It is hereby approved that this is the thesis in partial satisfaction of the requirements for degree of. Fig.3.12 The simulated and the measured results of the improved circuit with one-layer connected lines (a) and six-layer connected lines (b). Thus, a two-stage bandpass filter with both small size and automatic matching is more desirable.
In this structure, the ground plane is encapsulated around the filter, which avoids coupling with other basic components in the transmitter system. In addition, as another major advantage, it proved to have an automatic resistance match. The largest difference between simulation and measurement in CMOS fabrication is also analyzed and will be proven to be caused by transmission losses and quality factors in the lossy distributed inductor of the shunt resonator.
The method for improving the performance of the bandpass filters and automatically adjusting the impedance will be described. A lot of simulated and measured data are collected and provided here to show the advantages of the proposed bandpass filter.
Introduction
An introduction to the filters at present
Slow wave resonator filter [4], [5] is another effective approach to reduce the size of the bandpass filter by making use of the slow wave effect in periodic structures. Ohmic loss is inevitable as the primary inductor current flows through the thin metals of the coil. It has been reported that system performance using the silicon-on-insulator (SOI) process (where inductors with quality factors Q > .20 can be achieved) was comparable to a conventional low-noise amplifier with an off-chip bandpass filter [ 18 ].
However, it is not common for a single-chip transceiver to include an integrated bandpass filter. Despite the small silicon area and good insertion loss of the active filters, the active circuit has the disadvantage of having nonlinear and poor noise characteristics and consuming DC power. In this thesis, a new bandpass filter was designed using a diagonally shorted line with a loaded lumped capacitor for size reduction.
An additional ground plane is inserted below the signal line between the two multilayer filters to improve the filter efficiency. It will be demonstrated theoretically that center frequency shifts cause transmission losses and quality factors in an inductor with distributed displacement resonator losses.
Organization of the thesis
A ground plane on metal in BPF with the standard multi-layer metal CMOS technology was used to address this frequency shift, thereby reducing the electric field leakage into the silicon substrate[22]. The larger difference between the simulation and measurement in CMOS fabrication has not been analyzed until now. The simulation result confirmed that the filter with ground level below the intermediate stage line has a better performance than the one without ground level.
These approaches will be verified by measuring BPFs with two types of quality factors.
The Bandpass Filter Design Theory
Size reduction method
To reach very small electrical length up to several degrees, the coupled line component was used. Since it is easy to get a high impedance by choosing the even-mode impedance that matches the odd-mode impedance. So the equivalent circuit is the shortened quarter-wave transmission line using Hirota's method as mentioned above.
The structure of the diagonally miniaturized coupled lines with lumped capacitors appears as shown in Fig 2.5.
The two-stage filter
In addition, two phase filters are always matched at the input and output port, regardless of any fabrication error if the two filters have the same characteristic. As shown in equation (2.10), the input impedance of the two-stage filter Zin is equal to Z0, that is, the two-stage filter is automatically matched.
The inter-stage signal line enhancement method
The Simulation , fabrication and results analysis
The inter-stage signal line improvement
A multi-layer circuit is built on a substrate with ground posts arranged on either side of the coupled line to prevent coupling to other components. The oxide is used as an insulator inserted into the structure to prevent current from flowing downwards. Floor pillars are arranged on both sides of the connecting line, so that coupling can be effectively avoided.
If an additional ground plane is inserted below the line, the coupling will drop further and the filter performance should therefore be better theoretically.
Simulation and fabrication
The coupled line width is 20 μm, the transmission line length is 570 μm and the separation between the two coupled lines of 140 μm is used to provide input/output impedance matching with the system impedance Z0 = 50 Ω. The thickness of the signal line is 2.34um, and the thickness of the extra ground plane inserted under the signal line is 1.91um. 3.5 (a) the connection part of the original filter is only the transmission line and in Fig.3.5 (b) the line is covered by ground plane.
Before describing the result of the filters, we compare the two connection structures to gain some insight into the new design. The waveguides become lossy due to the parasitic coupling between the signal line and the substrate. After inserting an additional ground plane shielding the signal line, the electric field penetration through the substrate is completely eliminated as shown in fig.
The simulated results of the circuit with one-layer and six-layer connected lines are drawn in two figures, respectively. 3.8 (a), with 1 layer, the result of the original circuit without extra ground plane is distorted at 4.3 GHz due to the severe coupling while the improved one with extra ground plane has a normal bandpass filter shape. This is an improvement of 1.79dB compared to the original one, which has an insertion loss of -5.92 at resonance.
3.8(b), the result of the original circuit without additional ground plane is distorted at 4.2 GHz, while the improved circuit with additional ground plane has a normal bandpass filter shape. The insertion loss of the innovative 6-layer filter is -2.3 dB at the resonant frequency, while the original filter has an insertion loss of -5.67 at resonance. The circuit without additional ground plane was distorted at 4.7 GHz due to the severe coupling, while the approved circuit with additional ground plane had a normal bandpass filter shape.
Apparently, the improved BPF with additional ground area under the bond line has advantages over the typical BPF with both 1 layer and 6 layers.
The quality factor effect on the resonance frequency shift
Equation (3.1) shows that the resonant frequency wr is equal to the center frequency w0 as expected, and that the corresponding Q-factor is infinite. However, the loss effect of the substrate is actually too severe to ignore since the silicon substrate is inherently lossy and the electric field. Although the exact equivalent circuit of the distributed inductor is complicated, we assume that the inductor loss is mainly due to the series resistance R2, as shown in Figure 2.
3.10 (a), the equivalent circuit of the resonator, since the resistance Rp1, Rp2 of the parallel part does not change the resonant frequency of the shunt resonance. For the MIM capacitor, there is an equivalent series resistance R1 in the MIM circuit model and a maximum Q of about 80 has been reported [28]. The corresponding operating resonant frequency wrin of equation (3.5) will be less than the center frequency w0 of the lossless circuit.
3.12, the simulated and measured results of the improved filter with one-layer and six-layer coupled lines are plotted. The QL factors for the BPF were found to be 4.9 and 14.8 for the one-layer and six-layer filters, respectively. The QL factor of the six-layer BPF circuit was better than that of the one-layer circuit.
The measured center frequency of the lines coupled with a BPF layer shifted from 5.5 GHz to 4.7 GHz with 0.8 GHz shift as shown in Fig.
Conclusion
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Jenkins, "Microwave inductors and capacitors in standard multilevel interconnect silicon technology", IEEE Microwave Theory and Technologies, vol. I would like to acknowledge many people who have helped me in both my studies and daily life during the past two years. I would also like to express my appreciation to the other professors of our department for their support and guidance, which Prof.
Thank you for your support and guidance on my paper and their help over the past two years. I would also like to thank the members of the other laboratory of our department for helping me in my academic life. Special sincere thanks to former member of RF Circuit & System Lab, Mr.
