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This contribution presents a vertical transition between a WR34 rectangular waveguide (RWG) and two grounded coplanar waveguides (GCPW). It is intended for dual-band phased array applications and thus includes a diplexer. The RWG is the common port and the GCPWs are the diplexed 20- and 30-GHz ports. This yields a very compact design compared to conventional cascaded circuit topologies. The realized component exhibits a port matching and isolation exceeding 10 and 30 dB, respectively, over more than 500 MHz in both bands.

This work presents diplexers realized with folded circular substrate integrated waveguide (FCSIW) cavity filters. The properties of such cavities are analyzed, and empirical equations for calculating the resonant frequencies are given. The analysis relies on an even-/odd-mode decomposition. A 10-GHz filter is designed based on this approach. In the second step, its size is reduced, still maintaining the passband behavior. An asymmetric taper is used to connect two such filters to realize a diplexer. Two diplexers with center frequencies of 10/15 and 12/13.5 GHz are presented. The diplexers are several times more compact than comparable devices reported in the literature. The components are manufactured, and the functionality is demonstrated by simulation and measurements.

This article reports a solid-state power amplifier module in low-temperature cofired ceramic (LTCC) technology. For compactness and low loss, the package utilizes substrate-integrated waveguides (SIWs). To meet the thermal requirements, the amplifiers are mounted on a metallic plate that is integrated into the LTCC multilayer and transfers the heat to a spreader. Both RF and thermal measurement results for a package with two integrated 10-W gallium nitride (GaN) power amplifiers at the K-band are presented. They demonstrate the suitability of the module for highly integrated transmitters as needed for phased arrays or multiple-feed-per-beam satellite antennas.

This article presents a novel broadband septum polarizer with a relative bandwidth (BW) of 37.8%. This is significantly more than the approximate 25% BW of square and circular waveguide polarizers. It is enabled by using an equilateral triangular common port waveguide, which guarantees the largest possible frequency range between fundamental and next higher order mode cutoff. The transition between the triangular section and the rectangular input waveguides, which includes the septum, is designed to accommodate this large BW. The simulation is validated using a polarizer designed for 75–110 GHz and fabricated by conventional precision milling. A second polarizer is realized for the 18-to-26 GHz range by employing additive manufacturing to demonstrate the advantages of this technology in this context. In both cases, the axial ratio remains below 1.3 dB, whereas the input port isolation and the input return loss exceed 17 and 15 dB, respectively.

A compact 20/30 GHz diplexer based on substrate integrated waveguide (SIW) cavities and grounded coplanar waveguide (GCPW) feed lines is proposed. It features additional in-phase reactive power splitting in both passbands by exploiting symmetries. The component is realized in a vertically cascaded configuration using multilayer printed circuit board (PCB) technology, achieving a footprint of only 6×8 mm2. The compactness of the diplexer enables utilization in highly integrated applications such as shared aperture transmit/receive (Tx/Rx) phased arrays.

We present a design approach for a self-biased Ka-band isolator. A pre-sintered barium hexaferrite is integrated in a RO4003C laminate. In combination with a microstrip design this yields a compact and cost-effective component. The operating principle of the isolator and a concrete design example are presented. The experimental work confirms the theoretical expectations and reveals the optimization potential.

This paper reports the realization and measurements of two power amplifier MMICs at Ka-band. Both MMICs were manufactured using an industrial 0.15 $\mu$ m AlGaN/GaN HEMT technology. The power amplifiers MMIC1 and MMIC2 are three-stage designs utilizing a total gate width (TGW) of 5.12 mm and 10.24 mm, respectively. In order to maximize the efficiency, the MMICs exhibit a staging ratio of 1: 2: 6.4. The measurements demonstrate for MMIC18-10.5 W of output power with 28-32% of power-added efficiency (PAE) between 25 and 29 GHz, i.e., over a fractional bandwidth of 15%. In the same frequency band, MMIC2 exhibits more than 15 W of output power and 25% of PAE. The best performance for MMIC2 was measured at 27 GHz and reaches 20 W associated with a PAE of 27%.

The paper investigates experimentally the effect of harmonic terminations on AlGaN/GaN power amplifiers (PA) performance at K-/Ka-band. Two technologies are compared, a 0.25 µm and 0.1 µm process. In both cases, a harmonic termination increases the achievable output power by about 10 % at the expense of bandwidth, whereas the efficiency is improved only in the first one.

