JP3422909B2 - transceiver - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a portable radio such as radio, particularly to radios that utilized the transmission rate of the reception signal to the variable can be a wireless communication system.

[0002]

2. Description of the Related Art In recent years, the number of subscribers of mobile radio equipment represented by PHS and mobile phones has been increasing. Along with this, it is no longer possible to support the frequencies that have been allocated so far, and there is a strong demand for improvement in frequency utilization efficiency. One of the techniques for improving the frequency utilization efficiency is a variable rate transmission system adapted to the amount of information.

For variable rate transmission, baseband signals such as voice and data signals and RF radiated from an antenna are used.
(Radio Frequency) A direct conversion method for directly modulating / demodulating signals is desired. This is because it is generally difficult to manufacture a filter whose frequency characteristic is variable depending on the transmission rate, and the direct conversion method requires a smaller number of filters than the heterodyne method. Further, the variable filter required for the direct conversion method can be only a variable filter for baseband, which is generally easy to manufacture.

However, for items other than the variable filter, it is more difficult to realize a wireless device using the direct conversion system than a wireless device of the heterodyne system. This will be explained below.

In the transmission system using the direct conversion system, since the local oscillation frequency and the RF signal are the same frequency,
Interference of the RF output signal with the local oscillator occurs.
That is, the modulated signal is added to the oscillation signal of the local oscillator. As a result, the modulation accuracy of the RF signal is greatly deteriorated. In order to reduce the interference with the local signal oscillator, as shown in FIG. 11, there is a method in which two local signals 1stLO and 2ndLO are prepared and the frequency obtained by adding or subtracting these frequencies is used as the transmission frequency. When this method is adopted, interference with the oscillator is reduced, so that deterioration of modulation accuracy and the like is reduced. However, in this method, the local signal system uses the heterodyne method in order to obtain the local frequency to be transmitted, so that it has an advantage in reducing the number of parts, which is an advantage of the direct method as compared with the normal heterodyne method. Absent.

On the other hand, in the direct conversion receiving system,
It is known that the secondary distortion of the frequency converter and the DC offset generated in the frequency converter or the baseband amplifier deteriorate the reception characteristics. Therefore, a general wireless device uses the heterodyne system for both transmission and reception.

[0007]

However, in this way, both the transmitting and receiving systems are realized by using the heterodyne system .
The radios, the variable filter of the intermediate frequency stage is required in addition to the variable filter of the baseband in both transmission and reception system.
This IF stage variable filter is difficult to manufacture, and generally has problems such as a large volume and a high manufacturing cost.

[0008] The present invention is intended to solve such a problem, both the transmission system and the reception system can eliminate a variable filter of the IF stage, and aims to realize an inexpensive radios in small Te following .

[0009]

To achieve the above object, according to the solution to ## radios of the present invention, the second oscillating a first oscillator for oscillating a first frequency signal, the second frequency signal An oscillator, a multiplier that multiplies the frequencies of the first and second frequency signals to generate a transmission local signal, and a quadrature that directly converts a baseband signal into a transmission frequency band by the generated transmission local signal. A modulator, a frequency converter for converting a received signal into an intermediate frequency signal by the first frequency signal, and an intermediate frequency signal output from the frequency converter having a maximum frequency band of a variable transmission rate as a pass band. And a band-pass filter for limiting the band.

That is, according to the present invention, in a transmission system, a local signal for transmission is generated from two local signals by a multiplier, and a quadrature modulator directly converts a baseband signal into a transmission frequency band by the local signal for transmission. Also, by adopting the heterodyne method in the receiving system and setting the maximum bandwidth of the variable transmission rate as the band of the filter in the intermediate frequency band, it is easy to eliminate the variable filter in the IF stage from the transmitting system and the receiving system. It is possible to realize a variable rate wireless device having various configurations.

Also, the frequency of the received RF signal and the first
Where f is the frequency of the absolute value of the difference from the frequency f1 of the frequency signal and n · f2 is an integer multiple of the frequency f2 of the second frequency signal (where n is an integer, f1> f2),
By satisfying f> n · f2 or f <n · f2, it is possible to prevent the reception unit from receiving the leakage of the transmission signal and improve the reception performance.

