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In this paper, a novel integrated mode composite transmission line (IMCTL) is proposed, which consists of inner and outer transmission lines. The proposed IMCTL takes full advantages of both substrate integrated waveguide (SIW) and spoof surface Plasmon polaritons (SSPPs) transmission line and supports high-frequency transmission in the inner transmission line and low-frequency transmission in the outer surface transmission line with different propagation modes. The dispersion characteristics of the inner and outer surface IMCTL are studied. The electromagnetic field (EM) distributions and propagation modes of the inner and outer surface IMCTL are examined. The circuit models of the inner and outer surface IMCTL are discussed and analyzed. In order to achieve the transmission of inner and outer surface IMCTL with different propagation modes, two simple high-efficiency conversion structures are utilized to convert the guided waves to the proposed IMCTL. The inner and outer surface IMCTL are designed and simulated, which show good transmission performance. The ohmic losses and dielectric losses of the inner and outer surface IMCTL are simulated and compared with typical transmission lines. The measured data of the proposed IMCTL show a very good agreement with the simulated results. The measured insertion losses of inner IMCTL are within 1.77 ± 0.64 dB from 5.5 to 10.0 GHz and the measured insertion losses of outer surface IMCTL are within 3.21 ± 1.22 dB from 2.0 to 6.0 GHz. The proposed IMCTL will play an important role in the integrated high-performance multiband microwave and wireless communication systems.

A new RF coil based on microstrip Yagi-antenna for 7T magnetic resonance imaging (MRI) is presented in this paper. The RF coil element consists of a driver which is a pair of dipoles printed on the dielectric substrate and two reflectors distributed on either sides of the driver. Simulation results show that the proposed 8-channel RF coil array with these elements has high magnetic field intensity and uniform magnetic field distribution in the transverse plane, and can also maintain relatively low specific absorption rate (SAR) in the human body electromagnetic model. In addition, by comparing the RF field distribution of healthy organs and diseased organs, the feasibility of 8-channel RF coil array for human body imaging in MRI system is confirmed.

This paper presents a textile-based, embroidered inductive strain sensor that can be fabricated with standard embroidery processes and aesthetically integrated with apparel and garments fabrics. The sensor consists of two embroidered coupling coils (called coupling planar coils, or CPC) connected in series, and stacked on top of each other. The mutual inductance of this coupling coils pair is determined by the relative positions and displacement between them. This structure can be used as a restorable and repeatable strain sensor for human movements and activities, such as the measurement of respiratory rate. This structure can also form a passive sensor by using the coils as antennas to connect with RFID/NFC chips, such that the sensing information can be extracted wirelessly as phase and amplitude variations by RFID/NFC readers. Experiments demonstrate that a wearable belt embedded with this proposed sensor can be worn on human body to monitor breathing activities reliably under normal wearing conditions. The sensor structure can be fabricated by commercial embroidery machines using off-the-shelf conductive yarns and all the materials are commercially available in large quantity; therefore, it also has good potentials to be commercialized as a low-cost health monitoring system in mass production.

Textile-based antennas that can be embroidered directly onto cloth fabrics have shown great potential for wearable applications. However, the performance of the embroidered antennas are significantly affected by the materials used, as well as the geometrical variations and deformations. In this paper, we analyze several factors that affect the performance of embroidered antennas, including the choice of geometry, the bending and elongation of tags, as well as the resistivity of the yarns for embroidery. Modeling, simulation, and measurement have verified our analysis and demonstrated that slotted-patch UHF RFID antennas fabricated with low resistance yarns are more sensitive to geometrical variations, such as bending and curving. RFID tags equipped with this embroidered antenna can be utilized as a battery-less passive deformation sensor for human movements.

Embroidered UHF RFID antenna enables seamless integration of RFID tags with apparels. In this paper, we show that the resonant frequency and sensitivity of embroidered meander line dipole (MLD) antennas will vary with the elongation of antenna geometry. We further propose that by exploiting this property, embroidered antenna can also be utilized as a stretch sensor. Prototype tags with embroidered antennas have been tested and proved that by reading the RFID tags' back-scattered signals, the reader can extract the elongation information caused by the stretching of well-performed embroidered RFID tags.

In this paper, we have designed and assembled a Ka-band power amplifier. Working in the frequency range from 34 to 36 GHz, its highest saturation output power is up to 0.36 watts (25.5 dBm). We can estimate the highest power combining efficiency of the Ka-band power amplifier is up to 85%.

