JP3084545B2 - Intermediate frequency generation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA (Time Division Multiple Access) used as a communication device or a broadcast receiver.
x Access: Time division multiple access (TDM) communication method and TDD (Time D
The present invention relates to an intermediate frequency generation method in a wireless unit of the ivision Duplex communication method. The TDMA communication system is a system in which each station uses the same frequency band as a frequency band of a signal to be transmitted and divides a time to be transmitted by each station on a time axis. The TDD communication system uses the same frequency band as a frequency band of a signal to be transmitted and a signal to be received,
This is a method of transmitting and receiving a transmission frequency signal and a reception frequency signal in a time-division manner.

[0002]

2. Description of the Related Art As an intermediate frequency generation system in a radio section of a conventional TDMA communication system, three systems shown in FIGS. 3, 4 and 5 are typical.

In each of these figures, reference numeral 1 denotes a transmitting / receiving antenna for transmitting a signal as a radio wave or receiving a radio wave;
Is a transmission / reception switch connected to the transmission block at the time of transmission and connected to the reception block at the time of reception because the antenna 1 shares transmission and reception, 3 is a reception system amplifier that amplifies a small signal at the time of reception, and 4 is the desired frequency to receive A band-pass filter that passes the signal of FIG. 1 and attenuates other frequency signals.
A first mixer for lowering the frequency by mixing with the local oscillation frequency signal to produce a first intermediate frequency signal; and 6 and 8 switching switches for switching the signal path between transmission and reception;
Reference numeral 7 denotes a band-pass filter that passes only the first intermediate frequency signal and attenuates other frequency signals, and 9 mixes the first intermediate frequency signal and the local oscillation frequency signal of the second local oscillator 11 to lower the frequency. A second mixer for producing an intermediate frequency signal, a band-pass filter for passing only the second intermediate frequency signal and attenuating other frequency signals, and a VCO section and a PLL section for generating a second local frequency signal The second local oscillator 12 mixes the second local frequency signal from the second local oscillator 11 and the same frequency signal as the second intermediate frequency signal to generate a signal having the same frequency as the first intermediate frequency signal. The third mixer (up-converter) 13 uses a signal having the same frequency as the second intermediate frequency signal to shift the transmission signal by π / 4 shift QP.
A quadrature modulator for performing SK modulation, 14 is a band-pass filter that passes only the second intermediate frequency signal and attenuates other frequency signals, 15 is a first local frequency signal from a first local oscillator 16 and a first local frequency signal. Mixing the same frequency signal as the intermediate frequency signal to generate a transmission frequency signal;
Mixer (upconverter), 16 is VCO part, P
A first local oscillator comprising an LL section for generating a first local frequency signal; 17 a band-pass filter for passing only the transmission frequency signal and attenuating other frequency signals;
Is a transmission amplifier for amplifying the transmission frequency signal.

In the first conventional example shown in FIG. 3, at the time of reception, a signal received from a transmission / reception antenna 1 includes a transmission / reception switch 2, a reception amplifier 3, and a band-pass filter 4.
, And is mixed with the first local frequency signal from the first local oscillator 16 by the first mixer 5 to become a first intermediate frequency signal. The first intermediate frequency signal is supplied to the changeover switch 6 and the band-pass filter 7. , Through the changeover switch 8,
The second mixer 9 mixes the second local frequency signal from the second local oscillator 11 with the second local frequency signal to form a second intermediate frequency signal, which is guided to the demodulator through the band pass filter 10.

At the time of transmission, a quadrature modulator 13 modulates a transmission signal with the same frequency signal as the second intermediate frequency signal, removes spurious components by a band-pass filter 14, and removes a second local signal by a third mixer 12. The signal is mixed with the second local frequency signal from the oscillator 11 to become the first intermediate frequency signal, passes through the changeover switch 8, the band-pass filter 7, and the changeover switch 6, and passes through the first mixer 15.
Is mixed with the first local oscillation frequency signal from the local oscillator 16 of FIG.
7, the signal is amplified by the transmission system amplifier 18, passed through the transmission / reception switch 2, and transmitted from the transmission / reception antenna 1.

