Yi-Chieh Lin

Vertical interconnect measurement techniques based on double-sided probing system and short-open-load-reciprocal calibration

This work develops a double-sided probing system and calibration method for measuring the S-parameters of vertical interconnects at the wafer, package and socket level. The applicable device under test (DUTs) include through silicon vias (TSVs), plated through holes (PTHs), pogo pins and pressure sensitive conductive rubbers (PCRs). The effects of solder bumps and balls can also be taken into account. A short-open-load-reciprocal (SOLR) calibration method is used with a reciprocal thru to instead of the conventional short-open-load-thru (SOLT) which uses a standard thru. The S-parameters can be measured up to 40 GHz with a repeatable S21 parameter accuracy of better than 0.2 dB and 1 degree in magnitude and phase, respectively. Additionally, the eye diagrams are measured at a maximum data rate of 40 Gb/s and a minimum rise time of 10 ps with the help of Agilent physical layer test system (PLTS).

Synthesizing a Multiband LTCC Bandpass Filter With Specified Transmission- and Reflection-Zero Frequencies

This paper presents a vertically expandable low-temperature cofired ceramic (LTCC) bandpass filter (BPF) structure to increase the number of operating bands of the BPF without changing the area of the footprint. To design efficiently the proposed LTCC BPFs with highly configurable passbands and stopbands, a new method of synthesizing multiband BPF prototypes with specified transmission- and reflection-zero frequencies is developed. A dual-band BPF and a triple-band BPF were designed and implemented in LTCC. Both BPFs have the same area of 1.25×2.0 mm2. Comparisons of the S-parameters among the synthesized prototypes, postlayout simulations and measurements exhibit a strong correlation.

Kahn envelope elimination and restoration technique using injection-locked oscillators

The envelope elimination and restoration (EER) technique, which was proposed by Kahn, is a recognized means of highly-efficient linear amplification. This paper presents a novel EER transmitter using injection-locked oscillators (ILOs). In the proposed architecture, an ILO that is combined with a mixer and a low-pass filter extracts an envelope signal and a phase-modulated RF signal from an RF input signal with time-varying envelope modulation. Then, the phase-modulated RF signal is efficiently amplified by a Class-E power amplifier (PA) and the envelope signal is restored at the PA output by modulating the supply voltage of the PA. The constructed prototype of the EER transmitter achieves a 21 dB power gain and a 36% power-added efficiency at an average output power of 23 dBm for Enhanced Data rates for GSM Evolution (EDGE) signals, meeting the spectral mask specifications without using any pre-distortion techniques.

A MIMO antenna with built-in isolation for WLAN USB dongle applications

A novel couple-fed dual-bands MIMO antenna is proposed for WLAN 2.4/5.2/5.8 GHz bands. The MIMO antenna system consists of two parallel folded branch monopoles with an edge-to-edge separation of 0.2 mm. The antenna elements are printed on an FR4 substrate and are located at the top edge of the ground plane. Size of the antenna is 20 mm (W) × 11 mm (L). The isolation is achieved by introducing a round off-set structure at the end of the coupled feeding-line. Measured results show that antennas have good impedance matching and port isolation. Since we have not introduced any isolation enhancing structure, the MIMO antenna appeared to have a built-in decoupling mechanism. When one end was fed, the current distributions on the other feed line was reduced in magnitude by a self generated counter current occur at the round off-set structure area. That is, the self generated counter current has contributed the needed isolation between the two antennas. The results suggest that the proposed novel simple, compact antenna structure has indeed attained good isolation characteristics required for MIMO operations. Moreover, the antenna is easy to fabricate and suitable for applications at the 2.4/5.2/5.8-GHz bands.

Low cost QFN package design for millimeter-wave applications

This paper focuses on the design and development of a low-cost QFN package that is based on wirebond interconnects. One of the design goals is to extend the frequency at which the package can be used to 40-50 GHz (above the K band), in the millimeter-wave range. Owing to the use of mass production assembly protocols and materials, such as commercially available QFN in a mold compound, the design that is outlined in this paper significantly reduces the cost of assembly of millimeter wave modules. To operate the package at 50 GHz or a higher frequency, several key design features are proposed. They include the use of through vias (backside vias) and ground bondwires to provide ground return currents. This paper also provides rigorous validation steps that we took to obtain the key high frequency characteristics. Since a molding compound is used in conventional QFN packages, the material and its effectiveness in determining the signal propagation have to be incorporated in the overall design. However, the mold compound creates some extra challenges in the de-embedding task. For example, the mold compound must be removed to expose the probing pads so the effect of the microstrip on the GaAs chip can be obtained and de-embedded. Careful simulation and experimental validation reveal that the proposed QFN design achieves a return loss of -10 dB and an insertion loss of -1.5 dB up to 50 GHz.

