Rolf Vogt

Compact reflective-type phase-shifter MMIC for C-band using a lumped-element coupler

The design and results of an ultra-compact single-load reflective-type monolithic-microwave integrated-circuit phase shifter at 6.2 GHz for a satellite radar system is presented in this paper, which has been fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process. A 3-dB 90/spl deg/ coupler with lumped elements enables significant circuit size reduction in comparison to former approaches applying microstrip branch line or Lange couplers. Phase control is enabled using MESFET varactors with capacitance control ratios (C/sub max//C/sub min/) of only four. Equations are derived to precisely describe the phase control ranges versus capacitance control ratios for different load configurations to allow efficient optimizations. Furthermore, the design tradeoff between low loss and high phase control range is discussed. Within a phase control range of 210/spl deg/, a loss of 4.9 dB/spl plusmn/0.9 dB and a 1-dB input compression point of higher than 5 dBm was measured for the designed phase shifter. The circuit size is less than 0.5 mm/sup 2/, which, to our knowledge, is the smallest reflective-type phase-shifter size reported to date.

Calibratable adaptive antenna combiner at 5.2 GHz with high yield for laptop interface card

This paper presents a calibratable adaptive antenna combiner with three branches for high-performance radio local area network at 5.2 GHz. The system was mounted on a reinforced duroid substrate and enables the integration in a laptop interface card. Each branch consists of a bent stacked slot antenna, a low-noise-amplifier monolithic microwave integrated circuit (MMIC) with antenna/calibration switching and a vector modulator MMIC with an amplitude control range of 15 dB and 3600 phase control range. The signals of the three branches are combined by an active adder MMIC. A calibration is proposed to significantly improve the phase and amplitude control resolution and the yield of the designed MMIC circuits, which were fabricated using a commercial GaAs process. Each branch has a maximum power gain of 16 dB, a noise figure of 3.3 dB, and a 1-dB output compression point of -4 dBm. The whole system draws less than 28 mA from a 2.7-V voltage supply. The total required MMIC chip size is 10.8 mm/sup 2/.

Compact monolithic integrated resistive mixers with low distortion for HIPERLAN

Three ultra-compact low-cost mixers, using either a single enhancement, depletion, or deep-depletion FET are presented and compared. They are designed for HIPERLAN and 802.11a receivers with radio and intermediate frequencies around 5.2 and 0.95 GHz, respectively. An improved MESFET large-signal model has been used to allow efficient optimizations of the circuits. The fully integrated mixers have been fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process and require a total chip area of only 0.5 mm/sup 2/. With an ultra-low local-oscillator (LO) power of -10 dBm, the enhancement FET mixer achieves a -4.7 dBm 1-dB input compression point, a 12.6-dB conversion loss, and a 13-dB noise figure. At a low LO power of -2.5 dBm, excellent dynamic properties are obtained for the depletion FET mixer with 2.6-dBm 1-dB input compression point, 8.3-dB conversion loss, and 8.8-dB noise figure. State-of the-art performances with 16-dBm 1-dB input compression point, 5.5-dB conversion loss, and 6.5-dB noise figure are reached for the deep depletion FET mixer at 10-dBm LO power.

Ultra compact, low loss, varactor tuned phase shifter MMIC at C-band

This paper presents a high yield, ultra compact, low loss phase shifter MMIC, realized with a commercial 0.6 /spl mu/m GaAs MESFET process. Phase shift is enabled by varying the varactor capacitances of the lumped element equivalent of a transmission line. Continuously adjustable phase control over 90/spl deg/ is achieved from 4 GHz up to 6 GHz, with a loss of less than 2.2 dB. At 5.2 GHz, a loss of 1.2 dB and a loss variation of /spl plusmn/0.5 dB is measured. Phase and loss variations for several circuits from different wafers are within /spl plusmn/1/spl deg/ and /spl plusmn/0.1 dB, respectively, indicating low dependences on process variations. The phase shifter requires a circuit size of only 0.2 mm/sup 2/, which to our knowledge is the smallest size for a continuously adjustable passive phase shifter with comparable performance, reported to date.

