A novel frequency-tunable branch line coupler

Abstract

This article introduces a novel two-section frequency-tunable branch line coupler, which is realized by inserting a narrow band frequency-tunable phase inverter into a wideband two-section branch line coupler's middle branch line. Such frequencytunable method is different from the conventional one. Furthermore, in this bias feeding design, there are only one control voltage, two varactors, two resistors, and two capacitors are utilized. The measured results show that the operation frequency of the branch line coupler can be tuned from 0.73 to 1.33 GHz, and the return loss is >20 dB, the isolation >20 dB, the amplitude imbalances <1 dB, and the phase imbalances is <28. Through the comparison, the measured results basically conform to the simulated results in this design. K E Y W O R D Sbranch line coupler, frequency-tunable, phase inverter, resonant frequency

Microstrip phase inverters with different harmonic waves

“…The main applications for the proposed phase inverter can be concluded as follows: Some harmonic waves of the ring coupler which use the proposed phase inverter can be suppressed directly. The structures of the reconfigurable phase inverters can be simplified based on the proposed theory, only one of the shorted lines need to be changed to a reconfigurable resonator. …”

“…2. The structures of the reconfigurable phase inverters 3,4 can be simplified based on the proposed theory, only one of the shorted lines need to be changed to a reconfigurable resonator.…”

“…In recent years, novel phase inverters with reconfigurable functions have been reported in Refs. and . Phase inverters can be realized utilizing parallel‐strip transmission line, coplanar waveguide, coplanar strip, substrate integrated waveguide and microstrip with defected ground structure …”

A phase tunable hybrid coupler with enhanced bandwidth

“…Among the components, the hybrid coupler is considered to be one of the most important ones, as it provides the signals with desired amplitude and phase characteristics for the next module. To support different wireless communication standards, several approaches to achieve the tunability in operating frequency have been proposed in References . Besides, the tunability in coupling coefficient was also reported .…”