Measuring E band microwave connections: Page 4 of 5

September 11, 2013 // By Dr. Wolfgang Wendler, Rohde & Schwarz
The growing volume of data traffic, due to the use of wireless devices, calls for high bandwidths for connecting base stations to the network. Two 5 GHz frequency bands between 71 GHz and 86 GHz are available in the E band for point-to-point connections.
range sufficient for measuring the spectrum mask. The ETSI technical specification defines a value of 50 dB. The R&S FS-Z90 harmonic mixer is also equipped with an isolator at the input, which makes a VSWR of typically 1.4:1 possible. Power measurement errors due to reflections at the input resulting from mismatch are typically reduced by a factor of 5 compared to mixers without isolators.

Click image to enlarge. Figure 2: Measurement of the same signal as in Figure 1 with the R&S FSW signal and spectrum analyzer. The input and image-frequency signal are 2.6 GHz apart. Measuring the spectrum mask or analyzing the modulation quality of significantly wider signals is possible without any difficulty.

Figure 2 shows the measurement of the same signal of an E band microwave connection as Figure 1. The 500 MHz bandwidth input signal and the image signal are 2.6 GHz apart, and it is possible to measure if the spectrum is within the prescribed mask (red line). The required dynamic range of at least 50 dB is also easily achieved with this setup.

The R&S FSW can measure the spectrum as well as the modulation quality. Its optional high analysis bandwidth of up to 320 MHz makes it possible to capture wideband signals, demodulate them with the vector signal analysis option and to analyze the modulation quality.

Click image to enlarge. Figure 3: Modulation analysis of a 300 MHz bandwidth QPSK signal. Besides graphic displays, e.g. the constellation diagram or input signal versus time, values displayed in tabular form offer information about the modulation quality at a glance.

Figure 3 shows the analysis of a 300 MHz bandwidth QPSK signal. The error vector magnitude (EVM) as a measure of the modulation quality, as well as the frequency error, the symbol rate error and many more parameters can be measured. The R&S FSW signal and spectrum analyzer displays the results in tables or graphs. For example, the phase and

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