KR920009639B1 - Analog audio scrambling method and apparatus by using inversion - Google Patents

Abstract

The apparatus is for scrambling analog audio by quadratic-spectrum inverting and random-carrier-phase drifting without A/D converter and memory to reduce the cost of manufacturing. Its process includes the followings: (A) generating sine wave and cosine wave of random phase of which center frequency is fH by separating horizontal sync. from composite video signal; (B) dividing analog signal into two components, quadrature-amplitude modulating them with the sine and cosine waves respectively to shift its spectrum by fH, and (C) adding them and band-limiting with cutoff frequency of fH to generate scrambled analog signal.

Description

Method and apparatus of analog audio scrambling by inversion

1 is a conventional device block diagram.

2 is a device block diagram according to the present invention.

3 is a main output waveform diagram in FIG.

* Explanation of symbols for the main parts of the drawings

1: Horizontal Sync Signal Separator 2,8: BPF

3: carrier random phase generator 4: phase shifter

5,6,11: LPF 7,9: Balance Modulator

10: adder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to audio scrambling, in particular analog audio by quadratic spectrum inversion and random carrier phase drift adapted to analog audio scramble. It relates to a scrambling method and apparatus.

As a conventional digital scrambling method, an analog signal is converted into a digital signal by an A / D converter and scrambling is performed by time compression and time inverse arrangement using a memory.

That is, in FIG. 1, the analog audio signal is converted into a digital signal by the A / D converter 101, and the data corresponding to 65 kHz is stored in the memory 102, which is again reversed by the address control circuit 103. The data is read and stored in the memory 104 again.

If the Data Read Rate is higher than Write, the data is compressed and rearranged in the reverse order.

The scrambled audio is finally obtained through the D / A converter 105.

However, such a conventional technology configuration requires a high-cost A / D converter and a memory, so that the overall price increases.

Accordingly, in order to solve the above disadvantages, the present invention increases the S / N by band limiting the low pass filter (LPF) of the audio analog signal, and the spectrum is divided into two bands by the LPF and the band pass filter (BPF). Divide the two spectra into parts by scrambled by shifting the spectrum (full audio spectrum) by fH by QAM (Quadrature Amplitude Modulation) and filtering by LPF with Cut Off = fH. Changes the phase of the carrier to be random and the Random Sequence Initial Data (All of the random sequences can be known only by knowing this initial data). 2, the Horizontal Sync. Separtor 1 separates the horizontal synchronous signal from the composite video signal. The BPF 2 and the random phase generator 3 having the center frequency fH are used to generate a sine wave having the random phase of the fH frequency.

On the other hand, the analog audio signal as shown in FIG. 3a is band-limited using the LPF (5) whose cut off frequency is fH to increase the signal-to-noise ratio, and then the audio spectrum is adjusted. As shown in Figs. 3b and c, the LPF 6 and the BPF 8 are divided into two parts. Among these two parts, the output of LPF (6) is called ML (t), the output of BPF (8) is called MB (t), and the previous fH sine wave is shifted by 90 ° phase shift (4) to obtain the fH cosine wave. And two Balanced Modulators (7, 9), using MI. (T) Cos ｛2πfH + △ (t)｝ and MB (t) sin ｛2πfHt + △ (t)｝ as shown in 3d, e. Make The outputs of these two balance modulators 7 and 9 are summed by the adder 10 (see also FIG. 5f) and again filtered out to the LPF 11 with a cutoff frequency of fH and finally scrambled audio ana as shown in FIG. Randomly change the phase of the carrier used for spectral shifting to obtain a log signal.

Initial data of the random sequence is then carried on the delitext line. Knowing this initial data only tells us all the random sequences.

Therefore, the analog audio scrambling method and apparatus according to the present invention can be scrambling without using a high-cost A / D converter and memory, thereby reducing the cost.

Claims (2)

Separating the horizontal synchronous signal from the synthesized video signal to generate a sine wave and cosine wave having a random phase with a center frequency of fH, divide the analog signal into two parts, and then QAM the sine and cosine waves respectively to shift the spectrum by fH. And resuming the bands and band limiting the cutoff frequency to fH to obtain a scrambled analog signal. A horizontal synchronous signal separator (1) for separating the horizontal synchronous signal from the synthesized video signal, a BPF (2) for band passing such that the center frequency of the horizontal synchronous signal separated from the horizontal synchronous signal separator (1) becomes fH, and A random phase generator 3 that receives the output of the BPF 2 and generates a sine wave at an fH frequency, a phase shifter 4 which generates a cosine wave by shifting the output of the random phase generator 3 by 90 degrees; LPF (5) for band limiting the cutoff frequency of the analog audio signal to fH, LPF (6) and BPF (8) for dividing the output of the LPF (5) into two parts, the LPF (6) and A balance module (7) (9) and a balance modulator (7) (9) for QAM of two spectra divided by the BPF (8) with a sine wave and a cosine wave output from the random phase generator (3) and the phase shifter (4). The adder 10 and the output from the adder 10 to add the QAM signal from the An analog audio scrambling apparatus according to inversion, which is composed of an LPF (11) such that the cutoff frequency of the signal is fH, and is subjected to analog scrambling by quadratic spectrum inversion.

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