Active Quasi-circulator Research Articles

Design of a Broadband and High-Isolation CMOS Active Quasi-Circulator

Using industry standard TSMC 90 nm CMOS technology, a broadband and high-isolation active quasi-circulator MMIC was fabricated to meet the needs of future communication system integration. An active balun and phase inverter stage made of a common-source (CS) field-effect transistor (FET) comprised the quasi-circulator that was suggested. A cascade CS stage was used to produce the active balun, which increased the isolation of |S12| and |S23| through the unilateral characteristic of the FET and allowed for transmission of |S21| and |S32|. Further, a CS FET connected in parallel to ports 1 and 3 for phase cancellation can effectively increase the quasi-circulator’s isolation |S31|. Theoretical analysis for the detailed circuit was shown in the main paper. The results show that all isolations are better than 20 dB over 5–33 GHz, and the measured findings reveal that the suggested quasi-circulator has an insertion loss of less than 10 dB. It is possible to reach an isolation level of 55 dB between ports 1 and 3, which is greater than present research.

Active quasi circulator: Comprehensive review and performance comparison

AbstractDesigning circulator as an antenna interface device becomes a daunting task, particularly active‐quasi circulator. This article focuses on demonstrating the basic operation principle, design methods, technical parameters, and performance metrics of active quasi‐circulator. In addition, the study provides an analogy of the circuits and structures proposed by the researchers to enhance certain performance metrics. Active signal cancellation and passive signal cancellation are identified as the major design approaches. Tunable, wideband, and wideband‐tunable are the major types of circulators found in existing literature. Moreover, this article provides a performance comparison of the active‐quasi circulators available in existing literature. Several active quasi‐circulators were able to operate in high frequencies such as 60 GHz with acceptable isolation levels. On the other hand, several designs have over 30 dB isolation, which is a highly desired parameter. At last, the future design challenges associated with active‐quasi circulators have been discussed to provide insight into future research.

A Wideband Active Quasi-Circulator With 34-dB Isolation and Insertion Loss of 2.5 dB

Based on the dual-path cancellation methodology, a noise cancellation technique and an insertion loss (IL) mitigation technique are presented to improve the properties of the active quasi-circulators. The proposed circulator is fabricated with a standard 0.18-μm CMOS process, occupying an area of 0.91 mm × 0.49 mm including the pads. The measurement results show that 34-dB isolation is obtained over a wide frequency range from 1 to 8 GHz, while the IL is below 2.5 dB and the noise figure (NF) is less than 10 dB.

2.2–4.6-GHz Active Quasi-Circulator with > 24-dB Transmit–Receive Isolation

An active quasi-circulator (AQC) integrated circuit is designed and fabricated in a 0.18-[Formula: see text]m CMOS process. The proposed design is based on a parallel combination of a common-source (CS) stage and a combined common-drain (CD) and common-gate (CG) topology. Scattering matrix of the core AQC circuit is derived considering MOSFET’s secondary effects, particularly the body effect as well as output loading effects. Measurements of the quasi-circulator reveal an insertion loss of [Formula: see text] dB between transmitter-to-antenna ports ([Formula: see text]) and of [Formula: see text] dB between antenna-to-receiver ports ([Formula: see text]), within a frequency band of 2.2–4.6 GHz. The isolation between the transmitter and the receiver ports ([Formula: see text]) is better than 24 dB with a maximum value of 29.5[Formula: see text]dB @ 3.6[Formula: see text]GHz. The power dissipation of the proposed AQC is 40[Formula: see text]mW and it covers an active chip area of 0.677[Formula: see text]mm2.

A Dual Interference-Canceling Active Quasi-Circulator Achieving 36-dB Isolation Over 6-GHz Bandwidth

Circulator is a key component in full-duplex wireless and radar detection systems. In this letter, a dual interference-canceling active quasi-circulator is proposed to enhance the isolation capability over the range of 1–7 GHz. The circulator is fabricated in the standard 0.18- $\mu \text{m}$ CMOS process occupying 1.03 mm $\times0.55$ mm including the pads. Measurement results demonstrate more than 36-dB isolation from the Tx to the Rx within 6-GHz bandwidth. The designed circulator is a good candidate for duplexers to allow the integrated transmitter and receiver to share a single antenna in the certain short-range wideband wireless communication systems, where noise figure (NF) is not strictly demanded but low cost and high integration are urgently required.

