JP3178745B2 - Wireless telephone equipment - 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 telephone device capable of receiving a frequency band different from a frequency band used for a radio telephone.

[0002]

2. Description of the Related Art In recent years, miniaturization and solidification of radio equipment have been progressing, and in particular, reduction in size and weight of mobile radio telephone equipment represented by automobile telephones and mobile telephones has been remarkable. These mobile radiotelephone devices usually use frequencies in the VHF band or UHF band, and mainly use the FM (frequency modulation) system as a radio wave format. A phase-locked loop (hereinafter abbreviated as PLL) is often used as a local oscillator of these wireless telephone devices.

Further, the above-mentioned radio telephone apparatus such as a car telephone adopts a duplex system in which transmission and reception are simultaneously performed at different frequencies so that transmission and reception can be performed simultaneously. For two-way communication represented by such a radio telephone, a communication system for performing one-way information transmission from a base station called a television, a radio broadcast, a pager, a pager, or the like to a mobile station has been developed. In such a system, a frequency band different from that of a wireless telephone is generally assigned.

Hereinafter, a conventional wireless telephone device will be described. FIG. 5 is a block diagram showing a configuration of a conventional wireless telephone device. In FIG. 5, 1 is an antenna duplexer for sharing one antenna A for transmission and reception.
Bandpass filter 101 having a reception frequency band as a passband
And a band pass filter 10 having a transmission frequency band as a pass band.
And 2. A high-frequency amplifier 2 amplifies a received signal to a required level. Reference numeral 3 denotes a first local oscillator.
And a PLL shown in the block diagram of FIG. This PLL is constructed by a commonly known technique, and includes a reference oscillator 19, frequency dividers 20, 21, a phase comparator 22, a low-pass filter 23, and a voltage controlled oscillator (hereinafter abbreviated as VCO) 24. And operates so that the output frequencies of the frequency dividers 20 and 21 match. That is, if the oscillation frequency of the reference oscillator 19 is f _x , the division ratio of the divider 20 is M, and the division ratio of the divider 21 is N, V
Oscillation frequency of CO24, i.e. the output frequency f _o of the first local oscillator 3 is expressed as follows.

[0005]

(Equation 1)

When frequency modulation is directly performed by a local oscillator for transmission, a modulation signal is applied to the VCO 24 by an output from the audio processing circuit 12 as shown by a broken line in FIG.

Further, in FIG. 5, reference numeral 4 denotes a first mixer for mixing the outputs of the first local oscillator 3 and the high-frequency amplifier 2 to convert the output to a first intermediate frequency. A band-pass filter for extracting only the intermediate frequency,
Reference numeral 6 denotes a first intermediate frequency amplifier, and reference numeral 7 denotes a second local oscillator, for example, a crystal oscillator. Reference numeral 8 denotes a second mixer that mixes the outputs of the second local oscillator 7 and the first intermediate frequency amplifier 6 and converts the output to a second intermediate frequency. 9 denotes that only the second intermediate frequency is extracted from the output of the second mixer 8. A band-pass filter, 10 is a second intermediate frequency amplifier, 11 is a demodulator that demodulates the second intermediate frequency signal and converts it into an audio signal, 12 is an output signal of the demodulator 11 and an audio signal from the microphone M, Processing such as band limitation, amplitude limitation, pre-emphasis, and de-emphasis is performed, and the speaker S and the demodulator 11
And 13 is a local oscillator, which is constituted by a PLL shown in FIG. 6, generates a transmission carrier, and frequency-modulates the carrier with the audio signal processed by the audio processing circuit 12 to convert the transmission signal. obtain. Reference numeral 14 denotes a high-frequency amplifier, which amplifies a transmission signal obtained by the local oscillator 13 to a required transmission power.

[0008] The operation of the conventional wireless telephone device configured as described above will be described below.

As apparent from FIG. 5, the receiving section is of a superheterodyne type. The received signal induced by the antenna A is input to the high-frequency amplifier 2 via the duplexer 1, amplified to a required level, and input to the first mixer 4. Here, if the frequency configuration of the lower heterodyne is adopted, the frequency of the desired received wave is f _r , and the first intermediate frequency is f
_IF, when the oscillation frequency of the first local oscillator 3 is denoted by f _o, a first local oscillator 3 if caused to oscillate f _o determined by the following equation, the received wave hope is frequency-converted into first intermediate frequency.

