JP3272164B2 - 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 radio communication apparatus, and more particularly to a radio communication apparatus for use in an analog mobile communication system, which enables a duplex communication even in a frequency band which is not planned for a duplex system in advance. It is about.

[0002]

2. Description of the Related Art A communication system of a mobile communication system includes a simplex system and a duplex system. As a duplex system of a general mobile communication system, frequency division duplex (FDD) is used.
visionDuplex method and time division duplex (TDD: Time Di)
vision Duplex) system. The FDD (generally referred to as "two-frequency duplex") system realizes a duplex communication by allocating different frequencies to a transmission frequency and a reception frequency and performing simultaneous transmission / reception operations. That is, it is a duplex system in which transmission and reception are divided on the frequency axis.

[0003] On the other hand, the TDD (commonly called "single frequency duplex" or "ping-pong transmission") method assigns the same frequency to a transmission frequency and a reception frequency, and repeats transmission and reception periodically on the same frequency. This realizes a duplex call. That is, it is a duplex system in which transmission and reception are divided on a time axis.

[0004]

However, when an attempt is made to implement a duplex communication by a duplex system in a mobile communication system as described above, the above-mentioned FDD system or TDD system is generally adopted. However, the conventional method has the following disadvantages.

The FDD system requires two frequencies, a transmission frequency and a reception frequency, to separate transmission and reception. In general,
According to the frequency allocation standards in Japan, two-frequency allocation is not performed on the premise of duplex communication for general business use except for some allocated frequency bands for specific systems. Therefore, F
The DD method is a method that cannot be realized unless the initially assigned frequency is two or more. Further, the two waves must have a frequency interval in which a duplexer (filter) can be inserted in the assigned band. When the FDD system is used, the number of channels is inevitably reduced by half.

On the other hand, in the TDD system, since the audio signal is time-compressed, the baseband band is widened in proportion to the reciprocal of the compression ratio. When the modulation method is the FM method and the occupied band is to be kept constant, the reception sensitivity is deteriorated when the modulation degree is reduced and the baseband band is stored, and the sound quality is reduced when the baseband band is reduced to keep the modulation degree constant. Decrease.

Further, since the TDD system is a burst transmission, a waveform shaping for suppressing the spread of the spectrum is required. In the case of the FM system, a smooth ramp waveform shaping is not always easy because a class C amplifier is used. If this is done incompletely, the instantaneous adjacent channel leakage power will increase. Also, shortening the TDD frame increases the average adjacent channel leakage power.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a duplex radio apparatus which can reduce unnecessary radiation and perform high-quality analog transmission within an existing allocated frequency frame. And

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a modulation method for a radio apparatus, which is an all-carrier SSB which is one of the methods capable of transmitting analog signals in the narrowest band among existing methods. (Single Side Band: single sideband communication) system or reduced carrier SSB system is used, and the transmission operation and the reception operation are alternately performed at regular intervals, and in transmission, the baseband signal is compressed on the time axis and transmitted. In the reception, a function is provided in which the received signal compressed on the time axis is expanded and converted into the original baseband signal.

[0010] Further, by providing a function of performing a ramp waveform shaping in the baseband section, the baseband signal is shaped into a ramp waveform and supplied to a transmission power amplifier for linear amplification.

Further, the high-frequency amplifier has a function of shaping the ramp waveform.

[0012]

Therefore, according to the present invention, by using the TDD system as the duplex system according to the above configuration, duplex can be performed with one frequency, and a filter for performing simultaneous two-frequency transmission and reception such as the FDD system can be inserted. Is unnecessary. In addition, as for the point that the baseband band is widened for time-compressing the audio signal by using the TDD system, an all-carrier SSB system or a reduced carrier SSB system that transmits the baseband band in one sideband is used as a modulation system. Thus, the analog signal can be transmitted in the narrowest band. Therefore, the occupied band can be made substantially constant without lowering the modulation factor and reducing the baseband band unlike the FM system. Therefore, deterioration of sensitivity and deterioration of sound quality due to time compression of the audio signal are small. Further, by using the TDD method, T
Ramp waveform shaping for suppressing the adjacent channel leakage power generated in the DD burst is required, but in the present invention, by using the all-carrier SSB system or the reduced carrier SSB system of the amplitude modulation system as the modulation system, Since it is composed of a linear modulation system, it is possible to perform transmission ramp waveform shaping by giving a gentle slope to the leading edge (rising edge) and trailing edge (falling edge) of a burst-like baseband signal. Become.

[0013]

FIG. 1 shows an embodiment relating to the TDD frame structure of the present invention. The TDD frame length is T milliseconds (1
/ 1000 seconds, hereinafter referred to as “msec”, and the inside is divided into two sections of a transmission slot (slot length T / 2 msec) and a reception slot (slot length T / 2 msec). The TDD frame is arranged in the order of a calling station transmission slot (called station reception slot) 1-1 at the front, and a called station transmission slot (calling station reception slot) 1-2 at the rear.

