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Questions tagged [spectrum-analyzer]

Spectrum analyzers display the amplitude of an input signal versus frequency. Typically the frequency extends along the X-axis and the amplitude extends up the Y-axis of the display. They are used to measure the spectrum of an unknown signal within the frequency range of the particular analyzer being used. Sometimes their name is prefixed by the broad frequency range they cover, hence terms such as Audio / RF / Optical spectrum analyzer.

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32 views

Total thermal noise of a photodetector connected to a spectrum analyzer

I connected a photodetector to a spectrum analyzer (SA) and observed the signal (i.e. noise) on the SA when there is no light hitting the detector. I noticed that when I set a low spectral resolution ...
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43 views

Spectrum Analyzer Sweep Times Sub 1-ms vs. EMI Test Receivers?

I've got a Rigol DSA 832 and I have a client design that sends out a 1ms message every 100ms. The original protocol was a 1ms message every 6 seconds, which was darn near impossible to capture on ...
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46 views

Spurious signals around LO feedthrough in HP 8591A spectrum analyzer?

I am troubleshooting my HP 8591A spectrum analyzer. It is fully functioning, except for these spurious signals around the 0 Hz feedthrough. This noise is only within 15 MHz of DC. Where should I look ...
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74 views

Spectrum Analysis

I am working on a project where I need to measure the power density in milliwatts per centimeter squared (mW/cm²) from several different transmitting smart phone models. But the spectrum analyzer I ...
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41 views

What is the difference between residual phase noise and absolute phase noise?

Studying the characteristics of an oscillator with a phase noise analyzer, but I don't quite understand the difference between absolute and residual noise. Any help would be greatly appreciated
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How can I safely measure the output power of an RFID reader?

I want to measure the output power of a UHF RFID reader. I connected the antenna cable to one of the antenna ports of the RFID reader and to a spectrum analyzer (Hewlett Packard 8568B). There is a 10 ...
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58 views

How do I compute the average power from the PSD plot attached?

I want to calculate the average Power from the Power spectral density plot I have here. Any help would be greatly appreciated.
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21 views

I don't know why my attenuation setting changed

I have a question about the change in my attenuation setting. I have a spectrum analyzer. In one measurement the main harmonic is measured to be 342.28 mV and its reference level is 355 mV. The ...
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496 views

resolution bandwidth

I have the following trivial question: I have acquired a noise spectrum with a resolution bandwidth of \$124\mathrm{Hz}\$. I would like to convert it to \$\mathrm{V/\sqrt{Hz}}\$. Shall I simply ...
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117 views

Two details about phase noise have been confusing me for a long time. Hope to be resolved

Just like FLOYD M. GARDNER said in the PhaseLock Techniques, 3rd Edition: "In light of that success in spectrum analyzers, a practitioner’s answer to the question above is: The spectrum of phase noise ...
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1answer
59 views

Can I connect transmitter output to spectrum analyser input directly?

I have a spectrum analyser, that tolerates 30 dBm 50VDC signal on its input and has internal selectable attenuator up to 40 dB. Can I connect it directly (i. e. without any external attenuators) to ...
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152 views

Link between phase noise and linewidth for a oscillator?

I was googling for a formula to transform the dbc/Hz value given in data sheets for VNA, spectrum analyzers and VCO is often given in dBc/Hz with offset. Now looking up research papers about future ...
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85 views

Incoherence between oscilloscope and spectrum analyser

There seems to be an incoherence between what I see with my oscilloscope, and what I see with my spectrum analyser. I have a signal of about 1MHz (if I'm not wrong), 5mV, from an antenna, through ...
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76 views

Measurements using spectrum analyzer

I need to measure the following characteristics of a frequency synthesizer using a spectrum analyzer: Frequency range: 2.286 GHz to 2.346 GHz Output power: -2.5 dBm to 2.5 dBm SSB phase noise: ...
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1answer
148 views

THAT4315 audio analyzer - capacitors getting hot

I have designed a audio spectrum analyzer circuit with THAT4315 and a drivers for IN-13 bar graph nixie tube to visualize the signal level. To supply +-12V to the opamps, the Meanwell NSD15 module is ...
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74 views

