Combline filters designed on symmetric stripline

Problems arising during the design of stripline combline filters, which until quite recently were considered as all-stop microwave structures, are considered. It has been shown that the electromagnetic coupling coefficient of quarter-wave stripline resonators increases with the value of material permittivity ε_r, the operating frequency, and the thickness of the filter resonators. For ε_r = 92 and a thickness of stripline resonators of 4 mm, it exceeds 12% at frequencies higher than 2.2 GHz. Two alternative versions of combline filters have been designed: a filter with a coupling strip and a filter without a coupling strip. Experimental data for a nine-resonator combline filter with a thickness of 4 mm, ε_r = 9.7, and the center frequency f ₀ = 2.4 GHz are presented. A method for increasing the selectivity of combline filters with the same number of resonators is proposed. It has been found that amplitude–frequency responses of stripline combline filters are near-symmetric, unlike the responses of microstrip combline filters.     

Antennas for Short Distance Communications in Cryogenic Environment

Sets of bow-tie antennas, used in a single emitter-receiver near-field configuration and in array configuration, have been studied to be used as wireless means to transmit 8–12 GHz microwave signals from the cold stage of a cryogenic system to a room-temperature processing unit. Indeed, the absence of heat conduction allows increasing the performance of cryogenic systems and open the way to multichannel microwave systems that are necessary for imagers. Transmission loss has been found to be lower than 3 dB over a 1.5 GHz bandwidth while crosstalk in the array configuration is kept below ?20 dB when antennas are located at around 90 mm transversally from each other.     

Structural, Magnetic, and Microwave Properties of SrFe12−x (Ni0.5Co0.5Sn) x/2O19 Particles Synthesized by Sol–Gel Combustion Method

This study is intended to evaluate the structural, magnetic, and microwave properties of Ni-Co-Sn-doped strontium hexaferrite SrFe_12?x (Ni_0.5Co_0.5Sn) _x/2 O₁₉ particles with x = 0 to 2.5 synthesized by a sol–gel combustion method. These particles were evaluated to characterize the structural, magnetic, and reflection loss properties of prepared samples by use of x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FTIR) spectroscopy, vibrating-sample magnetometer (VSM), and vector network analyzer. The XRD results confirmed the presence of strontium ferrite phase with magnetoplumbite structure in all synthesized samples. The results of FTIR analysis indicated the formation of functional groups such as metal-oxygen (Sr-O and Fe-O) and carboxylic groups during the sol–gel process. In addition, FE-SEM micrographs indicated that submicron particles with different morphologies such as spherical, pyramidal, irregular, and hexagonal platelet shapes appeared in the structure. According to hysteresis loops, magnetization and coercivity decreased due to occupation of Ni-Co-Sn cations at low levels of substitutions. The microwave absorption characteristics of this ferrite were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% ferrite content showed a maximum reflection loss of ?29 dB at 9.6 GHz with 4 GHz bandwidth through the entire frequency range of 8 GHz to 12 GHz for absorber thickness of 1.5 mm. Based on microwave measurements of reflectivity, this material with the expressed chemical composition could be proposed as a good choice for electromagnetic compatibility and other practical applications such as microwave absorption at high frequencies.     

Rectangular resonators in inverted microstrip and suspended microstrip

Resonant frequency characteristics of rectangular resonators in a generalized shielded suspended substrate line are analysed using a rigorous spectral domain technique. The computed dominant mode resonant frequency of rectangular resonators in a suspended microstrip with centred dielectric, inverted microstrip and suspended microstrip are presented as a function of various structural parameters. These characteristics are distinct from those obtained for a conventional microstrip rectangular resonator. Experiments are carried out in the frequency range 4-18 GHz to verify the computed resonant frequencies for a suspended microstrip with a centred dielectric using first-order basis functions. The results should find applications in the design of inverted microstrip and suspended microstrip passive microwave and millimetre wave integrated circuits.     

Design of Compact Quad-Band Notched UWB-MIMO Antenna

With quad-notched band characteristic, a compact ultra-wideband (UWB) multiple-input-multiple-output antenna is proposed in the article. There are two identical monopole elements in the system. By inserting symmetrical L-shaped slots, complementary split-ring resonators) and C-shaped stubs in each element, four notched bands are achieved to filter 3.5 GHz WiMAX, 5.25 GHz lower WLAN, 5.8 GHz upper WLAN, and 7.5 GHz X-band. Without decoupling structures, the antennas were placed vertically to obtain high isolation. Results indicate that the antenna operates from 2.6 to 13 GHz except four rejected bands, and port isolation (S21) is better than ?25 dB, envelope correlation coefficient is below 0.002 in UWB spectrum frequency of 3.1–10.6 GHz.     

