JP3246842B2 - Wireless device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplex radio apparatus mainly used for an analog mobile communication system, and more particularly to a modulation scheme using an all carrier SSB (Single Side Band: single sideband communication) system or a reduced carrier SSB system. , TDD (Time Division Duplex)
: Time division duplex).

[0002]

2. Description of the Related Art All carrier SSB system or reduced carrier S
As a method of generating the SSB wave used in the SB system, there are a selective filter method and a phase shift method. The selectivity filter method is
One band is removed by a band-pass filter and S
This is a method for generating an SB wave. The phase shift method is a method of performing a Hilbert transform on a baseband signal by a Hilbert transformer and generating an SSB wave by orthogonal modulation of the baseband signal and the Hilbert transform of the baseband signal.

On the other hand, the TDD system is generally called one frequency duplex or ping-pong transmission, and the same frequency is assigned to a transmission frequency and a reception frequency, and the transmission and reception are periodically repeated on the same frequency to perform the duplex. It will be realized. That is, it is a duplex system in which transmission and reception are divided on a time axis.

[0004]

However, the above-mentioned conventional SSB method has the following problems.
It has been difficult to realize a D-system analog duplex radio apparatus. First, in order to completely remove one sideband by the selective filter method, the amplitude characteristic of the filter needs a sharp cutoff characteristic close to a square. The unsuccessful sideband component exists as unnecessary radiation, and causes interference.

Second, since the phase shift method uses a signal obtained by performing a Hilbert transform on a baseband signal, the accuracy of the Hilbert transform becomes a problem. The Hilbert transform is (-∞ ~
ヒ ル) is defined for the baseband signal in the range, and the TDD method cannot realize the Hilbert transform of the baseband signal in the range of (−∞ to ∞). Therefore,
The Hilbert transform is performed by approximation in a finite time. However, since the time is finite, an error of the Hilbert transform occurs, which causes the spectrum to spread.

SUMMARY OF THE INVENTION The present invention solves such a conventional problem, and aims to improve the accuracy of the Hilbert transform and to provide an analog duplex of the TDD system using the all carrier SSB system or the reduced carrier SSB system with less unnecessary radiation. It is an object to provide a wireless device.

[0007]

In order to achieve the above object, the present invention uses an all carrier SSB system or a reduced carrier SSB system as a modulation system and a TDD system as a duplex system.
Means for converting a baseband signal into a pulse amplitude modulation (PAM) signal in a transmission baseband unit and transmitting the PAM signal through a band limiting filter, and a PAM received in a reception baseband unit.
Means for sampling the code identification point of the signal and interpolating the waveform with a digital filter.
The use of an FIR filter that satisfies the first criterion
It is characterized by the following.

[0008]

According to the present invention, an audio signal is converted to a PAM signal by the above configuration.
A Hilbert transform is performed by converting the PAM signal into a band-limited filter multiplied by a window function, for example, an impulse response signal of an FIR filter multiplied by a window function and an impulse response signal of an FIR filter multiplied by a window function. it is possible to improve the accuracy, it is possible to reduce the adjacent channel leakage power due to an error of the Hilbert transform, low unwanted radiation
Can be done. Also, Nike
Bandwidth limitation by FIR filter that satisfies the first criterion
The PAM signal through the FIR filter
The signal can realize a radio apparatus of the SSB system and the TDD system in which intersymbol interference does not occur .

[0009]