Further, the clock frequency fck of the D / A converter that generates the baseband signal for transmission is set to at least twice the transmission band, and the pass band fLPF of the low-pass filter provided in the subsequent stage of the D / A converter is set. It is configured to be variable depending on the transmission band so that it is equal to or more than the transmission band and less than or equal to 1/2 of fck, or the clock frequency fck is at least twice the maximum frequency of the transmission band and fixed regardless of the transmission band. And the pass band fLPF of the low-pass filter is variable according to the transmission band so that it is equal to or greater than the transmission band and equal to or less than 1/2 of fck. A signal can be generated.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a transmission / reception unit of a variable rate radio device according to an embodiment of the present invention. This embodiment is FDD
A (Furequency Domain Duplex) type wireless communication system is assumed, and therefore, a duplexer (DUP) is inserted between the antenna (AT) and the transmission unit and the reception unit.

The local signal of the transmission system multiplies a frequency signal from a first oscillator (1stLO) having a synthesizer and a frequency signal from a fixed oscillator (2ndLO) which is a second oscillator by a multiplier (MIX1). Is generated by Of the output of the multiplier (MIX1), unnecessary waves other than the desired local frequency are detected by a bandpass filter (BP).
It is attenuated to a predetermined value by F1).

Since the base band signal of the transmission system corresponds to the variable rate, the clock frequency of the D / A converter (not shown) in the base band signal processing unit (BB) is at least twice the band of the base band signal. The above frequency is used. The clock speed of the D / A converter may be changed according to the transmission band, or may be fixed to twice or more the maximum band of the transmission band. With this configuration, it is possible to generate a baseband signal in all transmission bands without causing aliasing distortion.

The low-pass filters (LPF1, LPF2) for baseband signals are baseband processing units (BB).
It removes the harmonic components of the baseband signals (Ich, Qch) output from. These low-pass filters (LPF1, LPF2) can change the frequency characteristic according to the transmission band of the baseband signal so that aliasing distortion can be removed. However, when the clock of the D / A converter in the baseband processing unit (B) is fixed at the frequency required at the maximum transmission rate regardless of the transmission band, low-pass filters (LPF1, LPF) are used.
There is no problem even if the characteristic of 2) is fixed to the pass characteristic required for the maximum transmission rate.

Low-pass filters (LPF1, LPF2)
The baseband signal (Ic
h and Qch are 90 degree phase shifters (φ), mixers (MIX)
2, MIX3) and an adder (ADD) are used to convert to a desired RF signal. Although not shown, the generated RF signal is amplified by a power amplifier or the like and then input to a duplexer (DUP).

By configuring the transmission system in this way, the variable IF filter, which was required in the conventional variable rate transmission system of the heterodyne system, becomes unnecessary, and the configuration can be simplified. Therefore, the configuration of the transmission system shown in FIG. 11 plays an important role when applied to variable rate transmission.

The structure of the receiving system is the same as the conventional heterodyne system. That is, the RF signal obtained through the image removal filter (BPF3) that removes unnecessary components of the image frequency is multiplied by the multiplier (MI) using the oscillator (1stLO).
X4) converts into an IF signal. This IF signal is passed through a bandpass filter (BPF4), and then received IF.
It is converted into a baseband signal or a lower frequency IF signal (hereinafter referred to as a second IF signal) by a frequency converter included in the stage filter (RIF). When converted into the second IF signal, a variable filter is required in the second IF stage, but since the variable filter does not have to be used as the bandpass filter (BPF4) of the IF stage, the overall configuration is simple and low cost. Can be realized.

In a normal heterodyne type variable rate radio, the bandpass filter (BPF4) is a RIF.
This is an image removal filter for frequency conversion of the second IF signal performed in blocks, but the bandpass filter (BPF4) in this embodiment has a channel selection function as well as image removal.

That is, as shown in FIG. 2, when the pass band of the band pass filter (BPF4) is the maximum bandwidth BWmax of the variable rate, the center frequency of the desired signal frequency-converted by the multiplier (MIX4) is , Oscillator (1
The center frequency fcenter of the bandpass filter (BPF4) can be adjusted by adjusting the frequency of stLO).

Therefore, in the case of transmission with the maximum bandwidth, the bandpass filter (BPF4) can suppress the image of the received signal and also perform channel selection.

When the signal is transmitted with the maximum bandwidth or less, only the image suppression of the received signal is performed by the bandpass filter (BPF4) as in the past. in this case,
The channel is selected by the variable filter provided in the RIF block or the second IF unit or the baseband unit after the RIF block.