Integrated amateur band and ultra-wide band monopole antenna with multiple band-notched

This paper presents the integrated amateur band and ultra-wide band (UWB) monopole antenna with integrated multiple band–notched characteristics. It is designed for avoiding the potential interference of frequencies 3.99 GHz (3.83 GHz–4.34 GHz), 4.86 GHz (4.48 GHz–5.63 GHz), 7.20 GHz (6.10 GHz–7.55 GHz) and 8.0 GHz (7.62 GHz–8.47 GHz) with VSWR 4.9, 11.5, 6.4 and 5.3, respectively. Equivalent parallel resonant circuits have been presented for each band-notched frequencies of the antenna. Antenna operates in amateur band 1.2 GHz (1.05 GHz–1.3 GHz) and UWB band from 3.2 GHz–13.9 GHz. Different substrates are used to verify the working of the proposed antenna. Integrated GSM band from 0.6 GHz to 1.8 GHz can also be achieved by changing the radius of the radiating patch. Antenna gain varied from 1.4 dBi to 9.8 dBi. Measured results are presented to validate the antenna performances.     

Band notched UWB circular monopole antenna with inductance enhanced modified mushroom EBG structures

Circular monopole antenna for ultra-wide band applications with notch band transition from WLAN to WiMAX is presented. The proposed antenna rejects WiMAX band (3.3–3.8 GHz). Antennas utilises modified mushroom-type electromagnetic band gap (EBG) structures to achieve band-notched designs. The proposed inductance enhanced modified EBG structures are 34 % compact than the conventional mushroom EBG structures. The band notched antenna designs using EBG structures have advantages like notch-frequency tuning, antenna design independent approach and omnidirectional radiation pattern. The step wise effect of inductance enhancement and tuning of notch from WLAN band (5–6 GHz) to WiMAX band is shown. Effect of variation of EBG structure parameters on which notched frequency depends is investigated. The proposed antenna has been fabricated on low cost FR4 substrate with overall dimensions as (42 × 50 × 1.6) mm³. Measured results are in good agreement with simulated ones.     

Two-dimensional photonic crystal Fabry-Perot resonators with lossydielectrics

Square and triangular lattice two-dimensional (2D) photonic crystals (PCs) composed of lossy dielectric rods in air were constructed with a microwave bandgap between 4-8 GHz. Fabry-Perot resonators of varying length were constructed from two of these PCs of adjustable thickness and reflectivity. The quality factor of cavity modes supported in the resonators was found to increase with increasing PC mirror thickness, but only to a point dictated by the lossiness of the dielectric rods. A 2-D periodic Green's function simulation was found to model the data accurately and quickly using physical parameters obtained in separate measurements. Simple rules are developed for designing optimal resonators in the presence of dielectric loss     

Switched inductor dual-band CMOS cross-coupled VCO

This letter proposes a high-performance CMOS dual-band voltage-controlled oscillator (VCO). The VCO consists of two cross-coupled VCOs coupled by a pair of switched inductors or LC resonators to vary the resonator’s inductance. A pair of nMOSFET is used to switch high- and low-frequency bands. The VCO operates at the high-band using low resonator’s inductance and the VCO operates at the low-band using large inductance. The proposed VCO has been implemented with the TSMC 0.18 μm 1P6M CMOS technology and it can generate differential signals in the frequency range of 5.6–6.66 GHz and 4.13–4.75 and it also has comparable high output voltage swings at both low and high-frequency bands. The die area of the dual-band VCO is 0.84 × 1.1 mm². At the supply voltage of 0.75 V, the high (low)-band figure of merit is ?193.6 (?192.3) dBc/Hz.     

Microstrip bandpass filters on substrates with high permittivities

A new class of compact microstrip bandpass filters, the stepped-impedance resonators of which are located close together at a gap of 0.1–0.2 mm, is described. Basic two- and three-element sections of microstrip filters, which are designed around stepped-impedance impedance resonators used to implement tiny selective devices with overall sizes and characteristics comparable to those of microwave ceramic filters, are proposed. It is justified that the mentioned filters can be equipped with closely neighboring metallic shields whose heights are equal to the substrate thickness. As a consequence, these filters turn out to be thinner. The frequency responses of experimental microstrip filters operating at frequencies of 1.75–2 GHz and manufactured on the 1-mm-thick substrates with the permittivity ɛ _r = 100 have been analyzed. The three-pole microstrip filter with a shield (its operating frequency is 1.96 GHz, and sizes are 5 × 5 × 1.5 mm) has been simulated. It is demonstrated that new microstrip filters can be competitive with low-sized ceramic filters in certain applications.     

