JPH08317002A - Communication equipment by quadrature modulation system - Google Patents

Abstract

PURPOSE: To enhance the modulation accuracy and to use different systems in common by setting a phase difference of 90 deg. of two carrier waves for quadrature modulation with high accuracy. CONSTITUTION: A local oscillator 2F with a frequency twice a carrier frequency is provided onto a same device as a quadrature modulation circuit 2 and the local oscillator 2F and a phase comparator 24 form a PLL to generate a signal synchronously with an output clock of a crystal oscillator 25. The signal is given to a 90 deg. shifter 2C, in which the signal is 1/2 frequency-divided to generate two carrier waves whose phase difference is 90 deg., they are multiplied respectively with I, Q signals from input terminals 1A, 1B of mixer circuits 2A, 2B, the products are added by an adder 2D to obtain a quadrature modulated signal. The quadrature modulated signal is multiplied with a carrier wave from a local oscillator 2G by a mixer circuit 2E and the product is sent as a signal with a transmission frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device such as a mobile phone for transmitting and receiving using a digital modulation signal, and more particularly to a quadrature modulation system for transmitting or transmitting using a quadrature modulation system such as QPSK modulation. By a communication device.

[0002]

2. Description of the Related Art In the field of mobile phones, a method of transmitting and receiving by using a digital modulation signal has been developed and already put to practical use from the viewpoints of call quality, confidentiality, effective use of frequency and the like. In addition, cordless telephones will also be digitized in the future by using such technology. In Japan, the former uses PDC (Personal Digital Cellular) and the latter uses PDC.
HS (Personal Handyphone System) is used.

[0003] For example, in the case of the former, the standard is "Digital System Car Telephone System Standard RCR STD-27B" edited by Radio System Development Center, December 1992 pp. As described in 15-29, the transmission signal is a π / 4 shift QPSK modulation signal. As shown in Fig. 3.3-1 of the above standard, this is performed by quadrature-modulating a set of I and Q signals obtained by differentially encoding data with 2-bit data as a modulation symbol. It is generated.

FIG. 10 is a block diagram showing an example of such a conventional transmission / reception circuit. 1A and 1B are input terminals, 3 is a band limiting filter, and 4 is a high power amplifier (HP).
A) 5 is an antenna duplexer, 6 is an antenna, 7 is a low noise amplifier (LNA), 8 is a band limiting filter, 9 is a mixer circuit, 10 is a band limiting filter, 11 is a mixer circuit, and 12 is band limiting. Filter, 13 is an output terminal, 1
Reference numerals 4 and 15 are local VCOs (voltage controlled oscillators), 20 is a quadrature modulation circuit, 20A and 20B are mixer circuits, 20C is a 90-degree shifter, 20D is an adder, and 20E is a mixer circuit.

In the figure, differentially encoded I and Q signals are supplied from input terminals 1A and 1B to a quadrature modulation circuit 20, and quadrature modulation signals of a transmission frequency are obtained by carriers from local VCOs 14 and 15. To be The quadrature modulation signal is band-limited by the band-limiting filter 3 to remove unnecessary components (image components), amplified by the high power amplifier 4 until the power becomes necessary for transmission, and then passed through the antenna duplexer 5. It is supplied to the antenna 6 and transmitted.

Further, the quadrature modulation signal having a weak transmission frequency received by the antenna 6 is supplied to the low noise amplifier 7 via the antenna duplexer 5 and amplified to a level required for signal processing in the subsequent stage. This amplified received quadrature modulated signal is
After the unnecessary component outside the band is removed by the band limiting filter 8, it is supplied to the mixer circuit 9, multiplied by the carrier wave from the local VCO 14 to be converted into a quadrature modulated signal of the first intermediate frequency, and the band limiting filter. At 10, unnecessary components outside the band are removed. The quadrature modulation signal of the first intermediate frequency output from the band limiting filter 10 is the mixer circuit 1
1 and is multiplied by the carrier wave from the local VCO 15 to be converted into a second intermediate frequency quadrature modulation signal.
The quadrature modulated signal of the second intermediate frequency is supplied to the demodulator (not shown) from the output terminal 13 after the unnecessary component outside the band is removed by the band limiting filter 12, and is subjected to differential encoding I and Q. Demodulated into a signal.

Here, a portion surrounded by a double line, that is, a high power amplifier 4, a low noise amplifier 7, a mixer circuit 9 and 1
1, local VCO 14, 15 and quadrature modulation circuit 20
Is an independent active device (IC, module,
It is a single FET, etc.).

Here, in the quadrature modulation circuit 20, the carrier wave from the local VCO 15 is supplied to the 90-degree shifter, and the 90-degree phase is different from each other (that is, orthogonal).
Two carriers with a frequency equal to the intermediate frequency of are formed. One of these carrier waves is multiplied by the I signal from the input terminal 1A in the mixer circuit 20A to obtain the modulated I signal of the first intermediate frequency, and the other is mixed by the mixer circuit 20B in the input terminal 1A.
Modulation Q of the first intermediate frequency multiplied by the Q signal from B
The signal is obtained. These modulated I and Q signals are added to the adder circuit 20.
Addition is performed at D to obtain a quadrature modulation signal of the first intermediate frequency. This quadrature modulation signal is supplied to the mixer circuit 20E, multiplied by the carrier wave from the local VCO, and becomes a quadrature modulation signal up-converted to the transmission frequency. The band limiting filter 3 removes the unnecessary component generated in the mixer circuit 20E mixed in the quadrature modulation signal of the transmission frequency.

By the way, as the 90-degree shifter 20C used in the quadrature modulation circuit 20, conventionally, the following two types can be considered.

