| 摘要 |
<p>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 DEG and at its output it is also provided with an amplitude computer, a cyclic switch having a clock frequency (fT) which is preferably equal to 4 times the carrier frequency (f1) 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.</p> |
