A planar monopole loaded with composite right/left-handed transmission line (CRLH-TL) for broadband LTE mobile phone is presented. The CRLH-TL with a propagation constant of zero is added to widen the input impedance bandwidth of the antenna. The proposed antenna covers the LTE700/2500/GSM850/900/1800/1900/UMTS2100 and WLAN2400 bands. Impedance bandwidths of VSWR<2.5 (S11<-7 dB) ranging from 675 to 1010 MHz and 1690 to 2550 MHz are obtained. The size of the monopole is 60×16×1mm3 which is smaller than most of the LTE antennas. Detailed design considerations of the monopole are described. A prototype is fabricated and tested. Both simulated and experimental results are discussed.
In this paper, a miniaturized dual-band bandpass filter with high selectivity and band-to-band isolation is presented. The filter consists of two quarter-wavelength stepped impedance resonators (SIRs) which share a common grounded via-hole and two symmetrical half-wavelength SIRs which are embedded into the inner space to reduce the size of the filter. Two independent mixed coupling paths which are created by the coupling between these SIRs introduce two different passbands. Five transmission zeros (TZs) are generated near the two passbands to achieve high frequency selectivity and band-to-band isolation. To validate the design theory, a dual-band filter operating at 2.45 and 5.2 GHz was designed and fabricated. The size of the proposed filter only occupies 0.095λg × 0.109λg and the measured 3 dB fractional bandwidth (FBW) of the first and second passbands is 11.5% and 7.4% respectively. The measured results are in good agreement with the simulated results.
In this paper, a microstrip double-layered reflectarray element is studied. The unit element consists of a circular patch sandwiched between two substrates and a cross-slotted circular patch placed on the top-most surface. The radii of the two circular patches as well as the cross-slot lengths are varied simultaneously for controlling the phase range and the gradient of the reflection phase angle. Study shows that the sensitivity of the reflection phase angle can be made slower by utilizing substrates with lower dielectric constants. The component performance is studied using a rectangular waveguide and good agreement is found between thesimulation and experiment. A wide reflection phase range of 681.82° with loss magnitude of less than -1 dB is achievable in the reflection phase angle. A complete parametric analysis has been conducted to study the reflection characteristics of the proposed reflectarray unit element.
A novel 180˚ out-of-phase power divider based on stepped-impedance slotline is presented in this article. This power divider employs one T-junction formed by microstrip line and slotline to obtain two out-of-phase dividing signals. Stepped-impedance slotline and lumped resistor are introduced to improve the isolation between output ports. The experimental data show that the proposed power divider has good performance on insertion loss, return losses, isolation, phase balance, as well as group delay over the wide band 5 GHz-10 GHz.
In this paper, a compact tri-band bandpass filter (BPF) using multi-stub-loaded resonator with controllable frequencies is presented. The multi-stub-loaded resonator consists of a main transmission line, two open stubs and a short stub. Characterized by using even- and odd-mode analysis, it is found that the resonator consists three modes, and the modes can be controlled individually, which enables convenient designs of tri-band BPFs. To demonstrate the proposed idea, a tri-band BPF with operating frequencies of 2.45, 3.8 and 5.15 GHz is implemented. Five transmission zeros are generated near the passband edges, resulting in high skirt selectivity. The total size of the filter is 0.19λg × 0.13λg, featuring compact size. The comparisons of the measured and simulated results are presented to validate the theoretical predications.