This paper studies an integration concept for a self-biased Ka-band circulator. Non-reciprocity is achieved by means of a pre-sintered scandium substituted barium hexaferrite which, as a hard-magnetic material, does not require external magnetic biasing. The ferrite is integrated into a microstrip circuit on a RO4000 laminate. This yields a compact and potentially low-cost circulator. The basic functionality is demonstrated in a first experiment. The results are still quite preliminary, though. Yet, some important conclusions can be drawn regarding the required design optimization measures.

An alternative to wire-bonding and flip-chip interconnects of integrated circuits and printed circuit boards (PCB) is presented. The flip-line interconnect combines the advantages of wire-bonding and flip-chip technology while avoiding their disadvantages. It is especially useful for prototype setups where device inspection and repairability are crucial. The proposed structure is analyzed using full-wave simulation software. It is shown, that in contrast to wire-bonding, the transition length is not critical. A transition from a CMOS chip with a pad pitch of 100 µm to a regular PCB is manufactured. Measurements at W-band (75–110 GHz) reveal a return loss better than 12 dB and transmission above -3.4 dB.

This contribution deals with a 20/30 GHz diplexer intended to feed substrate integrated waveguide (SIW) antennas. As these feature circular polarization, they have a square cross section which is implemented in a thick multilayer. The transition between the thick antenna and the thin front end is part of the proposed diplexer. Realizing it as a step yields a low-loss and very compact component occupying approximately 5 × 8 mm2. The paper describes the structure and reports its design and realization. The functionality is demonstrated in simulation and verified experimentally. The measured insertion loss is 1 dB in the 20 GHz receive (Rx) path and 1.6 dB in the 30 GHz transmit (Tx) one. The port isolation exceeds 30 dB at 30GHz.

The nondestructive characterization of small liquid volumes, as well as the detection of single biological cells, can lead to new insights for biomedical and biotechnological applications. The dielectric permittivity of the sample, which depends on the chemical composition, is detected using electromagnetic sensors in the microwave frequency range. The sensing system proposed here is based on resonant near-field sensors, which are combined with a microfluidic chip. The sample volume of a few picoliters enables single-cell measurements. A novel process featuring a biocompatible polymer material is used for fabricating the microfluidic channel for liquid samples. Two opposed sensing tips are integrated at the bottom of the channel to improve the sensitivity to small dielectric contrasts. They are connected to two resonators, which allows to simultaneously characterize the sample permittivity at two different frequencies. In a proof-of-principle experiment, single cells of the Chinese hamster ovary cell line are detected. This shows that the proposed sensing system is suitable for single-cell characterization due to its high sensitivity and spatial resolution. A potential biomedical application is the systematic investigation of various cell types and states to elucidate potential distinguishing characteristics.

This paper presents requirements and front-end solutions for low-cost communication systems with data rates of 100 Gbit/s. Link budget analyses in different mass-market applications are conducted for that purpose. It proposes an implementation of the front-end as an active antenna array with support for beam steering and polarization multiplexing over the full W-band. The critical system components are investigated and presented. This applies to a transformer coupled power amplifier (PA) in 40 nm bulk CMOS. It shows saturated output power of more than 10 dBm and power-added-efficiency of more than 10 % over the full W-band. Furthermore, the performance of microstrip-to-waveguide transitions is shown exemplarily as an important part of the active antenna as it interfaces active circuitry and antenna in a polymer-and-metal process. The transition test design shows less than 0.9 dB insertion loss and more than 12 dB return loss for the differential transition over the full W-band.

This contribution presents the system design procedure and performance of an array fed reflector antenna. Combining the inherent benefits of a reflector antenna—high gain, low-cost, and simplicity—with the agility provided by a scannable active array feed, enables a new range of applications, for instance in commercial mobile antenna terminals. The whole arrangement features a restricted field of view for either scanning or multibeam applications. To minimize system cost, a planar patch antenna array in printed circuit board technology is used for the feed and the reflector diameter is restricted to 60 cm. To obtain optimal performance, both the reflector and the feed are specifically designed for the desired application, i.e., mobile satellite communication at Ka -band. A comprehensive study of various rotationally symmetric reflectors is carried out to determine arrangements maximizing the field of view and still complying with the respective regulations. For the feed, a 30 GHz transmit array with 49 elements is developed, enabling 2-D scanning in a ±6° conical sector. It includes a wideband signal distribution network and frontend electronics.

