JP2937866B2 - Wireless transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmission device, and more particularly to a radio transmission device provided with a cable loss compensation circuit for a cable connecting an indoor unit and an outdoor unit.

[0002]

2. Description of the Related Art In a conventional radio transmitting apparatus, only an antenna and a transmitting section are provided as outdoor units so that work can be performed indoors as much as possible. As a unit,
A configuration in which both units are connected by a signal cable is often used. However, since there is a loss due to the signal cable connecting between both units, the level of the signal received by the outdoor unit from the indoor unit via the signal cable is reduced by the loss due to the signal cable, and signal amplitude compensation is required. May be. As an example of an outdoor unit that constitutes a circuit in consideration of the loss due to such a signal cable, an ALC (Automatic Level C) disclosed in Japanese Patent Application Laid-Open No. 1-143411 is disclosed.
There is an example of a transmission power control circuit using an (control) circuit. This transmission power control circuit detects the output level, compares the detected level with a predetermined set level,
If the output level is large, the attenuation of the variable attenuator is adjusted so as to increase, and if the output level is small, the attenuation is adjusted so that the attenuation of the variable attenuator is small so that the output level is controlled to be constant. .

On the other hand, not only does a signal cable suffer from loss, but also the frequency characteristics change with the length of the signal cable, so it is necessary to compensate not only the signal level but also the frequency characteristics. If the type of signal cable is constant, the frequency characteristics of the signal cable are uniquely determined by the length, but at the same time, the loss is also uniquely determined by the length,
When a signal cable is used, its frequency characteristics can be estimated by detecting the loss amount. For this reason, conventionally, as shown in FIG. 3, a varactor diode or the like is further provided in the main signal line of the wireless transmission device so that the conductance can be changed according to the detection level. It has been practiced to insert a loss of the frequency characteristic as a characteristic into the main signal line to compensate for the frequency characteristic that changes depending on the length of the signal cable.

[0004] However, as shown in FIG. 4, the compensation of the frequency characteristics requires that the correction amount of the frequency characteristics of the main signal line be increased as the signal cable becomes longer. In addition, when correcting the frequency characteristic of the signal cable, the larger the correction, that is, the larger the primary slope of the main signal line, the more the circuit of the frequency characteristic compensation circuit unit becomes, as shown in FIG. Since the loss increases, the signal cable compensating circuit needs a gain to compensate for the total loss of the maximum loss of the signal cable and the circuit loss of the frequency characteristic compensating circuit.

[0005]

In the above-mentioned conventional radio transmission apparatus, the frequency characteristic compensation requires a larger correction amount of the frequency characteristic of the main signal line as the signal cable becomes longer. When correcting the frequency characteristic, the larger the correction, the greater the circuit loss of the frequency characteristic compensation circuit section.Therefore, the signal cable compensation circuit includes the maximum loss of the signal cable and the frequency characteristic compensation circuit. There is a disadvantage that a gain for compensating the total loss with the circuit loss of the section is required.

In addition, since the compensation of the frequency characteristic is performed based on the signal cable loss level, the frequency characteristic changes when the level is adjusted, and conversely, when the frequency characteristic is adjusted, the frequency characteristic of the frequency characteristic compensating circuit unit is changed. Since the circuit loss changes and the output level changes, the adjustment must be made to find a convergence point such as level adjustment → frequency characteristic adjustment → level adjustment again → frequency characteristic adjustment again. It has the disadvantage that it does not.

SUMMARY OF THE INVENTION An object of the present invention is to provide a radio transmitting apparatus which can reduce the circuit loss of a frequency characteristic compensating circuit section and easily perform level adjustment and frequency characteristic adjustment irrespective of the length of a signal cable. Is to do.

[0008]

According to the present invention, there is provided a wireless transmission apparatus comprising: an indoor unit for outputting a first intermediate frequency modulated signal; and a first intermediate frequency modulated signal from the indoor unit via a signal cable. And a wireless transmission device including an outdoor unit that receives the first intermediate frequency modulation signal and converts the output signal into a radio frequency modulation signal. Changing the frequency of the first local oscillation frequency signal, mixing the modulation signal of the first intermediate frequency with the first local oscillation frequency signal, and converting the mixed signal into a second intermediate frequency modulation signal; To compensate for the loss experienced by the signal cable when receiving the first intermediate frequency modulated signal, the frequency of the signal cable relative to the second intermediate frequency modulated signal Using a filter of a second intermediate frequency having a loss of a frequency characteristic that is opposite to the characteristic, changing a second local oscillation frequency in accordance with a change in the frequency of the first local oscillation frequency signal, The second intermediate frequency modulation signal is mixed with the second local oscillation frequency signal to be converted into the radio frequency modulation signal.

