Martin Laabs

Carrier recovery for sub-millimeterwave wireless transmission

The carrier frequencies of wireless systems are expanded to higher and higher frequency bands where huge bandwidths for data-hungry applications can be realized. One of the prospective regions is the sub-millimeterwave band. Wireless transmission needs coherent local oscillators at the transmitter and receiver for efficient operation. At such high frequencies, traditional methods of analog carrier recovery (e.g. narrowband filtering of the residual carrier and re-amplification) fail. At the same time, for high data rates above 10 Gbit/s, digital carrier recovery algorithms used in conjunction with free-running oscillators are too power-hungry and hard to realize. In this paper, a carrier recovery for a 300 GHz system based on the parallel transmission of a reference frequency together with the payload data is proposed. The corresponding electronic circuits for the transmitter and receiver are designed, manufactured and characterized.

Integrated Schottky diode detector for THz spectrometer

The longitudinal beam shape properties, crucial information to operators, can be monitored in modern superconducting linear accelerators measuring the generated THz radiation. Recent semiconductor technology may help to replace the single element THz detectors (e.g. used at the ELBE accelerator in Helmholtz-Zentrum Dresden-Rossendorf (HZDR)) as well as the costly and bulky THz spectrometers. Thats why we develop a simple integrated on-chip spectrometer in a GaAs technology that shall be able to resolve 5 to 20 frequency points in the frequency range between 0.1 THz to 1.5 THz. The core element is an integrated Schottky diode used as a power sensor connected to on-chip antennas and filters. First results show that a multi-narrowband antenna approach is very promising regarding complexity, sensitivity and selectivity. This paper explains the design and presents the first simulation results for an on-chip Schottky diode detector operating at 300 GHz that will be used on the on-chip spectrometer.

A planar Schottky diode based integrated THz detector for fast electron pulse diagnostics

Semiconductor based THz detectors are potentially cost-effective devices that can be manufactured in standard processes suitable for high frequencies such as GaAs, InP or SiGe. The core element of our detector circuit is an integrated Schottky-barrier diode used as a rectifier which is connected to an on-chip patch antenna. The detector operates at 300 GHz and is manufactured in a commercial GaAs technology. It is part of a multi-element array where each detector is tuned to a specific frequency in the range between 0.1 THz to 1.5 THz. The complete on-chip spectrometer will provide one more option to monitor the longitudinal beam shape properties in modern superconducting linear accelerators by measuring the THz radiation generated by electron bunches. Therefore, it may help to replace single element THz detectors as well as the costly and bulky THz spectrometers. We could conduct first measurements at the undulator THz source of the HZDRs linear accelerator and prove our detector concept. This paper briefly explains the system design and presents the first comparison between simulated data and measurement results of the on-chip Schottky diode detector operating at 300 GHz. We also present a bias-tee circuit developed and built for the measurement.

Active phased array antenna for animal location with passive surface acoustic wave based tags

Passive transponders based on surface acoustic waves (SAW) working at 2.4 GHz can be used in animal location systems inside stables where GPS fails. For that kind of systems, a steerable antenna is needed. Due to the environmental conditions inside a stable, a phased array antenna system providing electronic steering and avoiding moving parts is favorable. The design of such an active phased array antenna is explained. Based on the requirements from the location application, the antenna elements are developed first. Two candidates (patch and helix) are evaluated using simulations and measurements. To be flexible, a modularized approach (control unit, backplane carrying RF and antenna module) is chosen for the antenna system. First measurements of a line array are shown and discussed. Currently, the system is completed to form a 2D array which allows scanning in two directions.

Carrier Recovery Schemes for Submillimeter Wave Wireless Transmission

By moving carrier frequencies to higher and higher frequency bands, larger bandwidths can be provided for data-hungry wireless applications. The submillimeter wave region is a promising candidate for future systems. In order to accommodate sophisticated modulation formats, coherent local oscillators in the transmitter (TX) and the receiver (RX) are needed for efficient operation. However, traditional methods of analog carrier recovery (e.g., narrowband filtering of the residual carrier and reamplification) fail at such high frequencies and for many modulation formats. Also, digital carrier recovery algorithms used in conjunction with free-running oscillators are too power hungry and hard to realize for high data rates above 10 Gb/s. In this paper, carrier recovery schemes based on the parallel transmission of a reference frequency together with the payload data suitable for high data rates in the submillimeter waveband are proposed. They are demonstrated at 300-GHz carrier frequency. The corresponding electronic circuits for the TX and the RX are designed, manufactured, and characterized.

Modular steerable active phased array antenna at 2.4 GHz

Phased array antennas can cover a wide range of applications, e.g. localizing passive tags. Depending on the specifications for antenna gain, beam width and scanning range, different types and numbers of antenna elements are required. This kind of flexibility is provided by a customizable approach consisting of a control module and backplanes that carry RF and antenna modules where amplitude and phase shifting needed for beamforming takes place. Furthermore, an initial calibration of the antenna has to be carried out in order to compensate for tolerances in the manufacturing process. In this paper, a 4×4 array is realized and presented which allows full 2D beamsteering. Comprehensive measurement results are shown and discussed.