JP2000082958A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized communication equipment where spurious radiation from a voltage controlled oscillator is reduced. SOLUTION: A radio receiver 100 contains a high frequency reception circuit 1, an oscillation signal semiconductor chip 2, a crystal resonator 3, a frequency converter circuit 4, an intermediate frequency amplifier circuit 5, a detector circuit 6, a stereo demodulation circuit 7, an audio adjusting part 8, a power amplifier 9, a speaker 10 and an antenna 11. A frequency synthesizer 20 is made into one chip and it is treated as a single component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device for transmitting and receiving various signals using a frequency synthesizer.

[0002]

2. Description of the Related Art In radio broadcasting, a broadcasting station sends
A signal obtained by modulating an audio signal using a modulation method such as modulation or FM modulation is transmitted. For this reason, the radio receiver demodulates the received signal according to the modulation method and outputs audio from a speaker.

FIG. 8 is a diagram showing a configuration of a conventional radio receiver. The radio receiver 500 shown in the figure includes a high-frequency receiving circuit 501 that performs amplification processing and the like on a broadcast signal, a frequency synthesizer 502 that outputs a local oscillation signal mixed with the broadcast signal and controls the frequency thereof, Crystal oscillator 503 connected to synthesizer 502
And a frequency conversion circuit 50 for mixing the amplified broadcast signal with a local oscillation signal to convert the frequency of the broadcast signal into an intermediate frequency.
4, an intermediate frequency amplifying circuit 505 for amplifying the intermediate frequency broadcast signal, a detection circuit 506 for performing a predetermined detection process on the amplified intermediate frequency broadcast signal and outputting a composite signal, and an L signal from the composite signal. A stereo demodulation circuit 507 that demodulates the signal (left audio signal) and the R signal (right audio signal), an audio adjustment unit 508 that performs volume adjustment and the like on the L signal and the R signal, and outputs the result.
It includes a power amplifier 509, a speaker 510, and an antenna 511 for receiving a broadcast signal. The user can listen to a desired broadcast by instructing the radio receiver 500 to select a song, adjust the volume, and the like.

[0004]

The frequency synthesizer 502 of the above-described radio receiver 500 uses a voltage controlled oscillator (VCO) to output a local oscillation signal. In this VCO, a resonance circuit is formed by resonance elements such as inductors and capacitors. Conventionally, these resonance elements are not integrated with other circuits of the VCO or other circuits constituting the frequency synthesizer 502, but are externally attached to a printed wiring board or the like on which these circuits are formed. Was. However, when the resonance elements are externally attached, unnecessary radio waves (unnecessary radiation) may be generated from these resonance elements and leak to the outside. For this reason, the frequency synthesizer 5 including the resonance element
02 was covered with a shield member to prevent unnecessary radiation from leaking to the outside.

However, the frequency synthesizer 502
Since the entire structure is covered with a shield member, the shield member becomes large, the shield member itself plays a role of an antenna, and unnecessary radiation may leak to the outside. Further, the size of the shield member has been increased, which has hindered miniaturization of the radio receiver. Particularly, in the case of a portable radio receiver that requires miniaturization, obstruction of miniaturization has been a serious problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication device capable of reducing the size and reducing unnecessary radiation generated from a voltage controlled oscillator.

[0007]

In order to solve the above-mentioned problems, a communication apparatus according to the present invention comprises a voltage-controlled oscillator for outputting an oscillation signal used for performing a frequency conversion process on an input signal, and the oscillation device. It has a frequency synthesizer constituted by an oscillation frequency control unit for controlling the frequency of a signal, and this frequency synthesizer is integrally formed on a single semiconductor substrate. By integrally forming the frequency synthesizer on a single semiconductor substrate, the output of the voltage-controlled oscillator is reduced, so that unnecessary radiation is less likely to occur and leakage to the outside can be reduced. Also,
Since the frequency synthesizer is integrated, the size of the communication device can be reduced.

In particular, when the voltage-controlled oscillator includes an astable multivibrator, a low-frequency oscillation signal can be output. Further, since the entire voltage controlled oscillator is integrally formed on a semiconductor substrate together with other circuits constituting the frequency synthesizer, it is possible to reduce leakage of unnecessary radiation to the outside.

