JPS60141022A - Coder and decoder - Google Patents

Abstract

PURPOSE:To satisfy the insertion loss variation and te crosstalk characteristic specification by providing a selection circuit to the input stage of a transmission or reception filter and adjusting the gain of a coder or a decoder through the selection so as to use a single reference voltage source. CONSTITUTION:It is made possible to adjust the gain of the reception side independently of the gain adjustment at the transmission side by using a reception filer 14' and a gain adjusting section 21. Fig. (a) shows an example of the input stage of the reception filter 14' with a switch group, a capacitor group and an input stage amplifier 28. Switches 22, 23 are for substantial switched capacitor operation so as to constitute the input stage of a PAM output wave of the decoder 6. Other switches and capacitors 24'-27', represent the input capacitor group and the switch group and the gain adjustment section 21 is constituted as an example by a 2-bit selection signal generating circuit. Only the switches of the switches 24-27 are conductive when they are selected by the gain adjusting section 21 and the remaining switches are nonconductive. The gain adjustment of the reception side is conducted independently by the reference voltage source 19 and the output voltage adjusting section 20 at the input stage of the filter 14' in this way.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a code decoder.

(Prior Art) Conventionally, an encoder/decoder (hereinafter referred to as CODEC) has a built-in reference voltage source.

The first south part is a prong showing the first example of a conventional CODEC.

This is a diagram. In FIG. 142, the analog signal is band-limited and then applied to the analog input terminal 1.

The signal is converted into a j9PcM signal by the encoder section 5 and outputted from the digital output terminal 2. The PCM signal input from the digital input terminal 4 is converted into an 8kHz PA by the decoder section 6.
M (Pulse Amplitude
la ti on5. Output from the analog output terminal as a wave. Single unit used for encoder section 5 and decoder section 6
The reference pressure is supplied from terminal 7. Since the single reference voltage applied from terminal 7 can be easily driven with low impedance,
Even if it is used in common for the encoder section 5 and decoder section 6, the crosstalk characteristics usually do not deteriorate.

Since the CODEC system uses a sampling system that samples every 8 kHz, the analog signal input to the encoder section must be limited to a frequency of 4 kHz or less according to the sampling theorem.
Since it is an M wave, it is necessary to smooth it.

Advances in MO8 technology have made it possible to implement band limiting and smoothing functions, that is, LSI filter technology.

A switched-toe capacitor filter (hereinafter referred to as SCF) combines a capacitor and a switch to create equal dynamic resistance, and the time constant is determined by this equal dynamic resistance and capacity.

Figure 2(a) shows the principle of equal dynamic resistance of SCF.

Switches 10 and 11 are connected between terminals 8 and 9, and a capacitor 12 (capacitance t11 is C) is connected to the ground potential at the midpoint thereof. Switch 1 is shown in Figure 2(b).
0y and 11 timing charts are shown. Figure 2 (b
), each switch is conductive in the @H” state. At time t = nT, the switch 10 is conductive, and a photovoltaic voltage is applied to the cover 12 via the switch 10 due to the voltage V applied to the terminal 8. Assuming that the time constant of the switch 10 and the capacitor 12 is sufficiently small relative to the time T, the charged charge Q is calculated as follows: Q=CV ・・・・・・・・・・・・・・・・・・
・Requests will be made in accordance with (1). , at time t#nT+,T, the switch 10 becomes non-conductive. After that, it is assumed that the switch 11 is turned on and the capacitor 12 is charged with a discharged charge Q from the terminal 9 by just before time t = n T -1-T (that is, the time constant of the capacitor 12 and the switch 11 is sufficient). ).

At this time, the charge Q flowing from the terminal 8 to the terminal 9 during the time T can be expressed as equation (1).1 The equivalent current 1e is I e #
Q/T = CV/T ・・・・・・・・・・・・・・・
・Requests will be made in accordance with (2). Equation (2) applies Ohm's law to fL, equal dynamic resistance fLe, and R6=V/I6-T/C...
......(3). As can be easily understood from equation (3), the time constant (1/C) is determined by the capacitance ratio and can therefore be obtained with high accuracy. Therefore, there is no need to use adjustment techniques to match the time constants.

Figure 3 is a block diagram showing a second example of the conventional CODEC, in which the cardiac function tl-LS is band-limited and smoothed using 8CF.
This is a conventional example incorporated into I.

FIG. 3 shows that in FIG. 1, a transmission filter 13 of 8CF is used to perform band control Vi on the encoder section 5 side, and the decoder section 6
On the other hand, a receiving filter 14fc based on 5CFvc has a smoothing function of 1.81.

In recent years, it has become possible to realize a reference voltage source using M (J8 1. There is a ΔVT type reference voltage source with MO8 and T transistors of the same polarity.The other one is NP.
N)? There is a bandgap type j-quasi-voltage source that extracts and uses the bandgap voltage of a PNPN digital transistor or a PNPN digital transistor. Furthermore.

