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This contribution details the motivation and the status of a new satellite mission, which targets the in-orbit verification of a wideband satellite communication link operating in the high millimeter-wave regime at 71–76 GHz. The paper reviews the dynamic link budgets for data links between satellites in low-earth orbits and ground stations on close to sea level, taking into account the expected atmospheric attenuation according to lTU models and supported by successful terrestrial transmission experiments, which confirm the feasibility and attractiveness of exploiting allocated spectrum in E-band for Gigabit satellite feeder links of globe-spanning satellite constellations and high capacity data downlinks in earth observation, even under adverse weather conditions. The scientific payload, hosted by a 6V-Cubsat platform, comprises a high-performance E-band transmitter with GaN-based solid state power amplifiers, an InGaAs-based low-noise receiver and a modern FPGA-based digital processing unit realizing AWG functionality and 4k image/video storage. The ground terminal employs a highly directive Cassegrain antenna with coarse GPS and fine RF tracking and a low-noise receiver.

A wireless communication link operating in E-band at 71-76 GHz with 30 dBm of transmit power from a GaN-based solid-state power amplifier and a 3-dB noise Figure of its GaAs-based receiver is employed in a data transmission with up to 9.8 Gbit/s data rate between a plane and a ground station. Flying at a height of 1000 m above ground and at distances between 5 and 12 km from the receiver, a microlight aircraft hosts the payload mounted to its wing. The highly directional link is formed by a 39.7 dBi gain Cassegrain parabolic antenna in the plane-mounted transmitter, and a 48.7 dBi Cassegrain antenna with GPS-based antenna tracking in the ground terminal. Stable data links were established with up to 9.8 Gbit/s data rate employing QPSK, 8-PSK and 16-QAM modulation.

The Russians launched the first artificial Earth satellite, Sputnik 1, into an elliptical low-Earth orbit (LEO) in October 1957. Through its four external antennas, Sputnik 1 broadcast radio beacons at 20.005 and 40.01 MHz to study the density of the atmosphere and the radio-wave propagation through the ionosphere. This historic event represents the advent of the satellite age. Since then, satellites have become an integral part of global navigation, Earth observation, broadcasting, and communication systems. The latter complements conventional wired and wireless terrestrial communication and provides an effective platform to relay radio signals between two arbitrary points on or near the Earth. Satellite communication offers end users a high level of flexibility. Irrespective of the geological coordinate, the user can benefit from a broad spectrum for various applications, from two-way voice and data communication to video conferencing.

With the growing interest in millimeter-wave (mmW) communication links, especially for multi-gigabit backhaul applications, detailed studies on the performance limits in terms of achievable transmission distance and data rate, but also, and perhaps even more important, thorough investigations on the influence of different weather conditions gain in importance. In this paper we present a millimeter-wave monolithic integrated circuit (MMIC)-based transmit and receive front-end and ultra-broadband wireless data transmission experiments utilizing a 240 GHz carrier frequency in a long-range outdoor scenario as well as measurements inside a climatic wind tunnel. Data rates up to 64 Gb/s and various complex modulation formats are employed. While in the outdoor transmission, the link is tested in terms of maximum achievable transmission distance and data rate as well as alignment accuracy, in the climatic wind tunnel the influence of rain and fog in the transmission path is investigated in a defined and controlled environment.

This paper presents the influence of bandwidth-dependent deterministic impairments of diplexer filters on the performance of an E-band wireless link. The degradation of performance due to group delay variation and amplitude ripple in the analog front-end transmission chain is considered based on the system-level simulation and compared to measurements. The study involves the impairments characterization and their behavior in a transceiver system. The impairment decomposition method is performed in order to validate the measurements of error vector magnitude for QPSK transmission with variable baud-rates up to 4 GBd. We show that for a given RF bandwidth of 5 GHz, within an E-band RF chain configuration for downlink diplexer filters, the EVM performance related to deterministic linear impairments degrades by 3.3% (2.3 dB), while in case of uplink diplexer filters, it degrades by 4.25% (4.5 dB).