In addition, a wireless transmission apparatus according to the present invention includes an indoor unit that outputs a first intermediate frequency modulated signal, and a radio frequency modulated signal that receives the first intermediate frequency modulated signal from the indoor unit. An outdoor unit for converting and outputting to a wireless transmission device in which the indoor unit and the outdoor unit are connected by a signal cable,
(A) changing the oscillation frequency according to the magnitude of the input level when receiving the modulated signal of the first intermediate frequency;
A first local frequency oscillation means for outputting an oscillation frequency signal as a first local oscillation frequency signal for converting the first intermediate frequency modulation signal into a second intermediate frequency modulation signal; First frequency conversion means for converting the first intermediate frequency modulated signal into a second intermediate frequency modulated signal using one local oscillation frequency signal, and (C) inverse frequency characteristic of the signal cable. Using a filter of a second intermediate frequency having a loss of the frequency characteristic to be a characteristic,
Loss compensating means for compensating for a loss received by the signal cable when the first intermediate frequency modulated signal is received with respect to the second intermediate frequency modulated signal;
(D) changing the oscillation frequency in response to the change in the frequency of the first local oscillation frequency signal,
(E) using the second local oscillation frequency signal to output a second local oscillation frequency signal as a second local oscillation frequency signal for converting the intermediate frequency modulation signal into the radio frequency modulation signal. Second frequency conversion means for converting the second intermediate frequency modulated signal into a radio frequency modulated signal.

[0010] Also, a radio transmitting apparatus according to the present invention comprises: an indoor unit for outputting a first intermediate frequency modulated signal; and a radio frequency modulated signal receiving the first intermediate frequency modulated signal from the indoor unit. An outdoor unit for converting and outputting to a wireless transmission device in which the indoor unit and the outdoor unit are connected by a signal cable,
The outdoor unit, (A) a first mixer that converts the first intermediate frequency modulated signal output from the indoor unit into a second intermediate frequency modulated signal, (B) the first intermediate frequency A first local oscillation circuit for outputting a first local oscillation signal to the first mixer for converting the modulation signal into a second intermediate frequency modulation signal, and (C) frequency characteristics of loss of the signal cable A filter having a loss of a frequency characteristic having an inverse characteristic with respect to and extracting the modulated signal of the second intermediate frequency from the output signal of the first mixer;
(D) a detection circuit for detecting the level of the second intermediate frequency modulation signal, and (E) a DC voltage corresponding to the detection level of the second intermediate frequency modulation signal output from the detection circuit. And the first local oscillator circuit generates an AP.
APC voltage generation circuit for supplying as C voltage signal, (F)
A second mixer that receives a second local oscillation signal and converts the second intermediate frequency modulation signal into a radio frequency modulation signal;
(G) the first local oscillation circuit outputs the first local oscillation circuit;
Receiving the local oscillation signal, and changing the frequency of the second local oscillation signal for converting the modulation signal of the second intermediate frequency into a modulation signal of a radio frequency in response to the change of the first local oscillation frequency. A second local oscillation circuit for changing the level of the second intermediate frequency modulated signal upon receiving the APC voltage signal. Accordingly, the first local oscillation frequency is changed.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the radio transmitting apparatus according to the present invention.

The radio transmission apparatus according to the present embodiment shown in FIG. 1 has a modulation signal 14 in an intermediate frequency band (hereinafter referred to as IF band).
And an outdoor unit 2 that receives an IF band modulated signal 15 from the indoor unit 1 via the signal cable 3 and converts it into a radio frequency band (hereinafter referred to as RF band) modulated signal 21 for output. It is composed of

