Three broad-band miniature monolithic transformer singly balanced diode mixers for operation in the microwave and millimeter-wave bands are reported in this paper. The coupled-line equivalent models are used to synthesize the initial design of these transformers up to 50 GHz. The first one is a broad-band spiral transformer mixer, and the second one is a 21-GHz Marchand-type transformer mixer. These two mixers with chip sizes around 0.29 mm/sup 2/ exhibit bandwidths of 105% and 54.5%, respectively. We also propose a 30-GHz single-coiled transformer mixer, which has comparable performance with the first two mixers and reduced chip size. The single-coiled transformer mixer achieves a bandwidth of 100% with the chip size smaller than 0.25mm/sup 2/. In order to save chip area, all these transformers provide broad-band matching to the diodes directly. To the authors' knowledge, these mixers achieve the widest bandwidths with the smallest chip sizes among all passive balanced mixers using monolithic-microwave integrated-circuit processes in dc-40-GHz frequency range.

Compact and broad-band millimeter-wave monolithic transformer balanced mixers

It is shown analytically that impedance-transforming planar Marchand baluns can be designed. A GaAs monolithic CPW balun, transforming between a 50 /spl Omega/ source impedance and 160 /spl Omega/ load terminations has been realised to demonstrate the technique. The balun operates from 40 to 90 GHz with excellent performance.

40 to 90 GHz impedance-transforming CPW Marchand balun

A technique for reducing the isolation network's size in a Marchand balun needed for perfect all-ports matching and isolation is proposed in this letter. The proposed isolation circuit is realized using a coupled-line phase-inverter in place of the bulky 180/spl deg/ line section that has been previously proposed. Analysis of the proposed circuit yields the required relationship between the coupling coefficient and the electrical length of the coupler. Based on the design equations, the circuit is experimentally demonstrated at 1.8 GHz and has shown excellent results.

On miniaturization isolation network of an all-ports matched impedance-transforming Marchand Balun

We present the design and performance of two ultra-small MMIC double balanced mixers covering the 14 to 26 GHz band and the 18 to 32 GHz band, respectively. These passive mixers have a conversion loss of better than 8 dB with an LO to RF isolation of better than 30 dB. Both mixers are 0.48 mm/sup 2/ in die size, which is the smallest reported die size by a factor of 4 for mixers in these frequency ranges.

Ultra-small MMIC mixers for K- and Ka-band communications

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 16–44 GHz Compact Doubly Balanced Monolithic Ring Mixer

This paper describes a doubly balanced monolithic ring mixer using a unique planar balun consisting of a Marchand section followed by a coupled-line structure. The latter provides additional even-mode rejection and a convenient point for IF extraction. The mixer achieves low conversion loss and high isolation over an 18-40 GHz RF/LO bandwidth and a dc-10 GHz IF bandwidth.

A. K. Oki

Papers

An 18-40 GHz monolithic ring mixer