Monolithic Microwave IC Technologies and System Applications

This paper presents a unique design concept for a dual-frequency,electronically steerable, MM-wave phased array antenna using Monolithic Microwave Integrated Circuit (MMIC) technology. Such an antenna design will be found most attractive for satellite communication and missile seeker applications, where size, weight and power consumption are the most stringent requirements. The block diagram of a dual-frequency (20 GHz/30 GHz), electronically steerable, phased array antenna using MMIC technology is shown in Figure 1. Specific details on the critical RF components are also shown in Figure 1. Because of the location of the radiating elements on the hemispherical surface, the antenna is inherently capable of providing electronic scanning over 360 deg. in AZ-plane and over plus/minus 60 deg. in EL-plane. This electronically steerable phased array antenna will generate multiple beams in the AZ-plane with consistent bandwidth and pattern symmetry. This design exploits true integration of printed circuit antenna technology, GaAs active device technology, MM-wave microstrip technology and printed circuit time delay phase shifting element technology. This design employs microstrip periodic structure transmission line sections as time delay phasing elements, which requires no input power. The printed circuit microstrip line sections will be used as feed networks. Two distinct dual- frequency, antenna element fabrication techniques, namely, stacked-patch element (Figure 2a) and collocated, interleaved-patch element (Figure 2b), were investigated in terms of cost, size, performance and complexity. Tradeoff studies performed seem to indicate that stacked-patch element approach will offer minimum size and weight. The physical dimensions shown in Figure 1 and 2 are computed for 20 GHz and 30 GHz operations. All the electronics, control circuits and RF MMIC circuits can be located within the hemispherical structure. The input power, overall system size and weight will depend on the antenna gain requirement, inter-element spacing, number of elements and phase shifter types. It is important to mention that delay line phasing networks using printed circuit periodic structures will provide optimum flexibility in phasing of the antenna elements with minimum loss. The proposed antenna architecture for a dual-frequency operation using a common aperture and MMIC technology seems to offer an antenna system with minimum cost, size, weight and power consumption.

Modern reconfigurable communication systems demand microwave voltage-controlled oscillators (VCOs) possessing an octave-wide bandwidth. Many advanced applications require also a low phase noise and a low current consumption for such VCOs. To meet an octave-bandwidth specification in combination with a low phase noise and a low current consumption it is desirable to implement a microwave monolithic integrated circuit (MMIC) technology. In-house gallium arsenide (GaAs) MMIC technology is implemented to build VCOs in this work. At the same time, in order to achieve a high-Q wide frequency tuning range, we implemented also a discrete variable capacitance diode (varicap). The discrete varicap is stacked above MMIC oscillator chip. A vertical design structure of the discrete varicap guarantees a high overlap capacitance ratio (K>20) along with reduced affect of the parasitic reactance. A high overlap capacitance ratio is needed for an octave-wide frequency tuning, while reduced affect of the parasitic reactance increases Q-factor of the VCO resonator. Hence, a sequential integration of the discrete varicap over monolithic oscillator chip resolves referred tough challenges in the design of VCO. Integrated VCO is finally packaged as a surface-mount device (SMD). At that SMD ceramic package is sealed with the metal lid. The oscillator circuitry is based on the conventional negative resistance approach with a positive feedback realized by common-source capacitance. An active element of the oscillator is a pseudomorphic high electron-mobility transistor (pHEMT). The gate length of a transistor is 0.15 µm. The width of the gate varies from 240 µm to 360 µm depending on working frequencies of the VCO. The varicap is built on the GaAs epitaxial heterostructure having customized gradient doping profile with abrupt junction. Nonlinear behavioral model of the varicap is extracted from the diode measurements and is further used for VCO simulation. Two types of VCO have been designed, fabricated and tested. First (second) type of VCO provides a tuning range from 5 to 10 GHz (from 10 GHz to 20 GHz), respectively. The measurement results demonstrate an output power of 3.9 dBm; a current consumption of 30 mA at a supply voltage of 5 V; a phase noise of minus 90 dBc/Hz at 100 kHz offset (minus 85 dBc/Hz at 100 kHz offset) for the first (second) type of VCO, respectively.