In the second conventional example shown in FIG. 4, the operation at the time of reception is the same as that in the case of FIG. At the time of transmission, the quadrature modulator 13 modulates the transmission signal with the second local oscillation frequency signal from the second local oscillator 11 to produce a first intermediate frequency signal. The signal reaches the fourth mixer 15 through the switch 6, and thereafter is transmitted from the transmission / reception antenna 1 through the band pass filter 17, the transmission system amplifier 18, and the transmission / reception switch 2 in the same manner as in FIG.

In the third conventional example shown in FIG. 5, the operation at the time of reception is performed in the same manner as in FIG. 3 except that there are no changeover switches 6 and 8. At the time of transmission, the quadrature modulator 1
At 3, the transmission signal is modulated with the second local oscillation frequency signal from the second local oscillator 11 to form a first intermediate frequency signal, which passes through the band-pass filter 14 to the fourth mixer 15, and thereafter Are transmitted from the transmission / reception antenna 1 through the band pass filter 17, the transmission system amplifier 18, and the transmission / reception switch 2 in the same manner as in the case of FIG.

[0008]

In the case of the conventional example shown in FIG.
Although it is the simplest in circuit scale, in order to use the TDMA communication method, [transmission frequency] = [reception frequency].
The frequency difference of the second intermediate frequency signal is determined by the first local oscillator 1
6 and the second local oscillator 11 must cope with frequency switching.
In the communication system and the TDD communication system, the switching time becomes a very short time, and the local oscillator has a PL.
If an L circuit or the like is used, switching becomes difficult. Further, if the switching is performed in such a short time, the circuit configuration of the local oscillator becomes very large.

In the case of the conventional example shown in FIG. 4, the number of components is smaller than that of the conventional example shown in FIG. 3, so that the configuration can be simplified. However, unless the oscillation frequency of the second local oscillator 11 is switched between reception and transmission. Not bothersome. Compared with the conventional example of FIG. 5, the band-pass filter 7 is shared for transmission and reception. However, since the signal is modulated by the quadrature modulator 13 and then passes through the band-pass filter 7, the modulation is π / π. Since the bandpass filter 7 has a narrow band at the time of the 4-shift QPSK, the group delay characteristic deteriorates, and the modulation accuracy deteriorates. When the band of the band-pass filter 7 is widened, on the contrary, the selectivity characteristic at the time of reception deteriorates.

In the case of the conventional example of FIG. 3, it is not necessary to switch the oscillation frequency of the second local oscillator 11 as compared with the conventional example of FIG. 4, but the circuit scale becomes complicated. Also,
Since the narrow-band bandpass filter 7 is shared between transmission and reception, there is a problem of deterioration in modulation accuracy as in the conventional example of FIG.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made to eliminate the need for switching the local oscillation frequency, simplify the circuit configuration, and ensure good modulation accuracy. The purpose is.

[0012]

According to the first aspect of the present invention, there is provided an intermediate frequency generation system comprising a TDMA communication system or a TDD communication system.
An intermediate frequency generation system for a radio unit in a communication system, wherein a first mixer using a first local oscillation frequency signal is provided on one side of a common band pass filter for transmission and reception, and a second local oscillation frequency is provided on the other side. While a second mixer based on a signal is provided, a third mixer based on a second local frequency signal is provided on the other side of the common bandpass filter, and a fourth mixer based on the first local frequency signal is provided on one side. The third mixer is configured to mix the same frequency signal as the second local frequency signal and the second intermediate frequency signal, and is provided between the common band-pass filter and the fourth mixer. A quadrature modulator for modulating a transmission signal by a first intermediate frequency signal is inserted.

