Amplifiers – Modulator-demodulator-type amplifier
Patent
1995-01-27
1997-04-15
Mottola, Steven
Amplifiers
Modulator-demodulator-type amplifier
330124R, 332145, H03F 338
Patent
active
056213514
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to the field of radio transmitter technology. It is based on a modulation amplifier according to the preamble of the first claim.
STATE OF THE ART
Such a modulation amplifier is already known from the European patent EP-B1-0 083 727.
A modulation amplifier of this kind comprises a signal converter, which converts a low frequency input signal into a multiple of control signals, a plurality of high frequency stages, which are driven by the control signals, and a high frequency oscillator.
The high frequency stages can be turned on and off independently and send a high frequency signal to their outputs. The output signals of these high frequency stages are added in a summator. So many stages are always driven or turned on now that the amplitude of the high frequency composite signal changes by steps in accordance with the low frequency input signal. In this manner the low frequency signal modulates the amplitude of a high frequency oscillation. One can simultaneously increase the power by adding the output signals of the high frequency stages, which can amount, e.g., to a few hundred volts.
There are also means that serve to approximate the difference of the step-shaped composite signal and the low frequency amplitude to be amplified.
These means comprise in the aforementioned document four high frequency stages with binarily weighted amplitudes of 1/2, 1/4, 1/8 and 1/16 of the amplitude of the other 31 coarse stages.
The drawback with this arrangement is that different types of stages have to be used and a lot more stress is put over time on the stages with the binarily weighted amplitude than on the other similar coarse stages. Since the stages are not stressed uniformly, the modulation amplifier is inherently susceptible to interference. If binarily weighted stages are defective, the other stages cannot assume their task. Consequently there is a range of high frequency noise that has a detrimental effect on the neighboring channels and decreases the low frequency quality.
There exists a special kind of amplitude modulation--the socalled ampliphase modulation--from various older publications (H. Chireix: "High Power Outphasing Modulation" in Proceedings of the Institute of Radio Engineers, vol. 23, no. 11, November 1935; G. Clark: "A Comparison of Current Broadcast Amplitude Modulation Techniques", in IEEE Transactions on Broadcasting, vol. BC-21, no. 2, June 1975; D. R. Mousson: "Ampliphase for Economical Super-Power AM Transmitters", in Broadcast Transmitter Engineering; F. J. Casadevall: "The LINC Transmitter", in RF Design, February 1990).
This kind of modulation is used for a transmitter in the European patent application EP-A2-0 273 827. This transmitter comprises two partial transmitters, which are driven with different phases, a unit, which controls the phases of the transmitters as a function of an input signal, and a summation network, which adds the output signals of both partial transmitters, in such a manner that an amplitude and phase modulated signal, whose amplitude changes in accordance with the input signal, is sent to the subsequent antenna. By dividing the transmitter into two partial transmitters the total transmitting power is divided between the two partial transmitters, so that each partial transmitter has to exhibit only a part of the total power.
PRESENTATION OF THE INVENTION
The object of the present invention is to provide a modulation amplifier, whose means for fine approximation do not represent inherent sources of error.
This problem with a modulation amplifier of the aforementioned kind is solved by means of the features of the first claim.
Thus, the essence of the invention is that the means for fine approximation and coarse approximation comprise similar stages, where the fine stages are driven with different phases. Thus, the coarse and fine stages differ only in the phases of the selection and output signals. Their internal construction, however, is identical. The same applies to the output amplitudes and output frequency.
In a
REFERENCES:
patent: 4164714 (1979-08-01), Swanson
patent: 4862116 (1989-08-01), Olver
patent: 4870374 (1989-09-01), Harris
Gehri Patrick
Kyrian Bohumil
Niklaus Peter
Puri Narindra N.
Tomljenovic Juraj
Mottola Steven
Thomcast AG
LandOfFree
Modulation amplifier for radio transmitters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Modulation amplifier for radio transmitters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Modulation amplifier for radio transmitters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-363878