JP2001332975A - Delta/sigma modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a delta/sigma modulator capable also of dealing with plural communication modes. SOLUTION: While using a delta/sigma modulator 100 provided with a communication mode deciding part 60 for deciding plural communication modes and a coefficient setting circuit 70 for setting the gain coefficient of a gain controller and further the coefficient of the transfer function a filter 80 according to the decided communication mode, so that plural communication modes can be dealt with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a delta-sigma modulator used for obtaining a high resolution in a communication field,
The present invention relates to a filter device and a communication system using the same.

[0002]

2. Description of the Related Art A conventional delta-sigma modulator and a communication system using the same will be described with reference to FIG. FIG.
FIG. 1 is a block diagram showing a conventional fourth-order bandpass delta-sigma modulator.

In FIG. 3, reference numerals 1 to 4 denote loop filters operating at a sampling period sufficiently larger than a desired signal frequency, 10 to 13 are adders, 20 to 30 are gain adjusters, 40 is a quantizer, and 41 is a quantizer. It is a DA converter.

[0004] The operation of the delta-sigma modulator configured as described above will be described.

First, an input signal 50 is supplied to gain adjusters 20-3.
0, the gain of the amplitude is adjusted.
13 are subjected to an addition process.
4 are subjected to integration processing, and are converted into 1-bit digital signals by the quantizer 40, and appear at the 1-bit output terminal 51 as 1-bit digital signals having the same period as the sampling period.

The 1-bit digital signal appearing at the 1-bit output terminal 51 is converted from a digital signal to an analog signal by the DA converter 41, and is adjusted by the gain adjusters 20 to 23.
After the gain is adjusted, the data is fed back to the adders 10 to 13.

In this delta-sigma modulator, the input is U (z), the output is V (z), and the quantization noise is E (z).
(Z), the transfer function of the signal is G (z), and the transfer function of the quantization noise is HE (z), the output V (z) is: V (z) = G (z) · U (z) + H (Z) · E (z) (1) The signal transfer function G (z) and the quantization noise transfer function HE (z) are designed to be suitable for the system as shown in FIG. By reflecting the quantization noise in the coefficient of the gain adjuster, the quantization noise can be shifted to a higher frequency band, and a bandpass characteristic for improving the SN ratio in a desired frequency band can be provided.

In FIG. 4, the noise shaping characteristic is designed to be maximum at the intermediate frequency f0. f
n is a Nike straight.

FIG. 5 shows the frequency characteristics of a 1-bit digital output, which is designed to obtain bandpass characteristics at an intermediate frequency of the system.
The peak in the notch region in FIG. 5 indicates the signal of the intermediate frequency carrier.

In FIG. 5, the frequency is a relative value standardized by the sampling frequency, and the Nyquist rate is represented by 0.5. Such a band-pass delta-sigma modulator is also described in JP-A-11-177358.

[0011]

However, in the above-mentioned conventional configuration, since the gain coefficient in the gain adjuster is fixed, it cannot cope with a plurality of communication systems having different intermediate frequencies and signal bandwidths to be subjected to noise shaping. Had the disadvantage that

The present invention has been made in view of the above points, and has an intermediate frequency,
An object of the present invention is to provide a delta-sigma modulator, a filter device, and a communication system using the same, which can support a plurality of communication systems having different signal bandwidths.

[0013]

In order to achieve the above object, a delta-sigma modulator according to the present invention is a delta-sigma modulator having a signal converter for converting an input signal into a 1-bit signal. It is characterized by comprising means for determining a communication mode, and means for setting a gain coefficient of a gain adjuster of the signal conversion unit according to the determined communication mode.

With this configuration, a transfer function of a signal and a noise corresponding to a desired communication mode from a plurality of communication modes can be realized, so that a desired noise shaping characteristic can be obtained.

According to another aspect of the present invention, there is provided a filter for processing a digital signal subjected to delta-sigma modulation, means for determining a plurality of communication modes, and setting a transfer function coefficient of the filter according to the determined communication mode. Means for performing the operation.

With this configuration, a filter transfer function corresponding to a desired communication mode can be realized from a plurality of communication modes, so that a delta-sigma modulated digital signal corresponding to a desired communication mode can be processed.

Further, the communication system of the present invention includes a conversion means for converting an input signal into a delta-sigma modulated digital signal, a filter for processing the delta-sigma modulated digital signal, and a plurality of communication modes. Means, and means for setting a gain coefficient of a gain adjuster of the conversion means and a coefficient of a transfer function of the filter according to the determined communication mode.

According to this configuration, a communication system corresponding to a plurality of communication modes can be realized.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention. The communication system includes a delta-sigma modulator and a filter.