Attenuation measurements through extreme rain in a climate wind tunnel are carried out to benchmark the possibility of wireless data transmission at 77 GHz during adverse weather conditions. Based on a network analyzer and external E-band mixers, the propagation loss at 77 GHz is obtained over a distance of 180 m using a corner reflector at the end of a 90-m tunnel. Comparing the results to prediction models like the ITU-R P.838, a large deviation of several tens of dB/km was found for high rain rates when the drop size distribution is neglected. In the paper, the authors use known attenuation models based on rain drop distribution functions to explain the high measured attenuation during the testing, demonstrating a large variation of specific attenuation under heavy rain at high microwave frequencies.

The paper reviews our recent experimental work in the area of multi-Gigabit fixed wireless links operating in the high millimeterwave frequency range. An E-band link is employed to transmit up to 6 Gbit/s over a line-of-sight terrestrial distance of 36.7 km using QPSK modulation, and 15 Gbit/s over 15 km using 8QAM. At 240 GHz, up to 64 Gbit/s QPSK are transmitted over a distance of 850 m. The paper details the unified architecture of the analog transmit-receive frontends, reports EVM and BER data for these links and discusses link budget calculations.

Wireless transmission of broadband complex modulated data up to a bit rate of 6Gbit/s in E-band downlink frequency over a record distance of 36.7km is presented. The received signal quality is monitored for the transmitter working in both linear and saturation region. The overall link performance is evaluated in terms of error vector magnitude (EVM) and signal to noise ratio (SNR). The 6Gbit/s QPSK signal was received with an EVM of –11.48dB corresponding to an SNR of 11.46dB and a theoretical BER value of 5 × 10–3, when the last stage power amplifier in the Tx chain was operating near saturation region. Further, the atmospheric losses are derived from the measurements and compared with the theoretical values calculated from the ITU models for the atmospheric losses due to the dry air and water vapor.

A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.

This work discusses the fabrication of two GaN-based power amplifier modules, suitable to increase the available output power levels of E-band multi-Gigabit fixed wireless links dedicated to aeronautics and space applications. The first mounted module contains one GaN-based power amplifier MMIC, packaged in a WR-10 waveguide environment. The module shows a small-signal gain of 13.4 dB with a gain flatness of ± 1 dB, along with a saturated output power of more than 26 dBm (400 mW) for the entire intended frequency range between 71–76 GHz. The second module, parallelizing four MMICs, demonstrates a high saturated output power of more than 31.1 dBm (1290 mW), along with a small-signal gain of typically 11.2 dB and a flatness of ±1 dB within the frequency range of interest.

In this paper an E-band transmitter chain with a maximum RF output power of 29 dBm for a 1 GBd QPSK signal is presented. The high output power is achieved by applying AlGaN/GaN-based power amplifiers as final stage of a module chain which further comprises a GaAs mHEMT-based quadrature up-converter, LO frequency multiplier-by-eight and driver amplifiers. The output power remains higher than 27 dBm for up to 6 GBd symbol rate and a modulation complexity of up to 32 QAM. In this work the effect of different PSK and QAM modulation format as well as the baud rate on the transmitted RF power level is studied through measurements. The linearity of the dual GaN PA module is evaluated for different types of modulation formats.

This paper presents a survey of the status of five active THz imaging modalities which we have developed and investigated during the last few years with the goal to explore their potential for real-time imaging. We start out by introducing a novel waveguide-based all-electronic imaging system which operates at 812 GHz. Its salient feature is a 32-pixel linear detector array heterodyne-operated at the eighth subharmonic. This array in combination with a telescope optics for object distances of 2-6 m reaches a data acquisition speed suited for real-time imaging. The second system described then is again an all-electronic scanner (now for around 300 GHz ), designed for object distances of ≥ 8 m , which combines mechanical scanning in vertical direction, synthetic-aperture image generation in horizontal direction, and frequency-modulated continuous-wave sweeping for the depth information. The third and fourth systems follow an optoelectronic approach by relying on several- to multi-pixel parallel electrooptic detection. One imager is based on a pulsed THz-OPO and homodyne detection with a CCD camera, the other on either continuous-wave electronic or femtosecond optoelectronic THz sources and a photonic-mixing device (PMD) camera. The article concludes with a description of the state of the art of imaging with focal-plane arrays based on CMOS field-effect transistors.

