JP2001211213A - Demodulation method, demodulation circuit and mobile wireless equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in the conventional demodulation method and demodulation circuit that require AFC control taking long time for correction of a data error caused by a frequency shift, and to provide a demodulation method and demodulation circuit that can correctly receive and demodulate data, so as to dispense with the AFC control and reduce the reception time, and to provide a mobile wireless equipment. SOLUTION: In this demodulation method and demodulation circuit and the mobile wireless equipment, a plurality of quadrature demodulation sections 2 is provided in parallel, each local oscillator 21 in the inside of each quadrature demodulation section 2 outputs a plurality of local oscillation frequencies corrected in response to the estimated frequency shift, each demodulator 25 in the inside of each quadrature demodulation section 2 acquires demodulated data, an error rate measurement section 3 connected to each quadrature demodulation section 2 individually measures the error rate of the demodulated data outputted from each demodulation section 25 and a demodulation data selections selects and outputs the demodulation data, whose error rate is minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio signal demodulation method, a demodulation circuit, and a portable radio device. More particularly, the present invention can correctly receive and demodulate radio signals without performing AFC control, and can reduce the time required to receive radio waves. The present invention relates to a demodulation method, a demodulation circuit, and a portable wireless device.

[0002]

2. Description of the Related Art A conventional demodulation method and demodulation circuit will be described with reference to FIG. FIG. 3 is a configuration block diagram of a conventional demodulation circuit. As shown in FIG. 3, the conventional demodulation circuit includes an antenna for receiving a signal, a frequency conversion unit 1 ',
And a quadrature demodulation unit 2 '.

[0005] Inside the frequency converter 1 ', there are provided an amplifier 11a, an amplifier 11b, an amplifier 14, a local oscillator 12a', a local oscillator 12b ', a mixer 13a, and a mixer 13b.

[0004] Each component in the frequency converter 1 'will be specifically described. The amplifiers 11a, 11b, and 14 amplify received waves, and include local oscillators 12a 'and 12a'.
b 'is an oscillator having a function of changing the oscillation frequency in accordance with an external frequency correction control signal, and the mixers 13a and 13b compare the received wave with the frequency output from the local oscillator 12a' or 12b '. Mixing and frequency conversion.

Further, a local oscillator 21 ', a 90-degree phase shifter 22, a mixer 23, a mixer 24, and a demodulator 25' are provided inside the quadrature demodulator 2 '.

Each component in the quadrature demodulation unit 2 'will be specifically described. The local oscillator 21 'is an oscillator having a frequency changing function similar to that of the above-described local oscillators 12a' and 12b '.
This shifts the phase of the signal input from 1 'by 90 degrees.

The mixer 24 mixes (combines) the received signal input from the frequency converter 1 'with the oscillation frequency of the local oscillator 21', and in-phase with the oscillation frequency (I-phase).
And outputs the baseband signal of the
Represents the received signal input from the frequency converter 1 'and 90 °
The signal from the phase shifter 22 is mixed to output a (Q phase) baseband signal orthogonal to the oscillation frequency.

The demodulator 25 'demodulates the I-phase and Q-phase baseband signals to judge the symbols and outputs demodulated data. In addition, the demodulator 25' shifts the frequency between the baseband signal and the oscillation frequency. And a frequency correction control signal for correcting the
b 'and 21'.

Next, the operation of the conventional demodulation circuit will be described with reference to FIG. When a signal is received by the antenna, first, the amplifier 11a of the frequency converter 1 'amplifies the received signal, and the received wave and the local oscillator 12a are amplified by the mixer 13a.
The oscillation frequency output from a 'is mixed with the oscillation frequency to reduce the frequency. The amplifier 11b and the mixer 13b repeat the same operation to convert the frequency from a high frequency to a low frequency. This low frequency signal is amplified by the amplifier 14 and output.

In the quadrature demodulation unit 2 ', when a signal is input from the frequency conversion unit 1', the signals are mixed with the oscillation frequency of the local oscillator 21 'by the mixers 24 and 23, and the bases of the I-phase and the Q-phase, respectively. Band signal and demodulator 2
5 ′ demodulates the baseband signal to determine a symbol,
Output demodulated data.

Here, when the demodulator 25 'obtains demodulated data, an error occurs in the demodulated data due to a frequency deviation of a received signal, a frequency deviation of a local oscillator, or the like. To correct this, the demodulator 25 'detects a frequency shift and outputs a frequency correction control signal for correcting the oscillation frequency of the local oscillators 12a', 12b ', 21' to each local oscillator. AFC control (Auto Frequency Control
l) had done.

