Signal-interference Techniques Research Articles

RF Multi-Functional Input-Reflectionless Dispersive-Delay Structure With Sharp-Rejection Filtering Using Channelization Techniques

A class of RF multi-functional input-reflectionless dispersive-delay structure (DDS) with linear-type in-band group-delay variation and sharp-rejection bandpass-filtering capability is reported. It exploits a two-branch-channelized/balanced-type circuit with similar low-order reflective DDS units inside its channels, which are connected through input/output 3-dB quadrature wideband couplers. The adopted DDS unit is based on a coupled-resonator network with a frequency-dependent cross-coupling. It introduces a pair of complex transmission zeros (TZs) to shape the intended in-band group-delay profile. Unequal transmission-line-based phase-shifting sections are also inserted at the outputs of both channels. In this manner, an input-absorptive behavior and selectivity enhancement with TZ generation are attained by means of transversal signal-interference techniques at the overall input and output nodes, respectively. Moreover, as the transfer-function phase term of the interference action in transmission is linear with frequency, the total group-delay pattern is defined by the DDS unit of the channels. As practical validation, a 1.5-GHz proof-of-concept microstrip prototype is constructed and tested.

C/ X‐Band sub‐harmonic mixer using single oscillator and its design flow

This article describes the concept of designing a dual-band subharmonic mixer for C-band (4.3–5.3 GHz) and X-band (9.8–11.2 GHz) applications. This mixer exploits a single local oscillator (LO) (with a frequency of 2.6GHz) with two harmonics (second and fourth), in contrast to the two LOs, utilized in a conventional dual-band mixer. This configuration results in reduced system complexity and noise. The proposed mixer utilizes two signal interference technique (SIT)-based bandstop filters at the LO port, and a dual bandstop stub at the IF port to get good isolation. A prototype of the proposed configuration is fabricated on flexible Rogers' substrate RO5880B with 0.8 mm thickness. The total implementation area of the circuit is 43 mm × 32 mm. Circuit performance is validated by measurement. Based on the measured result, the mixer performs equally well in both bands with the conversion loss (CL) in the range of 6.1–10.9 dB. The measured LO-to-IF and LO-to-RF isolations are better than 25 dB, whereas the measured RF-to-IF isolation for both bands is better than 15 dB. Further, the measured value of 1 dB compression point is found to be − 8 dBm and − 7 dBm at 5.3 and 11.2GHz, respectively.

Design of high roll‐off frequency selective surface based on single‐layer SIW cavity with fully canonical filtering responses

In this paper, a novel design of high roll-off frequency selective surface (FSS) is proposed based on a single-layer substrate integrated waveguide (SIW) cavity. Fully canonical filtering responses with three transmission poles (TPs) and three transmission zeros (TZs) are obtained by employing transversal signal-interference techniques (TSITs). The FSS unit cell can be regarded as a combined triple-mode cavity consisting of one cross-slot resonator and two SIW cavities. By using the filtering coupling matrix, the FSS can be well designed and analysed. Accordingly, to verify the design concept, a prototype is fabricated and experimented. Measured and simulated results are in good agreement, showing high performances in terms of high roll-off and low profile.

High-Performance Wideband Balanced Bandpass Filter Based on Transversal Signal-Interference Techniques

A novel high-performance wideband balanced bandpass filter based on transversal signal-interference techniques is proposed in this article. Two signal-propagation paths consisted of coupled lines structure are used to realize two transmission zeros for the differential mode passband. Folding coupled lines are used to reduce the size of the balanced filter, and the source-load cross-coupling lines can generate additional transmission zeros to suppress the common mode signal. To validate the design, a prototype with center frequency at 2.2 GHz for long-term evolution (LTE)-band with 3-dB fractional bandwidths of 65.4% for the differential mode is designed and fabricated.

