A spectrum analyzer is a device that measures the power spectrum. It is often used to examine the components of a waveform, whether it is electrical, acoustic or optical in form. There are basically two kinds of spectrum analyzers, the analog and the digital.
It also displays the received signal and compares the bandwidth to the frequency. A comparison is often done with an Oscilloscope, which compares the strength of the signal against the time.
Spectrum analyzers are also useful in analyzing amplitude against the frequency. Amplitude is normally measured in power or in dBm instead of volts, which is what is normally used in most spectrum analyzer.
The reason behind this is the fact that there are low signal strengths and frequency of movements that may not be measured. Spectrum Analyzers can only measure the frequency of the response at powers as low as 100 dBm. These are the levels that are frequently seen in microwave receivers. Oscilloscopes, on the other hand, cannot measure such very low voltage. The device can only deal with very low frequency levels and high amplitude.
The analog analyzer uses a filter with a mid-frequency that can be automatically shifted through a series of frequencies where the spectrum will be measured. The digital spectrum, on the other hand, utilizes a mathematical process called the Fast Fourier Transform (FFT), which is used to transform a wavform into the different components of its frequency spectrum. This way, computer programs who do the transformations will make the audio processing much easier. FFTs, however, are not only used for this purpose. They also have applications in other fields.
There are also spectrum analyzers that makes use of a technique wherein the incoming signal is converted into a lower frequency. This hybrid technique uses first the superheterodyne and then the FFT techniques. Examples of spectrum analyzers with this technique are those made by the Tektronix from the real-time spectrum analyzer series.
Spectrum Analyzers have so many applications. One application is the device frequency response measurement, which refers to the amplitude response of a machine against frequency of device.
Another application is Microwave Tower Monitoring, which measures the transmitted power of the machine as well as the power that it receives. This is utilized for the verification if the signal strengths and frequency of the transmitter. A directional coupler is used to tap the power. This is done so as not to disturb or interrupt communications.
A spectrum analyzer is one instrument that is often used in the conversion of higher frequencies, often those that range up to 10s gigahertz. It is a sensitive receiver that works based on the super-heterodyne receiver principles.
Once received by the spectrum analyzer, the frequency signal is swept through a pre-selected set of frequencies. The selected frequency is then converted into a DC level, a logarithmic scale, that can be measured. It is also displayed on the CRT, where the y-axis contains the signal strength while the frequency is seen on the x-axis.
Spectrum analyzers, however, cannot detect signals that are too weak or weaker than the noise in the background. This is the reason why the spectrum analyzer is often used in tandem with an RBW. In fact, RBW is one of the vital considerations in choosing or buying a spectrum analyzer.
Here, the received signal strength is measured in dBm or what is called decibels, the zero of which corresponds to 1mWatt on the logarithm scale. The reason for the use of power or decibels instead of the usual voltage is the fact that what is being measured are the low signal strengths and the frequency range of measurement.
Spectrum analyzers can only measure the response of a device powered at 120 dBm. These are the power levels that are normally seen in microwave receivers.In addition to the RBW, there are other key features of spectrum analyzers that people need to consider before buying one. One of these vital components is the resolution width, which affects the sensitivity of the spectrum analyzer. In fact, the sensitivity is directly dependent on this feature. For instance, if the measurements are the over a wide band, a 3 KHz RBW will normally be effective.
However, if you need to analyze a much narrower spectrum, such as with filters, then you may need a bandwidth resolution of 300Hz or a 10 Hz RBW. All depends on how the spectrum analyzer will be used. Another feature is the frequency range, which refers to the frequencies that you will be needing in order to take measurements. Spectrum analyzers have ranges from 100 Hz to 50.
Another is the frequency stability, which allows the spectrum to maintain its frequency within a specific levels that is precise and accurate. Often, the frequency stability is entirely dependent on the stability of the oscillator. A provision for Narrow band measurements for instance is an important parameter because spectrum analyzers do not usually have very high stability clocks.
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