JP2001308946A - Multi-pilot tone detection method and matching filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-pilot tone detection method and a matching filter by which a filter circuit scale can be reduced if a preamble signal is composed of a multi-pilot tone signal. SOLUTION: A multi-pilot tone signal 32 is given to filters 1, 2, 3, where each of pilot tone signals 30, 30..., 30 is separated. Each of the pilot tone signals 30, 30..., 30 separated by the filters 1, 2, 3 are given to multipliers 4, 5, 6 where the frequency of the pilot tone signals 30, 30..., 30 is converted into the same frequency. Since the output signal from the multipliers 4, 5, 6 has the same frequency, an output signal from an adder 7 is the pilot tone signal 30. Thus, a single correlation detection filter 8 in matching with the output signal from the adder 7 detects the pilot tone signal 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matched filter technology for detecting a multi-pilot tone signal, and more particularly, to a multi-filter capable of reducing the circuit scale of a filter when a preamble signal is composed of a multi-pilot tone signal. The present invention relates to a pilot tone detection method and a matched filter.

[0002]

2. Description of the Related Art Conventionally, in a matched filter for detecting a multi-pilot tone signal, in order to demodulate a burst signal, a synchronization process for detecting the head of the burst signal is required. In many cases, a fixed preamble is added to the head of a burst signal for the purpose of facilitating synchronization processing. Since the preamble signal is fixed for each burst signal, preamble detection can be performed by using a filter matched to the preamble signal (first related art).

In addition, an FIR filter (Finite I)
As a conventional technique for reducing the circuit scale of a pulse response filter (a finite response filter), there is a technique described in Japanese Patent Application Laid-Open No. 9-98069 (second conventional technique). In other words, the second prior art employs an FIR in which the circuit scale of the tap coefficient processing unit is reduced while maintaining the same filter characteristics as the prior art.
And a shift register having m stages for inputting and shifting an input digital signal in synchronization with a clock ck, and dividing each stage of the shift register into a preceding stage and a succeeding stage. A selector for alternately selecting and outputting the output of the previous stage and the output of the subsequent stage by the double frequency clock ck2; A delay register for temporarily storing the output of the tap coefficient processing unit and delaying the output by one clock ck2 for output, and adding the output of the delay register and the output of the tap coefficient processing unit to output the operation result for all stages of the shift register And an output register that outputs the operation result from the adder as a filter output in synchronization with the clock ck. Seen, and to process the tap coefficients by dividing each stage of the shift register to the front and rear stages. The tap coefficient processing unit includes a tap coefficient ROM for storing a preset tap coefficient, and outputs of the preceding and succeeding stages of the shift register and the tap coefficient ROM alternately selected by selectors corresponding to the respective stages of the shift register. A multiplier that multiplies the tap coefficient data from
And a full adder for summing the outputs of the multipliers, wherein the number of multipliers is a number corresponding to approximately half of each stage of the shift register. Further, as a tap coefficient processing unit, all the operation results to be obtained by performing tap coefficient processing on the output of the shift register are stored, and the outputs of the previous stage and the subsequent stage of the shift register are stored by alternately using them as addresses. An operation result R in which the operation result is read out
OM is provided.

Thus, the output of the shift register is used for multiplication by half using a selector having a small circuit scale, so that the multiplier having a large circuit scale is reduced to approximately half, and the storage capacity of the tap coefficient ROM is reduced. And the number of data additions of the full adder can be greatly reduced,
The same filter characteristics as those of the prior art can be obtained, and the circuit scale can be largely reduced as a whole, and further, the FIR digital filter suitable for LSI can be provided by reducing the circuit scale. Also, the result of the tap coefficient processing performed in advance is stored in the calculation result ROM.
And the output of the shift register is used as the address, so that all of the tap coefficient ROM, the multiplier, and the full adder can be deleted, and the optimum operation result is calculated in advance. Thus, an effect is disclosed in which, together with simplification of the circuit configuration by using a simple address, it is possible to output a filter characteristic with less deterioration due to arithmetic processing.

[0005]

However, the first prior art filter matched to the preamble signal has the following problems.
In general, the filter is composed of an FIR filter. However, in a preamble based on a multi-pilot tone signal, the time waveform of the preamble has a complicated waveform. Therefore, when the tap coefficients are realized with a small number of bits, the filter output rapidly deteriorates. Therefore, there is a problem that it is necessary to increase the bit width of the tap coefficient, and it is difficult to reduce the circuit scale of the multiplier that multiplies the main signal by the tap coefficient. Furthermore, since a plurality of multipliers are often used in a matched filter, and the circuit size of the multiplier affects the circuit size of the entire filter, the circuit size of the filter matched to the multi-pilot tone signal is increased. There was a point.