In FIG. 1, reference numeral 100 denotes a delta-sigma modulator. The delta-sigma modulator 100 includes loop filters 1-4, adders 10-13, and gain adjusters operating at a sampling period sufficiently larger than a desired signal frequency. 20-3
0, a quantizer 40, a DA converter 41, a communication mode determination unit 60, and a coefficient setting circuit 70. 80
Is a filter, and 90 is an output terminal of the filter 80.

The operation of the communication system configured as described above will be described.

First, the communication mode determining unit 60 determines one communication mode from a plurality of communication modes.

Next, the coefficient setting circuit 70 sets a predetermined gain coefficient in the gain adjusters 20 to 30 according to the determined mode. Digital sigma modulator 100
Is the same as that shown in the conventional example, and a detailed description thereof will be omitted.

The coefficient setting circuit 70 also sets the coefficient of the filter transfer function of the filter 80 according to the communication mode. The filter 80 outputs a 1-bit signal appearing at the 1-bit output terminal 51.
It performs filter processing and thinning processing of a digital signal of bits, and needs to set a coefficient corresponding to a characteristic corresponding to a communication system. The processing result is output from the output terminal 90.

The signals output from the output terminal 90 include:
Further, orthogonal demodulation processing and baseband processing are performed.

With the above configuration, the gain coefficient of the gain adjuster can be set according to the determined communication system.
G (z) and H (z) in the above equation (1) V (z) = G (z) · U (z) + H (z) · E (z) indicate the characteristics corresponding to the determined communication mode. It can be set to have a noise shaping characteristic corresponding to a plurality of communication modes.

FIG. 2 shows a G corresponding to a communication mode in which the intermediate frequency f1 in the conventional example is twice the frequency f0 in the conventional example.
9 shows frequency characteristics of (z) and H (z).

By switching the coefficient setting corresponding to the communication mode in this manner, both the characteristics shown in FIGS. 2 and 4 can be realized.

In the present embodiment, the characteristics of the intermediate frequency are changed, but the frequency band can be changed according to the communication mode. Further, the present invention can be applied not only to delta-sigma conversion of an intermediate frequency but also to baseband signal processing in a direct conversion method or the like. The configuration of the circuit block is not limited to this.

The filter coefficient setting storage includes SR
Memory elements such as AM, DRAM, and EEPROM can be used.

[0032]

As described above, the delta-sigma modulator of the present invention has a plurality of communication modes by providing the setting means for setting the gain coefficient of the gain adjuster of the signal conversion unit in accordance with the determined communication mode. Therefore, since a transfer function of a signal and a noise corresponding to a desired communication mode can be realized, desired noise shaping characteristics can be obtained, and excellent delta-sigma modulation that can support a plurality of communication modes can be realized.

Further, the filter device of the present invention can realize a filter transfer function corresponding to a desired communication mode from a plurality of communication modes by setting a coefficient of a transfer function of the filter according to the determined communication mode. A delta-sigma modulated digital signal corresponding to a desired communication mode can be processed.

Further, the communication system of the present invention can support a plurality of communication modes by setting the gain coefficient of the gain adjuster of the conversion means and the coefficient of the transfer function of the filter according to the determined communication mode. An excellent communication system can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of a transfer function of a delta-sigma modulator of the communication system of FIG. 1;

FIG. 3 is a block diagram showing a conventional fourth-order bandpass delta-sigma modulator.

FIG. 4 is a frequency characteristic diagram of a transfer function of the delta-sigma modulator of FIG. 3;

FIG. 5 is a frequency characteristic diagram of a 1-bit output in the delta-sigma modulator of FIG. 3;

[Explanation of symbols]

 1-4 loop filter 10-13 adder 20-30 gain adjuster 40 quantizer 41 DA converter 60 communication mode determination unit 70 coefficient setting circuit 80 filter 100 delta sigma modulator

Claims (3)

[Claims] 1. A delta-sigma modulator comprising a signal converter for converting an input signal into a 1-bit signal, comprising: means for determining a plurality of communication modes; and a gain of the signal converter according to the determined communication mode. A delta-sigma modulator comprising means for setting a gain coefficient of a regulator. 2. A filter for processing a digital signal subjected to delta-sigma modulation, means for determining a plurality of communication modes, and setting means for setting a coefficient of a transfer function of the filter in accordance with the determined communication mode. A filter device characterized by the above-mentioned. 3. A converter for converting an input signal into a delta-sigma-modulated digital signal, a filter for processing the delta-sigma-modulated digital signal, a means for determining a plurality of communication modes, and the determined communication. A communication system comprising: means for setting a gain coefficient of a gain adjuster of the conversion means and a coefficient of a transfer function of the filter according to a mode.