JP2001144824A - Digital receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that, when radio wave propagation condition is bad, filter characteristic is improved by increasing the number of taps of a channel separation filter of a digital receiver, thereby bringing the filter characteristic close to desired recovery output characteristic, but the number of taps of the channel separation light filter is usually fixed, also the number of tape is increased as a regular use condition and the filter characteristic property is improved, thus it can set so that better demodulation output is obtained even when the radio wave propagation condition is bad, but the throughput is increased and the power consumption of the receiver is increased. SOLUTION: An FFT arithmetic circuit 6 frequency-analyzes output data of an A/D converter 1 and the number of taps in channel separation filters 4a and 4b is adjusted, based on a frequency analysis result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radio receiving apparatus, and more particularly to a digital radio receiving apparatus capable of changing a digital signal processing method in the apparatus according to the state of a radio wave propagation path.

[0002]

2. Description of the Related Art With the development of digital signal processing technology in recent years, many examples of digital receivers for converting a received signal into a digital signal and demodulating the signal have been proposed in the field of wireless communication. FIG. 5 is a schematic diagram showing an example of a conventional digital receiving apparatus. As shown in the figure, the present digital receiving apparatus includes an A / D converter 1, mixers 21a and 21b, a local signal generator 22, and 90 °
A quadrature multiplier 2 including a phase shifter 23, low-pass filters 31a and 31b, a down-sampling circuit 32a,
32b, frequency separation devices 3a and 3b, channel separation filters 4a and 4b, and a demodulator 5. The functions of all the parts except for the A / D converter 1 in FIG. 1 are realized by software in a digital signal processing device such as a DSP (Digital Signal Processor). In FIG. 1, a received signal is converted into a digital signal by an A / D converter 1,
1a and 21b. In the mixer 21a, the received signal and the local signal from the local signal generator 22 are used, and in the mixer 21b, the received signal is
With the local signal from the local signal generator 22 whose phase has been shifted by 90 ° by the phase shifter, the frequency is converted into a baseband frequency, respectively, and the frequency decimation device 3a,
3b are output to the low-pass filters 31a and 31b.
The received signal is band-limited by the low-pass filters 31a and 31b,
a, 32b, the next-stage channel separation filter 4
The signals are down-sampled to a predetermined sampling rate and output to the channel separation filters 4a and 4b so as to reduce the processing amount of the filtering operation in steps a and b. In the channel separation filters 4a and 4b,
A channel signal is selected from the received signal, and the channel signal is demodulated by the demodulator 5 to obtain an output signal such as data, voice, and image.

In this receiving apparatus, as described above, all functions of the circuit configuration after the A / D converter are processed by the digital signal processing apparatus. At present, the processing capacity of general-purpose DSPs is that the sampling rate is high, and
It is about PS. Therefore, the orthogonal multiplier 2 and the frequency decimation device 3a whose processing amount exceeds 100 MIPS,
Generally, 3b is configured by a programmable hardware logic circuit (for example, an FPGA or the like) and performs signal processing, and the channel separation filters 4a and 4b and the demodulation unit 5 are generally configured by a DSP to perform signal processing. The channel separation filters 4a and 4b whose processing ratio in the DSP is much higher than that of the demodulation unit 5 are not inferior in performance as compared with the case where the characteristics of the digital filters are realized by analog filters. In order to obtain the characteristics, processing must be performed at a sampling frequency that is eight times the demodulation symbol frequency. The processing amount of the filter operation is given by the product of the sampling frequency and the number of taps of the filter.

[0004]

In the DSP of the receiving apparatus having the above configuration, for example, when E _b / N ₀ of the signal wave desired to be received is bad due to the radio wave propagation condition at that time,
By increasing the number of taps of the channel separation filters 4a and 4b, it is possible to improve the filter characteristics and to approach the desired demodulation output characteristics. However, usually
When the receiving device is used, the channel separation filter 4
The numbers of taps a and 4b are fixed. It is also possible to improve the filter characteristics by increasing the number of taps in a steady state of use so that a better demodulated output can be obtained even when the radio wave propagation condition is poor. However, there is a disadvantage that the power consumption increases. In other words, the constant use with an increased number of taps has a problem that wasteful power is consumed in a normal radio wave propagation state with little noise. SUMMARY An advantage of some aspects of the invention is to provide a digital wireless reception device capable of reducing a processing amount in a DSP without deteriorating reception performance.

