuit on the amplitude measurement.
以上所述的具体实施方式，对本发明的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上所述仅为本发明的具体实施方式而已，并不用于限定本发明的保护范围，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.
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| CN201510932750.7AActiveCN106886002B (en) | 2015-12-15 | 2015-12-15 | Calibration method of spectrum analyzer |
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