JPS6217422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM broadcasting device, and more particularly to an FM broadcasting device with a good S/N ratio and high efficiency.

Conventionally, a switching regulator has been used as a power source for a power amplifier in an FM broadcasting device that performs stereo broadcasting in order to increase efficiency. The operating frequency of this switching regulator is set to 20 KHz or the like within the signal band of the frequency spectrum shown in FIG. In FIG. 1, Sp is a pilot signal that is used as a reference for distinguishing between stereo and mono.

In broadcasting equipment that uses a switching regulator set to such a frequency, the frequency of the switching regulator is mixed into the transmission signal by radiation from the power amplifier's signal circuit, causing the S/N ratio to decrease. It has deteriorated. In order to eliminate this, the arrangement of the switching regulator and shielding must be considered, which is complicated. Furthermore, when there is no pilot signal (in the case of mono), it is operated so that the pilot signal is present due to mixing.

The present invention has been made in view of this problem, and provides an FM broadcasting device in which the operating frequency of the switching regulator is selected to be at least four times the frequency of the reference signal.

An embodiment of the present invention will be described below with reference to the drawings. As shown in Fig. 2, from the stereo modulator 2 to which the left L signal, right R signal and pilot signal are supplied, (L+R) components up to 15KHz, the pilot signal of 19KHz and the pilot signal frequency are output as in Fig. 1. The (LR) components, which become sub-channels whose amplitude is modulated twice as much as 38 KHz, are multiplexed and derived. The output from the stereo modulator 2 is frequency modulated by a frequency modulator 4, then amplified by a power amplifier 6, and supplied from an output terminal 8 to a transmitting antenna or the like.

The stereo modulator 2, frequency modulator 4, and power amplifier 6 are supplied with operating power from a power supply 10, and the power amplifier 6 is supplied with operating power via a switching regulator 12. This switching regulator 12 increases the efficiency of the broadcasting device, and its operating frequency (o) is four times the frequency (19KHz) of the pilot signal sp, that is, 76K.
Set to Hz.

Therefore, the operating frequency (o) of the switching regulator 12 is set to a high frequency outside the signal band, as shown in FIG. 1, and four times the frequency of the reference pilot signal included in the stereo signal. be done. Since this frequency (o) is outside the signal band, even if it is mixed in, it can be easily removed with a filter or the like. In addition, the components that affect the signal band due to contamination are 38KHz and
19KHz, but the 19KHz component is at a low level and will not be confused with the pilot signal, and the 38K
The Hz component is the same as the modulation frequency of the (LR) component and does not cause any harmful effects.

Therefore, the switching regulator 12 can be placed close to the power amplifier 6, and there is no need to consider its placement or shielding.

Further, an embodiment in which the present invention is applied to audio multiplex broadcasting in television broadcasting will be described below with reference to FIG.

This broadcast is performed in stereo and multiplex, and in this stereo broadcast, the frequency spectrum of the signal introduced into the frequency modulator 4 has (L+R) components up to 15KHz, as shown in Figure 3.
31.5KHz frequency was frequency modulated (L-R)
It is an ingredient. This will be the secondary channel (L
-R) component frequency of 31.5 KHz is set to the horizontal scanning frequency (15.75 KHz) as a reference signal, and is selected to be twice this frequency.

Therefore, the switching regulator 1
The operating frequency (o) of No. 2 is set to 63 KHz, which is four times the reference horizontal scanning frequency. This frequency (63KHz) is outside the signal band and does not affect the transmission signal in any way as mentioned above.

Further, in multiplex broadcasting using A signal and B signal, the (LR) component shown in FIG. 3 becomes the A signal component, and the (L+R) component becomes the B signal component. Even in this case, switching regulator 1
The operating frequency (o) of No. 2 is set outside the 63KHz signal band as described above. Note that SQ is a signal for distinguishing between multiplex broadcasting and stereo broadcasting.

As explained above, according to the present invention, it is possible to maintain high efficiency and eliminate or reduce contamination due to the operating frequency of the switching regulator, and to achieve a good S/N ratio.
You can get FM broadcasting equipment.

[Brief explanation of the drawing]

Fig. 1 is a frequency spectrum diagram explaining stereo broadcasting of a conventional FM broadcasting device, Fig. 2 is a circuit configuration diagram showing an embodiment of the FM broadcasting device according to the present invention, and Fig. 3 is another embodiment of the present invention. FIG. 2 is a frequency spectrum diagram illustrating. 2... Stereo modulator, 4... Frequency modulator,
6...Power amplifier, 12...Switching regulator.

Claims (1)

[Claims] 1. In an FM broadcasting device that has a frequency modulator that modulates a multiplexed signal including a signal according to a reference frequency, a power amplifier that amplifies the output of this modulator, and a switching regulator that supplies power to this power amplifier. , An FM broadcasting device characterized in that the operating frequency of the switching regulator is selected to be at least four times the reference frequency.