One is to use a Gilbert circuit to double the carrier wave from the local VCO 15 (this is basically a mixer circuit, and its two input signals can be the same carrier wave from the local VCO 15). , And a flip-flop triggered every rising edge of this doubled carrier and a flip-flop triggered every falling edge of this doubled carrier to obtain a carrier divided by two. The carrier waves have a phase difference of 90 degrees from each other.

The other one uses an RC type low-pass filter and a CR type high-pass filter whose time constants are equal to each other, and supplies a carrier wave from the local VCO 15 to these filters, and these filters pass each other. Carrier waves with different phases of 90 degrees are obtained.

[0012]

By the way, in the structure of the above-mentioned conventional example, there are the following problems especially when the above method is used as the quadrature modulation circuit 20.

First, in order to generate two carrier waves having a phase difference of 90 degrees from each other, the carrier wave from the local VCO 15 is first doubled and divided by two.
In the multiplied carrier wave, unless the generation of the second harmonic is suppressed and the duty is kept good, the above 2
The accuracy of the 90-degree phase difference between the two conveyances cannot be ensured, and the modulation accuracy is reduced.

By the way, a Gilbert circuit is usually used as the above-mentioned doubling means.
When two identical input signals are multiplied, there is a problem that even-order harmonics are likely to occur due to multiplication of the fundamental wave and the third harmonic. In order to reduce this, the level of the input carrier wave to the Gilbert circuit may be narrowed down, but in that case, the input carrier wave leaks to the output doubled signal due to the characteristic variations of the circuit elements. Therefore, the rising and falling edges of the doubled signal are affected by the influence, and the accuracy of the duty of the doubled signal which is also obtained is reduced.

In order to solve such a problem, it is necessary to further provide a bandpass filter so as to remove such an unnecessary wave component in the obtained doubled signal. Of course, if the IF frequency (transmission frequency depending on the configuration of the quadrature modulation circuit) changes depending on the system, the time constant of this BPF must be changed to match it.

Further, in the above method in which the carrier wave from the local VCO 15 is phase-shifted using the low-pass filter and the high-pass filter having the same time constant,
The time constant must be changed according to the IF frequency (or transmission frequency) of the applied system, and there is a problem that circuit components cannot be shared between different systems.

The object of the present invention is to eliminate such problems and
It is an object of the present invention to provide a quadrature modulation type communication device capable of ensuring a 90-degree phase difference between two carriers with high accuracy and obtaining good modulation accuracy, and enabling circuit components to be shared between different systems. .

[0018]

In order to achieve the above object, the present invention provides a quadrature modulation circuit for generating a transmission signal of a quadrature modulation signal, the frequency being twice the IF (intermediate) frequency of the quadrature modulation signal. Of the first carrier wave, a 90-degree shifter for dividing the first carrier wave into two to generate second and third carrier waves having a phase difference of 90 degrees, and the second carrier wave. And a first differentially encoded signal
, A second mixer circuit for multiplying the third carrier wave by the second differentially encoded signal, and the output signals of the first and second mixer circuits are added to obtain the quadrature of the intermediate frequency. And an adder for forming a modulated signal.

Further, the present invention further comprises a third aspect of up-converting the quadrature modulated signal of the intermediate frequency into a transmission frequency.
The mixer circuit of is provided in the quadrature modulation circuit.

Further, according to the present invention, the first carrier generated by the local oscillator is a signal having a frequency four times as high as the IF frequency, and the 90-degree phase shifter divides the first carrier by four to divide the second carrier into the second carrier. , The third carrier is generated.

Further, according to the present invention, the above-mentioned 90 is used as a frequency conversion carrier for converting the received signal in these receiving circuits into a signal of the second intermediate frequency by providing two receiving circuits for diversity reception. The second and third carriers from the frequency shifter are used.

[0022]

A local oscillating unit which oscillates a carrier having a frequency twice the IF frequency is used, and this is divided by a 90-degree shifter to have a phase difference of 90 degrees with respect to each other.
Since the carrier wave is generated, a doubler circuit such as a Gilbert circuit is unnecessary, and therefore, the second, third
The accuracy of the 90-degree phase difference of the carrier wave is improved, and the modulation accuracy is improved. Further, since it is not necessary to remove the unnecessary wave component of the carrier having a frequency twice the IF frequency by BPF or the like, the number of parts is reduced, and even if the system changes, there is no need to change it. Further, compared to the case where the 90-degree phase shifter is configured by using the RC-type LPF and the CR-type HPF, even if the system to which the 90-degree phase shifter is applied is changed, the system can be used as it is, and the trouble of changing the constant is unnecessary.

When the first carrier having a frequency four times the IF frequency is used, the 90-degree shifter triggers only on one of its rising edge and falling edge to divide by four, Since the second and third carriers having the intermediate frequency with the phase difference of 90 degrees are generated, the accuracy of the phase difference is further improved.

Furthermore, when diversity reception is carried out by using two systems of receiving circuits, the second and third carrier waves from the 90-degree shifter are converted into signals of the second intermediate frequency from the signals received by these receiving circuits. Since the carrier for frequency conversion is used as the carrier for the frequency conversion, the loads of the two carriers of the 90-degree shifter are completely the same, and the accuracy of the 90-degree phase difference is further improved and the modulation accuracy is further improved.

[0025]

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

FIG. 1 is a block diagram showing a first embodiment of a communication apparatus using a quadrature modulation system according to the present invention. 2 is a quadrature modulation circuit, 2A and 2B are mixer circuits, 2C is a 90-degree shifter, and 2D is a Adder, 2E is a mixer circuit, 2F, 2G
Is a local oscillator, 23 is a phase comparison circuit, and 23A is M ₁
Frequency divider, 23B is N ₁ frequency divider, 23C is a phase comparator, 2
3D is a loop filter, 24 is a phase comparison circuit, 24A is an M ₂ frequency divider, 24B is an N ₂ frequency divider, 24C is a phase comparator,
Reference numeral 24D is a loop filter, and 25 is a crystal oscillator. Parts corresponding to those in FIG.

