 PSK modulator with noncollapsable output for use with a PLL power amplifier |
| The present invention pertains to a PSK modulator for use with either wideband power amplifier up ... |
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| Spectrally efficient digital modulation method and apparatus |
| One object of the present invention is to provide a method of pulse shaping which permits ... |
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| Amplifier with distortion reducing feedback |
| Accordingly, an object of the invention is to provide an amplifier device in which the distortion ... |
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| Pulse step modulator |
| The present invention is directed to minimizing dissipation by the unit step modules in a pulse ... |
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| High frequency pulse amplifier |
| I claim: 1. A high frequency power amplifier comprising: a power amplifier stage including a ... |
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| Low distortion operational amplifier |
| In accordance with the present invention, an operational amplifier (op-amp) operates to work with ... |
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| Protection circuit for RF power amplifiers |
| It is an object of this invention to provide a generic control amplifier that can receive feedback ... |
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| Portable radio communication equipment |
| The present invention has been made to solve the problems described above, and its object is to ... |
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| Temperature insensitive piezoelectric crystal mounting arrangement |
| OF THE PREFERRED EMBODIMENT FIG. 3A illustrates a simplified top view of the crystal mounting ... |
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| Impulse generator for use with phosphor energizable lamps |
| OF A PREFERRED EMBODIMENT Referring now in more detail and by reference characters to the drawings ... |
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System for set-up of transmitters in high capacity digital radio links
| Details |
Inventors: Cardini, Lorenzo; Perego, GianCarlo; Nobili, Rocco;
Assignee: Telettra-S.p.A. (IT)
Primary Examiner: Kuntz; Curtis
Assistant Examiner: Tse; Young
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb Soffen
The invention relates to a system for initializing transmitters in high capacity digital radio links, in which a digital signal with QAM (Quadrature Amplitude Modulation) modulation is transmitted over a radio frequency carrier wave. The initialization of the transmitter is accomplished by generating a plurality of sinusoidal signals (tones), adding those tones together to simulate a digital singal to be transmitted, sending the simulated digital signal through the transmitter, and adjusting the transmitter to compensate for the intermodulation odd order products developed as a result of the nonlinearity of the power amplifier in the transmitter. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG.
5 shows a block scheme of the generator 6 of the test signal of the invention.
The invention includes four sinusoidal oscillators 7, 8, 9, 10 operating at different frequency (but included in the field of IF) that can be cut off singularly by means of switches.
The generated tones are combined in the summator 11 S and amplitude-modulator 12 in by the square wave 13 (with adjustable "duty cycle" and levels) shown in FIG.
6a and generated by the square wave generator 14.
As a result of the amplitude modulation, the output power of the test signal has the behavior shown in FIG.
6b, where Pm represents the transmitted mean power and P1 and P2 indicate the mean power associated to the statuses 1 and 2 having a duration T1 and T2, respectively, of T=T.
sub.
1 +T.
sub.
2, the square wave 13 period.
T is selected so that the frequency of the square wave 1/T is much less than the signal frequency f.
sub.
IF and, at the same time, sufficiently fast so that automatic level control circuits present in the transmitter do not sense the power change in jumps among statuses 1 and 2, but instead the sole mean power value Pm.
Acting on the levels V.
sub.
1 and V.
sub.
2 of square wave 13, it is possible to adjust: r=P2/P1 while acting on the "duty cycle" of square wave 13, it is possible to adjust: d=T1/T Therefore, considering these parameters: P mean transmitted=(P1T1+P2T2)/T= ##EQU1## Remembering that for a signal formed by the sum of N sinusoidal uncorrelated tones: ##EQU2## it can be assumed that the instantaneous signal peak power with N modulated tones is equal with the mean power associated to the status 1 summed with the power increase associated with the (instantaneous) combination in phase of the N tones as numerically specified above: (Ppeak)dBm=(P1)dBm+(N)dB Finally, the result is obtained that: ##EQU3## It can be concluded that using the shown system and keeping the transmitted mean power constant, it is possible to control the dynamics of instantaneous amplitudes simply by selecting: ##STR1## Using the present invention, as a result of the structure of the test signal generator 6, N can be selected to be equal to 1, 2, 3 or 4
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Audio Signal Processing 