FIG. 1 shows a schematic configuration of a radio apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an input audio signal, 2 denotes a band limit of the input audio signal 1,
A transmission baseband unit that divides each frame and time-compresses it, adds a synchronization symbol at the beginning, and further performs Hilbert transform to convert it into two systems of baseband signals.
Are quadrature modulators that respectively amplitude-modulate and add intermediate frequencies orthogonal to each other by two baseband signals,
Is a radio unit for converting a quadrature-modulated signal from an intermediate frequency to a line frequency and outputting the signal, 5 is an antenna switch for switching between transmission and reception, 6 is an antenna for transmitting and receiving a radio signal, and 7 is a front panel for converting a received signal to an intermediate frequency. An end unit 8 is an SSB demodulation unit that demodulates the intermediate frequency signal into a baseband signal, and 9 is a unit that extracts a synchronization symbol from the demodulated baseband signal to generate a reception slot timing, and encodes the converted PAN signal. The reception baseband unit that samples the identification points, interpolates the waveform with a digital filter, expands the compressed audio signal on the time axis, and limits the band, is a restored audio signal. Reference numeral 11 denotes a synthesizer circuit for outputting a local frequency for performing frequency conversion in the radio section 4 on the transmitting side and the front end section 7 on the receiving side, and 12 designates a timing for alternately performing a transmitting operation and a receiving operation at regular intervals. A transmission baseband unit 2, a reception baseband unit 9,
The operation timing of the synthesizer circuit 11, the antenna switch 5, and the like is controlled.

FIG. 2 shows the details of the transmission baseband unit 2 of FIG.
In FIG. 2, 21 is a low-pass filter, 22 is an A / D
A converter 23 is a transmission frame switch, 24 is a synchronous memory, 25 and 26 are buffer memories, 27 is a transmission frame switch, and 28 is a synchronous symbol insertion switch. 2
Reference numeral 9 denotes a digital filter / Hilbert converter, which satisfies the Nyquist first criterion.
(Response: finite length impulse response) filter and Hilbert transformer. 30 is a DC power supply, 31 is an adder, 32 and 33 are multipliers, and 34 is a window function generator. The timing control circuit 12 supplies 1 / T to the input sides of the A / D converter 22 and the buffer memories 25 and 26.
The clock CLK1 of s [kHz] is supplied, and the output of the synchronous memory 24 and the buffer memories 25 and 26 is 2 /
A clock CLK2 of Ts [kHz] or more is supplied, a switch switching signal TIM1 is supplied to the transmission frame switches 23 and 27 and a synchronization symbol insertion switch 28, and a TDD timing signal TIM is supplied to the window function generator 34.

FIG. 3 shows the details of the reception baseband unit 9 of FIG.
In FIG. 3, 35 is a synchronization extraction circuit, 36 is a reception frame switch, 37 and 38 are buffer memories, 39 is a reception frame switch, 40 is a digital filter which is an FIR filter, 41 is a D / A converter, and 42 is a low-pass filter. It is. The clock CLK1 is supplied from the timing control circuit 12 to the output sides of the buffer memories 37 and 38, and the clock CL1 is supplied to the input sides of the buffer memories 37 and 38.
K2 is supplied, and the switch signal TIM1 is supplied to the reception frame switches 36 and 39.

FIGS. 4 and 5 show timing in the transmission baseband unit 2 shown in FIG. In FIG. 4, (a) shows the PA output from the A / D converter 22.
(B) is the timing of the transmission frame switch 23, (c) is the timing of the transmission frame switch 27,
(D) is the timing of the synchronization symbol insertion switch 28,
(E) is an input signal of the digital filter / Hilbert converter 29. In the figure, BM1 is a buffer memory 25, BM
2 indicates a buffer memory 26, and SM indicates a synchronous memory 24. In FIG. 5, (f) shows an output signal of the digital filter in the digital filter / Hilbert converter 29,
(G) is the output signal of the Hilbert transformer, (h) is the output signal of the DC power supply 30, and (i) is the window function generator 34.
, (J) is the output signal of the multiplier 32, and (k) is the output signal of the multiplier 33.

FIG. 6 shows the reception baseband unit 9 shown in FIG.
Shows the timing of the operation. In FIG.
(L) is an output signal from the SSB demodulation unit 8, (m) is a PAM signal in the synchronization extraction circuit 35, (n) is the timing of the reception frame switch 36, (o) is the timing of the reception frame switch 39, and (p) Is the digital filter 4
An input signal of 0, and (q) is an output signal of the low-pass filter 42. In the figure, BM3 represents a buffer memory 37, and BM4 represents a buffer memory 38.