NFC spectrum analysis, weird frequencies showing

I apologize for the picture quality, I did not have an opportunity to export the screenshots. I have a problem properly interpreting this signal. The subcarrier peak is visible but the data seems to ...
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53 views

Question related to two closely separated signals that need to be analyzed by a spectrum analyzer

Question The settings of a spectrum analyzer are given as following: Center Frequency = 1.89 GHz, RBW = 10 kHz, VBW = 10 kHz and Span = 50MHz. The Reference Level is set to -20 dBm and ...
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1answer
56 views

R&S Spectrum Analyzer Voltage Measurement Error

I just got FPC1000 spectrum analyzer that goes from 5 kHz to 1 GHz. I didn't had any spectrum analyzer experiences before this one so everything is very new to me. Among few things that I don't ...
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41 views

Dynamic range given the THD [Spectrum Analyzer]

Imagine that I have to measure the THD with an error less than 6%, given the first 40 harmonics. How do I know the dynamic range of the spectrum analyzer that I have to use?
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1answer
258 views

How to measure a 100 ohm differential signal on a spectrum analyzer?

I have a pair of 1.5V PCML differential signals coming out of an Altera Cyclone V GX FPGA, terminated on the FPGA in 100 ohms with common mode voltage = 0.65V (also provided on the chip). I need to ...
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61 views

Spectral analysis of spectrum analyzer

Using measures from a spectral analyzer, I am a bit confused on how to properly compare the power of each spectral line with the fourier coefficients (Parseval). Take this signal: Take it's spectrum:...
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656 views

Using a Spectrum Analyzer to measure VSWR

I need to measure the VSWR of a coaxial wire that has a length of 100 metres and a characteristic impedance of 50 ohms using a Spectrum Analyzer (I don't have a Network Analyzer). I found this website:...
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54 views

How to test an RF crystal oscillator performance integrated into a Cellular radio?

I have a couple of reference designs with 2 different crystal oscillators integrated into it. These are cellular radio and can generate standard LTE QAM signals out of it. But I do not have access to ...
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133 views

calibrating vector network analyzer with \$75\Omega \$ coax

I am new to electronics and I just began to use a vector notwork analyzer for some measurements. I calibrated my vector network analyzer with both ports connected to 50\$ \Omega \$ coax cables with ...
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631 views

How do I measure very low frequency noise?

I'd like to measure low-level noise in the 1 Hz to 100 kHz range, for example at the output of a LDO. For higher frequencies a spectrum analyzer would do the job, but most only go down to the MHz ...
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97 views

Is it not recommendable to use a spectrum analyzer in its limit frequencies?

Suppose we have a spectrum analyzer whose range of frequencies goes from \$x \ \mathrm{Hz}\$ to \$y \ \mathrm{Hz}\$. Is there any problem that could arise from measuring signals that are near those ...
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64 views

Harmonic mixing in spectrum analyzers

I'm having a pretty difficult time understanding how tuning works when using harmonics in spectrum analyzers. I'm reading about the topic from Keysight's AN 150. Question 1 The following plot is ...
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100 views

How do multiple mixing stages work in a spectrum analyzer?

I'm reading about spectrum analyzers from Keysight's AN 150. On page 12 they explain how multiple mixing stages are used to obtain narrower IF filters. The block diagram offered is the following one: ...
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83 views

Phase noise in spectrum analyzers

I'm reading about spectrum analyzers from Keysight's AN 150 and I have two questions regarding phase noise. The AN states: No oscillator is perfectly stable. Even though we may not be able to see ...
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Why do spectrum analyzers use envelope detectors?

Spectrum analyzers can usually be represented by the following block diagram: Before entering the video filter, the signal passes through an envelope detector. What I don't understand is why this is ...
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67 views

What is difference between channel power and normal power plotted by a spectrum analyzer?

I want to measure the power received by an antenna from an energy source by plugging the antenna to a spectrum analyzer (SA). What makes me confused is that there are different kinds of power that I ...
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1answer
126 views

S-Parameters math confusion

S11 for marker 1 says -47.661 dB Two Questions 1st ..... What is | S11 | ^ 2 2nd Is this accurate ? g = 20 log_10(-47.661) dB
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1k views

How does tuning in a spectrum analyzer actually work?

