Flip-chip technology and new microwave filters on coplanar strip lines

Traditionally, dominating transmission line is microstrip line on microwave and millimeter-wave integrated circuits (MMICs) and on print circuit boards (PCBs). The coplanar strip (CPS) line has both the signal and ground electrodes on the front surface of the board. In contrast to the microstrip line, the CPS line does not include the backside of the board as a part of the transmission line. Thus, the backside can be left open as dielectric or metallized. The backside condition can affect the wave propagation if it is too close to the electrodes. Analysis and characterization of CPS lines depending on backside condition were performed at millimeter-wave frequency up to 40GHz. The CPS line was analyzed and simulated using full-wave electromagnetic simulation. Many CPS lines were built on RT/Duroid board and the measured attenuation is as low as 0.8dB/cm at 30GHz. CPS lines of various electrode width and width-to-gap ratios were measured to obtain key design guidelines. The results clearly indicate that the CPS line is an attractive transmission line on the board level in millimeter electromagnetic waves applications. Its applications can be extended to microwave and millimeter-wave applications.;With those preliminary investigations and advantages of CPS line, a new flip-chip interconnect configuration with CPS lines on PCBs was first developed for millimeter-wave applications. The flip-chip configuration was designed and implemented using a test chip on dielectric board. Geometrical parameter analysis was carried out using full-wave simulation and equivalent circuit model for wideband performance. The chip was connected to the board using solder bumps. For a typical flip-chip assembly, the measured insertion loss is less than 3dB for frequencies up to 35GHz and the return loss is higher than 15dB for frequencies close to 30GHz using CPS flip-chip configuration.;A novel compact bandpass filter in coplanar strip (CPS) lines for RF and microwave applications was newly developed and implemented. The filter is implemented as electrode topology on the CPS electrodes. The topology consists of basic electrode patterns that emulate inductors and capacitors in a two-port filter section. It uses the creation of an electrode pattern on the coplanar strip electrodes to emulate an equivalent circuit. Bandpass filters for 2.4GHz ISM (Industrial, Scientific and Medical) and 5.15–5.85GHz UNII (Unlicensed National Information Infrastructure) bands were designed, fabricated, and measured. The electrode pattern can be scaled for different center frequency and improved with fine tuning procedure. The concept of hybrid topology that gives resonance response was newly introduced. The compactness of bandpass filter in CPS line was realized with large effective capacitance of hybrid topology, which is useful for the technologies in the millimeter wave frequency range. The bandpass filter is very compact in size and planar in structure. It does not use quarter-wavelength sections, vias, or bonding wires. It can be fabricated without incurring additional cost.