JPH0955710A - Measuring instrument for received signal strength - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect received signal strength over a wide dynamic range with good linearlity. SOLUTION: Through a signal branching circuit 3, high frequency signal (a) having passed through an antenna 1 and a filter part 2 is branched into high-frequency signals b1, b2, and b3 which have levels suppressed in a plurality of stages. A switch 4 selects one of the high frequency signals b1, b2, and b3 and the selected high frequency signal (d) is amplified by an amplification part 5; and a reception part 6 measures the level of this amplified high frequency signal (e) to generate an RSSI voltage (f). A switching control part 7 generates a control signal (g) for making the switch 4 select the high frequency signal (b) which is one stage lower in level when detecting an excessively high RSSI voltage (f) and also generates a control signal (g) for making the switch select the high-frequency signal (b) which is one stage higher in level when detecting an excessively low RSSI voltage (f). An electric field intensity detection part 8 adds voltages corresponding to the RSSI voltage (f) and control signal (g) to generate an accurate RSSI voltage (h) with good linearlity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving field strength measuring apparatus suitable for use in mobile communication devices and the like, and more particularly to a receiving field strength measuring apparatus requiring a wide dynamic range.

[0002]

2. Description of the Related Art A conventional reception electric field strength detection circuit for a mobile communication device is disclosed in Japanese Patent Application Laid-Open No. 5-63624 (Title of Invention:
Cellular receivers). This receiving electric field strength measuring device is shown as a part of a cellular receiver, and after a receiving input wave is amplified by a high frequency amplifier in order to improve receiving sensitivity, a frequency-converted signal is converted into a voltage, The electric field strength of the received input wave is monitored based on this voltage. In this cellular receiver, when the electric field strength of the received input wave is increased, in order to reduce the intermodulation distortion of the received signal by the high-frequency amplifier, the detection result of the electric field strength of the monitored received input wave is reduced. The signal is bypassed or the gain is controlled based on the above-mentioned high frequency amplifier.

[0003]

The electric field strength detection of the received input wave by the above-mentioned received electric field strength detection circuit only needs to detect whether or not the electric field strength is above a certain level. No consideration was given to linearity or accuracy.

However, when the detected received electric field strength is used for handoff switching of a cellular automobile telephone system, it is necessary to accurately detect the received electric field strength. In this type of receiving electric field intensity measuring device, it is necessary to detect the receiving electric field intensity over a wide dynamic range with good linearity.

[0005]

SUMMARY OF THE INVENTION A receiving electric field strength measuring apparatus according to the present invention comprises: a signal branching circuit for branching a high frequency signal band-limited to a predetermined band into a plurality of high frequency signals in which the level is reduced stepwise; A switch for selecting one of the selected high frequency signals according to a control signal, and a first RSSI for measuring a level of the selected high frequency signal.
A receiving unit that generates a voltage; and a control signal that responds to the first RSSI voltage and that selects the high-frequency signal at a next lower level when detecting an excessive voltage of the first RSSI voltage, A switching control unit that generates the control signal for selecting the high-frequency signal at a next higher level when detecting an undervoltage of the RSSI voltage of the first RSSI,
An electric field intensity detector for generating a second RSSI voltage in response to the I voltage and the control signal.

In the reception electric field intensity measuring device, the electric field intensity detecting section may add the first RSSI voltage and a voltage corresponding to a suppression level of the high frequency signal according to the control signal to generate the second RSSI voltage. Can be adopted.

In the above-mentioned receiving electric field strength measuring apparatus, the signal branching circuit is constituted by a strip line and generates the highest level of the high-frequency signal among the branched lines, and is coupled to the main line at a high frequency. Then, at least one sub-circuit for generating the high-frequency signal different from the main line can be provided.

[0008]

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

FIG. 1 is a block diagram showing an embodiment of a receiving electric field strength measuring apparatus according to the present invention.