This paper presents the wireless data transmission of complex modulated signals in the E-band using a MMIC-based link compared to the current state of the art in millimeter-wave wireless communication. Highly linear and extremely broadband frontend components in combination with the latest equipment to generate and analyze broadband complex data signals are used in this experiment. The received signal quality is evaluated in terms of EVM and BER. An error free QPSK transmission with a data rate of 40 Gbit/s over a wireless distance of 6m is presented, while the transmission of 80 Gbit/s signals, achieved by 16-QAM modulation, results in a BER of 3.7 × 10−3.

A directive fixed wireless link operating at a center frequency of 240 GHz achieves a data rate of 64 Gbit/s over a transmission distance of 850 m using QPSK and 8PSK modulation, in a single-channel approach without the use of spatial diversity concepts. The analog transmit and receive frontend consists of active monolithic integrated circuits including broadband RF amplification and quadrature subharmonic mixer channels. The analog frontend is addressed by 64 GSa/s ADC and DAC boards, which are amenable to real-time data transmission. A link budget calculation allows for the estimation of the performance under adverse weather conditions.

High carrier frequencies in the terahertz range 0.1...30 THz are required for wireless data transmission at line rates at or beyond 100 Gbit/s. Here we demonstrate a system with one to three carriers near 237 GHz for (75...100) Gbit/s single-polarization transmission over distances of (20...40) m. The narrow-band THz carrier is generated by photomixing of highly stable mode-locked laser lines in a uni-travelling-carrier photodiode. The electrical photodiode output is radiated over a lensed horn antenna. Besides a receiving lensed horn antenna, the receiver comprises monolithic integrated circuits with mixers and amplifiers. This synergetic use of THz photonics and electronics (“teratronics”) should be scalable to wireless Tbit/s transmission over 1 km. Such a wireless link could bridge the last mile to a subscriber, or could connect two spatially separated fibre gateways.

The influence of hydrometeors on a MMIC-based wireless data transmission at 240GHz carrier frequency was experimentally evaluated in a climatic wind tunnel over a distance of 90 m. Successful transmissions of up to 24 Gbit/s QPSK modulated signals through heavy rain at 43 mm/h and dense fog at 3 g/m 3 is achieved. The climatic impact is evaluated in terms of EVM. Reducing the bandwidth makes a transmission still possible with a BER

We present a PLL stabilized VCO at X-Band frequencies extended by a frequency multiplier-by-eight module forming a variable LO source for E-Band communication systems with enough output power to drive an E-Band mixer without additional post amplification. The module shows a 3-dB output bandwidth from 73 to 85 GHz with a saturated output power of 10 dBm. Together with the VCO module the source features a phase noise of −89 dBc/Hz at 100 kHz offset from the 76.8 GHz carrier.

In this paper, the transmission of broadband complex modulated signals with data rates up to 48 Gbit=s using an E-band MMIC-based analog frontend is shown. The paper presents the transmission of QPSK, 8-PSK and 16-QAM modulated signals with a symbol rate of 12 GBd. The received signal quality is evaluated in terms of error vector magnitude, which, measured in a coherent setup, shows values of −18.8 dB, −18.7 dB and −20.9 dB for the QPSK, 8-PSK and 16-QAM signal, respectively. Using a more application oriented incoherent setup, the signal quality decreases about 1 dB.

Based on active millimeter-wave monolithic integrated circuits (MMICs), a pair of receiver and transmitter modules have been developed and used for wireless data transmission experiments at 240 GHz with data rates of up to 40 Gbit/s. Both modules are driven with a subharmonic local oscillator, located at 120 GHz and feature broadband quadrature I/Q IF terminals. The receiver module has a maximum conversion gain of 3.8 dB at 240 GHz. The I/Q imbalance stays below 1.9 dB in the frequency range from 200 to 280 GHz. The transmitter achieves a maximum output power of -3.6 dBm.