In this paper, a novel and compact dual-band filter with enhanced upper stop characteristics has been presented. Dual band pass filter characteristics are achieved by introducing transmission zero (TZ) in pass band of band pass filter (BPF). The wide band pass filter (BPF) is implemented by combining low pass filter characteristics (i.e. stepped impedance resonator) and high pass filter characteristics (i.e. short stubs). Closed rectangular ring resonator (CRRR) and open loop rectangular ring (OLRR) combination is used to produce two transmission zeros (TZs). One TZ is placed on the pass band of BPF such that resultant filter characteristic consists of two pass bands. However, the second TZ is placed at edge of the pass band in BPF to improve skirt selectivity. The two pass bands are designed to cover two popular wireless bands namely WiMAX (center frequency f1 (3.5 GHz) and WLAN (center frequency f2 (5.7 GHz)) bands i.e. 3.35-3.65 GHz and 5.5-5.85 GHz respectively. Equi-ripple low pass stepped impedance resonator (SIR) filter response is responsible for improved and spurious free upper stop band (>20 GHz i.e. >6f1) and also provides sharp skirt attenuation at upper stop band. The proposed filter is implemented on an RT/Duroid 5880 (εr=2.2) substrate with thickness of 0.785 mm and surface area of 19 × 12 sq. mm. Good agreement between simulated and measured results ensures that the proposed filter is a suitable candidate for modern dual band communications.
A compact multiple-input-multiple-output (MIMO) antenna that covers the WLAN (2.4 GHz) and UWB (3.1-10.6 GHz) bands for wireless device applications is presented. The proposed antenna consists of two open L-shaped slot (LS) antenna elements and a narrow slot on the ground plane. The antenna elements are placed perpendicularly to each other to obtain a high isolation, and the narrow slot is added to reduce the mutual coupling between antenna elements at the WLAN band (2.4 GHz). The presented MIMO antenna has a small size of 40×40mm2, and the prototypes of antenna is fabricated and measured. The measured results show that the antenna has an impedance bandwidth of larger than 2.4-10.6 GHz with the mutual coupling less than 20 dB in WLAN band and 18dB in 3.1-10.6GHz, making the antenna a good candidate for portable applications.
A tunable electromagnetic-bangap (EBG) structure based on a double layer slotline using plasma is proposed. The plasma permittivity can be tuned by the electron density. The idea of integrating periodical plasma elements inside the slot to tune the stopband is investigated. An electron density and an electron collision frequency equal to 1.75 1013 cm-3 and 1010 s-1 respectively, are the plasma parameters selected in this study. The simulations reveal a shift rate of the second stopband equal to 6%. A new configuration of the structure is also proposed to adapt it better to the experimental requirements. Based on the simulation results, adding the plasma elements to the modified configuration shifts the stopband 4% and reduces its bandwidth by 43% (at -20 dB).
A compact millimeter-wave (MMW) wideband high-gain antenna is proposed and implemented. The development is based on the design principle of wideband Fabry-Perot resonator antennas (FPRAs). The antenna consists of three dielectric slabs and a PEC ground, and it is fed by a rectangular waveguide. All slabs are used to form the superstrate that exhibits the increasing reflection phase at the designed frequency band. Size reduction of the superstrate is carried out to enhance the bandwidth of the antenna. The effect of ground size and resonant frequency shift due to size reduction of the superstrate were studied. A wide bandwidth of over 30% was finally obtained, and measurements of the fabricated prototype validate the theory and simulation results.
A compact printed dipole antenna with wide impedance bandwidth is proposed in this paper. This antenna consists of a pair of radiation metal arms and a microstrip-to-slotline transition structure. At the end of the feeding slotted line, a beveled slot with stepped connection structure is designed to realize an offset feeding structure for feeding the dipole antenna. By using the beveled offset feeding structure, the bandwidth of the dipole antenna is significantly improved. The microstrip-to-slotline transition is used as an integrated balun to realize a balanced feeding for the dipole antenna. To demonstrate the effectiveness of the proposed design, a prototype of the designed antenna is fabricated and measured. The measured results show that the designed dipole antenna achieves a gain of 2.2-4.4 dBi across a wide impedance bandwidth from 2.65 GHz to 17.5 GHz with a compact size (33 mm×16 mm). The performance of the proposed dipole antenna is also compared with some similar printed dipole antennas with respect to overall size, substrate dielectric constant, impedance bandwidth and antenna gain.