According to a second aspect of the present invention, there is provided an intermediate frequency generating system, comprising: a transmission / reception switch connected to a transmission / reception antenna; a reception amplifier, a band-pass filter, and a first mixer connected to a reception side of the transmission / reception switch. , A first local oscillator for providing a first local frequency signal to the first mixer to generate a first intermediate frequency signal, and a common band-pass filter for transmission and reception having a changeover switch at both ends. A second local oscillator that supplies a second local frequency signal to the second mixer to generate a second intermediate frequency signal; and a second local oscillator that supplies a second local frequency signal to the second mixer to generate a second intermediate frequency signal. A third mixer for mixing a frequency signal identical to the second local frequency signal and the second intermediate frequency signal from the local oscillator to generate a first intermediate frequency signal; A quadrature modulator for modulating a transmission signal based on a first intermediate frequency signal from a mixer, a band-pass filter connected to the quadrature modulator, and a signal from the first local oscillator connected to the band-pass filter. A fourth mixer for mixing the first local oscillation frequency signal to generate a transmission frequency signal, a series circuit including a band-pass filter inserted between the fourth mixer and the transmission / reception switch, and a transmission amplifier; The output side of the first mixer and the input side of the quadrature modulator are connected to a changeover switch at one end of the common band-pass filter, and the input side of the second mixer and the third side are connected to each other. The output side of the mixer is connected to a changeover switch at the other end of the common bandpass filter.

[0014]

The third mixer mixes the same frequency signal as the second local oscillation frequency signal and the second intermediate frequency signal to generate the first intermediate frequency signal, and narrows the signal in a carrier state before modulation. Since the signal is passed through a band-pass filter of the band and then modulated by the quadrature modulator, it is not necessary to switch the frequency of the second local oscillation frequency signal between the time of transmission and the time of reception. The configuration of the oscillator can be simplified.

Also, a third intermediate frequency signal generating third signal is generated.
The mixer of this type still mixes at a low frequency stage, so that it can be composed of simple components such as transistors and diodes. Since switching between transmission and reception can be performed by performing a switching operation, the switching time between transmission and reception can be very short.

Furthermore, since a common band-pass filter passes only a carrier wave during transmission, a narrow-band band-pass filter designed only with reception characteristics can be adopted. Also, T
The modulation accuracy does not deteriorate in the DMA communication system and the TDD communication system.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an intermediate frequency generating system according to the present invention.

FIG. 1 is a circuit diagram showing the configuration of the intermediate frequency generation system in the radio section of the TDMA communication system.

As shown in FIG. 1, a transmission / reception switch 2 that connects to a transmission block during transmission and connects to a reception block during reception is connected to a transmission / reception antenna 1 that transmits and receives signals as radio waves. A reception amplifier 3, a bandpass filter 4, and a first mixer 5 are connected in series to a reception terminal of the transmission / reception switch 2. The reception amplifier 3 amplifies a small signal at the time of reception, the band-pass filter 4 passes a signal of a desired frequency to be received and attenuates other frequency signals, and the first mixer 5 receives the signal. Frequency signal
Is mixed with the local oscillation frequency signal of the local oscillator 16 to lower the frequency to produce a first intermediate frequency signal. First
The local oscillator 16 comprises a VCO section and a PLL section and generates a first local oscillation frequency signal.

A first mixer 5 is connected to a second mixer 9 via a series circuit including a changeover switch 6, a bandpass filter 7 and a changeover switch 8. The changeover switches 6 and 8 switch the signal path between transmission and reception, and the bandpass filter 7 passes only the first intermediate frequency signal and attenuates other frequency signals. The second mixer 9 receives the first intermediate frequency signal and the second intermediate frequency signal.
Of the local oscillator 11 of the local oscillator 11 to lower the frequency to produce a second intermediate frequency signal. Second
The band pass filter 10 connected to the mixer 9 passes only the second intermediate frequency signal and attenuates other frequency signals. The second local oscillator 11 is a VCO
And a PLL unit for generating a second local oscillation frequency signal.

A third mixer (up) for mixing the second local oscillator signal from the second local oscillator 11 and the same frequency signal as the second intermediate frequency signal to produce the same frequency signal as the first intermediate frequency signal A converter 12 is provided, and the third mixer 12 is connected to a band-pass filter 7 common to transmission and reception via a changeover switch 8. One end of the changeover switch 6 connected to the bandpass filter 7 is connected to the first mixer 5, while the other end is connected to the quadrature modulator 13. That is, a quadrature modulator 13 that modulates a transmission signal by π / 4 shift QPSK with a first intermediate frequency signal is provided to a third mixer 12 by connecting a changeover switch 8, a bandpass filter 7, and a changeover switch 6 in series. They are connected via a circuit.

