Adaptive Millimetre-wave Integrated TranSmitters

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Millimetre-waves enable ultra-high data rates. However, the high propagation loss limits the coverage range. At the expense of a large dc power, the coverage range and the data rate can be massively increased by using antenna transmitters featuring a large number of active paths. In ADAMIS we want to explore novel architectures and methodologies for millimetre-wave systems allowing an optimum trade-off regarding data rate, transmission distance and dc power consumption by applying adaptivity at system, circuit and device level. For this purpose, an adaptive transmitter frontend is developed, which features multiple switchable and tuneable active paths. At very low coverage range up to a few centimetres (e.g. for on-board communication) and/or low data rates, only one active antenna path with low directivity is activated. The circuits operate in a low power mode and the vector modulators are deactivated. For large distances (up to 10 m) and/or large data rates (up to 50 Gb/s) all active antenna paths incl. vector modulators for beamforming are activated. In this mode, the circuits operate at maximum gain and output power. At millimetre-wave frequencies, the variable gain amplifiers required within the vector modulators strongly change their phase versus gain requiring a complex control. We will investigate advanced topologies solving this problem, e.g. by cascading stages with inverse errors. To better understand and optimise the circuits we derive analytical expressions for the relevant transfer functions. For the adjustment of the parameters (number of paths, power and vectors), we study and compare two approaches: First, by scanning the parameters at millimetre-wave frequencies and measuring the receive strength or bit error rate, and second, by employing a low-power 2/5 GHz radar for positioning of the transmitter and the receiver. Hence, the optimum transmission angles and distances can be reliably extracted up to large distances. The latest IHP BiCMOS technology is used for the development of the frontend operating at 220-270 GHz. Each path consists of an antenna, a power amplifier, a vector modulator, a mixer, a frequency quadrupler and a binary phase modulator. Several antenna structures and packaging concepts will be investigated. To test the developed transmitter frontend, a receiver using existing lab-equipment will be designed. To minimize the power consumption and to allow the realisation of a fully integrated transmitter within the limited resources of this project we will focus on BPSK (binary phase shift keying) modulation, which can be realised with almost negligible dc power consumption by exploiting the differential circuit phases. Hence, no power consuming data converters are required. Due to the large available bandwidth of up to 50 GHz, a high data rate of 50 Gb/s is possible. In the low data rate and/or low distance mode, ultra-low dc power consumption is possible.