The outdoor unit 2 is connected to the indoor unit 1
A mixer 5 for converting the frequency of the modulation signal 15 in the IF band received from the other to another frequency in the IF band, and a local oscillator for outputting a local oscillation signal 22 for converting the frequency of the modulation signal 15 to another frequency to the mixer 5 The oscillator circuit 4 has a loss having frequency characteristics opposite to the frequency characteristics of the loss of the signal cable 3, and the frequency of the modulation signal 15 and the frequency of the local oscillation signal 22 are selected from the output signals of the mixer 5. IF signal 6 for extracting a signal of the sum of the frequency as a modulation signal 17 in the IF band, an IF amplifier circuit 7 for amplifying the modulation signal 17 and outputting it as a modulation signal 18 in the IF band, and detecting the level of the modulation signal 18 The detection circuit 8 generates a DC voltage corresponding to the magnitude of the detection level of the modulation signal 18 output from the detection circuit 8, and sends the APC (Automat) to the local oscillation circuit 4.
ic Phase Control) voltage signal, an APC voltage generation circuit 9 that supplies a local oscillation signal 24, a mixer 11 that converts the frequency of the IF band modulation signal 18 into an RF band frequency, and an output from the local oscillation circuit 4. Upon receiving the local oscillation signal 22, the frequency of the local oscillation signal 24 for converting the frequency of the modulation signal 18 in the IF band to the frequency in the RF band is changed in accordance with the change in the frequency of the local oscillation signal 22, and the mixed signal is supplied to the mixer 11. A local oscillation circuit 10 for outputting, and an RF filter for extracting an RF band modulation signal 20 which is a signal having a sum of the frequency of the modulation signal 18 and the frequency of the local oscillation signal 24 from the signals output from the mixer 11. 12 and a modulated signal 21 which amplifies the modulated signal 20 in the RF band.
And an RF amplifying circuit 13 for outputting the same.

Next, the operation will be described.

In FIG. 1, when the modulated signal 14 in the IF band output from the indoor unit 1 is transmitted through the signal cable 3, the level of the IF signal is reduced due to the loss caused by the signal cable 3. Is received by the outdoor unit 2 as the modulated signal 15 of Mixer 5 is an indoor unit 1
Modulation signal 15 in the IF band received from
Is mixed with the local oscillation signal 22 supplied from the control unit 15 to output an IF band modulation signal 16 including a sum frequency signal and a difference frequency signal of the modulation signal 15 and the local oscillation signal 22. The modulated signal 16 output from the mixer 5 is
, The sum frequency signal in the IF band modulated signal 16 is taken out, and given by the signal cable 3 by the frequency characteristic of the IF filter 6 which is the inverse characteristic to the loss frequency characteristic of the signal cable 3. The frequency characteristics of the obtained loss are equalized and corrected, and the IF band modulated signal 1
7 is output to the IF amplifier circuit 7. IF amplifier circuit 7
Amplifies the modulated signal 17 and outputs it as a modulated signal 18 in the IF band. The level of the modulation signal 18 is detected by the detection circuit 8. The output of the detection circuit 8 is an APC voltage generation circuit 9
And a DC voltage whose voltage value changes in accordance with the level of the modulation signal 18 detected by the detection circuit 8 in the voltage generation circuit 9 is generated. This DC voltage is output from the APC voltage generation circuit 9 to the local oscillation circuit 4 for use as the APC voltage of the local oscillation circuit 4. Local oscillation circuit 4 receives APC voltage signal 23 and changes the oscillation frequency of local oscillation signal 22 in accordance with the level of modulation signal 18. Here, it is assumed that the oscillation frequency of the local oscillation signal 22 is increased when the level of the modulation signal 18 detected by the detection circuit 8 is large. That is, the frequency of the modulation signal 16 output from the mixer 5 is
When the level of the modulation signal 18 detected by the detection circuit 8 is high, the level becomes high. In this case, if the frequency characteristic of the IF filter 6 is set to the frequency characteristic shown in FIG. 2, when the signal cable is short, the loss of the signal cable is small, and the detection level becomes large. The frequency of the IF band signal becomes higher. As the frequency of the IF band signal increases, the loss in the IF signal band of the IF filter 6 increases and the primary slope of the frequency characteristic decreases. On the other hand, when the signal cable is long, the loss of the signal cable is large, so that the detection level is low, and the frequency of the IF band signal output from the mixer 5 is low. When the frequency of the IF band signal decreases, the loss in the IF signal band of the IF filter 6 decreases and the primary slope of the frequency characteristic increases.