When the voltage-controlled oscillator is an LC oscillator, it is possible to output a high-frequency oscillation signal. In particular, by forming an inductor constituting a resonance circuit in this LC oscillator by a wiring pattern arranged on a semiconductor substrate, it is not necessary to separately provide an inductor, and the voltage-controlled oscillator as a whole constitutes a frequency synthesizer. Since it is formed integrally with the circuit on the semiconductor substrate, it is possible to reduce unnecessary radiation leakage to the outside.

Further, a frequency conversion circuit for converting the frequency of the input signal by mixing the input signal and the oscillation signal may be integrally formed together with the frequency synthesizer on a single semiconductor substrate. By integrally forming the frequency converter together with the frequency synthesizer on the semiconductor substrate, it becomes possible to reduce unnecessary radiation generated from the junction between the voltage controlled oscillator and the frequency converter.

Further, by disposing a frequency synthesizer or the like integrally formed on a semiconductor substrate inside a shield member for preventing noise radiation to the outside, unnecessary radiation generated from the voltage controlled oscillator is prevented from leaking to the outside. It can be further reduced. Further, the shield member that covers the single semiconductor substrate may be small, and the shield member itself does not play the role of an antenna, so that the communication device can be downsized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radio receiver according to an embodiment to which the present invention is applied is characterized in that a frequency synthesizer is integrally formed on a single semiconductor substrate. Hereinafter, a radio receiver according to an embodiment will be described with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of a radio receiver. A radio receiver 100 shown in FIG. 1 is for receiving an AM broadcast or an FM broadcast, and includes a high-frequency receiving circuit 1, an oscillation signal semiconductor chip 2, a crystal oscillator 3,
Frequency conversion circuit 4, intermediate frequency amplification circuit 5, detection circuit 6,
It includes a stereo demodulation circuit 7, an audio adjustment unit 8, a power amplifier 9, a speaker 10, and an antenna 11.

The high-frequency receiving circuit 1 includes an antenna tuning circuit and a high-frequency amplifier, performs high-frequency amplification on a broadcast signal input from the antenna 11, and outputs the amplified broadcast signal.

The oscillation signal semiconductor chip 2 has a frequency synthesizer 20 formed on a single semiconductor substrate such as silicon. That is, the entire frequency synthesizer 20 is integrated into one chip, and is treated as a single component.

The frequency synthesizer 20 includes a voltage controlled oscillator (VCO) 21 for outputting a local oscillation signal, a frequency divider 22 as an oscillation frequency control unit for controlling the frequency of the local oscillation signal, a reference oscillator 23, and a phase comparator. And a low-pass filter (LPF) 25.

The VCO 21 outputs a local oscillation signal. The VCO 21 includes an astable multivibrator suitable for oscillating a low-frequency signal in a radio receiver that receives a low-frequency broadcast signal such as an AM broadcast. In a radio receiver for receiving a high-frequency broadcast signal such as an FM broadcast, an LC oscillator suitable for oscillating a high-frequency signal is used as the VCO 21.

FIG. 2 is a diagram showing a detailed configuration of the VCO 21 including the astable multivibrator.
The VCO 21 shown in the figure includes an astable multivibrator 41 that performs an oscillating operation, a constant current circuit 42 that controls the free-running frequency of the astable multivibrator 41, transistors 43 and 44 for clamping, and a transistor 45 for buffer. And bias transistors 46 and 47, and is connected to an LPF 25 that applies a control voltage to the VCO 21.

The astable multivibrator 41 includes transistors 51 and 52 and a timing capacitor 53. The source terminals of the transistors 51 and 52 are connected by a timing capacitor 53. The drain terminal of the transistor 51 and the gate terminal of the transistor 52 are connected to the source terminal of the clamping transistor 43. The gate terminal of the transistor 51 and the drain terminal of the transistor 52 are connected to the source terminal of the clamping transistor 44 and the buffer transistor. 45 gate terminals. The astable multivibrator 41 performs an oscillating operation by turning on / off the transistors 51 and 52 alternately.

The constant current bias circuit 42 includes transistors 54 and 55. Transistor 54
Is connected to the source terminal of the transistor 51, and the drain terminal of the transistor 55 is connected to the source terminal of the transistor 52. The gate terminals of the transistors 54 and 55 are LPF2
5 and each source terminal is grounded.

