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The occurrence of passive intermodulation (PIM) is inevitable in high-power microwave devices. It interferes with wireless communication and radar systems, resulting in severe deterioration of receiving performance. So far, narrowband PIM analyzers have been realized for different business bands. However, they are incapable of testing wideband systems. To solve this problem, rack-mounted analyzers piled with multiple narrowband analyzers were implemented. While such solutions significantly increase the volume, cost, and power consumption, they cannot provide a wide, continuous bandwidth for PIM localizations. Aiming to solve this problem, we propose a novel solution for realizing ultrawideband PIM analyzers. Based on the principle of cooperative radio frequency and baseband (RF-BB) nulling, we demonstrate an experimental prototype working within a continuous frequency band covering three octaves, exhibiting promising potential in PIM testing applications. [ABSTRACT FROM AUTHOR]

Many radio frequency measurement systems require multicarrier signals with coherent phases between carriers with different frequencies. A typical example is the signal generator which is used in multicarrier multipactor (MM) testing systems. In this paper, we propose a new approach for the generation of coherent multicarrier signals based on a state-of-the-art phase-locked loops technique. Different from existing systems that rely on a heavy use of commercial microwave instruments, this generator can be implemented with on-shelf chips and devices. As an example, an ultrahigh frequency band generator is implemented and how to implement the in-system calibration of this generator in an experimental multipactor testing system is demonstrated. Based on the proposed approach, performing a quantitative experimental research on MM becomes affordable for an ordinary microwave laboratory, which may promote the in-depth experimental study in this area. It can also be used in a wide range of applications such as MIMO and phased array systems. [ABSTRACT FROM AUTHOR]

Passive intermodulation (PIM) potentially occurs in all high-power passive microwave devices. It can severely deteriorate the receiving performance of wireless communication and radar systems. To date, the simultaneous localization of multiple PIM sources in practical microwave devices is still a technical challenge. In this paper, we indicate that if a reference PIM source can be introduced into the standard PIM testing system, and the amplitude and frequency-dependent phase difference between the reference and the real PIM products can be used to construct a k-space multicarrier signal, PIM localization algorithms for both wideband and narrowband devices can be proposed based on the inverse k-space Fourier transform and inverse optimization of the partial multicarrier signal. Simulation and experimental results validate the effectiveness of the proposed approaches. These methods can solve the difficulty of multipoint PIM localization, and can be widely used in the design, production, testing, and troubleshooting of high-power microwave systems. [ABSTRACT FROM AUTHOR]

The newly discovered “long-term” multicarrier multipactors that can be induced by low-energy electric fields potentially threatens the reliability of spaceborne microwave systems. It also causes a new technical challenge to the prediction of the global occurrence threshold of multicarrier multipactors. In this paper, we propose efficient approaches to rapidly compute the fluctuation of space electrons in the evolving process of a multicarrier multipactor, based on which Monte Carlo approaches are developed to efficiently find the global “worst case” waveforms and the occurrence thresholds for both “single-event” and “long-term” multipactors. The proposed approaches can be used for wideband devices, providing an efficient integrated solution for the multicarrier multipactor analysis for practical high-power microwave devices with inhomogeneous field distribution. [ABSTRACT FROM PUBLISHER]

Terahertz technology is one of the research fronts in the microwave society. Among many technical challenges, achieving high-power terahertz radiation has been attracting many efforts. In this paper, we investigate the possibility of power synthesis at low-end frequencies of the terahertz gap based on discrete sources. We show that by applying precision digital phase control, such a power synthesis can be achieved, overcoming the difficulty of phase alignment at these frequencies. For demonstration, we implement a 110-GHz prototype system employing solid-state impact avalanche and transit time diodes. Using a simulation- and measurement-based design methodology, the impedance matching of the designed cavity is able to be simultaneously obtained at both the RF bias and the 110-GHz frequency without using any absorbing material. Detailed design, simulation, and measurement of the prototype are introduced and the experimental results comply well with analytical expectations. Analysis shows that with increased wide digital bit width, the proposed approach is able to provide sufficient phase control precision, making it possible to be used in the power synthesis applications at low terahertz frequencies. [ABSTRACT FROM AUTHOR]

Waveguides using a slab of left-handed metamaterial (LHM) adjacent to a slab of right-handed material (RHM) have shown backward coupling properties over the frequency range in the LHM passband where both permittivity and permeability are negative. In this letter the authors further show that when both slabs are LHMs with different passbands, the resultant backward coupling frequency band is a union of both passbands. The curious fact that the stop band of a metamaterial where permittivity is negative and permeability is positive can support propagating wave is shown theoretically. Backward couplers are demonstrated experimentally to have wideband and dual-band properties by judiciously choosing LHM-LHM and LHM-RHM slabs. This proposed method offers flexibility in producing wideband/multiband coupling and can be used to design and fabricate microwave devices. [ABSTRACT FROM AUTHOR]