In addition to this, bias conditions were used in which the relationship between the gate-source pressure VGII and the drain [iIn in the weak inversion layer region of the MOS transistor was an exponential function. There is also a reference voltage source, but it is not used much.

FIG. 4 is a block diagram showing an example of a conventional C0-1)EC system, in which a reference voltage source is built into the back of the LSI. In FIG. 4, what has been added from FIG. 3 is a reference voltage source 15 and an output voltage regulator 17 on the transmitting side, and a reference voltage source 16 and an output voltage regulator 18 on the receiving side.

As shown in FIG. 4, the reference voltage sources 15 and 16 and the outputs all! l Strain section 17. 18 is very useful because it allows adjustment of the transmitting and receiving sides to be performed independently, and gain adjustment can be performed independently of the transmitting and receiving sides. It helped with the tatami.

However, providing separate reference voltage sources for the transmitting side and the receiving side has the disadvantage of requiring twice the area and increasing the occupation rate τ of the L8I chip area.

Figure 5 is a block diagram showing a fourth example of a conventional CODEC, which was conceived as a method to minimize the LSI chip area within the allowable range of Talostalk characteristics on the transmitting and receiving sides. . In FIG. 5, a reference voltage image 19 and an output voltage adjustment section 20 are shared by the transmitting side and the receiving side 1d, and are supplied to the encoder section 5 and the decoder section 6. With this configuration, it was possible to provide a C0I)EC with a minimum area within the range allowed by the crosstalk characteristics.

However, as the standards for gain fluctuations on the transmitting and receiving sides become narrower, the configuration shown in FIG. 5 is approaching its limits. That is, as shown in FIG. The range of standards has become too narrow for variations in insertion loss that vary widely, and the standards for crosstalk characteristics have also become narrower. For this reason, there was a drawback that a very unstable element remained in stable production of C01) EC.

(Importance of the invention) The purpose of X=light is to eliminate the above-mentioned drawbacks, use a single reference voltage source, satisfy the intrusion loss fluctuation and crosstalk characteristic standards, and achieve stable performance. The object of the present invention is to provide an encoder-decoder that can be manufactured easily.

(Structure of the Invention) The uninvented encoder-decoder includes an encoder section, a decoder section, a single reference voltage source that supplies the same reference voltage to the encoder section and the decoder section, and a single reference voltage source that supplies the same reference voltage to the encoder section and the decoder section. a transmission filter consisting of an output acid pressure adjustment section for adjusting the output voltage of the voltage source; and a suite capacitor for manually limiting the band to the encoder section and smoothing the output of the decoder section, respectively. an encoder/decoder including a receive filter;
g filter or a gain adjustment section that includes a selection circuit consisting of a plurality of switches and a plurality of capacitors at the input stage of the reception filter and adjusts the gain of the encoder section or the decoder section according to the selection thereof; It consists of

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 6 is a block diagram showing a first embodiment of the invention.

This embodiment includes an encoder section 5, a decoder section 6, a reference rt voltage source 9 that supplies the same reference voltage to the encoder 7115 and the decoder section 6, and an output magnetic voltage of the reference voltage source 19. tl
--Transmission filter 1 consisting of an output pressure adjustment section 20 for adjusting the output voltage pA, and a suite filter for band limiting the input to the encoder section 5 and smoothing the output of the decoder section 6.
3 and a reception filter 14', a selection circuit including a plurality of switches and a plurality of capacitors is provided at the input stage of the reception filter 14', and the gain of the decoder section 6 is adjusted according to the selection thereof. It is configured by having an adjustment section 21.

In other words, what is different from the conventional example shown in FIG. 6 and shown in FIG. A receiving filter 14' incorporating a selection circuit consisting of a plurality of switches and a plurality of capacitors is provided in the receiver.

In FIG. 6, it is assumed that the reference voltage source 19 and the output adjustment section 20 are able to adjust the output of the encoder 5 within a desired range. Here, in the conventional configuration, no adjustment section was left on the receiving side, so it was impossible to adjust the gain on the receiving side. In the '2I-embodiment, by using the reception filter 14' and the gain adjustment unit 21, it is possible to adjust the gain on the reception side independently of the gain adjustment on the transmission side.

FIG. 7 is a partial detailed circuit diagram of this embodiment, showing an example of the input stage of the receiving 1M filter 14' by a switch group, a capacitor group, and an input stage amplifier 28.