Implementation of a compact dual-band bandpass filter using signal interference technique on paper substrate

This paper exhibits the design and implementation of a compact dual-band bandpass filter on paper substrate. The proposed filter which works on the principle of signal interference technique has a parallel combination of short-circuited coupled line and an H-shaped network of transmission lines with open stubs. Due to the superposition of signals of the two transmission paths, a second order dual-band bandpass response with four transmission zeroes is achieved. To validate the proposed design, theoretical analysis using the lossless transmission line model is carried out and acknowledged. The developed dual-band filter prototype with center frequencies 1.17 GHz and 4.06 GHz has 3-dB fractional bandwidths of 82.56% (0.69–1.656 GHz) and 20.59% (3.645–4.481 GHz), respectively. The simulated and experimental results are in good congruence with each other. The proposed dual-band bandpass filter can be used in various wireless applications, for example, Global System for Mobile Communications (880–915 MHz), Aircraft surveillance (960–1215 MHz), Indian Regional Navigation Satellite System (1.164–1.188 GHz), Amateur radio (1.24–1.30 GHz), Global Positioning System (1.559–1.61 GHz), Satellite phones (1.616–1.626 GHz), and Satellite communication (3.7–4.2 GHz).

Signal interference‐based selectivity‐enhancement technique for omnidirectional monopole antenna

AbstractA compact monopole antenna with enhanced selectivity is designed based on circular disk monopole antenna and signal interference technique (SIT). It is composed of a circular disk monopole and a SIT‐based filtering structure consisting of two pairs of short‐circuited edge coupled stubs loaded on the feeding line. When the filtering structure is just loaded the feeding line, a filtering monopole antenna is obtained. A prototype is constructed, assembled, and tested. The measured results agree well with simulated one.

Bezpieczeństwo bezzałogowych systemów powietrznych w środowisku zakłóceń

This study considers signal interference as a form of non-kinetic warfare against unmanned aircraft systems (UAS). The practical purpose of this paper is to organize the theoretical knowledge and terminology concerning interference, while its cognitive purpose is to demonstrate that this recently recognized problem is a real threat to the safe use of unmanned aircraft systems. The research methods employed in this work – analysis, synthesis, abstracting and generalization – serve to determine the types of interference (i.e. primarily jamming and spoofing) and their characteristics in relation to unmanned aircraft. The paper organizes the theoretical knowledge by explaining the signal interference techniques and indicating the targets of attacks or objects of interest. Therefore, available non-kinetic energy UAS neutralization systems are analyzed with respect to their capabilities, tactical characteristics and technical specifications. Given the anticipated further development of unmanned aircraft systems technologies, signal interference carries serious implications for the safety of autonomous operation of these systems. The second important conclusion highlighted in this analysis is the absence of a legislative framework that would regulate the use of interference facilities. This gap in legal regulations implicitly permits their engagement against such crucial infrastructure as e.g. satellite devices for navigation systems – standard and critical equipment in the aviation.

A Wideband Subharmonic Mixer Incorporating Signal Interference Technique Based Isolation Circuit

A broadband (8.7 GHz – 11.5 GHz) performing passive sub-harmonic down-conversion mixer using signal interference technique (SIT) is demonstrated, designed and reported in this paper. The local oscillator (LO) frequency is half of the radio frequency (RF) for the 2xsub-harmonic mixer architecture; therefore, for the RF lying in the range 8.7 GHz to 11.5 GHz, required LO frequency range is 4.25 GHz to 5.65 GHz with 0.2 GHz fixed intermediate frequency (IF). With a broadband operation, designed prototype shows single sideband down-conversion loss in the range 9.6 dB – 12.6 dB. Moreover, large-signal testing infers an adequate linear trait of the proposed design, showing -3 dBm and 11.32 dBm for the 1 dB compression point and third order input intercept point, respectively.

A Wideband Subharmonic Mixer With Low Conversion Loss and High Port-to-Port Isolations

A design of a diode based wideband subharmonic mixer (SHM) with low conversion loss and high port-to-port isolations is reported. To achieve low conversion loss, for a given diode, the radio frequency (RF) and intermediate frequency (IF) signals at the respective port should remain unattenuated over the frequency range of interest. At the same time, it has to reject unwanted signals over a wide bandwidth. The excellent wideband bandstop filtering behavior of signal interference technique is exploited for this purpose. The mixer is designed to operate over the RF band 8.5-11.5 GHz. The local oscillator (LO) frequency is tuned to keep IF fixed at 200 MHz. Measured minimum conversion loss is obtained as 6.05 dB while the theoretical limit of conversion loss for the chosen diode is 4.68 dB. Measured LO-to-RF and 2LO-to-RF isolations are better than −30 dB (maximum −50 dB) and −59 dB (maximum −73 dB), respectively, over the entire operational band. Large signal measurements show that the 1-dB compression point is −1 dBm and the third order intercept point is 10 dBm. Simplicity in circuit topology is another significant feature.

