JP3610080B2 - Arm-mounted radio - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a local oscillating circuit of an arm-mounted radio.
[0002]
[Prior art]
Conventionally, as a resonant element used for a local oscillation circuit of a small portable radio, a VCO (voltage controlled oscillator) using a crystal resonator for a fixed frequency and a PLL (Phase Lock Loop) for a plurality of frequencies is used. It is used. Both have highly stable oscillation characteristics and are widely used.
[0003]
Even in the wrist-worn radio, a selective call receiver used at a fixed frequency has been commercialized. A resonant element used in these local oscillation circuits is a crystal resonator.
[0004]
A surface acoustic wave element (SAW device) is widely used as an element for attenuating unnecessary signals in a narrow band, such as an RF filter.
[0005]
[Problems to be solved by the invention]
The oscillation frequency of the local oscillation circuit using a crystal resonator is generally 3rd to 5th order overtone vibration due to the relationship between the fundamental vibration mode of the crystal and low power consumption, and this frequency becomes the fundamental frequency. Multiply by the circuit to obtain the desired output signal.
[0006]
For this reason, an unnecessary oscillation signal is generated in the multiplier circuit section. Unwanted oscillation appears as spurious interference (unnecessary signal interference) to the receiver, which may deteriorate the characteristics of the radio.
[0007]
Conventionally, these unnecessary oscillations have been suppressed by narrow-band bandpass filters, but large parts such as filters can no longer be introduced due to space limitations due to the miniaturization of radios, and spurious characteristics are sacrificed. There was a problem that has been made.
[0008]
On the other hand, the SAW device may be used as a resonator by utilizing the narrow band property.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, an arm-mounted radio device according to the present invention includes an antenna element having a predetermined selectivity and a radio transmission / reception circuit unit. The wireless transmission / reception circuit unit includes a local oscillation circuit and a frequency conversion circuit, and the frequency conversion circuit frequency-converts a transmission / reception signal by a direct conversion method using an output signal of the local oscillation circuit, and the local oscillation circuit The circuit is used in a local oscillation element composed of a surface acoustic wave element, and in a region where the gain decreases as the frequency increases, and the oscillation signal of the local oscillation element is feedback-amplified to obtain a frequency substantially equal to the frequency of the transmission / reception signal. Feedback amplifier means for outputting as the output signal, and a coupling capacitor for transmitting the output signal to the frequency conversion circuit via a terminal portion, and the length of the antenna element is that of the wireless transmission / reception circuit portion It is set to have a resonance curve characteristic sufficient to selectively pass the received frequency component in cooperation with the capacitive component,
A power supply control circuit for controlling power supply to the wireless transmission / reception circuit unit and the waveform shaping circuit;
And a control unit that supplies power to the power control circuit to the radio transmission / reception circuit unit and the waveform shaping circuit only during a time during which a signal is received.
[0012]
The present invention provides a circuit configuration that dramatically improves spurious interference characteristics even in an ultra-small radio such as an arm-mounted radio.
[0013]
【Example】
Hereinafter, details of the present invention will be described by way of examples.
[0014]
FIG. 1 is a circuit diagram showing a local oscillation circuit unit of an arm-mounted radio device according to the present invention. A surface acoustic wave element (SAW resonator) 1 is a characteristic part of the present invention. The SAW resonator is characterized in that the reactance is inductive and close to zero at several hundred MHz compared to a conventional crystal resonator, and the loss in the vicinity is very small. Furthermore, it has a high Q and can be used as a local oscillation element.