With this configuration, the radio can be realized without changing the band pass filter (BPF4) in the IF stage according to the transmission rate, which is not only technically easy, but also the price of the radio is low. Can be realized.

FIG. 3 shows the present invention according to TDD (Time Domain Dupl).
FIG. 9 is a diagram showing a configuration of another embodiment of a transmission / reception unit of a variable rate radio when applied to the system in ex).

In this embodiment, the duplexer (DUP) of the previous embodiment is transmitted / received by a switch (T / R).
It is configured by replacing. Since the effectiveness of this embodiment is the same as that shown in the case of FDD, the description is omitted.

Next, the frequency f1 of the oscillator (1stLO),
Oscillator (2stLO) frequency f2, transmission frequency fTX,
Reception frequency fRX and bandpass filter (BPF
A method of setting the center frequency fcenter of 4) will be described.

First, the case where the transmission frequency fTX and the reception frequency fRX are different will be described.

FIG. 4 shows the case of f1 <fTX <fRX. In this case, fcenter = fRX-f1 and f2 =
The wireless device can be realized by setting fTX-f1.

FIG. 5 shows the case where fTX <fRX <f1. In this case, fcenter = f1-fRX and f2 =
By setting f1-fTX, the above radio can be realized.

FIG. 6 shows the case where fRX <fTX <f1. In this case, fcenter = f1-fRX and f2 =
By setting f1-fTX, the above radio can be realized.

FIG. 7 shows the case of f1 <fRX <fTX. In this case, fcenter = fRX-f1 and f2 =
The wireless device can be realized by setting fTX-f1.

Next, the case where the transmission frequency fTX and the reception frequency fRX are the same as seen in PHS and the like will be described.

FIG. 8 shows the case where f1 <fTX = fRX. In this case, fcenter = f2 = fRX (fTX)-
The wireless device can be realized by setting f1.

FIG. 9 shows the case of f1> fTX = fRX. In this case, fcenter = f2 = f1-fRX (fT
The wireless device can be realized by setting X).

Next, a case will be described in which the spurious of the transmission signal, which is a problem in the case of FDD, is superimposed on the reception signal. FIG. 10 shows a state in which there is a relationship of fcenter = 2 · f2. Local frequency f1 + for transmission
f2 [Ηz] is obtained by multiplying the signals of f1 [Ηz] and f2 [Ηz] by the multiplier (MIX1) shown in FIG. However, in general, there is distortion in the multiplier, so
A component of f1 + 2 · f2 [Z] is generated. This frequency component becomes transmission spurious, so f1 + 2 · f
The transmission spurious caused by the component of 2 [Ηz] should be below the allowable value so that the filter (B) after the multiplier (MIX1)
Attenuation is performed using PF1). However, in the FDD system, the transmission / reception unit operates at the same time, so if this spurious frequency f1 + 2 · f2 [Ηz] is leaked to the reception unit via the duplexer (DUP) or space, this signal is treated as an unnecessary wave. I will receive it. As a result, the reception performance of the wireless device deteriorates. In consideration of this leakage, a bandpass filter (BPF)
This problem can be avoided by setting the characteristic of 1), but it is generally difficult because it is necessary to consider coupling through space.

Therefore, in order to prevent the leakage of the transmission signal from being received by the receiving section, the frequency is set as follows so that the leakage of the transmission signal is not superimposed on the reception signal. One of the conditions for not overlapping is the following frequency relationship between fcenter and f2.

Fcenter ≠ nf2 (where n is an integer) By satisfying such a relationship, it is possible to suppress deterioration of reception performance. In this embodiment, n is set to 2 for the sake of simplicity, but similar problems occur with f2 and fcenter.
Since it occurs when and are in an integral multiple relationship, n is an integer.

[0040]

As described above, according to the present invention, in a transmission system, a local signal for transmission is generated from two frequency signals by a multiplier, and a baseband signal is generated by the local signal for transmission by an orthogonal modulator. Is directly converted to the transmission frequency band, and the heterodyne system is adopted in the reception system, and the maximum bandwidth of the variable transmission rate is set as the band of the filter of the intermediate frequency band, so that the transmission can be performed without degrading the performance. It is possible to realize a variable rate wireless device having a simple configuration that does not require a variable filter at the IF stage from the system and the receiving system.

