Suppression Of Spurious Harmonics Research Articles

Evanescent‐mode bandpass filter using D‐shaped slotlines for spurious harmonic suppression

AbstractA novel miniaturized evanescent‐mode substrate integrated waveguide (SIW) bandpass filter with D‐shaped slotlines for spurious harmonic suppression is proposed in this letter. Closed‐form equations for the proposed evanescent‐mode SIW cavity are summarized and two D‐shaped slotlines are etched together as a pair by the face‐to‐face style to obtain the designed lowpass feature, which could be utilized to improve the out‐of‐band spurious harmonic rejection level. To validate the feasibility of this method, a miniaturized evanescent‐mode SIW filter with D‐shaped slotlines is designed and measured. The measured results show that this filter operates at 1.05 GHz with 2.4 dB insertion loss and 3.8% bandwidth. The out‐of‐band spurious rejection is lower than 16 dB up to 11 times of the higher cutoff frequency of the passband. All test results are in good agreement with the simulation results.

Electrically Coupled Folded Arm Resonators with the Feedline Patch Antenna for Spurious Harmonic Suppression and Bandwidth Improvement

This paper presents a new design of the filtering antenna with a quasi-elliptic function response. The basic structure of the proposed filtering antenna is consists of a four-folded arms open-loop resonator (OLR). The proposed filtering antenna is simulated, improved and, analyzed by using 3D Computer Simulation Technology (CST) electromagnetic simulator software. The design has good spurious harmonic suppression in the upper and lower stopbands. The Insertion Loss of the proposed filtering antenna IL=0.2 dB and the Return Loss RL= -25.788 dB at the center frequency fo=5.75 GHz. The passband bandwidth which is relatively wide, and equal to 0.793 GHz. The microstrip filtering antenna circuit shows good design results compared to the conventional microstrip patch antenna. The filtering antenna design circuit with etched ground plane structure also has good design results compared to the filtering antenna design which has a complete ground plane structure.

Compact wide stopband microstrip lowpass filter using polygon patches and meandered lines

In this paper, a low pass filter based on T-Shaped resonator is presented. The T-Shaped resonator consists of meandered lines and rectangular patches. Also, the LC model and transfer function of the proposed resonator is presented. For suppression of spurious harmonics, a bandstop structure consists of hexangular patches and open stubs has been utilized. Finally, the wide stopband microstrip lowpass filter with cutoff frequency 2.72 GHz has been simulated, fabricated and measured. The LPF has good characteristics such as wide stopband and insertion loss lower than 0.18 dB in the passband region. The rejection level is less than -20 dB from 2.98 up to 21.3 GHz. The filter size is 10.5 mm×12.7 mm, or 0.131 λ<sub>g</sub>× 0.158 λ<sub>g</sub>, where λ<sub>g</sub> is the guided wavelength. The measured and simulated results of the filter is in good agreement with each other, which show the merits of low insertion loss and wide stopband.

Spurious harmonic suppression in compact coupled-line bandpass filter with asymmetric perturbations

ABSTRACTPresent article exhibits the design of a third-order compact parallel-coupled line bandpass filter at 5.25 GHz having asymmetric perturbations to suppress the second harmonic. Initially, the effects of compactness on filter characteristics have been studied by synthesising the distributed filter network into its equivalent circuit model. The design has been initiated by computing the unit cell model, which leads to the first-order and third-order design instances with an improvement in compactness over the traditional parallel-coupled line filter. In contrary, compactness in the filter characteristics degrades the second harmonic level subject to enhanced imbalances among the odd- and even-mode velocities at the coupled lines. Subsequently, the improvement in the harmonic suppression of 53 dB and 58 dB has been achieved by incorporating different non-uniform perturbations to the outer and coupled edges of the compact filters. Accordingly, compactness of 58% and 71% have been obtained subject to the folded and in-line designs over the conventional layout.

Standard Cell-Based Ultra-Compact DACs in 40-nm CMOS

In this paper, very compact, standard cell-based Digital-to-Analog converters (DACs) based on the Dyadic Digital Pulse Modulation (DDPM) are presented. As fundamental contribution, an optimal sampling condition is analytically derived to enhance DDPM conversion with inherent suppression of spurious harmonics. Operation under such optimal condition is experimentally demonstrated to assure resolution up to 16 bits, with 9.4–239X area reduction compared to prior art. The digital nature of the circuits also allows extremely low design effort in the order of 10 man-hours, portability across CMOS generations, and operation at the lowest supply voltage reported to date. The limitations of DDPM converters, the benefits of the optimal sampling condition and digital calibration were explored through the optimized design and the experimental characterization of two DACs with moderate and high resolution. The first is a general-purpose DAC for baseband signals achieving 12-bit (11.6 ENOB) resolution at 110kS/s sample rate and consuming $50.8\mu \text{W}$ , the second is a DAC for DC calibration achieving 16-bit resolution with 3.1-LSB INL, 2.5-LSB DNL, $45\mu \text{W}$ power, at only $530\mu \text{m}^{2}$ area.