Low loss and high fabrication tolerant phase shifters using signal interference technique

This article presents a new design of differential phase shifters based on signal interference technique. Two transmission line sections joined at their both ends is used as the phase shifting unit. Properties of the phase shifters are solely determined by the lengths and characteristic impedances of connecting transmission line sections. A lossless transmission line model is used to obtain design equations and design graphs for the phase shifters. It is observed that a fixed reference line can provide 0° to 90° differential phase shifts. While a varying reference line provides 0° to 360° differential phase shifts. Six differential phase shifters are fabricated to check the theoretical predictions at 5 GHz. All of them provide excellent phase and insertion loss performances. The main advantages are simple design technique and low insertion loss. Since no coupled-line or open-stub is used, the structure can accept higher fabrication tolerances compared to other popular methods.

Wideband Filtering Phase Shifter Using Transversal Signal-Interference Techniques

A wideband filtering phase shifter is presented in this letter using transversal signal-interference techniques. The proposed structure creates two signal-propagation paths by introducing extra coupling between two short-ended stubs. Cascaded coupled-line sections and parallel short-ended stubs can generate a constant passband and multiple transmission zeros (TZs) in the stopband and meanwhile provide the arbitrary value of phase shift within the filtering band range. The positions of TZs and phase shift range can be easily controlled. Explicit relations between the objective filtering band and the related parameters are given, and cases with different in-band phase shift values are studied. To validate the design, a prototype is built, simulated, and tested using microstrip lines. The experimental results agree with the predicted ones, demonstrating that the device can realize any given in-band phase shift with a wideband filtering response.

A <inline-formula> <tex-math notation="LaTeX">$C$ </tex-math> </inline-formula>-Band Compact Wideband Bandpass Filter With High Selectivity and Improved Return Loss

In this letter, a C-band compact wideband bandpass filter (BPF) with high selectivity and improved return loss (RL) is proposed. Two pairs of short-circuited stubs are employed on a transmission-line model to generate three transmission poles and two transmission zeros (TZs), where the odd- and even-mode analysis is used to analyze the resonant frequencies of the BPF. By applying the transversal signal-interference technique, two additional TZs can be generated in the upper and lower stopbands, respectively. The measured results show that the 3-dB fractional bandwidth is 62.8% at the center frequency of 5 GHz. The RL and the insertion loss within the passband are better than 22 and 0.6 dB, respectively. Moreover, the roll-off rate is up to 100 dB/GHz.

Compact dual-wideband bandpass filter for wireless applications

In this paper, a compact dual-wideband bandpass filter with two reflection zeros in both passbands and two transmission zeros in the stopband, based on a signal interference technique is presented. The proposed filter is formed by a transmission line connected in parallel with a series connection of transmission lines and a short circuited edge coupled line. A simple lossless transmission line model is used to derive the condition for transmission zeros. To validate the theoretical predictions, a compact dual-wideband bandpass filter has been fabricated to operate at GPS and INSAT Satellite bands. The measured 3 dB passband fractional bandwidths are 82.16% and 41.52%, respectively.

Compact, high selectivity and wideband bandpass filter with multiple transmission zeros

This paper presents the design of a compact, high selectivity and wideband bandpass filter based on signal interference technique. The proposed filter consists of open coupled line and stepped impedance modified Π-type (SMΠ) transmission line with short circuited stubs in transmission path 1 and path 2, respectively. Due to the superposition of signals of the two transmission paths, a fourth-order wideband bandpass filter with six transmission zeros can be obtained from 0 to 2f0 (f0 is the operating frequency). A bandpass filter prototype centring at 0.9 GHz, with 3 dB fractional bandwidth of 50% is designed, fabricated and tested. Good agreement is found between the simulated and experimental results.