[0015]
In FIG. 1, a variable capacitor 2 is an element for adjusting the oscillation frequency. Although this circuit is a Colpitts type oscillation circuit, the capacitors 4, 5, and 7 are elements for applying feedback to a signal in order to constitute a resonance circuit. The transistor 3 is an element for amplifying the feedback signal. The resistors 6, 8, and 9 are elements for applying a bias to the transistor 3. The terminal 14 is a terminal for applying a DC voltage. The capacitor 12 is a coupling capacitor for transmitting an output signal to the mixing circuit 16. The terminal 13 is a terminal connected to the mixing circuit 16. Since the double oscillation method using the nonlinearity of the transistor 3 is not used, the number of elements can be reduced. FIG. 2 shows a local oscillation circuit using a conventional crystal resonator, and the difference is clearly seen when compared with this. In FIG. 2, there are three inductors, but all of them can be omitted. An inductor is a so-called coil, and its volume is large compared to other elements, making it difficult to reduce the size of the device. However, the ability to omit these is very advantageous for downsizing. Resonant circuits 25 and 26 formed by inductors 10 and 22 and capacitors 11 and 23 in FIG. 2 are band-pass filters that extract an output signal used in the mixing circuit from the multiplied output signal. For example, assuming that the fundamental oscillation frequency is 90 MHz, all the multiplied output frequencies of the multiplied output appear. In practice, due to the frequency characteristics of the transistor 3, the output level decreases as the integer increases. If the required output in the mixing circuit is 270 MHz, only the output of three times the fundamental oscillation, that is, the third-order multiplication is extracted by the filter. In general, as the output becomes high frequency, the Q of the inductors 10 and 22 decreases. Therefore, the order of the filter is increased to increase the selectivity. However, an increase in order means that the number of elements increases accordingly, and an increase in loss must be taken into consideration. It is also disadvantageous in downsizing the device. On the other hand, if the order is small, an unnecessary multiplied oscillation output is difficult to attenuate, so that many multiplied outputs are input to the mixing circuit. This causes spurious interference.
[0016]
FIG. 3 shows a spurious interference generation diagram of the local oscillation circuit of the present invention, and FIG. 4 shows a spurious interference generation diagram of the conventional local oscillation circuit. As for the multiplication output by the local oscillation circuit of the present invention, 270 MHz becomes the basic oscillation output 31 and the secondary multiplication output 32 becomes 540 MHz. This is a feature of the local oscillation circuit of the present invention. Although not shown, the line frequency received by the receiver is in the vicinity of 270 MHz. The interference level 33 occurs in the vicinity of the output 31, but in the case of a superheterodyne receiver, the interference that falls to the intermediate frequency itself after frequency conversion is a steep RF filter, and is several tens KHz away from the line frequency. The interference is attenuated by the intermediate frequency filter after the frequency conversion.
[0017]
In recent years, a direct conversion method has been developed, which directly converts a line frequency into a baseband signal and has no intermediate frequency. In addition, since the local oscillation signal substantially matches the line frequency, the above-described disturbance falling to the intermediate frequency is greatly reduced compared to the superheterodyne system. The only remaining interference is the one that matches the unwanted multiplied output from the local oscillator circuit. In the case of this method, if there is no unnecessary multiplication output as described above, spurious interference can be drastically improved without an RF filter.
[0018]
In FIG. 3, there is a secondary multiplied output 32, but its level is small, and the frequency characteristic of the transistor 3 is generally used in a region where the gain decreases as the frequency increases, so that it is hardly disturbed. Further, if the bandpass filter characteristic 30 is taken into consideration, the anti-jamming characteristic is further improved. The bandpass filter refers to the resonance circuits 25 and 26 in FIG.
[0019]
In FIG. 4, in the conventional crystal oscillation circuit, 270 MHz becomes the third-order multiplied output 41, which is used in the mixing circuit, but other unnecessary multiplied output 42 also enters the mixing circuit. If the band-pass filter characteristic 30 is the same as that in FIG. Its anti-jamming ratio is only 40 dB. Since the spurious interference characteristic is determined by the level of external interference from the antenna, the level 43 is conventionally attenuated by the selectivity of the antenna and the RF filter. However, due to further downsizing of the device, the room for inserting the RF filter is reduced, and the selectivity of the antenna is not large at present.
[0020]
By utilizing the present invention, large parts such as an RF filter or an inductor can be omitted from a radio device using the direct conversion method, and further miniaturization can be promoted. This has a great advantage for an arm-mounted radio.