Future communications satellites are likely to use gallium arsenide (GaAs) monolithic microwave integrated-circuit (MMIC) technology in most, if not all, communications payload subsystems. Multiple- scanning beam antenna systems are expected to use GaAs MMIC's to increase functional capability, to reduce volume, weight, and cost, and to greatly improve system reliability. RF and IF matrix switch technology based on GaAs MMIC's is also being developed for these reasons. MMIC technology, including gigabit-rate GaAs digital integrated circuits, offers substantial advantages in power consumption and weight over silicon technologies for high-throughput, on-board baseband processor systems. In this paper, current developments in GaAs MMIC technology are described,and the status and prospects of the technology are assessed.

Rapid expansion of microwave systems in phased array radar and commercial applications in the emerging wireless communication system areas requires affordable, compact, lightweight, reliable, solid state, integrated microwave transmit/receive (T/R) modules. Traditional microwave modules fabricated using microstrip-based hybrid/ monolithic integrated circuitry are incompatible with low cost, high volume, robotics manufacturing techniques for multi-chip microwave modules, because of the fragile nature of current 4 mil-thick gallium arsenide monolithic microwave integrated circuits (MMICs). Backside processing, including wafer thinning and via-hole ground electrode access, are also significant yield limiting factors for MMIC manufacturing. Hughes has developed a novel, robust, flip-chip approach for microwave T/R modules using self-aligned, solder reflow, multichip assembly techniques. The rugged (25 mil thick), passivated MMIC chips with coplanar waveguide circuitry, silicon-like, on-chip multilayer metal interconnects, with off-chip plated metal electrical/thermal paths offers major advantages over conventional MMICs (Table 1). Elimination of wafer thinning will be critical for processing and handling of large-diameter wafers. The use of plated metal thermal bumps directly on top of active circuit elements leads to 30% thermal property improvement over conventional GaAs MMICs.

This paper presents the design and measured results of a high-performance, miniature 6-/4-GHz receiver for on-board satellite applications. The receiver has a gain of 76 dB, weighs less than 500 g, and consumes less than 5 W of DC power. Extensive use is made of custom-designed monolithic microwave integrated circuit (MMIC) chips for all RF functions, to achieve a high level of reliability and miniaturization. A pseudomorphic high-electron-mobility transistor (p-HEMT) C-band low-noise amplifier with 40-dB gain and a room temperature minimum noise figure of approximately 0.85 dB is used in the front end. Gain adjustments are provided in l-dB steps at IF frequency between 3.5 and 4.5 GHz.

A 64-element, Ku-band, active phased-array antenna developed for application in communications satellites is presented. Antenna radiation pattern and spatial isolation measurements show good agreement with predictions. In order to minimize the performance variations among the array elements, the 5-b digital phase shifter, the 50-b digital attenuator, and the amplifiers have been realized using MMIC (monolithic microwave integrated circuit) technology. This allowed the realization of 64 active modules whose amplitude and phase variations over 11.7 to 12.7 GHz are within +or-1.5 dB and +or-10 degrees . The successful development of this broadband active phased array has demonstrated the maturity of MMIC technology and the feasibility of active arrays in future communications satellites. >

