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In this letter, the concept of high-gain multifunctional antenna based on folded reflectarray antenna (FRA) and polarization-sensitive frequency selective surface (FSS) is proposed. Antenna with multiple functions can be realized by using a polarization-sensitive FSS as the subreflector of FRA instead of the traditional polarizing grid. To validate this concept, a high-gain filtering antenna designed at Ka -band is presented as a design example. Good filtering performance of the antenna has been achieved due to the frequency selective characteristics of FSS. Besides, the relationship between the focal-length-to-diameter ( F/D ) ratio of FRA and the size of FSS element has also been discussed.

A 2-pixel heterodyne receiver working in the 173–205-GHz band is presented in this paper. This receiver prototype is mainly composed of two balanced Schottky-based quadrature mixers and an integrated local oscillator (LO) chain. Based on sub-harmonically pumped mixing and quadrature coupling schemes, the proposed receiver operates in double sideband (DSB) mode or single sideband (SSB) mode. With combination of an external intermediate frequency (IF) 3-dB quadrature hybrid, the receiver can furtherly operate in sideband separation (2SB) mode. E-plane Riblet short-slot couplers combined with probe transitions are firstly employed in the radio frequency (RF) and LO path to realize quadrature configuration simultaneously; detailed theoretical derivation on 2SB operation is also given. The 2-pixel receiver is fabricated and tested, the measured SSB conversion loss of each channel achieves 12–20 dB when pumped with 18 dBm of input power at Ku-band, and the imbalance of conversion loss is less than 2 dB between all the IF ports. The typical sideband rejection ratio (SRR) is 12–16 dB over the operation frequency band. The corresponding achievements are valuable in the follow-up focal plane array detection system.

This paper reports a high-performance 90° waveguide hybrid coupler working in the full W-band. We demonstrate an 8-branch hybrid which features the low amplitude imbalance over a wide band by first increasing the waveguide height inwards and second introducing waveguide height discontinuity sections on the other inner side. Such a compact and robust waveguide hybrid coupler can be implemented in a split-block easily by current computer numerical control milling technology. The measured results show that the reflection and isolation are better than 16 dB, the amplitude imbalance is less than 0.8 dB, and the phase difference is within 90–4.25°/+ 2.38°, which are close to the simulations in most of the W-band.

In this paper, a high-performance waveguide bandpass filter (BPF) operating at W-band is proposed. This fifth-order BPF with a wide fractional bandwidth (FBW) of 20% is realized by adopting strong H-plane offset magnetic coupling, while maintaining a simple and robust structure for the computer numerical control (CNC) milling technology. An extra transmission zero is introduced through the extracted pole method to improve the rejection in the upper out-of-band. The BPF fabricated by aluminum exhibits a low insertion loss of about 0.6 dB in the passband and the 3-dB FBW of 20.2% from 83.6 to 102.3 GHz, which agree well with the simulations. Besides, the effects of tolerance on the filter features are discussed, which indicate that such W-band waveguide filter can be manufactured by the conventional CNC milling technology accurately.

A single-layered triband transmissive/reflective frequency selective surface (FSS) with incident angle up to 80° and polarization stability is designed, simulated, and measured. The periodic element includes a compact hexagonal arrangement of Y-slot and Y-patch, which can effectively reduce unit spacing to 0.16 $\lambda $ . Compared with the conventional hexagonal arrangement, compact arranged Y-unit has a larger band range from 1 to 40 GHz using grating lobes suppression. Controllable passband in X -band and reflectband in Ku -band and Ka -band are proposed. Transmission loss is less than 1 dB in 9.41 GHz in bandwidth of 5% when the incident angle is from 0° to 80°, while the return loss in bandwidth of 5% when 14.5 and 35 GHz is less than about 1 dB when incident angle range is from 0° to 80°/60° for dual polarization, respectively. Hyperboloid FSS is simulated, and performance of transmission and reflection is good. To the best of our knowledge, this is the first report of single-layered FSS that simultaneously operates for angle of incidence more than 60° in X/Ku/Ka -bands for dual polarization.

In this letter, a novel high-isolation 35/94-GHz dual-frequency orthogonal Cassegrain antenna is designed. The antenna consists of a D = 800 mm main reflector, a subreflector, and a dual-band orthogonal-polarization feed. In order to get similar feed horn's E – H radiation patterns and similar phase center positions at the dual frequencies separately, the dual-mode conical horn is designed in the feed. For obtaining a high isolation, a three-order low-pass filter is designed in the Ka-band waveguide feed port. The measured antenna gains are 43.6 and 51.3 dBi, and the sidelobe levels are −27.5 and −26.5 dB at 35 and 94 GHz, respectively. The isolation between the two ports is −61.0 dB in the Ka-band and −63.5 dB in the W-band. The proposed antenna is a suitable candidate for a dual-band radar system.

Local oscillator (LO) sources with sufficient output power are indispensable modules in submillimeter wave heterodyne detectors. In this work, we report on the design and characterization of a ×6×2 frequency multiplier chain that covers 176-196 GHz band. The LO chain mainly includes a W-band active times-6 frequency multiplier, a commercial W-band isolator, a W-band power module, a W-band band-pass filter (BPF) and a varactor-based G-band power-combined frequency doubler. First of all, design and performance of the W-band sextupler (×6), power module and BPF are briefly introduced. This is followed by a detailed description of the G-band frequency doubler as the key content. The final stage doubler employs two 50 μm thick quartz circuits and two commercially available varactor diodes. A circuit scheme named power-combining frequency multiplication is used for the doubler design. This circuit scheme is able to double the power handling capability of the frequency multiplier compared to the un-combined one. Therefore, the final stage doubler can fully make use of the driving power delivered by the power module to increase the output power. Each module is fabricated and assembled, and the discrete modules and the cascaded chain are measured, respectively. At room temperature, when pumped with 0 dBm at Ku-band, the LO chain produces at least 12.5 dBm in the 172-196 GHz band with a measured peak power of 16 dBm at 178 GHz. This power level is sufficient to pump a 0.36 THz heterodyne detector and makes it possible to deploy multi-pixel heterodyne imaging arrays in this frequency range.

In 1991, we developed a new type of quasi-optical power combiner, called a compound quasi-optical power combiner, at Ka-band. In this paper, the circuit of such a compound quasi-optical power combiner is analysed. Its equivalent circuit model is proposed. The circuit equations, the balance condition, the injection locking and the stabilized condition of the compound quasi-optical power combiner are studed by the equivalent circuit model. As an example, a compound quasi-optical power combiner which consists of two single—cavity, two—device power combiners is analysed

In this paper, the new technique of harmonic power combination—millimeter -wave quasi-optical harmonic power combination is presented. In this technique, by compounding several closed resonators with a quasi-optical open resonator, the harmonic powers of active devices are combined, which takes effectively respective advantages of closed cavity power combination and open cavity power combination and improve the combination efficiency of multiple-device harmonic power combiner. The experimental results for W-band are given and shown this combination method is available.

In this paper, a new kind of solid-state quasi-optical power combiner is presented. It consists of two or more singlecavity multiple-device power combiners and a Fabry-Perot cavity. The experimenal results using six Gunn diodes at X-band show that the total output power is higher than 400 mW, the total combining efficiency is as high as 83%, and the frequency stability is better than 10−5.