The second prior art uses the symmetry of the tap coefficient of the FIR filter, and has a problem that it is difficult to reduce the circuit scale of the multiplier itself.

The present invention has been made in view of such a problem, and an object thereof is to reduce the circuit size of a filter when a preamble signal is composed of a multi-pilot tone signal. An object of the present invention is to provide a multi-pilot tone detection method and a matched filter.

[0008]

The gist of the present invention is that a filter matched with a multi-pilot tone signal to be detected is replaced with a filter matched with the multi-pilot tone signal to be detected. A multi-pilot tone detection method is characterized in that the tone signal is divided into filters matched with the respective pilot tone signals. According to another aspect of the present invention, a filter matched to a multi-pilot tone signal to be detected is divided into a plurality of filters for a matched filter that detects a multi-pilot tone signal. And a method for detecting a multi-pilot tone. The gist of the invention according to claim 3 is that one multiplier that inputs the pilot tone signal, which is an output signal of each of the plurality of filters, is provided at a subsequent stage of the plurality of filters, and The multi-pilot tone detection method according to claim 1 or 2, wherein the different pilot tone signals are converted into the same frequency by frequency-converting the separated pilot tone signals. The gist of the invention described in claim 4 is that
4. The multi-pilot tone detection method according to claim 3, wherein the pilot tone signal is converted into a DC signal, and a matched filter is formed without using a multiplier. The gist of the invention described in claim 5 is that the same frequency as each of the pilot tone signals is used as the sine wave signal for performing the frequency conversion, wherein the multi-pilot tone detection method according to claim 3 is used. Exists. The gist of the invention described in claim 6 is that a matched filter for detecting a multi-pilot tone signal
A matched filter characterized in that it has a circuit configuration in which a filter matched with the multi-pilot tone signal to be detected is divided into filters matched with the pilot tone signals constituting the multi-pilot tone signal. The gist of the invention described in claim 7 is that a matched filter that detects a multi-pilot tone signal
A matched filter characterized by having a circuit configuration in which a filter matched to the multi-pilot tone signal to be detected is divided into a plurality of filters. Further, the gist of the invention according to claim 8 is that one multiplier for inputting the pilot tone signal which is an output signal of each of the plurality of filters is provided at a subsequent stage of the plurality of filters, 8. The matched filter according to claim 6, further comprising a circuit configuration for converting the different pilot tone signals to the same frequency by frequency-converting the separated pilot tone signals. The gist of the invention described in claim 9 is that the pilot tone signal has a circuit configuration for converting the pilot tone signal into a DC signal and forming a matched filter without using a multiplier. In the matched filter. According to a tenth aspect of the present invention, there is provided a matching circuit according to the eighth aspect, wherein the sine wave signal for performing the frequency conversion has a circuit configuration using the same frequency as each of the pilot tone signals. Be in the filter. The gist of the invention according to claim 11 is that the multi-pilot tone signal is input to each of the plurality of filters, the pilot tone signal is separated, and the pilot separated by the plurality of filters. The tone signal is converted into the same frequency by each of multipliers provided corresponding to each of the plurality of filters at a subsequent stage of each of the plurality of filters, and output from an adder provided at a subsequent stage of the multiplier. The matched filter according to any one of claims 8 to 10, further comprising a circuit configuration for detecting the pilot tone signal by a single correlation detection filter matched to a signal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to reduce the circuit scale by using a filter for separating individual pilot tone signals in a filter used for detecting a multi-pilot tone signal. The multi-pilot tone signal is input to a filter, and each pilot tone signal is separated. Each pilot tone signal separated by the filter is converted to the same frequency by a multiplier. Since the output signal of the multiplier has the same frequency, the output signal of the adder is also a pilot tone signal.
Therefore, the pilot tone signal can be detected by a single correlation detection filter that matches the output signal of the adder.

With the above configuration, a matched filter for detecting a multi-pilot tone signal can be used in common, and a reduction in circuit scale can be realized. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a functional block diagram illustrating a multi-pilot tone detection filter 100 according to an embodiment of the present invention. In the present embodiment, a case will be described in which the multi-pilot tone detection method of the present invention is applied to detection of a preamble 34 (described later) using a multi-pilot tone signal 32 arranged at the beginning of a burst signal signal.