A Tunable 5–7 GHz Distributed Active Quasi-Circulator With 18-dBm Output Power in CMOS SOI

Circulators and quasi-circulators (QCs) have a tradeoff between maximum isolation and bandwidth. We present a tunable distributed active circuit to achieve high isolation over a wide frequency range. The reported QC provides more than 40-dB suppression between transmit (TX) output signal at the antenna and TX leakage into the receive (RX) port over a tuning range of 5.3–7.3 GHz in small-signal operation. Large-signal TX-RX suppression is optimized across power level. The TX output achieves peak power of 18 dBm and 12% power-added efficiency at 6.3 GHz. The QC is designed in a high-resistivity 45-nm CMOS silicon-on-insulator process and occupies an area of $1.62~ \text {mm} \times 0.97~ \text {mm}$ .

Fully Integrated 10-GHz Active Circulator and Quasi-Circulator Using Bridged-T Networks in Standard CMOS

A three-port active circulator and an active quasi-circulator (QC) based on bridged-T networks (BTNs) are designed and fabricated in a standard 0.18- $\mu \text{m}$ CMOS technology. The BTN provides a notch frequency response, and therefore, the circulator is practical by connecting three BTNs in a ring-type configuration. With a power consumption of 18.2 mW, the circulator achieves $6.1\sim 8$ -dB insertion loss, better than 25-dB isolation and 18.3-dB transmission ratio from 8.4 to 11.1 GHz. Furthermore, the QC based on one BTN topology can also be obtained by adding an external amplifier. With a power consumption of 18.6 mW, it achieves 7/−2-dB forward transmission gain, better than 17.3-dB isolation, and better than 15.3-dB transmission ratio at 9.9 GHz. The presented designs feature excellent performances in high isolation and transmission ratio compared with other CMOS active circulators or QCs. To the best of our knowledge, the designs are the first demonstration of three-port circulator/QC designs based on the BTN topology, and the design concept is also applicable to an $n$ -port circulator design.

A Broadband Active Quasi Circulator for UHF and L Band Applications

This letter presents a compact, broadband three-port MMIC-based quasi circulator for UHF and L bands. As a motivation and application, the use of this circuit in a network analyzer is presented. The circuit is designed using differential amplifier and lossy broadband combiner to obtain effective phase cancellation for high directivity. The designed quasi circulator has return losses at all ports better than 10 dB and reverse isolation above 30 dB in the frequency range from 0.2 to 2.5 GHz. The quasi circulator has directivity of 15 to 52 dB and load dynamic range of 10 to 49 dB, over the 0.2 to 1.7 GHz band. The proposed circuit thus can be used in portable network analyzers and other applications designed for the UHF and L bands.

An Active Quasi-Circulator for 77 GHz Automotive FMCW Radar Systems in SiGe Technology

One of the key functions of transmit and receive modules with a single antenna is the separation of the weak receive signal (RX) from the strong transmit signal (TX). In state-of-the-art FMCW radar MMICs, this function is usually implemented using passive devices, which have relatively large physical dimensions compared to the chip area and exhibit insertion losses. In this letter the design of an active quasi-circulator (QC) is presented with a special emphasis on TX/RX isolation. An analysis is presented to aid in the circuit design, so that the desired isolation requirements can be achieved. The implemented active QC is fabricated in a 200 GHz fT Silicon-Germanium (SiGe) HBT technology. On-wafer measurements show a TX/RX isolation of 16 dB over a bandwidth of 8 GHz. The measured insertion loss for the TX and the RX signal is less than 1 and 1.5 dB, respectively.