A 7-GHz multiloop ring oscillator in 0.18-μm CMOS technology

A novel delay stage for ring oscillator utilizing multiloop technique is presented in this paper. Different conventional delay stages for the multiloop ring oscillators have been reviewed and analyzed in this work. By using push-pull inverter as the secondary input in its delay cell, the proposed oscillator demonstrates a frequency improvement of up to 17% when compared with conventional designs. The fabricated oscillator is measured to cover a frequency range of 6.24–7.04 GHz. Operating in 1.8-V power supply, the oscillator manifests itself a phase noise of ?107.7 dBc/Hz@10 MHz offset from a center frequency of 6.25 GHz. The proposed oscillator consumes a current of 40–51 mA from the 1.8-V supply and occupies an area of 440 μm ×  430 μm.     

Compact UWB monopole antenna with quadruple band notched characteristics

ABSTRACT

A compact planar Ultrawideband (UWB) monopole antenna with quadruple band notch characteristics is proposed. The proposed antenna consists of a notched rectangular radiating patch with a 50 Ω microstrip feed line, and a defected ground plane. The quadruple band notched functions are achieved by utilising two inverted U-shaped slots, a symmetrical split ring resonator pair (SSRRP) and a via hole. The fabricated antenna has a compact size of 24 mm × 30 mm × 1.6 mm with an impedance bandwidth ranging from 2.86 to 12.2 GHz for magnitude of S₁₁ < ?10 dB. The four band notched characteristics of proposed antenna are in the WiMAX (worldwide interoperability for microwave access) band (3.25–3.55 GHz), C band (3.7–4.2 GHz), WLAN (wireless local area network) band (5.2–5.9 GHz) and the downlink frequency band of X band (7–7.8 GHz) for satellite communication are obtained. The measured and simulation results of proposed antenna are in good agreement to achieve impedance matching, stable radiation patterns, constant gain and group delay over the operating bandwidth.     

2200 MHz圆环形介质谐振器的研制

讨论了TE011谐振模式的圆环形介质谐振器的研制过程。固定ZnO添加量为质量分数1.00%,考察了WO3改性剂对(Zr0.8Sn0.2)TiO4微波陶瓷介电性能的影响。当w(WO3)为0.25%时,可得到εr为38.0、Q值大于5800(7GHz)、τf小于2.0×10–6/℃的瓷料。以该瓷料为原料制作谐振器,研究了制作工艺和支撑物高度对谐振器性能的影响。发现采用冷等静压成型工艺所制谐振器的Q值比采用干压成型工艺提高了4%。获得了谐振频率为2200MHz的高Q值、高功率、高稳定性圆环形介质谐振器,完全满足设计要求。     

An Optimal Design of Fractal Antenna with Modified Ground Structure for Wideband Applications

This paper premeditates an optimal design of fractal antenna with modified ground structure for wideband applications. The proposed antenna has been designed by taking numerous iterations started from 0th to 3rd. To attain the wideband characteristics, the partial ground plane has been introduced in the 3rd iteration, and the length of the ground plane has been varied to enhance the bandwidth. The maximum value of bandwidth has been adorned in the final iteration as 1.88 and 0.20 GHz. Further, this bandwidth has been improved and embellished as 2.48 GHz within the frequency range of 3–6 GHz by employing horizontal and vertical extensions in the partial ground plane. Antenna is simulated by using HFSS and performance parameters of antenna like return loss (S_11?≤???10 dB), gain and radiation efficiency are in the acceptable limits. The maximum value of gain is reported as 5.1 dB and radiation pattern is also omnidirectional. The proposed antenna is useful for the wireless applications as WiMAX (3.4–3.69 GHz) and WLAN (5.15–5.35 and 5.72–5.82 GHz) Simulated and experimental results are also juxtaposed and found in good agreement with each other.     

Novel Bandpass Filter Configuration Using Coupled Linear Tapered Line Resonators

A novel tapped bandpass filter composed of two‐coupled linear tapered‐line resonators (LTLRs) is proposed. Multistepped resonators are applied to analyzing LTLRs, which are difficult to analyze directly. Through this analysis method, fundamental characteristics of LTLRs and their filter design parameters can be easily derived. This new filter has insertion loss less than 0.6dB at 1.9 GHz, the return loss less than 18dB in the range 1.8‐1.93GHz and 12.3% 3dB bandwidth. Experimental results of fabricated filter are in good agreement with the design results.     