FIG. 7 shows an example of a synchronization symbol when a plurality of impulse response waveforms are used, a synchronization symbol and a first PAM.
This is an example in which a time during which only an impulse response waveform exists is provided between the signal and the signal. 71 is a synchronization symbol (3 symbols),
Numeral 72 is a zero point signal (time—4 symbols in which only an impulse response waveform exists), 73 is a first PAM signal, and 74 is an impulse response waveform.

FIG. 8 shows an embodiment of a relay station for performing time division relay. 81 is a synchronous memory, 82 is a buffer memory, 83 is a synchronous symbol insertion switch, 84 is a digital filter / Hilbert converter, 85 is an adder, 86 is a DC power supply, 87 is a multiplier, 88 is a multiplier, 89 is a window function. Generator, 90 is a quadrature modulation section, 91 is a radio section, 9
2 is a timing control circuit, 93 is a synthesizer circuit, 9
4 is an antenna switch, 95 is an antenna, 96 is a front end unit, 97 is an SSB demodulation unit, and 98 is a synchronization extraction circuit.

FIG. 9 shows a transmitting station when time-division relay is performed.
This is the transmission / reception timing between the relay station and the reception station, and shows the transmission timing of the mobile station (1) in the transmission example, the transmission / reception timing of the relay station, and the reception timing of the mobile station (2) in the reception example.

Next, transmission and reception operations in the above embodiment will be described. However, the synchronization system is a subordinate synchronization system of the called side using the calling side as a synchronization source, and the transmission and reception operation of the calling side will be described here. First, the operation on the transmitting side will be described. The audio signal 1 is input to the low-pass filter 21, band-limited, and output to the A / D converter 22. The A / D converter 22 includes a timing control circuit 12
1 / Ts [kHz], and the audio signal band-limited by the low-pass filter 21 is sampled by the A / D converter 22 at the sampling interval T.
It is sampled at s [msec] and converted into a PAM signal as shown in FIG. The PAM signal output from the A / D converter 22 is sequentially transmitted to the buffer memory 25 (BM1) as shown in FIG. 4B by the transmission frame switch 23 to which the switch switching signal TIM1 from the timing control circuit 12 is input. ) Or 26 (BM
It is accumulated in 2).

Here, the TDD frame length is set to T [mse
c], the PAM signal is alternately written as a digital signal to the buffer memory 25 or 26 every T [msec] section with a clock of 1 / Ts [kHz]. Also, when the data is read out by the transmission frame switch 27, as shown in FIG.
M1) or 26 (BM2).
Further, as shown in FIG.
5 (BM1) and 26 (BM2) immediately before reading from the synchronous memory 2 by the synchronous symbol insertion switch 28.
4, the synchronization symbol and the data of the zero point are read out,
Subsequently, the PAM signal data is read from the buffer memories 25 and 26. As a clock to be read, a clock CLK2 of 2 / Ts [kHz] or more is supplied from the timing control circuit 12 to the buffer memories 25 and 26 and the synchronous memory 24.

Synchronous symbol example and synchronous symbol and first
FIG. 7 shows an example of the time when only the impulse response waveform exists between the PAM signal and the PAM signal.

The PAM signal data output from the synchronization symbol insertion switch 28 is input to a digital filter / Hilbert converter 29 as shown in FIG.
The digital filter / Hilbert converter 29 is composed of an FIR filter in which a sinx / x type impulse response is multiplied by a raised cosine window function and a Hilbert transform in which a sinx / x type impulse response is multiplied by a raised cosine window function. Container. The signal input to the digital filter / Hilbert converter 29 is a digital filter impulse response signal mg (t) shown in FIG. 5F and a Hilbert converted signal mh (h) of the Hilbert converter shown in FIG. t), the signal mg (t) is output to the adder 31, and the signal mh
(T) is output to the multiplier 33. Here, the signal h
(T) is a Hilbert transform of g (t), m is a modulation index, and (0 <m <
1) In the case of the reduced carrier SSB method, m that satisfies (1 <m) is selected. In addition, the adder 3
1 is applied with the DC signal shown in FIG. 5 (h), and the window function generator 34 applies the raised cosine window function W shown in FIG.
(T) is applied.