A conventional technique using quadrature demodulation is disclosed in Japanese Unexamined Patent Application Publication No. 11-3131 published November 9, 1999.
No. 17, "Frequency control method, quadrature detection circuit and FSK receiver" (applicant: Kokusai Electric Inc., inventor: Hisashi Kawai). This prior art includes means for detecting a rotation direction of a signal point of a received signal, and means for detecting an amount of rotation of a signal point of the received signal, and a determination circuit determines a symbol based on these, and standardizes the symbol. By comparing with an ideal signal output from the circuit, the AFC circuit is used as a frequency control method for controlling the frequency of the signal output from the VCO, a quadrature detection circuit, and an FSK receiver.
The VCO can be controlled appropriately.

[0013]

In the conventional demodulation method and demodulation circuit, however, the AFC control must be performed to correct the oscillation frequency of the local oscillator in order to correctly demodulate the received signal. There is a problem that it takes time to correct the frequency to an appropriate frequency, and correct correction cannot be performed without sufficient reception input.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a demodulation method and a demodulation circuit capable of correctly performing reception and demodulation without performing AFC control and shortening the reception time by eliminating the time required for frequency correction. And a portable wireless device.

[0015]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems of the prior art is to demodulate a received signal at a plurality of local oscillation frequencies corresponding to a frequency shift assumed in advance, and demodulate the demodulated signal. The demodulation method measures the data error rate and selects the demodulated data with the minimum error rate. The demodulation method can correctly receive and demodulate the data without performing AFC control, and shortens the time required for frequency correction by eliminating the time required for frequency correction. be able to.

Further, the present invention provides a receiving means for receiving a radio signal, a demodulating means for demodulating a signal received at a plurality of local oscillation frequencies corresponding to a frequency shift assumed in advance, and a demodulating means for demodulating each demodulated data. The demodulation circuit has an error rate measuring means for measuring an error rate, and a demodulation data selecting means for selecting and outputting demodulated data having a minimum error rate. The demodulation circuit can receive and demodulate correctly without performing AFC control. The required time is not required, and the reception time of the radio wave can be reduced.

In the present invention, the demodulating means, the error rate measuring means and the demodulated data selecting means may be realized by a DSP. Further, the present invention can be a portable wireless device including the demodulation circuit described above.

[0018]

Embodiments of the present invention will be described with reference to the drawings. Note that the function realizing means described below may be any circuit or device as long as the function can be realized, and some or all of the functions may be realized by software. is there. Further, the function realizing means may be realized by a plurality of circuits, or the plurality of function realizing means may be realized by a single circuit.

In the demodulation method according to the present invention, a received signal is demodulated at a plurality of local oscillation frequencies according to a frequency shift assumed in advance, and an error rate of demodulated demodulated data is measured.
Since the demodulated data with the lowest error rate is selected, the AF
Even if C control is not performed, reception and demodulation can be performed correctly, and the time required for frequency correction is not required, and the reception time of radio waves can be reduced.

A demodulation circuit according to the present invention comprises: a receiving means for receiving a radio signal; a demodulating means for demodulating signals received at a plurality of local oscillation frequencies corresponding to a frequency shift assumed in advance; Since it has an error rate measuring means for measuring an error rate of data and a demodulation data selecting means for selecting and outputting demodulated data having the minimum error rate, reception and demodulation can be performed correctly without performing AFC control, and frequency correction is required. This eliminates the need for time and shortens the time required to receive radio waves.

First, a demodulation circuit according to a first embodiment of the present invention will be described. FIG. 1 is a configuration block diagram of a demodulation circuit (first circuit) according to the first embodiment of the present invention. Parts having the same configuration as in FIG. 3 are described with the same reference numerals. As shown in FIG. 1, the demodulation circuit according to the first embodiment of the present invention includes a frequency conversion unit 1 for converting a received signal into a low frequency, and a plurality of quadrature demodulations for performing quadrature detection and outputting demodulated data. Parts 2a, 2b, ..., 2
x and error rate measuring units 3 a and 3 connected to each quadrature demodulation unit 2 and measuring the error rate of demodulated data from each quadrature demodulation unit 2.
, 3x, and a demodulation data selection unit 4 for selecting and outputting one data from the data input from each quadrature demodulation unit 2.

Here, the frequency conversion unit 1 corresponds to the receiving means of the claims, the quadrature demodulation unit 2 corresponds to the demodulating means of the claims, and the error rate measuring unit 3 corresponds to the error rate measuring means of the claims. The demodulation data selection section 4 corresponds to the demodulation data selection means in the claims.

Each component of the first circuit will be specifically described. First, the frequency conversion unit 1 converts a reception frequency to a low frequency as in the related art.
11 b, a local oscillator 12 and a mixer 13. These are all exactly the same as in the prior art, and will not be described.

The quadrature demodulation units 2a,..., 2x, like the conventional quadrature demodulation unit 2 ', quadrature demodulate the signal from the frequency conversion unit 1 and output demodulated data. , 2x, each of the quadrature demodulation units 2a,..., 2x performs demodulation at an oscillating frequency corrected in accordance with a frequency shift assumed in advance.

