Distributed 2- and 3-bit W-band MEMS phase shifters on glass substrates

This paper presents state-of-the-art RF microelectromechanical (MEMS) phase shifters at 75-110 GHz based on the distributed microelectromechanical transmission-line (DMTL) concept. A 3-bit DMTL phase shifter, fabricated on a glass substrate using MEMS switches and coplanar-waveguide lines, results in an average loss of 2.7 dB at 78 GHz (0.9 dB/bit). The measured figure-of-merit performance is 93/spl deg//dB-100/spl deg//dB (equivalent to 0.9 dB/bit) of loss at 75-110 GHz. The associated phase error is /spl plusmn/3/spl deg/ (rms phase error is 1.56/spl deg/) and the reflection loss is below -10 dB over all eight states. A 2-bit phase shifter is also demonstrated with comparable performance to the 3-bit design. It is seen that the phase shifter can be accurately modeled using a combination of full-wave electromagnetic and microwave circuit analysis, thereby making the design quite easy up to 110 GHz. These results represent the best phase-shifter performance to date using any technology at W-band frequencies. Careful analysis indicates that the 75-110-GHz figure-of-merit performance becomes 150/spl deg//dB-200/spl deg//dB, and the 3-bit average insertion loss improves to 1.8-2.1 dB if the phase shifter is fabricated on quartz substrates.     

Distributed phase shifter with pyrochlore bismuth zinc niobate thin films

A monolithic Ku-band phase shifter employing voltage tunable Bi/sub 1.5/Zn/sub 1.0/Nb/sub 1.5/O/sub 7/ (BZN) thin film parallel plate capacitors is reported. BZN films were deposited by radio frequency magnetron sputtering on single-crystal sapphire substrates. A nine-section distributed coplanar waveguide loaded-line phase-shifter structure was designed. A differential phase shift of 175/spl deg/ was achieved with a maximum insertion loss of 3.5 dB at 15 GHz, giving a figure of merit /spl sim/50/spl deg//dB. To the best of our knowledge, this is the first demonstration of a monolithic tunable microwave circuit using BZN thin films.     

Arbitrary dual-band components using composite right/left-handed transmission lines

Arbitrary dual-band microstrip components using composite right/left-handed (CRLH) transmission lines (TLs) are presented. Theory, synthesis procedure, and implementation of the dual-band quarter-wave (/spl lambda//4) CRLH TL are presented. Arbitrary dual-band operation is achieved by the frequency offset and the phase slope of the CRLH TL. The frequency ratio of the two operating frequencies can be a noninteger. The dual-band /spl lambda//4 open/short-circuit stub, dual-band branch-line coupler (BLC), and dual-band rat-race coupler (RRC) are also demonstrated. The performances of these dual-band components are demonstrated by both simulated and measured results. Insertion loss is larger than 23 dB for the shunt /spl lambda//4 CRLH TL open-circuit stub and less than 0.25 dB for the shunt /spl lambda//4 CRLH TL short-circuit stub at each passband. The dual-band BLC exhibits S/sub 21/ and S/sub 31/ larger than -4.034 dB, return losses larger than 17 dB, isolations larger than 13 dB, phase differences 90/spl deg//spl plusmn/1.5/spl deg/, and gain imbalance less than 0.5 dB at each passband. The dual-band RRC exhibits S/sub 21/ and S/sub 31/ larger than -4.126 dB, return losses larger than 12 dB, isolations larger than 30 dB, phase difference 180/spl deg//spl plusmn/4/spl deg/, and gain imbalance less than 0.2 dB at each passband.     

W-band CPW RF MEMS circuits on quartz substrates

This paper presents W-band coplanar waveguide RF microelectromechanical system (MEMS) capacitive shunt switches with very low insertion loss (-0.2 to -0.5 dB) and high-isolation (/spl les/ -30 dB) over the entire W-band frequency range. It is shown that full-wave electromagnetic modeling using Sonnet can predict the performance of RF MEMS switches up to 120 GHz. Also presented are W-band 0/spl deg//90/spl deg/ and 0/spl deg//180/spl deg/ switched-line phase shifters with very good insertion loss (1.75 dB/bit at 90 GHz) and a wide bandwidth of operation (75-100 GHz). These circuits are the first demonstration of RF MEMS digital-type phase shifters at W-band frequencies and they outperform their solid-state counterparts by a large margin.     