Digital filter / Hilbert converter 29
Are multiplied by the window function W (t) by the multipliers 32 and 33, and as shown in (j) and (k) of FIG. 5, the signal T (t) ),
It is converted to Q (t). I (t) = W (t) · {1 + mg (t)} Q (t) = W (t) · m · h (t)

The signals I (t), Q thus obtained
(T) is quadrature-modulated by the quadrature modulator 3 in FIG. 1 and converted into an all-carrier SSB modulated wave or a reduced-carrier SSB modulated wave, and then mixed with the local frequency from the synthesizer circuit 11 in the radio unit 4 to link the line. The frequency is converted to a frequency and radiated from the antenna 6 via the antenna switch 5. The antenna switch 5 can switch between transmission and reception by a TDD timing signal TIM from the timing control circuit 12.

Next, the operation on the receiving side will be described. The received signal received from the antenna 6 is transmitted to the antenna switch 5
Is input to the front end unit 7 via the. The input signal is converted to an intermediate frequency, converted by the SSB demodulator 8 into a compressed baseband signal shown in FIG. 6 (l), and input to the synchronization extraction circuit 35. The baseband signal input to the synchronization extraction circuit 35 is subjected to synchronization symbol correlation detection. When synchronization is established, the synchronization extraction circuit 35 outputs a TDD synchronization timing signal TIM2 to the timing control circuit 12. In the PAM signal following the synchronization symbol, only the code identification point is sampled,
After being converted into a PAM signal as shown in FIG.
As shown in FIG. 6 (n), the reception frame switch 36
Thus, a digital signal is alternately written into the buffer memories 37 (BM3) and 38 (BM4) for each slot. The write clock is a clock CLK2 of 2 / Ts [kHz] or more from the timing control circuit 12.
In the case of reading, as shown in FIG. 6 (o), the reception frame switch 39 controls the buffer memory 37 (BM).
3) The data is alternately read from the buffer memory 38 (BM4). The read clock is supplied to the timing control circuit 12.
1 / Ts [kHz] from the clock CLK1.

The PAM signal data output from the reception frame switch 39 is input to a digital filter 40 using an FIR filter as a signal as shown in FIG. The input PAM signal data is converted into data whose waveform is interpolated by the digital filter 40,
After being converted into a staircase waveform by the A-converter 41, the harmonic component is suppressed by the low-pass filter 42, and the original audio signal 10 is restored.

Next, the operation of the relay station when performing time division relay will be described. The time division relay using one frequency enables the relay of the simplex communication. FIG. 9 shows mobile station (1)-
The transmission / reception timing of each station when relaying with the relay station-mobile station (2) is shown. In FIG. 9, the mobile station (1) is in the transmission state and the mobile station (2) is in the reception state. At this time, the relay station transmits the signal received in the reception slot in the immediately following transmission slot.

As the synchronization symbol pattern in the simplex relay mode, a pattern in which the polarity of the synchronization symbol pattern at the time of ordinary mobile station direct duplexing is inverted is used, so that relay (simplex) communication and direct (duplex) communication are performed using the synchronization symbol. Communication can be distinguished. In the relay system, the relay station notifies the mobile station of the relay TDD frame timing. The relay station intermittently transmits the TDD frame timing signal in which the synchronization symbol in the simplex relay mode is inserted. By receiving the TDD frame timing signal, the mobile station can accurately capture the TDD frame timing in the simplex relay mode by using the synchronization symbol attached to the TDD frame timing signal.

