JP2002198859A - Transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and low-power consumption transmitter-receiver. SOLUTION: A first image rejection mixer 1 mixes a received signal with a first local signal having a frequency lower by a half the channel frequency spacing than a desired channel frequency. A second image rejection mixer 2 mixes a reception signal with a second local signal having the same frequency as the channel frequency spacing with an intermediate frequency signal, and outputs a resultant signal to a demodulator circuit. For transmission, the frequency of a first local signal source is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transceiver mainly used for a wireless communication device such as a cordless remote controller, a pager, a cordless telephone, and a portable telephone.

[0002]

2. Description of the Related Art A conventional transceiver will be described with reference to the drawings. FIG. 9 is a block diagram showing a configuration of a conventional transceiver.

In FIG. 9, reference numeral 3 denotes a first local signal source;
Is a second local signal source, 6 is a transmission amplifier, 7 is an antenna,
8 is an antenna switch, 9 is a receiving amplifier, 10 is a demodulated data output terminal, 16 is a high frequency filter, 24 is a mixer,
51 is a first mixer, 52 is a second mixer, 53 is an intermediate frequency filter, and 54 is a channel selection filter.
The receiving system of the transceiver in FIG. 8 has a double superheterodyne system.

First, the receiving operation will be described. The received signal input to the antenna is input to the high frequency filter 16 to remove unnecessary frequency components. Here, the first mixer 5
The image frequency component at the time of frequency conversion by 1 is removed. The output of the high frequency filter 16 is amplified by the receiving amplifier 9. The output of the receiving amplifier 9 and the output of the first local signal source 3 are mixed by a first mixer 51 and converted into a first intermediate frequency signal. From the first intermediate frequency signal, an image frequency component at the time of mixing in the second mixer 52 is removed by the intermediate frequency filter 53. The output of the intermediate frequency filter 53 and the output of the second local signal source 4 are mixed by the second mixer 52 and converted into a second intermediate frequency signal. The second intermediate frequency signal is input to the channel selection filter 54, and unnecessary components other than the reception channel component are removed. Here, the channel selection filter 54 is a g-channel filter configured using a passive element such as a ceramic filter or a crystal filter or an active element such as a transistor.
An mc filter or the like is used. The output of the channel selection filter 54 is input to the demodulation circuit 5, and the demodulation output is output from the demodulation data output terminal 10.

Next, the transmission operation will be described. The first local signal source 3 is modulated. Here, a binary FSK signal is output from the first first local signal source 3 and amplified by the transmission amplifier 6. The output of the transmission amplifier 6 is radiated from the antenna 7 via the antenna switch 8.

[0006]

However, the conventional transceiver has a problem in miniaturization and power saving.
That is, it is difficult to reduce the size of a passive element filter such as a ceramic filter or a quartz crystal filter because integration is difficult. Further, when a g-mc filter or the like is configured using active elements, there is a problem that current consumption increases in order to realize a filter characteristic that is steep and has a large amount of attenuation. Further, even if the number of elements is increased and integrated into a semiconductor IC, the chip size is increased and the cost is increased.

In addition, it is necessary to greatly change the frequency of the first local signal source between reception and transmission, and it has been difficult to obtain the frequency required for reception and transmission with one local oscillator.

An object of the present invention is to provide a small-sized and low-power-consuming transceiver by solving the above-mentioned conventional problems.

[0009]

In order to solve the above-mentioned conventional problems, a transceiver according to the present invention comprises first and second local signal sources, first and second image rejection mixers, and a demodulator. And a transmission amplifier, wherein at the time of reception, the first local signal source is set to a frequency lower or higher by a half of a channel frequency interval than a desired channel frequency of a reception signal, and the first image rejection mixer is provided. Receiving the output of the first local signal source and the output of the first local signal source, and suppressing the lower or higher frequency component of the received signal component than the first local signal source frequency, and receiving the first local signal of the received signal. A frequency component higher or lower than the signal source frequency is converted into a first intermediate frequency signal and output, and the second local signal source outputs a signal having the same frequency as the channel frequency interval. And inputting the first intermediate frequency signal and the output of the second local signal source to a second image rejection mixer, wherein the first intermediate frequency signal is higher than the second local signal source frequency in the first intermediate frequency signal A frequency component is suppressed, and a frequency component of the first intermediate frequency signal lower than the second local signal source frequency is converted into a second intermediate frequency signal, and the second intermediate frequency signal is input to the demodulation circuit. During transmission, the first local signal source is set to a transmission channel frequency, and the output of the first local signal source is amplified by the transmission amplifier.