This receiving field strength measuring device is used as a part of a radio base station of a digital mobile communication system such as a cellular type mobile telephone system. The antenna 1 is 800 MHz from the mobile terminal of this digital mobile communication system.
The high frequency signal in the z band is received and supplied to the filter unit 2.
The high frequency signal may be in the 1.5 GHz band. The filter unit 2 is a predetermined band that may receive the supplied high frequency signal from the mobile terminal, for example, 15M
A high-frequency signal a is generated by band limiting to about Hz. The high-frequency signal a branches into a plurality of high-frequency signals b1, b2, and b3 whose levels are suppressed step by step by the signal branch circuit 3. For example, the high frequency signal b2 is suppressed by 60 dB from the high frequency signal a, the high frequency signal b3 is suppressed by 30 dB from the high frequency signal a, and the high frequency signal b is suppressed.
1 receives 0 dB level suppression from the high frequency signal a, that is, there is almost no level suppression.

Here, the signal branching circuit 3 is a directional coupler constituted by a coupled strip line including a main line 31 and sub-lines 32 and 33. The main line 31, the sub-lines 32 and 33 are high-frequency signals b1 and b, respectively.
2 and b3, respectively. Main track 31 and sub track 3
2 and the main line 31 and the sub line 33 are connected to each other at a high frequency. The sub-lines 32 and 33 need only be circuits that are coupled to the main line 31 at high frequencies, and need not necessarily be striplines.

The high frequency signals b1, b2 and b3 are supplied to switching terminals 41, 42 and 43 of the switch 4, respectively. The switch 4 connects the switching terminal (any one of 41, 42 and 43) and the common terminal 44 in accordance with the control signal g supplied from the switching control unit 7, and outputs any one of the high frequency signals b1, b2 and b3. Select and amplify section 5
To supply. The amplifying unit 5 outputs the selected high frequency signal (b
1, b2 and b3) and supplies the amplified high frequency signal e to the receiving unit 6. The receiver 6 measures the level of the high frequency signal e and generates an RSSI voltage f. Here, the receiving unit 6 converts the high-frequency signal e to Log-L
a transistor amplifier that amplifies the signal with inear characteristics, and linearly detects the amplified high-frequency signal to obtain an RSSI voltage f
And a linear detector that generates Log-Linear of RSSI voltage f over a wide dynamic range
To ensure the linearity of the characteristics, a transistor amplifier having a high linearity to a high level is required. This not only complicates the configuration of the receiving unit 6, but also causes a problem that the price of the electric field strength detecting device increases.

The RSSI voltage f is supplied to the switching control unit 7. When detecting an excessive voltage of the RSSI voltage f, the switching control unit 7 generates a control signal g for selecting a high-frequency signal having a level one level lower. For example, when the control signal g when the excessive voltage is detected selects the high frequency signal b1, the control signal g is switched to the control signal g for selecting the high frequency signal b3, and the control signal g when the excessive voltage is detected. Switches to the control signal g for selecting the high frequency signal b2 when the high frequency signal b3 is selected. Switching control unit 7
When detecting an undervoltage of the RSSI voltage f, a control signal g for selecting a high-frequency signal of one level higher is generated. For example, the control signal g when the undervoltage is detected
Is switched to the control signal g for selecting the high-frequency signal b3 when the high-frequency signal b2 is selected, and when the control signal g when the undervoltage is detected selects the high-frequency signal b3. The control is switched to the control signal g for selecting the high frequency signal b1.

The RSSI voltage f and the control signal g are also supplied to the electric field strength detector 8. The electric field strength detection unit is RSS
A log-linear RSSI voltage h is generated in the high frequency signal a in response to the I voltage f and the control signal f. That is, the electric field strength detection unit 8 generates the RSSI voltage h by adding the RSSI voltage f and the voltage according to the control signal g, that is, the voltages corresponding to the respective suppression levels of the high frequency signals b1, b2, and b3. I do.