A 1.5-mW, 2.4 GHz Quasi-Circulator With High Transmitter-to-Receiver Isolation in CMOS Technology

A 2.4 GHz active quasi-circulator is implemented in TSMC 0.18 μ m CMOS technology. We propose a new architecture using current-reuse and adjustable signal cancellation to achieve a low-power, high-isolation and small-size circulator. The measured isolation from transmitter to receiver, |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> |, can be as high as 68 dB, which to our knowledge is the highest value ever reported in integrated circulators. Other isolations, such as receiver-to-transmitter, receiver-to-antenna, and antenna-to-transmitter isolations, are all better than 28 dB. The total power consumption is only 1.5 mW with a chip size of 820 μm × 750 μm including bypass capacitors and pads.

Wideband active quasi‐circulator with tunable isolation enhancement

An active quasi-circulator comprises three single-stage distributed amplifiers (DAs), in which two are for wideband transmission while the remaining one is for wideband signal cancellation. This quasi-circulator has wideband frequency operation and by optimising the bias current, tunable isolation enhancement between port 1 and port 3 is achieved. The experimental results show that this quasi-circulator has insertion losses of around 0 dB, return losses better than 10 dB at each port, minimum non-tunable isolation of around 15 dB from 0.8 to 2.2 GHz and tunable isolation of more than 40 dB between port 1 and port 3 from 0.8 to 2.2 GHz.

Active quasi-circulator with high port-to-port isolation and small area

An active quasi-circulator integrated circuit relying on a differential central core is presented. Measurements on the quasi-circulator reveal that the forward transmission coefficients, S 21 and S 32 , are both close to -4 dB in the range of 2.5 to 6 GHz. The isolation between the ports is greater than 20 dB and can reach up to 59-dB in the case of S 13 . The chip was fabricated on a standard 130 nm CMOS process and the core circuit area measures 0.105 mm 2 , making it the smallest active quasi-circulator known to date.

A 30 GHz Active Quasi-Circulator With Current-Reuse Technique in &lt;formula formulatype="inline"&gt; &lt;tex Notation="TeX"&gt;$0.18~\mu{\rm m}$&lt;/tex&gt;&lt;/formula&gt; CMOS Technology

An active quasi-circulator at 30 GHz is designed and fabricated in TSMC RF mixed signal CMOS technology. The current-reuse technique is integrated with a common-source stage to form the quasi-circulator core while reducing the power consumption at the same time. The transmitter-to-receiver leakage is alleviated by the out-of-phase cancellation of signals from two paths. The isolation and insertion loss between other pairs of ports are improved with buffer stages. All the measured isolations are higher than 12 dB, all the insertion losses are lower than 7.9 dB, and the total power consumption is 15 mW.

CMOS Active Quasi-Circulator With Dual Transmission Gains Incorporating Feedforward Technique at $K$-Band

This paper presents an innovative architecture for the active quasi-circulator to break the structural limitation on the leakage suppression. A practical prototype is implemented at K -band and fabricated by using standard 0.18- μm 1P6M CMOS technology. The comparisons between simulations and on-wafer measurements are reported in detail to confirm the feasibility and capability of the proposed active quasi-circulator. At 24 GHz, the prototype has dual transmission gains of 22.4 and 12.3 dB in the transmitting and receiving paths, respectively. The measured isolation, which is defined by the ratio of the forward transmission to reverse transmission coefficient in the same path, is higher than 50.0 dB at 24.0 GHz. By comparing the leakage phenomena between the prototype with and without feedforward cancellations, the leakage suppression can be improved with a maximum value of 44.7 dB at 23.63 GHz.

MMIC-Based Quadrature Hybrid Quasi-Circulators for Simultaneous Transmit and Receive

This paper presents a new type of monolithic microwave integrated circuit (MMIC)-based active quasi-circulator using phase cancellation and combination techniques for simultaneous transmit and receive (STAR) phased-array applications. The device consists of a passive core of three quadrature hybrids and active components to provide active quasi-circulation operation. The core of three quadrature hybrids can be implemented using Lange couplers. The device is capable of high isolation performance, high-frequency operation, broadband performance, and improvement of the noise figure (NF) at the receive port by suppressing transmit noise. For passive quasi-circulation operation, the device can achieve 35-dB isolation between the transmit and receive port with 2.6-GHz bandwidth (BW) and insertion loss of 4.5 dB at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band. For active quasi-operation, the device is shown to have 2.3-GHz BW of 30-dB isolation with 1.5-dB transmit-to-antenna gain and 4.7-dB antenna-to-receive insertion loss, while the NF at the receive port is approximately 5.5 dB. The device is capable of a power stress test up to 34 dBm at the output ports at 10.5 GHz. For operation with typical 25-dB isolation, the device is capable of operation up to 5.6-GHz BW at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band. The device is also shown to be operable up to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i> -band by simulation with ~15-GHz BW of 20-dB isolation. The proposed architecture is suitable for MMIC integration and system-on-chip applications.