In this paper, an equivalent-circuit model including detailed parasitic parameters of a planar anti-parallel GaAs Schottky diode is proposed for Terahertz application. The 3D electromagnetic model is established according to the actual geometry of diode to extract diode parameters simultaneously. Combined with empirical equivalent circuit model, equivalent circuit model and 3D electromagnetic model, the parameters of diode can be extracted completely and accurately. These models can be used for the design of terahertz circuits.

A novel substrate integrated waveguide filter with four symmetrically arranged square complementary split-ring resonators(CSRRs) etched on the SIW surface is presented in this paper. A device which has excellent selectivity with compact size and a novel structure has been desgined, fabricated and measured. The HFSS simulation results show that the filter has good passband performance, and the out of band rejection is relatively high. The circuit area of the band-pass filter is just $17 \times\ 15\mathbf{mm}^{2}$ . The proposed filter demonstrated a minimum passband insertion loss of 2.53dB and a bandwidth of 2.06% at a center frequency of 5.82 GHz by measurement. The filter implementation showed a rejection which is larger than 50 dB at the stopband. The measured results are in good agreement with the simulation.

A substrate integrated waveguide filter with two reversely arranged square complementary split-ring resonators (CSRRs) etched on the SIW surface is presented in this paper. The proposed filter allow the implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the substrate integrated waveguide. The circuit area of the bandpass filter was only 16 × 16 mm. The proposed filter demonstrated a minimum passband insertion loss of 3.5dB and a bandwidth of 5.5% at a center frequency of 5.15 GHz. The filter implementation showed a rejection which was larger than 37 dB at the stopband.

In this paper, a novel compact ultra-wideband (UWB, 3.1 GHz-10.6 GHz, defined by U.S. Federal Communications Commission) band-pass filter with good transmission characteristic and flat group delay is presented by using multiple-mode resonator (MMR) and open stubs. The proposed structure consists of a main multiple-mode resonator and four open stubs. The dimension of this structure is 10 mm × 2.2 mm (not including the 50 Ω microstrip), which is much less than conventional structure. By properly optimizing the parameters of the multiple-mode resonator and open stubs, four resonator modes can be allocated within the UWB band. It can cover the frequency band of 3.1 GHz to over 11 GHz and has 3-dB bandwidth of more than 110% that can satisfy the requirement of UWB band communication system.

The direct frequency synthesizer has advantages of excellent frequency stability, low phase noise, but it is difficult to suppress its spurious signals very well. This paper describes a optimized circuit scheme of direct frequency synthesizer, which output power up to 15 dBm, spurious signals suppression reaches −55dBc and the phase noise at 1kHz offset from carrier is about −90dBc/Hz.

In this paper, a compact wideband low-noise amplifier (LNA) is proposed, where the lumped component is employed as the matching network. Both the simulation and measurement verifies that the improved performance is achieved compared with the conventional LNA. Concretely, the operating frequency band of the proposed LNA is from 30MHz to 1500MHz with its noise figure (NF) smaller than 1.2dB and the voltage standing wave ratio (VSWR) below 1.5, the gain of the LNA is above 16dB while pass-band fluctuation is smaller than 2dB.

A novel slot-shaped defected ground structure (DGS) on the microstrip line to provide a band-rejection property with an improved Q factor is proposed in this paper. It has a size of only 11% of conventional dumbbell DGS unit section and 26.8% of U sharp DGS unit section, while the Q factor is 7.6 times than dumbbell DGS and 3.2 times than U-sharp DGS at the same resonant frequency of 4.88 GHz. A minimized two-pole bandstop filter based on the newly proposed DGS is designed and simulated. It has a 3 dB cutoff frequency of 3.38 GHz with 37 dB rejection in the stopband from 3.63 to 3.75 GHz, the size of the filter is less than 0.35 lambdag times 0.16 lambdag.

A novel patch-shaped patch loaded slotline (PLS) to provide a band-rejection property with an improved Q factor is proposed in this paper. It has size of only 28% of conventional dumbbell PLS unit section and 72% of the conventional open-loop PLS unit section, while the Q factor is more than 10.5 times than dumbbell PLS and 3.3 times than the conventional open-loop PLS at the same resonant frequency of 33 GHz. High Q bandstop filters based on the newly proposed PLS with two and three sections are designed and simulated. Both filters have sharp cutoff frequency and high attenuation in the stopband.

This paper presents a highly integrated chip set for low-cost Ka-band receiver applications. The receiver consists of a low noise amplifier (LNA), an image rejection mixer (IR mixer), a quadruple and a medium power amplifier. A Ka-band receiver module is realized using this kind of chip set, and is got a good performance.