[0021]
FIG. 5 is a block diagram of the RF circuit unit of the wrist-worn radio according to the present invention. The signal received by the antenna 50 is amplified by the high frequency amplifier circuit 51, mixed by the mixing circuit 52 with the necessary multiplied output signal from the local oscillation circuit 53, and converted into an IF signal. The intermediate frequency filter 54 is for improving channel selectivity characteristics near the reception frequency. A detection circuit and a data decoder circuit follow the terminal 55. Details will be described with reference to FIG.
[0022]
Conventionally, an RF filter has been inserted after the high-frequency amplifier circuit 51 in order to improve spurious interference characteristics. However, if the local oscillation circuit of the present invention is used, the RF filter can be omitted. In particular, a radio device using a direct conversion method is very effective because image interference, which is one of spurious interference, does not occur in principle.
[0023]
FIG. 6 shows an external view of the wrist-worn radio of the present invention. A buckle fitting 61 is used to attach to the arm, and a positioning rod 62 for changing the band length is inserted into the hole 63. The surplus band is fastened with a band clamp 65. The main body 66 includes a display unit 67 and a button switch 68, and can check or change reception information and time information. This form is also used for ordinary watches. An antenna is incorporated in the bands 64a and 64b to receive the line frequency.
[0024]
FIG. 7 is a circuit block diagram of the wrist-worn radio of the present invention. The wireless device of this embodiment includes the antenna 101, the transmission / reception wireless unit 102, and the waveform shaping circuit 103 described above. Further, a power supply control circuit 104 that controls power supply to the wireless unit 102 and the waveform shaping circuit 103 and a control unit 105 that controls the circuit 104 are provided. The radio of the present embodiment is further described with a P-ROM (programmable read only memory) 106 in which a unique call number to be compared by the control unit 105 is described, and transmission information associated with the fixed call number. RAM (Random Access Memory) 109, LCD driving circuit 110 for controlling LCD (Liquid Crystal Display) 112 on which information is displayed, and oscillation circuit 111 for generating a clock signal used for controlling the driving circuit 110 And are installed. A message processing unit 114 is configured by the power supply control circuit 104, the control unit 105, the RAM 109, the LCD drive circuit 110, and the oscillation circuit 111. An LCD 112 for displaying a message processed by the message processing unit 114, an alarm driving circuit 107 for transmitting that the message is stored, and an alarm device 108 such as a buzzer, LED or vibrator are installed. An external operation unit 113 for operating the wireless device is provided.
[0025]
In such a configuration, a signal transmitted at a predetermined line frequency is demodulated by the radio unit 102 via the antenna 101. Then, the waveform shaping circuit 103 converts it into a rectangular wave. The radio unit 102 and the waveform shaping circuit 103 are supplied with power only during the time of receiving a signal based on the control of the control unit 105 by the power control circuit 104.
[0026]
The control unit 105 generates a battery saving timing signal for managing the above power supply, controls the power supply circuit 104, and performs bit synchronization and frame synchronization with the received signal. Further, the unique call number recorded in the P-ROM 106 is compared with the rectangular wave received signal supplied from the waveform shaping circuit 103 with error control, and the stored unique call number is A determination is made whether or not it has been called. It also has a measurement function for measuring a signal from the oscillation circuit 111 which is a reference signal source such as crystal.
[0027]
When the call is confirmed, message data is received following the unique call number and stored in the RAM 109. Then, the alarm device 108 notifies the user that there has been a call through the alarm driving circuit 107. The message stored in the RAM 109 is sent to the LCD drive circuit 110 via the control unit 105 by operating the external operation unit 113 including switches, and is displayed on the LCD 112. The LCD drive circuit 110 is supplied with a clock signal from the oscillation circuit 111.
[0028]
The arm-mounted radio device of the present invention has the above configuration.
