A novel varactor tunable dual-band bandpass filter (BPF) using stub-loaded stepped-impedance resonators is proposed in this letter. Compared with the traditional tunable filters, the source-load coupling and T-shape stub-loaded lines are employed in this design. The proposed BPF architecture has the advantages of high selectivity and less control voltages. In the overall tuning range, the proposed filter is designed with 5-6 transmission zeros and more than 30 dB rejection between the two passbands. Meanwhile, only one control voltage is needed for each passband. A prototype of this filter is fabricated and measured. The measurement results show great agreement with simulated results, which show that the first passband can be tuned in a frequency range from 0.8 to 1.02 GHz, and the second passband varies from 2.02 to 2.48 GHz.

Artificial magnetic conductor (AMC) is a kind of periodic structures and it introduces a zero degrees reflection phase shift to incident wave. In order to reduce size of artificial magnetic conductor and increase their working bandwidth, InP process is used to design AMC in this paper. InP material has advantages of large forbidden bandwidth, high electron mobility, negative resistance effect etc. AMC based on InP process has been analyzed and results show that the proposed AMC has a good bandwidth compared with that of CMOS process for its smooth reflection phase variation and its whole size is greatly reduced.

This paper presents a 5 GHz CMOS radio frequency (RF) transceiver built with 0.18 μm RF-CMOS technology by using a proprietary protocol, which combines the new IEEE 802.11n features such as multiple-in multiple-out (MIMO) technology with other wireless technologies to provide high data rate robust real-time high definition television (HDTV) distribution within a home environment. The RF frequencies cover from 4.9 to 5.9 GHz: the industrial, scientific and medical (ISM) band. Each RF channel bandwidth is 20 MHz. The transceiver utilizes a direct up transmitter and low-IF receiver architecture. A dual-quadrature direct up conversion mixer is used that achieves better than 35 dB image rejection without any on chip calibration. The measurement shows a 6 dB typical receiver noise figure and a better than 33 dB transmitter error vector magnitude (EVM) at −3 dBm output power.

A novel accurate and efficient modeling method based on Equivalent Circuit trained Artificial Neural Network (EC-ANN) technique is developed for a RF-MEMS extended tuning range varactor. The parameters are extracted directly from the equivalent circuit model and used as training and testing sets for the ANN. Experiments show that the proposed approach can be used to fast and accurately model the RF characteristics of the RF-MEMS varactor. The results can agree with the EC-ANN predictions and the Ansoft HFSS simulations. To extend the capabilities of the proposed methodology, the developed EC-ANN modeling technique is used for design, simulation and optimization of the MEMS circuits.

Two RF MEMS-based true time delay lines for millimeter-wave applications were presented.First,a novel RF MEMS extended tuning range varactor structure was employed and on-wafer measure-ment results obtained a maximum capacitance ratio of 5.39.A five-mask fabrication process was designed by using surface micromachining technology.Based on the RF MEMS varactor design,the proof-of-principle Ka-band RF MEMS true time delay line was designed,fabricated and tested.The on-wafer measurement results show that,for the Ka-band RF MEMS-based true time delay line,the insertion loss at 28 GHz is-2.36 dB in the down-state and the return losses at the two ports are both below -15 dB at 28 GHz and below-10 dB over the entire tested frequency range of 5-40 GHz.Based on the Ka-band RF MEMS true time delay line design,a 60 GHz RF MEMS true time delay line design has been finished and is ready to be fabricated.

A simple method of gain improvement for the cavity backed slot antenna based on the substrate integrated waveguide technique has been presented in this article. By using dual slot at the cavity edges to substitute a single slot at the cavity center as the radiating element gain of the cavity backed slot antenna has been improved about 1.7 dB whereas its total size is little reduced. The proposed antenna has high radiation performance and keeps the advantages low profile, easy integration, and low cost fabrication. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2767-2769. 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25582

Single fed low profile cavity backed crossed slot antennas for dual frequency dual linear polarization and circular polarization applications are first presented in this paper. By employing the substrate integrated waveguide (SIW) technique in the antenna designs, the low profile backed cavity structure can be realized by using only a single layer of low cost printed circuit board (PCB) substrate. A single grounded coplanar waveguide (GCPW) is employed as the feeding element to excite the TE 120 and TE 210 modes in the SIW cavity. A crossed slot structure is used as the radiating element in order to radiate the desired dual linearly or circularly polarized wave. From the measurement results, it is seen that these novel antennas retain the advantages of conventional metallic cavity backed antennas, including high gain, high front-to-back ratio (FTBR), and low cross polarization level (CPL). Furthermore, the proposed antennas also possess the advantages of low profile, light weight, low fabrication cost, and easy integration with planar circuits.

MEMS varactors are one of the important passive MEMS devices. Their applica- tions include use in VCOs, tunable impedance matching networks, tunable fllters, phase shifters, and true time delay lines. The shunt capacitive structure has been employed in most of the conventional MEMS varactor designs because of its simplicity. However, the capacitance ratio of this conventional shunt capacitive MEMS varactor is limited to 1.5 because of the MEMS Pull- In efiect, which happens when the de∞ection between the MEMS top and bottom metal plates increase beyond 1/3 of the airgap between the two metal plates. At that time, the top metal plate will quickly snap down. This efiect is the major limitation in MEMS varactor designs and can cause nonlinearity and mechanically instability. In order to eliminate this Pull-In efiect, the author employed the so-called MEMS extended tuning range structure. This structure utilizes a variable height top metal beam with separate actuation parts. The airgap between the center part of the top beam and the bottom plate has been designed to be less than 1/3 of the airgap between the top beam and the bottom actuation pads. When DC bias is applied to the actuation parts, the entire top beam will move down together. Consequently, before the Pull-In efiect happens at the actuation parts, the center part has already traveled through its entire tuning range, which means that the capacitive ratio of this kind of MEMS varactor can go to inflnity. A fabrication process employing a GaAs substrate has been designed based on surface micro- machining technology. The maximum capacitance ratio of the designed MEMS extended tuning range varactor is 5.39 with a Cmax value of 167fF. Based on this MEMS varactor design, a Ka-band MEMS varactor based distributed true time delay line has been designed. This dis- tributed true time delay line includes a high impedance CPW transmission line with 70› un- loaded impedance at 28GHz and eight MEMS extended tuning range varactors based on the varactor design periodically loaded on the CPW line. The testing results show that a 56 - phase delay variation has been achieved at 28GHz. The measured insertion loss at 28GHz is i1:07dB at the up-state and i2:36dB at the down-state. The measured return losses, S11 and S22, are both below i15dB at 28GHz and below i10dB over the entire tested frequency range of 5GHz to 40GHz.

Phased antenna array (PAA) systems play an important role in modern radar and communication technologies. In order to satisfy the broadband requirement of future PAA systems, a true time delay approach is preferred over phase delay approaches. Several true time delay methods for PAA beam steering and beam shaping are compared at K-Band and Ka-Band frequencies. Fabrication details and test results for Ka- Band micro-electro-mechanical systems (MEMS) based true time delay lines are presented.

Novel RF-MEMS extended tuning range varactors are being developed for incorporation in arrays of RF MEMS based true time delay lines for use in millimeter-wave Phased Antenna Array (PAA) systems. A frequency of 28 GHz (Ka-Band) has been selected for the activity since it is a frequency region of considerable commercial, scientific, and military interest as well as being sufficiently high to result in small size units. The design of the 28 GHz proof-of-principle RF MEMS varactor based true time delay line is presented together with the fabrication process and the initial measurement results.