A Theoretical Model of Dual Tunable Optoelectronic Oscillator

A theoretical model of an electronically tunable multi-loop optoelectronic oscillator (OEO) based on photonic and microwave multiferroic delay lines has been developed. The theory takes into account a dispersion of electromagnetic waves in optical fibers and a dispersion of spin-electromagnetic waves in ferrite-ferroelectric structures. An expression for transfer function of the OEO circuitry was derived. The theory enables one to calculate transmission characteristics and suppression of spurious harmonics of the multi-loop OEOs. The features of both magnetic and electric tunabilities are investigated.

Varactor‐tunable dual‐band filtering low‐noise amplifier

AbstractDesign and development of a tunable dual‐band filtering LNA has been presented in this paper. The center frequency of the lower band is continuously tuning with applied dc voltages. The center frequency of lower band has a tuning range of 2.0–2.5 GHz; while that of upper band is fixed at 5 GHz. Power consumption of our circuit is 28 mW. Overall size of proposed device is 0.96λg × 0.34λg, where λg is the guided wavelength at lower frequency. One ATF36163 GaAs HEMT is used as the active device in our circuit. Measured per stage gain of lower band is varying from 8 to 1.6 dB; while that of upper band is 5.4 dB. Measured noise figure of lower band is 2.4–3.4 dB; while that of upper band is 2.5 dB. Proposed filtering LNA has improved selectivity and spurious harmonic suppression with measured stopband attenuation of 45 dB. To author's knowledge, the investigation of tunable multiband and multifunctional device for highly improving the level of integration of the multiband RF front‐end design is reported for the first time.

Harmonic suppressed coupled stepped-impedance resonator based dual-band tunable bandpass filter

In this paper, a tunable dual-band bandpass filter (BPF) based on a varactor-loaded coupled stepped-impedance resonator is presented. Transmission matrices techniques are employed to explain the working concept of proposed tunable BPF. For validating the proposed concept, a hardware prototype is fabricated and characterized. As per the measured results, when the center frequency of the lower band is tuning from 2.15 to 2.40 GHz, the upper band is fixed at 4.5 GHz; and when the center frequency of the upper band is tuning from 4.5 to 4.75 GHz, the lower passband almost remains constant at 2.25 GHz. Proposed tunable filter is capable of working at higher passband frequencies. Spurious harmonic suppression up to 15 GHz is demonstrated. Center frequency of dual-passband is tunable using only two dc control voltages.

Band Notched UWB-BPF Based on Broadside Coupled Microstrip/CPW Transition

ABSTRACTA planar band notched ultra-wideband (UWB) bandpass filter based on broadside coupling of microstrip/co-planar waveguide (CPW) transition is proposed and implemented. The UWB filter topology is made up of microstrip lines on the top coupled in broadside fashion to an open ended CPW in the ground plane. Dual narrow notches at 5.2 and 7.9 GHz are implemented by etching two meander shaped defected ground structures in the CPW under the microstrip lines. A wideband stopband for improved isolation is obtained with the suppression of spurious harmonics by the attenuation poles generated by the spur line structures embedded in the input and output feeding lines. The proposed structure exhibits good frequency characteristics and is of compact size.

Spatial and frequency selection of waves in pseudoperiodic slow-wave structures

The principles of the joint selection of spatial harmonics and the extension of passbands of pseudoperiodic slow-wave structures (SWSs) are considered. Relationships for calculating the continuous spectrum of spatial harmonics are presented. Recurrence formulas for determining the input reflection coefficient from an SWS section are derived and used for the analysis of frequency characteristics. Selection of spatial harmonics and transformation of passbands in pseudoperiodic folded SWSs (a folded waveguide, an interdigital structure, etc.) are investigated. The possibility of extraction of either the first or the fundamental spatial harmonic in a frequency band from 30% to one octave and simultaneous suppression of spurious harmonics, including backward waves, is demonstrated. Owing to this feature, pseudoperiodic SWSs can be used in high-power wideband traveling-wave tubes.

A wide-band microwave photonic phase and frequency shifter

Advanced radar deception systems require wide-band devices which perform microwave processing of frequency and phase information. A wide-band microwave photonic phase shifter was constructed which is capable of imposing greater than 2/spl pi/ phase shift to microwave signals in the 2-18-GHz frequency range. The maximum standard deviation from the phase setting was 10/spl deg/ (7/spl deg/ typical). The phase shifter was then incorporated into a frequency translation architecture. The carrier suppression obtained was 50 dB with a spurious harmonic suppression of 23 dB.