That is, in the first circuit, each quadrature demodulator 2
a,..., 2x perform demodulation using different oscillation frequencies, respectively. Instead of using the local oscillator of one quadrature demodulation unit in accordance with the frequency of the received signal as in the related art, It has a plurality of quadrature demodulators that have been frequency-corrected corresponding to different frequencies.

Here, the configuration of the quadrature demodulation unit 2 will be specifically described using the quadrature demodulation unit 2a as an example. The configuration of the quadrature demodulation unit 2a is almost the same as that of the prior art. A mixer 24a that outputs an I-phase baseband signal, a mixer 23a that mixes a signal from the frequency converter 1 with a signal from the phase shifter 22a and outputs a Q-phase baseband signal, And a demodulator 25a that outputs a demodulated data by performing symbol determination based on the Q-phase baseband signal.

Then, as a feature of the first circuit, the local oscillator 21a oscillates, as a specific frequency, a frequency corrected corresponding to one of frequency shifts assumed in advance. Further, the demodulator 25a is greatly different from the conventional demodulation circuit in that the AFC control for correcting the oscillation frequency of the local oscillator 21a is not performed.

The internal configuration of the quadrature demodulation units 2b,..., 2x is the same as that of the quadrature demodulation unit 2a, but the oscillation frequency output from the local oscillator 21 is different. That is, each of the local oscillators 21b,..., 21x is corrected to oscillate at a different frequency so that reception and demodulation can be accurately performed in response to various frequency shifts assumed in advance.

Thus, the local oscillators 21a,.
It is expected that any of the oscillation frequencies of x will coincide with the reception frequency, and the demodulated data from the quadrature demodulation unit 2 including the local oscillator 21 is transmitted to all quadrature demodulation units 2a,.
It is considered that the error is the least among the demodulated data from x. The present invention utilizes this fact to select the optimum demodulated data.

The error rate measuring section 3 measures the error rate of the demodulated data demodulated by the demodulator 25 of the quadrature demodulating section 2,
This is output to the demodulation data selection unit 4. The error rate measuring units 3b,..., 3x are the same as the error rate measuring unit 3a.

The demodulation data selection section 4 measures the error rates individually from the demodulation data demodulated by the quadrature demodulation sections 2a,..., 2x by the error rate measurement sections 3a,. Based on the output error rate, demodulated data having the minimum error rate is selected and output.

Thus, the first circuit can easily obtain correct received data without performing AFC control for correcting the oscillation frequency of the local oscillator in accordance with the received frequency.

Next, the operation of the first circuit will be described with reference to FIG. The signal received from the antenna is shown in FIG.
As in the conventional demodulation circuit shown in FIG.
, And is converted from a high frequency to a low frequency by the frequency conversion unit 1, and is output in parallel to the plurality of orthogonal demodulation units 2a,.

Then, each quadrature demodulation unit 2i (i = a to x)
Then, similarly to the quadrature demodulation unit 2 'in the conventional demodulation circuit, the input received signal is mixed with the oscillation frequency of the local oscillator 22i provided in the quadrature demodulation unit 2i, demodulated, and demodulated from the demodulator 25i. Demodulated data is output. As described above, the oscillation frequency of the local oscillator 22i is a frequency corrected so as to correspond to a frequency shift assumed in advance.

Here, the demodulated data from the quadrature demodulation unit 2i is branched and inputted to the demodulation data selection unit 4 and the error rate measurement unit 3i. And outputs the error rate as a measurement result to the demodulation data selection unit 4.

Thus, the demodulated data from the orthogonal demodulation units 2a,..., 2x and the error rates from the error rate measurement units 3a,. Become. Then, the demodulated data selection unit 4 selects and outputs the demodulated data having the minimum error rate from all the inputted demodulated data. The operation of the first circuit is performed in this manner.

According to the demodulation circuit (first circuit) according to the first embodiment of the present invention, the quadrature demodulation unit including the frequency oscillator 22 that has performed the frequency correction corresponding to the frequency shift assumed in advance. 2 in parallel, and each quadrature demodulation unit 2a,
, 2x demodulate the received signal using different oscillation frequencies, and the error rate measurement unit 3 connected to the quadrature demodulation unit 2
Since the error rate of the demodulated data from the quadrature demodulator 2 is measured and output to the demodulated data selector 4, the demodulated data selector 4 selects and outputs the demodulated data having the minimum error rate. The demodulation data demodulated at the oscillation frequency closest to the reception frequency can be selected from among the outputs of the plurality of quadrature demodulators 2, and the demodulation data can be correctly received and demodulated without performing the AFC control. Becomes unnecessary,
There is an effect that the reception time can be reduced.

