G.A. Morin

Compact MMIC CPW and asymmetric CPS branch-line couplers and Wilkinson dividers using shunt and series stub loading

Circuit size may be reduced by up to 60% by embedding series and shunt uniplanar stubs inside the main uniplanar line since this reuses physical space in the longitudinal direction. This size-efficient stub loading of the main uniplanar line results in robust options for designing compact K-band 90/spl deg/ hybrid couplers and Wilkinson dividers. The approach is confirmed by experimental results that agree well with theory up to at least 30 GHz using both coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS). Furthermore, these couplers and dividers do not use lumped inductors or capacitors and, consequently, have excellent design accuracy even at millimeter-wave frequencies. Additionally, it is shown that it is possible to design an ACPS 90/spl deg/ branch-line coupler without the conventional CPW quarter wavelength transformers used to match the input and output port characteristic impedances.

The integration of thin-film microstrip and coplanar technologies for reduced-size MMICs

This paper proposes the integration of coplanar waveguide (CPW) and thin-film microstrip transmission lines to achieve size reduction of monolithic microwave integrated circuits (MMICs). The proposed structures take advantage of the multilevel metallization processes offered in MMIC technology. A very compact 90/spl deg/ CPW branchline coupler, operating at 44 GHz, is used to illustrate the technique. In comparison with conventional hybrid couplers, this coupler offers lower insertion loss and significantly smaller dimensions. The area of the coupler is approximately 65% of a conventional coupler. This paper also presents a family of novel series/shunt matching stub structures based on the CPW/thin-film microstrip combination. The technique allows a reduction in the length of matching stubs of approximately 50% by collocating multiple stubs together. Simulated and experimental results are presented in support of the novel structures.

A novel compact uniplanar MMIC Wilkinson power divider with ACPS series stubs

Short-circuit series stubs realized in the signal conductor of an asymmetric coplanar stripline (ACPS) transmission line are investigated as a circuit element in order to achieve a significant size reduction of a MMIC Wilkinson divider. A simple ideal transmission line equivalent circuit is used to model the ACPS line/stub combination yielding good agreement with EM simulation. The stubs are then utilized to shorten the /spl lambda//4 transmission lines by approximately 35% in a Wilkinson divider application at 23 GHz.

Size Reduction of a MMIC Direct Up-Converter at 44 GHz in Multilayer CPW Technology Using Thin-Film Microstrip Stubs Loading

This paper proposes a novel compact multilayer 44.5-GHz coplanar waveguide (CPW) single-sideband (SSB) subharmonically pumped (SHP) mixer for direct up-conversion GaAs monolithic microwave integrated circuit. It uses previously developed thin-film microstrip (TFMS) and CPW structures for capacitive and inductive loading techniques to drastically reduce its size. The SSB SHP mixer uses 50-MHz in-phase and quadrature signals to directly modulate the second harmonic of a 22.25-GHz carrier to produce the required 44.55-GHz RF output. Two pairs of antiparallel diodes reduce feedthrough of the fundamental 22.25-GHz signal to the RF output while novel CPW/TFMS-based structures provide matching. This 1.2times1.5 mm2 chip uses a lumped Wilkinson divider as a local-oscillator divider and a previously developed reduced size 90deg coupler. The SSB SHP mixer acts as an up-converter with a measured conversion gain of -10plusmn1 dB and the lower sideband suppression is greater than 23 dB across the RF bandwidth of 43.5-45.5 GHz. Additionally, it is shown that the RF port return loss is better than 20 dB, and 2timesfLO was suppressed by 21 dB over the same band. The circuit also does not require any dc bias. Compared to the conventional SSB SHP mixer, a 70% reduction in circuit area was achieved with better performances

A novel compact multi-layer MMIC CPW branchline coupler using thin-film microstrip stub loading at 44 GHz

A very compact 90/spl deg/ CPW branchline coupler at 44 GHz for Ka/K-band, advanced SATCOM terminal systems operating in the 20/44 GHz frequency bands is reported. This coplanar coupler structure using two metallization layers separated by a thin dielectric sheet on GaAs was investigated. This arrangement provides additional degrees of freedom compared to standard coplanar line structures resulting in extremely compact couplers suitable for monolithic integration. The proposed method takes advantage of the coexistence of the CPW lines and shunt thin film microstrip stubs. The coupler does not use lumped inductors or capacitors and, subsequently, has the advantages of excellent design accuracy even at high frequencies. In comparison with conventional hybrid couplers, this coupler offers lower insertion loss, higher compactness (a significant 65% reduction of the circuit area) and additional degrees of freedom by the inclusion of the shunt thin film microstrip stubs. These stubs are the sole reason for the major reduction in size.

