Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2001-01-24
2003-05-27
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000
Reexamination Certificate
active
06571372
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for measuring and designing an electric circuit and a computer-readable recording medium for recording the same. In particular, the present invention relates to a method and an apparatus for measuring an electric circuit such as an oscillator circuit, an amplifier circuit or the like based on S-parameters of a 2-port network thereof, a method and an apparatus for designing the electric circuit, a computer-readable recording medium recording a method of measuring the electric circuit, and a computer-readable recording medium for recording a method of designing the electric circuit.
2. Description of the Related Art
Oscillators in RF (Radio Frequency) and microwave frequencies remain to be rather mysterious circuit blocks, that is, their behaviors are not fully explained yet. In order to analyze a microwave oscillator, an approach of calculating oscillation parameters by introducing a virtual ground into an equivalent circuit of the microwave oscillator has been heretofore proposed (for exmaple, a prior art document 1, Stanilaw Alechno, “Analysis Method Characteristics Microwave Oscillators, Oscillator Analysis, Part 1”, Microwave & RF, November 1997; a prior art document 2, Stanilaw Alechno, “Analysis Method Characteristics Microwave Oscillators, Oscillator Analysis, Part 2”, Microwave & RP, December 1997; a prior art document 3, Stanilaw Alechno, “Analysis Method Characteristics Microwave Oscillators, Oscillator Analysis, Part 3”, Microwave & RF, January 1998; and a prior art document 4, Stanilaw Alechno, “Analysis Method Characteristics Microwave Oscillators, Oscillator Analysis, Part 4”, Microwave & RF, February 1998).
However, in particular, designing a wide-tuning voltage-controlled oscillator (hereinafter, a voltage-controlled oscillator is referred to as a VCO) still involves a lot of guesses, many printed-circuit board tunes, even with the help of today's highly sophisticated design tools. One problem in the designing process lies in the absence of analysis method that gives full insights into oscillation phenomenon represented in an easy-to-understand format.
Traditionally, all oscillators are classified into either a negative resistance oscillator (also known as a reflection oscillator) or a feedback oscillator. The criterion is whether or not there is an “obvious” feedback circuit. In RF and microwave frequencies, it becomes difficult to construct a feedback circuit without introducing excess phase shift. Therefore, almost all oscillators in the frequency range are classified as a negative resistance oscillator.
FIG. 1A
is a circuit diagram showing a circuit of a negative resistance oscillator of the prior art, and
FIG. 1B
is a circuit diagram showing a reflection analysis model circuit, showing a method of analyzing the negative resistance oscillator.
As shown in
FIG. 1B
, the negative resistance oscillator is represented as a combination of an active element part
10
and a resonator part
20
of a passive element. For example, an active element of a transistor TR generates a negative resistance, and drives a passive element, which is usually a resonator RE. Simply speaking, when the negative resistance beats all losses in the resonator RE and the active element, oscillation builds up. Oscillation conditions for reflection analysis shown in
FIG. 1B
are expressed by the following Equations (1) and (2):
|&Ggr;
A
·&Ggr;
B
|≧1 (1);
and
arg
(&Ggr;
A
)=−
arg
(&Ggr;
B
) (2),
where &Ggr;
A
denotes a reflection coefficient of a port P
11
when viewing the active element part
10
from the port P
11
, &Ggr;
B
denotes a reflection coefficient of a port P
12
when viewing the resonator part
20
from the port P
12
, and arg(·) denotes a phase or an angle of deviation of an argument thereof.
In the prior art, negative resistance analysis is so common, yet there are many questions in controversy as to the validity of this analysis. Also there are some oscillation parameters, like a loaded-Q, that cannot be derived from this analysis. The loaded-Q is one of the fundamental yet most important parameters because it dictates spectral purity (indicating how low phase noise is). Missing loaded-Q information when analyzing an oscillator prevents designers from a full understanding of their own design. In other words, there is such a problem that there is not yet any method of analyzing an RF circuit and a microwave circuit in a complete form.
SUMMARY OF THE INVENTION
It is an essential object of the present invention to overcome the foregoing problems, and also to provide a method and an apparatus for measuring an electric circuit, capable of measuring circuit parameters by analyzing an electric circuit such as an RF circuit, a microwave circuit or the like in a complete form using a method simpler than that of the prior art.
It is another object of the present invention to provide a method and an apparatus for designing an electric circuit, capable of designing circuit parameters by analyzing an electric circuit such as an RF circuit, a microwave circuit or the like in a complete form using a method simpler than that of the prior art.
It is a still further object of the present invention to provide a computer-readable recording medium for recording a program for measuring an electric circuit or a method of designing an electric circuit, capable of measuring or designing circuit parameters by analyzing an electric circuit such as an RF circuit, a microwave circuit or the like in a complete form using a method simpler than that of the prior art.
According to one aspect of the present invention, there is provided a method of measuring an electric circuit including the steps of:
entering an equivalent circuit of the electric circuit, the equivalent circuit comprising a plurality of elements respectively having element values thereof;
specifying a break point and a virtual ground in the entered equivalent circuit, the break point being for disconnecting an electric path for forming a closed-loop circuit;
generating a 2-port network by disconnecting the electric path at the specified break point in the entered equivalent circuit so as to form first and second terminals that are two ends of the electric path, the 2-port network having a first port comprising the first terminal and the specified virtual ground, and having a second port comprising the second terminal and the specified virtual ground;
calculating S-parameters of the generated 2-port network; and
calculating an open-loop transfer function of the electric circuit in accordance with the calculated S-parameters.
The above-mentioned method preferably further includes the step of calculating characteristic parameters of the electric circuit in accordance with the calculated open-loop transfer function.
Also, the above-mentioned method preferably further includes the steps of:
entering other element value of at least one of the plurality of elements of the entered equivalent circuit; and
repeatedly executing the step of specifying, the step of generating and the two steps of calculating for the equivalent circuit of the electric circuit containing the other element value.
Further, the above-mentioned method preferably further includes the steps of:
entering other element value of at least one of the plurality of elements of the entered equivalent circuit; and
repeatedly executing the step of specifying, the step of generating and the three steps of calculating for the equivalent circuit of the electric circuit containing the other element value.
In the above-mentioned method, the electric circuit is preferably an oscillator, and the characteristic parameters are at least one of an oscillation frequency, a gain margin, a phase margin and a loaded-Q.
In the above-mentioned method, the electric circuit is preferably an amplifier circuit, and the characteristic parameters are at least one of a maximum gain within a 3-dB bandwidth, the 3-dB bandwidth and a stabili
Agilent Technologie,s Inc.
Lin Sun James
Smith Matthew
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