Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2001-11-05
2004-04-20
Siek, Vuthe (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000, C716S030000, C716S030000
Reexamination Certificate
active
06725430
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of high frequency circuit design, including but not limited to RF and microwave circuit design, and more specifically, to high frequency circuit designs simultaneously interchangeable into multiple domains, such as prototype and production domains.
RELATED ART
In the late 1800s, after Heinrich Hertz confirmed J. C. Maxwell's wave equations, and proved that electromagnetic energy radiates through the air in the form of long transverse waves, many new fields of endeavor were born, ranging from radio, TV and sonar, which emerged in the first half of the 20
th
century, to wireless communications, including cellular, PCS, fixed wireless, and satellite communications, which became prevalent in the latter half of the 20
th
century.
As these applications have evolved, the trend has been to utilize higher and higher operating frequencies, both because high frequencies facilitate faster and higher capacity information transmission than low frequencies, but also because high frequency transmissions are more efficient and entail smaller circuit elements than low frequency transmissions. In order to support these applications, electrical engineers and circuit designers have had to develop circuits capable of operating at the high frequencies.
This has posed significant challenges since, at high frequencies, many circuit elements, such as resistors, capacitors, and inductors, typically deviate quite a bit from their idealized behavior. Compounding this problem is that, at high frequencies, voltages and currents are no longer spatially uniform when compared to the physical size of the circuit elements, and instead must be treated as propagating waves, such as transverse electromagnetic (TEM) waves in which the electric and magnetic field components are orthogonal to each other and to the direction of propagation. Consequently, conventional circuit analysis techniques, in which circuit elements are modeled as idealized lumped elements which obey Kirchoff's circuit laws, no longer apply since they ignore the spatial variations in the voltage and current which occur at high frequencies, and do not account for the manner in which circuit elements deviate from their ideal behavior. Instead, more advanced models using transmission line and distributed elements, which account for this spatial variation in voltage and current, and which account for the frequency dependent behavior of the circuit elements, are required.
The non-ideal behavior of circuit elements at high frequencies can be illustrated with reference to
FIGS. 1A
,
2
A, and
3
A, which depict simplified, first order, high frequency models of, respectively, a resistor, capacitor and inductor, and
FIGS. 1B
,
2
B, and
3
B, which are respectively a plot of the real part of the impedance exhibited by the model of
FIGS. 1A
, the imaginary part of the admittance exhibited by the model of
FIG. 2A
divided by 2&pgr;f, and the imaginary part of the impedance exhibited by the model of
FIG. 3A
divided by 2&pgr;f, over high frequencies. (In
FIGS. 1B
,
2
B, and
3
B, both axes are assumed to be log
10
scale axes).
Referring to
FIG. 1A
, a resistor R is modeled as two inductors L in series with each other and the parallel combination of a capacitor C and the resistor R. The inductors L model the leads to the resistor R, and C represents stray capacitance. Referring to
FIG. 1B
, the dotted line represents the idealized behavior of the resistor R, and the solid line represents the frequency-dependent behavior exhibited by the resistor at high frequencies. As illustrated, the real part of the impedance starts out at the value R, and then, as the frequency increases, decreases due to the effect of the stray capacitance, beginning at the point identified with numeral
102
.
Referring to
FIG. 2A
, a capacitor C is modeled as inductor L in series with resistor R
s
, and with the parallel combination of the capacitor C and resistor R
e
. The inductor L represents parasitic lead inductance, and the series resistor R
s
represents losses through the leads. The resistor R
e
represents losses through the capacitor dielectric at high frequencies. Referring to
FIG. 2B
, the dotted line represents the idealized behavior of the capacitor, and the solid line represents the behavior of the capacitor at high frequencies. As illustrated, the capacitor starts out exhibiting idealized behavior (where the imaginary part of the admittance divided by 2&pgr;f is constant and does not vary with frequency when both are plotted on log
10
scale axes). Then, as the frequency increases, this admittance parameter begins to increase at the point identified with numeral
104
.
Referring to
FIG. 3A
, the inductor L is modeled as a shunt capacitance C
s
in parallel with the series combination of inductor L and series resistance R
s
. The shunt capacitance C
s
represents the parasitic capacitance introduced by adjacent coils of the inductor, and the series resistance R
s
represents losses which occur through the coils and leads of the inductor. Referring to
FIG. 3B
, the dotted line represents the idealized behavior of the inductor, and the solid line represents the behavior of the inductor at high frequencies. As illustrated, the inductor starts out exhibiting idealized behavior (where the imaginary part of the impedance divided by 2&pgr;f is constant and does not vary with frequency when both are plotted on log
10
scale axes). Then, as the frequency increases, this impedance parameter begins to increase at the point identified with numeral
106
At this point, a natural question to consider is what frequencies are “high” frequencies? The answer is that a “high” frequency is one which depends upon the circumstances and includes consideration of several factors such as whether the more sophisticated circuit analysis techniques referred to above are required, whether the corresponding wavelength is comparable with or less than the physical dimensions of the circuit elements involved, whether parasitic reactances are significant compared to the primary parametric value, and whether unspecified responses at higher harmonics thereof contribute to circuit performance. Referring to the table below, which is a classification of the frequency spectrum developed by the Institute of Electrical and Electronic Engineers (IEEE), it can be seen that the wavelength begins to be comparable to the physical dimensions of typical circuits elements at a point somewhere within or preceding the VHF band. In light of this factor and the other factors mentioned above, a general rule is that, a “high” frequency is any frequency beyond a point somewhere within or preceding the VHF band. Coincidentally, RF frequencies are generally understood to extend from somewhere within the VHF band to and including the S band, so “high” frequencies are generally understood to include RF frequencies. Moreover, microwave frequencies are generally understood to begin at and extend beyond the C band, so a “high” frequency is generally understood to include microwave frequencies as well.
WAVELENGTH IN
FREQUENCY BAND
FREQUENCY
FREE SPACE
ELF (Extreme Low
30-300
Hz
1,000-10,000
km
Frequency)
VF (Voice Frequency)
300-3,000
Hz
100-1,000
km
VLF (Very Low Frequency)
3-30
kHz
10-100
km
LF (Low Frequency)
30-300
kHz
1-10
km
MF (Medium Frequency)
300-3,000
kHz
0.1-1
km
HF (High Frequency)
3-30
MHz
10-100
m
VHF (Very High Frequency)
30-300
MHz
1-10
m
UHF (Ultrahigh Frequency)
300-3,000
MHz
10-100
cm
SHF (Superhigh Frequency)
3-30
GHz
1-10
cm
EHF (Extreme High
30-300
GHz
0.1-1
cm
Frequency)
Decimillimeter
300-3,000
GHz
0.1-1
mm
P Band
0.23-1
GHz
30-130
cm
L Band
1-2
GHz
15-30
cm
S Band
2-4
GHz
7.5-15
cm
C Band
4-8
GHz
3.75-7.5
cm
X Band
8-12.5
GHz
2.4-3.75
cm
Ku Band
12.5-18
GHz
1.67-2.4
cm
K Band
18-26.5
GHz
1.13-1.67
cm
Ka Band
26.5-40
GHz
0.75-1.13
cm
Millimeter wave
40-300
GHz
1-7.5
mm
Submillimeter wave
300-3,000
GHz
0.1-1
mm
The design of a high frequency circuit typically undergoes two distinct phases, a prototype phase and a production
Draxler Paul J.
Woodall William
Bachand Richard
Brown Charles D.
Do Thuan
Qualcomm Incorporated
Siek Vuthe
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