Measuring E band microwave connections

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.

The high frequencies are a challenge for T&M equipment; not only when developing transmit and receive modules, but also when measuring transmission systems.

E band: extra bandwidth for more data

Over 30 years ago at the World Radiocommunication Conference WARC-79 in Geneva [1], the International Telecommunication Union (ITU) passed the decision to dedicate the E band frequencies from 71 GHz to 76 GHz and from 81 GHz to 86 GHz for transmission applications. It took more than 20 years before commercial interest in these applications emerged and led the US Federal Communications Commission (FCC) and European authorities to issue licenses for these bands and to specify the technical requirements for their use. The reason why interest finally evolved was that, by then, it had become possible to commercially manufacture components for this frequency range. At the same time the demand for increasing transmission rates made it necessary to use new frequency bands. Transmission links with data rates of several Gbit/s are no problem in the E band. The two frequency bands, each with a continuous range of 5 GHz, make transmission bandwidths of several 100 MHz possible. Combined with a simple modulation method such as BPSK, high data rates can be achieved. Consequently, it is possible to implement simple and reliable transmit and receive modules for these millimeter-wave connections. It goes without saying that more complex types of modulation may be used as this technology evolves. The achievable range in these frequency bands is only insignificantly shorter than for example in the 38 GHz band. This was proven with open field tests done in normal weather conditions with an attenuation of 0.5 dB/km [2].

The high frequencies pose new T&M challenges. Although licensing protects against interference from other microwave sources, the power and spectrum of the transmitters must be measured to ensure disturbance-free coexistence of licensed communications. The requirements for transmitters in this frequency range, especially for the radiated power

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