@article{shen_ricketts_2020, title={Compact W-Band "Swan Neck" Turnstile Junction Orthomode Transducer Implemented by 3-D Printing}, volume={68}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2020.2992065}, abstractNote={A turnstile junction orthomode transducer (OMT) provides polarization separation/combining on a full waveguide bandwidth; however, it bears a complex connecting structure, which accordingly leads to a bulky volume. We present a compact W-band (75–110 GHz) OMT using a “swan neck” twist for the connection between a turnstile junction and an $E$ -plane Y-junction, for minimizing the overall OMT structure. The core volume for the proposed OMT is $9\times $ less than the previously reported stacked-layer OMT. The compact W-band OMT was built by digital light processing (DLP) 3-D printing technology and was postmetallized by silver electroless plating. The return loss of the vertical-polarized port (V-port) and the horizontal-polarized port (H-port) is characterized, as averagely 17 and 15 dB, respectively. The measured average insertion loss from H- and V-ports to the common port is 0.5 and 0.6 dB. The measured isolation between V- and H-ports is averagely 28 dB. Furthermore, the turnstile junction asymmetry along the central axis was revealed in computed tomography (CT) scanned images. The simulation shows a negative effect of the asymmetric structure on the OMT isolation. In addition, the dual-polarized (dual-pol) antenna combining such OMT and a corrugated horn was realized in a compact size. The cross-polarization level of the OMT, characterized in a far-field test of this dual-pol antenna, is averagely −18 dB at the W-band.}, number={8}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Shen, Junyu and Ricketts, David S.}, year={2020}, month={Aug}, pages={3408–3417} }
 @article{shen_ricketts_2019, title={Additive Manufacturing of Complex Millimeter-Wave Waveguides Structures Using Digital Light Processing}, volume={67}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2018.2889452}, abstractNote={Additive manufacturing technology has enabled the manufacturing of complex structures, especially those with intricate internal features. This paper proposes a method for building complex-structured millimeter-wave waveguides using a strategy that combines digital light processing 3-D printing technology, a curved corner design, an off-axis print angle of 45°, and a robust postmetallization process. To demonstrate the capability of this combined-strategy method, a traditional magic tee prototype and an adapted inherently matched magic tee prototype are fabricated for use in the W-band. The measured performance of the fabricated inherently matched magic tee demonstrates return loss better than 13.5 dB, isolation coefficients higher than 15.7 dB, insertion losses smaller than 1.3 dB, and a magnitude imbalance of less than 1.3 dB across 80–105 GHz. The 3-D printed magic tee has a comparable performance to a W-band CNC-machined magic tee but weighs 77.5% less than the metallic one.}, number={3}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Shen, Junyu and Ricketts, David S.}, year={2019}, month={Mar}, pages={883–895} }
 @article{mao_shen_gui_2018, title={A Study on Deep Belief Net for Branch}, volume={6}, ISSN={["2169-3536"]}, DOI={10.1109/access.2017.2772334}, abstractNote={Since 2006, there have been significant advances in deep learning algorithms, and they have shown superior performance in audio and image processing. In this paper, we explore the feasibility of applying deep learning algorithms to branch prediction. We treat branch prediction as a classification problem and compare the effectiveness of deep learning with existing branch predictors. We make several interesting observations from our study. The first is that for branch prediction, the deep learning algorithm based on deep belief networks outperforms the prior work, but only outperforms state-of-the-art branch predictors, such as the TAgged GEometric length (TAGE) predictors, for several benchmarks. Compared with the much simpler perceptron branch classifier, the deep learning classifier reduces the average misprediction rate by 3%–4% for the benchmarks in this paper. Second, we analyze the impact of the length of hashed program counter, local history register, global history register, and branch global addresses of deep learning classifiers on the misprediction rate. Our results show that an adaptive length of the history information is a better choice than the longest history. Third, compared with TAGE, the hardware budget of our model is less than 1% of the TAGE predictor.}, journal={IEEE ACCESS}, author={Mao, Yonghua and Shen, Junjie and Gui, Xiaolin}, year={2018}, pages={10779–10786} }
