A right-angle wideband transition between differential microstrip line and rectangular waveguide

This paper presents electromagnetic band gap (EBG)-based periodic microstrip lines and balanced (differential) microstrip lines. Specifically, it is shown that through a proper modulation of the strip width in a microstrip transmission line, a stopband with controllable characteristics can be obtained. These EBG structures are then applied to differential microstrip lines, where it is shown that it is possible to achieve common-mode rejection in a certain frequency band, keeping the differential signals unaltered in that band. This is an interesting approach to implement common-mode suppressed differential microstrip lines without ground plane etching.

In modern radar systems, often planar transmission lines, such as stripline, microstrip line or coplanar waveguides are used to distribute signals between different components. In this paper we present a way to realize low-loss distribution with embedded waveguides by radiating laterally from an MMIC housed in an eWLB package into a waveguide. In this work, the waveguide is made half of a 3d-part and the other half is realized as cavity in a low cost non RF printed circuit board. For a proof of concept study, the chip was replaced by a differential microstrip line back-to-back structure. Different manufacturing tolerances and their impact on the performance will be shown. A prototype was built, measured and compared to the simulation results. It will be shown that the splitted PCB-waveguide channel has a loss of 0.11 dB/cm and that the transition from PCB-waveguide to differential microstrip line will lead to an insertion loss of 2.55 dB.

In this article, a novel method to suppress differential-to-common mode conversion noise in differential serpentine delay microstrip lines (DSDMLs) is proposed. To suppress the remnant mode conversion noise, embedded coupled lines are adopted in the parallel traces section of DSDMLs. Embedded coupled lines can minimize the timing delay between even- and odd-modes in the parallel traces section. In specific dimensions, embedded coupled lines propagate even- and odd-mode signals with the same velocity without changing the differential-mode impedance, so DSDMLs with embedded coupled lines can suppress differential-to-common mode conversion noise without degrading differential-mode signal quality. In simulations, the proposed DSDMLs exhibit about 93.0% suppression of the peak common-mode conversion voltage compared with conventional DSDMLs, regardless of the length of the parallel traces section of DSDMLs. The performance of our proposed DSDMLs is verified by conducting measurements with millimeter-scale test boards in the frequency and time domains. The test board exhibited 78.7% suppression of common-mode conversion noise without degrading the differential insertion loss compared with conventional DSDMLs. Simulations and measurement results exhibited good agreement.

Novel resistor-free differential microstrip lines prototype loaded with lossy metamaterial is proposed to achieve wideband common-mode (CM) absorption. The metamaterial is constructed by a chain of lossy complementary split-ring resonators (CSRRs), which are etched on the ground plane. Different from the CM absorption realized by lumped resistors, this work utilizes the inherent dielectric and conductor losses introduced by the differential microstrip lines and CSRRs to absorb CM energy. Furthermore, CSRRs are designed with gradual perturbation to broaden the CM absorption band. The lossy even-mode equivalent circuit models are established and analyzed to reveal the CM absorption mechanism. In order to verify the proposed strategy to design resistor-free differential microstrip lines with CM absorption, a sample was fabricated and measured. The measured <inline-formula> <tex-math notation="LaTeX">$S_{\mathrm {cc21}}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$S_{\mathrm {cc11}}$ </tex-math></inline-formula> are kept below &#x2212;10 dB simultaneously from 4.3 to 5.65 GHz with 27.4&#x0025; fractional bandwidth, where the CM energy is absorbed over 80&#x0025; by the dielectric and conductor losses. Meanwhile, the low insertion loss of <inline-formula> <tex-math notation="LaTeX">$S_{\mathrm {dd21}}$ </tex-math></inline-formula> below 6 GHz as well as the good differential-mode eye diagrams demonstrates that good signal integrity of differential signals is kept.

In this letter, a comparative analysis is carried out between the mechanism of mode conversion in differential microstrip lines due to bend discontinuities on one side and trace asymmetry on the other side. With the help of equivalent modal circuits, a theoretical basis is provided for the idea to compensate the undesired common mode (CM), due to the presence of the bend, by intentionally designing asymmetric traces. As an application example, the proposed CM-reduction strategy is used in conjunction with another recently-presented wideband CM suppression filter for differential microstrip lines. It is shown that the proposed solution enhances the overall CM-reduction performance of the filter by some decibels, while preserving its transmission properties.