Referring to FIG. 1, in the present embodiment, the multi-pilot tone signal 32
2, 3 and each pilot tone signal 30,.
30 are separated. Each of the pilot tone signals 30,..., 30 separated by the filters 1, 2, 3 is converted to the same frequency by the multipliers 4, 5, 6. Multiplier 4,
Since the output signals 5 and 6 have the same frequency, the output signal of the adder 7 also becomes the pilot tone signal 30. Therefore, the pilot tone signal 30 can be detected by the single correlation detection filter 8 that matches the output signal of the adder 7.

With the above configuration, in the multi-pilot tone detection filter 100 for detecting the multi-pilot tone signal 32, the multi-pilot tone detection filter 100 can be shared, and the circuit size can be reduced. .

The received signal input to the preamble detection filter has a predetermined frame format. An example is shown in FIG. FIG. 2 is an example of a frame format.

Referring to FIG. 2, a preamble 34 composed of a multi-pilot tone signal 32 is arranged at the head of the burst signal, and data 36 is received following the preamble 34. The multi-pilot tone signal 32 constituting the preamble 34 is a predetermined signal and is fixedly arranged at the head of all burst signals.

In FIG. 1, a received signal input to a multi-pilot tone detection filter 100 is input to filters 1, 2, and 3 having a number equal to the number n of pilot tones constituting a multi-pilot tone signal 32. The filters 1, 2, and 3 are narrow band filters sufficient to output only the individual pilot tone signal 30, and are realized by, for example, a Butterworth filter.

The output signals of the filters 1, 2, 3 are input to the multipliers 4, 5, 6. The multipliers 4, 5, and 6 receive the output signal signals of the filters 1, 2, and 3 and a sine wave signal (sine wave shown in the drawing), and output the result of multiplication of the two. However, the sine wave signals input to the multipliers 4, 5, and 6 have different frequencies for each of the multipliers.

The output signals of the multipliers 4, 5, and 6 are input to an adder 7, and the outputs of all the multipliers are added. The output signal of the adder 7 is input to the correlation detection filter 8.
The correlation detection filter 8 is a filter that matches the converted pilot tone signal 30 that is the output signal of the adder 7, and the correlation detection filter 8 performs correlation detection.

Next, the configuration of the correlation detecting filter 8 of FIG. 1 will be described with reference to FIG. FIG. 3 is a functional block diagram showing an embodiment of the correlation detection filter 8 of FIG.

Referring to FIG. 3, the correlation detecting filter 8 according to the present embodiment includes a first filter 24 and a second filter 25. The first filter 24 is a narrow-band filter that outputs only the frequency-converted pilot tone signal 30, and is composed of, for example, a Butterworth filter. On the other hand, the second filter 25 is a filter matched to the frequency-converted pilot tone signal 30.

Next, the configuration of the second filter 25 of FIG. 3 will be described with reference to FIG. FIG. 4 is a functional block diagram showing an embodiment of the second filter 25 of FIG.

In this embodiment, a case where a 5-tap FIR filter is employed as the second filter 25 will be described. Referring to FIG. 4, the filter input signal 38
Are sequentially delayed by delay units 9, 10, 11, and 12.
The multipliers 13, 14, 15, 16, and 17 are provided with tap coefficients a0, a0, which are set to the multiplication operation unit input signal and after the multiplication operation unit.
a1, a2, a3, and a4 are circuits that perform multiplication.

The filter input signal 38 is input to the multiplier 13. The filter input signal 38 delayed by one time slot by the delay unit 9 is input to the multiplier 14. The output signal of the delay unit 10 is input to the multiplier 15,
The filter input signal 38 delayed by two time slots is input by the delay unit 9 and the delay unit 10.

Similarly, the filter input signal 38 delayed by three time slots, which is the output signal of the delay unit 11, is input to the multiplier 16. The multiplier 17 includes a delay unit 1
The filter input signal 38 delayed by 4 time slots, which is the output signal of 2, is input.

Tap coefficients a0, a1, a2, a3, and a4 are set in the multipliers 13, 14, 15, 16, and 17, and the multipliers 13, 14, 15, 16, and 17 use the multipliers 13, 14, and 17, respectively. , 15, 16, 17 and the multiplication results of the tap coefficients a0, a1, a2, a3, a4 are output. The adder 18 includes multipliers 13, 14, 15, 16, 1
7 is input and the multipliers 13, 14, 15, 1
The addition result of the output signals 6, 17 is output as a filter output signal.