Miniaturised microstrip bandpass filters based on Moore fractal geometry

This paper presents new microstrip bandpass filter design topologies that consist of dual edge-coupled resonators constructed in the form of Moore fractal geometries of second and third iteration levels. The space-filling property for proposed fractal filters has found to produce reduced size shapes in accordance with sequential iteration levels. These filters have been prepared for ISM band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 10.8, dielectric thickness of 1.27 mm and metallisation thickness of 35 µm. The output responses of each fractal bandpass filter have been determined by a full-wave-based electromagnetic simulator Sonnet software package. Simulated and experimental results are approximately compatible with each other. These responses clarify that these fractal filters have good transmission and return loss characteristics with blocked higher harmonics in out-of-band regions.     

225–255-GHz InP DHBT Frequency Tripler MMIC Using Complementary Split-Ring Resonator

In this paper, a novel design of frequency tripler monolithic microwave integrated circuit (MMIC) using complementary split-ring resonator (CSRR) is proposed based on 0.5-μm InP DHBT process. The CSRR-loaded microstrip structure is integrated in the tripler as a part of impedance matching network to suppress the fundamental harmonic, and another frequency tripler based on conventional band-pass filter is presented for comparison. The frequency tripler based on CSRR-loaded microstrip generates an output power between ?8 and ?4 dBm from 228 to 255 GHz when the input power is 6 dBm. The suppression of fundamental harmonic is better than 20 dBc at 77–82 GHz input frequency within only 0.15?×?0.15 mm² chip area of the CSRR structure on the ground layer. Compared with the frequency tripler based on band-pass filter, the tripler using CSRR-loaded microstrip obtains a similar suppression level of unwanted harmonics and higher conversion gain within a much smaller chip area. To our best knowledge, it is the first time that CSRR is used for harmonic suppression of frequency multiplier at such high frequency band.     

A wideband stepped-impedance rectangular-ring resonator bandpass filter with multiple notched bands

A configuration of wideband bandpass filter (BPF) with multiple notched bands is presented. Proposed BPF is based on stepped-impedance resonator. By utilising dual stepped-impedance resonators in folded topology a rectangular-ring resonator is formed. Two notched bands in the passband are achieved without using asymmetrical coupled lines. In other words, the filter configuration is capable of producing notched bands. It should be noted that additional information on filter performance and design is presented. Measurement results are presented to approve propounded filter characteristics. The measured passband of the second proposed filter is from 3.68 to 10.2 GHz with insertion loss of –1.76 dB in the first passband at the centre frequency of 4.45 GHz. The measured notched band frequencies are about 5.45 and 7.95 GHz with rejection of –21.77 and –20.82 dB, respectively. The return loss in the passband is better than –11.4 dB.     

GaAs active structures with applications to microwave wideband 90° phase shifters and bandstop filters

Lumped-element second-order active filters are presented which can either be tuned to an all-pass response and then especially used in 90° phase shifters, or tuned to a bandstop response. Their structures have been chosen so that they can be easily implemented in the microwave domain. Preliminary simulations have shown that the filter having the highest-frequency capabilities results in a 90^° phase shifter operating up to the (6 GHz, 1O GHz) band, and that its centre frequency can be tuned up to 15 GHz when it is used as a bandstop filter.     

A novel approach to generate a chirp microwave waveform using temporal pulse shaping technique applicable in remote sensing application

Microwave photonics is a prominent field in which photonic technologies are used to empower and extend the functionalities of microwave system which is a very tough exercise to fulfil directly in microwave domain. A photonic technique to generate a high chirp rate arbitrary microwave waveform using dual-drive LiNbO₃ has been put forward and demonstrated experimentally in this paper. Nowadays in order to increase the Range-Doppler resolution of radar, the chirp microwave waveform is widely used. The Mach-Zehnder modulator (MZM) performs the intensity modulation techniques which can operate on the principle of electro-optic effect. In this paper, the authors used a very simple and straightforward method of producing chirped arbitrary millimetre waveform by change in phase at the two arms of dual-drive LiNbO3 MZM. The generated waveform has the 3 dB bandwidth of 12.6 GHz which exists in extremely high-frequency band applicable in high-frequency microwave radio relay, microwave remote sensing, radar range resolution and millimetre wave scanner. The proposed design is simpler, cost-effective and compact than the previously proposed model of chirped waveform generation using MZM and fibre Bragg grating.