FIG. 2 is a diagram showing the relationship between the level of the high frequency signal a and the RSSI voltages f and h in the embodiment of FIG.

When the high-frequency signal a input to the signal branch circuit 3 is a weak electric field (from 0 dB to +30 dB; hereinafter, the level of the high-frequency signal is a relative value), the switch 4 is controlled by the signal branch circuit 3. The high frequency signal b1 without level suppression is supplied to the amplifier 5 as the high frequency signal d. At this time, the receiving unit 6 transmits the RSS from A (V) to B (V).
The switching controller 7 supplies the I voltage f to the electric field strength detector 8 with the control signal g of A (V). The electric field strength detector 8 adds the above-mentioned RSSI voltage f and the control signal g to generate an RSSI voltage h. Since the RSSI voltage f is a voltage to which A (V) has already been added, the RSSI voltage h is R
It is equal to the SSI voltage f. Note that the high frequency signal a is excessive,
That is, when the high frequency signal e becomes excessive, the RSSI voltage f
Is suppressed from deviating downward from the Log-Linear characteristic, as shown above Y (V) of the RSSI voltage f in FIG.

Next, when the high frequency signal a changes from a weak electric field to a medium electric field (from +30 dB to +60 dB) and the RSSI voltage f reaches Y (V), which is a limit of good linearity, the switching control unit 7 Is detected, and it is determined that the high frequency signal a is excessive, and the control signal g is changed from A (V) to B (V). Then, the switch 4 supplies the high frequency signal b3 whose level suppression by the signal branching circuit 3 is 30 dB to the amplifier 5 as the high frequency signal d. As a result, the RSSI voltage f from the receiving unit 6 changes to X (V). The electric field intensity detector 8 adds the control signal g of B (V) corresponding to the level suppression of 30 dB and the RSSI voltage f of X (V) to obtain Y (V).
Of the RSSI voltage h. As described above, when the high frequency signal a is a medium electric field, the electric field strength detection unit 8 calculates the RSSI voltage h obtained by adding the control signal g of B (V) and the RSSI voltage f except for the vicinity of the electric field transition point. Occurs.

Further, when the high frequency signal a changes from a medium electric field to a strong electric field (from +60 dB to +90 dB) and the RSSI voltage f changes from B (V) to Y (V), the switching control unit 7 detects this. , The control signal g is changed from B (V) to C (V) by determining that the high frequency signal a is excessive. Then, the switch 4 controls the signal branching circuit 3 to suppress the level by 6
The high-frequency signal b2 of 0 dB is supplied to the amplifier 5 as the high-frequency signal d. As a result, the RSS from the receiving unit 6
The I voltage f changes to X (V). The electric field strength detector 8 controls the C (V) control signals g and X corresponding to the level suppression of 60 dB.
(V) RSSI voltage f and Z (V) RSSI
This produces an I voltage h. As described above, when the high-frequency signal a is a strong electric field, the electric field intensity detection unit 8 adds the control signal g of C (V) and the RSSI voltage f to the maximum D (V ) Are generated. Therefore, the receiving electric field intensity measuring device can detect the receiving electric field intensity with high linearity over a dynamic range in which the high frequency signal a is three times as wide as the receiving unit 8.

On the other hand, when the level of the high frequency signal a decreases, the control signal g operates in the opposite manner as described above. For example, when the high-frequency signal a changes from a strong electric field to a medium electric field and the RSSI voltage f reaches A (V), the switching control unit 7 detects this and determines that the high-frequency signal a is too small to perform control. The signal g is changed from C (V) to B (V). Then, the switch 4 controls the level of the signal branching circuit 3 by 3
The high-frequency signal b3 of 0 dB is supplied to the amplifier 5 as the high-frequency signal d. As a result, the RSS from the receiving unit 6
The I voltage f changes to B (V). The electric field strength detector 8 controls the control signals g and B of B (V) corresponding to the level suppression of 30 dB.
(V) RSSI voltage f and C (V) RSSI
This produces an I voltage h. As described above, when the high frequency signal a is a medium electric field, the electric field strength detection unit 8 calculates the RSSI voltage h obtained by adding the control signal g of B (V) and the RSSI voltage f except for the vicinity of the electric field transition point. Occurs.