The output side of the quadrature modulator 13 is connected to a fourth mixer 15 via a band pass filter 14. The band pass filter 14 passes only the first intermediate frequency signal and attenuates other frequency signals. The fourth mixer 15 is an up-converter that mixes the first local oscillator signal from the first local oscillator 16 and the same frequency signal as the first intermediate frequency signal to generate a transmission frequency signal. The fourth mixer 15 is connected to a transmission terminal of the transmission / reception switch 2 via a band pass filter 17 and a transmission amplifier 18. The band-pass filter 17 passes only the transmission frequency signal and attenuates other frequency signals, and the transmission amplifier 18 amplifies the transmission frequency signal.

Next, the operation will be described.

The frequency of the second local frequency signal generated by the second local oscillator 11 is the same at the time of transmission and at the time of reception,
There is no need to switch.

At the time of transmission, the third mixer 12 mixes a fixed second local oscillation frequency signal from the second local oscillator 11 and a frequency signal identical to the second intermediate frequency signal to form a first intermediate frequency signal. Then, the signal passes through the changeover switch 8 to reach the band-pass filter 7, and the spurious is removed by the band-pass filter 7. Then, the light reaches the quadrature modulator 13 through the changeover switch 6, and the quadrature modulator 1
At 3, the transmitted signal is modulated with the same frequency signal as the first intermediate frequency signal. Next, the light passes through a broadband bandpass filter 14 and reaches a fourth mixer 15. In the fourth mixer 15, the signal is mixed with the first local oscillation frequency signal from the first local oscillator 16 to become a transmission frequency signal,
The signal passes through the band-pass filter 17, is amplified by the transmission amplifier 18, passes through the transmission / reception switch 2, passes through the transmission / reception antenna 1,
Sent from

At the time of reception, a signal received from the transmission / reception antenna 1 passes through the transmission / reception switch 2, the reception system amplifier 3, and the band-pass filter 4, and is passed through the first mixer 5 to the first local oscillator 16 from the first local oscillator 16. The first intermediate frequency signal is mixed with the generated frequency signal to form a first intermediate frequency signal. The first intermediate frequency signal passes through the changeover switch 6, the bandpass filter 7 and the changeover switch 8, and is transmitted from the second local oscillator 11 by the second mixer 9. Is mixed with the second local oscillation frequency signal to form a second intermediate frequency signal, which is guided to the demodulator through the band pass filter 10.

As described above, in the third mixer 12, the second local oscillator signal from the second local oscillator 11 and the same frequency signal as the second intermediate frequency signal are mixed to produce the first intermediate frequency signal. It is generated.
Further, in the state of the carrier before the modulation, the signal is passed through a narrow-band bandpass filter 7 common to transmission and reception, and then modulated by the quadrature modulator 13.

With the above configuration, it is not necessary to switch the frequency of the second local oscillation frequency signal between transmission and reception, and the configuration of the second local oscillator 11 can be simplified.

The third mixer 12 for generating the first intermediate frequency signal has a low frequency (unmodulated wave).
Since the mixing is performed at the stage, it can be easily constituted by transistors, diodes, and the like. An example is shown in FIG. Switching between transmission and reception can also be performed by performing a switching operation, so that the switching time between transmission and reception is very short.

Further, since the frequency of the first intermediate frequency signal is the same at the time of transmission and at the time of reception, the band-pass filter 7
Can be used in common, and the number of components can be reduced and the cost can be reduced.

The common band-pass filter 7 allows only a carrier wave to pass at the time of transmission, so that the modulation accuracy does not deteriorate in the TDMA communication system and the TDD communication system, and the π / 4 shift QP
It is possible to cope with a modulation method having a severe group delay characteristic such as SK. Then, a narrow-band bandpass filter designed only with the reception characteristics can be adopted.