44.5 GHz MMIC direct I&Q modulator in coplanar waveguide technology for an EHF Satcom terminal phased array

A MMIC (monolithic microwave integrated circuit) 44.5-GHz direct I&Q modulator has been developed for implementation in a low-cost EHF SATCOM terminal phased array. In this paper, the performance of the MMIC modulator is reported and the integration aspects are discussed. The K-band even-harmonic quadrature modulator conversion loss was measured to be less than 10 dB, sideband suppression better than 28 dB, carrier (2f/sub LO/) suppression around 15 dB, and IM3 (2f/sub LO/-3f/sub IF/) suppression better than 38 dB over the 43.5 to 45.5 GHz frequency band of interest.

A novel uniplanar 44 GHz MMIC subharmonic mixer using CPW series stubs

The design of a subharmonically pumped (SHP), monolithic microwave integrated circuit (MMIC) mixer for Satcom applications is described. The mixer uses an anti-parallel diode pair to achieve frequency translation by mixing the IF signal with the second harmonic of the fundamental local oscillator (LO) pump. The circuit was fabricated using OMMICs ED02AH foundry process and contains two pairs of 0.18 /spl mu/m PHEMT based diodes, each, having two 15-/spl mu/m cathode fingers. The measured conversion loss is 8 dB for an RF output signal of 44.51 GHz and the RF port return loss is better than 13 dB over the RF frequency range (43.5 to 45.5 GHz). The 2*f/sub LO/ suppression is better than 17 dB over the RF range of 43.5 to 45.5 GHz.

3D MMIC compact semi-lumped loaded CPW stubs for spurious suppression fabricated with a standard air bridge process

Compact and harmonic suppression semi-lumped stubs based on a CPW/thin film microstrip combination using 3D on-chip air-core solenoid and elevated symmetric inductors are proposed. The stubs are implemented using an MMIC airbridge process to realize an elevated transmission line and 3D inductors. These 3D inductors are used to load open circuit CPW/TFMS stubs in order to reduce their sizes. In addition to size reduction, an excellent suppression of spurious harmonic responses are achieved with improved dielectric loss which are inherent in these types of semi-lumped stubs. The experimental results presented in this paper demonstrate the validity of the design method.

DC-to-50 GHz compensation structure for flip-chip assembled SPST MEMS switch

A new structure is proposed which simply compensates the flip-chip mounting effect. As an example which shows the mounting effect and the validity of the compensation structure, a discrete RF MEMS SPST switch is used. The degraded frequency response of the RF MEMS SPST switch when it is flipped into a coplanar transmission line is successfully recovered simply by adding the proposed compensation structure. It consists of inserting the proper sizes of CPW series stubs. Whereas conventional wire bonding of discrete MEMS switches in MIC circuits prevents the realization of very low loss characteristics of the switch, models of a flip-chipped MEMS switch show it is possible to retain the low loss characteristics by using some of the novel characteristics of coplanar transmission lines. The principle of achieving such high-quality compensation structure is detailed and is also confirmed by experimental results up to at least 50 GHz. It is shown that a return loss better than 18dB in the frequency range up to 50 GHz is achievable. Finally, applying this simple compensation structure, the frequency range of operation can be further extended.

DC to 70 GHz 90 nm 3D CMOS SPDT using elevated CPW and CPS series stubs

This paper proposes a new approach for realizing a compact SPDT switch incorporating compact, elevated coplanar waveguide (ECPW) series stubs in conjunction with CPS series stubs in order to extend the operating frequency. The design technique has been successfully demonstrated using a multi-layer 90nm CMOS process. The proposed SPDT switch takes advantage of the multi-level metallization processes offered in CMOS technology. The intrinsic area of the fabricated 3D SPDT switch is significantly reduced. Simulated and experimental results are presented in support of the novel compact switch. The switch achieves a measured insertion loss of less than 3.8 dB and a measured isolation of better than 18 dB from DC to 70 GHz.