 @inproceedings{shen_aiken_abbasi_parekh_zhao_dickey_ricketts_2017, title={Rapid prototyping of low loss 3D printed waveguides for millimeter-wave applications}, DOI={10.1109/mwsym.2017.8058593}, abstractNote={Traditional hollow metallic waveguide manufacturing techniques are readily capable of producing components with high-precision geometric tolerances, yet generally lack the ability to customize individual parts on demand or to deliver finished components with low lead times. This paper proposes a Rapid-Prototyping (RP) method for relatively low-loss millimeter-wave hollow waveguides produced using consumer-grade stere-olithographic (SLA) Additive Manufacturing (AM) technology, in conjunction with an electroless metallization process optimized for acrylate-based photopolymer substrates. To demonstrate the capabilities of this particular AM process, waveguide prototypes are fabricated for the W- and D-bands. The measured insertion loss at W-band is between 0.12 dB/in to 0.25 dB/in, corresponding to a mean value of 0.16 dB/in. To our knowledge, this is the lowest insertion loss figure presented to date, when compared to other W-Band AM waveguide designs reported in the literature. Printed D-band waveguide prototypes exhibit a transducer loss of 0.26 dB/in to 1.01 dB/in, with a corresponding mean value of 0.65 dB/in, which is similar performance to a commercial metal waveguide.}, booktitle={2017 ieee mtt-s international microwave symposium (ims)}, author={Shen, J. Y. and Aiken, M. W. and Abbasi, M. and Parekh, D. P. and Zhao, X. and Dickey, Michael and Ricketts, D. S.}, year={2017}, pages={41–44} }
 @inproceedings{shen_aiken_ladd_dickey_ricketts_2016, title={A simple electroless plating solution for 3D printed microwave components}, DOI={10.1109/apmc.2016.7931434}, abstractNote={Using a modified version of the Tollens' Test, acrylate-based polymer prints made using a consumer-grade Digital Light Projection Stereolithographic (DLP-SLA) 3D printer are successfully silver plated, without the need for complex surface preparation techniques. A single-piece prototype waveguide design is used for testing the plating process, and a discussion is provided on minimizing printing process variables such as polymerization shrinkage and undesirable geometric tolerance variance. Measurement results of plated WR-10 1-inch waveguide sections show reflection coefficients of less than −21dB and an insertion loss of less than 0.53dB, which are comparable to similar studies using specialized plating and split-block designs. Furthermore, this approach shows great potential in providing an affordable passive microwave component rapid prototyping solution for research environments.}, booktitle={2016 asia-pacific microwave conference (apmc2016)}, author={Shen, J. Y. and Aiken, M. and Ladd, C. and Dickey, Michael and Ricketts, D. S.}, year={2016} }
 @article{liu_shen_yin_liu_liu_2015, title={Compact 0.92/2.45-GHz Dual-Band Directional Circularly Polarized Microstrip Antenna for Handheld RFID Reader Applications}, volume={63}, ISSN={["1558-2221"]}, DOI={10.1109/tap.2015.2452954}, abstractNote={This paper presents a compact 0.92/2.45-GHz dual-band directional circularly polarized (CP) microstrip antenna for handheld radio-frequency identification (RFID) reader applications. The proposed antenna comprises a wideband dual-feed network and two stacked concentric patches assembled by two orthogonally placed vertical probes. The dual-feed network feeds quadrature signals across the RFID bands between 0.92 and 2.45 GHz. The two stacked concentric patches provide resonance frequencies in fundamental mode for lower band and higher band, respectively. Additionally, the antenna features only one connection port and same sense CP radiation at two bands, beneficial to cost and complexity reductions of the dual-band front end of RFID readers. The measurement results show the performances of return loss (RL) >10 dB, 3-dB gain variation, and axial ratio (AR) <;3 dB are achieved on the bands 0.911-0.933 GHz and 2.40- 2.57 GHz. The measured peak gains are 3.8 dBic at 0.926 GHz and 8.9 dBic at 2.48 GHz. In addition, the antenna provides symmetrical patterns with wide-angle half-power beamwidths and wide-angle 3-dB AR beamwidths. The size of the antenna 110 × 110 × 6.6 mm3 is much smaller than reported dual-band one port RFID directional CP reader antennas. The antenna appropriates to both ultra-high frequency (UHF) and industrial scientific and medical (ISM) bands in handheld RFID reader applications.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Liu, Qiang and Shen, Junyu and Yin, Jungang and Liu, Hongli and Liu, Yuanan}, year={2015}, month={Sep}, pages={3849–3856} }
 @article{liu_shen_liu_wu_su_liu_2015, title={Low-cost compact circularly polarized directional antenna for universal UHF RFID handheld reader applications}, volume={14}, journal={IEEE Antennas and Wireless Propagation Letters}, author={Liu, Q. and Shen, J. Y. and Liu, H. L. and Wu, Y. L. and Su, M. and Liu, Y. N.}, year={2015} }
 @article{liu_shen_liu_liu_2014, title={Dual-Band Circularly-Polarized Unidirectional Patch Antenna for RFID Reader Applications}, volume={62}, ISSN={["1558-2221"]}, DOI={10.1109/tap.2014.2360704}, abstractNote={A dual-band 0.92/2.45 GHz circularly-polarized (CP) unidirectional antenna using the wideband dual-feed network, two orthogonally positioned asymmetric H-shape slots, and two stacked concentric annular-ring patches is proposed for RF identification (RFID) applications. The measurement result shows that the antenna achieves the impedance bandwidths of 15.4% and 41.9%, the 3-dB axial-ratio (AR) bandwidths of 4.3% and 21.5%, and peak gains of 7.2 dBic and 8.2 dBic at 0.92 and 2.45 GHz bands, respectively. Moreover, the antenna provides stable symmetrical radiation patterns and wide-angle 3-dB AR beamwidths in both lower and higher bands for unidirectional wide-coverage RFID reader applications. Above all, the dual-band CP unidirectional patch antenna presented is beneficial to dual-band RFID system on configuration, implementation, as well as cost reduction.}, number={12}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Liu, Qiang and Shen, Junyu and Liu, Hongli and Liu, Yuanan}, year={2014}, month={Dec}, pages={6428–6434} }