Nan-Wei Chen

An Ultra-Broadband Coplanar-Waveguide Bandpass Filter With Sharp Skirt Selectivity

An ultra-broadband coplanar-waveguide (CPW) bandpass filter (BPF) is demonstrated. The proposed CPW BPF is designed via cascading CPW lowpass and bandpass structures. As compared to the classical CPW BPFs, the ultra broadband is realized relatively easily by separately adjusting the cutoff frequencies of the CPW lowpass and bandpass structures. The cascaded CPW BPF is of greater than 120% 3-dB fractional bandwidth, very sharp skirt selectivity, good stopband rejection, and no repeated passbands

Photonic Generation and Wireless Transmission of Linearly/Nonlinearly Continuously Tunable Chirped Millimeter-Wave Waveforms With High Time-Bandwidth Product at W-Band

We demonstrate a novel scheme for photonic generation of chirped millimeter-wave (MMW) pulse with ultrahigh time-bandwidth product (TBP). By using a fast wavelength-sweeping laser with a narrow instantaneous linewidth, wideband/high-power photonic transmitter-mixers, and heterodyne-beating technique, continuously tunable chirped MMW waveforms at the W-band are generated and detected through wireless transmission. Compared with the reported optical grating-based wavelength-to-time mapping techniques for chirped pulse generation, our approach eliminates the problem in limited frequency resolution of grating, which seriously limits the continuity, tunability, and TBP of the generated waveform. Furthermore, by changing the alternating current (AC) waveform of the driving signal to the sweeping laser, linearly or nonlinearly continuously chirped MMW pulse can be easily generated and switched. Using our scheme, linearly and nonlinearly chirped pulses with record-high TBPs (89-103 GHz/ 50 μs/7 × 105) are experimentally achieved.

V-Band On-Chip Dipole-Based Antenna

A V-band on-chip dipole-based antenna for 60 GHz wireless personal area network (WPAN) application is implemented using WIN 0.15 mum pHEMT process. The fabricated antenna has a compact size of 0.9 mm2, including test pads. The antenna comprises a half-wavelength dipole element and two tilted and slotted dipole elements to realize a wider impedance bandwidth than conventional wire dipole antennas, and provides endfire radiation patterns with high front-to-back ratio. The antenna performance is characterized using S-parameter, two-antenna (identical), three-antenna, and radiation pattern measurement methods for return loss, transmission gain, absolute gain, and radiation patterns. Measurement results shows that the on-chip antenna achieves a VSWR = 2 fractional bandwidth of 24% (55 to 70 GHz), a transmission gain of - 32 dB (the separated distance R = 5 cm), an absolute gain of 3.6 dBi, a front-to-back ratio of 12 dB, and an half-power beamwidth of 60deg in E-plane and H-plane. The measured and simulated results are shown in good agreements.

Spectral Power Enhancement in a 100 GHz Photonic Millimeter-Wave Generator Enabled by Spectral Line-by-Line Pulse Shaping

We report generation of high-modulation-depth photonic millimeter-wave (MMW) waveforms by applying line-by-line pulse shaping on a phase-modulated continuous-wave frequency comb. The optimized 20 and 100 GHz optical waveforms are then converted into electrical MMW signals using a near-ballistic uni-traveling-carrier photodiode (NBUTC-PD). A 7.4 dB MMW power enhancement is experimentally achieved by using 2.6 ps optimized pulses at a 100 GHz repetition rate, as compared with excitation by a conventional sinusoidal signal for the NBUTC-PD operated at the same photocurrent. This is in qualitative agreement with a theoretical analysis of spectral power enhancement by optical short pulses comprised of equi-amplitude frequency lines over sinusoidal excitation.

A W-Band Linear Tapered Slot Antenna on Rectangular-Grooved Silicon Substrate

A W-band (75-110 GHz) coplanar-waveguide (CPW)-fed linear tapered slot antenna (LTSA) on rectangular-grooved silicon substrate is presented. Compared to its ungrooved version, the W-band CPW-fed LTSA shows significantly improved endfire radiation patterns in the whole band. Also, the symmetric patterns together with moderately high gain (8-10 dBi), high front-to-back (F/B) ratio (16-28 dB), and low sidelobe level (SLL; -15 to -17 dB for the E-plane and -11 to -18 dB for the if-plane) are achieved. The proposed CPW-fed LTSA is expected to find applications, such as a transceiver antenna in millimeter-wave wireless communication systems, owing to its easy integration with the uniplanar monolithic millimeter-wave integrated circuits