When the high-frequency signal a changes from a medium electric field to a weak electric field and the RSSI voltage f becomes A (V), the switching control unit 7 detects this and determines that the high-frequency signal a is too small. Control signal g is changed from B (V) to A (V). Then, the switch 4 supplies the high frequency signal b1 without the level suppression by the signal branching circuit 3 to the amplifier 5 as the high frequency signal d. As a result, RSSI from the receiving unit 6
The voltage f changes to B (V). The electric field strength detector 8 controls the A (V) control signals g and B corresponding to the level suppression of 0 dB.
(V) RSSI voltage f and B (V) RSSI
This produces an I voltage h.

In the present embodiment, the suppression level of the high frequency signal a by the signal branching circuit 3 is set to three levels.
It is determined by the dynamic range of the linear amplifier.

[0022]

As described above, the present invention provides a signal branching circuit for branching a high-frequency signal band-limited to a predetermined band into a plurality of high-frequency signals suppressed to different levels, A switch for selecting one of the signals in accordance with a control signal, a receiving unit for measuring a level of the selected high-frequency signal to generate a first RSSI voltage, and a responsive to the first RSSI voltage for receiving the first RSSI voltage; When the overvoltage of the RSSI voltage is detected, the control signal for selecting the high-frequency signal at the next lower level is generated, and when the undervoltage of the first RSSI voltage is detected, the higher-frequency signal at the next higher level is selected. A switching control unit for generating the control signal, and a field strength detecting unit for generating a second RSSI voltage in response to the first RSSI voltage and the control signal. Because, an effect that can be detected and accurately yet linearity received field strength over a wide dynamic range. Further, according to the present invention, since an amplifier having a narrow dynamic range can be used in the receiving section, the configuration is simple and the economy is excellent.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a receiving electric field strength measuring device according to the present invention.

FIG. 2 is a diagram showing a relationship between a level of a high frequency signal a and RSSI voltages f and h in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Filter part 3 Signal branch circuit 31 Main line 32, 33 Branch line 4 Switch 41-43 Switching terminal 44 Common terminal 5 Amplifying part 6 Receiving part 7 Switching control part 8 Electric field intensity detecting part

Claims (3)

[Claims] 1. A signal branching circuit for branching a high-frequency signal band-limited to a predetermined band into a plurality of high-frequency signals suppressed to different levels, and selecting one of the branched high-frequency signals according to a control signal. And a switch for measuring the level of the selected high frequency signal to provide a first R
A receiving unit that generates an SSI voltage; and a control signal that is responsive to the first RSSI voltage and that selects the high-frequency signal at a next lower level when an overvoltage of the first RSSI voltage is detected. A switching control unit that generates the control signal for selecting the high-frequency signal at a next higher level when detecting an undervoltage of one RSSI voltage; and a second RS in response to the first RSSI voltage and the control signal.
An electric field intensity measuring device comprising: an electric field intensity detecting section for generating an SI voltage. 2. The method according to claim 1, wherein the electric field intensity detection unit is configured to output the first RS
2. The reception field intensity measuring device according to claim 1, wherein the second RSSI voltage is generated by adding an SI voltage and a voltage corresponding to a suppression level of the high frequency signal according to the control signal. 3. The main line, wherein the signal branching circuit is formed of a strip line and produces the highest level of the high-frequency signal among the branched lines, and a main line which is high-frequency coupled to the main line and separate from the main line. 3. An apparatus according to claim 2, further comprising at least one sub-circuit for generating said high frequency signal.