Several different microwave circuits, including beamforming networks and balanced amplifiers, make use of 3-dB power dividers and combiners. A well-known architecture able to work over large bandwidths, a critical request for many applications, is based on E-plane three-port waveguide structures, where a lossy element is added to overcome the inherently poor isolation given by lossless three-port junctions. While a standard implementation based on normal rectangular waveguides often results in large and heavy structures, an implementation based on substrate-integrated-waveguide (SIW) technology offers advantages in terms of compactness, weight reduction, cost minimization, and integration possibilities with active stages. This paper presents the design, fabrication, and characterization of two SIW E-plane 3-dB power divider/combiners where the lossy element is realized using a resistive layer. The prototypes cover the entire $X$ -band from 8 to 12 GHz, and the resistive layers are realized according to two different manufacturing techniques to investigate the potentials of both approaches. The optimization of the resistive layer geometry and resistivity, a critical aspect for low-profile SIW circuits, is discussed in detail. In particular, an analytical formula is derived, which allows to determine the optimum values for the resistive layers’ principal parameters, namely the length and resistivity, without the use of full-wave numerical solvers.

A fully differential power divider with ultra-broadband performance is presented. It consists of multi-section Wilkinson power combiners vertically aligned in a multilayer circuit board, which are fed by differential via transitions. The carbon paste decoupling resistors are integrated in the stack. The measured differential-mode output isolation exceeds 10 dB above 2.9 GHz. The excess insertion loss remains below 1.0 dB up to 21 GHz and reaches 2.0 dB at 36.5 GHz. The structure, which is designed for compactness, occupies only 50 mm2.

A vertical transition from differential microstrip line to WR10 rectangular waveguide is presented. In contrast to other approaches, it does not necessitate a backside cavity. This simplifies the integration into multilayer circuits. The measured response which agrees well with the simulated one demonstrates a good performance over the entire W-Band. The insertion loss ranges from 0.5dB to 1.1dB whereas the return loss is better than 13dB over the whole bandwidth of 37.8%.

This contribution deals with a compact substrate integrated waveguide (SIW) diplexer for terminal array antennas at K-/Ka-band. The diplexer connects the transmit (Tx) and the receive (Rx) frontend with an antenna element. It is comprised of a bifurcation and two second order bandpass filters with low insertion loss. The Rx-filter has additionally two transmission zeros in the Tx-band. The structure is implemented in multilayer printed circuit board (PCB) technology. This yields a compact design which can be integrated in an array with half-wave element spacing. The simulated diplexer performance is validated by measurements. The insertion loss in the Rx-band remains below 0.7 dB, while the Tx-/Rx-isolation exceeds 40 dB in a 1.2 GHz band at Tx.

An ultrawideband K-/Ka-band lens antenna for future satellite communication systems is presented. It consists of an extended hemispherical dielectric lens that is fed by a square substrate-integrated waveguide (SIW) and therefore offers a low-cost alternative to horn antennas. The design procedure is explained, and the antenna performance is presented. A sophisticated test fixture is developed to excite the square SIW. The measured ${S}$ -parameters and far-field patterns validate the concept and exhibit more than 13 GHz bandwidth.

A design approach for substrate-integrated waveguide (SIW) to rectangular waveguide (RWG) transitions based on the synthesis of antipodal finline tapers is proposed. The taper is designed using a reflection-based impedance definition as no suitable model is available for antipodal finlines. The characteristics of the finline are determined from full-wave simulation. To demonstrate the proposed method, two SIW-to-RWG transitions are designed and characterized at the $K$ -band. The measured back-to-back transitions exhibit a return loss above 15 dB and an insertion loss below 1 dB between 16.7 and 20.5 GHz and between 21.1 and more than 31 GHz, respectively. A good agreement between the synthesis model and full-wave simulation of the taper on one hand and between simulation and measurements of back-to-back transitions on the other hand is demonstrated.

In this contribution a dual-band, dual-polarized microstrip antenna element for array applications is presented. The patch antenna is designed to operate simultaneously at around 30 and 20 GHz, the up- and downlink frequencies of modern Ka-band satellite communication systems. The antenna is smaller than half the freespace wavelength at 30 GHz to enable its utilization as array element of dual-band ground terminals. Integrating transmitter and receiver circuits allows, in turn, for a very compact active terminal solution. To minimize production cost, the design is carried out in standard multilayer printed circuit board technology. The antenna features two distinct polarization ports suitable for either dual linear or dual circular polarization if both ports are excited in quadrature. The single antenna design process is described in detail and simulation and measurement results are presented. Finally, different arrays based on this patch antenna are evaluated by simulation and measurements.