The transmission of complex modulated data signals with data rates up to 30 Gbit/s is successfully realized using a 240 GHz wireless link based on active MMIC components. The paper presents the transmission of QPSK and 8-PSK modulated signals over a distance of 40 m as well as a characterization of the RF frontend based on S-parameter measurements and back-to-back signal transmission. The link quality is evaluated in terms of error vector magnitude (EVM) measurement. For a symbol rate of 10 GBd, the EVM measurement shows values of 10.3% and 15.2% for the QPSK and 8-PSK signal, respectively.

We present the first high-resolution (500 m × 500 m) gridded methane (CH4) emission inventory for Switzerland, which integrates the national emission totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and recent CH4 flux studies conducted by research groups across Switzerland. In addition to anthropogenic emissions, we also include natural and semi-natural CH4 fluxes, i.e., emissions from lakes and reservoirs, wetlands, wild animals as well as uptake by forest soils. National CH4 emissions were disaggregated using detailed geostatistical information on source locations and their spatial extent and process- or area-specific emission factors. In Switzerland, the highest CH4 emissions in 2011 originated from the agricultural sector (150 Gg CH4 yr−1), mainly produced by ruminants and manure management, followed by emissions from waste management (15 Gg CH4 yr−1) mainly from landfills and the energy sector (12 Gg CH4 yr−1), which was dominated by emissions from natural gas distribution. Compared to the anthropogenic sources, emissions from natural and semi-natural sources were relatively small (6 Gg CH4 yr−1), making up only 3 % of the total emissions in Switzerland. CH4 fluxes from agricultural soils were estimated to be not significantly different from zero (between −1.5 and 0 Gg CH4 yr−1), while forest soils are a CH4 sink (approx. −2.8 Gg CH4 yr−1), partially offsetting other natural emissions. Estimates of uncertainties are provided for the different sources, including an estimate of spatial disaggregation errors deduced from a comparison with a global (EDGAR v4.2) and a European CH4 inventory (TNO/MACC). This new spatially-explicit emission inventory for Switzerland will provide valuable input for regional scale atmospheric modeling and inverse source estimation.

We demonstrate a single-input single-output photonic wireless link at 237.5 GHz with record 100 Gbit/s data transmission over 20 m. We use an optical heterodyne I/Q transmitter and a state-of-the-art active I/Q-MMIC at the receiver.

Using dark rate dependent feedback and quench circuitry, avalanche photodiodes have been stably operated at voltages close to breakdown and above. Exploiting the large amplification in such an operation, time resolutions of 15 ps for 10 8 incident photons have been measured at temperatures around 0°C.

We present a heterodyne hybrid terahertz imaging system, which combines electronic narrow-band emitters, operating at 0.2 THz and 0.62 THz respectiveley, with a continuous-wave two-color laser system for electro-optic detection. The laser system employs two distributed-feedback laser diodes, providing a tunable difference frequency which is phase-locked to the emitted terahertz frequency with an offset of 10 MHz.

We present a fast-scanning active THz-camera with two different illumination techniques. The first uses local illumination and offers high dynamic range while the second uses global illumination and allows to expand the range of angles over which specular reflections are detected. Furthermore, the second approach holds the promise that the object topography can be resolved with larger uniqueness.

