JPH05244032A - Dual-band radio communication device - Google Patents

Abstract

PURPOSE:To increase circuits which can be shared and reduce the size of the device by converting an IF signal into a radio signal of a 1st or 2nd band with a common local oscillation signal consisting of an intermediate frequency of a transmission radio frequency. CONSTITUTION:For communication in the 1st or 2nd band, a fundamental wave consisting of the intermediate frequency of a frequency synthesizer 4 is outputted as a common local oscillation signal to a mixer 3. A 1st transmitting BPF circuit 5 extracts the signal of the 1st band from the converted signal and sends it and a 2nd transmitting BPF circuit 6 extracts and sends the signal of the 2nd band. Then the received signals are inputted by an antenna selector 7 to 1st and 2nd receiving BPF circuits 9 and 10. The received signal is converted down by being multiplied by the local oscillation signal of a frequency synthesizer 11 so that it is converted to a 1st reception IF frequency by a mixer 12. Thus, the circuits which can be shared are increased to reduce the size of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual band wireless communication device. In particular, it relates to compatible digital car phones.

[0002]

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

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 800MHz band will be allocated to existing analog mobile phone carriers such as NTT. And
Base station transmission frequency in the 1.5 GHz band is 1477 to 1489 MHz
And 1501-1513 MHz. The mobile station transmission frequency in this 1.5 GHz band is 1429 to 1441 MHz and 1453 to 1465 M.
Hz. This 1.5GHz 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 is capable of communicating by connecting to both the 800 MHz band and the 1.5 GHz band. This compatible digital car telephone is technically a dual band wireless communication device. By the way, a conventional dual-band wireless communication device used for amateur radio or 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 system circuits and two reception system circuits, and selects one of them according to the band to be used for communication.

[0005]

In the conventional dual band radio communication device, the transmission / reception system circuit has two circuits for each.
Since it is composed of a system, there is a problem that the circuit becomes large.

[0006]

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

[0007]

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

[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 800MHz band and 1.5GHz band. The communication frequency of this compatible digital car phone in the 1.5 GHz band is 1453 MHz to 1465 MHz.
z, the reception frequency is possible only in the 12MHz band of 1501-1513MHz.

(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 up to the 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) and up-converts it to a radio frequency.

(4) is a frequency synthesizer. This frequency synthesizer (4) has a built-in local oscillation circuit, and the oscillation frequency of this local oscillation circuit is changed by changing the set value of the internal program divider. Generally, the channels of digital car phones are 25 KHz intervals,
The oscillation frequency of 25 KHz is changed by changing at least the minimum unit of the set value. This Frequency Synthesizer (4)
The variable range of is set to 1195.5MHz to 1211.5MHz.

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

(6) is a second transmission system radio frequency signal extraction circuit for passing a second band signal of 1453 MHz to 1465 MHz.
(Second transmission BPF circuit). This second transmission BPF circuit
(6) extracts the 1.5 GHz band transmission signal. That is, when the frequency synthesizer (4) outputs a frequency of 1200.5 MHz, the mixer (3) outputs a signal of 1200.5 MHz ± 255.5 MHz. This first transmission BPF circuit (6) is 1200.5MHz +
Extract the 255.5MHz (1456MHz) signal, and add the extra 1195.5MHz−
Remove the 255.5MHz component.

The first and second transmission BPF circuits (5, 6) are
It operates selectively depending on whether it is transmitting at 00MHz band or 1.5GHz band. (7) is an antenna selector. (8) is an antenna. (9) is a first reception system radio frequency signal extraction circuit (first circuit) that allows reception signals of the first band of 810 MHz to 826 MHz to pass.
Reception BPF circuit).