The timing at which the transistors 51 and 52 of the astable multivibrator 41 are turned on / off alternately;
That is, the free-running frequency changes according to the voltage applied from the LPF 25 to the gate terminals of the transistors 54 and 55 of the constant current bias circuit 42. Therefore, LPF25
, The free-running frequency, that is, the oscillation frequency of the VCO 21 can be controlled.

FIG. 3 shows a VCO using an LC oscillator.
FIG. 21 is a diagram illustrating a detailed configuration of a first embodiment. VCO2 shown in FIG.
Reference numeral 1 denotes a clap-type oscillation circuit, which includes a resonance circuit 61. The resonance circuit 61 includes an inductor 71 and a variable capacitance diode 72. The inductor 71 is formed by spirally forming a part of a wiring pattern used for the VCO 21 among wiring patterns arranged on a semiconductor substrate of the oscillation signal semiconductor chip 2. The cathode terminal of the variable capacitance diode 72 is connected to the LPF 25, and the LPF 2
The capacitance changes according to the reverse control voltage applied by 5. When the capacitance of the variable capacitance diode 72 changes, the resonance frequency of the resonance circuit 61, that is, the VCO 21
Oscillation frequency changes. Therefore, the oscillation frequency of the VCO 21 can be controlled by changing the control voltage applied to the variable capacitance diode 72 by the LPF 25.

The VCO 21 has the above-described configuration. Next, the operation of the frequency synthesizer 20 including the VCO 21 will be described. For example, if the VCO 21 has the frequency N
If it is necessary to output a × fr local oscillation signal,
First, when the VCO 21 outputs a local oscillation signal having the frequency fosc, the frequency divider 22 converts the local oscillation signal into the frequency fosc.
The signal is divided into c / N signals and output to the phase comparator 24. On the other hand, the reference frequency divider 23 outputs a signal of the frequency fr determined by the crystal oscillator 3 to the phase comparator 24. The phase comparator 24 outputs the frequency fosc / N output from the frequency divider 22.
Is compared with the signal of the frequency fr output from the reference oscillator 23 to determine the phase difference, and outputs a signal having a duty ratio according to the comparison result. The LPF 25 outputs a control voltage corresponding to the signal output from the phase comparator 24 to V
This is fed back to CO21. The VCO 21 changes the oscillation frequency by the feedback control voltage so that fosc / N is equal to fr, that is, fosc is equal to N × fr, and outputs a local oscillation signal of frequency N × fr. .

The frequency conversion circuit 4 mixes the amplified broadcast signal output from the high-frequency receiving circuit 1 with the local oscillation signal output from the VCO 21 to output an intermediate frequency signal whose frequency is converted from the broadcast signal. . For example, FM
In a radio receiver for receiving a broadcast, when a desired broadcast signal to be received is input to the frequency conversion circuit 4,
By mixing this signal with the local oscillation signal output from the VCO 21, the signal is converted into an intermediate frequency signal of 10.7 MHz.

The intermediate frequency amplification circuit 5 includes a frequency conversion circuit 4
Amplifies the intermediate frequency signal output from the controller and performs a tuning operation. The detection circuit 6 performs a detection process on the amplified intermediate frequency signal output from the intermediate frequency amplification circuit 5 and outputs a composite signal.

The stereo demodulation circuit 7 demodulates the L signal and the R signal from the composite signal output from the detection circuit 6. The audio adjustment unit 8 adjusts the volume and sound quality of the L signal and the R signal output from the stereo demodulation circuit 7. Specifically, the audio adjustment unit 8 includes a power amplifier 9 at a subsequent stage.
, The volume of the L signal and the R signal is adjusted. The audio adjustment unit 8 adjusts the sound quality of the L signal and the R signal by changing the resistance value of a built-in variable resistor (not shown) for adjusting the sound quality. The power amplifier 9 includes the audio adjustment unit 8 described above.
The L signal and the R signal are amplified according to the gain adjusted by the above. These amplified L and R signals are output as audio from the speaker 10.