In FIG. 10, this first embodiment is shown in FIG.
10 is different from the conventional example shown in FIG.
Instead of the O14 and 15 and the quadrature modulation circuit 20, one crystal oscillator 25, the phase comparison circuits 23 and 24, and the quadrature modulation circuit 2 are used, and two oscillators 2F and 2G are provided on the same device called the quadrature modulation circuit 2. It is a point.

The local oscillator 2F in the quadrature modulation circuit 2 and the phase comparison circuit 24, that is, the phase comparator 24 thereof.
C, the loop filter 24D and the N ₂ frequency divider 24B are P
LL (Phase Lock Loop) circuit, and
The local oscillator 2G and the phase comparison circuit 23 in the quadrature modulation circuit 2, that is, the phase comparator 23C, the loop filter 23D and the N ₁ frequency divider 23B form a PLL (phase locked loop) circuit, All the two PLL circuits may be provided on the same device. In this case, the two phase comparison circuits 23 and 24 are also integrated with the quadrature modulation circuit 2.

In addition to the quadrature modulation circuit 2, the two phase comparison circuits 23 and 24 may be integrated.

In short, in the present invention, only the local oscillator 2F of the two local oscillators 2F and 2G needs to be on the same device as the quadrature modulation circuit 2, and the object of the present invention can be achieved. Further, in the case of the local oscillator 2F which is configured to oscillate by feedback between the base and emitter of the transistor, for example, only the transistor itself may be on the same device as the quadrature modulation circuit 2.

Next, the operation of the first embodiment will be described.

The local oscillator 2F has a phase comparison circuit 24.
In addition, the local oscillator 2G constitutes a PLL circuit and a PLL circuit, respectively, and the crystal oscillator 2G
The carrier wave phase-locked with the clock of the reference frequency generated in 5 is oscillated and output. Here, the oscillation frequency of the local oscillator 2F is set to a frequency twice the first IF (intermediate) frequency, which is one of the features of this embodiment, and the output carrier of the local oscillator 2F is Since the 90-degree shifter 2C divides the frequency by two, the phases are 90 degrees relative to each other.
Carrier waves of different first IF frequencies are obtained. These carrier waves are supplied to the mixer circuits 2A and 2B and modulated by the I and Q signals. The carrier of the first IF frequency output from the 90-degree shifter 2C is also supplied as a carrier to the mixer circuit 11 on the receiving side.

Further, being outputted carrier N ₂ divided by N ₂ frequency divider 24B of the local oscillator 2F, the clock and phase comparison of the reference frequency of the crystal oscillator 25 which is M ₂ divided by M ₂ frequency divider 24A The phase comparison is performed by the device 24, and the error signal corresponding to the phase difference is supplied to the local oscillator 2F as an oscillation control signal via the loop filter 24D.

The frequency divider 24B may be supplied with a frequency-divided signal by 2 (for example, the output signal of the 90-degree phase shifter 2C) instead of the output carrier of the local oscillator 2F as shown in the figure. Good.

Here, as described above, the local oscillator 2
The fact that the oscillation frequency of F is selected to be twice the first IF frequency is also a feature of this embodiment. In the conventional example shown in FIG. 9, the quadrature modulation circuit 20 and the local VCO 1 are used.
5 and 5 are separate devices, and the local VCO 15
Since the carrier wave generated from is not only the 90 shifter 20C of the quadrature modulation circuit 20 but also the carrier wave of the mixer circuit 11 on the receiving side, the oscillation frequency of the local VCO 15 should be set to twice the first IF frequency. I can't.
This is because if the number is doubled, an external countdown circuit is required.

On the other hand, in the first embodiment, as shown in FIG.
As shown in, the local oscillator 2F is in the same device as the quadrature modulation circuit 2, so there is no problem even if the oscillation frequency is doubled.

In this way, by making the frequency of the output signal from the local oscillator 2F twice the first IF frequency, the 90-degree shifter 2C can operate by dividing this output signal by two. Good. Therefore, 90 degree shifter 2
As C, it is not necessary to adopt a configuration using a low-pass filter and a high-pass filter having the same time constant as in the above-mentioned conventional example, and it can be used as it is in a system having a different carrier frequency. Since there is no need to multiply by two, it is not necessary to use the Gilbert circuit as in the above-mentioned conventional example. Therefore, as described above, an error in the 90-degree phase difference between the two carriers due to the leakage of the even harmonics and the carrier. There is no problem such as occurrence of noise or a filter for removing unnecessary waves.

Further, since the 90-degree phase shifter 2C can be constituted by a flip-flop triggered at every rising edge of the output signal of the local oscillator 2F and a flip-flop triggered at every falling edge, the mixer circuit on the receiving side. The carrier required for 11 can also be obtained by this 90-degree shifter 2C, and there is no need for a countdown circuit required when the frequency of the output of the local VCO 15 in FIG. 9 is twice the first IF frequency. There are also advantages.

[0039] Further, a carrier wave output from the local oscillator 2G is N ₁ divided by N ₁ frequency divider 23B, clock and phase comparison from crystal oscillator 25 which is M ₁ divided by M ₁ frequency divider 23A The phase is compared by the device 23C. The phase error signal is processed by the loop filter 23D, and the local oscillator 2G is output by the output of the loop filter 23D.
The oscillation frequency of is controlled. The output signal of the local oscillator 2G is supplied to the mixer circuit 2E and is also supplied as a carrier wave to the mixer circuit 9 on the receiving side.

Here, the frequency relationship between each carrier and the clock will be described.

For example, in a system such as PHS in which the carrier frequency is the same during transmission and during reception (1895.150 to 1917.950 MHz, carrier interval 300 kHz), the oscillation frequency of either local oscillator 2G or 2F is the same as during transmission. There is a slight shift between when receiving (at the second IF frequency on the receiving side, for example, 10.8 MHz).

