Modulators – Amplitude modulator – Nonlinear device controlled by modulating signal
Patent
1986-01-30
1987-04-07
Grimm, Siegfried H.
Modulators
Amplitude modulator
Nonlinear device controlled by modulating signal
332 48, 332 49, 332 60, 332 64, 455 47, 455109, H03C 160
Patent
active
046564403
ABSTRACT:
A broadcast transmitter with single-sideband modulation for transmitting a message with a band width and carrier power which is lower in comparison with double-sideband modulation. To be able to operate a high-power single-sideband transmitter with only one transmitting tube, a single-sideband modulator (1) is used which generates, as a function on a modulating LF signal (2), a zero-phase modulator amplitude signal (9) which amplitude-modulates the anode (23) of an RF output stage tube (26) via a digital/analog converter (21), constructed as a switching amplifier with pulse step modulation, and an RF filter (22). The single-sideband modulator (1) also supplies a modulator phase signal (19) which is preferably not amplitude-dependent and which is fed to the control grid of the RF output stage tube (26), if necessary via a frequency converter (25). The single-sideband modulator (1) can be of digital or analog construction; at its input it has a Hilbert transformer which splits the modulating input signal (2) into two component signals which are phase-shifted by 90.degree. and at its output it is also provided with an amplitude computer, a cyclic switch having a clock frequency (f.sub.T) which is preferably equal to 4 times the carrier frequency (f.sub.1) and, if necessary, a quotient computer and a subsequent band-pass filter. A residual carrier signal can be added to the input signal (2) or to the output signals of the Hilbert transformer.
REFERENCES:
patent: 4417358 (1983-11-01), Zeis
patent: 4593410 (1986-06-01), Kyrian
Kocher et al., "A New 500 kW Short-Wave Transmitter", Brown Boveri Review 5/6, 1983, pp. 235-240.
Munger et al., "A New 600 kW Medium-Wave Transmitter", Brown Boveri Review 5, 1984, pp. 202-205.
Nohara et al., "Generation of Single-Sideband Signal Using Switched-Mode Technique", Bull. Univ. Osaka Prefect. A. (Japan), vol. 23, No. 2, 1974, pp. 167-176.
BBC Brown Boveri & Company Limited
Grimm Siegfried H.
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