JPH012434A - pulse frequency modulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to pulse frequency modulation (hereinafter referred to as PFM).
Regarding. In particular, it relates to sub-data transmission means.

〔overview〕

The present invention expands the band of a modulated signal by changing the pulse width of a frequency-modulated pulse based on the sub-data in a sub-data transmission means of a device that transmits main data using pulse frequency modulation. This makes it possible to transmit sub-data without any need for transmission.

[Conventional technology]

Conventionally, in order to transmit sub-data on this type of PFM signal, sub-data is frequency-multiplexed on a baseband signal to be subjected to PFM, PFM is performed, and data is reproduced after baseband demodulation. Examples of conventional sub-data transmission are shown in FIGS. 6 to 9. FIG. 6 shows an example of modulation. The input bass punt signal e is as shown in FIG.
These are a video signal and an FM audio signal. data signal f
is FSK-modulated by an FSK modulator g, frequency-multiplexed with the input basepant signal e, and modulated into a PFM pulse train by a PFM modulator 7 as a frequency-multiplexed signal g shown in FIG. FIG. 7 shows an example of demodulation.

A PFM demodulator 9 outputs the PFM pulse train as a frequency multiplexed signal g. The baseband signal e is passed through a low-pass filter 11 to F
The SK modulated data signal component is removed from the frequency multiplexed signal g and output. Also, the data signal f is passed through the bandpass filter 1
2, extract the FSK modulation component from the frequency multiplexed signal g,
The signal is further demodulated by an FSK demodulator 10 and then output.

[Problem that the invention seeks to solve]

In this way, in conventional sub-data transmission, the data signal is
Since an FSK modulator and an FSK demodulator are required for SK modulation and demodulation, and a low-pass filter and a bandpass filter are required to separate the frequency multiplexed signal after PFM demodulation, the circuit size is reduced. The disadvantage is that it gets bigger. In addition, since the FSK modulated data signal is frequency-multiplexed on the baseband signal, the modulated signal band seen from the PFM modulator and demodulator becomes wider than the baseband signal band. There is a drawback that the degree must be reduced.

The present invention aims to eliminate such drawbacks, and aims to provide a pulse frequency modulation device that can transmit sub-data with a simple circuit configuration without significantly expanding the modulated signal band.

[Means for solving problems]

The present invention provides a pulse frequency modulation device including main data modulation means for generating a modulated signal in which the repetition frequency of periodic pulses is modulated according to main data, in which the pulse width of the pulse included in the modulated signal is The present invention is characterized by comprising sub-data modulation means that generates a new modulated signal changed according to the sub-data.

[Effect]

The pulse time width of the modulated signal, which is pulse frequency modulated according to the main data, is changed according to the sub data and transmitted. The demodulation side demodulates the sub-data based on this change in pulse time width.

As a result, the frequency band of the modulated signal output modulated by the sub-data does not expand significantly with respect to the input base punt signal of the main data.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block configuration diagram showing the overall configuration of this embodiment. This embodiment includes a pulse frequency modulation circuit 15 modulated with main data 1 and a pulse width modulation circuit 20 modulated with sub data C.

FIG. 2 is a block diagram showing details of the pulse width modulation circuit in this embodiment. This pulse width modulation circuit 20
As shown in Figure 2, generates a new modulation signal in which the pulse width of the pulse included in the modulation signal is changed in accordance with the sub-data, and the repetition frequency of periodic pulses is changed in accordance with the main data. D-FFI which is sub data modulation means
, a delay circuit 2, a delay circuit 3, and a switch circuit 4. That is, the modulation side of this embodiment includes a D-FF1, delay circuits 2 and 3 having delay amounts of TI and τ2, respectively, and a switch circuit 4 that selects a delay circuit based on data C.

Now, the PFM pulse train a obtained by PFM modulating the baseband signal is inputted to the CLK terminal of the D-FFI. At this time, the D terminal power is set so that the Q output is at a high level. The Q output passes through either the delay circuit 2 or 3 selected by the switch circuit 4 that operates based on the state of the data C, and is input to the R (reset) terminal of the D-FF 1.

In this embodiment, when the data is "l", the delay circuit 2 is
When the data is "0", the delay circuit 3 is selected. Further, the relationship between the delay amounts of delay circuits 2 and 3 is τ1>τ2. The PFM input pulse train a is output as a PFM pulse train having different pulse widths according to the data signal C.

FIG. 4 is a block configuration diagram showing the configuration of an embodiment for demodulating sub-data. This embodiment includes a D-FF 5 and a delay circuit 6 with a delay amount τ3.

Now, the PFM pulse train whose pulse width has been modulated by the sub-data is inputted to the D (data) terminal of the D-FF 5, passes through the delay circuit 6, and is inputted to the CLK terminal. By setting the delay amount r of the delay circuit 6 in advance to 7〉τ3〉T2, the demodulated sub-data C' is output as the Q output of the D-FF 5.

〔Effect of the invention〕

As explained above, the present invention transmits sub-data by modulating the pulse width of the PFM pulse train.
The modulated bandwidth of the PFM modulator/demodulator can be set to be the same as the baseband band of the pleasant sound signal, and the advantage is that it can be achieved with a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration on the modulation side of an embodiment of the present invention. FIG. 2 is a block configuration diagram showing a partial configuration on the modulation side of the embodiment of the present invention. FIG. 3 is a waveform diagram showing the modulation operation of the embodiment of the present invention. FIG. 4 is a block configuration diagram showing the configuration on the demodulation side of the embodiment of the present invention. FIG. 5 is a waveform diagram showing the demodulation operation of the embodiment of the present invention. FIG. 6 is a block configuration diagram showing the configuration on the modulation side of a conventional example. FIG. 7 is a block configuration diagram showing the configuration on the demodulation side of a conventional example. FIGS. 8 and 9 are waveform diagrams showing signal waveforms at various parts in the conventional example. 1.5...D-FF, 2.3.6...Delay circuit, 4
...Switch circuit, 7...PFM modulator, 8...
FSK modulator, 9...PFM demodulator, 10...FS
K demodulator, 11...Low pass filter, 12...Band filter, 15...Pulse frequency modulation circuit, 20...Pulse width modulation circuit. a...PFM pulse train, bSd...PFM pulse train pulse width modulated by sub data, c, f...
・Sub data, C'... Demodulated sub data, e... Base node signal, g... Frequency multiplexed signal, h...
Pulse train, i...main data. Patent applicant: NEC Corporation. Agent Patent Attorney Nao Takashi Ide Structure of the embodiment Fig. 1 T-barrel side of the embodiment Fig. 2 Modulation side of the conventional example Fig. 6 Demodulation side of the conventional example Fig. 7

Claims (1)

[Claims] (1) In a pulse frequency modulation device equipped with main data modulation means for generating a modulated signal in which the repetition frequency of periodic pulses is modulated according to main data, the pulse width of the pulse included in the modulated signal is subdivided. A pulse frequency modulation device comprising sub-data modulation means for generating a new modulated signal changed according to data.