Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
1998-07-31
2001-04-03
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
C455S067700, C455S226100
Reexamination Certificate
active
06212479
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power detector and more particularly to a super heterodyned power detector with enhanced linearity for use in power leveling loops.
FIG. 1
shows a typical power leveling loop in which a source
10
provides a frequency Fl to power modulator
12
. Modulator
12
provides an input to directional coupler
14
, which in turn provides an output F
1
on line
16
and an input F
1
of broad band power detector
20
. This design uses power detector
20
to convert the coupled signal to DC, which is then filtered through LPF
22
and compared to a power reference voltage
26
in difference amplifier
24
. The difference signal
28
drives the loop integrator
29
which in turn drives the power modulator
12
, so that the power is automatically adjusted until the detector voltage equals the reference voltage. This approach has several limitations:
1. The directional detector must operate at the measurement frequency. This degrades the performance in several ways.
a. The detector performance is not constant with frequency. Therefore, when the power is adjusted by changing the reference setting, the output power change is not constant with frequency.
b. The detector must have enough bandwidth to operate at all output frequencies. For microwave systems, this can mean more than 10 gigahertz of bandwidth. This broad bandwidth limits the sensitivity of the leveling loop, since the noise power is proportional to bandwidth. As a result, the power adjustment range of the loop is reduced. In addition, since the detector responds to all frequencies within the bandwidth, output power at frequencies other than the desired output frequency will effect the power setting.
c. The requirement for full frequency coverage can also result in added system complexity, since there may be no single detector with adequate bandwidth to cover the entire frequency range. If this is the case, some sort of frequency multiplexing with multiple detectors would become necessary.
2. When the power is varied, the variation appears directly at the detector. Therefore, the power control accuracy is degraded by nonideality of the detector device.
3. The directional coupler reduces the maximum power available to the test port.
In view of the foregoing, it would be desirable to provide an improved power detector.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved power detector and more particularly a power leveling loop with a superheterodyned adjustable gain power detector.
In one preferred embodiment, the adjustable gain power leveling detector receives an output signal from a directional coupler. According to the present invention, the leveling detector includes means for producing a signal whose amplitude is proportional to the amplitude of the output signal from the directional coupler and whose frequency is equal to a fixed intermodulation IF frequency, a power detector for providing a stable DC output voltage signal for an input of a single power at the IF frequency; and a leveling loop for maintaining the power detector DC voltage signal substantially constant for output powers in the power adjustment range.
Other objects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3611130 (1971-10-01), Larsen
patent: 5835850 (1998-11-01), Kumar
Krombholz Michal
Shoulders Robert E.
Agilent Technologie,s Inc.
Shah Kamini
LandOfFree
Super heterodyned power detector with enhanced linearity for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Super heterodyned power detector with enhanced linearity for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Super heterodyned power detector with enhanced linearity for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2491168