I have a pretty basic doubt about how tuning works in spectrum analyzers. I'm reading about the topic from Keysight's AN 150. The problem arises in this paragraph in page 11: We need to pick an ...
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469 views

Why is this the maximum dynamic range in a spectrum analyzer?

In Keysight's popular AN 150 there is a plot of noise and harmonics amplitudes versus the level of the input signal at the mixer (page 57). It's stated there that the maximum n-th dynamic range is ...
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non-negative FFT spectrum, subtlety

definations \$x(t)\$ is a function of time. Physically, it can be voltage, displacement, magnetization and so on. It can be real, complex, vectors or more fancy numbers. \$C(t)\$ is the auto ...
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whats the difference between a cascaded band pass filter and a normal band pass filter (Audio visualizer)

simulate this circuit – Schematic created using CircuitLab currently im building an audio visualizer i would like to know what is the difference between a cascaded 2nd order band pass filter ...
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1answer
176 views

How to calculate noise power (dBm) of a photodiode?

I want to check the thermal noise spectrum of a photodiode (PD) at different frequency response but I do not know how to calculate it. Below graph is an example which shows noise power (dBm) as a ...
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1answer
51 views

Observing sawtooth spectrum

I have measured the output of a triangle wave using a spectrum analyser. This is controlled via digital, but oscillates completely by analogue circuitry. It is from the design of a music synth. I am ...
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2answers
212 views

Why do square waves have this spectrum response?

Below shows my makeshift spectrum analyser, where a 2V, 66Hz square wave on the input. Why do square have have this response (where every harmonic has some amplitude attached to it)? I read somewhere ...
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Audio spectrum analysis: PC Software vs Hardware Spectrum Analyzer

I need to do some audio spectrum analysis (basically, listening to a machine and tell if it is properly calibrated). I will record the sound it makes with a microphone (it sounds differently if it is ...
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81 views

Measurement setup for power line spectrum

I've come across a setup for measuring AC power line spectrum. Here is the spectrum graph which shows 60Hz and harmonics in a power line voltage: And below is the setup and wiring for this ...
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1answer
68 views

Spectral analysis with RF signal generator

I need the spectral analysis of an LC circuit which oscillates in UHF band. I have a rough idea about its resonance peak but I need to observe it. As equipment, I have at my disposal Aeroflex 3020 RF ...
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75 views

Proper Spectrum Analyzer settings to match sweep speed to pulsed signal interval

I was trying to measure received signal level of a pulsed signal (at 433MHz) sending packages of 64 bytes with an interval of 1s. As shown in the attachment, the settings of Spectrum Analyzer are RBW=...
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133 views

Why spectrum analyzer ruined my oscillator's output?

I have been tried to investigate and fix this problem by myself. I however cannot find the solution. Please give me some advises. I used 3 traditional oscillator circuits with opamps (Wien bridge, ...
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388 views

Can I measure 220 V AC signal by spectrum analyzer ?

I want to observe noise in mains voltage. Can I measure 220 V AC signal by spectrum analyzer to observe noise? My spectrum analyzer GSP-830. Thanks!
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153 views

Measure S21 between 2 antennas at certain frequency using a Spectrum Analyzer

RX antenna is connected to the Spectrum Analyzer whose reading is regarded as P_RX. TX antenna is connected to a transceiver module that is set to work at the target frequency and emit certain power (...
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1answer
55 views

Measuring PSR of a current reference chip

Some Background: I'm designing a test board to characterize noise and PSR of a multiple voltages(1V) and currents(1uA) reference IC. The chip has a single voltage source. I use ultra low noise MUX ...
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291 views

Connecting a spectrum analyzer without DC block

I have seen many spectrum analyzers with the warning on the RF input port: “!!! Avoid electrostatic discharge and DC voltage !!!”. Out of precaution I always connected my signal source with a DC ...
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4answers
76 views

How to measure a fast-varying RF power in a circuit?

I have a circuit which generates an RF signal to drive a device, and I want to test it. For my application, I require the RF power to vary with a high frequency (of around 100 Hz), and the RF signal ...
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2k views

What does the attenuation setting do in an RF spectrum analyzer?

I have to make measurements of the RF power which a circuit is delivering, and I am using an RF spectrum analyzer for that purpose. I am a beginner in this topic, so I apologize if the question is too ...