[0029]
【The invention's effect】
As described above, the wrist-worn radio of the present invention uses a surface acoustic wave element as a resonance element of the local Hanshin circuit section and adopts a direct conversion method, so compared with a superheterodyne receiver or the like. The interference that falls to the intermediate frequency can be greatly reduced. In addition, as interference that falls to the intermediate frequency, part of the interference that remains is the same as the unnecessary multiplied output from the local oscillation circuit, but the feedback amplification means is used in a region where the gain decreases as the frequency increases, and the antenna The element length is set to have a resonance curve characteristic sufficient to selectively pass the reception frequency component in cooperation with the capacitance component of the radio transmission / reception circuit unit. Can be reduced.
Therefore, since it is not necessary to use large parts such as an RF filter and an inductor in order to improve the anti-jamming characteristics, it is possible to drastically reduce the size of the radio main body and abnormal oscillation because there is no need to use an inductor. Oscillation does not occur, and oscillation by the SAW resonator is performed from the beginning, and the selectivity is maintained well.
Also, a power control circuit that controls power supply to the wireless transmission / reception circuit unit and the waveform shaping circuit, and a control for supplying power to the power transmission control circuit to the wireless transmission / reception circuit unit and the waveform shaping circuit only during the time of signal reception. Power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a local oscillation circuit unit of a wrist-worn radio according to the present invention.
FIG. 2 is a local oscillation circuit diagram using a conventional crystal resonator.
FIG. 3 is a spurious interference generation diagram of the local oscillation circuit of the present invention.
FIG. 4 is a spurious interference generation diagram of a conventional local oscillation circuit.
FIG. 5 is a block diagram of the RF circuit unit of the wrist-worn radio according to the present invention.
FIG. 6 is an external view of an arm-mounted radio device according to the present invention.
FIG. 7 is a circuit block diagram of the wrist-worn radio of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surface acoustic wave element 2 Variable capacitor 3 Transistors 4, 5, 7 Capacitors 6, 8, 9 Resistor 10 Inductor 11 Capacitor 12 Coupling capacitor 13, 14 Terminal 15 Ground 16 Mixing circuit 20 Crystal oscillator 21, 22 Inductor 23 Capacitor 24 Terminal 25, 26 Resonant circuit 30 Band pass filter characteristic 31 Basic oscillation output 32 Secondary multiplication output 33 Interference level 41 Tertiary multiplication output 42 Unnecessary multiplication output 43 Spurious interference level 50 Antenna 51 High frequency amplification circuit 52 Mixing circuit 53 Local oscillation circuit 54 Intermediate Frequency filter 55 Terminal 61 Locking bracket 62 Positioning rod 63 Hole 64a, b Band 65 Band clamp 66 Main body 67 Display unit 68 Button switch 101 Antenna 102 Transmission / reception radio unit 103 Waveform shaping circuit 104 Power supply control circuit 105 Control unit 106 P-ROM
107 Alarm drive circuit 108 Alarm device 109 RAM
110 Drive circuit 111 Oscillation circuit 112 LCD
113 External operation unit 114 Message processing unit

Claims (1)

In an arm-mounted radio including an antenna element having a predetermined selectivity, a radio transmission / reception circuit unit, and a waveform shaping circuit,
The wireless transmission / reception circuit unit includes a local oscillation circuit and a frequency conversion circuit,
The frequency conversion circuit frequency-converts a transmission / reception signal by a direct conversion method using an output signal of the local oscillation circuit,
The local oscillation circuit is used in a region where a gain decreases as the frequency increases, and a local oscillation element made of a surface acoustic wave element. Feedback amplification means for outputting as the output signal having a frequency to be coupled, and a coupling capacitor for transmitting the output signal to the frequency conversion circuit,
The length of the antenna element is set to have a resonance curve characteristic sufficient to selectively pass the component of the reception frequency in cooperation with the capacitance component of the wireless transmission / reception circuit unit,
A power supply control circuit for controlling power supply to the wireless transmission / reception circuit unit and the waveform shaping circuit;
The power supply control circuit includes a control unit that supplies power to the wireless transmission / reception circuit unit and the waveform shaping circuit only during the time of signal reception.
An arm-mounted wireless device characterized by that.

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