In each slot, a front collision avoidance guard time 1-3, a transmission rise waveform control time 1-4, a synchronization symbol transmission time 1-5, an audio signal transmission time 1-6, a transmission fall waveform control time 1-7 and guard time 1-8 for rear collision avoidance. The synchronization method is
This is a called-side dependent synchronization method using the calling side as a synchronization source.

FIG. 2 is a block diagram showing a configuration of a wireless device according to one embodiment of the present invention. In this figure, 2-1
Is a transmission unit. The transmission unit 2-1 includes a transmission baseband unit 2-3 serving as a reception unit for the audio signal 2-2 input to the transmission unit 2-1, a quadrature modulation circuit 2-4, and a π / 2 phase shifter. 2-5, an oscillation circuit 2-6, a mixer circuit 2-7,
Power amplification circuit 2-8 for amplifying power by high frequency amplification
And performs a transmission operation when transmitting a signal from the wireless device to the partner device. Reference numeral 2-9 denotes a timing control circuit which takes timing for the wireless device of the present embodiment to alternately perform a transmission operation and a reception operation at regular intervals.
-10 is a synthesizer circuit, 2-11 is an antenna switch for switching an antenna between a transmission operation and a reception operation,
2-12 is an antenna. 2-13 is a receiving unit.
The receiving unit includes a front end unit 2-14, an SSB demodulation circuit 2-15, and a reception baseband unit 2-16, and converts a received signal into an audio signal 2-17 and outputs the audio signal 2-17.

The operation of the wireless device having such a configuration will be described below. During the transmission operation, the timing control circuit 2-9 sends the clock signal C to the transmission baseband section 2-3.
LK, and synthesizer circuit 2-10,
The TDD frame timing signal is sent to the power amplifier circuit 2-8 and the antenna switch 2-11. As a result, the mixer circuit 2-10
-7, the local frequency signal is output, and the antenna switch 2-11 switches the antenna 2-12 to the transmission side. In this transmission operation, the transmission unit 2-
1 audio signal 2 input to the transmission baseband unit 2-3 of FIG.
-2 (FIG. 3 (a)) is subjected to band limitation to become a baseband signal, and this baseband signal is divided for each Tmsec frame shown in the TDD frame configuration example as shown in FIG. (FIG. 3B), and further time-compressed (FIG. 3C). A synchronization symbol 1-5 is added to the head of the time-compressed audio signal for each frame (FIG. 3D). The synchronization compressed audio signal symbolic Le is added, where the signal g (t). The signal g (t) is converted into the following complex signal I (t) + jQ (t). I (t) = 1 + m · g (t) Q (t) = m · h (t) where the signal h (t) is the Hilbert transform of g (t). In addition, m represents a modulation index, and m that satisfies (0 <m <1) in the case of the all carrier SSB system and (1 <m) in the case of the reduced carrier SSB system is selected.

Further, the signals I (t) and Q (t) are multiplied by a raised cosine type window function shown in FIG. Assuming that the window function is W (t), signals I (t) and Q (t)
Are the signals W (t) · I each having a ramp waveform shaped.
(T), converted to W (t) Q (t).

FIG. 4 shows the difference in frequency characteristics between the signal I (t) without the ramp waveform shaping and the signal W (t) · I (t) with the ramp waveform shaping. For simplicity, the continuous signal I
The waveform of (t) is f (t), and its frequency characteristic is shown in FIG.
In the case of the rectangular characteristic shown in (d), the signal I (t) not subjected to the ramp waveform shaping is obtained by multiplying f (t) by the rectangular window function of FIG. And the ramp-shaped signal W (t) .I (t) is obtained by multiplying f (t) by the raised cosine window function of FIG.
This means that the TDD burst of sec has been extracted. In general, multiplication on the time axis is known to be convolution integration on the frequency axis. That is, the convolution integral of the frequency characteristic of the rectangular window function in FIG. 4B and the frequency characteristic of f (t) in FIG. 4D is the frequency characteristic of the signal I (t) that is not subjected to the ramp waveform shaping. FIG. 4D shows the frequency characteristics of the raised cosine window function shown in FIG.
The convolution integral of the frequency characteristic of f (t) is the frequency characteristic of the signal W (t) · I (t) obtained by shaping the ramp waveform.
As shown in FIGS. 4B and 4C, the frequency characteristics of the raised cosine window function converge faster than the frequency characteristics of the rectangular window function.
As for the result of the convolution integral with, the raised cosine window function has better convergence and can suppress the spread of the spectrum.