2.4 GHz continuously variable ferroelectric phase shifters using all-pass networks

Continuously variable ferroelectric (BST on sapphire) phase shifters based on all-pass networks are presented. An all-pass network phase shifter consists of only lumped LC elements, and thus the total size of the phase shifter is kept to less than 2.2 mm /spl times/ 2.6 mm at 2.4 GHz. The tunability (C/sub max//C/sub min/) of a BST interdigital capacitor is over 2.9 with a bias voltage of 140 V. The phase shifter provides more than 121/spl deg/ phase shift with the maximum insertion loss of 1.8 dB and the worst case return loss of 12.5 dB from 2.4 GHz to 2.5 GHz. By cascading two identical phase shifters, more than 255/spl deg/ phase shift is obtained with the maximum insertion loss of 3.75 dB. The loss figure-of-merit of both the single- and double-section phase shifters is over 65/spl deg//dB from 2.4 GHz to 2.5 GHz.     

On the feasibility of CMOS multiband phase shifters for multiple-antenna transmitters

We present the design of an integrated multiband phase shifter in RF CMOS technology for phased array transmitters. The phase shifter has an embedded classical distributed amplifier for loss compensation. The phase shifter achieves a more than 180/spl deg/ phase tuning range in a 2.4-GHz band and a measured more than 360/spl deg/ phase tuning range in both 3.5-GHz and 5.8-GHz bands. The return loss is less than -10dB at all conditions. The feasibility for transmitter applications is verified through measurements. The output power at a 1-dB compression point (P/sub 1 dB/) is as high as 0.4dBmat 2.4GHz. The relative phase deviation around P/sub 1 dB/ is less than 3/spl deg/. The design is implemented in 0.18-/spl mu/mRF CMOS technology, and the chip size is 1200/spl mu/m /spl times/ 2300 /spl mu/m including pads.     

40 Gbit/s electroabsorption modulators with impedance-controlled electrodes

A novel travelling-wave electroabsorption optical modulator, electrically matched for 50 /spl Omega/ loads of driving circuit drivers, was developed. The scattering parameter of electric reflection (S/sub 11/) from this modulator is less than -20 dB at 20 GHz. It can thus enable a 40 Gbit/s, 2 km SMF transmission with a 0.3 dB penalty at a 1.3 /spl mu/m wavelength.     

Two-stage broadband high-gain W-band amplifier using 0.1-/spl mu/m metamorphic HEMT technology

We report broadband high-gain W-band monolithic microwave integrated circuit amplifiers based on 0.1-/spl mu/m InGaAs-InAlAs-GaAs metamorphic high electron mobility transistor (MHEMT) technology. The amplifiers show excellent S/sub 21/ gains greater than 10 dB in a very broad W-band frequency range of 75-100 GHz, thereby exhibiting a S/sub 21/ gain of 10.1 dB, a S/sub 11/ of -5.1 dB and a S/sub 22/ of -5.2 dB at 100 GHz, respectively. The high gain of the amplifier is mainly attributed to the performance of the MHEMTs exhibiting a maximum transconductance of 691 mS/mm, a current gain cutoff frequency of 189 GHz, and a maximum oscillation frequency of 334 GHz.     

Arbitrarily dual-band components using simplified structures of conventional CRLH TLs

Microwave components with nonlinear phase responses are developed using a simplified composite right/left-handed (CRLH) transmission-line (TL) structure without the series capacitance or the shunt inductance. Using such a simplified CRLH structure, arbitrarily dual-band microstrip components have been realized in compact sizes such as a quarter-wavelength short-circuited stub and dual- band branch-line couplers. Simulation and measurement results are given to demonstrate the efficiency and good performance of the proposed components. For the quarter- wavelength short-circuited stub based on the simplified CRLH-TL structure without the series capacitance, it has been shown that the insertion loss is less than -0.1dB. For the arbitrarily dual-band branch-line coupler, experiment results exhibit that S/sub 21/ and S/sub 31/ are larger than -3.6dB, the isolations are smaller than -30dB, the return losses are smaller than -20dB, and the phase differences are within 90/spl deg//spl plusmn/1.8/spl deg/.     

Miniature and tunable filters using MEMS capacitors

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (/spl epsiv//sub r/ = 3.8, tan/spl delta/ = 0.0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-Q MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (/spl epsiv//sub r/ = 4.6, tan/spl delta/ = 0.006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 /spl plusmn/ 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP/sub 3/ of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP/sub 3/ increases to >50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz//spl mu/s.     