Full Chip-Package-Board Co-Design of Broadband QFN Bonding Transition Using Backside via and Defected Ground Structure

A complete chip-package-board co-design of bonding transition for a quad flat pack nonlead (QFN) package was conducted from dc to millimeter wave frequencies. First, two ground paths in parallel were used to improve the operating frequency of the commercially available QFN to 50 GHz. Owing to its rectangular cross section, ribbon bond has a better form factor than the corresponding round wire bond with the same dc resistance; it is therefore more effective in impedance matching, and can carry more current at high frequencies. Ribbon bonds were utilized to improve incrementally the frequency performance. Applying the -1.5-dB rule for |S21| and the -10-dB rule for |S11|, improvements are found to be 1.7 and 3.2 GHz, respectively. Second, QFN frequency performance was significantly improved by using an embedded DGS on the PCB. At 50 GHz, the transition was found to be excessively capacitive. A high-impedance DGS, being inductive itself, was used to compensate for the capacitive nature of the transition. The lumped element approach was taken to provide the background rationale how a DGS on the PCB ground can be adequately used to reduce the capacitive nature of the transition around 50 GHz. Indeed, from simulation at 50 GHz, utilizing the DGS helped to improve the impedance matching, and reduce the insertion loss, further extending the range of operating frequencies. Later, a full wave simulation of the DGS-compensated transition was conducted and the transition was experimentally validated. The full-wave simulated and experimentally obtained results are in good match. From measurements, when the DGS is used, the -1.5-dB rule for |S21| and the -10-dB rule for |S11| enable the QFN package to achieve the bandwidth up to 62.3 and 66 GHz, respectively.

High performance plastic molded QFN package with ribbon bonding and a defective PCB ground

An interconnect transition within the plastic mold is formed between the output ports of the IC sitting on top of a Quad Flat Non-leaded (QFN) package and the nearby I/O leads of the package. This paper describes the design and development of a cost-effective interconnect transition structure for improving the operating frequency of the package up to millimeter-wave range. In addition to adopting ribbon bonds, which have been shown to exhibit a lower insertion loss, a novel Defective Ground Structure (DGS) has been used to compensate the ribbon bonds imaginary part of impedance (the parasitic capacitive from the I/O pad), thus, achieving superior bandwidth performance. By employing the ribbon bonds and the DGS structures; the measured results of QFN package is able to achieve S21 at -1.5dB up to 62.3 GHz, and S11 less than -10 dB up to 66 GHz.

Implementation of a MIMO antenna design for USB dongle applications

A compact monopole slot MIMO antenna integrated on a 2.4 GHz WLAN module for USB dongle applications is presented. In this study, we focus on design and implementation of the MIMO antenna in a four-layered PCB with realistic system ground. To ensure a high isolation between the two closely spaced MIMO antennas on a restricted antenna area, we performed antenna miniaturization to enhance the isolation by introducing a T-shaped cut-off on the top edge of the monopole slot MIMO antenna. Adopting a slot structure for the radiating elements, a high isolation between the antennas was achieved within the specified antenna area. The details of the antenna design are described; the simulation and measurement results are presented and discussed. Moreover, throughput experiment was conducted to validate the proposed MIMO antenna design. Throughputs of 139.45 Mbps on average for receiving and 63.59 Mbps on average for transmitting were obtained for IEEE 802.11n 1T2R standards.

Highly flexible and miniaturized triple-band bandpass filter design using coupled stacked spiral resonators

This paper describes a triple-resonance stacked spiral resonator (SSR) structure for designing very compact tripleband bandpass filters. The resonant frequencies of the proposed SSR structure can be determined by designing the spiral geometry and controlling the mutual coupling in a stacked structure. The triple passband bandwidths can then be determined by the spacing of different layer patterns between two coupled SSRs. An adequately designed geometry of the input/output resonator with a tapped-line feed can achieve matching conditions for all passbands simultaneously. Moreover, multiple transmission zeros created on both sides of each passband provide high stopband roll-off rates.

Inductive link design with optimal transfer efficiency and a high CMRR

In this paper, we present two key design approaches to optimize an inductive link for contactless energy transfer. Applications of the inductive link include 1.) a wireless technique to energize implanted biomedical devices; and 2.) wireless peripheral I/Os between chips. First, a new hybrid (i.e., surface mount components on a PCB) structure, which consists of a symmetrical coils and matching capacitors for improving the power link efficiency and immunity to misalignment was designed. The maximum transfer efficiency with and without impedance matching will be analyzed and shown. Since biomedical implants often relying on inductive links for power and data transfers, the interference between them is a major concern. Therefore, as the second design approach, this study proposes a full differential signaling scheme to eliminate out of band interference and provide a high CMRR in the interested frequencies. Based on EM modeling and analysis, the simulation result yields transfer responses that are in good agreement with experimental results. According to the results, the maximum transfer efficiency is 87% at 3mm vertical distance and the CMRR is higher than 50dB. At z=12mm, or a lateral misalignment of 9 mm, it is still able to achieve an optimal energy transfer (at 48%), after impedance re-matching.