Generally, the local oscillator 2G having a higher oscillation frequency requires a smaller ratio of the shift amount to the local oscillator 2G. Therefore, it is better to shift the oscillation frequency of the local oscillator 2G. For example, an example in which the local oscillators 2F and 2G are phase-locked with respect to the crystal oscillator 25 that oscillates at 19.2 MHz is as follows.

That is, the local oscillator 2F is set to 458.5 MHz
(The carrier frequency of the quadrature modulation signal output from the quadrature modulation circuit 2 is 229.25 MHz), and this is divided into N ₂ frequency divider 2
The signal of frequency 100kHz divided by 4585 by 4B and the output clock of the crystal oscillator 25 are 192 by the M ₂ frequency divider 24A.
A phase comparator 24C compares the phase of the divided 100 kHz signal, the phase error signal is processed by the loop filter 24D, and the oscillation frequency of the local oscillator 2F is controlled by the output signal. Since the switching between transmission and reception and channel switching are not performed here, this oscillation frequency is constant.

On the other hand, the oscillation frequency of the local oscillator 2G is made different by 10.8 MHz during transmission and during reception. Assuming that the first IF frequency on the receiving side is 240.05 MHz, the oscillation frequency of the local oscillator 2G is 1665.9 to 168 during transmission.
8.7 MHz, 1655.1 to 1677.9 MHz for reception, and it must be locked every 300 kHz depending on the channel used.

Therefore, in the phase comparison circuit 23, M ₁ = 64
, The output clock of the crystal oscillator 25 is divided by 64 by the M ₁ divider 23A to obtain a signal of 300 kHz.
N _{1 is set} to 1/5553 to 5629 when transmitting and 1/5517 to 5593 when receiving, and the output carrier of the local oscillator 2G is 5553 to 56 when transmitting.
Divide by 29 and divide by 5517 to 5593 when receiving, N ₁
The frequency divider 23B switches the frequency division ratio to obtain a 300 kHz signal, and these two 300 kHz signals are used for the phase comparator 23C.
You can compare the phases with. Set the division ratio of the N ₁ divider 23B to 1
The oscillation frequency of the local oscillator 2G is 300 each time it is switched.
The frequency is shifted by kHz, so that {(1688.7MHz-166
5.9 MHz) ÷ 300 kHz} + 1 = 77 channels can be switched.

As described above, the carrier frequency of the first intermediate frequency signal output from the mixer circuit 9 on the receiving side (second I
The F frequency) is 240.05 MHz, and the frequency of the carrier wave supplied from the 90-degree shifter 2C to the mixer circuit 11 is 229.25 MHz as described above.
The carrier frequency of the second intermediate frequency signal output from 1 is
240.05-229.25 = 10.8MHz.

On the other hand, a 19.2 MHz crystal oscillator 25
When the output clock of is multiplied by 9/16, it becomes 19.2 × 9/16 = 10.8MHz, which is equal to the second IF frequency on the receiving side of 10.8MHz.

Therefore, the demodulator 26 demodulates the second intermediate frequency signal output from the band limiting filter 12 as shown in FIG. 2 showing the second embodiment of the communication apparatus using the orthogonal modulation method according to the present invention. If the conversion ratio output clock of the crystal oscillator 25 is K ₂ / K ₁ of the frequency converter (K ₂ = 1
In this case, the output of the frequency converter 26 can be used as a demodulation clock in the demodulation circuit 26 by converting the frequency to 9/16 times with 27 which becomes a K ₁ frequency divider.
The crystal oscillator unique to the demodulation circuit 26 is not necessary. The I and Q signals demodulated by this are output terminals 28.
Output from

In this way, all the clocks and carrier waves can be generated only by using one crystal oscillator 25 as a reference oscillator, and the number of parts of the device can be greatly reduced.

FIG. 3 is a block diagram showing a third embodiment of the communication apparatus using the quadrature modulation method according to the present invention.
Is a frequency-dividing circuit, and the parts corresponding to those in FIG.

In this embodiment, as shown in FIG. 3, the carrier wave of the mixer circuit 11 on the receiving side is obtained by dividing the output signal of the local oscillator 2F in the quadrature modulation circuit 2 by 2 by the frequency divider 2H. It is the one. The frequency divider 2H is provided in the same device as the quadrature modulation circuit 2. The output signal of the local oscillator 2F is supplied to the N2 frequency divider 24B of the phase comparison circuit 24 as in the case of FIGS.

In this embodiment, the same effect as that of the first embodiment shown in FIG. 1 can be obtained.

FIG. 4 is a block diagram showing a fourth embodiment of the communication apparatus using the orthogonal modulation method according to the present invention.
4E is a frequency dividing circuit, and the parts corresponding to those in FIG.

In this embodiment, as shown in FIG. 4, the phase comparison circuit 24 is provided with a frequency dividing circuit 24E, and the output signal of the local oscillator 2F is frequency divided by 2 by the frequency dividing circuit 24E to obtain N2.
It is supplied to the frequency divider, and the output signal of this frequency divider is used as the carrier wave of the mixer circuit 11 on the receiving side. The frequency dividing circuit 24H is provided in the same device as the phase comparison circuit 24.

Here, in order to make the frequencies of the two inputs of the phase comparator 24C equal to those of the embodiments shown in FIGS. 1 and 2, the frequency division ratio N ₂ 'of the frequency divider 24B is set to that shown in FIG. , it may be equal to 1/2 of the frequency dividing ratio N ₂ of N ₂ frequency divider 24B in FIG. 2, when the dividing ratio N ₂ is an odd number, 4
The frequency division ratio N ₂ ′ of the frequency divider 24B is equal to the frequency division ratio N ₂ and the frequency division ratio M ₂ ′ of the frequency divider 24A is M ₂ frequency divider 24A in FIGS. of equal to twice the frequency division ratio M _2, FIG. 1 the frequency of the input signal to the phase comparator 24C, may be 1/2 of the case of FIG.