This paper reports on recent progress in the field of terminal antennas for Ka-band satellite communications, the focus being on mobility scenarios requiring beam steering agility. Selected European activities are briefly reviewed, before a more in-depth view of ongoing work performed at the Hamburg University of Technology is given. Three different approaches are reported.

This paper describes the development of ultra-broadband compact power dividers for the frequency range from 2 to 40 GHz. A multi-section approach with reduced line lengths of the successive sections is used to achieve this large bandwidth at a minimal size. The resistors needed for an acceptable isolation are manufactured by lithographically structuring a conductive paste on top of microstrip lines. Thus, the entire device is planar and enables the integration in multilayer printed circuit board (PCB) stacks. The design is demonstrated with a three (five) section divider, which occupies less than 5 mm2(16 mm2) of surface area. The insertion loss is below 3.8 dB (4.7 dB) from 1 to 40 GHz, while all ports exhibit more than 10 dB match. The isolation exceeds 10 dB above 6 GHz (2.5 GHz).

A multilayer dual-band dual-mode bandpass filter with widely spaced passbands and using two independent square loop resonators is proposed. For improved stopband characteristics, the spurious second harmonic passband of the low frequency resonator is suppressed. The passbands are centered around 3 GHz and 9.35 GHz for application in a dual-frequency maritime radar. The simulated and measured results show good agreement.

A dual-band transmit-receive module for a new commercial maritime radar with digital beamforming is presented. The module is realized in a low cost approach. It consists of two RF-stages, one at S- and one at X-band, and a shared IF-stage. The cost is kept low by using components of the shelf and a novel integration technique for low-cost circulator. The transmit-receive module exhibits a transmit power of 28.7 dBm in the S-band and of 29.7 dBm in the X-band. The system noise figure is 2.9 dB and 7.5 dB, respectively.

A dual-polarized dual-frequency antenna module for a future commercial navigation radar is presented. The module is comprised of three X-band antenna columns as well as one S-Band antenna column. All antennas feature dual-polarization capability and are the basic antenna cell for a full phased array realization of the radar system.

Two power amplifier (PA) MMIC designs with more than 1W of output power in the 37.5–42.5 GHz Q-band downlink band are presented. The circuits are manufactured using the Fraunhofer IAF 100 nm AlGaN/GaN process. The first one is a two-stage design in microstrip line (MSL) technology, whereas the second one is a three-stage design in grounded coplanar waveguide (GCPW) technology, which enables effective output power combining and compact layout at Q-band. A maximum output power of 2.1 W (33.2 dBm) is measured at 39 GHz with a power-added efficiency (PAE) of 14.7%, corresponding to a power density of 1.45 W/mm.

The nondestructive characterization of biological liquids and cell suspensions using electromagnetic waves in the microwave frequency range calls for accurate and sensitive measurement devices. Especially when reducing the sample volume, the sensitivity becomes a critical design parameter for broadband sensors. In this paper, a miniaturized transmission-line sensor based on a coplanar waveguide is used to characterize the permittivity of nanoliter volumes of biologically relevant liquids and cell suspensions. The sensor’s sensitivity is increased by means of electrically small discontinuities within the sensing section. The biological samples are guided across the sensor in a microfluidic channel, which is fabricated using microsystems technology. The sensor is used between 850 MHz and 40 GHz to detect the broadband permittivity of liquid samples such as aqueous salt and protein solutions. The experimentally detected contrast between living and dead Chinese hamster ovary cells in suspension is significant despite the small sample volume.

A dual-polarized X-band antenna module for a maritime navigational phased array radar is introduced as part of a dual-band array. The module is comprised of three column arrays with five patch antennas each. The design of layer stack, unit cell, and distribution network is detailed. Measurement data and simulation results are presented. The antennas contained on the module achieve up to 10.3 dBi gain.

A dual-band and dual-polarized antenna element for K/Ka-band satellite communication systems is presented. An orthomode transducer (OMT) excites circular polarization in a square substrate integrated waveguide (SIW), that feeds an extended hemispherical dielectric lens. The feed structure is composed of a multilayer printed circuit board (PCB) and tapered superstrates. The design procedure of the components is explained and the antenna performance is presented. The measured scattering and far-field parameters validate the concept.

A novel type of substrate integrated waveguide (SIW) tapers in a multilayer stackup is presented. A simple and fast synthesis method is developed. The taper is modeled as a nonuniform transmission line with varying waveguide characteristics. These are determined using a transverse resonance method (TRM), which is extended to calculate a characteristic impedance. The synthesis procedure is explained and the results are compared to full-wave simulation. Measurement results of compact, ultra-wideband, and low-loss tapers at K/Ka-band validate the concept.