A printed slot antenna fed by a microstrip line with a diamond-shaped tuning stub for bandwidth enhancement is proposed and experimentally validated. The simulated results show that the impedance matching of the proposed rotated slot antenna is greatly affected by the dimension of the slot and by the size and the position of the diamond-shaped tuning stub. The experimental results demonstrate that the impedance bandwidth is over 123% for |S11|≤-10 dB ranging from 2.80 to 11.81 GHz. Moreover, the proposed antenna has a small size, and stable and omnidirectional radiation patterns are observed within the operating bandwidth.
A novel horizontally polarized (HP) antenna with omnidirectional pattern is presented in this paper. The proposed antenna applies the concept of rotating electric field method to conventional slot dipoles. Two CPW-fed slot dipoles are placed in a perpendicularly conjugate form. By properly arranging the magnitude and phase of input signals, the omnidirectional pattern can be synthesized at broadside. A prototype is developed at the 2.6 GHz band, which offers a horizontally polarized omnidirectional radiation pattern with gain of 2.5-3.4 dBi, and the measured antenna efficiency is greater than 73% through the operating band (2.4-2.8 GHz). Furthermore, a 20-dB polarization purity is achieved in this design. The overall volume of the proposed antenna is 22×22×90 mm3 (0.19λ0×0.19λ0×0.78λ0). Distinct from the other proposed HP antennas provided with planar geometry, this antenna is slim in shape, and it can be readily integrated with vertical dipoles to form a polarization diversity system in current wireless router and AP applications.
The design and implementation of millimeter-wave full-band waveguide-based spatial power divider/combiner are presented in this paper. The divider/combiner is based on a compact waveguide-to-microstrip (Wg-Ms) probe-array transition structure, providing full-band frequency coverage and low insertion loss. Efficient design and analysis method for this type of power divider/combiner is developed using spectral domain method combined with the image theory. Ka-band two-way (1×2) and four-way (2×2) power combining structures are analyzed and optimized. The performances of the both optimized power dividers/combiners are evaluated by experiments in back-to-back configurations. The measured overall insertion loss for the 1×2 power divider/combiner is better than 1.4dB over the entire Ka-band, which demonstrates the low-loss performance of the divdier/combiner. The optimized 2×2 power divider/combiner shows a same performance as the 1×2 structure without any degradation in operating bandwidth and insertion loss.
A novel compact slotline power divider is proposed in this article. This presented power divider employs a novel configuration with one lumped resistor, which makes it surpass most antecedent UWB power dividers based on microstrip-to-slotline transitions in aspect of isolation between output ports and return losses at output ports. The simulated and measured results illustrate the good performances of the novel power divider on return losses at all ports, isolation, amplitude and phase balances between output ports, as well as group delay over the wide frequency band from 3.8 GHz to 10.4 GHz.
This paper presents a novel compact dual-tri bandpass microstrip filter employing meander and open stub loaded resonators. With the proposed technique, a simple transformation from dual-band to tri-band BPF is realized. A novel structure using embedded resonators is designed to generate multi-band response. The main resonators control the low-band resonant frequency, the meander resonators control the two high-band resonant frequency and the open stub resonators control the high-band resonant frequency. The meander/stub resonators are embedded into the main spiral resonators, which makes the filter compact where its size is reduced by 64% compared to traditional filters. Passbands improvements and high selectivity are realized by the short circuit stubs which generate additional transmission zeros. The proposed filter has advantages such as low insertion loss, compact size and high selectivity. The theory is validated using the commercial full-wave solver CST 2012. Finally, the proposed structure is implemented and the measurement results are found to be in good agreement with the simulation results.
