Ho-Jin Song

Recent changes in how people consume multimedia services are causing an explosive increase in mobile traffic. With more and more people using wireless networks, the demand for the ultra-fast wireless communications systems is increasing. To date, this demand has been accommodated with advanced modulation schemes and signal-processing technologies at microwave frequencies. However, without increasing the carrier frequencies for more spectral resources, it may be quite difficult to keep up with th

Thanks to the abrupt advances in semiconductor technologies, particularly in terms of the operating frequency, the last decade has seen various efforts and trials in attempts to achieve high-throughput wireless communications at terahertz (THz) frequencies. Through the use of several potential device technologies, not only III-V heterojunction bipolar and high-electron-mobility transistors but also silicon complementary metal-oxide-semiconductors and photonic technologies, high data rates of 100

Presented is 24 Gbit/s wireless data transmission at 300 GHz using a uni-travelling carrier photodiode (UTC-PD) emitter and Schottky barrier diode detector, which were designed and fabricated for larger bandwidth. Both the emitter and the detector were fabricated on the same epi-layer of the UTC-PD. At the link distance of around 50 cm, a bit error rate of less than 1 ×10−10 has been achieved with the transmitted power from the UTC-PD of less than 200 µW and effective antenna gains of 40 and 35

Terahertz waves, which lie in the frequency range of 0.1-10 THz, have long been investigated in a few limited fields, such as astronomy, because of a lack of devices for their generation and detection. Several technical breakthroughs made over the last couple of decades now allow us to radiate and detect terahertz waves more easily, which has trigg

We demonstrate direct quadrature modulator and demodulator monolithic microwave integrated circuits for future terahertz communications at 300 GHz based on the quadrature phase-shift keying (QPSK) modulation format. For the modulating and demodulating signal, we employed half-Gilbert cell mixers, which provide balanced signaling and moderate performance in conversion efficiency with a simple circuit configuration. In order to maintain the balance performance of the modulator and demodulator, pas

In the last couple of decades, solid-state device technologies, particularly electronic semiconductor devices, have been greatly advanced and investigated for possible adoption in various terahertz (THz) applications, such as imaging, security, and wireless communications. In tandem with these investigations, researchers have been exploring ways to package those THz electronic devices and integrated circuits for practical use. Packages are fundamentally expected to provide a physical housing for

In this letter, we demonstrate over 1 mW power generation at 300 GHz with a uni-travelling-carrier photodiode (UTC-PD) packaged in a WR-3 waveguide module. To increase the maximum power, two identical UTC-PDs were monolithically integrated along with a T-junction to combine the power from the two PDs. The UTC-PD module exhibited peak saturated output power of approximately 1.2 mW at 300 GHz with photocurrent of around 20 mA per PD and bias voltage of -3.9 V. In addition, 3 and 10 dB bandwidths w

We present a terahertz wave wireless link operating at 300 GHz which has a potential for use in ultra fast future wireless services in short range. Terahertz wave was generated and modulated with photonic technologies in the transmitter, allowing us to use radio on fiber system concept as well. For the receiver, we used a Schottky barrier diode detector integrated with a planar antenna. With the link, error free data transmission at 12.5 Gbps was experimentally demonstrated. Taking the performan

An ASK receiver MMIC operating at 300 GHz for future terahertz communications is presented. In the receiver IC, we fully integrated all necessary components-a receiving dipole antenna, high gain RF amplifier, envelop detector for demodulating ASK signal and output differential data amplifier-in a 1000×2500 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area. A silicon lens was used to compensate for the small gain of the on-chip antenna.

We present a monochromatic sub-terahertz signal generation technique using an optical comb signal, arrayed waveguide gratings (AWGs), and a uni-traveling carrier photodiode (UTC-PD) for spectroscopic applications. This scheme offers random or continuous frequency tuning in the range between 100 GHz and up to 1 THz. In addition, since a RF synthesizer is employed as a reference signal source of the photonic frequency multiplier, frequency locking with external instruments and reliable operation a

8 Gbit/s wireless data transmission using a 250 GHz millimetre-wave carrier signal is demonstrated. Photonic devices and technologies, including an electro-optic modulator and J-band uni-travelling-carrier photodetector (UTC-PD) module, were used for the transmitter. In addition, a high-efficiency Schottky barrier diode detector monolithically integrated with a ring slot antenna was developed and fabricated for the receiver on the same epi-layer as the UTC-PD.

All-optical signal up-conversion into the millimeter-wave frequency band is demonstrated using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) wavelength converter, which is based on a cross phase modulation (XPM) effect in the SOA. This scheme shows good conversion efficiency with polarization immunity and no increase in phase noise. The measured phase noise of the up-converted RF signal of 32.5 GHz is -79.2 dBc/Hz at 10 KHz offset, which is limited by that from the LO s

A simultaneous all-optical upconversion technique for cost-effective wavelength-division-multiplexing (WDM) radio-over-fiber (RoF) applications utilizing a semiconductor optical amplifier (SOA) Mach-Zehnder interferometer is investigated. The proposed upconversion scheme uses only one frequency upconverter for multi-RoF channels, thereby reducing the complexity and cost of the system. Error-free simultaneous all-optical upconversion of two WDM intermediate frequency (IF) channels (155-Mb/s diffe

Recent advances in semiconductor device technologies and the ever growing worldwide traffic explosion have focused great attention on THz frequencies, which had long been considered a forbidden region in the electromagnetic spectrum. The huge bandwidth, perhaps much larger than the total bandwidth used on Earth for all wireless systems, is now believed to be the only way to handle incredibly large amounts of data instantaneously by wireless means. In this article, we describe the development of

We present 20-Gbps wireless ASK data transmission at 300 GHz with an all-electronic transmitter and receiver for KIOSK instant data downloading applications. The transmitter and receiver MMICs are based on 70-nm indium-phosphide-based high electron mobility transistor technologies of which the cut-off frequency (fmax) is approximately 700 GHz. For an experiment, the transmitter and receiver were packaged in a split-block waveguide and dedicated metallic housing, respectively. With 30-dBi and 25-