Extremely high frequency

About: Extremely high frequency is a research topic. Over the lifetime, 6151 publications have been published within this topic receiving 52336 citations. The topic is also known as: EHF & millimeter wave.

Optical generation of millimeter-wave signals for fiber-radio systems using a dual-mode DFB semiconductor laser

Abstract: This paper presents a new approach to the optical generation of millimeter-wave signals using a dual-mode multisection distributed feedback semiconductor laser. This simple device is capable of generating high power signals between 40 and 60 GHz with extremely high spectral purity and stability. The two optical modes produced by this laser are heterodyned on an ultrafast photodiode to give a beat signal at the mode difference frequency. The phase noise of the beat signal is greatly reduced by phase-locking the modes using an electrical drive signal applied to the laser at a subharmonic of the beat frequency. Millimeter-wave signals are obtained with a linewidth of less than 10 Hz, a phase noise of less than -85 dBc/Hz at 100 kHz offset, and a locking range of about 500 MHz. Millimeter-wave fiber-radio systems are seen as a major application area for these new compact optical sources. >

Active and nonlinear wave propagation devices in ultrafast electronics and optoelectronics

Abstract: We describe active and nonlinear wave propagation devices for generation and detection of (sub)millimeter wave and (sub)picosecond signals. Shock-wave nonlinear transmission lines (NLTL's) generate /spl sim/4-V step functions with less than 0.7-ps fall times. NLTL-gated sampling circuits for signal measurement have attained over 700-GHz bandwidth. Soliton propagation on NLTL's is used for picosecond impulse generation and broadband millimeter-wave frequency multiplication. Picosecond pulses can also be generated on traveling-wave structures loaded by resonant tunneling diodes. Applications include integration of photodetectors with sampling circuits for picosecond optical waveform measurements and instrumentation for millimeter-wave waveform and network (circuit) measurements both on-wafer and in free space. General properties of linear and nonlinear distributed devices and circuits are reviewed, including gain-bandwidth limits, dispersive and nondispersive propagation, shock-wave formation, and soliton propagation. >

3-D Printed Metal-Pipe Rectangular Waveguides

Abstract: This paper first reviews manufacturing technologies for realizing air-filled metal-pipe rectangular waveguides (MPRWGs) and 3-D printing for microwave and millimeter-wave applications. Then, 3-D printed MPRWGs are investigated in detail. Two very different 3-D printing technologies have been considered: low-cost lower-resolution fused deposition modeling for microwave applications and higher-cost high-resolution stereolithography for millimeter-wave applications. Measurements against traceable standards in MPRWGs were performed by the U.K.’s National Physical Laboratory. It was found that the performance of the 3-D printed MPRWGs were comparable with those of standard waveguides. For example, across X-band (8–12 GHz), the dissipative attenuation ranges between 0.2 and 0.6 dB/m, with a worst case return loss of 32 dB; at W-band (75–110 GHz), the dissipative attenuation was 11 dB/m at the band edges, with a worst case return loss of 19 dB. Finally, a high-performance W-band sixth-order inductive iris bandpass filter, having a center frequency of 107.2 GHz and a 6.8-GHz bandwidth, was demonstrated. The measured insertion loss of the complete structure (filter, feed sections, and flanges) was only 0.95 dB at center frequency, giving an unloaded quality factor of 152—clearly demonstrating the potential of this low-cost manufacturing technology, offering the advantages of lightweight rapid prototyping/manufacturing and relatively very low cost when compared with traditional (micro)machining.

An Ultra-Wideband 80 GHz FMCW Radar System Using a SiGe Bipolar Transceiver Chip Stabilized by a Fractional-N PLL Synthesizer

Abstract: A radar system with an ultra-wide FMCW ramp bandwidth of 25.6 GHz (≈32%) around a center frequency of 80 GHz is presented. The system is based on a monostatic fully integrated SiGe transceiver chip, which is stabilized using conventional fractional-N PLL chips at a reference frequency of 100 MHz. The achieved in-loop phase noise is ≈ -88 dBc/Hz (10 kHz offset frequency) for the center frequency and below ≈-80 dBc/Hz in the wide frequency band of 25.6 GHz for all offset frequencies >;1 kHz. The ultra-wide PLL-stabilization was achieved using a reverse frequency position mixer in the PLL (offset-PLL) resulting in a compensation of the variation of the oscillators tuning sensitivity with the variation of the N-divider in the PLL. The output power of the transceiver chip, as well as of the mm-wave module (containing a waveguide transition), is sufficiently flat versus the output frequency (variation <;3 dB). In radar measurements using the full bandwidth an ultra-high spatial resolution of 7.12 mm was achieved. The standard deviation between repeated measurements of the same target is 0.36 μm.

Synthesis of an electromagnetic wave absorber for high-speed wireless communication.

Abstract: Millimeter waves (30-300 GHz) are starting to be used in next generation high-speed wireless communications. To avoid electromagnetic interference in this wireless communication, finding a suitable electromagnetic wave absorber in the millimeter wave range is an urgent matter. In this work, we prepared a high-performance millimeter wave absorber composed of a series of aluminum-substituted epsilon-iron oxide, epsilon-Al(x)Fe(2-x)O(3), nanomagnets (0 < or = x < or = 0.40) with a particle size between 25 and 50 nm. The materials in this series have an orthorhombic crystal structure in the Pna2(1) space group, which has four nonequivalent Fe sites and Al ion that predominantly occupies the tetrahedral [FeO(4)] site. The field-cooled magnetization curves showed that the T(C) values were 448, 480, and 500 K for x = 0.40, 0.21, and 0, respectively. The magnetization versus external magnetic field showed that the coercive field H(c) values at 300 K were 10.2, 14.9, and 22.5 kOe for x = 0.40, 0.21, and 0, respectively. The millimeter wave absorption properties were measured at room temperature by terahertz time domain spectroscopy. The frequencies of the absorption peaks for x = 0.40, 0.30, 0.21, 0.09, 0.06, and 0 were observed at 112, 125, 145, 162, 172, and 182 GHz, respectively. These absorptions are due to the natural resonance achieved by the large magnetic anisotropies in this series. Such frequencies are the highest ones for magnetic materials. Because aluminum is the third most abundant atom, aluminum-substituted epsilon-iron oxide is very economical, and thus these materials are advantageous for industrial applications.