As a result, the circuit scale can be greatly reduced, and the current consumption can be reduced. Also, semiconductor IC
In this case, the chip size can be reduced, so that cost reduction can be realized. In addition, since the frequency change of the first local signal source is small, it can be easily realized with one local signal source.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 comprises first and second local signal sources, first and second image rejection mixers, a demodulation circuit, and a transmission amplifier.
At the time of reception, the first local signal source is set to a frequency which is lower or higher by a half of a channel frequency interval than a desired channel frequency of the received signal, and the first image rejection mixer supplies the received signal and the first Input of the output of the local signal source, and suppressing the lower or higher frequency component of the received signal component than the first local signal source frequency, and adjusting the frequency of the received signal higher or lower than the first local signal source frequency. The second local signal source outputs a signal having the same frequency as the channel frequency interval, and outputs the first intermediate frequency signal to a second image rejection mixer. Inputting a signal and an output of the second local signal source, and suppressing a frequency component higher than the second local signal source frequency in the first intermediate frequency signal. Converting a frequency component of the first intermediate frequency signal that is lower than the second local signal source frequency into a second intermediate frequency signal, inputting the second intermediate frequency signal to the demodulation circuit, and performing demodulation; During transmission, the first local signal source is set to the transmission channel frequency and the first
A transmitter for amplifying the output of the local signal source by the transmission amplifier. A two-stage image rejection mixer realizes a channel selection filter by suppressing the signal components on the low frequency side and the high frequency side of the desired channel frequency, thereby significantly reducing the circuit scale. And current consumption can be reduced. In addition, when a semiconductor IC is used, the chip size can be reduced, so that cost reduction can be realized. Further, since the frequency of the first local signal source hardly changes during reception and transmission, the local signal source can be easily realized.

According to a second aspect of the present invention, the first local signal source comprises a PLL frequency synthesizer having a reference signal source and a voltage controlled oscillator, and the oscillation load capacitance of the reference signal source is reduced at the time of transmission and reception. A transceiver that varies the output frequency of said first local signal source by approximately one-half of the channel frequency interval by varying. Then, since an operation of changing the frequency by half of the channel frequency interval between reception and transmission can be realized by a simple circuit, a transceiver can be formed at a small size and at low cost.

According to a third aspect of the present invention, the first local signal source includes a reference signal source, a voltage controlled oscillator, and a frequency divider.
A transceiver comprising an LL frequency synthesizer, wherein the frequency divider of the frequency divider takes a fractional value to change the output frequency of the first local signal source by approximately one half of the channel frequency interval. Since the frequency division number of the frequency divider is a fraction and the frequency of the first local signal source can be set finely, a frequency change of half the channel frequency interval can be easily realized, and the circuit scale can be reduced. .

According to a fourth aspect of the present invention, there is provided the first and second local signal sources, the first, second and third image rejection mixers, a demodulation circuit, and a transmission amplifier. The first local signal source is set to a frequency lower or higher by a half of the channel frequency interval than the desired channel frequency of the received signal, and the first image rejection mixer supplies the received signal and the first local signal to the first image rejection mixer. The output of a source is input, and a frequency component lower or higher than the first local signal source frequency in the received signal component is suppressed, and a frequency component higher or lower than the first local signal source frequency in the received signal is converted to a second component. And the second local signal source outputs a signal having the same frequency as the channel frequency interval, and outputs a second image rejection signal. A first intermediate frequency signal and an output of the second local signal source are input to a mixer, and a frequency component higher than the second local signal source frequency in the first intermediate frequency signal is suppressed to suppress the first intermediate frequency signal. In the intermediate frequency signal, a frequency component lower than the second local signal source frequency is converted into a second intermediate frequency signal, and the second intermediate frequency signal is input to the demodulation circuit to perform demodulation. The first local signal source is set to a frequency lower or higher by a half of a channel frequency interval than a transmission channel frequency, and the second local signal source outputs a signal having a frequency of a half of the channel frequency interval. And outputs the outputs of the first and second local signal sources to the third image rejection mixer, and outputs a frequency component or a sum frequency difference between the first and second local signal source frequencies. A transmitter that attenuates the output and outputs a sum frequency component or a difference frequency component of the first and second local signal source frequencies, and amplifies the output of the third image rejection mixer with the transmission amplifier. . Since it is not necessary to change the frequency of the first local signal source for reception and transmission, and it is not necessary to change the frequency by half of the channel frequency interval, the configuration of the first local signal source can be simplified.

According to a fifth aspect of the present invention, there are provided first, second and third local signal sources, first, second and third image rejection mixers, a demodulation circuit, and a transmission amplifier. The first local signal source is set to a frequency lower or higher by a half of a channel frequency interval than a reception channel frequency of a reception signal, and reception is performed by the first image rejection mixer. Input of the output of the local signal source, and suppressing the lower or higher frequency component of the received signal component than the first local signal source frequency, and adjusting the frequency of the received signal higher or lower than the first local signal source frequency. The second local signal source outputs a signal having the same frequency as the channel frequency interval, and outputs a second image rejection signal. The first intermediate frequency signal and the output of the second local signal source are input to a mixer, and a frequency component of the first intermediate frequency signal that is higher than the second local signal source frequency is suppressed. In the intermediate frequency signal, a frequency component lower than the second local signal source frequency is converted into a second intermediate frequency signal, and the second intermediate frequency signal is input to the demodulation circuit to perform demodulation. The third
Outputs a signal having a frequency obtained by adding or subtracting a half of the channel frequency interval to or from the frequency of the difference between the reception channel frequency and the transmission channel frequency, the third image rejection mixer And outputs the first and third local signal sources, attenuates the frequency component of the difference between the first and third local signal source frequencies or the sum frequency component, and attenuates the first and third local signal sources. Output the frequency component of the sum of the frequencies or the frequency component of the difference,
A transmitter / receiver that amplifies an output of the third image rejection mixer with the transmission amplifier. And there is no need to change the frequency of the first local signal source for reception and transmission,
Since the third local signal source is provided for transmission, the reception operation and the transmission operation can be performed simultaneously.