As described above, according to this embodiment, the problems of all of the first to third conventional examples are solved.

[0033]

In the third mixer, the first intermediate frequency signal is generated by mixing the same frequency signal as the second local oscillation frequency signal and the second intermediate frequency signal.
In addition, since the signal is passed through a narrow-band bandpass filter in the state of the carrier before the modulation, and then modulated by the quadrature modulator, the frequency of the second local oscillation frequency signal is transmitted and received. There is no need to switch over time, and the configuration of the second local oscillator can be simplified.

The third intermediate frequency signal is generated by a third
Since the mixer of this type still mixes at the low frequency stage, it can be easily composed of transistors and diodes, and the switching between transmission and reception can be switched by performing the switching operation, so the switching time between transmission and reception is also reduced. Can be very short.

Further, since the common band-pass filter passes only a carrier wave during transmission, the TDMA communication system
In the DD communication system, the modulation accuracy is not deteriorated, and it is possible to cope with a modulation system having a severe group delay characteristic such as π / 4 shift QPSK.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an intermediate frequency generation system according to one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific example of a third mixer in the embodiment.

FIG. 3 is a circuit diagram showing a configuration of an intermediate frequency generation system according to a first conventional example.

FIG. 4 is a circuit diagram showing a configuration of an intermediate frequency generation system according to a second conventional example.

FIG. 5 is a circuit diagram showing a configuration of an intermediate frequency generation system according to a third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmission / reception antenna 2 ... Transmission / reception changeover switch 3 ... Reception system amplifier 4 ... Bandpass filter 5 ... 1st mixer 6 ... Changeover switch 7 ... Common bandpass filter for transmission and reception 8 ... Changeover switch 9 second mixer 10 band-pass filter 11 second local oscillator 12 third mixer 13 quadrature modulator 14 band-pass filter 15 fourth mixer 16 First local oscillator 17 Band-pass filter 18 Transmitting amplifier

Claims (2)

(57) [Claims] An intermediate frequency generation method for a radio unit in a TDMA communication system or a TDD communication system,
One side of a common band-pass filter for reception is provided with a first mixer based on a first local frequency signal, and the other side is provided with a second mixer based on a second local frequency signal. A third mixer based on the second local frequency signal is provided on the other side, and a fourth mixer based on the first local frequency signal is provided on one side, and the second local frequency signal and the third mixer are provided in the third mixer. A quadrature modulator configured to mix the same frequency signal as the second intermediate frequency signal and inserting a quadrature modulator for modulating a transmission signal with the first intermediate frequency signal is inserted between the common band pass filter and the fourth mixer. An intermediate frequency generation method, characterized in that: 2. A transmission / reception switch connected to a transmission / reception antenna, a series circuit of a reception amplifier, a bandpass filter, and a first mixer connected to a reception side of the transmission / reception switch, and a first mixer. A first local oscillator for giving a first local oscillation frequency signal to generate a first intermediate frequency signal, a common transmission and reception band-pass filter having a changeover switch at both ends, a second mixer and a band-pass filter; A series circuit; a second local oscillator for providing a second local frequency signal to the second mixer to generate a second intermediate frequency signal; a second local oscillator signal from the second local oscillator; (2) a third mixer that mixes the same frequency signal as the intermediate frequency signal to generate a first intermediate frequency signal, and based on the first intermediate frequency signal from the third mixer. A quadrature modulator for modulating a transmission signal, a band-pass filter connected to the quadrature modulator, and a first local frequency signal from the first local oscillator connected to the band-pass filter for transmission. A fourth mixer for generating a frequency signal, and a series circuit of a band-pass filter and a transmission system amplifier inserted between the fourth mixer and the transmission / reception switch, and an output of the first mixer. And the input side of the quadrature modulator are connected to a changeover switch at one end of the common band-pass filter, and the input side of the second mixer and the output side of the third mixer are connected to the common band-pass filter. An intermediate frequency generation system, which is connected to a changeover switch at the other end of the filter.