Further, according to the present invention, the frequency of the absolute value of the difference between the frequency of the received RF signal and the frequency f1 of the first frequency signal is f, and the value is an integer multiple of the frequency f2 of the second frequency signal. Letting n · f2 (where n is an integer, f1> f2) and satisfying the condition of f> n · f2 or f <n · f2, it is possible to prevent the reception section from receiving the leakage of the transmission signal. It is possible to improve the reception performance.

Further, according to the present invention, the clock frequency fc of the D / A converter for generating the baseband signal for transmission is generated.
k is at least twice the transmission band, and the pass band fLPF of the low-pass filter installed after the D / A converter
To be equal to or more than the transmission band and less than or equal to 1/2 of fck,
It is configured to be variable depending on the transmission band,
Alternatively, the clock frequency fck is set to be at least twice the maximum frequency of the transmission band and fixed regardless of the transmission band,
By configuring the low-pass filter so that the pass band fLPF is greater than or equal to the transmission band and less than or equal to ½ of fck, the baseband signal is generated for all transmission bands without causing aliasing distortion. Can be generated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a transmission / reception unit of a variable rate radio device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a variable rate signal.

FIG. 3 is a diagram showing a configuration of a transmission / reception unit of a variable rate wireless device according to another embodiment of the present invention.

4 is a diagram showing a method of setting a center frequency in the bandpass filter (BPF4) of FIG. 1 (f1 <fTX <fR
For X)

5 is a diagram showing a method of setting a center frequency in the bandpass filter (BPF4) of FIG. 1 (fTX <fRX <f
1)

6 is a diagram showing a method of setting a center frequency in the bandpass filter (BPF4) of FIG. 1 (fRX <fTX <f
1)

7 is a diagram showing a method of setting a center frequency in the bandpass filter (BPF4) of FIG. 1 (f1 <fRX <fT
For X)

8 is a diagram showing a method of setting a center frequency in the band pass filter (BPF4) of FIG. 1 (f1 <fTX = fR
For X)

9 is a diagram showing a method of setting a center frequency in the bandpass filter (BPF4) of FIG. 1 (f1> fTX = fR).
For X)

FIG. 10 is an explanatory diagram of reception characteristic deterioration due to local spurious.

FIG. 11 is a diagram showing a conventional direct modulation method that prevents interference with a local oscillator.

[Explanation of symbols]

AT ... antenna DUP ... Duplexer MIX1 to 4 ... Mixer (multiplier) 1stLO ... first oscillator 2ndLO: second oscillator BPF1 to 4 ... Bandpass filter LPF: Low-pass filter for baseband signals RIF: IF stage signal processing unit for reception ADD ... Adder BB: Baseband signal processing unit

Claims (4)

(57) [Claims] 1. A first oscillator that oscillates a first frequency signal, a second oscillator that oscillates a second frequency signal, and a transmitter for multiplying the frequencies of the first and second frequency signals. A multiplier for generating a local signal, a quadrature modulator for directly converting a baseband signal into a transmission frequency band by the generated local signal for transmission, and a quadrature modulator for converting a reception signal into an intermediate frequency signal by the first frequency signal. A radio device comprising: a frequency converter; and a bandpass filter having a maximum frequency band of a variable transmission rate as a pass band and band-limiting the intermediate frequency signal output from the frequency converter. 2. The radio device according to claim 1, wherein the frequency of the absolute value of the difference between the frequency of the received RF signal and the frequency f1 of the first frequency signal is f, and the frequency f2 of the second frequency signal is f2. Let n · f2 (where n is an integer, f1> f2) be an integer multiple of f, and f> n · f2 or f <n
-A radio characterized by satisfying f2. 3. The radio device according to claim 1, further comprising: a D / A converter that generates a baseband signal for transmission, and a low-pass filter that is provided in a subsequent stage of the D / A converter, The clock frequency fck of the A converter has at least twice the transmission band, and is variable by the transmission band so that the pass band of the low-pass filter is not less than the transmission band and not more than 1/2 of fck. And a radio. 4. The D / A converter for generating a baseband signal for transmission and the D / A according to claim 1.
With a low-pass filter installed in the latter stage of the converter,
The clock frequency fck of the D / A converter is at least twice the maximum frequency of the transmission band, and the pass band of the low pass filter is set to the maximum frequency of the transmission band or more and half of fck or less. A wireless device characterized by being fixed regardless of the transmission band.