Next, another embodiment (second embodiment) of the present invention will be described. The demodulation circuit (second circuit) according to the second embodiment of the present invention is the demodulation circuit (second circuit) shown in FIG.
In the circuit shown in FIG. 2, a portion composed of a plurality of orthogonal demodulation units 2, a plurality of error rate measurement units 3, and a demodulation data selection unit 4 is denoted by D
Replaced by SP (Digital Signal Processor), DSP
The function is realized by the processing described above.

The configuration of the demodulation circuit according to the second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a configuration block diagram of a demodulation circuit (second circuit) according to the second embodiment of the present invention. As shown in FIG. 2, the second circuit includes a frequency converter 1 similar to the first circuit, and an A / D converter 5 and a DSP 6, which are characteristic parts of the second circuit.

Each component will be specifically described. A
The / D converter 5 converts the received signal converted to low frequency into digital data and outputs the digital data to the DSP 6.

The DSP 6 includes the quadrature demodulation units 2a,..., 2x of the first circuit shown in FIG. 1, the error rate measurement units 3a,.
And implements the function of the portion composed of

Specifically, the DSP 6 includes a plurality of demodulation processing means (not shown) for realizing the function of the quadrature demodulation unit 2 of the first circuit, and the function of the error rate measurement unit 3 of the first circuit. And a demodulation data selection unit (not shown) that realizes the function of the demodulation data selection unit 4 of the first circuit.

Each demodulation processing means of the DSP 6 has parameters corresponding to different frequency deviations in consideration of various frequency deviations assumed in advance, and performs demodulation processing in parallel. .

As a result, the DSP 6 can operate the A / D converter 5
The digital data input from is demodulated in parallel in consideration of a plurality of types of frequency shifts assumed in advance, and the demodulated data having the minimum error rate is selected and output from the obtained plurality of demodulated data. It has become.

According to the demodulation circuit according to the second embodiment of the present invention, the A / D converter 5 and the DSP 6 are provided, and the first
Since the functions realized by the quadrature demodulation unit 2, the error rate measurement unit 3, and the demodulation data selection unit 4 of the demodulation circuit according to the second embodiment are realized by the DSP 6, the first embodiment In addition to the effect of the embodiment, there is an effect that the number of parts can be reduced, and power consumption and cost can be reduced.

[0046]

According to the present invention, a received signal is demodulated at each of a plurality of local oscillation frequencies corresponding to a frequency shift assumed in advance, and an error rate of each demodulated data is measured. Since the demodulation method of selecting the demodulated data is used, the reception and demodulation can be performed correctly without performing the AFC control, and the time required for the frequency correction is unnecessary, and the reception time of the radio wave can be shortened.

According to the present invention, a demodulating means for demodulating a signal received by a receiving means at a plurality of local oscillation frequencies corresponding to a frequency shift assumed in advance, and an error for measuring an error rate of each demodulated demodulated data. Since the demodulation circuit includes a rate measurement unit and a demodulation data selection unit that selects and outputs demodulated data having the minimum error rate, reception and demodulation can be performed correctly without performing AFC control, and the time required for frequency correction is eliminated. There is an effect that the reception time of radio waves can be reduced.

Further, according to the present invention, the demodulating means, the error rate measuring means, and the demodulated data selecting means are constituted by a demodulating circuit realized by a DSP, so that the number of parts is reduced, and power consumption and cost are reduced. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a demodulation circuit (first circuit) according to a first embodiment of the present invention.

FIG. 2 is a configuration block diagram of a demodulation circuit (second circuit) according to a second embodiment of the present invention.

FIG. 3 is a configuration block diagram of a conventional demodulation circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Frequency conversion part, 11a ... Amplifier, 11b ... Amplifier, 12 ... Local oscillator, 13 ... Mixer, 2 ... Quadrature demodulation part, 21 ... Local oscillator, 22 ... 90 degree phase shifter,
23 ... mixer, 24 ... mixer, 25 ... demodulator,
3: Error rate measurement unit, 4: Demodulation data selection unit, 5: A
/ D converter, 6 ... DSP

Claims (4)

[Claims] A demodulated signal is demodulated at each of a plurality of local oscillation frequencies according to a frequency shift assumed in advance, and an error rate of each demodulated data is measured. A demodulation method characterized by selecting. 2. A receiving means for receiving a radio signal, a demodulating means for demodulating the received signal at a plurality of local oscillation frequencies according to a frequency shift assumed in advance, and an error rate of each demodulated data. And a demodulation data selecting means for selecting and outputting demodulated data having the minimum error rate. 3. A demodulation means, an error rate measurement means, and a demodulation data selection means realized by a DSP, and an A / D conversion means for converting a signal from the reception means into a digital signal and outputting the digital signal to the demodulation means. The demodulation circuit according to claim 2, wherein: 4. A portable wireless device comprising the demodulation circuit according to claim 2.