According to a sixth aspect of the present invention, a pre-mixer for converting a received signal into a pre-frequency signal having a frequency lower than the frequency of the received signal is provided before the first image rejection mixer. Is a transceiver for inputting the preceding frequency signal to the first image rejection mixer in place of the above. Since the received signal is previously converted to a low frequency by the pre-mixer provided in the preceding stage of the receiving circuit, the accuracy of the image rejection mixer is easily obtained, and the attenuation as the channel selection filter is easily increased. Further, the reception current can be reduced.

According to a seventh aspect of the present invention, the first local signal source comprises a PLL synthesizer having a crystal oscillator and a voltage controlled oscillator, and the frequency of the output of the crystal oscillator is divided to provide a second local signal source. A transceiver that obtains the frequency. Since the second local signal source frequency is obtained by dividing the frequency of the crystal oscillator, which is a component of the first local signal source, the circuit scale can be reduced, and miniaturization and cost reduction can be achieved.

In a preferred embodiment of the present invention, the first local signal source comprises a PLL synthesizer having a crystal oscillator and a voltage controlled oscillator, wherein the output of the crystal oscillator is used as a third local signal source, and A transceiver that divides the output of the oscillator to obtain the frequency of the second local signal source. Since the second and third local signal source frequencies are obtained from the output of the crystal oscillator which is a component of the first local signal source, the circuit scale can be reduced, and miniaturization and cost reduction can be achieved.

According to a ninth aspect of the present invention, the pre-local signal source comprises a PLL synthesizer having a reference signal source and a voltage controlled oscillator, wherein the output of the reference signal source is used as a first local signal source. Divide the output of the reference signal source to
And a mixer for mixing the output of the pre-local signal source and the output of the reference signal source to output a transmission channel frequency signal, instead of the first local signal source signal. A transceiver for inputting the output of the mixer to a transmission amplifier. It is not necessary to greatly change the frequency of the first local signal source during transmission and reception, and the first local signal source can be simplified, so that downsizing and cost reduction can be achieved.

[0020]

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

(Embodiment 1) FIG. 1 is a block diagram showing the configuration of a transceiver according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a configuration of an image rejection mixer which is a component of the present invention. Also, FIG.
9 is a graph illustrating frequency characteristics of an output signal of a second image rejection mixer that is a component of the present invention. The transceiver according to the present embodiment will be described with reference to FIGS.

In FIG. 1, 1 is a first image rejection mixer, 2 is a second image rejection mixer, 3 is a first local signal source, 4 is a first local signal source,
Reference numeral 5 denotes a demodulation circuit, 6 denotes a transmission amplifier, 7 denotes an antenna, 8 denotes an antenna switch, 9 denotes a reception amplifier, and 10 denotes a demodulation data output terminal. In FIG. 2, 21 is a reception signal input terminal, 22 is an intermediate frequency signal output terminal, 23 is a local signal input terminal, 24 is a mixer, 25 is a +90 degree phase shifter, 26 is a +45 degree phase shifter, and 27 is -45. Degree phase shifter 28 is an adder.

First, the operation of the image rejection mixer shown in FIG. 2 will be described. The reception signal input to the reception signal input terminal 21 is branched and input to two mixers 24. The local signal input to the local signal input terminal 23 is branched and input to the two mixers 24. Here, the frequency of the local signal source input to the local signal input terminal 23 is set to be lower than the desired channel frequency of the received signal by half the channel frequency interval. The channel frequency interval is predetermined according to a frequency band to be used, and is a frequency interval at which channels are arranged. For example, in Japanese low-power radio in the 400 MHz band, the channel frequency interval is determined to be 12.5 kHz. In this case, the frequency of the local signal source is set 6.25 kHz lower than the desired channel frequency. Hereinafter, the case of this low-power radio will be described as an example.

The local signals input to the two mixers 24 have a phase difference of 90 degrees from each other because the +90 degree phase shifter 25 is inserted in one path. The received signal and the local signal are mixed by the two mixers 24, respectively, and the converted signal is output. One of the converted signals is +
The signal is input to the adder 28 via the 45-degree phase shifter 26.
The other is input to the adder 28 via the -45 degree phase shifter 27. The signal obtained by adding the two signals is output from the intermediate frequency signal output terminal 22.