In this article, a novel procedure for the frequency-domain solution of nonuniform transmission lines (NUTLs) is presented. The procedure is based on a recently proposed perturbative technique, which is proven to be computationally more efficient than standard solution approaches, which are based on line subdivision into uniform cascaded sections. With respect to the original perturbation technique, the procedure proposed here offers more flexibility, as it provides a representation of the NUTL under analysis in terms of S and/or T parameters at its ports. Moreover, it retains the same prediction accuracy at the price of a slight increase in computational burden, which can be mitigated anyway through parallel computing. Furthermore, even without ad hoc (parallel) implementations, the proposed procedure outperforms other approaches to solve differential lines with partially or fully repetitive geometries. Namely, it assures accurate prediction of output quantities with reduced simulation time. This is proven by three application examples, namely, two differential trapezoidal tabbed lines (one with interdigital tabs and one with facing tabs), and a differential microstrip line with a varying common-mode (CM) impedance (as such reducing CM noise). Comparison with full-wave simulations allows assessing the prediction accuracy of the proposed procedure. Comparison with the aforementioned transmission-line-based solutions allows appreciating the enhanced computational efficiency.

In this paper, design and implementation of a 4.25Gb/s optical fiber transceiver for Gigabit Ethernet (GbE) applications based on IEEE802.3z standard using Multi Mode Fiber (MMF) is described. Transmitter consists of an 850 nm Vertical-Cavity Surface-Emitting Laser (VCSEL), laser driver and transmission lines and receiver consists of a PIN photodiode, amplifiers and transmission lines. Differential microstrip lines and single-ended Conductor Backed Coplanar Waveguides (CBCPWs) on a FR-4 Printed Circuit Board (PCB) are implemented. To evaluate the performance of the implemented optical transceiver, as the results, the measured eye diagrams and Bit Error Rate (BER) measurements at the transmitter and receiver outputs are presented.

Common-mode (CM) noise on differential microstrip lines can be suppressed by PCB-embedded filters. These filters use resonating or broadband structures such that only the field from the CM signal couples to them. Based on a quarter-wavelength resonator, a new PCB filter is designed having an electrical size of only 0.15 λ × 0.065 λ, where λ is the effective wavelength in the CM filter. Its interdigital structure is also capable of suppressing higher order harmonics of the CM signal and can be used for USB 3.0 to mitigate electromagnetic interference. Further, a novel broadband suppression structure is described that uses magnetically lossy material to suppress the CM signal from 4.6 to 20 GHz without strongly affecting the intended differential signal.

Empty substrate integrated waveguide (ESIW) is a hollow SIW with its inner dielectric removed to achieve a reduced insertion loss. One of the drawbacks is the top and bottom covers need to be soldered to the middle substrate. Gap waveguide (GW) technology solves the contact issue utilising contactless electromagnetic band‐gap (EBG) structures. Therefore, empty substrate integrated GW (ESIGW) is a transmission line having both advantages of ESIW and GW. In this Letter, a wideband transition from rectangular waveguide (RW) to ESIGW is presented. RW is firstly matched to reduced‐height RW using E ‐plane stepped waveguides. Then, a short substrate integrated GW (SIGW) section is introduced between the reduced‐height RW and the ESIGW. This section not only serves as an impedance matching component, it also connects the two sides of the ESIGW and maintains the integrity of the substrate. To broaden the bandwidth of the transition, a triangular dielectric is added at the end of the ESIGW. A Ka‐band back‐to‐back prototype of the transition is designed and fabricated. In addition, TRL calibration is used to measure the transmission performance of the ESIGW. The measured results show that the transition works well over the entire Ka‐band.

