Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
1999-09-16
2003-10-21
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
Reexamination Certificate
active
06637008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic circuit provided with a plurality of circuit elements performing a specified basic function and its adjusting method, including an analog filter circuit and its adjusting method, a high-frequency circuit and its adjusting method, and an integrated circuit and its adjusting method. The present invention can be effectively applied to an electronic circuit in which analog values such as the amplitude, phase, frequency of a signal are important.
2. Related Art
Previously, (1) effort in a circuit design, (2) adjustment of adjusting points provided on an electronic circuit, (3) effort to reduce errors in production of a semiconductor integrated circuit and (4) selection of manufactured electronic circuits have been used as methods for improving the accuracy attained by an electronic circuit in producing a target value.
However, method (1), making an effort in a circuit design, needs to be repeated until a good result can be obtained. The design process is repeated until variation in the function of an electronic circuit caused by variation in characteristics of elements forming the electronic circuit becomes as insensitive as possible. In the case that a target function has a high energy content, it is necessary to exactly grasp such parameters as transfer characteristics of the circuit elements and when it is difficult to do so, it is technically difficult to design such a circuit.
Moreover, since there is also the method of item (2), adjusting points are provided on an electronic circuit. Usually, the number of adjusting points is made as small as possible during of design. In case the number of adjusting points becomes large, an effort in a circuit design is made so that adjustment results are independent of one another, as shown in FIG.
2
(
a
). But when performing such a circuit design that makes it possible to obtain adjustment results independent of one another this method has an advantage of making adjustment easy. But, on the other hand, it requires a special circuit design to obtain its adjustment results. Additionally, the circuit design becomes complicated and needs to adopt a number of high-accuracy elements. For example, adding a trimmer capacitor TC at a point of a signal source impedance Z where a signal s appears, it is possible to adjust the phase delay quantity of the signal s but at the same time as this adjustment occurs, the amplitude of this signal is also changing. In order to change only the phase and not to change the amplitude, it is necessary to add a circuit for compensating for the amplitude change or to use a separate complicated phase delay adjustment circuit.
A circuit to make only a single parameter variable as described above, or a circuit to perform compensation so as to make only a single parameter variable is here referred to as an “equalizing circuit”. An equalizing circuit needs a greater number of circuit elements in comparison with a simple circuit and often needs more accurate elements.
Therefore, the prior method is expensive in design cost and long in design time. And it is sometimes necessary to adopt expensive elements that are highly redefined in an electronic circuit when designing the circuit.
Further, when adjusting the adjusting points of item (2), the effects which adjustment points have on circuit characteristics are not independent of one another as shown in FIG.
2
(
b
). When the design is simple, a small number of elements can do and high-accuracy elements are not necessary. However, it is still necessary to divide an electronic circuit into very small parts and adjust operation of the electronic circuit individually. With these small parts, the adjustment is very complicated and when individual measurements cannot be performed, the adjustment is very difficult.
Sometimes, when a plurality of adjusting points, as described above, cannot be adjusted independently of one another, the size of an adjustment range has the same number of dimensions as the number of adjusting points linked with one another, the adjusting and search space expands in proportion to the number of adjusting points at an exponential rate. The adjustment then requires an impractical time or becomes impossible. Considering as an example, a case in which there are ten adjusting points to be adjusted by a setting signal of 8 bits and all of them are linked to one another. The search space for adjustment has an enormous number of combinations of “2{circumflex over ( )}80≈10{circumflex over ( )}24”, and it has been impossible using the prior methods to perform adjustment in a practical time.
Additionally, a pre-set resistor or trimmer capacitor used at an adjusting point can be made large in size so that it can be operated by an adjusting bar or the like in order to adjust a parameter by a mechanical means. Such a method has a disadvantage that it is expensive to adjust. Furthermore, an alternate adjustment method using a laser trimming operation gives a physically unrestorable change to the adjusting point. Thereafter, once the circuit fails in adjustment the electronic circuit cannot adjusted.
Last, the method of making errors in production small in item (3) is problematic in that there is limitation in processing accuracy of a semiconductor material. A high-accuracy process is expensive.
And the method of selecting electronic circuits in item (3) has a problem, since an electronic circuit whose function does not meet the specified target value is treated as a defective product and is generally discarded, the electronic circuit manufacturing process can be very low in its yield rate and becomes remarkably uneconomical.
Furthermore, considering individual circuits, an analog filter circuit (filter circuit) performs a process of removing a specific frequency-band signal component of an input signal or a process of taking out only a specific frequency-band signal component (filtering process). In the case of mass production it sometimes occurs that individual filter circuits vary greatly in filter characteristics due to irregularities in material and manufacturing errors. Then a desired signal component and an unnecessary signal component (a frequency component out of the passing band of a filter circuit) are sometimes not completely separated. Filter circuits have been made into an LSI (large scale integrated circuit) in recent years. Since such an LSI filter circuit cannot replace individual components, an LSI filter circuit whose filter characteristics are not within an acceptable range is treated as a defective product and discarded.
A mixer circuit sometimes outputs unnecessary signal components (image frequency components, local oscillation frequency components, harmonic components of a total frequency or a differential frequency of the mixer circuit) due to variation in characteristics of circuit elements.
Since a high-frequency circuit handles a signal having high-frequency components (radio frequency components of 100 kHz or higher in general), it has a problem of parasitic inductance and parasitic capacitance. Furthermore, it often needs to consider frequency dependence in transfer characteristics of a circuit elements, and scattering and reflection of a signal at a characteristic impedance discontinuity point. Therefore, it has typically required a long time for design and manufacture, and has been high in development cost and manufacturing cost.
A high-frequency integrated circuit is a circuit obtained by integrating a high-frequency circuit conventionally composed of discrete components into an LSI by means of a semiconductor integrated circuit technology. In order to attain a specified performance in this integrated circuit, it is necessary to perform impedance matching and accurately set the parameters of individual electronic circuits contained in the integrated circuit to specific values. In order to do so, it is necessary to know accurate parameter values of circuit elements and exactly manage its manufacturing process, and therefore a high
Adachi Toshio
Higuchi Tetsuya
Kasai Yuji
Kiryu Shogo
Murakawa Masahiro
Agency of Industrial Science and Technology
Do Thuan
LandOfFree
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