In the image rejection mixer having the above configuration, the local signals orthogonal to each other are input to the two mixers 24, and the output signals of the two mixers 24 are also orthogonal to each other. Then, the +45 degree phase shifter 26 and -4
The relative phase is further rotated by 90 degrees by the 5-degree phase shifter 27. Here, the components of the received signal having a frequency higher than the local signal source frequency have the same phase at the outputs of the two mixers 24 and are added by the adder 28. The components of the received signal having a frequency lower than the local signal source frequency have opposite phases to each other at the outputs of the two mixers 24, so that the adder 2
8 cancels out and is suppressed.

In the above description, an adder is used.
The frequency to be suppressed can be changed by using a subtractor. That is, if a subtractor is used, components of the received signal having a frequency higher than the local signal source frequency are in phase with each other at the outputs of the two mixers, and are canceled out. In addition, components of the received signal having a frequency lower than the local signal source frequency have opposite phases at the outputs of the two mixers, and are added. By using the adder or the subtractor in this way, it is possible to select whether to suppress a component having a frequency higher than the local signal source frequency or a component having a lower frequency in the received signal.

Next, the transceiver will be described with reference to FIG.

First, the receiving operation will be described. The reception signal input to the antenna 7 is amplified by the reception amplifier 9 via the antenna switch 8. The output of the receiving amplifier 9 and the output of the first local signal source 3 are input to the first image rejection mixer 1. Here, the configuration of the first image rejection mixer 1 is as shown in FIG. The frequency of the first local signal source 3 is set to be lower than the desired channel frequency by half the channel frequency interval. Therefore, in the output of the first image rejection mixer 1, a frequency component higher than the first local signal source frequency of the received signal is output as the first intermediate frequency signal, and lower than the first local signal source frequency. Frequency components are suppressed. At this time, there is a signal component of a desired channel with a center frequency of 6.25 kHz of the first intermediate frequency signal.

Then, the first intermediate frequency signal, which is the output of the first image rejection mixer 1, and the output of the second local signal source 4 are input to the second image rejection mixer 2. Here, the second image rejection mixer 2 has the configuration shown in FIG. 2, but uses a subtractor instead of the adder. The frequency of the second local signal source 4 is set to 12.5 kHz, which is the same as the channel frequency interval. Therefore, the signal component of the desired channel is
The signal is converted again into a second intermediate frequency signal which is a signal centered at 6.25 kHz. Then, a frequency component lower than the second local signal source frequency 4 in the first intermediate frequency signal is subtracted by the subtractor and output, and a frequency component higher than the second local signal source frequency 4 is suppressed.

Then, the second intermediate frequency signal output from the second image rejection mixer 2 is output to the demodulation circuit 5
, And the demodulated output is output from the demodulated data output terminal 10.

FIG. 3 shows the frequency characteristics of the signal amplitude output from the second image rejection mixer 2. In FIG. 3, the horizontal axis represents the frequency, and the vertical axis represents the output amplitude of each frequency with reference to the output signal amplitude of the desired channel. The band indicated by A in FIG. 3 is the band of the desired channel. The band B is a component suppressed by the first image rejection mixer 1. The band of C is a component suppressed by the second image rejection mixer 2. Thus, the frequency components on both sides of the desired channel component are suppressed,
It has the characteristics of a channel selection filter.

In FIG. 3, the amount of suppression is 30 dB, but the amount of suppression is determined by the accuracy of the first and second image rejection mixers.

In the above embodiment, the case where the frequency of the first local signal source 3 is lower than the desired channel frequency has been described.
A configuration in which the frequency is set higher than the reception frequency can be adopted. That is, the frequency of the first local signal source 3 is set higher than the desired channel frequency by half the channel frequency interval. In this configuration, a subtractor is used instead of the adder of the first image rejection mixer 1. Thereby, a frequency component lower than the first local signal source frequency in the received signal is output as the first intermediate frequency signal, and a frequency component higher than the first local signal source frequency is suppressed.

Next, the transmission operation will be described. During transmission, the frequency of the first local signal source is changed to the frequency of the transmission channel. Consider the case of a radio band in which the reception channel frequency and the transmission channel frequency are the same. At the time of reception, the frequency of the first local signal source 3 was set to be lower than the reception channel frequency by 6.25 kHz. At the time of transmission, the frequency is changed from 6.25 kHz to match the transmission channel frequency.

Here, a method of changing the frequency will be described. The first local signal source 3 is constituted by a PLL synthesizer, and the comparison frequency is set to 6.25 kHz. The frequency is changed to 6.25 by changing the frequency division number by one.
kHz can be changed.

The output of the first local signal source 3 is
And is amplified by the antenna 7 via the antenna switch 8.
More radiated.