When the signal cable is short, the modulated signal 1
Although the loss caused by the signal cable is small and the influence of the frequency characteristic is small, the modulated signal 1
2 becomes the higher frequency band in FIG. 2 when the IF signal 6 passes through the IF filter 6. Since the loss in the IF signal band is large and the primary slope of the frequency characteristic is small, the modulated signal 16 Can pass through the IF filter 6, thereby increasing the loss received by the modulation signal 16 and compensating the IF filter by equalization with a gently sloped frequency characteristic. On the other hand, when the signal cable is long, the loss given to the modulation signal 14 by the signal cable is large and the influence of the frequency characteristic is large. 2 becomes the lower frequency band of FIG. 2. Here, the loss in the IF signal band is small, and the primary slope of the frequency characteristic becomes large.
6 passes through the IF filter 6 so that the modulated signal 1
6 can be reduced, and compensation can be performed by equalization with the steep slope frequency characteristic of the IF filter. As described above, when the signal cable is short, the loss of the modulated signal 16 is increased, and
Compensation is performed by equalization with the frequency characteristics of the gradual slope of the IF filter to reduce the loss to the modulation signal 16 when the signal cable is long, and to compensate by equalization with the frequency characteristics of the steep slope of the IF filter. So that even if the length of the signal cable changes, I
The modulated signal 17 output from the F filter is not much affected by loss due to the signal cable 3 and frequency characteristics.

The mixer 11 receives the local oscillation signal 24 supplied from the local oscillation circuit 10 and receives the modulated signal 18 in the IF band.
Is converted into a signal of an RF band frequency. An RF signal which is a signal having the sum of the frequency of the modulation signal 18 and the frequency of the local oscillation signal 24 from among the signals output from the mixer 11.
The band modulation signal 20 is extracted by the RF filter 12. The RF band modulation signal 20 is amplified by the RF amplifier circuit 13 and output from the outdoor unit 2 as a modulation signal 21. Since the local oscillation circuit 10 receives the local oscillation signal 22 output from the local oscillation circuit 4 together with the mixer 5, the modulation signal 16 of the IF band output from the mixer 5
Is changed by the length of the signal cable,
The frequency of the local oscillation signal 24 supplied from the local oscillation circuit 10 also changes, and the frequency of the RF band modulation signal 21 output from the mixer 11 is controlled to be constant irrespective of the length of the signal cable. .

[0019]

As described above, according to the radio transmission apparatus of the present invention, the first local oscillation is controlled by the outdoor unit according to the level of the input level when the modulated signal of the first intermediate frequency is received. Changing the frequency of the frequency signal, mixing the first intermediate frequency modulation signal with the first local oscillation frequency signal, converting the first intermediate frequency modulation signal into a second intermediate frequency modulation signal, and receiving the first intermediate frequency modulation signal; In order to compensate for the loss received by the signal cable at the time, the second intermediate frequency filter has a frequency characteristic loss that is inverse to the frequency characteristic of the signal cable with respect to the second intermediate frequency modulated signal. And changing the second local oscillation frequency in accordance with the change in the frequency of the first local oscillation frequency signal, mixing the modulated signal of the second intermediate frequency with the second local oscillation frequency signal, By which is adapted to convert the modulated signal, the circuit loss of the frequency characteristic compensating circuit portion of the signal without cables related to the length of the signal cable requires less,
Only the gain for compensating for the loss of the signal cable is required, and the gain of the amplifier circuit can be reduced without the need to compensate for the circuit loss of the frequency characteristic compensation circuit section.

Further, since the adjustment of the loss of the signal cable and the adjustment of the frequency characteristic do not affect each other, there is an effect that the level adjustment and the adjustment of the frequency characteristic can be easily performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a wireless transmission device of the present invention.

FIG. 2 is an explanatory diagram showing characteristics of an intermediate frequency filter used in the wireless transmission device of FIG. 1;

FIG. 3 is a block diagram of a conventional wireless transmission device.

FIG. 4 is an explanatory diagram showing frequency characteristics of a signal cable used in the wireless transmission device of FIG. 3;

FIG. 5 is an explanatory diagram illustrating frequency characteristics of a loss compensation circuit used in the wireless transmission device of FIG. 3;

[Explanation of symbols]

 Reference Signs List 4 local oscillation circuit 5 mixer 6 IF filter 7 IF amplification circuit 8 detection circuit 9 APC voltage generation circuit 10 local oscillation circuit 11 mixer 12 RF filter 13 RF amplification circuit 22 local oscillation signal 23 APC voltage signal 24 local oscillation signal

Claims (3)

