JP2840496B2 - Dual band wireless communication 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 dual band radio communication device. In particular, it relates to a compatible digital car phone.

[0002]

2. Description of the Related Art In Japan, a digital car telephone system service is scheduled to start in 1993. As the frequency band assigned to this,
There are two bands, 800 MHz band and 1.5 GHz band.

[0003] The base station transmission frequency in this 800 MHz band is
810 to 826 MHz, and the mobile station transmission frequency is 940 to 956 MHz. This 800 MHz band is scheduled to be allocated to existing analog car phone operators such as NTT. And
The base station transmission frequency in the 1.5 GHz band is 1477 to 1489 MHz
And 1501 to 1513 MHz. Further, the mobile station transmission frequency in this 1.5 GHz band is 1429 to 1441 MHz and 1453 to 1465 M
Hz. The 1.5 GHz band will be allocated to new operators such as Japan Telecom.

By the way, there is a demand for a compatible digital car telephone which can communicate by connecting to both the 800 MHz band and the 1.5 GHz band. This compatible digital car phone is technically a dual-band wireless communication device. By the way, a conventional dual-band wireless communication device used for amateur radio and the like includes a transmission system circuit and a reception system circuit for each band. That is, the conventional dual-band wireless communication device has two transmission circuits and two reception circuits, and performs communication by selecting one of them according to the band to be used.

[0005]

In the conventional dual band radio communication apparatus, the transmission / reception system circuit has two circuits.
Since the system is constituted by a system, there is a problem that the circuit becomes large.

[0006]

According to the present invention, the center oscillation frequency of a local oscillation circuit (4, 11) supplied to a mixer (3, 12) for up-conversion and down-conversion is set to a first band and a first band. It is characterized in that the value is an intermediate value between the frequencies of the two bands.

[0007]

According to the present invention, up-conversion to the first and second bands or down-conversion from the first and second bands can be performed even if the variable range of the local oscillation frequency is narrow.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a compatible digital car telephone will be described with reference to FIG. This compatible digital car phone can communicate in both the 800 MHz band and the 1.5 GHz band. Note that the 1.5 GHz band communication of this compatible digital car phone has a transmission frequency of 1453 to 1465 MHz.
z, possible only in the 12 MHz band where the reception frequency is 1501 to 1513 MHz.

(1) is a modulator. This modulator (1) outputs a modulated wave. (2) is a transmission system IF signal processing circuit (transmission IF circuit). The transmission IF circuit (2) up-converts the modulated wave to a transmission intermediate frequency (transmission IF frequency) of 255.5 MHz. (3) is a mixer. The mixer (3) multiplies the signal of the transmission IF frequency by a local oscillation signal corresponding to the transmission channel from the frequency synthesizer (4) to up-convert the signal to a radio frequency.

(4) is a frequency synthesizer. The frequency synthesizer (4) has a built-in local oscillation circuit, and changes the set value of an internal program divider to change the oscillation frequency of the local oscillation circuit. Generally, digital car phone channels are 25KHz apart,
The oscillation frequency of 25 KHz is changed by changing at least the minimum unit of the set value. This frequency synthesizer (4)
Is set to 1195.5 MHz to 1211.5 MHz.

(5) A first transmitting system radio frequency signal extracting circuit for passing a first band signal of 940 MHz to 956 MHz.
(First transmission BPF circuit). This first transmission BPF circuit
(5) extracts an 800 MHz band transmission signal. That is, when a frequency of 1200.5 MHz is output from the frequency synthesizer (4), the mixer (3) outputs a signal of 1200.5 MHz ± 255.5 MHz. This first transmission BPF circuit (5)
Extract 255.5MHz (945MHz) signal, extra 1200.5MHz + 2
Remove the 55.5MHz component.

(6) A second transmission system radio frequency signal extraction circuit for passing a second band signal of 1453 MHz to 1465 MHz.
(A second transmission BPF circuit). This second transmission BPF circuit
(6) extracts a transmission signal in the 1.5 GHz band. That is, when a frequency of 1200.5 MHz is output from the frequency synthesizer (4), the mixer (3) outputs a signal of 1200.5 MHz ± 255.5 MHz. The first transmission BPF circuit (6) has a frequency of 1200.5 MHz +
Extract the signal of 255.5MHz (1456MHz),
Remove the 255.5MHz component.

The first and second transmission BPF circuits (5, 6)
It operates selectively when transmitting in the 00 MHz band and when transmitting in the 1.5 GHz band. (7) is an antenna selector. (8) is an antenna. (9) is a first receiving system radio frequency signal extraction circuit (first receiving band) for passing a receiving signal of a first band of 810 MHz to 826 MHz.
Receiving BPF circuit).

(10) is a second reception system radio frequency signal extraction circuit (second reception BPF circuit) for passing the reception signal of the second band of 1501 MHz to 1513 MHz. (11) has a variable range
This is a frequency synthesizer for reception at 1154.5 MHz to 1170.5 MHz. This frequency synthesizer (11) has a built-in local oscillation circuit like the frequency synthesizer for transmission (4), and by changing the set value of the internal program divider,
The oscillation frequency of the local oscillation circuit is changed.

(12) is a mixer. This mixer (12)
Converts the received signal to the first received IF frequency of 344.5 MHz. The mixer (12) performs down conversion by multiplying the received signal by the local oscillation signal. (13) is a reception system intermediate frequency signal processing circuit (reception IF circuit). The reception IF circuit (13) performs interference wave removal, conversion to the second IF frequency of 450 KHz, waveform shaping, and signal amplification.