This transceiver has the following features.
The channel selection filter is composed of two image rejection mixers. Here, in order to obtain a steep attenuation characteristic using a g-mc filter which is an active filter conventionally used, it is necessary to configure a high-order filter, and the circuit scale becomes very large. On the other hand, as in the present embodiment, two image rejection mixers are used.
By obtaining the characteristics of the band-pass filter by forming the stages, the number of elements can be reduced, and the circuit scale can be greatly reduced. And current consumption can be reduced. Therefore, there is an advantage that the cost can be reduced because the chip size can be reduced when the semiconductor IC is used.

Another feature is that a change in the frequency of the first local signal source is small when switching from reception to transmission. In other words, the frequency variable range of the first local signal source may be small, and the configuration of the local signal source can be simplified.
Since the loop gain of the LL synthesizer can be reduced, the phase noise characteristic of the first local signal source can be improved.

The second local signal source frequency is constant even if the channel is changed. Therefore, a first local signal source is set to a P-channel oscillator having a crystal oscillator and a voltage-controlled oscillator as reference signal sources.
A second local signal source frequency can be obtained by configuring the LL synthesizer and dividing the output of the crystal oscillator. By adopting such a configuration, the transceiver of the present invention can be configured only by the voltage controlled oscillator and the crystal oscillator constituting the first local signal source.

That is, since a transceiver can be obtained without increasing the number of signal sources, the circuit scale can be reduced, and the size and cost can be reduced.

(Embodiment 2) FIG. 4 is a block diagram showing a configuration of a reference signal source which is a component of a first local signal source which is a component of a transceiver according to a second embodiment of the present invention. FIG.
, 31 is an inverter, 32 is a quartz oscillator, 33
Is a diode switch, 34 is a variable frequency capacitor, 35 is a capacitor, 36 is a resistor, 37 is a frequency control terminal, and 38 is a reference signal output terminal.

The overall configuration of the transceiver is the same as in FIG.
A feature of the present invention lies in the configuration of the first local signal source 3. That is, the change of the first local signal source frequency performed in reception and transmission is performed by the frequency control terminal 37. The first reference signal source 3 shown in FIG. 1 comprises a reference signal source comprising a crystal oscillator and a PLL frequency synthesizer comprising a voltage controlled oscillator. Here, the output frequency of the PLL synthesizer is determined by the frequency of the reference signal source. FIG. 4 shows the configuration of a reference signal source capable of changing the output frequency.

As in the case of the first embodiment, the frequency of the first local signal source 3 during reception is 6.2 times higher than the desired channel frequency.
Set lower by 5kHz. Here, the frequency control terminal 37 in FIG. 4 is controlled to have a high potential, and the diode switch 33 is turned on. Since one electrode of the frequency variable capacitor 34 is grounded, the crystal oscillator 32
Is the sum of the capacitor 35 and the capacity of the frequency variable capacitor 34. At this time, the respective constants are determined so that the first local signal source 3 is lower than the above-mentioned frequency, that is, the desired channel frequency by 6.25 kHz.

At the time of transmission, the frequency control terminal 37 is controlled to have a low potential, and the diode switch 33 is turned off. Thereby, the frequency variable capacitor 34
Is cut off, the load capacity of the crystal unit 32 is reduced, and the frequency of the first local signal source 3 is increased by 6.25 kHz, that is, the desired channel frequency.

As described above, the load capacitance of the crystal oscillator 32 is switched by the diode switch 33 to set the frequency of the first local signal source 3 to a frequency necessary for reception and transmission. The operation of changing the frequency of the signal source 3 can be realized with a simple circuit, and the transceiver can be made compact and at low cost.

(Embodiment 3) FIG. 5 is a block diagram showing a configuration of a PLL synthesizer constituting a first local signal source which is a component of a transceiver according to Embodiment 3 of the present invention. In FIG. 5, 41 is a crystal oscillator, 42 is a voltage controlled oscillator, 43 is a fractional frequency divider, 44 is a frequency divider, 45 is a phase comparator, 46 is a charge pump, 47 is a loop filter, and 48 is a voltage controlled oscillator output. Terminal.

The overall configuration of the transceiver is the same as in FIG.
A feature of the present invention is that the PLL constituting the first local signal source 3
In the synthesizer. That is, the PLL synthesizer shown in FIG. 5 includes the fractional frequency divider 43. The fractional frequency divider is a frequency divider whose frequency division number equivalently takes a fractional value by switching the frequency division number temporally. A signal obtained by dividing the output of the crystal oscillator 41 by the frequency divider 44 and the voltage-controlled oscillator 4
A signal obtained by dividing the output of 2 by the fractional frequency divider 43 is input to the phase comparator 45, and a signal corresponding to the phase difference between the two signals is output to the charge pump 46. Then, the output of the charge pump 46 is input to the frequency control terminal of the voltage controlled oscillator 42 via the loop filter 47. And
A feedback loop is configured so that the two signals input to the phase comparator 45 have the same frequency or phase difference.

