What is a Spectrum Analyzer?
Applications for Spectrum Analyzers,
Key Features to Consider When Buying a Spectrum Analyzer:
Typical Features of a Spectrum Ananlyzer,
Spectrum Analyzers that you may consider buying,
Where to buy spectrum analyzers:
1. What is a Spectrum Analyzer?
A spectrum analyzer is a wide band, very sensitive receiver. It displays received signal strength (y-axis) against frequency ( x-axis). Compare this with Oscilloscope, which displays received signal strength (y-axis) against time (x-axis). Spectrum analyzer is useful for analyzing the amplitude response of a device against frequency. The amplitude is normally measured in dBm in Spectrum Analyzers, where as the same is measured in volts when using Oscilloscopes. The primary reasons for measuring the power (in dBm) rather than voltage in Spectrum Analyzers are the low signal strength, and the frequency of measurement. Spectrum analyzers are capable of measuring the frequency response of a device at power levels as low as –100dBm. (Note that 0 dBm corresponds to 1 mWatt of power on a logarithmic scale). These power levels are encountered frequently in microwave receivers, and spectrum analyzers are capable of measuring the device characteristics at that power levels. Normally, Oscilloscope can not measure such low voltage levels and are intended for low frequency, high amplitude measurements. The spectrum analyzer measurements are in frequency domain, whereas the oscilloscope measurements are in time domain.
2. Applications for Spectrum Analyzers:
- Device Frequency Response Measurements: You can use spectrum analyzers for measuring the amplitude response (typically measured in dbm) against frequency of device. The unit of frequency is Hertz. 1000Hz=1KHz, 1000Kz=1MHz, 1000MHz=1GHz. The device may be anything from a broadband amplifier to a narrow band filter.
- Microware Tower Monitoring: You can measure the transmitted power and received power of a Microware tower. Typically, you use a directional coupler to tap the power without interrupting the communications. In this way, you can verify that the frequency and signal strength of your transmitter are according to the specified values.
- Interference Measurements — Any large RF installations normally require site survey. A spectrum analyzer can be used to verify identify and interferences. Any such interfering signals need to be minimized before going ahead with the site work. Interference can be created by a number of different sources, such as telecom microwave towers, TV stations, or airport guidance systems etc.
- Other measurements that could be made using spectrum analyzer include the following:
- Return-loss measurement
- Satellite antenna alignment
- Spurious signals measurement
- Third harmonic measurements
- Intermodulation measurements
3. Key Features to Consider When Buying a Spectrum Analyzer:
1. Resolution bandwidth
2. Frequency range
3. Frequency stability
4. AC/DC Operation
5. Service warranty
- Resolution bandwidth: This is an important parameter to consider when buying a Spectrum Analyzer. The sensitivity of the spectrum analyzer is directly dependent on the resolution bandwidth of the analyzer. If your measurements are over a wide band, a 3 KHz RBW is normally sufficient. If you need to make very narrow band measurements (such as filters), then consider a 300Hz or even a 10Hz RBW spectrum analyzer. Obviously, a spectrum analyzer with lower RBW costs more than a spectrum analyzer with 3 KHz RBW.
- Frequency range: This is the range of frequencies that you need to make measurements. Spectrum analyzers are available from 100 Hz to 50 GHz range. If you require measurements up to, say IF to 2.4 GHz, a spectrum analyzer from 10MHz-2.4 GHz would be suitable.
- Frequency Stability: Frequency stability is the ability of the spectrum analyzer to maintain the frequencies within a specified accuracy. The frequency stability is dependent on the Local Oscillator stability of the spectrum analyzer. For narrow band measurements, this is a very important parameter. Spectrum analyzers do not normally have very high stability clock. If high accuracy of measurement is required, consider buying a spectrum analyzer with provision for external frequency reference. In such an event, the accuracy of the spectrum analyzer is as good as the external reference.
- AC/DC operation: If you need to make measurements out-doors, you may require DC operation. Check if it is available.
- Service warranty: Normally, spectrum analyzers are very expensive. A comprehensive warranty is recommended when buying a spectrum analyzer. Also ensure that the rf input connection has dc protection.
4. Typical Features of a Spectrum Ananlyzer:
Given below are the important features available with a 8563EC Portable Spectrum Analyzer, 9 kHz to 26.5 GHz:Color displayContinuous 30 Hz to 26.5 GHz sweepFast digital resolution bandwidths of 1, 3, 10, 30 and 100 HzAdjacent channel power, channel power, carrier power, occupied bandwidth percentage and time-gated measurements standardPrecision timebase and 1 Hz counter resolutionMIL-PRF-28800, Class 3 ruggedMeasurement personalities for digital radio and phase noise measurementsEasily transfer screen image or trace data to PC with E4444A BenchLink software
5. Spectrum Analyzers that you may consider buying:
The price is primarily determined by the frequency range (i.e. the range of operation of the instrument), the resolution bandwidth, and the frequency stability. Some instruments have additional options such as in-build tracking generator, frequency counter, or power meter that may also add to the overall cost.
1. Avcom PSA Series
2. BK Precision 3.3 GHz Spectrum Analyzer
3. Instek 2.7 GHz Spectrum Analyzer
1. Anritsu Handheld 7 GHz Spectrum Analyzer
2. Anritsu MS2681A Spectrum Analyzer (9 kHz to 3 GHz), High Performance
3. R&S 6 GHz Spectrum Analyzer
1. Agilent ESA-L Spectrum Analyzers
2. Agilent ESA-E Spectrum Analyzers
3. Anritsu MS2668C Spectrum Analyzer (9kHz to 40GHz)
6. Where to buy spectrum analyzers:
Given below are some of the sources to buy spectrum analyzers:
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