[0010]

[Number 2] f _o = f _r - f determined by the formula of the _IF, ie the number 2 f _o and made so that the number 1 in the formula of N
And the values of M, ie, the frequency dividers 20 and 21 in FIG.
Is set by control means such as a microcomputer. Since the output of the first mixer 4 includes frequency components other than the converted desired reception wave, the output is filtered by the band-pass filter 5 to extract only the desired reception wave component. Then, the signal is amplified by the first intermediate frequency amplifier 6 and further converted to the second intermediate frequency by the second local oscillator 7, the second mixer 8, and the band-pass filter 9,
After being amplified to a required level by the second intermediate frequency amplifier 10, it is demodulated by the demodulator 11. The demodulated audio signal is subjected to processing such as de-emphasis in the audio processing circuit 12, and then amplified and output to the speaker S or the like.

On the other hand, an audio signal input from a microphone M or the like is subjected to processing such as pre-emphasis, amplitude limitation, and band limitation in an audio processing circuit 12 and then input to a local oscillator 13. The local oscillator 13 oscillates a carrier wave of a transmission frequency and generates a directly frequency-modulated transmission signal from the audio signal. The transmission signal obtained by the local oscillator 13 is amplified to a required transmission power by the high-frequency amplifier 14 and radiated from the antenna A through the antenna duplexer 1 into the air.

[0012]

However, the above-mentioned conventional radio telephone apparatus cannot receive communication, broadcast, and the like of frequencies other than the frequency band used for the radio telephone. Assume that the band-pass filter 10 of the antenna duplexer 1 shown in FIG.
Even if the band 1 is changed to pass a desired frequency other than the frequency band used for the radio telephone, the oscillating frequency range of the first local oscillator 3 is limited, so that the frequency used for the radio telephone is limited. There has been a problem that frequencies far away from the band cannot be received.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a radio telephone device capable of receiving a frequency band different from a radio telephone frequency band with a simple configuration.

[0014]

According to the present invention, in order to achieve the above object, when receiving a frequency band different from the frequency band of a radio telephone, the output of a transmitting local oscillator is branched and mixed with a received signal. And a switch circuit for controlling the opening and closing of the output signal of the branched transmitting local oscillator in order to convert the output signal to the frequency band of the wireless telephone or a nearby frequency.

[0015]

According to the present invention, when a frequency band different from the frequency band of a radio telephone is received, the output is mixed with a received signal by using the output of the local oscillator for transmission, and the frequency band of the radio telephone is set close to the frequency band. Since the frequency is converted to a frequency, a frequency band different from the frequency band of the wireless telephone can be received.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a wireless telephone device according to a first embodiment of the present invention. In FIG. 1, the same functional blocks as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. However, functional blocks different from those in FIG. 5 will be described below. The high-frequency amplifier 2 amplifies the received signal to a required level, and operates as a mixer when receiving a frequency other than the frequency band of the radio telephone. this is,
For example, a common-source amplifier circuit using a field-effect transistor (hereinafter abbreviated as FFT) is preferable. Also, the third-order distortion is small as a high-frequency amplifier, and the second-order mixer is 2
Although the secondary distortion is required, the primary and secondary components are dominant in the transfer characteristics of the FET, and the tertiary component is extremely smaller than that of the bipolar transistor. Reference numeral 15 denotes a switch circuit, which controls opening and closing of the output of the branched local oscillator 13 and supplies the output to the high-frequency amplifier 2, and can be realized by, for example, a circuit using an FET shown in FIG.

In FIG. 2, reference numeral 150 denotes an FET having a junction type depression type static characteristic. 151 and 152 are capacitors for blocking DC, 153 is FE
A drain load resistance of T150, 154 is an input terminal, 155 is an output terminal, and 156 is a control input terminal, which performs opening / closing control by changing the DC potential of the terminal.

That is, if a DC voltage of 0 V or less and a voltage of the pinch-off voltage of the FET 150 or more is applied to the control input terminal 156, the circuit of FIG. 2 operates as a normal source-grounded amplification circuit, and the signal applied to the input terminal 154 is output. The signal is transmitted to the terminal 155.

