The demand for higher broadband speeds is ever increasing whereas the deployment of full fibre to the premises is slower than initially predicted and remains costly. Solutions exploiting the existing, ubiquitous, copper network and increasing its capacity would be highly beneficial in the near term. One approach is to use surface wave (SW) transmission mode to transmit signals over the existing copper cabling network. We present proof-of-concept experimental SW data transmission on twisted pair cables. A surface wave launcher for low GHz carrier frequency operation is designed and optimised. Experimentally, we demonstrate data rates in excess of 12 Gb/s in a 1.15-3.25 GHz band over a 6.1 m twisted pair cable with an average bit error rate of$2.25 \times 10 ^{-5}$, without coding or feedback implementation. Furthermore, higher frequency bands are tested with data rates up to 3.4 Gb/s displaying their potential for surface wave transmission. S-parameter measurements allow capacity estimations of SW data transmission on longer cable lengths using water-filling algorithms. Our calculations predict over 13 Gb/s capacity on a 100 m cable using a 3.5 GHz transmission bandwidth, this may be further extended by further increases to the bandwidth used for SW transmission.

This paper re-examines the 100 Ohm characteristic impedance assumption used in the context of Digital Subscriber Line in the very to ultra high frequency range. A novel method of measuring the characteristic impedance of a transmission line is introduced which uses time-gated measurements from a vector network analyser. The results are utilised to synthesise impedance matching circuits for the excitation of a single twisted pair and a two pair underground cable at centre frequencies of 150 MHz and 500 MHz. These circuits achieved reflections as low as -40 dB. Furthermore, we report gains in transmission increasing with frequency, ranging from few decibels below 100 MHz, to several in 100-250 MHz and many above 400 MHz when compared to a commercial reference balun. In fact, compatibility tests beyond the target cable samples demonstrated higher than 10 dB gains in 20, 40 and 60 metre underground cables at around 500 MHz indicating that sample-based matching circuits are not entirely sample-specific. Preliminary tests showed no significant change in crosstalk when using differential matching circuits.