Here, the output frequency of the frequency divider 44 is 12.
It is set to 5kHz. When the frequency division number of the fractional frequency divider 43 is n, the output frequency of the frequency divider / divider 43 becomes 12.5.
When the frequency is n- (1/2), the frequency of the first local signal source 3 is 6.25 kHz lower. However,
n: It is an integer. That is, the division number n is the division number at the time of transmission,
n- (1/2) corresponds to the frequency division number at the time of reception.

By using the fractional frequency divider in this manner, it is not necessary to add a circuit for changing the frequency, so that it is possible to reduce the size and cost of the circuit.

If the fractional frequency divider is used, the comparison frequency can be set higher. For example, 125kH of 10 times
can be z. As a result, the frequency convergence time of the PLL synthesizer can be reduced.

(Embodiment 4) FIG. 6 is a block diagram showing the configuration of a transceiver according to Embodiment 4 of the present invention. In FIG. 6, reference numeral 11 denotes a third image rejection mixer. The same components as those in FIG. 1 are denoted by the same reference numerals.

The difference between the present embodiment and the first embodiment is that the third image rejection mixer 11 is provided.
There is no need to change the frequency of the first local signal source for reception and transmission.

The operation at the time of reception is the same as in the first embodiment. The operation at the time of transmission is different. At the time of transmission, the second local signal source 4 operates at the frequency of the channel frequency interval, that is, 1
It is set to 2.5 kHz. Then, the outputs of the first and second local signal sources 3 and 4 are input to a third image rejection mixer 11. The third image rejection mixer 4 outputs a sum frequency component or a difference frequency component of the first local signal source frequency and the second local signal source frequency, and suppresses the difference component or the sum component. Thereby, the reception channel frequency and the transmission channel frequency can be made the same.

The third image rejection mixer 11 removes carrier leaks by suppressing not only the difference or sum frequency components but also the signals of the first and second local signal source frequencies. are doing.

As described above, since it is not necessary to change the frequency of the first local signal source 3 between reception and transmission, there is no need to provide a mechanism for changing the frequency by half of the channel frequency interval.
The configuration of the local signal source 3 can be simplified. Further, since there is no need to change the frequency of the first local signal source 3, the present invention can be applied to a system that performs communication by switching between transmission operation and reception operation in a short time, and the operation can be switched instantaneously.

In this embodiment, transmission and reception are performed by switching the frequency of the second local signal source 4. However, the third local signal source that outputs a frequency of 12.5 kHz during transmission is used. Is also good. In this case, the second local signal source 4 does not need to switch the frequency for transmission and reception.

(Embodiment 5) FIG. 7 is a block diagram showing the configuration of a transceiver according to Embodiment 5 of the present invention. In FIG. 7, 12 is a third local signal source, and 13 is a duplexer.
The same components as those in FIGS. 1 and 6 are denoted by the same reference numerals.

The difference between the present embodiment and the fourth embodiment is that the receiving operation and the transmitting operation can be performed simultaneously.

If the transmission channel is 20 for the reception channel
Consider the case of a radio band set to a frequency lower by MHz.

The operation of the receiving system is the same as in the first and sixth embodiments. The first local signal source 3 is set at a frequency 6.25 kHz lower than the reception channel frequency.

The operation of the transmission system will be described. The third local signal source 12 has the above-mentioned frequency between the transmission and reception channels of 2
5. From 0 MHz to one half of the channel frequency interval, ie, 6.
19.99375MHz which is the frequency which subtracted 25kHz
Is set to Then, the outputs of the first and third local signal sources 3 and 12 are input to a third image rejection mixer 11. The third image rejection mixer 11 outputs a sum frequency component or a difference frequency component of the first local signal source frequency and the third local signal source frequency,
The difference component or the sum component is suppressed. This allows
The output frequency of the third image rejection mixer 11 can be used as the transmission channel frequency.

The third image rejection mixer suppresses the difference or sum frequency components,
The carrier leak is removed by also suppressing the signals of the first and third local signal source frequencies.

Then, by separating the reception channel signal and the transmission channel signal by the duplexer, transmission can be performed simultaneously with reception.

Since the second and third local signal source frequencies are constant even when the channel is changed, the first local signal source is used as a PLL synthesizer having a crystal oscillator as a reference signal source and a voltage controlled oscillator. And a second local signal source frequency can be obtained by dividing the output of the crystal oscillator. Further, the output of the crystal oscillator can be used as a third local signal source. With this configuration, the transceiver of the present invention can be configured with only two signal sources, the voltage controlled oscillator and the crystal oscillator.

That is, a transceiver that performs reception and transmission simultaneously without increasing the number of signal sources can be obtained. As a result, the circuit scale of the transceiver is reduced, and downsizing and cost reduction can be achieved.

(Embodiment 6) FIG. 8 is a block diagram showing the configuration of a transceiver according to Embodiment 6 of the present invention. In FIG. 8, 14 is a pre-mixer, 15 is a pre-local signal source, 16
Is a high frequency filter.