[0005]

According to a first aspect of the present invention, a receiving input signal is converted to an A / D signal.
The digital signal output from the A / D converter is converted into a digital signal by the converter, the frequency of the digital signal is converted by the A / D converter, the sampling frequency is reduced by the downsampling unit, and a desired channel is output from the output of the downsampling unit by the digital filter. Isolate the signal,
In a digital receiving device for obtaining a demodulated signal from the channel signal by a demodulating unit, the number of taps of the digital filter unit is adjusted according to a radio wave propagation state of wireless communication. Claim 2
In the digital receiver of the first aspect, the output data of the A / D converter is frequency-analyzed by an FFT operation unit, and the number of taps of the digital filter unit is adjusted based on the frequency analysis result. It is characterized by having comprised so that it may perform. According to a third aspect of the present invention, in the digital receiving apparatus of the first aspect, the output data of the orthogonal multiplying means is frequency-analyzed by an FFT operation means, and taps of the digital filter means are provided based on the frequency analysis result. The number is adjusted.

According to a fourth aspect of the present invention, in the digital receiving apparatus of the first aspect, the output data of the down-sampling means is subjected to frequency analysis by FFT operation means, and based on the frequency analysis result, the digital filter means is used. The number of taps is adjusted. In the invention of claim 5, claim 1
In the digital receiving apparatus, a communication system having a data format for judging a radio wave propagation state of a wireless communication channel from the data demodulated by the demodulation means is adopted, and a radio communication is performed based on the data demodulated by the demodulation means. The radio wave propagation state of the road is determined, and the number of taps of the digital filter means is adjusted. Also,
According to a sixth aspect of the present invention, in the digital receiving apparatus according to the fifth aspect, as a parameter for judging a radio wave propagation state of a wireless communication path from data demodulated by the demodulation means,
A BER (Bit Error Rate) is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 is a schematic diagram of the configuration of a digital receiver according to the present invention. As shown in FIG. 1, the digital receiving apparatus includes an A / D converter 1, a quadrature multiplier 2 including mixers 21a and 21b, a local signal generator 22, and a 90 ° phase shifter 23, and a low-pass filter 31a. , 31b and downsampling circuits 32a, 32
b, frequency separation devices 3a and 3b, channel separation filters 4a and 4b, a demodulator 5, an FFT operation circuit 6, and a BER determination circuit 7. Among the above configurations, the configuration from the A / D converter 1 to the demodulator 5 is the same as that of the receiving apparatus shown in the schematic configuration diagram of FIG. 5, except that the channel separation filters 4a and 4b have a variable number of taps. , And have the same function, and the description of the common part is omitted.

In FIG. 1, a reception input is an A / D converter 1
Is converted into a digital signal and output to the orthogonal multiplier 2, and the output signal is input to the FFT operation circuit 6. The FFT operation circuit 6 constantly monitors the output signal of the quadrature multiplier 2 and analyzes the data (for example, the ratio E _b / N ₀ ), and determines the radio wave propagation state of the wireless communication path based on the analysis result. . Then, tap control signals based on the result of the determination are output to the channel separation filters 4a and 4b, and the control signals output the tap control signals.
The number of taps of b is changed, and the filter characteristics are changed.
If the radio wave propagation condition is bad, the filter characteristics can be improved by increasing the number of taps of the channel separation filters 4a and 4b from the standard number of taps, thereby improving the reception characteristics. On the other hand, when the radio wave propagation condition is good, the number of taps of the channel separation filters 4a and 4b can be reduced from the standard to make the filter characteristics moderate. In other words, if the receiving device is used under favorable radio wave propagation conditions, power consumption can be saved by reducing the standard number of taps from the above.

FIG. 2 is a diagram showing a second embodiment. The feature of this embodiment is that the mixer 21a of the quadrature multiplier 2 receives a signal for monitoring the radio wave propagation state input to the FFT operation circuit 6. , 21b are used.
FIG. 3 is a diagram showing a third embodiment. The feature of this embodiment is that a down-sampling circuit of the frequency decimation devices 3a and 3b is used as a signal for monitoring the radio wave propagation state input to the FFT operation circuit 6. The output signals of 32a and 32b are used. Each of the input signals is subjected to data analysis in the FFT operation circuit 6 in the same manner as described above to determine the radio wave propagation state of the wireless communication path, and the control signal based on the determination result is transmitted to the channel separation filter 4a,
4b, and the number of taps is adjusted. The method of adjusting the number of taps according to the radio wave propagation situation is the same as in the above example.

