In this paper, we propose and demonstrate time-modulated patch antennas able to exhibit opposite polarization ellipticity when operated in transmission or reception, effectively leading to nonreciprocal polarization responses. To this purpose, we merge a patch antenna fed from four symmetrical sides with a low-frequency time-modulation scheme. This configuration exploits the photonic Aharonov Bohm effect to individually manipulate the phase of surface currents flowing along orthogonal directions on the antenna with the phase of the modulation signals. The polarization states of the radiated/received waves can easily be calculated using diagrams in the Poincaré sphere together with the phase difference of the modulating signals. Experimental results at 2.2 GHz demonstrate high conversion efficiency in the time-modulation process, isolation levels over 40 dB in transmission/reception mode, and tunability to generate/receive electromagnetic waves with arbitrary polarization ellipticity. Our findings may enable exciting applications in full-duplex communications as well as in polarimetric radar, sensing and imaging systems.

Processing ground penetrating radar data to obtain well-focused images for object detection has been an active research area. Phase-shift migration (PSM) is a widely used method since it allows the wave velocity to vary with respect to multi-layer medium. However, this requires pixel-by-pixel calculation of the image, which is time-consuming. This paper presents an extended Omega-k algorithm for multi-layer medium imaging with significantly less computation complexity than the PSM algorithm. The extended Omega-k exploits fast interpolation in the wave-number domain instead of iterative calculating as done by PSM. The method of estimating the wave propagation velocity in different media is also proposed via vertex region extraction for phase compensation and image focusing. Various images of buried targets of a two-layer medium experiment are obtained, which validate the effectiveness of the proposed algorithm, and make it practical for some typical ground-based surveillance applications.

A new class of wideband bandpass filters based on using thick metallic bars as microwave resonators is presented in this work. These bars provide a series of advantages over fully planar printed technologies, including higher coupling levels between resonators, higher unloaded quality factors QU, and larger bandwidths implemented with compact structures. In comparison to dielectric and waveguide resonators filters, higher bandwidths together with lower weight and footprint reduction are achieved with the proposed thick bars technology. Moreover, thick bar resonators can easily be coupled to an additional resonance excited in a box used for shielding, allowing to realize transversal topologies able to implement transmission zeros at desired frequencies. To illustrate the capabilities of this technology, three microwave filters with different topologies have been designed. One of the designed filters has been manufactured and tested using copper bars inside an aluminum housing partially filled with Teflon. Measured data demonstrates a fractional bandwidth of FBW = 32%, spurious free range SFR > 50%, unloaded quality factor of QU = 1180, insertion losses over 0.16 dB and return losses over 20 dB, without requiring any post-tuning operation on the prototype. This result confirms the exciting performance of the proposed technology for wideband applications.

We propose the concept and design of a time-modulated antenna able to exhibit nonreciprocal polarization handedness during transmission and reception (for instance, the antenna radiates right-handed circularly polarized waves but receives left-handed circularly polarized waves) by exploiting the photonic Aharonov-Bohm effect. To demonstrate our approach, we combine a patch antenna fed from four symmetrical sides with an appropriate low-frequency modulation scheme to control orthogonal currents. We show that it is simultaneously possible to (i) obtain very high frequency conversion efficiency; (ii) independently tailor the phase of radiated fields that have orthogonal polarization with the phase of certain modulation signals, thus implementing any polarization state of the Poincaré sphere; and (iii) achieve nonreciprocity at the polarization level with a single antenna element. We envision that the proposed time-modulated device may find exciting applications in the next generation of sensing, radar, and communication systems.

This paper presents a 212-GHz fundamental VCO with a $\Pi$-embedding network with high dc-to-RF efficiency. Particle swarm optimization method is utilized to find the optimal values of elements of the lossy embedding network. Fabricated in 65-nm bulk CMOS, the VCO achieves 0.6-mW peak output power per transistor at 1-V power supply and the peak dc-to-RF efficiency of 5.3%. The measured phase noise is -92.5dBc/Hz and -113.9dBc/Hz at 1MHz and 10MHz offset, respectively. Bulk voltage is used as the tuning mechanism. The measured tuning rang is 212.2GHz to 208.8GHz when the bulk voltage is changed from 0V to 0.8V.