WIDE-BAND HIGH ISOLATION SUBHARMONICALLY PUMPED RESISTIVE MIXER WITH ACTIVE QUASI-CIRCULATOR

A novel subharmonically pumped resistive mixer (SH- PRM) with a core chip dimension of 0:64 £ 0:65mm 2 is fabri- cated through a standard 0.18m CMOS process. An impedance- transforming active quasi-circulator is monolithically integrated with an nMOS fleld-efiect transistor (FET) to perform up-converter mix- ing while simultaneously enhancing all port isolation through a broad- band operation. The design analysis of impedance-transforming ac- tive quasi-circulator is also presented for matching between circulator and resistive transistor. As shown in the measured results, the mixer exhibits a 9{14.5dB conversion loss. All port-to-port isolations bet- ter than 16.5dB over a radio frequency (RF) of 10{20GHz can be achieved.

Active Quasi-Circulator MMIC Using OTAs

A very compact, active quasi-circulator is proposed and experimentally demonstrated in this work. It consists of an active balun and a current combiner using operational transconductance amplifiers in CMOS. Experimental results show that the insertion loss between the circulation ports is low and all three ports have input reflection coefficients below -10 dB. The chip operates from 1.5 to 2.7 GHz and it outperforms previously known monolithic microwave integrated circuit circulators covering this frequency range in terms of the S31 isolation, standing at -26 dB, as well as physical size: the integrated circuit measures only 0.25 mm2 including bonding pads.

ANALYSIS AND DESIGN OF NEW ACTIVE QUASI CIRCULATOR AND CIRCULATORS

This paper introduces two new type active quasi circulators and three new type active circulators which use the out- of-phase power divider/combiner, symmetric/anti-symmetric couplers and generic unilateral ampliflers. The proposed circuits are full-symmetric and composed of conventional microwave devices. Analytical relations for active quasi circulator modules are described. These modules have many variations and can be used for very wide frequency range depending on the type of the employed unilateral amplifler, power divider/combiner and symmetric/anti-symmetric couplers. Based on the proposed conflgurations, analysis and design of n-port active circulators are presented. Also they can be used in MMICs as active quasi circulators, active circulators and in other high frequency applications.

Novel Active Quasi-Circulator With Phase Compensation Technique

A novel active quasi-circulator using phase compensation technique for wideband isolation is proposed. It is formed by configuring three transistors with a complimenting phase shifter for equalization. It provides wideband frequency operation with sufficient return loss and isolation between ports without the need for passive filters. This compensation technique minimizes the circulator's size compared with conventional ferrite circulators and is compatible with monolithic microwave integrated circuit technology. Experimental results show that the proposed quasi-circulator has insertion losses around 0 dB, return losses better than 10 dB at each ports and minimum isolation around 15 dB from 0.8 to 2.2 GHz. Good agreement is obtained between simulation and experimental results.

Active quasi-circulator realisation with gain elements and slow-wave couplers

A microstrip active quasi-circulator is presented using two generic amplifier blocks and two power couplers. The power couplers are parallel-coupled lines with a slow-wave structure in order to improve the isolation between ports of the quasi-circulator. A detailed analytic design procedure is presented for the slow-wave couplers based on the capacitive coupling modelling approach for coupled transmission lines. Experimental results show that the quasi-circulator has an insertion loss between 1 and −2 dB, a return loss better than 11 dB at each of the ports and an isolation better than 20 dB from 1.0 to 3.0 GHz. The input 1 dB compression point is 14 dB m at 2.4 GHz.