The operation of the relay station receiving the signal transmitted by the mobile station (1) will be described. The mobile station (1) performing the simplex relay communication receives the TDD frame timing signal intermittently transmitted from the relay station in advance, acquires the TDD frame timing in the simplex relay mode, and acquires the TDD frame timing in the relay station reception slot. Start burst transmission. As a result, the relay station starts receiving a signal from the mobile station (1) in the relay station reception slot. In the relay station, the operation of converting the received signal received from the antenna 95 to the PAM signal by the synchronization extraction circuit 98 is the same as that of the above-described duplex operation. The decoded PAM signal is sequentially transferred to the buffer memory 82 of the transmission unit as a digital signal. The write clock used at this time is fs from the timing control circuit 92.
The clock is (fs ≧ 2 / Ts) [kHz], and the timing control circuit 92 starts supplying a clock to the input side of the buffer memory 82 by receiving the TDD synchronization timing signal from the synchronization extraction circuit 98.

Next, the operation of transmission by the relay station will be described. During the reception operation of the relay station, after the writing of the PAM signal from the synchronization extraction circuit 98 to the buffer memory 82 is completed,
The timing control circuit 92 stops the clock supplied to the input side of the buffer memory 82, supplies a switch switching signal TIM1 to the synchronous symbol insertion switch 83, and supplies a clock of fs [kHz] to the synchronous memory 81. The synchronization symbol insertion switch 83 is switched to the synchronization memory 81 side when the switch switching signal TIM1 is input, and the synchronization symbol and the zero point data are read from the synchronization memory 81. When the reading of the synchronization symbol and the zero point data is completed, the timing control circuit 92 stops the switch switching signal TIM2 supplied to the synchronization symbol insertion switch 83, and supplies the clock of fs [kHz] to the output side of the buffer memory 82. I do. The synchronous symbol insertion switch 83 is switched to the output side of the buffer memory 82 by stopping the switch switching signal TIM1, and the PAM signal data is read from the buffer memory 82. The operation from the conversion of the PAM signal output from the synchronization symbol insertion switch 83 to the SSB wave to the emission from the antenna 85 is the same as in the case of the above-described duplex.

The mobile station (2) receives the burst signal transmitted first from the relay station, and accurately captures the TDD frame timing in the simplex relay mode by using the synchronization symbol inserted in the burst signal. Start burst reception in the transmission slot.

In this embodiment, a case is described in which the relay station is used as a synchronization source and each mobile station performs subordinate synchronization with the relay station.
This is an effective method when the relay station relays two or more channels simultaneously. That is, if the transmission / reception timing of each channel in the relay station is the same, the relay station does not need to perform transmission and reception at the same time, so that the antenna sharing having a steep cutoff characteristic even when the frequency allocation is made close to the relay station. There is no need to equip it.

On the other hand, in the relay station that performs the relay operation of only 1CH, since the transmission time and the reception time are separated from the original, it is only necessary to sequentially perform the slave synchronization with the transmission station (mobile station). That is, it is possible to omit the intermittent transmission of the TDD frame timing signal of the relay station and the advance synchronization acquisition operation in each mobile station in the embodiment.

In this embodiment, an example is shown in which the transmission baseband is constituted by a hardware unit, but this unit may be constituted by a DSP.

As described above, the present embodiment has the following effects. (1) Since the PAM signal is band-limited by an FIR filter that satisfies the Nyquist first criterion, the PAM signal that has passed through the FIR filter has no intersymbol interference. (2) By using the synchronization symbol using the impulse response waveform of the FIR filter that satisfies the Nyquist first criterion, the synchronization symbol via the FIR filter has no intersymbol interference and can establish accurate TDD synchronization. . For this reason, the code identification point of the PAM signal can be reliably recognized, the fidelity of the restoration of the baseband signal is improved, and there is no occurrence of a fault in the analog signal between bursts, which generally causes a problem in the TDD burst. (3) In the time division relay operation, the received signal is not restored to a baseband signal, but is returned to the transmission side with a PAM signal, so that there is no quantization noise associated with the time division relay operation. (4) When performing a simplex communication by the time-division relay operation, a plurality of channels (calls) can be simultaneously time-divisionally relayed because the relay station is used as a synchronization source.

