Low Local Oscillator Power Requirements Research Articles

High-Tc Superconducting Josephson Junction Harmonic Mixers with Stub Tuners on Integrated Bowtie Antennas

Ordinary mixers can hardly meet the requirements in terahertz (THz) communications due to the low-power and expensive THz sources. Sensitive harmonic mixers have been widely studied to avoid this problem, owing to the fact that the higher the number of harmonics, the lower the local oscillator (LO) frequency, and the lower the cost. High-Tc superconducting (HTS) Josephson junction (JJ) mixers are performing candidates for THz receiver frontends because of the advantages of excellent sensitivity, wide bandwidth, high harmonic number and low LO power requirement. However, the normal-state resistance of HTS JJ is so low that traditional antennas are difficult to match it. In other words, it is quite a challenge to match the input impedance to a low input impedance for traditional antennas, especially for antennas fed by coplanar striplines (CPSs). In this work, based on the structure of bowtie, two types of stub tuners were integrated to decrease the impedance of the bowtie antenna so as to improve the coupling efficiency between the traditional bowtie antenna and the JJ. Furthermore, HTS YBa2Cu3O7-δ (YBCO) JJ harmonic mixers coupled with the proposed structures and fed by CPSs are fabricated and measured. The measurements show that the JJ mixer coupled with a pair of open-end stubs of the bowtie antenna achieves up to 88 harmonics, with a conversion efficiency of −69.6 dB. In contrast, the JJ mixer coupled with a pair of lumped-element stubs of the bowtie antenna only attains to 30 harmonics, with a conversion efficiency of −73.4 dB. Additional numerical simulations indicate that the coupling efficiency is enhanced when the complex impedance of the antenna is explicitly considered. Compared with other coupled traditional antennas, the JJ mixer with bowtie antenna has the largest harmonic number. This work paves the way for the future application of low-frequency and low-cost LO for THz communications.

A 38-GHz High-Speed I/Q Modulator Using Weak-Inversion Biasing Modified Gilbert-Cell Mixer

A 90-nm CMOS I/Q modulator with low dc-power consumption, low local oscillator (LO) power requirement, and high image reject ratio (IRR) is proposed in this letter. To minimize dc-power consumption and LO power requirement, the weak-inversion biasing technique is adopted in the switching transistors and the modified Gilbert-cell mixer structure is also applied to solve the voltage headroom problem in conventional Gilbert-cell mixer. Moreover, to demonstrate high IRR, a four-way quadrature signal generator with low phase and gain imbalance is implemented. With only 28.8-mW dc consumption and 0-dBm LO driving power, this I/Q modulator performs −2 ± 1-dB conversion gain and better than −35-dBc IRR from 34 to 39 GHz at 0.5-GHz IF frequency. Furthermore, due to the high IRR performance, 16-quadratic-amplitude modulation (QAM) and 256-QAM measurements with data rate of 4 and 1.6 Gb/s are successfully demonstrated at 38 GHz.

A low local oscillator power K‐band mixer based on tunneling diodes

AbstractIn this article, we will demonstrate a low local oscillator (LO) power K‐band mixer based on a tunneling diode technology. Due to its unique diode characteristics, no DC supply is needed, whereas an LO power as low as −2 dBm is required for nominal functionality. The energy‐efficient MMIC prototype integrates a pair of heterojunction interband tunnel diodes and a 90° coplanar broadband coupler. The prototype is optimized within the 19–26 GHz band, with an IF ranging from zero to 7 GHz. In addition, when compared with other mixers, it has the lowest LO power requirement with a conversion loss ranging from 6 to 10 dB, an input compression point of −3 dBm and an intercept 2nd and 3rd order intermodulation point of 22 and 12 dBm, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1140–1143, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24228

Planar Millimeter-Wave Diode Mixer (Short Paper)

A new mixer has been built, using a planar GaAs Schottky-barrier diode, for operation at frequencies around 100 GHz. The mixer has low noise temperature and conversion loss and low local oscillator power requirement. The design is such that construction of scaled versions should he possible for operation up to 200 GHz.