Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Demand – excess – maximum or minimum
Reexamination Certificate
2002-09-18
2003-11-04
Cuneo, Kamand (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Demand, excess, maximum or minimum
C324S1540PB
Reexamination Certificate
active
06642703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a signal detector and a detecting method thereof. More particularly, the present invention relates to a peak detector and a detecting method having input signal triggering control and low frequency energy attenuation capability
2. Description of Related Art
A peak detector is a device capable of measuring the peak value of a voltage signal. However, most peak detectors have no special faculties for distinguishing between high and low frequency signals. In real applications, the capacity of a peak detector to find the degree of signal attenuation in a local area network (LAN) or transmission medium such as cable or twisted pair is very important.
FIG. 1
is a circuit diagram of a conventional peak detector. As shown in
FIG. 1
, the conventional peak detector
10
comprises of a comparator
12
, an NMOS transistor
14
, a resistor
16
, a capacitor
18
and a current source
20
. The positive input terminal of comparator
12
is a terminal for receiving an input signal. The negative input terminal of comparator
12
is connected to a node point N
1
. The output terminal of comparator
12
is connected to the gate terminal of NMOS transistor
14
. The source terminal of NMOS transistor
14
is connected to the output terminal of current source
20
. The drain terminal of NMOS transistor
14
is connected to node point N
1
. One end of resistor
16
is connected to node point N
1
while the other end of resistor
16
is connected to ground GND. One end of capacitor
18
is connected to node point N
1
while the other end of capacitor
18
is again connected to ground GND. The input terminal of current source
20
is connected to a voltage source VCC.
FIG. 2A
is a diagram showing an example signal waveform as measured by a conventional peak detector.
FIG. 3A
is a diagram showing the signal waveform shown in
FIG. 2A
after signal attenuation.
For example, when the peak detector
10
shown in
FIG. 1
is used to detect voltage peak, the detected signal before attenuation has a waveform
30
shown in FIG.
2
A. Since the peak detector
10
is incapable of distinguishing between low and high frequencies, output waveform
40
is still quite rugged even after attenuation as shown in FIG.
3
A. In other words, if low frequency signals are not attenuated, signal waveform measured by the peak detector is bound to contain larger ripples.
In addition, several conventional techniques related to the design of peak detectors can be found in the following U.S. Patents.
(1) John D. Young et. al, in “High Speed Gated Peak Detector”, U.S. Pat. No. 4,6620,444.
(2) Robert H. Leonowich et. al, in “Master-Slave Peak Detector”, U.S. Pat. No. 5,254,881.
(3) Stan Dendinger et. al, in “Closed-Loop Peak Detector Topology”, U.S. Pat. No. 5,428,307.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a peak detector. The peak detector having input signal triggering control and low frequency energy attenuation capability. The peak detector includes a charging unit and a discharging unit. By being triggered by a peak value detected in a received input signal by comparing voltage potential levels of the output signal of the peak detector and the received signal, the charging unit charges an electrical charge storage unit, for example, a capacitor, connected to the output terminal of the peak detector for a pre-determined charge duration in accordance with a charge pulse being in a logic high. After the pre-determined charge duration of charging operation, before being triggered by a next peak value of the received input signal, the discharging unit discharges the electrical charge storage unit for a pre-determined discharge duration in accordance with a discharge pulse being in a logic high or in accordance with a plurality of discharge pulses, which is determined by design desired.
The invention provides a peak detector for receiving an input signal and output a peak signal from an output terminal. The peak detector comprising a comparator, a programmable pulse generator, a logic unit, an electrical charge storage unit, a charging unit and a discharge unit. The comparator receives the input signal and the peak signal and generates a comparing signal by comparing the input signal and the peak signal. The programmable pulse generator receives the comparing signal and generates a first pulse signal and a second pulse signal in according to the comparing signal. The logic unit receives the first pulse signal and the second pulse signal and outputs a first control signal and a second control signal. The electrical charge storage unit is coupled to the output terminal of the peak detector. The charging unit charges the electrical charge storage unit during a pre-determined charge duration in response to the first control signal to increase a voltage potential level of the peak signal. The discharge unit discharges the electrical charge storage unit during a pre-determined discharge duration in response to the second control signal to decrease the voltage potential level of the peak signal.
In the peak detector above, the pre-determined charge duration is determined in accordance with the period of the first pulse signal being in the logic high, and the pre-determined discharge duration is the period of the second pulse signal being in the logic high. A charging/discharging ratio of the peak detector is determined by (a pre-determined charge duration×the value of the first current source)/(a pre-determined discharge duration×the value of the second current source). The pre-determined charge duration is the period of the first pulse signal being in the logic high, and the pre-determined discharge duration is the period of the second pulse signal being in the logic high.
In the peak detector above, the programmable pulse generator is used for generating a first pulse signal and a second pulse signal in accordance with the comparing signal of the comparator and an external clock signal. In an example, the programmable pulse generator is triggered by the comparing signal and the pulse duration of the first pulse signal or the second pulse signal can be determined by the external clock signal. That means that the pre-determined charge duration and the pre-determined charge duration depend on the external clock signal.
For above-mentioned object of the invention, a method for detection a peak attitude of an input signal and output a peak signal is provided. The method comprises comparing voltage potential levels of the peak signal and the received signal and generating a first pulse signal; charging an electrical charge storage unit during a pre-determined charge duration in accordance with the first pulse signal being in a logic high; after the pre-determined charge duration, before being triggered by a next peak value of the input signal, generating a second pulse signal and discharging the electrical charge storage unit during a pre-determined discharge duration in accordance with the second pulse signal being in a logic high.
In the method above, a value of the voltage potential level of the peak signal being increased depends on the pre-determined charge duration. The electrical charge storage unit is charged by a first current source. A value of the voltage potential level of the peak signal being increased depends on the pre-determined charge duration and the value of the first current source.
In the method above, a value of the voltage potential level of the peak signal being increased depends on the pre-determined discharge duration and/or the value of the second current source.
In the method above, the electrical charge storage unit is charged by a first current source and is discharged by a second current source. A charge/discharge ratio is determined by (the pre-determined charge duration×the value of the first current source)/(the pre-determined discharge duration×the value of the second current source).
The peak detector comprises of a comparator, an input-trigger
Chen Chi-Ming
Chen Pi-Fen
Cuneo Kamand
J.C. Patents
Macronix International Co. Ltd.
Nguyen Jimmy
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