We present a scanning THz-camera with active illumination. Three different fully electronic transceiving techniques are evaluated: The first employs a commercial 230-320GHz frequency-modulated continuous-wave system with a harmonic mixing detector. Its bandwidth allows a ranging resolution in the mm-range. The second one is based on heterodyne detection operating at 645GHz with sub-harmonic mixer and provides a dynamic range beyond 100 dB. Like in the first system, we employ local illumination (THz beam focused on observed pixel). The third one equals the second one, but utilizes global illumination of the scene. In all cases, the scanning optics consists of a Cassegrainian telescope with a primary mirror diameter of 23 cm and a scanning mirror, which is spinning about a slightly tilted axis which itself is slowly rotated in a perpendicular direction to provide the second scan-dimension. With a typical distance of 0.5m between the scanning mirror and the object plane, the field of view covers several 100cm 2 . While the fast mirror axis spins with about 660RPM, the slow axis turns with at least 1 deg. per second and the data acquisition samples about 40000 points for each THz-image. Single-pixel detectors are used; the frame acquisition time is below 10 s. The development of a video-rate multi-pixel imager with up to 32 sub-harmonic mixers as detectors is in progress.

The development of active THz cameras with the potential for video-rate operation is an emerging and exciting research field. With our currently realized 645 GHz system we achieve scan rates of a few seconds with a one-pixel heterodyne detector and two-dimensional fast rotational scanning. The active illumination allows to resolve the object topography with subwavelength resolution. Within the next evolution step we will realize an active 812 GHz system incorporating a 1x32-pixel heterodyne detector array with one-dimensional scanning. This will allow video-frame-rates for images (amplitude and phase) with approximately 2000 pixels. But for large fields of view the quasioptical system must be optimized to minimize the aberrations inherent in all optical systems. We show, with the use of the optical software package Zemax, how to design, simulate and optimize such quasioptical systems for the one-dimensional 1x32-pixel heterodyne detector array. The resulting quasioptical system is diffraction-limited over the field of view (20 cm x 30 cm) at the design working distance of 4 m and has an adjustable focus optics for distances from 2 m up to 6 m.

We report on the realization of two active fully electronic THz cameras operating at different frequencies (645 GHz and 300 GHz) and room temperature. Active illumination together with the frequency modulation continuous wave approach allows us to implement unique features, such as phase-sensitive detection, working-distance selection and the suppression of spurious reflections. With both systems we are able to acquire images with more than 50000 pixels (phase and amplitude) in 9 seconds. The dynamic range exceeds 35 dB and we achieve a subwavelength depth resolution due to the measurement of the phase. The typical object distance is about 50-100 cm and the image size is on the order of hundreds of cm2. With frequency modulation of the source we are furthermore able to detect the position form objects up to an accuracy of a few mm.

We demonstrate a hybrid system for THz raster scan imaging using frequency-stabilized DFB lasers for electro-optic detection. The system combines a 0.65-THz micro-electronic narrow-band emitter with two synchronized diode lasers, providing two-color laser radiation. The functional principle promises three-dimensional real-time imaging capabilities.

We report on the realization of an active fully electronic THz camera operating at 645 GHz and room temperature. It currently acquires images with about 9000 pixels in 10 seconds. Each pixel contains the amplitude as well as the phase information of the reflected THz signal. Frequency modulation allows to select a specific working distance and to suppress spurious reflections. The typical image size is in the order of hundreds of cm2.

Schottky structures based on quasi-vertical diode (QVD) design concept are essentially improved by optimization of the GaAs/AlGaAs wafer layout and fabrication process. Insertion of a 4 mum-thin epitaxial AlGaAs layer permits more accurate micromachining of the membrane-substrate without significant degradation of anode parameters. This greatly improved repeatability and increased the yield of the fabrication process. New technology tolerances allowed further optimization of structure geometry, which in turn led to achievement of state-of-the-art mixer performance at millimeter-waves.

The main limitation of whisker-contacted diode technology is that no integration is possible. Therefore, the development of competitive planar Schottky barrier diodes has been put forward in the last decade. The quasi-vertical planar Schottky diode was proposed several years ago and the necessary technologies are developed for a reliable fabrication. We show the recent status of this type of planar Schottky diodes. At 200 GHz an output power of 5 mW (12.5% efficiency) has been achieved with a quasi-vertical planar varactor diode. Recent activities concentrate on anti-parallel Schottky mixer diodes and integration of diodes (0.8 /spl mu/m anode diameter) with several receiver components. These diodes offer characteristics comparable to substrateless diodes with the same diode parameters.