Also in this embodiment, the same effect as that of the first embodiment shown in FIG. 1 can be obtained.

FIG. 5 is a block diagram showing a fifth embodiment of the communication apparatus using the quadrature modulation method according to the present invention.
Is a local oscillator, and 2J is a frequency divider by 2. The parts corresponding to those in FIG.

In the figure, the local oscillator 2I has a first
Oscillates at a frequency four times as high as the IF frequency, and the output signal is frequency-divided by the frequency divider 2J into a signal having a frequency twice the first IF frequency. The 90-degree phase shifter 2C and the phase comparison circuit 24 of the N2 frequency divider 24B. The other configuration is the same as that of the embodiment shown in FIG.

The frequency divider 2J is triggered by a rising edge or a falling edge of the output signal of the local oscillator 2I to generate a signal having a frequency twice that of the first IF frequency divided by two. Therefore, even if the duty of the output signal of the local oscillator 2I is not good, the 90-degree shifter 2
The C input signal has no even harmonics, and the modulation accuracy is further improved.

FIG. 6 is a block diagram showing a sixth embodiment of a quadrature modulation type communication apparatus according to the present invention.
Is a local oscillator, and 2L is a 90-degree shifter. The parts corresponding to those in FIG.

In the figure, the local oscillator 2K has a first
It outputs a signal with a frequency four times the IF frequency of
0 ° shifter 2L and N ₂ frequency divider 24B of the phase comparison circuit 24
Is supplied to. Other than this, it is the same as the embodiment shown in FIG.

[0062] Here, 90 degree phase shifter 2L is the phase shifter of the fourth frequency type, also the frequency division ratio N ₂ of N ₂ frequency divider 24B also, N ₂ in the embodiment shown in FIG. 1, etc. Frequency divider 24B
The frequency division ratio N ₂ is twice.

FIG. 7 is a block diagram showing a specific example of the 90-degree shifter 2L in FIG. 6, in which 2L ₁ is an input terminal,
2L ₂ and 2L ₃ are D-type flip-flops (D-FF),
2L ₄ and 2L ₅ are output terminals.

In the figure, a signal having a frequency four times the first IF frequency output from the local oscillator 2K in FIG. 6 is supplied as a clock P _i from the input terminal 2L ₁ , and the D-FF 2L ₂ , 2L ₃ is simultaneously triggered on the rising or falling edge of this clock P _i . Further, as the D (data) input D1 of the D-FF2L ₂ ,
An output (hereinafter referred to as a Q-inverted output Q2) having an inversion relation with the Q output Q2 of the D-FF2L ₃ is supplied to the D-FF2L.
The _third D input D2, Q output Q1 of the D-FF2L ₂ is supplied. Then, Q output Q1 of the D-FF2L ₂ is output from the output terminal 2L ₄ as a carrier wave P _O1, D-FF
2L ₃ Q inversion output Q2 is output terminal 2 as carrier wave P _O2
It is output from L ₅ .

Next, the operation of this specific example will be described with reference to FIG. 8 showing the timing relationship of the signals of the respective parts of FIG.

[0066] Now, D-FF2L _2, 2L ₃ is assumed to be triggered on the rising edge of the input clock P _i, the D-FF2L ₂ on the rising edge at time t ₁ of the input clock D
A D input D2 of the input D1 and D-FF2L ₃ are both "H" and (high level). Thus, Q-inverting output Q2 of the Q output Q1 and D-FF2L ₃ of D-FF2L ₂ are both "H".

At the rising edge of the input clock P _i at time t ₁ , the D-FF 2L ₂ samples and holds the "H" D input D1, and the D-FF 2L ₃ also samples and holds the "H" D input D2. The Q output Q1 of D-FF2L ₂ is
Because it is the time to "H", it is maintained as it "H", Q inverting output Q2 of the D-FF2L _3, since it is the time to "H", inverted to "L" (low level).
Thus, from time t ₁ , the D input D of D-FF2L ₂
1 is "L", D input D2 of the D-FF2L ₃ is "H".

Further, at time t ₁ , the carrier wave P _O1 output from the output terminal 2L ₄ remains “H”, and the output terminal 2
The carrier wave P _O2 output from L ₅ is level-inverted from “H” to “L”.

At the next rising edge (time t ₂ ) of the input clock P _i , the D-FF2L ₂ samples and holds the D input D1 of "L", and the Q output Q1 thereof changes from "H" to "L". level inverted, D input D2 of the "H" in D-FF2L ₃ is a sample and hold, the Q inverting output Q2
Is held at "L" as it is. As a result, the time t ₂
From the D-FF2L ₂ D input D1 and D-FF2L ₃
D input D2 of is "L".

At time t ₂ , the carrier wave P _O1 output from the output terminal 2L ₄ is level-inverted from “H” to “L”, and the carrier wave P _O2 output from the output terminal 2L ₅ is “L”.
It remains.

At the next rising edge (time t ₃ ) of the input clock P _i , the D-FF 2L ₂ outputs the "L" D input D.
1 is a sample and hold, its Q output Q1 is held as it is "L", D-FF2L D input D2 of the "L" ₃ is a sample and hold, the Q inverting output Q2 changes from "L" to "H Invert the level to "". Thus, from the time t _3, D input D1 of D-FF2L ₂ is "H", D-
The D input D2 of FF2L ₃ is “L”.

At time t ₃ , the carrier wave P _O1 output from the output terminal 2L ₄ remains “L”, and the output terminal 2
The carrier wave P _O2 output from L ₅ is level-inverted from “L” to “H”.