(57) [Claims] 1. An indoor unit for outputting a first intermediate frequency modulation signal, and receiving the first intermediate frequency modulation signal from the indoor unit via a signal cable and converting the first intermediate frequency modulation signal into a radio frequency modulation signal. In a wireless transmission device having an outdoor unit for outputting, the outdoor unit changes the frequency of a first local oscillation frequency signal in accordance with the magnitude of an input level when receiving the first intermediate frequency modulated signal. Changing, modulating the first intermediate frequency modulated signal with the first local oscillation frequency signal to convert it to a second intermediate frequency modulated signal, and receiving the first intermediate frequency modulated signal. In order to compensate for the loss received by the signal cable, the loss of the frequency characteristic that is inverse to the frequency characteristic of the signal cable with respect to the second intermediate frequency modulated signal. Using a second intermediate frequency filter having a second local oscillation frequency, changing the second local oscillation frequency in accordance with a change in the frequency of the first local oscillation frequency signal, and converting the second intermediate frequency modulation signal to the second intermediate oscillation frequency. 2. A radio transmitting apparatus, wherein the radio transmitting apparatus mixes the local oscillation frequency signal with the local oscillation frequency signal and converts the signal into a modulation signal of the radio frequency. 2. An indoor unit that outputs a first intermediate frequency modulation signal, and an outdoor unit that receives the first intermediate frequency modulation signal from the indoor unit, converts the first intermediate frequency modulation signal into a radio frequency modulation signal, and outputs the radio frequency modulation signal. Wherein the indoor unit and the outdoor unit are connected by a signal cable, and (A) according to the magnitude of the input level when the first intermediate frequency modulated signal is received. First local frequency oscillating means for changing an oscillating frequency and outputting the oscillating frequency signal as a first local oscillating frequency signal for converting the modulation signal of the first intermediate frequency into a modulation signal of a second intermediate frequency (B) first frequency conversion means for converting the first intermediate frequency modulation signal into a second intermediate frequency modulation signal using the first local oscillation frequency signal; The modulation of the first intermediate frequency is performed on the modulation signal of the second intermediate frequency by using a filter of the second intermediate frequency having a loss of a frequency characteristic that is opposite to the frequency characteristic of the signal cable. Loss compensating means for compensating for a loss received by the signal cable when a signal is received; (D) changing an oscillation frequency in response to a change in the frequency of the first local oscillation frequency signal; Second local frequency oscillating means for outputting a second intermediate frequency modulation signal as a second local oscillation frequency signal for converting the second intermediate frequency modulation signal into the radio frequency modulation signal;
(E) The second local oscillation frequency signal is used for the second local oscillation frequency signal.
A second frequency converting means for converting the intermediate frequency modulated signal into a radio frequency modulated signal. 3. An indoor unit that outputs a first intermediate frequency modulation signal, and an outdoor unit that receives the first intermediate frequency modulation signal from the indoor unit, converts the first intermediate frequency modulation signal into a radio frequency modulation signal, and outputs the radio frequency modulation signal. And wherein the indoor unit and the outdoor unit are connected by a signal cable, wherein the outdoor unit outputs (A) the modulated signal of the first intermediate frequency output from the indoor unit. A first conversion into a modulation signal of a second intermediate frequency;
(B) a first local oscillator circuit for outputting to the first mixer a first local oscillation signal for converting the first intermediate frequency modulation signal into a second intermediate frequency modulation signal (C) a filter having a frequency characteristic loss that is inverse to the frequency characteristic of the signal cable loss, and extracting the modulated signal of the second intermediate frequency from the output signal of the first mixer; D) a detection circuit for detecting the level of the second intermediate frequency modulation signal; and (E) a DC voltage corresponding to the detection level of the second intermediate frequency modulation signal output from the detection circuit. Occurs, said first
Supplies APC voltage signal to local oscillation circuit of APC
A voltage generating circuit, (F) a second mixer that receives the second local oscillation signal and converts the second intermediate frequency modulation signal into a radio frequency modulation signal, and (G) an output from the first local oscillation circuit. Receiving the first local oscillation signal, and converting the second intermediate frequency modulation signal into a radio frequency modulation signal in response to a change in the first local oscillation frequency. By changing the frequency of the oscillation signal, the second
A second local oscillation circuit that outputs the second local oscillation circuit to the mixer. The first local oscillation circuit receives the APC voltage signal, and according to the level of the second intermediate frequency modulation signal, A wireless transmission device for changing a first local oscillation frequency.