As described above, the radio receiver 1 of the present embodiment
Reference numeral 00 denotes an oscillation signal semiconductor chip 2 in which the circuits constituting the frequency synthesizer 20 are formed on a single semiconductor substrate. That is, the frequency synthesizer 20
Are integrated into one chip and handled as a single component. By integrating the frequency synthesizer 20 into one chip, the VCO
Since the output of 21 is low power, unnecessary radiation hardly occurs, and leakage to the outside can be reduced. Further, since the frequency synthesizer 20 is integrated, the size of the radio receiver 100 can be reduced.

In particular, when the VCO 21 is configured using the astable multivibrator 41, it becomes possible to output a low-frequency oscillation signal suitable for receiving AM broadcast, for example. In addition, by using the astable multivibrator 41, the entire VCO 21 can be connected to the oscillation signal semiconductor chip 2.
Therefore, leakage of unnecessary radiation to the outside can be reduced.

When the LC oscillator is used as the VCO 21, it is possible to output a high-frequency oscillation signal suitable for receiving FM broadcasts, for example. In particular, by forming the inductor 71 constituting the resonance circuit 61 in the LC oscillator by a wiring pattern arranged on the semiconductor substrate of the oscillation signal semiconductor chip 2, it is not necessary to separately provide an inductor, and the entire VCO 21 can be used. Since it can be included in the oscillation signal semiconductor chip 2, leakage of unnecessary radiation to the outside can be reduced.

In the above-described embodiment, only the entire frequency synthesizer 20 is integrated into one chip. However, as in the radio receiver 200 shown in FIG. 4, a frequency conversion circuit 4 connected to the frequency synthesizer 20 is also included. Thus, the oscillation signal semiconductor chip 30 may be configured. By integrating the frequency synthesizer 20 and the frequency conversion circuit 4 into one chip, it is possible to reduce unnecessary radiation generated from the junction between the VCO 21 and the frequency conversion circuit 4.

Also, as in the case of the oscillation signal semiconductor chip 35 shown in FIG. 5, the frequency synthesizer 20 is arranged inside a shield member 36 such as a resin mold for preventing noise radiation to the outside, so that the VCO 21 Leakage of unnecessary radiation generated from the outside can be further reduced.

When the frequency synthesizer 20 and the frequency conversion circuit 4 are integrated into a single chip, the frequency synthesizer 20 and the frequency conversion circuit are provided inside a shield member 38, as in an oscillation signal semiconductor chip 37 shown in FIG. By arranging 4, the leakage of unnecessary radiation generated from VCO 21 to the outside can be further reduced.

In the above-described embodiment, the LPF 25 is built in the oscillation signal semiconductor chips 2 and 30.
When the area occupied by the capacitor included inside F25 increases (when a large time constant is required), the LPF
25 may be connected to the outside of the oscillation signal semiconductor chip 2.

In the above-described embodiment, a radio receiver for receiving an AM broadcast or an FM broadcast is used as a receiver, but other media such as a radio receiver for receiving a PCM broadcast or the like, a television receiver, or the like. Receiver for receiving
Alternatively, the present invention can be applied to a receiver that receives a signal other than a broadcast signal. In these cases, similarly, each circuit constituting the frequency synthesizer may be integrally formed on a single semiconductor substrate.

The present invention can be similarly applied to a transmitter for transmitting various signals. FIG. 7 is a diagram showing a partial configuration of a transmitter according to an embodiment to which the present invention is applied. The transmitter 300 shown in FIG. 3 is a portion obtained by extracting a portion for performing a transmission process in a mobile phone, and includes a transmission signal processing circuit 301, a modulator 302, an oscillation signal semiconductor chip 303, a crystal oscillator 304, and a frequency conversion circuit. 30
5, transmission power amplifier 306, and antenna 307.

The transmission signal processing circuit 301 performs various kinds of signal processing such as amplitude limiting processing on an audio signal output from a transmitter (not shown) and outputs a baseband signal. The modulator 302 modulates a predetermined high-frequency signal with the baseband signal.

The oscillation signal semiconductor chip 303 has a frequency synthesizer 320 formed on a single semiconductor substrate. That is, the frequency synthesizer 320 is integrated into one chip and handled as a single component.