At the next rising edge of the input clock P _i (time t ₄ ), the D-FF 2L ₂ outputs "H" at the D input D.
1 is sampled and held, and its Q output Q1 is "L"
Level inverted from "H", D input D2 of the "L" in D-FF2L ₃ is a sample and hold, the Q inverting output Q2 is held as it is "H". Thus, from the time t _4, D-FF2L ₂ of D inputs D1 and D-FF2L
The D input D2 of ₃ is "H".

At time t ₄ , the carrier wave P _O1 output from the output terminal 2L ₄ is level-inverted from “L” to “H”, and the carrier wave P _O2 output from the output terminal 2L ₅ is “H”.
It remains.

At the next rising edge (time t ₅ ) of the input clock P _i , the D inputs D1 and D- of the D-FF2L ₂ are sent.
D input D2 of FF2L ₃ is "H", therefore, D-FF2
The Q output Q1 of L ₂ and the Q inverted output Q2 of D-FF2L ₃ are “H”, which is the same as the state at time t ₁ , and the input clock P _{i from} time t _{1 to} t _{4 will be described} below. The operation of 4 cycles is repeated.

Therefore, as is apparent from FIG. 8, the carrier waves P _O1 and P _O2 output from the output terminals 2L ₄ and 2L ₅ are signals having a quarter period of the input clock P _i (thus, the first IF).
Frequency signal) and the carrier wave P _O1 is a carrier wave P _O2
Therefore, the input clock P _i is delayed by one cycle (that is, 90 degrees). Then, if the frequency of the input clock P _i is stable, regardless of the accuracy of the duty,
The duty of the carrier waves P _O1 and P _O2 and the phase difference of 90 degrees between them are accurately maintained.

In the fifth embodiment shown in FIG. 5, the output signal of the frequency divider 2J is supplied only to the phase comparison circuit 24 (in this case, the frequency divider 2J is a quadrature modulation circuit). 2 may be provided in the same device, or may be provided in the same device as the phase comparison circuit 24),
The 90-degree shifter 2C may be configured as shown in FIG. 7, and an output signal having a frequency four times the first IF frequency of the local oscillator 2I may be directly supplied to the 90-degree shifter 2C.

Heretofore, as a quadrature modulation method, an IF modulation method has been used in which modulation is performed once at an IF frequency and then up-converted to a transmission frequency band by the mixer circuit 2E. In addition, there is a direct modulation method in which a carrier wave in a transmission frequency band is generated and quadrature modulation is performed using this. As in the embodiment shown in FIGS. 5 and 6, the local oscillator 2
When I and 2K are oscillated at a frequency four times as high as the IF frequency, in the PHS, the direct modulation method has an extremely high frequency of 7.6 GHz, which is not practical. However, the IF modulation method has a value of 960 MHz, which is a sufficient value. That is,
In particular, in the embodiments shown in FIGS. 5 and 6, it is preferable to implement it in combination with the IF modulation method.

Also in the embodiments shown in FIGS. 3 to 6 described above, the demodulation clock can be obtained from the clock output from the crystal oscillator 25, as shown in FIG.

FIG. 9 is a block diagram showing a seventh embodiment of a quadrature modulation communication device according to the present invention.
Is an antenna, 17 is a low noise amplifier, 18, 19 and 21 are band-limiting filters, 22 is an output terminal, and 29 and 30 are mixer circuits. The parts corresponding to those in FIG. Is omitted.

In this figure, this embodiment differs from the first embodiment shown in FIG. 1 in that the antenna 16, low noise amplifier 17,
A receiving system including a band limiting filter 18, a mixer circuit 29, a band limiting filter 19, a mixer circuit 30 and a band limiting filter 21 is added.

The signal received by the antenna 16 is amplified by the low noise amplifier 17, the unnecessary components outside the required band are removed by the band limiting filter 18, and the signal is supplied to the mixer circuit 29 to be supplied to the quadrature modulation circuit 2. It is multiplied by the carrier wave from the local oscillator 2G and converted into a signal of the first IF frequency. The signal of the first IF frequency, after the unnecessary component is removed by the band limiting filter 19, is supplied to the mixer circuit 30 and is multiplied by the carrier wave from the 90-degree shifter 2C of the quadrature modulation circuit 2 to obtain the second IF signal. Converted to a frequency signal. The signal of the second IF frequency is supplied to the demodulator (not shown) from the output terminal 22 after the unnecessary component is removed by the band limiting filter 21.

Here, the mixer circuits 9, 11, 29, 30
Are collectively described as one device, but this is not necessarily an essential condition of this embodiment, and these may be devices different from each other. Alternatively, these mixer circuits 9, 11, 29 and 30 may be combined in the same device as the quadrature modulation circuit 2.

Further, the reason why two receiving systems are provided as described above is to perform known diversity reception.
One of the outputs from the output terminals 13 and 22 having a good sound quality is always selected. In particular, PDC and the like often take this configuration.

The mixer circuits 9 and 29 include the quadrature modulation circuit 2
The carrier wave output from the local oscillator 2G is supplied. In addition, the mixer circuit 11 includes 90% of the quadrature modulation circuit 2.
One carrier of the first IF frequency output from the frequency shifter 2C is supplied to the mixer circuit 30.
The other carrier having a different phase is supplied. By doing so, the load of the 90-degree shifter 2C becomes completely symmetrical between the two outputs having different 90-degree phases, and the 90-degree phase difference error can be completely eliminated.

Note that, also in the embodiment shown in FIGS. 2 to 6, as in the seventh embodiment, two receiving systems can be provided so as to have the same configuration. Even in these cases, there is no factor that causes a 90-degree phase difference error between the two output carriers of the 90-degree shifter from the clock input section to the load of the two outputs.

[0087]

As described above, according to the present invention,
A 90-degree phase difference between two carriers for orthogonally modulating an information signal can be secured with high accuracy, good modulation accuracy can be obtained, and circuit components can be shared between different systems. The number of parts such as filters can be reduced. Furthermore, even if diversity reception is performed as necessary, the accuracy of the 90-degree phase difference between the two carriers can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 6 is a block diagram showing a sixth embodiment of the communication apparatus using the orthogonal modulation method according to the present invention.

FIG. 7 is a block diagram showing a specific example of the 90-degree shifter in FIG.

8 is a timing chart showing the operation of the specific example shown in FIG.

FIG. 9 is a block diagram showing a seventh embodiment of a communication device using a quadrature modulation method according to the present invention.

FIG. 10 is a block diagram showing an example of a communication device using a conventional quadrature modulation method.

[Explanation of symbols]

 1A, 1B I, Q signal input terminal 2 Quadrature modulation circuit 2A, 2B Mixer circuit 2C, 2L 90 degree shifter 2D Adder 2E Mixer circuit 2F, 2G, 2K Local oscillator 2H, 2J 2 Divider 3 Band limiting filter 4 high power amplifier 5 antenna duplexer 6,16 antenna 7,17 low noise amplifier 8,18 band limiting filter 9,11,29,30 mixer circuit 10,19 band limiting filter 12,21 band limiting filter 13, 22 output terminal 23, 24 phase comparison circuit 23A, 23B, 24A, 24B frequency divider 23C, 24C phase comparator 23D, 24D loop filter 24E 2 frequency divider 25 crystal oscillator 26 demodulation circuit 27 frequency conversion circuit

Claims (16)