(14) is a demodulation circuit. First, the operation of the transmission system will be described. The modulated wave generated by the modulator (1) is up-converted by the transmission IF circuit (2) to the transmission IF frequency. Further, this signal is up-converted by the mixer (3) to a radio frequency corresponding to the transmission channel. The mixer (3) uses the local oscillation signal from the frequency synthesizer (4) and the IF for this up-conversion.
Crossover with frequency.

That is, when used as an 800 MHz band transmitter, the fundamental wave (1195.5 to 1211.5 MHz) of the frequency synthesizer (4) is used.
z) is output to the mixer (3) as a local oscillation signal. As a result, of the up-converted signals, the first band signal of 940 MHz to 956 MHz in the 800 MHz band is transmitted to the first transmission BPF.
It is extracted and transmitted by the circuit (5). During transmission in the 800 MHz band, the second transmission BPF circuit (6) is turned off and does not output a signal.

When used as a 1.5 GHz band transmitter, the fundamental wave (1195.5 to 1211.5 MHz) of the frequency synthesizer (4) is used.
z) is output to the mixer (3) as a local oscillation signal. As a result, of the up-converted signals, the signal of the second band of 1501 Hz to 1513 MHz in the 1.5 GHz band is transmitted to the second transmission BP.
It is extracted and transmitted by the F circuit (6). At this time, the first transmission BPF circuit (5) is turned off and does not output a signal.

Further, the transmission signal in the 800 MHz band and the transmission signal in the 1.5 GHz band can be created from the same transmission IF signal, but their spectra are inverted. For this reason, 800 MHz
When transmitting in the band, the modulation circuit (1)
The polarity of the data is inverted. Next, the operation of the receiving system will be described.

The received signal received by the antenna (8) is passed through the antenna selector (7) to the first reception BPF circuit (9) and the second reception BPF circuit (9).
It is input to the receiving BPF circuit (10). Where signal amplification,
After the interference wave is removed, the received signal is down-converted by multiplying with the local oscillation signal by the mixer (12) so as to be converted into the received first IF frequency.

When used as an 800 MHz band receiver, the fundamental wave (1154.5 MHz to 1170.5 MHz) of the frequency synthesizer is supplied to the mixer (12) as a local oscillation signal. This local oscillation signal causes the mixer (12) to receive the first band reception RF signal.
The signal is downconverted to a receive first IF frequency of 344.5 Hz. This is input to the reception IF circuit (13), and after performing the interference wave removal processing, conversion to the second IF frequency (450 KHz), waveform shaping processing, and signal amplification processing, it is output to the demodulator (14). . The signal is demodulated by the demodulator (14).

The same applies when used as a 1.5 GHz band receiver. The mixer (12) down-converts the received RF signal of the second band. As described above, the reception first IF of 344.5 MHz is also performed at the time of 1.5 GHz band reception similarly to the 800 MHz band reception.
Conversion to frequency becomes possible. Also, the spectrum of the received IF signal created from the 800 MHz band received signal and the spectrum of the received IF signal created from the 1.5 GHz band received signal are inverted. For this reason, the data polarity of the demodulation circuit (1) is once inverted at the time of reception in the 800 MHz band as compared with the time of reception in the 1.5 GHz band.

[0023]

As described above, according to the present invention, since many circuits that can be shared in communication in the first and second bands of the communication device are included, it is advantageous for miniaturization of the wireless communication device. Since the IF signal is converted into the first or second band wireless signal by the local oscillation signal, the size of the dual-band wireless communication device can be reduced by including many circuits that can be shared for transmission in different bands.

Further, since the received signal of the first or second band is converted into the same received IF signal by the common local oscillation signal, the dual band wireless communication apparatus includes many circuits that can be shared for reception of different bands. Can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

[Explanation of symbols]

 (2) ... transmission IF circuit, (3) ... mixer (transmission mixer circuit), (4) ... frequency synthesizer (transmission local oscillation circuit), (5) ... first transmission BPF circuit (first filter circuit), (6) ... second transmission BPF circuit (second filter circuit), (9) ... 1st reception BPF circuit, (10) ... second reception BPF circuit, (11) ... frequency synthesizer (local oscillation circuit for reception), (12) ... mixer (reception) (System mixer circuit) (13) ····· Reception system IF circuit.

Claims (2)

(57) [Claims] A first band transmitting radio frequency and a second band transmitting radio frequency;
A transmission local oscillation circuit (4) having an oscillation center frequency substantially at an intermediate frequency with the transmission radio frequency of the transmission line, and an output of the transmission local oscillation circuit (4) to transmit the transmission intermediate frequency signal to the first and second signals. Transmission mixer circuit for up-converting to radio frequency signal of band 2 (3)
And a first filter circuit (5) for extracting the signal of the first band from an output signal of the transmission mixer circuit (3).
And a second filter circuit (6) for extracting the signal of the second band from the output signal of the transmission mixer circuit (3).
And a dual band wireless communication device comprising: 2. The reception radio frequency of the first band and the second band
A reception local oscillation circuit substantially intermediate frequency and the oscillation center frequency of the de reception radio frequency (11), the output of the reception local oscillation circuit (11), said first及beauty second
A reception mixer circuit (12) for down-converting a radio frequency signal of the band to a reception intermediate frequency signal.