Hybrid integration often requires to connecting components with different contact footprints, typical examples being MMICs versus larger drop-in devices. In microstrip technology this calls for different line widths and substrate thicknesses. This paper proposes a novel transition between two microstrip lines of different width and height. The basic concept of the multilayer approach is to gradually adapt the field distribution along the transition while keeping the impedance constant. In simulation the optimized transition exhibits an impedance match in excess of 20 dB from DC to 20 GHz. For verification a back-to-back transition is fabricated and measured. It features more than 13 dB input match and an insertion loss below 1 dB in a bandwidth up to 20 GHz, and the results being in good agreement with simulation.

Traveling wave tubes (TWTs) operating at S-band are to be improved by suppressing the second harmonic frequency. Among the different possibilities, two techniques, namely harmonic injection and a filter helix for frequency selective signal suppression, are studied in more detail and applied to S-band tubes in both simulation and measurement. In addition, their suitability to improve tube performance by reducing the second harmonic is discussed. Moreover, filter helix implementation in TWTs with an arbitrary pitch profile along the interaction area is considered. In this context, the dependence of the pitch discontinuity reflection coefficient on several filter helix parameters is investigated. The influence of those parameters on the filter performance is shown by filter helix optimization. Measurement results of the optimized filter helix TWT are presented.

The implications of different matching conditions for coupled-cavity traveling-wave tubes are considered. Using a small-signal approach the characteristic impedance for the coupled (hot) beam-wave system is derived. It is taken as reference impedance to model ideal transformers and severs. This matching condition is compared to the standard cold match and both cases are analyzed using a large-signal interaction tool. The implications on input reflection and output gain are discussed.

Increasing the efficiency of traveling wave tubes (TWTs) is a basic development strategy. In this paper, second harmonic suppression is introduced as a possible mean. For this purpose, a filter consisting of periodic pitch discontinuities is implemented in the helix transmission line (TL) of a tube. A method is developed to obtain the reflection coefficients of adjustable pitch discontinuities. A filter design for a low frequency TWT is tested in a helical TL without electron beam and implemented in the tube. Both simulation and measurement confirm a stopband at the second harmonic and thus a significant reduction of this harmonic at the output. An additional filter is designed and tested at S-band. It is shown to improve both the output power and the linearity of the tube.

This letter introduces a theory which considers the effect of lossy second-harmonic terminations on the voltage waveform, output power, and efficiency of power amplifiers (PAs) operated in the class-J mode. To this end, the conventional (reactive) class-J mode is extended to a resistive-reactive class-J mode with complex fundamental and second-harmonic load impedances. The theory is experimentally validated by performing on-wafer active load-pull measurements on an AlGaN/GaN HEMT power device with $0.25~\mu{\rm m}$ gate length and a total gate periphery of $6\times 200~\mu{\rm m}$ . The measured waveforms are de-embedded to the internal current-generator of the device, where they exhibit the theoretically predicted behavior.

Resonant substrate integrated near-field sensors are used for characterization of aqueous solutions at three different frequencies. In addition, Chinese hamster ovary (CHO) cells in a culture medium are characterized with the same sensors. Different concentrations as well as different vital states of cell suspensions are examined. The complex permittivity of the samples is evaluated using a linearized method based on perturbation theory. The permittivity differences between the measured cell suspensions are discussed. The resonant frequencies of the sensors are close to 3, 7, and 11 GHz, respectively.

In this study scandium-doped barium hexaferrite thin-films intended for self-biased nonreciprocal devices are produced by means of the sol-gel method on alumina substrate. The scandium doping factor is varied between x = 0:025 and x = 0:4. X-ray diffraction analysis and the measured hysteresis curves are shown for both doped and undoped films. For broadband microwave characterization the thin-films are deposited on coplanar waveguides. In experiments the ferromagnetic resonance frequency is shown to be adjustable from 43:2 GHz to 27:1 GHz by increasing the scandium-doping level and nonreciprocal behavior is demonstrated.

We present the design of a self-biased Y-junction circulator for Q-band applications. It relies on barium hexaferrite thin-films deposited by means of the cost-effective sol-gel method. The potential of the approach is first investigated in simulation based on a realistic material description. From this, critical design parameters are identified. This is followed by an experimental study. First encouraging practical results are reported. Steps for further performance improvements are discussed.

