Proper antenna selection will be critical to the success of WSCE. The review below shows why.

The W-band Analysis and Verification (WAVE) project uses three static spot beams from two antennas on a GEO satellite. The three beams provide ground diameter coverage of 200 km, 700 km and 2000 km. A key concern is connecting high-power amplifiers that work in the W-band to the antennas using gyrotronic travelling wave tube (TWT) technology [1]. The reference also provides preliminary figures for beam angle and antenna gains.

The Data Collection Experiment (DCE) of the Data and Video Interactive Distribution (DAVID) mission uses a steerable receive/transmit antenna for the W-band portion of the system [2]. This antenna, hosted on a LEO platform, uses an orthomode transducer (OMT) to separate left hand circular polarized (LHCP) transmit signals from right hand circular polarized (RHCP) receive signals. Waveguide technology (WR10, S-type) is also used here to connect the antenna to the onboard transceiver. The antenna is steered by moving only the planar main reflector; the feed and parabolic sub-reflector remain stationary.

The French STENTOR Program, which also has a W-band component, uses a transmitting active antenna (AATx) and a transmission-reception antenna with a large reflector (LRA). As described in [3] the LRA is an ultra-light reflector antenna (9.0 kg for reflector and source, 2.4 m diameter) with 40 dB gain. The AATx is comprised of a 0.6 m2 radiating panel with 48 radiating elements. The elements are supplied by 12 active quadri-module solid state power amplifiers (QSSPA), which in turn are driven by a beam forming network (BFN). Three beams can be generated simultaneously with individual amplitude and phase control.

The Advanced Communications Technology Satellite (ACTS) used dynamic hopping spot beams and in conjunction with onboard switching and processing. The beam hops from one location to the next within fractions of a millisecond; and then revisits each location in the following millisecond. Iridium and Teledesic have now deployed this technology. The Beam Forming Network (BFN) can switch beams within one microsecond [4].
It is noteworthy that these agile beams were a key part of a rain fade compensation protocol that achieved very high system availability at extremely low bit rates over different time periods in both the 20 GHz and 30 GHz band [5].

A survey of work on millimeter wave antennas done twenty years ago [6] indicated very active research into integrated antennas, i.e. a single module that both radiates and performs signal processing or some other function. A survey article released a few years later [7] shows a significant growth in the research area. The ferrite-based beam-shifters in the ACTS program had apparently been superseded; and quasi-optical ways of combining power were under investigation. Currently the literature on active integrated antennas has exploded. Even short articles [8] address a multitude of techniques: metamaterials for leaky wave antennas; microelectromechanical systems (MEMS) to make tunable high impedance surfaces (HIS); using MEMS to drive reflectarrays for beam steering and modulation; coupling dielectric lenses directly to beam steering arrays; and dielectric rod waveguides (DRW) for phase shifting with minimal loss.
In summary:
a) Antennas are a critical component of this effort.
b) Use of agile beam hopping has significantly enhanced fade mitigation techniques.
c) This technology is now part of the commercial telecommunications infrastructure.
d) Active integrated antenna technology is moving forward rapidly. It is now done in concert with signal processing, metamaterials, MEMS and optical methods.
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Antennas for the fixed and mobile ground sites must be capable of:
a) Receiving polarized beacons for the depolarization study;
b) Accommodating deep fades for the various attenuation studies (i.e. high G/T ratio);

Specifications for the ground and flight antennas to be used in follow-on phases will be prepared. The focus will be on finding the most capable and flexible antenna options available, which will almost certainly include agile beam hopping.

References

[1] Jebril, A., et al. "The WAVE Mission Payload." IEEEAC, 2005: 1-10.

[2] Ruggieri, M., M. Pratesi, A. Salome, E. Saggese, and C. Bonifazi. "The W-Band Data Collection Experiment of the DAVID Mission." IEEE Transactions on Aerospace and Electronic Systems 38, no. 4 (October 2002): 1377-1387.

[3] Ehster, B. "STENTOR Programme." Proceedings of the Euro-Asis Space Week Cooperation in Space. Singapore: ESA, 1999. 137-144.

[4] Gargione, Frank. "ACTS Hardware - A Pictorial." Archive Set 390. AIAA, 1990. 490-496.

[5] Cox, C.B., and T.A. Coney. "Advanced Communications Technology Satellite (ACTS) Fade Compensation Protocol Impact on Very Small Aperture Terminal Bit Error Rate Performance." IEEE Journal on Selected Ares in Communications (IEEE) 17, no. 2 (February 1999): 173-179.
[6] Schwering, Felix K. "Millimeter Wave Antennas." Proceedings of the IEEE (IEEE) 80, no. 1 (January 1992): 92-102.

[7] Yongxi, Qian, and Tatsuo Itoh. "Progress in Active Integrated Antennas and Their Applications." IEEE Transactions on Microwave Theory and Techniques (IEEE) 46, no. 11 (November 1998): 1891-1900.
[8] Raisanen, A. V., et al. "Beam-steering antennas at millimeter wavelengths." Millimeter Waves (GSMM), 5th Global Symposium on. IEEE, 2012. 170-173.
3.4 Antenna Types:
