A bandpass filter with reconfigurable band traps operating in the S-band with a wide tuning range for the transmission zeros is presented in this article. The filter employs a main transmission line path comprising two different step impedance resonator structure, with stopband formation achieved through four quarter-wavelength resonators coupled to both ends of the main path. These resonators folded into open-ring to decrease the area of the circuit, are loaded with reconfigurable elements (SMV2020), controlled via a voltage-based control system. The voltage control system, which is designed by microcontroller unit (MCU)-AT32F421K8T7, can change the power supply voltage linearly to make this filter system flexible. The filter is fabricated on a Rogers 4350 substrate with a relative dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.762 mm and simulated in high-frequency structure simulator. The filter demonstrates favorable passband characteristics on either side of the stopband, achieving an in-band insertion loss of less than 1 dB and a return loss exceeding 12 dB. The reconfigurable stopband spans from 2.1 to 3.0 GHz, with a stopband return loss greater than 13 dB and an out-of-band rejection exceeding 50 dB.

An active receiving antenna for Radio Navigation and Radio Positioning applications in S-band frequency is designed and fabricated. In this active antenna, the amplifier is integrated with the radiator which is a rectangular patch antenna. This patch antenna is analyzed with full-wave momentum method. With the developed design routine, ultra-low noise active receiving antenna can be realized. The ADS software and its full-wave Momentum is used for simulation. The experimental results show good agreement with the simulation results.

This paper presents a design method of internally-matched packaged GaN high electron mobility transistors (HEMTs) for achieving not only high-efficiency and high-power performances but also a wide bandwidth and insensitivity to harmonic terminations in the S-band. The package and its internal matching networks are synthesized to confine the second harmonic impedances seen by the GaN die to high-efficiency regions whatever the harmonic impedances presented outside the package. This paper reports the design of a packaged GaN HEMT achieving 78% of power-added-efficiency (PAE) and 25 W of output power at 2.5 GHz. A packaged GaN power bar is also reported with the addition of fundamental matching networks inside the package. In 50 Ω environment, the packaged GaN power bar provided more than 56% of PAE from 2.5 to 3.1 GHz and was desensitized to harmonic load variations with less than two points of PAE variation when a load-pull is performed at second harmonic frequencies outside the package.