Soumava Mukherjee

In this letter, the design and implementation of a single-balanced mixer are presented at 24–32 GHz. The size of the proposed mixer is $3.6\lambda _{g}\times 3.4\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at the center frequency. The single-balanced mixer is realized by using a configuration of a substrate-integrated coaxial line (SICL)-based rat-race hybrid ring with five ports and two MA4E1317 GaAs Schottky diodes. The IF extraction circuit is introduced at the fifth port of the rat-race hybrid ring with passband from dc to 8 GHz. The measured conversion loss (CL) is less than 13 dB from 24 to 32 GHz. The measured port isolations of local oscillator (LO)-radio frequency (RF), RF-intermediate frequency (IF), and LO-IF ports are greater than 24 dB.

This article presents the design and fabrication of self-packaged, self-shielded substrate integrated coaxial lines (SICL). The study introduces a closed-form equation for the characteristic impedance of SICL, emphasizing the effect of the outer conductor width and substrate thickness on this parameter. The robustness of the proposed formula is confirmed through testing of four distinct SICL transmission lines, each with varying dielectric constants and substrate thicknesses. A novel dual-band SICL transmission line is developed using short-circuited planar coaxial stubs, which serves as an alternative to the conventional quarter-wavelength transmission line design. The performance of this dual-band line is analyzed across different characteristic impedances, and the range of achievable frequency ratios is determined analytically. The resulting SICL-based rat-race coupler, fabricated using standard PCB processes, demonstrates a measured fractional bandwidth of 26.69% at 10.83 GHz and 11.29% at 22.94 GHz. It achieves low amplitude and phase imbalances, with values of $\pm$1 dB and less than $\pm$4°, respectively. Owing to the filtering response provided by short circuited coaxial stubs, the third harmonic of proposed coupler is suppressed and spurious rejection better than 22 dB is achieved up to 40 GHz.

This article proposes a new design procedure for the development of a highly selective diplexer and its integration with a high-gain antenna. The proposed diplexer conceived by two SICL-based bandpass filters and an impedance matching network exhibits low insertion loss and excellent out-of-band rejection. The proposed SICL-based diplexer exhibits high selectivity, and multiple transmission zeros which aid in achieving steep rejection skirt as well as excellent out-of-band rejection. The self-shielded structure and multiple transmission zeros outside the band of operation provides a high measured isolation greater than 48 dB at both transmit and receive bands of the proposed diplexer, while maintaining a low profile and planar form factor. Additionally, a design for a SICL-based T-junction power divider with suitable electrical lengths and characteristic impedance selection is presented for two output sections operating at different frequency bands. A wideband high gain linearly tapered antipodal antenna is realized for a frequency range of 11 to 18 GHz. The SICL diplexer-antenna integrated system has a peak gain of 13.8 dBi at 11.21 GHz and 13.15 dBi at 13.85 GHz.

This letter describes a compact, co-designed 16-port MIMO antenna that operates in both sub-6 GHz and millimeter-wave (mmWave) frequency bands. In the sub-6 GHz range, it features eight interconnected modified octagonal eighth-mode substrate integrated waveguide (SIW) cavities. The TM010 mode is excited through a U-shape slot inserted on the top surface of SIW cavities. For the mmWave range, eight rectangular quarter-mode SIW cavities are excited at TE330 mode. They are strategically positioned to create a compact footprint, forming two 8×8 MIMO antenna structures. It achieves a measured bandwidth of 30 MHz with a peak gain of 2.29 dBi at the resonance frequency of 3.5 GHz and a bandwidth of 2.48 GHz with a peak gain of 6.73 dBi at 26 GHz. The isolation among the different feeding ports is below 16.3 dB, while the ECC between various radiated fields is less than 0.14. Key advantages of this proposed MIMO antenna are inter-band spatial carrier aggregation (CA), low antenna density, and easy tunability across various NR frequency ranges. An example of four 4×4 MIMO antennas enabling intra-band spatial CA is also investigated. These performances make it suitable for 5G indoor small-cell base stations in densely populated urban environments.

A digitally controlled beam steerable printed dipole antenna operating in ISM band has been proposed using PIN diodes switching mechanism. The proposed antenna provides effective solution of beam steering by establishing adequate coverage in elevation plane using a single dipole element. The beam steering of antenna has been digitally controlled by varying the effective length of one dipole arm by switching the PIN diodes integrated on it. For effective digitally controlled beam steering, the DC biasing voltage applied for switching PIN diodes is regulated by Pulse Width Modulation (PWM) signal generated from STM32F407VG microcontroller through RC filter. Biasing elements for antenna is intentionally placed on back side of substrate through via to minimize the effect on radiation pattern. Peak gain of proposed antenna is measured as 4.57 dB with cross polarisation below −20 dB and scan loss less than 0.8 dB. The proposed antenna is capable of steering beam up to 45 degrees in elevation plane having 120 MHz operational bandwidth. In order to establish wide range of applications, proposed antenna is designed and tested for 2.45 GHz ISM band. The proposed antenna operates with minimal design complexity, high portability, reduced manufacturing cost, easily integrated architecture, lower parasitic losses and less space constraints due to single dipole structure with microcontroller switched PIN diodes integrated on antenna itself.

This letter presents substrate integrated coaxial line technology (SICL)-based low phase noise (PN) reflection oscillator at 15 GHz. The proposed oscillator circuit is realized using SICL-based high- $Q$ -factor resonator. The SICL resonator operates at 15 GHz, where the terminating impedance of the resonator is controlled by the appropriate selection of inset dimensions. Moreover, the proposed circuit satisfies the Kurokawa’s condition between the SICL resonator and the source terminal of active device with adjusting the length of short-circuited stub at the gate terminal in the SICL environment. Due to the high- $Q$ factor of the SICL-based resonator, the prototype of the proposed oscillator achieved a low PN of $-$ 110 dBc/Hz at 100 kHz and $-$ 133 dBc/Hz at 1 MHz with an RF output power of 12 dBm.

This research study introduces a Multiple-Input Multiple-Output (MIMO) antenna array for simultaneous operation in 5G FR2 millimeter wave and 6G mid-band frequencies. At 10 GHz, a Substrate Integrated Waveguide (SIW) cavity backed slot antenna (CBSA) is designed to radiate in broadside direction with a gain of 6.3 dBi. A rhombus-shaped slot is engraved on the top layer of the cavity and its position is tuned to obtain a bandwidth of 750 MHz to satisfy the forthcoming 6G mid-band. At 28 GHz, a Substrate Integrated Coaxial Line (SICL) fed novel ±45◦ inclined crossed dipole antenna exhibiting a gain of 6 dBi is designed. An impedance matching network is designed in the middle layer to achieve a bandwidth of 3.5 GHz, enabling support for the entire n261 and n257 bands of the FR2 millimeter wave frequency. In order to have simultaneous operation at 10 GHz and 28 GHz, a novel SICL transmission line based feed section is proposed. In the lower band (10 GHz), one arm of the feed section feeding the crossed dipole behaves as an open-circuited line, facilitating wave propagation exclusively in the lower band CBSA. Similar effect is obtained in the other arm for operation in the upper band (28 GHz). This technique helps in attaining simultaneous 5G/6G performance while having negligible effect at the other operating frequency.