The same components as those in FIG. 1 are denoted by the same reference numerals.

The difference between this embodiment and the first to fifth embodiments is that a front mixer 14 is provided. Receiver amplifier 9 and first
Premixer 1 between image rejection mixers 1
4 and the received signal has a frequency of 4
In the case of the 00 MHz band, it is converted to a relatively low frequency front frequency such as 20 MHz. Here, the pre-mixer 1
A high frequency filter 16 is provided in front of the receiving amplifier 9 in order to remove the image frequency component at 4.

The reason why the frequency is previously converted to a relatively low frequency and then input to the first image rejection mixer 1 is that the lower the frequency, the easier it is to increase the accuracy of the phase and amplitude of the signal. . Therefore, there is an advantage that the amount of attenuation as a channel selection filter can be easily increased. Further, when an image rejection mixer operating at a high frequency is configured, current consumption tends to increase. However, by using the pre-mixer 14 having a simple configuration,
Current consumption can be reduced.

The pre-local signal source is composed of a PLL synthesizer having a crystal oscillator and a voltage controlled oscillator as reference signal sources, and the output of the reference signal source is used as a first local signal source. The output of the source may be divided to obtain the frequency of the second local signal source. Further, at the time of transmission, a mixer may be provided for mixing the output of the pre-local signal source and the output of the crystal oscillator to obtain a transmission channel signal. Then, the output of the mixer may be input to the transmission amplifier instead of the first local signal source signal. Accordingly, it is not necessary to largely change the frequency of the first local signal source between reception and transmission, and the configuration of the first local signal source can be simplified. And size reduction and cost reduction can be realized. In the above configuration, it is necessary to change the frequency of the pre-local signal source by half of the channel frequency interval between transmission and reception. In the first to fifth embodiments, the method of changing the frequency can be the method of changing the frequency of the first local signal source, that is, the method of changing the frequency division number, changing the load of the crystal oscillator, or performing the frequency division.

Although the embodiment has been described with reference to the low power radio in the 400 MHz band, it goes without saying that the present invention is not limited to this frequency.

[0072]

As described above, according to the transceiver of the present invention, since the image rejection mixer is configured in two stages to obtain the characteristics of the bandpass filter, it can be configured with a small number of elements and the circuit scale can be greatly reduced. This has the effect of reducing power consumption as well as power consumption. Therefore, there is an advantage that the cost can be reduced because the chip size can be reduced when the semiconductor IC is used. Further, since the frequency variable range of the first local signal source may be small, there is an effect that the phase noise characteristic of the first local signal source can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transceiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an image rejection mixer according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a frequency characteristic of an output amplitude of a second image rejection mixer according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a crystal oscillator which is a component of a transceiver according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a PLL synthesizer that is a component of a transceiver according to a third embodiment of the present invention.

FIG. 6 is a block diagram of a transceiver according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a transceiver according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram of a transceiver according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram of a conventional transceiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st image rejection mixer 2 2nd image rejection mixer 3 1st local signal source 4 2nd local signal source 5 Demodulation circuit 6 Transmission amplifier 7 Antenna 8 Antenna switch 9 Receiving antenna 11 Third image rejection Action mixer 12 Third local signal source 14 Pre-mixer 24 Mixer 25 +90 degree phase shifter 26 +45 degree phase shifter 27 -45 degree phase shifter 28 Adder 31 Inverter 32 Crystal oscillator 33 Diode switch 34 For frequency change Capacitor 37 Frequency control terminal 41 Crystal oscillator (reference signal source) 42 Voltage controlled oscillator 43 Fractional frequency divider

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K011 DA04 DA08 KA03 KA04 5K020 DD02 DD11 DD13 EE05 FF04 GG04 GG09 GG10 GG11 GG25 MM04 MM11 MM12

Claims (9)