Center Frequency and Bandwidth Controllable Microstrip Bandpass Filter Design Using Loop-Shaped Dual-Mode Resonator

A design approach for developing microwave bandpass filters (BPFs) with continuous control of the center frequency and bandwidth is presented. The proposed approach exploits a simple loop-shaped dual-mode resonator that is tapped and perturbed with varactor diodes to realize center frequency tunability and passband reconfigurabilty. The even- and odd-mode resonances of the resonator can be predominately controlled via the incorporated varactors, and the passband response reconfiguration is obtained with the proposed tunable external coupling mechanism, which resolves the return losses degradation attributed to conventional fixed external coupling mechanisms. The demonstrated approach leads to a relatively simple synthesis of the microwave BPF with an up to 33% center frequency tuning range, an excellent bandwidth tuning capability, as well as a high filter response reconfigurability, including an all-reject response.

High-Speed

A high-speed W -band integrated photonic transmitter is demonstrated. The presented integrated photonic transmitter is essentially developed with a near-ballistic uni-traveling-carrier photodiode integrated with a broadband front end through the flip-chip assembling technique. Technically, compared to our previous design, a W-band bandpass filter is exploited to significantly increase the transmitter IF modulation bandwidth. The demonstrated integrated photonic transmitter has a flat broad IF modulation response, as well as a broad optical-to-electrical (O-E) bandwidth. Specifically, the variation of the normalized IF modulation response, ranging from dc to around 13 GHz, is within 3 dB, and the normalized 3-dB O-E bandwidth is about 24 GHz. On the other hand, an up to 20-Gb/s high data-rate wireless transmission realized with the presented transmitter is demonstrated. The integrated photonic transmitter is expected to find applications in high-speed radio-over-fiber communications.

W

A 25 Gbits/s error-free on-off-keying (OOK) wireless link between an ultra high-speed W-band photonic transmitter-mixer (PTM) and a fast W-band envelope detector is demonstrated. At the transmission end, the high-speed PTM is developed with an active near-ballistic uni-traveling carrier photodiode (NBUTC-PD) integrated with broadband front-end circuitry via the flip-chip bonding technique. Compared to our previous work, the wireless data rate is significantly increased through the improvement on the bandwidth of the front-end circuitry together with the reduction of the intermediate-frequency (IF) driving voltage of the active NBUTC-PD. The demonstrated PTM has a record-wide IF modulation (DC-25 GHz) and optical-to-electrical fractional bandwidths (68-128 GHz, ~67%). At the receiver end, the demodulation is realized with an ultra-fast W-band envelope detector built with a zero-bias Schottky barrier diode with a record wide video bandwidth (37 GHz) and excellent sensitivity. The demonstrated PTM is expected to find applications in multi-gigabit short-range wireless communication.

-Band Integrated Photonic Transmitter for Radio-Over-Fiber Applications

A W-band photonic transmitter-mixer, constructed by integrating a planar quasi-yagi radiator for feeding the WR-10 waveguide-based horn antenna and a near-ballistic uni-traveling-carrier photodiode, is used with a mode-locked fiber laser to obtain 2.5-Gb/s impulse-radio (IR) wireless data transmission at around a center frequency of 100 GHz. The bias-modulation technique provides less jitter and a longer maximum transmission distance compared with the technique of modulating the optical pulse train using an electrooptics modulator. Using the bias-modulation technique, we achieve a 2.5-Gb/s IR wireless data transmission.

Design and demonstration of ultra-fast W-band photonic transmitter-mixer and detectors for 25 Gbits/sec error-free wireless linking.

A microstrip bandpass filter (BPF) with high center-frequency tunability, bandwidth reconfigurability, and a one-side band edge transmission zero (TZ) is presented. The reconfigurable BPF is developed with a simple T-shaped dual-mode resonator, which is externally coupled and perturbed with varactor diodes. Also, the design of adjustable admittance inverters for tunable resonators external coupling is proposed to mitigate the in-band performance degradation that hurdles the ones with a fixed coupling. It is demonstrated that the 1 dB bandwidth is able to be varied from 55 to 175 MHz for center frequency ranging from 750 to 1240 MHz with a low insertion loss (2.9 dB).