On the other hand, if a DC voltage equal to or less than the pinch-off voltage of the FET 150 is applied to the control input terminal 156, the forward transfer admittance (mutual conductance) of the FET becomes 0 and no signal appears at the output terminal 155. Therefore, the circuit of FIG. 2 operates as a switch circuit. If the output level of the local oscillator 13 is too high or too low as the injection level of the high-frequency amplifier 2 also serving as a mixer, the gain of the circuit can be varied by adjusting the voltage at the control input terminal 156. It can also be adjusted to the injection level.

The operation of the wireless telephone device configured as described above will be described below. First, when transmitting and receiving in the frequency band of a radio telephone, the switch circuit 15 is turned off, and the output of the local oscillator 13 is not injected into the high frequency amplifier 2. Therefore, the configuration is completely equivalent to the configuration of the conventional wireless telephone device in FIG. 5, and operates exactly the same. For example the receiving frequency f _r = 800 [MHz], the transmission frequency f _t = 850 [MHz], the first intermediate frequency f _IF = 45 [MHz], the first local oscillation frequency f _o = 755 [MHz] when.

Next, when a frequency other than the frequency band of the radio telephone is received, the power of the high-frequency amplifier 14 is turned off and no radio wave is emitted. Further, the modulation signal from the audio processing circuit 12 to the local oscillator 13 is stopped. And switch circuit 15
Is turned on, and the output of the local oscillator 13 is injected into the high-frequency amplifier 2. Therefore, the received signal is mixed with the signals of both the local oscillator 13 and the first local oscillator 3 and converted into the first intermediate frequency _fIF . Therefore, each frequency relationship is

[0023]

| F _t ± _fr | −f _o = f _IF For example, at the first intermediate frequency f _IF = 45 [MHz], fr _r
= 80 MHz, for example, f _t = 860 [MH
z] and f _o = 735 [MHz]. When a signal of 1.7 GHz is received, for example, f _t = 870 [MHz] and f _o = 78
Set it to 5 [MHz]. Generally, the narrower the variable range of the local oscillator, the easier it is to obtain good characteristics such as stability and noise.Therefore, the frequency of the transmission / reception frequency interval of the wireless telephone (50 MHz in the above example) or the frequency of the sum of the transmission / reception frequencies
It is suitable for receiving a frequency near (1.65 GHz in the above example).

FIG. 3 is a block diagram showing a configuration of a wireless telephone device according to a second embodiment of the present invention. In FIG. 3, the functional blocks except for the high-frequency amplifier 16 and the first mixer 4 are exactly the same as those in the first embodiment shown in FIG.
16 is a high frequency amplifier for amplifying a received signal of a frequency other than the frequency band of the radio telephone to a required level, 4 is a first mixer,
When receiving a reception signal of a radio telephone, the radio frequency amplifier 2
Is mixed with the output of the first local oscillator 3 and converted into a first intermediate frequency signal. When a received signal having a frequency other than the frequency band of the radio telephone is received, the output from the high frequency amplifier 16 is output. The received signal thus obtained is mixed with the output of the first local oscillator 3 and the signal from the local oscillator 13 and converted into a first intermediate frequency signal.

The first mixer 4 that mixes the two signals and the three signals generates a second-order distortion and a third-order distortion, and preferably has little higher-order distortion after the fourth order. Therefore, a simple one using a diode or a bipolar transistor is preferable, and can be realized by, for example, the circuit shown in FIG.

In FIG. 4, 400 is a bipolar transistor, 401 is an input terminal to which the output of the high frequency amplifier 16 is connected, 402 is an input terminal to which the output of the high frequency amplifier 2 is connected, and 403 is the output of the switch circuit 15, ie, the local oscillator. 13
404 is an injection terminal to which a signal from the first local oscillator 3 is input, 405 is an output terminal, 406 is a capacitor for blocking direct current, and 407 is a bias current to the bipolar transistor 400. , 408 is an emitter resistor, and 409 is a collector load choke, which is a coil having a sufficiently high impedance at the first intermediate frequency. The reception signal input from the input terminal 401 or 402 is mixed with the local oscillation signal injected from the injection terminals 403 and 404, and the bipolar transistor
The nonlinear characteristic of the 400 is converted to an intermediate frequency f _IF obtained by the numerical formula 3.