[Claims] 1. A receiving apparatus comprising: first and second local signal sources; first and second image rejection mixers; a demodulation circuit; and a transmission amplifier. The received signal and the output of the first local signal source are input to the first image rejection mixer and set to a frequency lower or higher by a half of a channel frequency interval than a desired channel frequency. And suppressing a frequency component lower or higher than the first local signal source frequency, converting a frequency component higher or lower than the first local signal source frequency of the received signal into a first intermediate frequency signal, and outputting the converted signal. And the second local signal source outputs a signal having the same frequency as the channel frequency interval, and supplies the first intermediate frequency signal to a second image rejection mixer. And the output of the second local signal source, and suppresses a frequency component higher than the second local signal source frequency in the first intermediate frequency signal, thereby suppressing the second intermediate signal in the first intermediate frequency signal. A frequency component lower than a local signal source frequency is converted into a second intermediate frequency signal, the second intermediate frequency signal is input to the demodulation circuit to perform demodulation, and at the time of transmission, the first local signal source is a transmission channel. A transceiver set to a frequency and amplifying the output of the first local signal source with the transmission amplifier. 2. The first local signal source comprises a PLL frequency synthesizer with a reference signal source and a voltage controlled oscillator,
2. The transceiver according to claim 1, wherein an output frequency of the first local signal source is changed by approximately one half of a channel frequency interval by varying an oscillation load capacity of the reference signal source during transmission and reception. . 3. The first local signal source comprises a reference frequency signal source, a voltage controlled oscillator, and a PLL frequency synthesizer having a frequency divider. The frequency division number of the frequency divider is a fractional value. 2. The transceiver of claim 1, wherein the output frequency of one local signal source is changed by approximately one-half of the channel frequency interval. 4. The first and second local signal sources;
Second and third image rejection mixers, a demodulation circuit, and a transmission amplifier, wherein at the time of reception, the first local signal source is lower or higher than a desired channel frequency of the received signal by a half of a channel frequency interval. The frequency is set, and the received signal and the output of the first local signal source are input to the first image rejection mixer, and a frequency component lower or higher than the first local signal source frequency among the received signal components And converts a higher or lower frequency component of the received signal than the first local signal source frequency into a first intermediate frequency signal, and outputs the first intermediate frequency signal.
Outputs a signal having the same frequency as the channel frequency interval, inputs the first intermediate frequency signal and the output of the second local signal source to a second image rejection mixer, A frequency component higher than the second local signal source frequency in the intermediate frequency signal is suppressed, and
Of the intermediate frequency signal, the frequency component lower than the second local signal source frequency is converted to a second intermediate frequency signal, the second intermediate frequency signal is input to the demodulation circuit to perform demodulation, The first local signal source is set to a frequency lower or higher by a half of a channel frequency interval than a transmission channel frequency, and the second local signal source is a signal having a frequency of a half of the channel frequency interval. And outputs the outputs of the first and second local signal sources to the third image rejection mixer, and outputs the frequency component of the difference between the first and second local signal source frequencies or the sum frequency component. Attenuates and outputs a sum frequency component or a difference frequency component of the first and second local signal source frequencies, and increases the output of the third image rejection mixer by the transmission amplifier. Transceiver for. 5. A first, second and third local signal source;
A first, second, and third image rejection mixer, a demodulation circuit, and a transmission amplifier, wherein the first local signal source is lower than a reception channel frequency of a reception signal by a half of a channel frequency interval or A high frequency is set, and at the time of reception, the received signal and the output of the first local signal source are input to the first image rejection mixer and the received signal component is lower than the first local signal source frequency or A high frequency component is suppressed, a frequency component higher or lower than the first local signal source frequency of the received signal is converted into a first intermediate frequency signal and output, and the second local signal source is configured to output the channel frequency. A signal having the same frequency as the interval is output, and an output of the first intermediate frequency signal and an output of the second local signal source are input to a second image rejection mixer. The frequency component higher than the second local signal source frequency in the first intermediate frequency signal is suppressed, and the frequency component lower than the second local signal source frequency in the first intermediate frequency signal is converted into a second intermediate frequency signal. The signal is converted to a frequency signal, and the second intermediate frequency signal is input to the demodulation circuit to perform demodulation. At the time of transmission, the third local signal source sets the frequency to the frequency of the difference between the reception channel frequency and the transmission channel frequency. A signal having a frequency obtained by adding or subtracting half the frequency of the channel frequency interval is output, and the outputs of the first and third local signal sources are input to the third image rejection mixer. And attenuates the difference frequency component or the sum frequency component of the third local signal source frequency and outputs the sum frequency component or the difference frequency component of the first and third local signal source frequencies. Transceiver for amplifying the output of said third image rejection mixer in the transmission amplifier. 6. A pre-mixer for converting a received signal into a pre-frequency signal having a frequency lower than the frequency of the received signal is provided in a stage preceding the first image rejection mixer. The transceiver according to any one of claims 1 to 5, which inputs a signal to the first image rejection mixer. 7. A first local signal source comprising a PLL synthesizer having a reference signal source and a voltage controlled oscillator, wherein said output of said reference signal source is frequency-divided to obtain a frequency of a second local signal source. The transceiver according to any one of claims 1 to 6. 8. The first local signal source comprises a PLL synthesizer having a reference signal source and a voltage controlled oscillator, wherein an output of the reference signal source is used as a third local signal source, and an output of the reference signal source is used as a third local signal source. 7. The transceiver according to claim 5, wherein the frequency is divided to obtain the frequency of the second local signal source. 9. A local signal source comprising a PLL synthesizer having a reference signal source and a voltage controlled oscillator, wherein an output of the reference signal source is used as a first local signal source, and an output of the reference signal source is divided. A second local signal source for obtaining a frequency of the second local signal source, and a mixer for mixing an output of the pre-local signal source and an output of the reference signal source to output a transmission channel frequency signal; 7. The transceiver according to claim 6, wherein an output of the mixer is input to a transmission amplifier instead of a source signal.