Low-loss Broadband Research Articles

Low-Loss and Broadband Asymmetric Broadside-Coupled Balun for Mixer Design in 0.18-$\mu{\hbox {m}}$ CMOS Technology

This study presents an asymmetric broadside coupled balun with low-loss broadband characteristics for mixer designs. The correlation between balun impedance and a 3D multilayer CMOS structure are discussed and analyzed. Two asymmetric multilayer meander coupled lines are adopted to implement the baluns. Three balanced mixers that comprise three miniature asymmetric broadside coupled Marchand baluns are implemented to demonstrate the applicability to MOS technology. Both a single and dual balun occupy an area of only 0.06 mm2. The balun achieves a measured bandwidth of over 120%, an insertion loss of better than 4.1 dB (3 dB for an ideal balun) at the center frequency, an amplitude imbalance of less than 1 dB, and a phase imbalance of less than 5deg from 10 to 60 GHz. The first demonstrated circuit is a Ku-band mixer, which is implemented with a miniaturized balun to reduce the chip area by 80%. This 17-GHz mixer yields a conversion loss of better than 6.8 dB with a chip size of 0.24 mm2. The second circuit is a 15-60-GHz broadband single-balanced mixer, which achieves a conversion loss of better than 15 dB and occupies a chip area of 0.24 mm2. A three-conductor miniaturized dual balun is then developed for use in the third mixer. This star mixer incorporates two miniature dual baluns to achieve a conversion loss of better than 15 dB from 27 to 54 GHz, and occupies a chip area of 0.34 mm2.

Substrate Integrated Waveguide-to-Microstrip Transition in Multilayer Substrate

This paper presents a novel transition between a microstrip line and a substrate integrated waveguide (SIW) in a multilayer substrate design environment. In order to achieve a low-loss broadband response, the transition, consisting of a tapered or multisectional ridged SIW and a tapered microstrip line, is modeled and designed by simultaneously considering both impedance matching and field matching. Characteristic impedance and guided wavelength calculated by using closed-form expressions based on a transverse resonant method are used to develop our design procedure. Effective broad bandwidth is obtained in two examples developed in this study, which are validated with simulated and measured results. This transition provides a simple way to design substrate integrated circuits with buried microstrip circuits in the multilayer substrate in which any ratio of impedance transform can be anticipated.

Optimal design method of a low-loss broadband Y branch with a multimode waveguide section.

An optimal design method for a low broadband silica-on-silicon Y branc is considered. A multimode waveguide section, which was used earlier to reduce the excess loss, is designed optimally when the light distribution at the end of the multimode waveguide section is matched to the profile of the symmetric supermode for the structure of the two branching waveguides. An optimization method that combines the genetic algorithm and a gradient-based search method is used to obtain the optimal geometrical parameters for the multimode waveguide section as well as the widths for the input and branching waveguides.

Low-loss broadband semiconductor saturable absorber mirror for mode-locked Ti:sapphire lasers

We developed a low-loss broadband silver-based semiconductor saturable absorber mirror (SESAM) for mode-locked Ti:sapphire lasers. By the insertion of a dielectric layer in between the semiconductor and metal layers, the non-saturable loss of the SESAM was reduced to ∼1%. The experiment demonstrated that such a SESAM offers a sufficiently broad band-width to support sub-10-fs pulses, with a reasonably high output power.

Self-starting mode-locked Cr^4+:YAG laser with a low-loss broadband semiconductor saturable-absorber mirror

We report a self-starting mode-locked Cr(4+):YAG laser with a low-loss broadband metal reflector-based semiconductor saturable-absorber mirror. The minimum pulse width was 44 fs at a wavelength of 1520 nm.

Broadband semiconductor saturable-absorber mirror for a self-starting mode-locked Cr:forsterite laser

We report a low-loss broadband semiconductor saturable-absorber mirror (SESAM) that uses gold film as the reflector. A semiconductor- SiO(2) double-layer stack enhances the reflectivity of the gold film. This low-loss SESAM was used in a mode-locked Cr:forsterite laser to produce self-starting 20-fs-scale laser pulses at 1.3 microm . The structure can be applied to SESAM's for other wavelengths.

Quadruply resonant optical parametric oscillation in a monolithic total-internal-reflection resonator

Monolithic total-internal-reflection resonators are low-loss broadband devices that permit variable input–output coupling. They are ideally suited as resonators for high-efficiency low-threshold widely tunable continuous-wave optical parametric oscillation. We demonstrate a continuous-wave quadruply resonant MgO:LiNbO3 optical parametric oscillator in which doubly resonant second-harmonic generation and doubly resonant optical parametric oscillation occur simultaneously. The threshold subharmonic power at 1.06 μm for oscillation near 1.06 μm is 0.4 mW. Stable single-frequency operation is achieved, and the tuning curve is measured.

Low-loss broadband multimode corrugated waveguide performance

A 30-m-long waveguide run using circular corrugated waveguide (i.d.=6.35 cm) with a corrugated period and depth of 254 μm (0.01 in.) has been fabricated and installed on TFTR (Tokamak Fusion Test Reactor) for use in electron cyclotron emission measurements, and is the first large scale application of this type of waveguide. It is designed for low-loss (<0.01 dB/m) multimode operation between 75 and 575 GHz, and includes three E-plane and four H-plane miter bends. Single-mode measurements at 140 GHz and multimode measurements at 250 GHz indicate that both ohmic losses as well as loss due to mode conversion are negligible with this type of transmission line.

Efficient single mode operation of a CW ring dye laser with a Mach-Zehnder interferometer

Stable single mode operation of a ring dye laser is obtained with the combination of a Mach-Zehnder interferometer (MZI), three plate birefringent filter, a single thin etalon and a unidirectional diode. The MZI eliminates the fractional insertion loss due to beam walk-off and distortion which an intracavity etalon must introduce in order to select single frequency operation. We experimentally demonstrate the low insertion loss, single mode stability and frequency tuning of a ring dye laser using a specially designed, compact MZI. Finally, we propose MZIs with no coatings, which should permit extremely low loss broadband operation.

New low-loss broadband SAW filter using unidirectional IDTs with U-shaped MSCs

A new low-loss broadband SAW filter is presented. A new configuration using one pair of electrically connected IDTs with an optimum number of fingers, as well as unidirectional IDTs with U-shaped MSCs, is described. Experimental results with bandwidth as wide as 10% and loss as low as 3 dB are achieved. Very accurate computer-aided design of a low-loss filter with MSCs is obtained.

Multiloop mixer circuits

It is shown that multiloop mixers using resistance diodes pumped at one frequency, but with various phases, have a minimum loss of 3 dB if the terminations are ‘broadband’, and if the circuit loops have self and mutual impedances which are pure resistances at the intermediate frequency. The latter condition prohibits phase shifters in the intermediate-frequency paths, and therefore implies that these are necessary in successful low-loss broadband mixers. It is further shown that, for the minimum loss of the mixer to approach 0 dB, the circuit must have image-rejection properties.

The Ferromagnetic Faraday Effect at Microwave Frequencies and its Applications

A new microwave circuit element dependent on the Faraday rotation of a polarized wave has been developed. The element violates the reciprocity theorem and, because it shares this property with a gyroscope and because it is dependent on gyromagnetic resonance absorption, it has been termed a microwave gyrator. It is a low-loss broadband device with many applications. Among these are one-way transmission systems, microwave circulators, microwave switches, electrically controlled variable attenuators and modulators.