The two time-compressed signals W (t) ·
I (t), W (t) and Q (t) represent the transmission baseband unit 2
-3 to the quadrature modulation circuit 2-4. Further, a cosine wave and a sine wave having an angular frequency ωT are applied to the quadrature modulation circuit 2-4 by the oscillation circuit 2-6 and the π / 2 phase shifter 2-5.

The signal W generated by the transmission baseband unit
(T) · I (t) and W (t) Q (t) are transmitted by the quadrature modulation circuit 2-4 in the following transmission IF
requency (intermediate frequency) is converted to a signal S (t).

[0021]

(Equation 1)

The transmission IF signal S thus obtained
(T) is multiplied by the local frequency from the synthesizer circuit 2-10 by the mixer circuit 2-7 to be converted to a line frequency, then linearly amplified by the power amplifier 2-8, and passed through the antenna switch 2-11. Radiated from the antenna 2-12. The antenna switch 2-11 switches between transmission and reception in accordance with the TDD frame timing signal from the timing control circuit 2-9.

On the other hand, on the receiving unit 2-13 side, the antenna 2
The signal received at -12 is transmitted to the antenna switch 2-11.
Is input to the front end unit 2-14 via the. The input signal is converted to an intermediate frequency, converted to a baseband signal as it is as a signal compressed by the SSB demodulation circuit 2-15, and input to the reception baseband unit 2-16.
The reception baseband unit 2-16 extracts a synchronization symbol from the compressed baseband signal, generates a reception slot timing, and extracts only the audio signal section.
Further, the compressed audio signal is expanded on the time axis, band-limited, and restored to the original audio signal.

[0024]

As is clear from the above embodiment, the present invention can perform a duplex communication with one wave even in the frequency allocation of the conventional FM system, so that the restrictions on the frequency allocation are relaxed and This has the effect of helping to improve the frequency use efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a TDD frame configuration of a signal used in a TDD method used in a wireless device of the present invention.

FIG. 2 is a block diagram showing an embodiment of a wireless device according to the present invention.

3A illustrates an example of an audio signal input to a transmission unit in the wireless device according to the present invention. FIG. 3B illustrates an audio signal input to the transmission unit in the wireless device according to the present invention. (C) A diagram showing a state where the divided audio signal is time-compressed in the wireless device according to the present invention. (D) A synchronization symbol is added to the time-compressed audio signal in the wireless device according to the present invention. Diagram showing status

4A is a diagram showing a raised cosine type window function and a rectangular window function. FIG. 4B is a diagram showing a frequency characteristic of a rectangular window function. FIG. 4C is a diagram showing a frequency characteristic of a raised cosine type window function. d) A diagram showing frequency characteristics when the signal I (t) has a continuous waveform.

[Explanation of symbols]

 1-1 Calling station transmission slot (Calling station reception slot) 1-2 Calling station transmission slot (Calling station reception slot) 1-3 Front collision avoidance guard time 1-4 Transmission rise waveform control time 1 5 Synchronization symbol transmission time 1-6 Audio signal transmission time 1-7 Transmission fall waveform control time 1-8 Rear collision avoidance guard time 2-1 Transmission section 2-2 Audio signal 2-3 Transmission base basid section 2-4 Quadrature Modulation circuit 2-5 π / 2 phase shifter 2-6 Oscillator circuit 2-7 Mixer circuit 2-8 Power amplifier circuit 2-9 Timing control circuit 2-10 Synthesizer circuit 2-11 Antenna switch 2-12 Antenna 2-13 Receiver 2-14 Front end 2-15 SSB demodulation circuit 2-16 Receiver baseband 2-17 Audio signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-37829 (JP, A) JP-A-5-252074 (JP, A) JP-A-3-11814 (JP, A) JP-A-62-1987 288604 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) H04B 1/54 H03C 1/60 H03D 1/24

Claims (3)

(57) [Claims] A transmitting unit, a receiving unit, an antenna for transmitting / receiving a radio wave during a transmitting / receiving operation, a timing control circuit connected between the transmitting unit and the receiving unit for timing the transmitting operation and the receiving operation, and provided in the transmitting unit. A radio apparatus of an all-carrier SSB scheme or a reduced-carrier SSB scheme having a transmission baseband unit for performing audio signal band limitation and ramp waveform shaping, wherein a transmission operation and a reception operation are alternately performed at regular intervals. For transmission, the baseband signal is compressed on the time axis for transmission, and for reception, the received signal compressed on the time axis is decompressed and converted into the original baseband signal. A time-division duplex function. 2. The radio apparatus according to claim 1, wherein ramp waveform control for reducing spread of a transmission spectrum during burst transmission is performed in a baseband unit. 3. The radio apparatus according to claim 1, wherein a ramp waveform control for reducing a spread of a transmission spectrum at the time of burst transmission is performed by a high frequency amplifying section of a transmitting section.