Distributed MEMS analog phase shifter with enhanced tuning

The design, fabrication, and measurement of a tunable microwave phase shifter is described. The phase shifter combines two techniques: a distributed capacitance transmission line phase shifter, and a large tuning range radio frequency (RF) microelectromechanical system (MEMS) capacitor. The resulting device is a large bandwidth, continuously tunable, low-loss phase shifter, with state-of-the-art performance. Measurements indicate analog tuning of 170/spl deg/ phase shift per dB loss is possible at 40 GHz, with a 538/spl deg/ phase shift per centimeter. The structure is realized with high-Q MEMS varactors, capable of tuning C/sub max//C/sub min/= 3.4. To our knowledge, this presents the lowest loss analog millimeter wave phase shifter performance to date.     

Composite right/left-handed transmission line based compact resonant antennas for RF module integration

Several electrically small resonant antennas employing the composite right/left-handed transmission line (CRLH-TL) are presented for integration with portable RF modules. The proposed antenna designs are based on the unique property of anti-parallel phase and group velocity of the CRLH-TL at its fundamental mode. In this mode, the propagation constant increases as the frequency decreases, therefore, a small guided wavelength can be obtained at a lower frequency to provide the small /spl lambda//sub g//2 resonant length used to realize a compact antenna design. Furthermore, the physical size and the operational frequency of the antenna depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL, including series inductance, series capacitance, shunt inductance and shunt capacitance. Optimization of these parameters as well as miniaturization techniques of the physical size of unit cell is investigated. A four unit-cell resonant antenna is designed and tested at 1.06 GHz. The length, width and height of the proposed antenna are 1/19/spl lambda//sub 0/, 1/23/spl lambda//sub 0/ and 1/83/spl lambda//sub 0/, respectively. In addition, a compact antenna using a 2-D three by three mushroom like unit cell arrangement is developed at 1.17 GHz, showing that an increased gain of 0.6 dB and higher radiation efficiency can be achieved over the first prototype antenna. The same design is applied in the development of a circularly polarized antenna operating at 2.46 GHz. A 116/spl deg/ beamwidth with axial ratio better than 3 dB is observed. The physical size of the proposed mushroom type small antenna and the circularly polarized antenna is 1/14/spl lambda//sub 0/ by 1/14/spl lambda//sub 0/ by 1/39/spl lambda//sub 0/ and 1/10/spl lambda//sub 0/ by 1/10/spl lambda//sub 0/ by 1/36/spl lambda//sub 0/, respectively.     

30-100-GHz inductors and transformers for millimeter-wave (Bi)CMOS integrated circuits

Silicon planar and three-dimensional inductors and transformers were designed and characterized on-wafer up to 100 GHz. Self-resonance frequencies (SRFs) beyond 100 GHz were obtained, demonstrating for the first time that spiral structures are suitable for applications such as 60-GHz wireless local area network and 77-GHz automotive RADAR. Minimizing area over substrate is critical to achieving high SRF. A stacked transformer is reported with S/sub 21/ of -2.5 dB at 50 GHz, and which offers improved performance and less area (30 /spl mu/m/spl times/30 /spl mu/m) than planar transformers or microstrip couplers. A compact inductor model is described, along with a methodology for extracting model parameters from simulated or measured y-parameters. Millimeter-wave SiGe BiCMOS mixer and voltage-controlled-oscillator circuits employing spiral inductors are presented with better or comparable performance to previously reported transmission-line-based circuits.     

Low-power programmable gain CMOS distributed LNA

A design methodology for low power MOS distributed amplifiers (DAs) is presented. The bias point of the MOS devices is optimized so that the DA can be used as a low-noise amplifier (LNA) in broadband applications. A prototype 9-mW LNA with programmable gain was implemented in a 0.18-/spl mu/m CMOS process. The LNA provides a flat gain, S/sub 21/, of 8 /spl plusmn/ 0.6dB from DC to 6.2 GHz, with an input impedance match, S/sub 11/, of -16 dB and an output impedance match, S/sub 22/, of -10 dB over the entire band. The 3-dB bandwidth of the distributed amplifier is 7GHz, the IIP3 is +3 dBm, and the noise figure ranges from 4.2 to 6.2 dB. The gain is programmable from -10 dB to +8 dB while gain flatness and matching are maintained.     

A 2-bit miniature X-band MEMS phase shifter

The design and performance of a compact low-loss X-band true-time-delay (TTD) MEMS phase shifter fabricated on 8-mil GaAs substrate is described. A semi-lumped approach using microstrip transmission lines and metal-insulator-metal (MIM) capacitors is employed for the delay lines in order to both reduce circuit size as well as avoid the high insertion loss found in typical miniaturized designs. The 2-bit phase shifter achieved an average insertion loss of -0.70 dB at 9.45 GHz, and an associated phase accuracy of /spl plusmn/1.3/spl deg/. It occupies an area of only 5 mm/sup 2/, which is 44% the area of the smallest known X-band MEMS phase shifter . The phase shifter operates over 6-14 GHz with a return loss of better than -14 dB.     