[Claims] 1. A communication device comprising a quadrature modulation circuit for transmitting a digitally modulated transmission signal and generating a quadrature modulation signal as the transmission signal in a transmission circuit, wherein the quadrature modulation circuit is the quadrature modulation signal. Local oscillator that oscillates a first carrier having a frequency twice as high as the carrier frequency, and frequency-divides the first carrier by two, and the second and second frequencies are equal to the carrier frequency and have a phase difference of 90 degrees from each other. 90 degree shifter for generating a third carrier wave, a first mixer circuit for multiplying the second carrier wave by the first differentially encoded signal, a third carrier wave and a second differentially encoded signal And a second mixer circuit that multiplies by and an adder that adds the output signals of the first and second mixer circuits to generate the quadrature modulation signal. . 2. The frequency of the first carrier is twice the intermediate frequency of the quadrature modulated signal, and the quadrature modulated signal of the intermediate frequency output from the adder is the transmission frequency of the quadrature modulated signal. A communication device using a quadrature modulation method, wherein a third mixer circuit for up-converting the transmission signal is provided. 3. A communication device comprising a quadrature modulation circuit for transmitting and receiving a transmission signal by digital modulation and generating a quadrature modulation signal which becomes the transmission signal in a transmission circuit, wherein the quadrature modulation circuit is the quadrature modulation signal. A local oscillating unit that oscillates a first carrier wave having a frequency twice as high as the intermediate frequency, and frequency-divides the first carrier by two, and the frequency is equal to the intermediate frequency and the second and second phases have a phase difference of 90 degrees from each other. 90 degree shifter for generating a third carrier wave, a first mixer circuit for multiplying the second carrier wave by the first differentially encoded signal, a third carrier wave and a second differentially encoded signal And a second mixer circuit that multiplies by and an adder that adds the output signals of the first and second mixer circuits to generate the quadrature modulated signal of the intermediate frequency, and is generated by the 90-degree shifter. One of the second and third carrier waves The communication apparatus according to an orthogonal modulation scheme, characterized in that a frequency conversion carrier for converting the received signal of the receiving circuit in the second intermediate frequency signal. 4. A communication device comprising a quadrature modulation circuit for transmitting and receiving a transmission signal by digital modulation and generating a quadrature modulation signal to be the transmission signal in the transmission circuit, wherein the quadrature modulation circuit is the quadrature modulation signal. A local oscillating unit that oscillates a first carrier wave having a frequency twice as high as the intermediate frequency, and frequency-divides the first carrier by two, and the frequency is equal to the intermediate frequency and the second and second phases have a phase difference of 90 degrees from each other. 90 degree shifter for generating a third carrier wave, a first mixer circuit for multiplying the second carrier wave by the first differentially encoded signal, a third carrier wave and a second differentially encoded signal And a second mixer circuit that multiplies the first and second mixer circuits, and an adder that adds the output signals of the first and second mixer circuits to generate the quadrature-modulated signal of the intermediate frequency. Divide the frequency and divide the received signal in the receiving circuit to the second intermediate frequency. Communication device according to orthogonal modulation scheme, characterized in that a frequency conversion carrier for converting the signal. 5. The quadrature according to claim 3, further comprising a third mixer circuit that up-converts the quadrature modulation signal of the intermediate frequency output from the adder into the transmission signal of a transmission frequency. Communication device by modulation method. 6. A communication device comprising a quadrature modulation circuit for transmitting and receiving a transmission signal by digital modulation and generating a quadrature modulation signal to be the transmission signal in a transmission circuit, wherein the quadrature modulation circuit is the quadrature modulation signal. Local oscillator that oscillates a first carrier wave having a frequency four times the intermediate frequency, and a frequency divider that divides the first carrier wave by two to obtain a second carrier wave having a frequency twice the intermediate frequency. And a 90-degree shifter that divides the second carrier by two to generate third and fourth carriers whose frequencies are equal to the intermediate frequency and have a phase difference of 90 degrees from each other, and the third carrier and the first carrier. And a second mixer circuit for multiplying the fourth carrier by the second differential encoding; and a first mixer circuit for multiplying the fourth carrier by the second differential encoding, Addition for adding output signals to generate the quadrature modulated signal at the intermediate frequency Communication device according to orthogonal modulation scheme, characterized in that it comprises and. 7. A communication device comprising a quadrature modulation circuit for transmitting or receiving a transmission signal by digital modulation and generating a quadrature modulation signal to be the transmission signal in a transmission circuit, wherein the quadrature modulation circuit is the quadrature modulation circuit. A local oscillator that oscillates a first carrier wave having a frequency four times the intermediate frequency of the modulation signal, and the first carrier wave triggered by only one of a rising edge and a falling edge of the first carrier wave. Divide by 4
A 90-degree shifter for generating second and third carriers having a frequency equal to the intermediate frequency and having a phase of 90 degrees with each other, and a first mixer circuit for multiplying the second carrier by the first differential encoding. And a second mixer circuit for multiplying the third carrier wave by the second differential encoding, and output signals of the first and second mixer circuits are added, and the quadrature modulation signal of the intermediate frequency is added. And an adder for generating the quadrature modulation method. 8. The 90 degree shifter according to claim 6, further comprising a third mixer circuit for up-converting the quadrature modulation signal of the intermediate frequency output from the adder into the transmission signal of a transmission frequency. Orthogonal modulation, characterized in that one of the second and third carrier waves generated in step 1 is used as a frequency conversion carrier wave for converting a signal received by a receiving circuit into a signal of a second intermediate frequency. Communication device by method. 9. A quadrature modulation circuit for transmitting and receiving a digitally modulated transmission signal and generating a quadrature modulation signal to be the transmission signal in the transmission circuit, and performing diversity reception by the first and second reception circuits. In the communication device, the quadrature modulation circuit oscillates a first carrier wave having a frequency twice as high as an intermediate frequency of the quadrature modulated signal, and divides the first carrier wave by 2 to divide the frequency into the intermediate frequency band. A 90-degree shifter for generating second and third carriers that are equal in frequency and have a 90-degree phase difference from each other; a first mixer circuit for multiplying the second carrier by the first differential encoding; A second mixer circuit for multiplying the third carrier wave by the second differential encoding and output signals of the first and second mixer circuits are added to generate the quadrature modulated signal of the intermediate frequency. An adder and the second and third Respectively transmitting, first, the communication device by the orthogonal modulation scheme, characterized in that the second frequency conversion carrier for converting the received signal into a signal of a second intermediate frequency in the receiving circuit. 10. A quadrature modulation circuit for transmitting and receiving a digitally modulated transmission signal and generating a quadrature modulation signal to be the transmission signal in the transmission circuit, and diversity reception is performed by the first and second reception circuits. In the communication device, the quadrature modulation circuit includes a local oscillating unit that oscillates a first carrier wave having a frequency four times the intermediate frequency of the quadrature modulated signal, and divides the first carrier wave by 2 to generate the intermediate frequency signal. A frequency divider having a doubled frequency as a second carrier and a frequency divider that divides the second carrier by two and that has a frequency equal to the intermediate frequency and a phase difference of 90 degrees from each other. A 90-degree shifter for generation, a first mixer circuit for multiplying the third carrier by the first differential encoding, and a second mixer circuit for multiplying the fourth carrier by the second differential encoding. Of the mixer circuit and the first and second mixer circuits And an adder for generating the quadrature-modulated signal of the intermediate frequency, the third and fourth carrier waves being respectively received by the first and second receiving circuits. A quadrature modulation communication device, which uses a carrier wave for frequency conversion for converting into a signal of an intermediate frequency of 2. 11. A quadrature modulation circuit for transmitting and receiving a digital modulation transmission signal and generating a quadrature modulation signal to be the transmission signal in the transmission circuit, and diversity reception is performed by the first and second reception circuits. In the communication device, the quadrature modulation circuit includes a local oscillator that oscillates a first carrier wave having a frequency four times the intermediate frequency of the quadrature modulated signal, and one of a rising edge and a falling edge of the first carrier wave. Triggered on one side to divide the first carrier by four,
A 90-degree shifter for generating a second carrier and a third carrier having a frequency equal to the number of the intermediate weeks and having a phase difference of 90 degrees from each other, and a first multiplier for multiplying the second carrier by the first differential encoding. Mixer circuit, a second mixer circuit for multiplying the third carrier by the second differential encoding, output signals of the first and second mixer circuits are added, and An adder for generating a quadrature modulated signal, for converting the reception signals of the second and third carrier waves into the second intermediate frequency signal, respectively. A communication device using a quadrature modulation method, which uses a carrier for frequency conversion. 12. The third mixer circuit according to claim 9, further comprising a third mixer circuit that up-converts the quadrature modulation signal of the intermediate frequency output from the adder into the transmission signal of a transmission frequency. Communication device using a quadrature modulation method. 13. The single reference oscillator according to claim 2, means for synchronously controlling the local oscillator with the output of the reference oscillator, and the orthogonal modulation signal of the intermediate frequency in the third mixer circuit. A communication device using a quadrature modulation method, comprising: a transmission oscillating unit for generating a carrier wave for up-converting the signal; and means for synchronously controlling the transmission oscillating unit with the output of the reference oscillator. 14. Any one of claims 3 to 5 and 8 to 12.
A single reference oscillator, means for synchronously controlling the local oscillator with the output of the reference oscillator, and means for generating a demodulation clock of a demodulation circuit in the receiving circuit from the output of the reference oscillator And a communication device using a quadrature modulation method. 15. The single reference oscillator according to claim 12, means for synchronously controlling the local oscillator with the output of the reference oscillator, and the demodulation circuit of the receiving circuit from the output of the reference oscillator. Means for generating a demodulation clock, a transmission oscillating section for generating a carrier wave for up-converting the quadrature modulated signal of the intermediate frequency in the third mixer circuit, and synchronous control of the transmission oscillating section with the output of the reference oscillator. And a means for performing the quadrature modulation method communication device. 16. The switching oscillator according to claim 13, wherein the oscillation frequency of the transmission oscillator is switched.
A communication device using a quadrature modulation method, which switches frequency channels.