This paper reports an approach to designing compact high efficiency millimeter-wave fundamental oscillators operating above the fmax=2 of the active device. The approach takes full consideration of the nonlinearity of the active device and the finite quality factor of the passive devices to provide an accurate and optimal oscillator design in terms of the output power and efficiency. The 213-GHz single-ended and differential fundamental oscillators in 65-nm CMOS technology are presented to demonstrate the effectiveness of the proposed method. Using a compact capacitive transformer design, the single-ended oscillator achieves 0.79-mW output power per transistor (16 μm) at 1.0-V supply and a peak dc-to-RF efficiency of 8.02% (VDD=0.80 V) within a core area of 0.0101mm2, and the measured phase noise is -93:4 dBc/Hz at 1-MHz offset. The differential oscillator exhibits approximately the same performance. A 213-GHz fundamental voltage-controlled oscillator (VCO) with bulk tuning method is also developed in this work. The measured peak efficiency of the VCO is 6.02% with a tuning rang of 2.3% at 0.6-V supply.

A monolithic piezoelectric MEMS-CMOS resonant transformer that can be used in ultra-low-power high-efficiency RF sensing applications is presented for the first time. The MEMS-CMOS resonant transformer is based on a 59 MHz 2-port Aluminum Nitride (AlN) Contour Mode Resonator (CMR) bonded to a 0.18 μm NMOS-based rectifier for voltage boosting and RF-to-DC conversion. The integrated device is fabricated in a foundry-based process by conductive eutectic wafer bonding. To amplify the voltage, the AlN CMR is designed to attain a large quality factor (Q=1150) and a relatively low dielectric capacitance (C 0 =1.51 pF) in relation to the number of rectifier stages (n=20). As a result, a ten-fold voltage gain MEMS-CMOS resonant transformer is demonstrated in this work.

Wake-up receivers have been proposed to provide continuous sensing in a wide variety of Internet of Things applications. To achieve impedance transformation and passive amplification between the antenna and rectifier node, current wake-up receivers employ large magnetic transformers that exhibit both low Q and inductance per unit area in planar CMOS technology. The adoption of piezoelectric MEMS resonators to replace magnetic transformers offers an area-efficient, high-Q, monolithic solution that allows large voltage amplification for ultra-low-power applications. AlN Contour Mode Resonators (CMRs) are an emerging class of piezoelectric MEMS that offers frequency reconfiguration via lithography.

We present a tunable high-Q two pole waveguide bandpass filter at 110 GHz. The demonstrated filter has record performing insertion loss (2 dB) and tuning range (11 GHz) in the W band (75-110 GHz). A sub-micron resolution piezo electric stepper motor is used to actuate a thin film which forms the ceiling of the resonant cavities. This sub-micron actuation effectively tunes the center frequency of the filter. This tunable filter has a variety of uses such as a front-end bandpass filter for multi-band communications, as a filter for rejecting intermodulation products on tunable systems or as a channel select filter.

A 75-110GHz (W band) high-Q tunable band pass filter is demonstrated. The band pass filter has low insertion loss, a Q of approximately 200 and can be tuned across the entire W waveguide band. This filter has a variety of uses including rejecting spurious signals generated from non-linear frequency multiplication and improving signal to noise ratio at the front end of a receiver. The tuning is achieved by actuating a resonant cavity by using a sub-micron resolution stepper motor.

A 330-500GHz (WR2.2) directional coupler is demonstrated. The coupling is achieved by parallel quarter-wavelength gold beams suspended in air over a silicon substrate. The circuit was designed in an “H” shape in order to transition to low loss rectangular waveguide. We present the design and analysis of a WR2.2 coupler with 4dB insertion loss, 10dB coupling factor and 20dB minimum isolation. The techniques we describe can be employed to design high performance, low cost THz components.