Traveling-wave Switch Research Articles

Time-domain Analysis of Traveling Wave Switches based on Time-variant Transmission Line Model

Background and Objectives: Switches play an important role in controlling the signal flow in telecommunication systems. The traveling wave switch structure is introduced based on active transmission lines. By applying the gate voltage (Vg), the transfer of signal through the drain transmission line is controlled. By increasing operating frequency, lumped model is unreliable and semi and fully distributed modeling should be applied for the analysis of these elements. Methods: Traveling wave switches can be analyzed based on the lossy transmission line model, in linear and non-linear modes in the time and frequency domains. The study of transient behavior and time domain response of switch is very important. Switching and transient from on to off state and vice versa affect the performance of telecommunication systems.In the proposed method, the switch is modeled as the lossy transmission line that the primary elements of this model change with time based on the control voltage applied to the gate and are considered as variable with time. The structure is discretized in the space and time domains with ∆z and ∆t steps. The Finite-difference time-domain (FDTD) method is utilized to study the transient response of switches. By using the leap-frog algorithm, the new voltages and currents of the transmission line are calculated based on the values of adjacent spatial and temporal steps.Results: The transient response of the switch is analyzed in transition from off to on states and vice versa, for the 800µm switch at 60GHz, based on the parameters of the passive transmission line and nonlinear Curtice2 FET model.Conclusion: For transient analysis of the structure, the time-variant lossy transmission line model was used that its elements changed based on the applied control voltage. The results of FDTD method were investigated with the transient analysis of commercial software that show good agreement with each other and validated the proposed method.

A compact low insertion loss Ka‐band GaAs MMIC traveling wave switch with absorptive characteristic

AbstractIn this articel, a compact single‐pole double‐throw traveling wave switch is proposed and fabricated using 0.15 μm‐pHEMT GaAs technology. The switch obtained an insertion loss less than 2 dB, and the isolation is better than 28 dB in the core passband. The excellent return losses performances at all the ports are good obtained especially for the isolation port from 30 to 40 GHz. The return losses of isolated port is better than around 5 dB. To demonstrate the design conception, a prototype of the proposed switch is fabricated with a size of 0.97 × 0.77 mm2 including all the pads. There is a good agreement between the simulated and measured results. To the best of our knowledge, this is the neoteric GaAs MMIC traveling‐wave switch topology with the good absorptive characteristic.

A 5-Bit X-Band GaN HEMT-Based Phase Shifter

In this study, we propose a 5-bit X-band gallium nitride (GaN) high electron mobility transistor (HEMT)-based phased shifter monolithic microwave integrated circuit for a phased-array technique. The design includes high-pass/low-pass networks for the 180° phase bit, two high-pass/bandpass networks separated for the 45° and 90° phase bits, and two transmission lines based on traveling wave switch and capacitive load networks that are separated for the 11.25° and 22.5° phase bits. The state-to-state variation in the insertion loss is 11.8 ± 3.45 dB, and an input/output return loss of less than 8 dB was obtained in a frequency range of 8–12 GHz. Moreover, the phase shifter achieved a low root mean square (RMS) phase error and RMS amplitude error of 6.23° and 1.15 dB, respectively, under the same frequency range. The measured input-referred P1dB of the five primary phase shift states were larger than 29 dBm at 8 GHz. The RMS phase error and RMS amplitude error slightly increased when the temperature increased from 25 to 100 °C. The on-chip phase shifter exhibited no dc power consumption and occupied an area of 2 × 3 mm2.

A $Ka$ -Band GaAs MMIC Traveling-Wave Switch With Absorptive Characteristic

A 36–38-GHz monolithic microwave integrated circuit (MMIC) single-pole double-throw (SPDT) switch employing a traveling-wave concept with absorptive characteristic is presented. The switch uses absorptive sections for better impedance matching in all ports. The switch obtained good linearity with the insertion loss of 3.2 dB, more than 28-dB isolation, and the return losses at all the ports are larger than 8.1 dB within the bandwidth of interest (36–38 GHz). The switch was fabricated by using GaAs 0.15- $\mu \text{m}$ process. The chip area is very compact, just about 1 mm $\times \,\, 1.1$ mm, including all the pads. To our best knowledge, this is the first GaAs MMIC traveling-wave switch type that has the absorptive characteristic.

75–110-GHz $W$ -band High-Linearity Traveling-Wave T/R Switch by Using Negative Gate/Body-Biasing in 90-nm CMOS

In this letter, a 75-110-GHz W-band high-linearity traveling-wave single-pole-double-throw switch in 90-nm CMOS GUTM 1P9M is presented. Compared with the traditional traveling-wave switch with negative body-biasing technique, the proposed design applies the negative biasing to the gate terminals simultaneously. Therefore, the third-order intermodulation product is significantly reduced. The measured results show that the insertion loss is less than 3.4 dB, return loss is better than 10 dB, and Tx-to-Rx isolation is higher than 40 dB, respectively. For the linearity of the switch, the measured IP1dB is higher than 15 dBm and IIP3 is 37.1 dBm at 94 GHz, respectively. The proposed switch presents good performance of insertion loss, isolation, IP1dB, and IIP3, among the compared millimeter-wave CMOS switches.