In particular, in FIG. 1, the pilot tone signal 30 is used as a sine wave signal input to the multipliers 4, 5, and 6.
When a sine wave signal having the same frequency as the above is used, the configuration of the second filter 25 can be simplified.

One embodiment of a simplified second filter 25 is shown in FIG. FIG. 5 is a functional block diagram showing an embodiment of a simplified sub-filter. In the present embodiment, a case will be described in which a 5-tap FIR filter is employed as in the case of FIG.

Referring to FIG. 5, multipliers 19, 20, and 2
Reference numerals 1 and 22 denote delayers for delaying the input signal by one time slot. Multipliers (delay devices) 19, 20, 21, 22
The filter input signal 38 sequentially delayed by 2 is input to the adder 23, and the addition result is output as a filter output signal.

Next, the operation of this embodiment shown in FIG. 1 (multi-pilot tone detection method) will be described.

Referring to FIG. 1, filters 1, 2, 3
Is a filter that has each of the pilot tone signals 30,..., 30 constituting the multi-pilot tone signal 32 as a center frequency and blocks the adjacent pilot tone signal 30.

The pilot tone signal 3 constituting the multi-pilot tone signal 32 by the filters 1, 2 and 3
Since 0 is separated and output, only the pilot tone signal 30 of a specific frequency exists in the band in the output signals of the filters 1, 2, and 3.

The multipliers 4, 5, and 6 are provided with filters 1, 2, 3
Is multiplied by the sine wave signal, and the multipliers 4, 5,
6 is shifted on the frequency axis.

The output signals of the filters 1, 2, 3 include:
Since only the pilot tone signal 30 having the characteristic frequency exists, when the shift on the frequency axis is performed by the multipliers 4 and 5, the signals that move to the desired frequency are the output signal signals of the filters 1, 2, and 3. Only the pilot tone signal 30.

The pilot tone signals 30 shifted to the same frequency by the multipliers 4 and 5 are input to the adder 7, and a single pilot tone signal 30 is output by the addition.

Next, the operation of the correlation detecting filter 8 shown in FIG. 3 will be described. Referring to FIG. 1, multipliers 4,
In the case where the frequency conversion is performed according to the steps 5 and 6, harmonics are generated in addition to the pilot tone signal 30 converted to a desired frequency. Since harmonics are not deleted in the addition operation by the adder 7, it is necessary to delete them by a filter.

Referring to FIG. 3, the first filter 24
Is a filter whose center frequency is the frequency-converted pilot tone signal 30, and removes harmonics generated by the multipliers 4, 5, and 6.

Since the input signal of the second filter 25 is the pilot tone signal 30 from which the harmonics have been eliminated, the correlation can be detected by using a filter matched to the pilot tone signal 30. This is the second
Tap coefficients a0, a1, a2, a3 of the filter 25
This is realized by making a4 the impulse response of the filter matched to the frequency-converted pilot tone signal 30.

From the above, it can be seen that the present embodiment operates as the multi-pilot tone detection filter 100 used for detecting the multi-pilot tone signal 32.

Next, the operation of the second filter 25 shown in FIG. 5 will be described. In the present embodiment, the multiplier 4,
When the frequency of the sine wave signal by which the input is multiplied by 5, 6 is made equal to the frequency of the pilot tone signal 30 output by the filters 1, 2, 3, the frequency-converted pilot tone signal 30 is converted into a DC signal. You. Since the DC signal has no waveform change with time, the tap coefficients a0 and a0 of the multi-pilot tone detection filter 100
1, a2, a3, and a4 have the same value. The embodiment shown in FIG. 5 has a configuration in which the multipliers 13, 14, 15, 16, 17 are removed from the embodiment shown in FIG. 4, and the tap coefficient a0 in the embodiment shown in FIG. ,
This corresponds to the case where all of a1, a2, a3, and a4 are set to 1. Therefore, when the frequency of the pilot tone signal 30 is converted into a DC signal by the multipliers 4, 5, and 6, it is understood that the embodiment shown in FIG. 5 constitutes the multi-pilot tone detection filter 100 for the input signal.

As described above, according to the present invention, in the multi-pilot tone detection filter 100 for detecting the multi-pilot tone signal 32, each of the pilot tone signals 30,... , The filter 100 for multi-pilot tone detection can be shared, and as a result, an effect that the circuit scale can be reduced can be achieved.

In particular, by using the same frequency as each of the pilot tone signals 30,..., 30 as the sine wave signal for frequency conversion, the multi-pilot tone detecting filter 100 can be configured without using a multiplier. become able to.

