JPS6037661B2 - Sample value conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample value conversion circuit, and more specifically, a sample value conversion circuit that converts a sample value series sampled at a certain phase into the same sample value series as a sample value series sampled at another phase. Related to conversion circuit.

For example, an NTSC composite color television signal has a constant sampling frequency (e.g., four times the color subcarrier frequency NaSc).
When sampling with , there is a degree of freedom regarding the phase, but it is usually performed on the 1 and Q axes, or on the (R-Y) and (B-Y) axes. The former is preferable when the band width of the color signal strictly conforms to the standard, and the latter is preferable for simplifying the circuit. Now, as mentioned above, since there are sampling methods using at least two different phase sets, it may be necessary to mutually convert these. Conventionally, this method demodulates the color signal and converts each component of Y, 1, and Q, or Y, (R
-Y) and (B-Y) are obtained, and these 1, Q, and (R-Y), (B-Y) are multiplied by coefficients according to the NTSC standard and converted by performing matrix operation. A method was taken.

However, in this case it was necessary to modulate the color subcarrier again to obtain sampling in the other axis.
- An object of the present invention is to realize a conversion circuit that directly obtains a sample value series sampled at a ground phase without demodulating the sample value series sampled at a certain phase.

That is, for example, a value sequence sampled on the 1,Q axis of a color television signal...g-,, soft, &, saddle,...
..., directly sample value series on the (R-Y) and (B-Y) axes...h-. , to,h,,h2,...

In order to achieve the above object, the present invention adds a plurality of sample value signals sampled at a certain phase (referred to as a sample value sequence) to a delay element, and multiplies the delayed sample sequence by a certain coefficient. By weighting and adding the sample sequence signals with the different phases, the sample sequence signals are converted into sample sequence signals that are substantially equal to the sample sequence signals sampled at different phases.

According to the present invention, a conversion circuit can be easily constructed using only a delay element and a simple series addition circuit. Hereinafter, the present invention will be explained in detail using the drawings.

Figure 1 shows the sample sequence when an NTSC decoded color television signal is sampled at a sampling frequency that is four times the color subcarrier frequency. ...Saddle, ...... is 1, and when sampling is performed on the Q axis, the system is indicated by the dotted line. ,h,,...also,
. . . indicates a case where sampling is performed on the (RY) and (BY) axes. A certain relationship exists between these series, and one sample series can be converted to another according to the principle described below. According to the sampling theorem, the source waveform 〆t is s
With t as the sampling function (=sint/f), F・Z g
iS(t-iT) ......{1113'' Represented by nu.

T is the sampling interval, which in this case is normalized by T/2. Therefore, the signal sequence...h-,,ho,h,,h
2... defines Q-1'Qo'Q... as shown in Figure 2, and hk=. Z g skin Q;・ ……■・
It is expressed in diagonals.

Since Q, becomes smaller as the absolute value of i becomes larger, N.・・・・・・【31h
k3. Z gk+i Q-11==1N.

Therefore, it can be seen that the sample sequence hk from the sample sequence gk can be easily realized by calculation.

FIG. 3 is a diagram showing the circuit configuration of an embodiment of the sample value conversion circuit according to the present invention. Now, the analog sample value series g-, , dynamic, seal, &... is added from the input terminal 1.

This is delayed by analog shift register 3. The analog shift register 2 can be thought of as a plurality of delay elements connected in tandem in multiple stages, each having a delay time equal to the sampling period. The outputs of each stage are multiplied by a coefficient by a load resistor 3, added, and outputted to an output terminal 4 as other sample value series h-, , L, h, , h2, . . . . The present invention is not limited to the above embodiments, but can be implemented in various ways.

For example, it can be realized by the following embodiment. {1} Instead of analog conversion, it is also possible to perform digital conversion on the A/D converted signal sequence.

In this case, the multiplication circuit becomes a problem, but in addition to the usual method of dispensing with a read-only memory, methods of obtaining coefficients by shifting, addition, and subtraction are also widely known. For example, from Fig. 2, Qo = 0.94562, which is Qo i0
．． 94562 Ni1-1/16 (11/64), and similarly Q,,Q2 can be approximated as o,=-0.25370=-1/
It can be approximated as 4 o2 = 0.14650 = 1/8 (11/64), and each data may be shifted by a predetermined number of bits and added.

■ Equations '1}, [2', {3}' hold true in general, not just for TV signals, so this method is applicable not only to TV signals, but also to TV signals.
It is clear in principle that this holds true for any signal.

(3) Although the configuration in the embodiment shown in FIG. 3 is of a transversal filter type, there are various other non-recursive filters that exhibit characteristics equivalent to this type, and can be configured using known methods.

As described above, the present invention is extremely effective in practical use because it allows conversion between signal sequences having different sampling phases with a simple circuit.

[Brief explanation of the drawing]

1 and 2 are waveform diagrams for explaining the principle of the present invention, and FIG. 3 is a circuit diagram of an embodiment of the present invention. 1... Input terminal, 2... Delay circuit element, 3... Load resistance, 4... Output terminal. Drawing 2, Figure 3

Claims (1)

[Claims] 1 The first sampled signal sequence sampled at a certain phase is
In the conversion circuit that converts into a second sampled signal sequence sampled with a certain phase difference with respect to the above-mentioned certain phase,
guiding the first sampled signal sequence to a plurality of delay elements;
The second
A sample value conversion circuit characterized in that it obtains a sampled signal sequence.