A Low Loss High Isolation DC-60 GHz SPDT Traveling-Wave Switch With a Body Bias Technique in 90 nm CMOS Process

In this letter, a low loss high isolation broadband single-port double-throw (SPDT) traveling-wave switch using 90 nm CMOS technology is presented. A body bias technique is utilized to enhance the circuit performance of the switch, especially for the operation frequency above 30 GHz. The parasitic capacitance between the drain and source of the NMOS transistor can be further reduced using the negative body bias technique. Moreover, the insertion loss, the input 1 dB compression point (P1 dB)> and the third-order intermodulation (IMD3) of the switch are all improved. With the technique, the switch demonstrates an insertion loss of 3 dB and an isolation of better than 48 dB from dc to 60 GHz. The chip size of the proposed switch is 0.68 × 0.87 mm2 with a core area of only 0.32 × 0.21 mm2.

A 55–64 GHz Fully-Integrated Sub-Harmonic Wideband Transceiver in 130 nm CMOS Process

In this letter, a 55-64 GHz compact fully-integrated gigabit transceiver with sub-harmonic pump technique is presented. The transceiver consists of a single-pole-double-throw (SPDT) traveling wave switch, a low-noise amplifier (LNA), a buffer amplifier (BA), and two sub-harmonic resistive mixers for up-conversion and down-conversion, respectively. The transceiver using 130 nm standard CMOS technology achieves an up-conversion gain of 7.4 dB at 62 GHz and down-conversion gain of 7.2 dB at 60 GHz with a compact chip size of 1.2 mm2. The 3 dB frequency bandwidth ranges from 55 to 64 GHz, which can cover the whole frequency band for 802.15.TG3C WPAN applications. For system applications, gigabit BPSK modulation signal test is successfully performed in this work.

Broadband InGaAs PIN Traveling-Wave Switch Using a BCB-Based Thin-Film Microstrip Line Structure

This letter describes the design and fabrication of a broadband InGaAs PIN traveling wave switch. A new thin-film microstrip line structure integrated with InGaAs PIN diodes has been used to enhance the switch performance at higher frequencies. The developed InGaAs PIN switch has an insertion loss of less than 3.2 dB and an isolation of greater than 40 dB in a broadband frequency range from 25 to 95 GHz. The BCB-based multi-layer technology effectively reduces the chip size of the fabricated SPDT MMIC switch to 1.05 times 0.58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . To our knowledge, this is the first InGaAs PIN traveling-wave switch demonstrated up to 95 GHz.

Design Considerations for Traveling-Wave Single-Pole Multithrow MMIC Switch Using Fully Distributed FET

The circuit design considerations for the traveling-wave switch (TWSW) single-pole double-throw (SPDT) monolithic microwave integrated circuit (MMIC) utilizing a fully distributed FET (FD-FET) are presented here for the first time. The normalized length of the impedance transformer for a single-pole multithrow TWSW using the FD-FET is found to be less than a quarter-wavelength at the operating frequency. Unlike the TWSW using lumped FETs, the TWSW with the FD-FET offers the advantage of no design limits regarding such frequency characteristics as bandwidth and group delay. The newly developed SPDT TWSW MMIC using the 400-mum-gate finger FD-FET delivers broadband characteristics over more than an octave frequency range with highly reliable MMIC technology. The newly developed SPDT MMIC switch provides low insertion loss of less than 2.1 dB and high isolation of over 25.5 dB from 38 to 80 GHz, coupled with the benefit of very small size

FET-integrated CPW and the application in filter synthesis design method on traveling-wave switch above 100 GHz

A new transmission-line concept, called the field-effect transistor (FET)-integrated coplanar waveguide (CPW), is proposed. This concept treats the passive two-finger FET as CPW and, thus, the scaling rule is more accurate than the previous model, especially in high frequency. The extraction approach of the parameters of the FET-integrated CPW is also included. With this concept, the design procedure of traveling-wave switches can be equivalent to a filter synthesis problem. Based on this design procedure, a single-pole single-throw and a single-pole double-throw traveling-wave switch have been realized and measured using 0.15-/spl mu/m high-linearity AlGaAs/InGaAs/GaAs pseudomorphic high electron-mobility transistors. Finally, the frequency limitation of the traveling-wave switches is also discussed. The results show the FET-integrated CPW is the most efficient way to overcome the frequency limitations of traveling-wave switches, achieving operation frequency to 135 GHz, the highest frequency reported to date.

DC-110-GHz MMIC traveling-wave switch

This paper presents the broadest band monolithic-microwave integrated-circuit traveling-wave switch ever reported for millimeter-wave applications. The developed switch with the novel structure of a 400-/spl mu/m-gate finger field-effect transistor (FET) indicated an insertion loss of less than 2.55 dB and an isolation of better than 22.2 dB from dc to 110 GHz. Also, the switch indicated no degradation of insertion loss and an ON/OFF ratio of more than 22.7 dB up to an input power of 26.5 dBm at 40 GHz. Circuit analytical results based on a lossy transmission-line model for small-signal performance and circuit simulation results using the two-terminal nonlinear FET model for large-signal operation successfully showed good agreement with the experimental results.

Continuous-wave CO2laser with acoustoopticQswitching

An experimental investigation was made of low-frequency switching of the Q factor of cw sealed conventional and waveguide lasers. The use of an intracavity acoustooptic traveling-wave switch made it possible to generate microsecond pulses with repetition frequencies up to 200 kHz.