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Today we are witnessing a true revolution in wireless communications. The history and technology behind mobile communications is fascinating, and Bell Labs has had a major role in launching this multi‐billion dollar industry. In this paper, we take a brief look at the history of mobile communications—including many Bell Labs milestones and contributions to wireless technology—and provide a glimpse into the future. We also summarize the development of the industry and the path leading to today's imminent launch of third‐generation (3G) systems. Finally, we identify and present in detail several selected enabling technologies, along with breakthrough Bell Labs research in these areas.

We have studied the low temperature(T〈 4.2 K) current-voltage characteristics of a c-axis-perpendicular epitaxial YBa2Cu3O7thin-film microbridge, separated from a parallel Sn film by an insulating layer, to search for evidence of theoretically-predicted current-driven plasma instabilities. We have observed small induced voltages across the microbridge which are consistent with the predicted phenomenon. The assignment of the observed voltage to the plasma instability is not unambiguous, however, and possible future work is discussed.

We have performed resistance measurements on thin films of the high-temperature superconductor YBa2Cu3O7 (YBCO) in applied magnetic fields to above 200 T (2 MegaOersted) at temperatures as low as 2.5 K. The fields are produced by an explosively driven flux-compression system. We can see a particularly clear onset, without replotting the data, of the “hydrodynamic” flow of vortices probably because of the very fast increasing field. The low-temperature “critical field” for the field parallel to the c-axis of the sample is 135 T. Our data in the other direction are still preliminary. We discuss possible interpretation of our results.

We review methods of measuring surface resistance (Rs) of thin films using stripline resonators, and present our measurements of theRs of YBa2Cu3O7-x films as a function of frequency, temperature, and r.f. magnetic field. The films were deposited on LaAlO3 substrates by two methods: (1) electron-beam coevaporation of Y, BaF, and Cu followed by annealing in O2, and (2) single-targetin situ sputtering. The measurements were obtained at frequencies from 0.4 to 10 GHz, temperatures from 4 to 90 K, and an r.f. magnetic field range from 0 to 30 Oe. At low temperature and low r.f. field at 0.4 GHz, theRs values obtained for the two deposition methods are approximately 7×10-6 and 4×10-6 O, respectively.

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High-temperature superconducting technology along with conventional semiconducting elements has been incorporated into the design of a subharmonically pumped digital phase modulator and demodulator capable of Gb/s transmission rates. The appropriate bandpass filters, stopband filters, and matching networks are fabricated from postannealed double-sided YBa/sub 2/Cu/sub 3/O/sub 7/ films on 10 mil LaAlO/sub 3/. Typically, these films have T/sub c/>90 K, J/sub c/>2*10/sup 6/ A/cm/sup 2/ at 77 K, and surface resistance at 10 GHz and 77 K of approximately 0.6 Omega /sq. The use of superconducting microstrip filters and matching elements with conventional nonlinear devices provides significant performance improvements, including higher bit rates, lower intersymbol interference, and lower conversion loss than for conventional circuits.

We have measured the upper critical fieldHC2(T) of YBa2Cu3O7 (YBCO) thin films in magnetic fields up to 140 T forH applied parallel to thec-axis of the film. The critical field in the zero-temperature limit is 138 T, and the temperature dependence does not fit any simple model.