A Negative Group Delay Microwave Circuit Based on Signal Interference Techniques

A novel self-matched negative group delay (NGD) microwave circuit based on the signal interference technique is proposed to eliminate the performance degradation due to the temperature-dependent resistance variation. The proposed circuit consists of unequal power dividing/combining structures and coupled-line phase shifter, which can be directly synthesized with prescribed NGD time and insertion loss (IL). To verify the proposed method, an NGD circuit with a size of $0.41\lambda _{g}\times 0.41\lambda _{g}$ is designed and fabricated. From the measured results, NGD time of −2.09 ns at the center frequency of 1.016 GHz is obtained with NGD bandwidth of 14.2% (0.944–1.088 GHz), in which the IL is less than 18.1 dB and the return loss is greater than 33 dB.

Behavioural digital modelling of lossy frequency‐periodic microwave passive filters

The theoretically synthesised power transmission response of several classes of RF/microwave passive filters is frequency periodic. Examples of these filters include those exploiting signal-interference techniques as well as those consisting of stub-loaded circuit networks. A behavioural z -plane digital modelling of these ideally synthesised frequency-periodic high-frequency filters has been recently proposed. It led to innovative explanations for commonly observed spurious resonant peaks and circuit redundancies in suboptimal designs. This work reports on a novel behavioural discrete-time modelling methodology for frequency-periodic microwave lossy filters. It considers for the first time the effect of high-frequency losses by introducing a σ parameter on the originally lossless transfer function. For practical-validation purposes, the manufacturing and characterisation of a new type of generalised stub-loaded-based extended-upper-stopband bandpass filter along with its lossy digital modelling are shown.

Compact dual-band bandpass filter based on signal-interference techniques

To realize good isolation between two signal passbands, a dual-band bandpass filter (BPF) in this article was presented using signal-interference techniques, in which five open loop resonators are adopted. The proposed filter topology is made up of two signal transmission paths in parallel, under signal-interference principles, overlap section of two original passbands, decided respectively by two different transmission paths, is selectively removed from the combined passband, as a result, two aim passbands are realized. In addition, good isolation between two aim passbands is established due to two new transmission zeros, produced by adopted signal-interference techniques. At last, good agreement can be observed between simulation and measurement.

Analysis and design of high‐order wideband bandstop filters with sharp rejection

High-order wideband bandstop filters (BSFs) with sharp rejection based on transversal signal-interference techniques are analysed and designed. By choosing different open stubs and open/shorted coupled lines, third/fifth/seventh-order wideband BSFs with six transmission zeros from 0 GHz to 2 f 0 ( f 0 is the centre frequency of the stopband) can be achieved, respectively, due to the superposition of signals from the two transmission paths. The bandwidths of the three high selectivity wideband BSFs can be easily adjusted by changing the characteristic impedance of the resonant structures of the two transmission paths. Three wideband BSF prototypes with 3 dB fractional bandwidths of 113% (1.74-6.26 GHz), 115% (1.85-6.45 GHz) and 112.3% (1.76-6.25 GHz) are designed and fabricated for demonstration. The theoretical and measured results are in good agreement and show good in-band filtering performance and high selectivity.

A Compact Bandpass Filter Based on Right- and Left-Handed Transmission Line Sections

A new type of a compact second-order bandpass filter (BPF) with two transmission zeros based on transversal signal-interference technique is proposed in this letter. Unlike other transversal filters published, the proposed structure is composed of artificial right- and left-handed transmission lines, instead of traditional distributed transmission line sections. Such an approach is not only helpful in size reduction, but also promising for frequency-asymmetrical stopband performance achievement. Design equations and guidelines to adjust filter performance are provided in the letter. To validate the proposed design approach, a two-pole BPF was designed, fabricated using multilayer liquid crystal polymer (LCP) technology and measured.

Compact bandpass filter based on two meandered parallel-coupled lines in different lengths

A new compact bandpass filter based on two meandered parallel-coupled lines of different lengths in shunt is presented, using the signal-interference technique, this filter obtains a low insertion loss and sharp rejection. A set of analytical formulas and guidelines for the design of the bandpass filter are provided in two theoretical analysis methods. According to the number of attenuation poles of the reflection coefficients in the passband, it can be summed up two types of filters. To validated this topology, two wideband bandpass filters centered at 3 GHz are built to verify the theoretical prediction, the measured frequency response of the filter agrees excellently with the predicted result.