Koen Mouthaan

Millimeter-Wave Bandpass Filters by Standard 0.18-

Millimeter-wave (mm-wave) bandpass filters are presented using the standard 0.18-mum CMOS process. Without any postprocessing steps, thin film microstrip (TFMS) structure is properly constructed on the low-resistivity silicon substrate, aiming at reducing the substrate loss and crosstalk to a large extent. Using the broadside-coupled scheme, a tight coupling is achieved so as to make up a class of low-loss and broadband TFMS bandpass filters in the mm-wave range. To achieve a small size, one-stage and two-stage filters with sinuous-shaped resonators are designed and fabricated. A good agreement between the predicted and measured results has been observed up to 110 GHz

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This paper investigates the design and implementation of millimeter-wave narrow-bandpass filters in a standard 0.18- m CMOS technology. Filters with a measured 10% 3-dB bandwidth at 60 and 77 GHz are realized in a thin-film microstrip structure by using the lowest metallization layer as a ground plane. The impact of dissipation losses of the filters is also examined. It is found that the metallization losses in the coupled-line filter as well as the ground plane are the main reasons for the insertion loss.

CMOS Technology

This paper presents the theory and a design method for distributed digital phase shifters, where both the phase-error bandwidth and the return-loss bandwidth are considered simultaneously. The proposed topology of each phase bit consists of a transmission-line (TL) branch and a bandpass filter (BPF) branch. The BPF branch uses grounded shunt λ/4 stubs to achieve phase alignment with the insertion phase of the TL branch. By increasing the number of transmission poles of the BPF branch, the return-loss bandwidth can be increased. Analysis of the BPF topology with one, two, and three transmission poles is provided. The design parameters for 22.5° , 45° , 90° , and 180° are provided for bandwidths of 30%, 50%, 67%, and 100%. The relations between phase error, return loss, and maximum achievable phase shift are shown for the three topologies for design purposes. The methodology is also applicable to bandwidths larger than 100%. To validate the method, four separate L-band phase bits (1-2 GHz) are designed and measured. A complete 4-bit phase shifter with single-pole double-throw switches is then designed and measured. The measured rms phase error of the phase shifter is less than 3.6 °, while the return loss is larger than 15 dB from 1.06 to 1.95 GHz for all 16 phase states.

Design of 60- and 77-GHz Narrow-Bandpass Filters in CMOS Technology

A wideband LC voltage-controlled oscillator (VCO) design with a new varactorless frequency-tuning technique is presented. The wideband continuous frequency tuning is achieved using a tunable negative-inductance cell. Fabricated in a 0.35-μm SiGe BiCMOS process, the varactorless VCO achieves a continuous tuning range of 24.5%. An overall tuning range of 31% from 3.8 to 5.2 GHz is achieved when the continuous tuning is combined with a 2-bit switched capacitor array. The measured phase noise is - 109.8 and - 109.5 dBc/Hz at 1-MHz offset from a 3.8- and a 5.2-GHz carrier frequency. The proposed VCO has demonstrated performance that is better than other wideband varactorless VCOs in the literature.

Phase-Shifter Design Using Phase-Slope Alignment With Grounded Shunt

In modern CMOS technologies, metal dummy fills are required to maintain metal density uniformity and to planarize the layers. As frequency increases, the effect of the metal dummy fills on the CMOS integrated circuits or components should be taken into account. This work presents experimental results of the effect of metal dummy fills on the microwave behavior of spiral inductors fabricated in a standard 0.18-mum CMOS technology. The influences on the equivalent model parameters and the Q-factor are characterized based on measured S-parameters of inductors with and without metal dummy fills.

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A fully scalable and SPICE compatible wideband model of on-chip interconnects valid up to 110 GHz is presented in this paper. The series branches of the proposed multisegment model consist of an RL ladder network to capture the skin and proximity effects, as well as the substrate skin effect. Their values are obtained from a technique based on a modified effective loop inductance approach and complex image method. A CG network is used in the shunt branches of the model, which accounts for capacitive coupling through the oxide and substrate loss due to the electrical field, as well as the impact of dummy metal fills. The values of these elements are determined by analytical and semiempirical formulas. The model is validated by a full-wave electromagnetic field solver, as well as measurements. The simulated S-parameters of the model agree well with the measured S-parameters of on-chip interconnects with different widths and lengths over a wide frequency range from dc up to 110 GHz.

Stubs

This paper analyzes the two-way Wilkinson power dividers using coupled lines as λ/4 impedance transformer to have more compact layout. The analysis shows that the input port matching is only influenced by the even mode impedance of the coupled lines. Once the even mode impedance is fixed, all other specifications of the power divider are determined by the odd mode impedance of the coupled lines. Design tradeoffs among the output matching, isolation and the odd mode impedance are shown. By using smaller odd mode impedance, layout constraint can be relaxed. To validate the analysis, Wilkinson power dividers using coupled lines with areas of 1.5 cm2 and 1.25 cm2 are designed together with a conventional divider with an area of 3.8 cm2. The experimental results of the three designs are comparable. When coupled lines are used, the layout is more compact with a reduction in size of more than 50% compared to the conventional design.

Wideband Varactorless

A tunable decoupling and matching network (DMN) for a two-element closely spaced antenna array is presented. The DMN achieves perfect matching for the eigenmodes of the array and thus simultaneously isolates and matches the system ports while keeping the circuit small. Arrays of closely spaced wire and microstrip monopole pairs are used to demonstrate the proposed DMN. It is found that monopoles with different lengths can be used for the design frequency by using this DMN, which increases the design flexibility. This property also enables frequency tuning using the DMN only without having to change the length of the antennas. The proposed DMN uses only one varactor to achieve a tuning range of 18.8% with both return loss and isolation better than 10 dB when the spacing between the antennas is 0.05 λ. When the spacing increases to 0.1 λ, and the antennas are properly matched, the simulated tuning range is more than 60%.

LC

A new method for octave-band phase-shifter design based on high-pass, low-pass, bandpass, and all-pass networks (APNs) using discrete components is presented. First, the general synthesis method is provided to find the optimum return loss and phase error of a high-pass/low-pass phase shifter. It is also shown that the conventional design method is a special case of the method presented here. The proposed method facilitates tradeoffs between the bandwidth, phase error, and return loss, which is not possible in the conventional method. Phase bits of 22.5^°, 45 ^°, and 90 ^° are designed using this method. For the phase bit of 180^° , a new topology using a third-order bandpass network and an APN is proposed. The phase error is reduced from 25 ^° to 7.4 ^° and the return loss is improved from 5 to 22 dB over the whole octave band compared to the conventional method. For the cascaded 4-bit phase shifter, the return loss is improved from 5 to 19 dB and the rms phase error is reduced from 13.5 ^° to 4.3 ^° in theory. The experimental results of the 4-bit phase shifter show an rms phase error of 5.9^° and a return loss of 13 dB from 530 to 1090 MHz. The maximum amplitude imbalance is 0.6 dB for all 16 phase states.

VCO Using a Tunable Negative-Inductance Cell

Using the complex image method (CIM), we have analyzed the frequency and temperature dependencies of substrate eddy currents for single-ended and differential spiral inductors on a lossy silicon substrate. From our analysis, we have derived a set of accurate closed-form expressions for calculating inductances and substrate losses due to substrate eddy currents. Here, we propose a frequency-dependent eleven-element equivalent circuit model based on these formulas. We established the validity of the model by comparing the simulated and measured results, which are in good agreement.