Monopole antennas are widely used in communication systems because of features such as pure vertical polarization and omnidirectional radiation patterns in the horizontal plane. Conventionally, monopole antennas are fed through a ground plane by a coaxial probe. Recently, monopole antennas fed by printed transmission lines have attracted increasing attention. However, to the best of our knowledge, monopole antennas are seldom fed by a rectangular waveguide. We consider the problem of this type of feed because of our interest in designing an omnidirectional antenna at millimeter wave bands. At millimeter wave frequencies, rectangular waveguides are preferred to coaxial or microstrip lines because they exhibit very low loss, have a large power handling capacity and other waveguide components are readily available. The paper presents a design for monopole antennas fed by a rectangular waveguide. In order to achieve a good transition from a rectangular waveguide to the monopole antenna, a ridged waveguide section is introduced, and the vertical monopole is attached to the ridge through a circular aperture opened on the upper broad-wall of the rectangular waveguide, which is part of the ground plane. Two examples are provided and experimental tests of one of these antennas shows that the monopole can achieve about 24% bandwidth and 5 dBi gain.

In this paper, we are introducing a new category of wafer-level micromachined rectangular waveguide devices and illustrate a new transition of these devices to Coplanar Waveguide (CPW) lines for millimeter-wave applications. The 3-D fabrication process used in this paper utilizes a combination of thin film and thick film processes and produces a simple three-mask fabrication process. As a result, all the on-wafer elements such as the waveguide, the CPW lines, and their transition are simultaneously fabricated, which eliminates the ever-existing requirement of hybrid assembly of the waveguide parts. A metalized post is employed to couple the signal from the CPW line to the waveguide. Unlike the previous designs that are mostly based on capacitive coupling, the proposed CPW to waveguide transition is based on inductive coupling, which simplifies the fabrication requirements and improves the performance. Here, the entire back-to-back structure is designed, fabricated, and measured on a 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> wafer area. A wide-band RF performance is measured for the proposed waveguide structure. Our measured results show an insertion loss of as low as 1 dB at 72 GHz range. The proposed technique to realize wafer-level waveguides has great potential to include a variety of waveguide topologies including bends and arcs. Besides, this method allows for further expansion of the topic to integrate MEMS components inside the waveguide.

The concept of transmission zero resonator pair (TZRP) is used in this paper. Based on this TZRP, a new method to induce a passband is demonstrated, by which different types of bandpass filters can be designed. The proposed TZRP is structured by a pair of resonators with different resonant frequencies, which lead not only to two transmission zeroes, but also to a transmission pole between them. Passband filters can then be built by designing the proximity coupling between the TZRPs, as the TZRP works as a basic resonant element. The passband of these filters can be flexibly controlled by the resonators of TZRPs, which determine the locations of the transmission zeroes and poles. By carefully allocating the transmission zeroes, high selectivity and large out-of-band rejection can be realized. This design method is applied to design filters in two different transmission media, namely, microstrip line and rectangular waveguide. Simulated and measured results demonstrate the effectiveness of this new approach of bandpass filter design. The designed filters have the properties of small size, easy fabrication, low cost, and low loss.

This paper presents a 3.5 GHz reflective liquid crystal (LC) phase shifter based on a differential microstrip line periodically loaded with floating electrodes. By creating a virtual ground between differential lines, the design eliminates the need for metal grounding, allowing fabrication on glass substrates using LCD-compatible processes. The LC layer forms a tunable capacitor under AC bias, enabling continuous analog phase modulation. A prototype achieves a 282° phase shift, 300 MHz bandwidth, and low-voltage operation below 15 V. The one-port reflective design utilizes round-trip enhancement to double the effective phase shift, achieving compact size and low return loss. This structure is highly suitable for scalable, transparent, and low-cost reconfigurable intelligent surface (RIS) implementations in mid-band 5G and future 6G systems.

The C-band adapter for matching standard coaxial line and rectangular waveguide with reduced height is simulated numerically. The proposed design of this adapter provides high power transmission what can be useful in some applications. Numerical modeling shows that developed adapter exhibits a voltage standing wave ratio less than 1,2 with an insertion loss of 0,1 dB in the frequency range from 4,5 GHz to 7,5 GHz.

The transition between coaxial line and rectangular waveguide has been extensively studied in the past. The probe antenna usually a cylinder, is the extension of the inner conductor of the coaxial line into the waveguide normal to the H-plane. Several models for the probe geometry and current distribution are considered, both for open- and short-circuited antennas. In the case of shorted antenna, a two-stage analysis is employed. In the first stage, the coaxial line is matched to the reduced-size waveguide followed by the second stage which involves the design of an impedance transformer. The mode matching method is used to solve this part of the problem, which helps obtain more accurate results than those obtained by classical approximate methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>