[0010] In the case of a communication system for performing communication in a data format in which the radio wave propagation state of a wireless communication path can be determined from the data demodulated by the demodulator 5, the following configuration may be adopted. For example, BER (Bit Error Rate)
In the case of a communication system in which the radio wave propagation state of the wireless communication path can be determined by the above, the demodulated output of the demodulator 5 is output to the BER determination circuit 7 as shown in FIG. The BER determination circuit 7 analyzes the BER of the input signal to determine the radio wave propagation state of the wireless communication path, and outputs a control signal based on the determination result to the channel separation filters 4a and 4b to adjust the number of taps. Is performed. The method of adjusting the number of taps according to the radio wave propagation situation is the same as described above.

As described above, in the present receiver, when the radio wave propagation condition is poor, the channel separation filters 4a, 4a
The sampling frequency and the number of taps are increased by using the number of taps of b from the standard number of taps, or by reducing the number of standard taps when using the receiver in a good radio wave propagation situation. , The processing amount of the channel separation filters 4a and 4b in the DSP can be reduced. It should be noted that the present invention is not limited to the above embodiment, but includes all those that control the number of taps of the channel separation filter of the digital receiving apparatus according to the radio wave propagation situation. May be combined.

[0012]

As described above, according to the present invention,
The radio wave propagation state is determined by the FFT operation circuit or the BER determination circuit, and based on this determination, the number of taps of the channel separation filter can be reduced without deteriorating the reception performance. As a result, the processing amount of the DSP can be reduced, which can greatly contribute to reduction of power consumption in the receiving device. It is also possible to add other functions with extra processing capacity.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a digital receiving apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the digital receiver according to the present invention;

FIG. 3 is a schematic configuration diagram showing a third embodiment of the digital receiving apparatus according to the present invention.

FIG. 4 is a schematic configuration diagram showing a fourth embodiment of the digital receiving apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional digital receiver.

[Explanation of symbols]

1. A / D converter, 2. Quadrature multiplier, 3a, 3
b frequency decimation device, 4a, 4b channel separation filter, 5 demodulator, 6 FFT operation circuit, 7 BER determination circuit, 21a, 21b mixer, 22 local signal generator , 23 ... 90
° Phase shifter, 31a, 31b, low-pass filter,
32a, 32b ... downsampling circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 27/00 H04L 27/00 C

Claims (6)

[Claims] An A / D conversion means converts a received input signal into a digital signal, a digital signal output from the A / D conversion means is frequency-converted, and a sampling frequency is reduced by a down-sampling means. In a digital receiving apparatus which separates a desired channel signal from an output of the sampling means by a digital filter means and obtains a demodulated signal from the channel signal by a demodulation means, the number of taps of the digital filter means is changed according to a radio wave propagation state of wireless communication. A digital receiving apparatus characterized in that it is configured to adjust. 2. An output data of said A / D conversion means is FFT
2. The digital receiving apparatus according to claim 1, wherein a frequency analysis is performed by an arithmetic unit, and the number of taps of said digital filter unit is adjusted based on the frequency analysis result. 3. An output data of said orthogonal multiplication means is frequency-analyzed by an FFT operation means, and the number of taps of said digital filter means is adjusted based on said frequency analysis result. Item 1. The digital receiving device according to Item 1. 4. The apparatus according to claim 1, wherein the output data of said downsampling means is frequency-analyzed by FFT operation means, and the number of taps of said digital filter means is adjusted based on the frequency analysis result. Item 1
A digital receiver as described in the above. 5. A communication system having a data format for judging a radio wave propagation state of a radio communication channel from data demodulated by said demodulation means, and a radio communication path is provided based on the data demodulated by said demodulation means. 2. The digital receiving apparatus according to claim 1, wherein the radio wave propagation condition is determined and the number of taps of said digital filter means is adjusted. 6. A parameter B for judging a radio wave propagation state of a radio communication channel from data demodulated by the demodulation means.
6. The digital receiving apparatus according to claim 5, wherein ER (Bit Error Rate) is used.