Khalid Alharbi

High Performance Resonant Tunneling Diode Oscillators for THz Applications

This paper presents monolithic microwave integrated circuit (MMIC) resonant tunneling diode (RTD) oscillator with high performance: high power at high frequencies. The circuit topology employs two In0.53Ga0.47As/AlAs RTDs in parallel and each device is biased individually. These oscillators operate at 125GHz, 156GHz and 166 GHz with output power 0.34 mW, 0.24 mW and 0.17 mW respectively. These are highest power reported for RTD oscillators in D-band (110 GHz-170 GHz) frequency range. The phase noise of the RTD oscillators was characterized and is reported. This work demonstrates the circuit-based RTD oscillator design approach to increase the output power of RTD oscillators at millimeter-waves.

W-band InP-based resonant tunnelling diode oscillator with milliwatt output power

This paper presents a high power (milliwatt) W-band resonant tunneling diode (RTD) oscillator. The oscillator circuit employs two RTD devices in parallel and operates at 75.2 GHz with -0.2 dBm (0.95 mW) output power. To the authors knowledge, this is the highest reported output power for an RTD oscillator at W-band.

Resonant tunnelling diode terahertz sources for broadband wireless communications

This paper will discuss resonant tunnelling diode (RTD) sources being developed on a European project iBROW (ibrow.project.eu) to enable short-range multi-gigabit wireless links and microwave-photonic interfaces for seamless links to the optical fibre backbone network. The practically relevant output powers are at least 10 mW at 90 GHz, 5 mW at 160 GHz and 1 mW at 300 GHz and simulation and some experimental results show that these are feasible in RTD technology. To date, 75 - 315 GHz indium phosphide (InP) based RTD oscillators with relatively high output powers in the 0.5 – 1.1 mW range have been demonstrated on the project. They are realised in various circuit topologies including those that use a single RTD device, 2 RTD devices and up to 4 RTD devices for increasingly higher output power. The oscillators are realised using only photolithography by taking advantage of the large micron-sized but broadband RTD devices. The paper will also describe properties of RTD devices as photo-detectors which makes this a unified technology that can be integrated into both ends of a wireless link, namely consumer portable devices and fibre-optic supported base-stations (since integration with laser diodes is also possible).

Novel tunnel diode oscillator power combining circuit topology based on synchronisation

Devices with negative differential resistance (NDR) regions in their current-voltage (I-V) characteristics such as tunnel diodes (TD) and resonant tunneling diodes (RTDs) have been used for realizing high frequency oscillators. In this paper, a new power combining technique is presented which combines output power through synchronisation of two coupled tunnel diode oscillators. The measured output power of the two synchronised tunnel diode oscillators realized in microstrip hybrid technology was -6.72 dBm at 716.2 MHz, while that of single tunnel diode oscillator was -9.09 dBm at 575.7 MHz. The circuit topology proposed in this paper can be utilized to realize high power and high frequency RTD terahertz sources.

G-Band MMIC resonant tunneling diode oscillators

This paper presents a G-band (140 -220 GHz) monolithic microwave/ (millimeter-wave) integrated circuit (MMIC) resonant tunneling diode (RTD) oscillator operating at 205.8 GHz with -14.6 dBm output power. The circuit topology employs two InGaAs/AlAs RTDs in parallel. A new RTD epi-layer material design which will greatly benefit micrometer-sized RTD devices for high output power of millimeterwave oscillators is also presented. It is expected that the oscillator output power will reach several mW for RTD oscillators operating in the G-band. This work shows the promising potential of RTD oscillators as terahertz (THz) sources for a variety of applications including high speed wireless communication.

MMIC resonant tunneling diode oscillators for THz applications

This paper presents a monolithic microwave integrated circuit (MMIC) that combines two InGaAs/AlAs resonant tunneling diodes (RTDs) in parallel. By employing appropriate circuitry the oscillators generate an output power of about 1 mW (-0.1 dBm) at 39.6 GHz and (-0.2 dBm) at 75.2 GHz which are the highest power reported for RTD-based oscillators in the relative frequency range. This work demonstrates that circuit-based power combining technique can be used to solve the bottle-neck of RTD oscillators, i.e. low output power at millimeter-wave or even higher frequencies. The techniques show the potential to be implemented at terahertz (THz) frequencies.

THz electronics for data centre wireless links — The TERAPOD project

This paper presents an overview of the terahertz (THz) resonant tunneling diode (RTD) technology that will be used as one of the approaches towards wireless data centres as envisioned on the eU H2020 TERAPOD project. We show an example 480 gm × 680 gm THz source chip at 300 GHz employing a 4 gm × 4 gm RTD device with 0.15 mW output power. We also show a basic laboratory wireless setup with this device in which up to 2.5 Gbps (limited by equipment) was demonstrated.

Resonant tunneling diode photodetectors for optical communications

Resonant tunneling diodes (RTDs) have been extensively studied due to their potential applications in very high speed electronics, optical communications, and terahertz generation. In this work, we report the latest results on the characterization of the resonant tunneling diode photo-detectors (RTD-PDs), incorporating InGaAlAs light sensitive layers for sensing at the telecommunication wavelength of λ = 1310 nm. We have measured responsivities up to 28.8 A/W and light induced voltage shift of 204.8 V/W for light injection powers around 0.25 mW.

High performance microstrip resonant tunneling diode oscillators as terahertz sources

This paper prepents monolithic microwave integrated circuits (MMIC) employing large size resonant tunneling diode (RTD) with high power at high frequencies. This is achieved by proper design of the resonating inductances which are realized by shorted microstrip transmission lines with low characteristic impedances (Z0 = 10.4 Ω). Two oscillators were fabricated using photolithography. Oscillation frequencies of 312 GHz delivering 0.15 mW and 262 GHz delivering 0.19 mW were measured for oscillators employing a single 4 μm × 4 μm and 5 μm × 5 μm RTD devices, respectively.

Bow-tie antenna for terahertz resonant tunnelling diode based oscillators on high dielectric constant substrate

In this paper, a broadband bow-tie slot antenna is presented. The coplanar waveguide (CPW) fed antenna is fabricated on an InP substrate for same chip integration with the promising resonant tunnelling diode (RTD) terahertz (THz) oscillator which has the capability of room temperature operation and with relative high power. The antenna exhibits a very wide bandwidth (return loss S11 <;-10 dB) around the design frequency (300 GHz). However, the radiation pattern is degraded because of the large dielectric constant of the InP substrate. A technique to overcome this problem employing a reflector ground plane underneath a thin substrate of low dielectric constant is presented. Initial simulation results of this technique are reported and experimental validation at lower frequency (17 GHz) shows the feasibility of the concept.