Switches 22 and 23 are actual switches)-switches for capacitor operation, and the decoder 6 shown in broken lines
This constitutes the input stage of the PAM output wave. Switches 24, 25, 26 and 27 and capacitors 24', 25',
26' and 27' represent an input stage capacitance group and a switch group of the reception filter 14'. p1 In this embodiment, the gain adjustment section 21 is a 2-bit selection signal generation circuit (
Although not shown, it can be easily formed using known techniques. ). Switch 24°25.2
Both of the switches 6 and 27 are unrelated to the switched capacitor operation, and only the switches selected by the gain adjustment section 21 are conductive, and the remaining switches are always non-conductive. However, even if the gain adjustment step by the gain adjustment section 21 is rough, if possible, as a method of achieving a human power capacity equivalent to 2 bits, the human power capacity is realized by connecting two switches in parallel by simultaneously making them conductive. It is also possible. With this human power capacity, the gain V can be adjusted without changing the frequency characteristics.

In this way, the gain adjustment on the receiving side is performed independently of the reference voltage source 19 and the output voltage adjustment section 20 in the input stage of the receiving filter 14', so that the gain adjustment on the transmitting side and the receiving side can be finely adjusted. Therefore, a CODEC with excellent characteristics can be realized.

FIG. 8 is a block diagram showing a second embodiment of the present invention. The difference in FIG. 8 from the first embodiment shown in FIG. 6 is that a gain adjustment section 29 is provided in the sending 1M filter 13'. The human power capacity of the transmission filter 13' is
Similarly to the receiving filter 14' in the embodiment, by providing a switch group and a filter group, gain adjustment can be performed regardless of one frequency characteristic. This allows the gains to be adjusted independently on the transmitting side and the receiving side.

FIG. 9 is a block diagram showing a third embodiment of the invention. Figure 9 shows an example in which the characteristics were modified when the crosstalk characteristics of the output side and the receiver (*1itlJ) were deteriorated when the output impedance of the output pressure adjustment section 20 was high. The difference from the second embodiment shown is that buffer amplifiers 30 and 31 are provided independently at the output of the output width pressure g adjustment s2o.
By connecting the encoder section 5 and the decoder section 6, the crosstalk characteristics are improved.
Even when applied to FIG. 6, which shows the first embodiment, the same effect can be obtained.

In addition, in the description of the above embodiment, it can be realized by using either a ΔVT type or a bandcap type as the reference voltage source, and a publicly available polycrystalline silicon conductor can be used in the output magnetic pressure adjustment section or the gain adjustment section. A fuse using
It is clear that this can be done using an example of a metal conductor.

(Effects of the Invention) As described above in detail, according to the 2L invention, the encoder section and the decoder section can perform the O/U gain distortion independently, and the encoder section and the decoding section can be performed by the buffer amplifier. The encoder and decoder parts are separated, and an encoder/decoder that satisfies insertion loss variation and crosstalk standards and can be manufactured in one step is obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a first example of a conventional encoder-decoder, Figure 2 (a) is a switched cano (Schiff's principle diagram, diagram of Figure 2) is its timing chart, Figure 3 , 4th
5 and 5 respectively show the second example of the conventional encoder/decoder. Third
．． FIG. 6 is a block diagram showing the fourth example, and FIG. 6 is a block diagram showing the first embodiment of the present invention. FIG. 7 is a partial detailed circuit diagram thereof, and FIGS. 8 and 9 are respectively 83. of the present invention. It is a block diagram showing a fourth example. 1...Analog input terminal, 2...Digital output terminal, 3...Analog output terminal, 4
...Digital input terminal, 5...Encoder section, 6...Decoder section, 7.8.9...
・Terminal, 10.11... Switch, 12...
...Electrical connection, 13.13'...Transmission filter,
14.14'... Reception filter, 15.16.
...Reference Boshohara % 17.18 ... Output voltage source, 19 ... Reference voltage source, 20 ...
. . . Output voltage adjustment section, 21 . . . Gain adjustment section,
22~27...Switch, 24'~27'...
... Capacity, 28 ... Input stage amplifier, 29.
... Gain adjustment section, 30.31 ... Output buffer amplifier.阜1 loquat fight 2i C phantom Z side (Ref r-1 t=rz ding 1=nTf7- So + 梠half 1 mouth 2) Y-70% graduation θ shōg edict

Claims (2)

[Claims] (1) a single reference voltage source that provides the same reference voltage to the encoder section, the post-coder section and the decoder section;
an output pressure adjustment section that adjusts the output direct pressure of the semi-flexural pressure source;
In an encoder/decoder including a transmission filter and a reception filter each comprising a switched capacitor for manually limiting the band to the encoder section and smoothing the output of the encoder section, @iJ transmission is performed. At the input stage of the filter or the reception filter, a selection circuit including several switches and a plurality of capacitance switches is provided, and the gain of the encoder section or the IJ recording/decoder section is determined by the selection. An encoder-decoder comprising a gain adjustment unit for adjusting the gain adjustment unit. (2) An independent buffer amplifier f whose output voltage adjustment section supplies the same reference pressure to the encoder section and the imaginary signal section, respectively;
An encoder-decoder according to claim (1) comprising: