Multipactor has become a keylimiting factor of the final performance of satellite communication systems, due to the increase in power levels and/or operating frequency bands. As a result, the critical components of these systems must meet demanding multipactor specifications which should be considered during the design process. This paper describes the different techniques available to predict the multipactor threshold power for radio frequency (RF) and microwave passive hardware under continuous wave (CW) excitation, from cumbersome particle simulations to fast approximate methods based on circuit models. All these techniques have been described and compared together for the first time, including also a detailed description of the configuration issues of commercial particle simulators required to obtain accurate multipactor threshold predictions. The techniques are applied to both wideband and narrowband application examples. The predictions have been compared with measured thresholds of manufactured samples obtained with a novel multipactor test bed, thus allowing to highlight the advantages and limitations of each technique and particle simulator. From this paper, it will be possible to choose the most suitable procedure (and an appropriate simulator, if needed) to obtain multipactor threshold prediction of passive hardware.

This article presents a theoretical and experimental comparative study of the different multipactor threshold values obtained in the rectangular waveguide (RW) and the groove gap waveguide (GGW). To this end, the multipactor effect has been first analyzed in an RW with a recently developed theoretical model. Then, the multipactor breakdown power levels in the equivalent GGW have been predicted with an accurate electron tracking code, showing a significant increment compared with the RW case. In order to validate these results, two E-plane WR-90 RW transformers have been designed with a full-wave electromagnetic simulation tool. The central sections of these transformers have been implemented in RW and GGW, respectively, and their multipactor breakdown power levels have also been predicted. The two designed transformers have been fabricated in aluminum and then measured in terms of electrical response (scattering parameters) and RF multipactor effect (power threshold values). All the experimental results agree well with the set of simulated data, thus fully validating the performed study.

In this paper, we discuss how the use of the recently developed modified tuning pin (MTP) can be extended to the design of filters and diplexers implemented in rectangular waveguide, that can be reconfigured in a number of discrete states, and that can be used in high-power payloads. As an application example, the design of two reconfigurable filters and a reconfigurable diplexer is fully described. The high-power behavior of these components (in particular, with respect to corona and multipaction effects) is also studied in detail, in order to demonstrate that the structures that we discuss can operate correctly under high-power conditions. Furthermore, comparisons between simulations and measurements of several prototypes are also included, showing an excellent agreement between simulated and experimental data, thereby fully validating both the design approach and the filter reconfiguration strategy.

This article presents the theoretical study and experimental validation of the multipactor (MP) effect in bandpass filters implemented in groove gap waveguide (GGW) technology. Such filters are based on rectangular cavities and inductive coupling irises, whose optimized dimensions (widths and lengths) are fixed between rows of metal pins. For the effective design of the considered GGW filter, an equivalent counterpart in standard rectangular waveguide (RW) technology will be first studied, using very efficient tools for computing its electrical response and MP discharge breakdown levels. Two prototypes of the GGW and RW bandpass filters, designed to operate at 17.5 GHz (for Ka-band satellite downlink applications), are manufactured for validation and comparison purposes. Both of them are made of aluminium material, whose properties (in terms of secondary electron emission) have also been measured, as well as considered in the prediction of MP threshold levels using available software tools. Proceeding in this way, an outstanding matching between all simulated and experimental results of the MP effect has been achieved.

The Empty Substrate Integrated Waveguides (ESIW) maintain the advantages of the Substrate Integrated waveguide (SIW) (i.e. low-volume, low profile, lightweight, easy manufacturing, and integration in a planar circuit board), and present lower losses and higher quality factors in resonators due to the propagation of the fields through air, instead of through lossy dielectric as in SIW. The operational (monomode) bandwidth of the ESIW can be increased with the Single Ridge ESIW (SRESIW). However, the bandwidth can be further increased with the Double Ridge ESIW (DRESIW). In this paper, a brief study of possible DRESIW geometries has been performed, and two transitions from microstrip line (MS) to DRESIW with a dielectric taper geometry based on different equations are proposed. The new wideband transitions present simulated return losses in back-to-back configurations greater than 20 dB in more than a 95% fractional bandwidth. The transition that presents a better compromise between return losses, bandwidth and ease of fabrication is manufactured. The measured return and insertion losses are better than 19.7 dB and 1.5 dB, respectively, in a 96.4% fractional bandwidth.

Spaceborne Synthetic Aperture Radar (SAR) instruments are becoming a very important source of information for Earth observation. These systems produce a great amount of data to be stored and extensively processed on ground. However, recent technological developments concerning microprocessors and solid state memories will enable the possibility of on-board SAR data processing. In this scenario, efficient algorithms for generating SAR images are demanded. This new situation requires specially designed algorithms for the processing stages because high-resolution approaches to SAR image generation are still too computationally expensive. We compare and analyse a very efficient SAR processing method for reduced resolution images called spectral analysis (SPECAN) and its variants. This work compares for the first time SPECAN techniques and their variants with other possible candidates. Overall processing evaluation is validated in a simulation environment using ERS-1 raw data. This study compares the computational cost of the algorithms. The conclusion obtained from this study is that SPECAN and especially SPECAN combined with Chirp-Z Transform is a very appropriate candidate for processing SAR data not only in azimuth but also in range. The results show that these new developments are very promising for obtaining fast and simple SAR image generation and they could be suitable candidates for potential on-board implementation.