Multiband monolithic BiCMOS low-power low-IF WLAN receivers

This letter presents the design, implementation, and measurements of two monolithic low-IF receivers compliant with the main WLAN standards. The first receiver targets the three 5GHz U-NII bands, while the second allows dual-band operation in the 2GHz and 5GHz bands. Fabricated in a 47GHz-f/sub t/ BiCMOS technology, both consist of a low-noise preamplifier, two matched active singly-balanced mixers and two polyphase filters, used to generate quadrature LO signals and provide image-rejection. The single-band receiver exhibits 25 dB of conversion gain, 8.9 dB of NF and -19 dBm of P/sub 1 dB/, while consuming 19 mW. The dual-band receiver shows similar performances in the 5GHz band, and extends its operation in the 2GHz band, achieving 33.4dB of conversion gain, 4.1dB of NF and -26dBm of P/sub 1 dB/, while consuming 14.9mW.

5-6 GHz low-noise active antenna array for multi-dimensional channel-sounding

The design and measurement of a 5-6 GHz active receiving antenna array is presented. To obtain a compact and robust design, active downconverters are monolithically integrated using a standard 0.6 /spl mu/m-MESFET process and combined with planar linearly polarized aperture-coupled patch antennas. A very low noise figure of 3.5 dB and a total conversion gain of 30 dB is achieved. The use of dedicated monolithically integrated components leads to very low gain and phase variations. This active array will be used in a multi dimensional channel sounder.

High power-density monolithic linear X-band power amplifier using a low-cost MESFET technology

A physically small high-efficiency linear class-A monolithically integrated power amplifier is presented in this work. The power amplifier was fabricated on a general-purpose high-volume 0.6 /spl mu/m GaAs MESFET process. The small chip size of 0.32 mm/sup 2/ could be obtained through the use of microstrip transmission lines instead of lumped components. The circuit delivers a maximum linear output power of 24.2 dBm. The monolithic microwave integrated circuit (MMIC) exhibits a power density per chip area of 0.82 W/mm/sup 2/ at 12.2 GHz. At present, this value is amongst the highest reported in the open literature. A high power added efficiency for class-A operation of 33.9 % as well as a maximum small-signal gain of 8.3 dB was achieved. Using a general-purpose process, instead of a dedicated power process, allows the integration of the power amplifier with other RF front-end blocks in next-generation X-band communication systems targeting mass-production.

A versatile calibration method for small active antenna arrays

A novel method is introduced to determine the gain and phase inequalities in antenna arrays that are caused by active components. This method makes use of the reciprocity of a single transmission line that propagates a calibration signal to all elements. This approach avoids a symmetric divider network and therefore it can be easily applied to two-dimensional, not equally spaced or non-planar arrays. An estimation of the systematic error is given. The concept is experimentally verified.

A low-power SiGe-HBT active double-balanced mixer for compact integrated C-band wireless-LAN receivers

This paper presents the design, implementation and measurements of a C-band down-conversion active mixer. A Gilbert topology has been modified to provide RF power and noise matching, in order to improve the overall noise behavior. The circuit was fabricated in a 47 GHz BiCMOS process, achieving voltage conversion gain of 24 dB, double-side-band noise figure of 9.5 dB, P/sub 1dB/ and iIP/sub 3/ of -11 dBm and -4 dBm, respectively. Current consumption is 4 mA from a 3 V supply.

Reduction of mutual coupling in active antenna arrays by optimized interfacing between antennas and amplifiers

This paper discusses the reduction of mutual coupling in active antenna arrays. A broadband lumped-element circuit model is developed for an array of aperture-coupled patch antennas. This allows simulating and optimizing the mutual coupling in a standard circuit simulator. Experimental results at 5.5 GHz demonstrate that the mutual coupling can be significantly reduced by adjusting the electrical distance between the amplifier and the antenna phase center. This simple technique proved to be useful especially for active antenna arrays based on standard MMIC amplifiers.