[0034]

As is apparent from the above embodiment, the present invention uses the full carrier SSB system or the reduced carrier SSB system as the modulation system, uses the TDD system as the duplex system, and uses the baseband unit in the transmission baseband unit. PAM signal
Means for converting the signal into a signal and transmitting the signal through a band-limiting filter, and means for sampling the code identification point of the received PAM signal and interpolating the waveform with a digital filter in the reception baseband unit. First
The feature is that an FIR filter that satisfies the standard is used.
The audio signal is converted into a PAM signal, and the PAM signal is subjected to a Hilbert transform of an impulse response signal of a FIR filter obtained by multiplying the impulse response signal of a FIR filter and a window function by multiplying the PAM signal by a window function. By converting to a signal,
Since the accuracy of the Hilbert transform can be improved,
It is possible to reduce the adjacent channel leakage power due to an error of the Hilbert transform, it is possible to reduce unwanted radiation
You. Also, the Nyquist first criterion is satisfied for the PAM signal.
The band is limited by the added FIR filter.
Therefore, the PAM signal passed through the FIR filter has
A wireless device of the SSB system and the TDD system that does not occur can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a wireless device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the relationship between details of a transmission baseband unit and a timing control circuit in the wireless device.

FIG. 3 is a block diagram showing a relationship between details of a reception baseband unit and a timing control circuit in the wireless device.

FIG. 4 is a timing chart showing the timing of each unit in the apparatus.

FIG. 5 is a timing chart showing the timing of each unit in the apparatus.

FIG. 6 is a timing chart showing the timing of each unit in the apparatus.

FIG. 7 is a waveform diagram when a plurality of impulse response waveforms are used in the apparatus.

FIG. 8 is a block diagram showing a configuration of a relay station when time division relay is performed in the present invention.

FIG. 9 is a transmission / reception timing diagram when time division relay is performed in the present invention.

[Explanation of symbols]

 Reference Signs List 1 audio signal 2 transmission baseband section 3 quadrature modulation section 4 radio section 5 antenna switch 6 antenna 7 front end section 8 SSB demodulation section 9 reception baseband section 10 audio signal 11 synthesizer circuit 12 timing control circuit 21 low-pass filter 22 A / D Converter 23 Transmission frame switch 24 Synchronous memory 25, 26 Buffer memory 27 Transmission frame switch 28 Synchronous symbol insertion switch 29 Digital filter / Hilbert converter 30 DC power supply 31 Adder 32, 33 Multiplier 34 Window function generator 35 Synchronous extraction circuit 36 reception frame switch 37, 38 buffer memory 39 reception frame switch 40 digital filter 41 D / A converter 42 low-pass filter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-206917 (JP, A) JP-A-3-11814 (JP, A) JP-A-61-288604 (JP, A) JP-A-5-206 218937 (JP, A) JP-A-6-45962 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/40 H03C 1/60 H03D 1/24

Claims (7)

(57) [Claims] 1. A modulation method using an all-carrier SSB method or a reduced carrier SSB method, and a TDD as a duplex method.
A means for converting a baseband signal into a PAM signal and transmitting it through a band-limiting filter to a transmission baseband unit, and a method for sampling a code identification point of a received PAM signal to a reception baseband unit to digitally transmit the PAM signal. Means for interpolating the waveform with a filter , wherein the band-limiting filter has a FI satisfying the first Nyquist criterion
A wireless device using an R filter . 2. A radio apparatus according to claim 1, further comprising a means for multiplying a window function to the FIR filter for band-limiting. 3. The radio apparatus according to claim 2 , wherein one or a plurality of impulse response waveforms of a band limiting FIR filter is used as a synchronization symbol for TDD. 4. The radio apparatus according to claim 3, wherein a time during which only an impulse response waveform exists is provided between the synchronization symbol and the first PAM signal. 5. A radio apparatus according to claim 1 for dividing relay operation when by folding to the transmitting section 4 of the received signal after converting the PAM signal. If wherein performing time division relay operation, the wireless device according to claim 1 or <br/> et 5 that the slave synchronization method of incoming and outgoing call station that the relay station and the synchronization source. 7. A duplex radio device according to any one of claims 1 to 6, carried out by the sync symbol pattern distinction simplex.