Abstract
This paper presents the analysis, design, and characterization of a wideband 90° phase switch in Ka-band. The phase switch is based on two microstrip bandpass filters in which the commutation is performed by a novel single-pole double-throw (SPDT) switch. The analysis of π-network bandpass filters is provided, obtaining the phase difference and amplitude imbalance between filters and their scattering parameters; tested results show an average phase difference of 88.9° ± 5° and an amplitude imbalance of 0.15 dB from 24 to 37 GHz. The new broadband SPDT switch is based on a coplanar waveguide-to-slotline-to-microstrip structure, which enables a full planar integration with shifting branches. PIN diodes are used to perform the switching between outputs. The SPDT shows isolation better than 19 dB, insertion loss of around 1.8 dB, and return loss better than 15 dB. The full integration of the phase switch achieves a return loss better than 11 dB and insertion loss of around 4 dB over the band 26-36 GHz, with an average phase difference of 87.1° ± 4° and an average amplitude imbalance of 0.3 dB. It provides an excellent performance for this frequency range, suitable for radio-astronomy receivers.
Highlights
Phase switches are two-port networks providing a fixed phase difference with low-amplitude imbalance between two states in a defined bandwidth.1 As an initial design approach, a phase switch is based on a phase shifter, which is a four-port passive network, introducing a constant phase difference
A = S21S, B = S22S · i1, C = S32S · i2, D = S31S, E = S32S · i1, and F = S33S · i2. Both transmission parameters for each circuit state are obtained, which enable the errors in phase difference and amplitude imbalance to be calculated by subtracting the calculated phase difference and amplitude imbalance of the phase switch to the values of the ideal bandpass filter (BPF) (AI and ), shown in EAI = 10 · log 10|S21BPF #1_C/S21BPF #2_C|2 − AI, (20)
The proposed configuration uses broadband single-pole double-throw (SPDT) on planar technology integrated with wideband phase shifting branches based on BPF designs
Summary
Phase switches are two-port networks providing a fixed phase difference with low-amplitude imbalance between two states in a defined bandwidth. As an initial design approach, a phase switch is based on a phase shifter, which is a four-port passive network, introducing a constant phase difference. As an initial design approach, a phase switch is based on a phase shifter, which is a four-port passive network, introducing a constant phase difference. The design of wideband phase shifters has been widely described in the literature using quite different topologies.. Other approaches use modified configurations instead of the transmission line, synthesizing coupled section, or bandpass filter (BPF) topologies as reference circuits. This paper presents the analysis, design, and characterization of a 90◦ phase switch based on BPF combination as shifting branches.
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