The frequency synthesizer 320 has the same configuration as the frequency synthesizer 20 shown in FIG.
It includes a VCO 321, a frequency divider 322, a reference oscillator 323, a phase comparator 324, and an LPF 325. The frequency synthesizer 320 performs a phase comparison between a signal obtained by dividing the oscillation signal output from the VCO 321 and a reference frequency signal determined by the crystal oscillator 304, and according to the comparison result, the VCO
By changing the control voltage applied to H.321,
The frequency of the oscillation signal output from the VCO 321 is controlled.

The frequency conversion circuit 305 mixes the modulated high-frequency signal output from the modulator 302 with the oscillation signal output from the frequency synthesizer 320, thereby changing the frequency of the high-frequency signal to a predetermined frequency (for example, 80
The signal is converted to a frequency of 0 MHz band or 1.5 GHZ band, and a signal (transmission signal) after the frequency conversion is output.

The transmission power amplifier 306 amplifies the power of the transmission signal output from the frequency conversion circuit 305. The power-amplified transmission signal is transmitted from antenna 307 to the base station.

As described above, the transmitter 300 of the present embodiment
Is to form each circuit constituting the frequency synthesizer 320 on a single semiconductor substrate,
02. That is, the frequency synthesizer 3
20 are integrated into one chip and handled as a single component. Therefore, like the radio receiver 100 shown in FIG.
Since the output of the VCO 321 is low power, unnecessary radiation is less likely to occur, and leakage to the outside can be reduced. Further, since the frequency synthesizer 320 is integrated, the size of the transmitter 300 can be reduced.

[0042]

As described above, according to the present invention, the frequency synthesizer constituted by the voltage controlled oscillator and the oscillation frequency control unit is integrally formed on a single semiconductor substrate, and the output of the voltage controlled oscillator is Since the power is reduced, unnecessary radiation hardly occurs, and leakage to the outside can be reduced. Further, since the frequency synthesizer is integrated, the size of the communication device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a radio receiver according to an embodiment.

FIG. 2 is a diagram showing a detailed configuration of a VCO including an astable multivibrator.

FIG. 3 is a diagram showing a detailed configuration of a VCO using an LC oscillator.

FIG. 4 is a diagram illustrating an example of a radio receiver including an oscillation signal semiconductor chip further including a frequency conversion circuit connected to a VCO;

FIG. 5 is a diagram showing an oscillation signal semiconductor chip in which a frequency synthesizer is arranged inside a shield member.

FIG. 6 is a diagram showing an oscillation signal semiconductor chip in which a frequency synthesizer and a frequency conversion circuit are arranged inside a shield member.

FIG. 7 is a diagram illustrating a partial configuration of a transmitter according to an embodiment.

FIG. 8 is a diagram showing a configuration of a conventional radio receiver.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 high-frequency receiving circuit 2 semiconductor chip for oscillation signal 3 crystal oscillator 4 frequency conversion circuit 20 frequency synthesizer 21 voltage-controlled oscillator (VCO) 41 astable multivibrator 61 resonance circuit 100 radio receiver

Continued on front page F-term (reference)

Claims (7)

[Claims] 1. A frequency synthesizer comprising: a voltage-controlled oscillator that outputs an oscillation signal used when performing frequency conversion processing on an input signal; and an oscillation frequency control unit that controls the frequency of the oscillation signal. Wherein the frequency synthesizer is integrally formed on a single semiconductor substrate. 2. The communication device according to claim 1, wherein the voltage-controlled oscillator includes an astable multivibrator. 3. The communication device according to claim 1, wherein the voltage controlled oscillator is an LC oscillator. 4. The communication device according to claim 3, wherein an inductor used for a resonance circuit in the LC oscillator is formed by a wiring pattern on the semiconductor substrate. 5. The frequency conversion circuit according to claim 1, further comprising: a frequency conversion circuit configured to mix the input signal and the oscillation signal output from the voltage controlled oscillator to convert a frequency of the input signal. A communication device, wherein the frequency conversion circuit is integrally formed on the semiconductor substrate together with the frequency synthesizer. 6. The communication device according to claim 1, further comprising a shield member for preventing noise radiation to the outside, wherein the frequency synthesizer is arranged inside the shield member. 7. The communication device according to claim 5, further comprising a shield member for preventing noise radiation to the outside, wherein the frequency synthesizer and the frequency conversion circuit are arranged inside the shield member.