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

(12) is a mixer. This Mixer (12)
Converts the received signal to the received first IF frequency of 344.5 MHz. The mixer (12) performs down conversion by multiplying the received signal and 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 a 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 to the transmission IF frequency by the transmission IF circuit (2). Further, this signal is up-converted by a mixer (3) to a radio frequency corresponding to the transmission channel. This mixer (3) uses the local oscillator signal from the frequency synthesizer (4) and the IF for this up-conversion.
Cross with the 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 as a local oscillation signal to the mixer (3). As a result, of the up-converted signals, the signal of the first band of 940 MHz to 956 MHz in the 800 MHz band is transmitted as the first transmission BPF.
It is extracted by the circuit (5) and transmitted. During this 800 MHz band transmission, 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 as a local oscillation signal to the mixer (3). As a result, of the up-converted signals, the signals of the second band of 1501 Hz to 1513 MHz in the 1.5 GHz band are transmitted by the second transmission BP.
It is extracted by the F circuit (6) and transmitted. At this time, the first transmission BPF circuit (5) is turned off and does not output a signal.

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. Therefore, 800MHz
When transmitting in the band, compared to transmitting in the 1.5 GHz band, the modulation circuit (1)
The polarity of the data in is reversed. Next, the operation of the receiving system will be described.

The reception signal received by the antenna (8) passes through the antenna selector (7) and the first reception BPF circuit (9) and the second reception BPF circuit (9).
It is input to the reception BPF circuit (10). Where signal amplification,
After the interference wave is removed, the received signal is multiplied by the local oscillation signal so as to be down-converted 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. Due to this local oscillation signal, the mixer (12) receives the reception RF of the first band.
The signal is down converted to the received first IF frequency of 344.5 Hz. This is input to the receiving IF circuit (13), subjected to interference wave removal processing, conversion to the second IF frequency (450KHz), waveform shaping processing, and signal amplification processing, and then output to the demodulator (14). .. Demodulated by this 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. In this way, even when receiving at the 1.5 GHz band, as with the receiving at the 800 MHz band, the reception first IF of 344.5 MHz is received.
Conversion to frequency is possible. Further, the received IF signal created from the received signal in the 800 MHz band and the spectrum of the received IF signal created from the received signal in the 1.5 GHz band are inverted. For this reason, the polarity of the data of the demodulation circuit (1) is once inverted when receiving in the 800 MHz band, compared to when receiving in the 1.5 GHz band.

[0023]

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

Further, since the reception signal of the first or second band is converted into the same reception IF signal by the common local oscillation signal, many circuits which can be shared for reception of different bands are included, and the size of the dual band radio communication device is small. Can be realized.

[Brief description of drawings]

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

[Explanation of symbols]

 (2) ・ ・ ・ ・ ・ ・ Transmission system IF circuit, (3) ・ ・ ・ ・ ・ ・ Mixer (transmission system 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) ・ ・ ・ ・ ・・ First receiving BPF circuit, (10) ・ ・ ・ ・ ・ Second receiving BPF circuit, (11) ・ ・ ・ ・ ・ Frequency synthesizer (local oscillation circuit for receiving), (12) ・ ・ ・ ・ ・ Mixer (receiving System mixer circuit) (13) ・ ・ ・ ・ ・ Reception system IF circuit.

Claims (2)

[Claims] 1. A local oscillation circuit for transmission (4) having an oscillation center frequency at an intermediate frequency between transmission radio frequencies of the first and second bands, and an output of the local oscillation circuit for transmission (4), The transmission mixer circuit (3) for up-converting the transmission intermediate frequency signal into the radio frequency signals of the first and second bands, and the first signal from the output signal of the transmission mixer circuit (3)
The first filter circuit (5) for extracting the signal of the band and the second signal from the output signal of the transmitting mixer circuit (3).
A second band wireless communication device comprising: a second filter circuit (6) for extracting a signal of the band. 2. A receiving local oscillator circuit (14) having an oscillation center frequency at a frequency substantially in the middle of the receiving radio frequencies of the first and second bands, and an output of the receiving local oscillator circuit (14), A dual-band wireless communication device comprising: a reception system mixer circuit (12) for down-converting the first and second band radio frequency signals into reception intermediate frequency signals.