메타 물질의 한 형태인 LHTL(Left-Handed Transmission Line)과 기존의 전송 선로 형태인 RHTL(Right-Handed Transmission Line)을 이용하여 광대역 I-Q 벡터 신호 생성을 위한 <TEX>$90^{\circ}$</TEX> 커플러를 설계, 제작하고 측정을 하였다. LHTL과 RHTL 모두 커패시터와 인덕터를 이용하여 합성 전송 선로 형태로 구성함으로써, 그 크기를 최소화 하였다. 또한, 제안된 커플러 제작에 필요한 Wilkinson 전력 분배기를 합성 RHTL을 이용하여 간단하게 구현함으로써 전체 회로의 크기를 <TEX>$11mm{\times}12mm$</TEX>로 만들 수 있었다. 주파수 범위 0.8~1.25 GHz에 대해 출력의 위상 차이가 <TEX>$90^{\circ}{\pm}5^{\circ}$</TEX>를 유지함으로써 광대역 <TEX>$90^{\circ}$</TEX> 커플러를 작은 크기로 만들 수 있었다. 동 주파수 범위에 대해 삽입 손실을 1.6 dB 이하로, 반사 손실을 10.1 dB 이상으로 유지 가능했다. 필자가 아는 한 이는 그 주파수 대에서 가장 작은 광대역 <TEX>$90^{\circ}$</TEX> 커플러이며, MMIC(Monolithic Microwave Integrated Circuit)로 만들 경우 그 크기를 훨씬 더 줄일 수 있을 것이다. By using LHTL(Left-Handed Transmission Line) which is a form of a metamaterial and conventional RHTL (Right-Handed Transmission Line), we designed, fabricated and tested a broadband <TEX>$90^{\circ}$</TEX> coupler which is a basic circuit for I-Q vector signal generation. Synthetic LHTL and RHTL were implemented with capacitors and inductors only, that the size is minimized. Also, by implementing a Wilkinson power divider which is required for the suggested circuit using a synthetic RHTL, the size of whole circuit is only <TEX>$11mm{\times}12mm$</TEX>. For the frequency range 0.8~1.25 GHz, the phase difference at the outputs maintained <TEX>$90^{\circ}{\pm}5^{\circ}$</TEX> and thus, a broadband <TEX>$90^{\circ}$</TEX> coupler could be made in a compact form. for the same frequency range, the insertion loss is less than 1.6 dB and return loss is more than 10.1 dB. To the best of our knowledge, this is the smallest and broadband <TEX>$90^{\circ}$</TEX> coupler for the frequency range and if the circuit is made with MMIC(Monolithic Microwave Integrated Circuit) technology, the size will be reduced much further.

InP/InGaAsP/InGaAs avalanche photodiodes with sepa- rate absorption, grading, and multiplication regions (SAGM-APD's) have been fabricated from wafers grown by chemical beam epitaxy (CBE). These APD's exhibit low dark current ( 500-Mbit/s) lightwave sys- tems experiments have shown that avalanche photodiodes (APD's) can provide several decibels of improvement in receiver sensitivity compared to p-i-n photodiodes ( 11-(5). In long-wavelength (= 1.3- or 1.5-pm) lightwave receivers the highest sensitivities have been achieved with APD's having an InP multiplication region and an 1~,~~Ga,-,.~~As (subscripts deleted in following text) absorption region separated by a transition region consisting of one or more lattice-matched intermediate-bandgap In,Gal -,AsL.P1 -y layers, the separate absorption, grading, and multiplication regions (SAGM)- structure APD ( 11. To operate properly, the carrier concentra- tions and thicknesses of the different layers which comprise this structure must be controlled within very narrow tolerances (6). Although most of the SAGM-APD's that have been reported to date have been grown by liquid-phase epitaxy (LPE), the degree of precision and uniformity necessary to maintain the wafer parameters within the constraints required by this structure are difficult to achieve by this growth technique. Also, LPE is more difficult and more expensive to implement in large-scale production than vapor-phase tech- niques such as hydride vapor-phase epitaxy (VPE), metal- organic chemical vapor deposition (MOCVD), or molecular beam epitaxy (MBE). In the past, however, InP/In,- Gal-,As,P1-, photodetectors grown by MBE and MOCVD have not achieved performance characteristics as good as those grown by LPE due to the high background carrier concentra- tions of the In,Gal-,As,PI-, layers and the difficulty in achieving good InP/In,Gal -,As,P1 ->, interfaces. Recently, InPIInGaAsPiInGaAs SAGM-APD's grown by MOCVD (7) and VPE (8), (9) have been reported. In this paper we report on InP/InGaAsP/InGaAs SAGM-APD's grown by chemical beam epitaxy (CBE) (lo), a crystal growth technique that combines many of the advantages of MOCVD and MBE. A schematic cross section of the back-illuminated InP/

A high-performance four-stage monolithic microwave integrated circuit (MMIC) power amplifier chip has been developed using 0.3- mu m gate-length and molecular beam epitaxial (MBE) MESFET technologies. These power MMIC chips have been combined to constitute a 47-GHz power amplifier with an output power of 0.45 W and an associated gain of 16.6 dB. A saturated output power of over 0.58 W was also achieved at 47 GHz. These results represent the highest reported power and gain at U-band from a MMIC amplifier using a 0.3- mu m gate-length MESFET. This amplifier has potential application as a driver for a monolithic doubler to obtain more than 80 mW of transmitted power at 94 GHz for W-band system applications. >