An Analog RF MEMS Slotline True-Time-Delay Phase Shifter

An analog RF microelectromechanical systems (MEMS) slotline true-time-delay (TTD) phase shifter is presented for use in conjunction with tapered slot antennas, such as the Vivaldi aerial and the double exponentially tapered slot antenna. The design is a scalable distributed loaded-line cascade of 62 novel differential slow-wave unit cells. Each differential slow-wave unit cell comprises an electrically short slotline section, which is loaded with a shunt impedance consisting of two center-pulled contactless fixedfixed beam RF MEMS varactors in series, sharing a common electrode. The analog RF MEMS slotline TTD phase shifter is demonstrated on a borosilicate glass wafer using a microfabrication process requiring six masks. It is designed for transistortransistor logic bias voltage levels and exhibits a measured phase shift of 28.2$^{circ}/{hbox{dB}}$ (7.8 ps/dB) and 59.2$^{circ}/{hbox{cm}}$ at 10 GHz, maintaining a 75-$Omega$ differential impedance match $(S_{11_{dd}}<-15.8 {hbox{dB}})$ . The input third-order intercept point is 5 dBm at 10 GHz for a $Delta{ f}$ of 50 kHz, measured in a 100-$Omega$ differential transmission line system. Design and fabrication opportunities, concerning distortion and loss reduction, as well as packaging, are highlighted.      

A matrix amplifier in 0.18-/spl mu/m SOI CMOS

A fully integrated matrix amplifier with two rows and four columns (2-by-4) fabricated in a three-layer metal 0.18-/spl mu/m silicon-on-insulator (SOI) CMOS process is presented. It exhibits an average pass-band gain of 15 dB and a unity-gain bandwidth of 12.5 GHz. The input and output ports are matched to 50 /spl Omega/ using m-derived half sections; the measured S/sub 11/ and S/sub 22/ values exceed -7 and -12 dB, respectively. Integrated in 2.0/spl times/2.9mm/sup 2/, it dissipates 233.4 mW total from 2.4- and 1.8-V power supplies.     

Packaged single-ended CMOS low noise amplifier with 2.3 dB noise figure and 64 dBm IIP/sub 2/

A single-ended low noise amplifier (LNA) implemented in a foundry 0.18 /spl mu/m CMOS process is tested on a PC board using the chip-on-board technique. The measured S/sub 11/ and S/sub 22/ are less than -10 dB over 5.15-5.35 GHz, which is the lower subband of UNII and HIPERLAN/2 band. The measured noise figure is 2.0 dB and power gain is 15.5 dB at 5.15 GHz, while drawing 5.8 mA of current from a 1.8 V supply. The measured IIP/sub 2/ is greater than 64 dBm. This extremely high IP/sub 2/ is due to the tuned response of the LNA. The LNA is suitable for WLAN applications in the lower UNII and HIPERLAN/2 subband.     

On-chip micromachined solenoid balun for RF-SOC applications

A transformer balun is fabricated by using a post-CMOS compatible MEMS process. The novel concave-suspended solenoid balun can be integrated with radio-frequency system-on-chips (RF-SOCs). In the frequency range 0.5-10 GHz, the tested balun shows less than 0.7 dB amplitude imbalance and less than 1.5deg phase imbalance. After tuning, the transformer balun can match between a 100 Omega single-ended port and two 50 Omega differential ports. At the two differential ports, insertion losses of -1.5 and -0.8 dB are obtained at 5-GHz centre frequency, more than 40% bandwidth of S ₁₁ is achieved.     

Exact analysis of maximum available gain and unilateral gain including phase angle of S21

Exact formulae are presented for both maximum available gain (G/sub ma/) and unilateral gain (U), which include both the magnitude and phase angle of the S/sub 21/ parameter. The result for G/sub ma/ is not unique since there are many possible solutions to simultaneously match S/sub 11/ and S/sub 22/ when k>1. For the phase angle of U, the result tends to become 180/spl deg/ when using the topology of a variable coupler, a line stretcher, and a feedback amplifier. From the verifications, an amplifier using the unilateralizing technique will achieve 4-6 dB higher gain than that of the G/sub ma/ amplifier.