A broadband CPW-fed circularly polarized square slot antenna for ultra-high-frequency (UHF) radio frequency identification (RFID) applications is proposed. It consists of a square slot embedded with a spur line along diagonal and an F-shaped feeding structure. The proposed antenna achieves an imped-ance bandwidth about 307 MHz (34.6% @886 MHz) and a 3 dB axial ratio (AR) bandwidth about 232MHz (24.3% @954 MHz). The 3 dB AR beam-width is about 96 degrees over the UHF band of 840-960 MHz. The proposed reader antenna based on CPW structure is easy to integrate. With the symmetry and bidirectional radiation pattern, there are less readers needed in some applications, such as access con-trol, than the reader with unidirectional pattern, which will definitely decrease the implemented cost. Therefore, this universal design with desired performance across the entire UHF RFID band (from 840 MHz to 960 MHz) can be applied to all the UHF RFID applications worldwide. Detailed considera-tions of the design and main parameters will be studied in this paper.
A compact UWB (Ultrawideband) MIMO (Multiple-input multiple-output) antenna with asymmetric coplanar strip (ACS)-fed structure is proposed in this paper. The antenna consists of two modified ACS feeding staircase-shaped radiation elements which are orthogonally placed, and the wideband isolation is achieved through a fence-like stub between them. The effectiveness of the fence-like stub is analyzed. Measured results show that the presented antenna can achieve a broad impedance bandwidth (|S11|≤-10 dB) of 3.1-11 GHz with good performance in terms of isolation >15 dB. Radiation patterns and correlation coefficient (ECC) denote the consistent diversity performance across the entire UWB bandwidth. By introducing the ACS-fed structure, the antenna size can be considerably reduced to 43.5 mm×43.5 mm×1.6 mm compared to the recently published UWB MIMO antennas, which makes the antenna suitable for portable UWB MIMO applications.
Two different kinds of artifical magnetic conductors (AMCs) are used to reduce the out-of-band radar cross section (RCS) of microstrip patch antenna. The principle of this method is based on the high impedance characteristic of the AMC structures. The simulated results show that out-of-band RCS of the proposed patch antenna is much lower than that of the reference antenna over the frequency range of 5-12 GHz. The in-band scattering characteristic of the microstrip patch antenna is analyzed, and two slots are cut on the patch antenna to reduce in-band RCS. Prototypes of the reference and designed antennas are manufactured and tested, and the measured and simulated results of the two antennas are in good agreement.
In this paper, a circular microstrip patchcentrally etched with a cross slot is studied. The slot dimensions are varied for controlling the reflection lossand thephase range of a reflectarray. It is found that the dominant TM mode of the slotted circular patch can be easily excited, and the slot length can be varied to function as a phase-changing parameter. Cross slots with equal and unequal arms are investigated. Study shows that the slope of the S curve can be made slow-changing by increasing the slot width. A maximum reflection phase range of 328.68º is achievable in the S curve. Rectangular waveguide method has been deployedfor simulating and verifying the design idea. Reasonable agreement is found between the measurement and simulation.
The design of a differential K-band UWB(Ultra Wideband) Short Range Radar (SRR) transmitter in 90nm bulk CMOS is presented. Implementation of SRRs in deep submicron CMOS technology is attractive, in terms of cost and monolithic integration of RF font-end with signal base-band processor. The transmitted pulse bandwidth limits the range resolution of the radar system. Due to the wide bandwidth and high frequency of CMOS implementation, UWB transmitters in the K-band are challenging to make and critical for the system performance. The design presented is based on frequency up conversion using a double balanced mixer. The differential output is combined and matched with the antenna using an on-chip balun. To mitigate local oscillator (LO) leakage of UWB differential transmitters we propose a new Pulse Generator (PG) design. A switching technique is used to minimize the LO leakage enabling continuous wave operation with very wideband pulses. Measurements of the proposed transmitter achieves a -10 dB bandwidth (BW) of 5 GHz. Using a Pulse Repetition Frequency (PRF) of 100 MHz the peak average power is -40 dBm. Compared to measured transmitter performance of a single balanced mixer design, the LO leakage of this dual balanced mixer is decreased with more than 20 dB, and is lower than the peak average power of the pulse. It consumes 11 mW from a 1.2 v supply where 6 mW is from the LO.