GaAs monolithic frequency doublers in the 13-GHz band and 26-GHz band were designed and fabricated. These doublers use a uniplanar monolithic microwave IC (MMIC) structure. They are composed of coplanar waveguides, slotlines, and air bridges only on the upper side of the GaAs substrate. These uniplanar MMIC frequency doublers offer the advantages of smaller circuit size and simpler fabrication processes than microstrip-based MMICs. The fabricated doublers achieve a conversion gain of 2.9 dB at 12.4 GHz and a minimum conversion loss of 0.7 dB at 24.4 GHz. A 6.5-26.0-GHz frequency quadrupler is presented that uses a cascade connection of the doubler chips. It demonstrated stable operation without any adjustment and achieved a conversion loss of 10 dB. >

A wideband distributed GaAs MMIC (monolithic microwave IC) amplifier module developed for optical transmission systems is described. This module is assembled by an innovative packaging technique featuring a new multilayer ceramic-frame package with an improved impedance-matched film carrier. The newly designed package suppresses undesired modes arriving at grounded coplanar-waveguide terminals over a wide frequency bandwidth. For interconnection between the MMIC-chip electrode pads and the terminal pads of the package, a newly developed impedance-matched film carrier is used for module assembly having a wideband interconnection with a high mechanical strength and high reliability. The application of this packaging technique to GaAs distributed MMIC amplifier results in a 0.5 to 23 GHz, 5-dB flat gain that agrees well with the gain of an MMIC chip measured directly on-wafer. >

In this paper, we have first proposed a RF MEMS thermistor power sensor based on Wheatstone full-bridge structure. The proposed RF MEMS thermistor power sensor is fabricated using GaAs MMIC (monolithic microwave integrated circuit) technology. In this device, two parallel low TCR (temperature coefficient of resistance) heaters are employed to keep the impedance match stable. And a Wheatstone full-bridge formed by four identical thermistors is used for the unknown RF power measurement. To improve the sensitivity of the sensor, a MEMS substrate membrane is fabricated beneath the hot area to suppress longitudinal heat loss by back etching process. The whole structure is integrated with CPW transmission line, which has the potential of high integration density. Compared with traditional thermistor power sensor, this device has both advantages of stable impedance match and high sensitivity.

Chapter 5 Low-Pressure Metallo-Organic Chemical Vapor Deposition of GaxIn1−xAsyP1−y Alloys

This paper presents the results of the first W-band InP-based high electron mobility transistor-heterojunction bipolar transistor (HEMT-HBT) monolithic microwave integrated circuit (MMIC). The InP-based HBT and HEMT devices are monolithically integrated using selective molecular beam epitaxy (MBE). The amplifier demonstrates the highest frequency performance MMIC so far obtained with this technology. A single-stage HBT op amp current regulator is integrated with a single-stage HEMT amplifier in order to regulate and self-bias the MEMT device over process, temperature, and age variations. The HBT regulates the HEMT bias to within 3% of the bias current while consuming only a small fraction of the total dc power. The HEMT W-band amplifier achieves a radio frequency (RF) gain of 8.25 and 5.9 dB at 77 and 94 GHz, respectively. A minimum noise figure of 4.2 dB was also recorded at 93.5 GHz. The RF performance achieved from the HEMT amplifier using the InP-based HEMT-HBT integrated technology is comparable to that of InP-based single-technology HEMT performance.

This paper presents a comparison of the dark currents and differential resistance of photodiodes, obtained using p-type cadmium-mercury telluride (CdHgTe) layers doped with boron ions, grown by molecular-beam epitaxy (MBE) and liquid-phase epitaxy (LPE). The volt-ampere responses for diodes on CdHgTe layers with composition x=0.215, grown by MBE and LPE (x≈0.222) are characterized by various saturation currents (reverse bias −0.25V) of 1–2 and 5–10nA, even though the band gap is greater for the latter. In this case, the maximum differential resistance is 4×109 and 5×107Ω for diodes based on MBE and LPE layers, respectively. The experimental data are compared with the calculated values. Numerical modelling showed that, for MBE structures with low biases, the dark current is limited by the diffusion current and by the Shockley-Read-Hall current outside the n-p junction, whereas, in LPE structures, there is a substantial contribution of currents through traps in the depletion region.