Yu Ann Lai

A 23–37 GHz Miniature MMIC Subharmonic Mixer

A novel configuration of subharmonic mixer using an anti-parallel diode pair is presented for operating over the 23-37 GHz band. The monolithic microwave integrated circuit is implemented by GaAs 0.15 mum PHEMT technology with the compact size of 0.85 times 0.85 mm2. This mixer employs a directional coupler, LC low-pass filter, and a short stub for isolating three ports corresponding to radio frequency (RF), local oscillation (LO) input, and intermediate frequency (IF) output ports. The directional coupler also provides impedance transformation between the diode pair, RF, and LO ports. This makes the subharmonic mixer more compact and flexible. The best conversion loss of the subharmonic mixer is 9.4 dB, and the LO-to-RF and LO-to-IF isolations are better than 22 and 31 dB, respectively.

A Compact Ka-Band Planar Three-Way Power Divider

A Ka-band planar three-way power divider which uses the coupled line instead of the transmission line is proposed to reduce chip size. The proposed planar topology, different from the conventional Wilkinson power divider, is analyzed and can provide not only compact but also dc block characteristics, which are very suitable for monolithic microwave integrated circuit applications. The divider implemented by a pHEMT process shows an insertion loss less than 5.1 dB and an output isolation better than 17 dB. A return loss less than 18 dB and a phase difference of 4.2deg at 30 GHz can be achieved. Finally, good agreements between the simulation and experimental results are shown.

A Variable Conversion Gain Star Mixer for Ka-Band Applications

A variable conversion gain star mixer for Ka-band applications has been presented. This monolithic microwave integrated circuit was implemented on AlGaAs/InGaAs/GaAs pseudomorphic high-electron-mobility transistor process with a chip size of 1.7times1.7 mm2. The mixer is modified from conventional star mixer to apply dc bias. The conversion gain of the mixer, controlled by the voltage of the diodes, could be applied to meet gain compensation requirements in communication systems. From the measured results, the circuit can provide 11.9 dB conversion gain and 9.3 dB gain adjustment by controlling voltage from 0 to 0.7 V at 30 GHz.

A 10–40 GHz Broadband Subharmonic Monolithic Mixer in 0.18

A 10-40 GHz broadband subharmonic monolithic passive mixer using the standard 0.18 mum CMOS process is demonstrated. The proposed mixer is composed of a two-stage Wilkinson power combiner, a short stub and a low-pass filter. Likewise, the mixer utilizes a pair of anti-parallel gate-drain-connected diodes to achieve subharmonic mixing mechanism. The two-stage Wilkinson power combiner is used to excite a radio frequency (RF) and local oscillation (LO) signals into diodes and to perform broadband operation. The low-pass filter supports an IF frequency range from dc to 2.5 GHz. This proposed configuration leads to a die size of less than 1.1 times 0.67 mm 2 . The measured results demonstrate a conversion loss of 15.6-17.6 dB, an LO-to-RF isolation better than 12 dB, a high 2LO-to-RF isolation of 51-59 dB over 10-40 GHz RF bandwidth, and a 1 dB compression power of 8 dBm.

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A novel configuration of doubly balanced mixer is presented for operating over the 26-38 GHz band. The monolithic microwave integrated circuit (MMIC) was implemented by GaAs 0.15 mum pHEMT technology with the compact size of 1times2.5 mm2. A 180deg hybrid circuit and two identical Marchand baluns were employed to achieve good port-to-port isolation. They also have wide band performance, make the mixer more compact, and simplify IF extraction. This mixer has a conversion loss of better than 6 dB, a dc-10 GHz IF bandwidth, and the LO-to-RF and LO-to-IF isolations are better than 20 dB and 29 dB, respectively.

m CMOS Technology

A novel and compact 16-44 GHz ultra-broadband doubly balanced monolithic ring mixer for Ku- to Ka-band applications implemented with a 0.15-mum pHEMT process is presented. The proposed mixer is composed of a C-band miniature spiral balun and a 180deg hybrid formed with an interdigital coupler, a low-pass pi-network, and a high-pass T-network. The 180deg hybrid eliminates the use of a cross-over structure for application in the balanced mixer, as well as provides an output port for the RF extraction of up-converter application. This proposed configuration leads to a die size of less than 0.8times0.8 mm2 . From the measured results, the mixer exhibits an 11-14 dB conversion loss, a 27-50 dB high LO-to-IF isolation over 16-44 GHz RF/LO bandwidth, and a 1-dB compression power of 14 dBm for both down- and up-converter applications.

A 26–38 GHz Monolithic Doubly Balanced Mixer

A compact double-balanced frequency doubler with simple harmonic suppression and gain compensation functions is proposed. In order to enhance the suppression of fundamental and third harmonics of the doubler, the band-reject filter (BRF) is integrated into the Marchand balun, which also provides the ground for the coupler line of the balun. In addition, the simple bias circuit is applied to solve the gain variation, which improves the conversion efficiency at low input power. This doubler exhibits 11.7-16 dB conversion loss, while the fundamental suppression is better than 22.5 dB from 25 to 37 GHz. By controlling the voltage from 0 to 0.6 V, the doubler can increase the gain and provide better operational bandwidth.

A 16–44 GHz Compact Doubly Balanced Monolithic Ring Mixer

A compact Ka-band doubly balanced diode mixer with new phase relationships is demonstrated. In this design, a novel configuration was employed to have good performance while keeping compact size and simple intermediate frequency (IF) extraction. It is flexible not only in layout design, but also in the reduction of IF inductance. The chip dimension is as small as 0.851.35 mm, implemented by using a 0.15 m PHEMT technology. This mixer has a conversion loss between 9 to 12 dB, a dc-3.5 GHz IF bandwidth, and a good port-to-port isolation in Ka band.

Compact Doubler With Simple Harmonic Suppression and Gain-Compensation Functions

Compact double-balanced monolithic star mixers using 0.25 μm GaAs pHEMT process are presented. These star mixers adopt two novel types of the dual 180° hybrid structure, thereby reducing the chip size and eliminating complex layout. With multi-coupled lines technology, the proposed dual 180° hybrids are produced and applied to star mixers successfully. Furthermore, the proposed hybrids simplifies the star mixers IF extraction circuit to reduce the chip size and enhance the IF bandwidth. The results demonstrate wide operation bandwidth, low conversion loss and good port-to-port isolations with a size dimension of less than 0.81 mm2, could thus be obtained.

A New Ka-Band Doubly BalancedMixer Based on Lange Couplers

A novel configuration of double- balanced sub-harmonic mixer using a ring connected anti-parallel diode pair (RAPDP) is presented for operating in 26-30 GHz. The monolithic microwave integrated circuit (MMIC) was implemented with GaAs 0.15 mum PHEMT technology with the compact size of 0.85 x 0.85 mm2. The proposed mixer consists of two spiral transformer baluns and a band-reject filter. The RF spiral balun with a band-reject filter served by an L-C resonator is used to provide an output port for the IF extraction. The best conversion loss of the sub-harmonic mixer is 12.7 dB and LO-to-RF and LO-to-IF isolations are better than 24 dB and 28 dB respectively.