The operation of the wireless telephone device configured as described above will be described below.

First, when transmitting and receiving in the frequency band of the radio telephone, the power supply of the high-frequency amplifier 16 is turned off and the switch circuit 15 is also turned off. It is not injected into the mixer 4. Therefore, the configuration is completely equivalent to the configuration of the conventional wireless telephone device in FIG. 5, and operates exactly the same.

Next, when receiving a frequency other than the frequency band of the radio telephone, the power of the high-frequency amplifier 14 is turned off and no radio wave is emitted. Further, the modulation signal from the audio processing circuit 12 to the local oscillator 13 is stopped. And switch circuit 15
Is on, the power supply of the high frequency amplifier 2 is off, and the power supply of the high frequency amplifier 16 is on. Therefore, the received signal is amplified by the high-frequency amplifier 16, mixed with the signals of both the local oscillator 13 and the first local oscillator 3 by the first mixer 4, and converted into the first intermediate frequency _fIF . Therefore, each frequency relationship is given by the following equation.
The same relationship as shown in the equation holds, and reception is possible as in the embodiment of FIG.

As described above, by independently providing the high-frequency amplifier on the receiving side for each frequency band, it is possible to adopt a dedicated element or circuit configuration suitable for each frequency, and to obtain characteristics of the high-frequency amplifier such as noise figure and gain. And improved reception characteristics can be obtained.

[0031]

As described above, the wireless telephone device of the present invention can realize a wireless telephone device capable of receiving frequencies other than the frequency band of the wireless telephone simply by adding a switch circuit having a simple configuration. Also, when receiving a frequency outside the frequency band of the radio telephone, the local oscillator for transmission is used as the local oscillator for reception, so it is necessary to add a new local oscillator or mixer for frequencies other than the frequency band of the radio telephone. However, the increase in the circuit scale can be minimized as compared with the conventional wireless telephone device. Therefore, according to the present invention, it is possible to provide a wireless telephone device that is small and can receive frequencies other than the frequency band of the wireless telephone without significantly increasing the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a wireless telephone device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a switch circuit 15 of FIG.

FIG. 3 is a block diagram illustrating a configuration of a wireless telephone device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of the first mixer 4 of FIG.

FIG. 5 is a block diagram illustrating a configuration of a conventional wireless telephone device.

FIG. 6 is a block diagram illustrating a configuration of a PLL circuit.

[Explanation of symbols]

2, 14, 16 ... high frequency amplifier, 3 ... first local oscillator,
4: first mixer, 5, 9: band-pass filter, 6:
1st intermediate frequency amplifier, 7 ... second local oscillator, 8 ... second mixer, 10 ... second intermediate frequency amplifier, 11 ... demodulator,
12 ... Sound processing circuit, 13 ... Local oscillator, 15 ... Switch circuit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/40

Claims (2)

(57) [Claims] 1. A high-frequency amplifier for amplifying a signal received from an antenna, the high-frequency amplifier including the high-frequency amplifier, a receiver for converting the received signal to obtain a demodulated output, and at least one local oscillator, A transmission unit that generates a transmission signal and sends the transmission signal to an antenna; and a switch circuit that receives an output of a local oscillator of the transmission unit and opens and closes an output signal of the local oscillator. When receiving a frequency other than the band, the output of the local oscillator of the transmission unit, which is controlled to be opened and closed by the switch circuit, is injected into the high-frequency amplification unit of the reception unit, and the high-frequency amplification unit operates as a mixer. Characteristic wireless telephone device. 2. A high-frequency amplifier for amplifying a signal received from an antenna, the high-frequency amplifier including the high-frequency amplifier, a receiver for converting the received signal to obtain a demodulated output, and at least one local oscillator, A transmission unit that generates a transmission signal and sends the transmission signal to an antenna; and a switch circuit that receives an output of a local oscillator of the transmission unit and opens and closes an output signal of the local oscillator. When receiving a frequency other than a band, an output of a local oscillator of the transmitting unit, which is controlled to be opened and closed by the switch circuit, is injected into a frequency converting unit of the receiving unit.