It should be noted that the present invention is not limited to the above embodiment, and it is apparent that the above embodiment can be appropriately modified within the scope of the technical idea of the present invention. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to numbers, positions, shapes, and the like suitable for carrying out the present invention. In each drawing, the same components are denoted by the same reference numerals.

[0043]

As described above, according to the present invention, in a matched filter for detecting a multi-pilot tone signal, each pilot tone signal is separated and frequency-converted so that the matched filter can be shared. As a result, there is an effect that the circuit scale can be reduced.

In particular, by using the same frequency as each pilot tone signal as a sine wave signal to be subjected to frequency conversion, a matched filter can be configured without using a multiplier.

[Brief description of the drawings]

FIG. 1 is a functional block diagram for explaining a multi-pilot tone detection filter according to an embodiment of the present invention.

FIG. 2 is an example of a frame format.

FIG. 3 is a functional block diagram illustrating an embodiment of the correlation detection filter of FIG. 1;

FIG. 4 is a functional block diagram illustrating an embodiment of the second filter of FIG. 3;

FIG. 5 is a functional block diagram showing an embodiment of a simplified sub-filter.

[Explanation of symbols]

1, 2, 3 ... filters 4, 5, 6 ... multipliers 7, 23 ... adders 8 ... filters for correlation detection 9, 10, 11, 12 ... delay units 13, 14, 15, 16, 17, 19, 20 , 21,2
2 Multiplier 24 First filter 25 Second filter 30 Pilot tone signal 32 Multi-pilot tone signal 34 Preamble 36 Data 38 Filter input signal 100 Multi-pilot tone detection filter (matched filter) a0, a1, a2, a3, a4 ... tap coefficients

Claims (11)

[Claims] 1. For a matched filter for detecting a multi-pilot tone signal, a filter matched to the multi-pilot tone signal to be detected is divided into a filter matched to each pilot tone signal constituting the multi-pilot tone signal. A multi-pilot tone detection method characterized by comprising: 2. A multi-pilot tone detection apparatus according to claim 1, wherein a filter matched to the multi-pilot tone signal to be detected is divided into a plurality of filters. Method. 3. A multiplier which receives the pilot tone signal as an output signal of each of the plurality of filters is provided at a subsequent stage of the plurality of filters, and the pilot tone separated by each of the plurality of filters is provided. 3. The multi-pilot tone detection method according to claim 1, wherein the different pilot tone signals are converted into the same frequency by converting the frequency of the signal. 4. The multi-pilot tone detection method according to claim 3, wherein said pilot tone signal is converted into a DC signal and a matched filter is formed without using a multiplier. 5. The multi-pilot tone detection method according to claim 3, wherein the same frequency as each of the pilot tone signals is used as the sine wave signal for performing the frequency conversion. 6. For a matched filter for detecting a multi-pilot tone signal, a filter matched to the multi-pilot tone signal to be detected is divided into a filter matched to each pilot tone signal constituting the multi-pilot tone signal. A matched filter having a circuit configuration as described above. 7. A matched filter having a circuit configuration in which a filter matched with a multi-pilot tone signal to be detected is divided into a plurality of filters, compared to a matched filter that detects a multi-pilot tone signal. 8. A multiplying device for receiving the pilot tone signal, which is an output signal of each of the plurality of filters, is provided at a subsequent stage of the plurality of filters, and the pilot tone separated by each of the plurality of filters is provided. 8. The matched filter according to claim 6, wherein the matched filter has a circuit configuration for converting the different pilot tone signals to the same frequency by converting the frequency of the signal. 9. The matched filter according to claim 8, further comprising a circuit configured to convert the pilot tone signal into a DC signal and form a matched filter without using a multiplier. 10. The matched filter according to claim 8, wherein the matched filter has a circuit configuration using the same frequency as each of the pilot tone signals as the sine wave signal for performing the frequency conversion. 11. The multi-pilot tone signal comprises:
The pilot tone signal is input to each of the plurality of filters, the pilot tone signal is separated, and the pilot tone signal separated by each of the plurality of filters is provided to each of the plurality of filters at a subsequent stage of each of the plurality of filters. Each of the multipliers provided correspondingly is converted into the same frequency, and the detection of the pilot tone signal is performed by a single correlation detection filter matched to the output signal of the adder provided at the subsequent stage of the multiplier. The matched filter according to any one of claims 8 to 10, further comprising a circuit configuration for performing the matching.