The next generation of satellite communication systems at Q/V-band increases the need for highly performing MMIC technology. Gallium nitride high electron mobility transistors (GaN HEMTs) can provide high power density even at millimeter wave frequencies. Targeting a band of 35–40 GHz, a power amplifier MMIC using second-harmonic input and output matching is designed, manufactured, and measured. The presented single-transistor MMIC exhibits a small-signal gain of more than 9 dB at 38 GHz and delivers 269 mW (24.3 dBm) of output power at 38 GHz, which results in a power density of over 1.2 W/mm. The amplifier shows a drain efficiency of up to 33 % and a power-added efficiency (PAE) of up to 22 %.

A single-pole double-throw (SPDT) switch for a dual-band radar duplexer at S- and X-band is presented. The switch is particularly useful for monostatic phased array radars where a high isolation between transmitter and receiver is necessary. It consists of three PIN-diodes and needs only one switching voltage. A high isolation and a low insertion loss combined with the potential for a high power handling capability are achieved by utilizing an asymmetric PIN-diode network with shunt diodes in the transmit and a series diode in the receive path. The isolation is improved at both frequency bands by compensating the parasitic capacitance of the series diode. Simulation and measurement results are presented. The fabricated switch exhibits an isolation of more than 30 dB and an insertion loss of less than 1.4 dB in the transmit case.

A compact 20 GHz/30 GHz diplexer for satellite communication systems is presented. It consists of a T-junction and two bandpass filters implemented in substrate-integrated waveguide (SIW) technology. The 30 GHz filter relies on a standard design, whereas a wide stopband approach is used for the 20 GHz filter to suppress a parasitic passband at the upper frequency. The design procedure is explained and simulation as well as measurement results are presented. The complete diplexer is fabricated in a standard PCB process. The measurement results validate the approach.

A matched load in substrate integrated waveguide (SIW) technology is presented at K-band. An embedded resistive thick film is used to absorb the input signal. The proposed structure is fully compatible with standard multilayer printed circuit board processes. The realized SIW termination exhibits a bandwidth of 2.75 GHz with a return loss of more than 20 dB around 18.4 GHz.

Architectures for active multiple-feed-per-beam satellite antennas with power amplifiers shared between adjacent beams are presented. Different concepts for sharing solid state power amplifiers (SSPAs) to reduce required power margins for a K-band scenario are proposed and compared. In scenarios with data traffic and rain attenuation unequally distributed across the beams the overall efficiency can be increased.

The design, realization, and characterization of a K-band high power amplifier with a saturated output power of 40dBm is described in this paper. The amplifier is realized using a 250nm gate length AlGaN/GaN HEMT MMIC technology on semi-insulating SiC substrates. The two-stage amplifier is designed with two 6×90 µm HEMT cells in the driver and four 8×100 µm HEMT cells in the final stage and thus exhibits a relatively aggressive staging ratio of 1∶3. When measured with a supply voltage of 32V, the amplifier delivers a saturated output power of 40dBm at 18 GHz. The peak PAE at this frequency is 30%, and the linear gain exceeds 20 dB. These results are state-of-the-art performance with regard to power/efficiency at K-band.

A small-signal model for the gain estimation of traveling-wave tubes with folded-waveguide delay lines is derived from perturbation theory. The model extends an existing formulation from literature, and increases its accuracy significantly. The results are compared to full-wave particle-in-cell simulation.

A Q-band folded-waveguide delay line is presented which is loaded with nose cones that are intended to increase the beam-wave coupling in a traveling-wave tube. The fabrication process is briefly outlined and one-port measurement results are evaluated to compare the dispersion with full-wave results. The results prove the concept of field enhancement due to the nose cones with an acceptable increase in manufacturing complexity.

A modified folded-waveguide (FW) delay line for traveling-wave tubes (TWTs) is proposed. The amplifier performance is assessed by full-wave and interaction simulation. Properly designed nose cones are shown to enhance the beam-wave coupling. This, in turn, improves the amplifier gain, a weak point of conventional FW-TWTs. The achievable beam efficiency is increased without sacrificing too much bandwidth.

The ongoing developments of satellite antenna technology, mainly of multiple-feed-per-beam (MFB) concepts, combined with advanced compound semiconductor and packaging technologies that provide the building blocks for a new generation of K-band satellites, are reported. This paper proposes a next-generation MFB application scenario using the advantages of both new antenna and solid-state power amplifier concepts.