JP2002031657A - Circuit for generating receiving electric field intensity detection signal and mobile communication device with the generating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit for generating receiving electric field intensity detection signals which can improve a linearity of the receiving electric field intensity detection signals. SOLUTION: There are set an automatic gain control amplification circuit 30, a band pass active filter 40, a limiter amplification circuit 50 constituted of a plurality of stages, and a signal addition circuit 45 for adding outputs of signal detection circuits 21, 23, 51, 52 and 53. The linearity between an input signal intensity and an electric field intensity signal level is enlarged by obtaining the receiving electric field intensity detection signal at an output of the signal addition circuit 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for generating a received signal strength detection signal having good linearity, and to a mobile communication device having the circuit.

[0002]

2. Description of the Related Art As a receiving circuit used in a receiving apparatus such as a mobile communication device, there is a superheterodyne receiving circuit which converts a radio frequency signal in a radio frequency band into an intermediate frequency band signal and then demodulates the signal. In some cases, a band-pass filter for selecting only a necessary signal in an intermediate frequency band is realized by an active filter configured on a semiconductor integrated circuit to reduce the size of a device.

[0003] Although active filters are small and have relatively good characteristics, one of the disadvantages is that the dynamic range is narrower than passive filters due to the non-linearity and noise of the active elements. Sometimes. In order to remedy the drawback, an automatic gain control amplifier is provided before the active filter so that the signal level falls within the dynamic range of the active filter.

On the other hand, in the case of a limiter-amplifying receiving circuit, as a means for detecting the received electric field intensity, a signal corresponding to the amplitude is extracted from each stage of the multi-stage limiter amplifying circuit by extracting a signal in the intermediate frequency band. There is a method for obtaining an intensity signal. At that time, if the bandpass filter of the intermediate frequency band is realized by the active filter, it is necessary to add information of the gain control signal of the automatic gain control amplifier provided in the front stage of the active filter as the received electric field strength.

FIG. 3 shows an example of the configuration of such a receiving circuit. In FIG. 3, an automatic gain control amplifier circuit 30 whose gain is controlled so that the output of the intermediate frequency signal input from a terminal 35 does not exceed a predetermined value, and a band-pass active filter circuit
40, a limiter amplification circuit 50, a first signal detection circuit 51 for detecting a signal level of each amplification stage of the limiter amplification circuit,
The signal detection circuit 52, the third signal detection circuit 53, the gain control signal of the automatic gain control amplification circuit 30, and the output signals of the first signal detection circuit 51, the second signal detection circuit 52, and the third signal detection circuit 53 are added. And an adder circuit 45 for generating a reception electric field strength detection signal.

[0006] The automatic gain control circuit 30 is a variable gain amplifying circuit.
31; a double-wave detection circuit 32 for detecting an output signal of the variable gain amplification circuit 31; and an integration circuit 33 for integrating the output of the double-wave detection circuit 32 and outputting a gain control signal.

The limiter amplifier circuit 50 includes an amplifier circuit 55 at the first stage.
And a multi-stage amplifier circuit whose output stage is an amplifier circuit 56. The output of the limiter amplifier circuit 50 is taken out from the terminal 60 and output to, for example, a subsequent demodulation circuit.

Next, the operation of the receiving circuit will be described. The automatic gain control amplifier circuit 30 performs feedback control so that the amplitude of the input signal to the band-pass active filter circuit 40, which is an active circuit, does not exceed a certain value. That is, the variable gain amplifier is set so that the operation is linear with respect to the input signal amplitude.
The output signal of 31 is detected by a dual-wave detection circuit 32 and input to an integration circuit 33, and the output signal of the integration circuit 33 is used as a variable gain amplification circuit 31.
The gain is controlled. After unnecessary frequency components are reduced by the band-pass active filter circuit 40, the intermediate frequency signal is input to the limiter amplifier circuit 50 and output from the intermediate frequency signal output terminal 60.

On the other hand, the signal level intensities obtained by detecting the signals taken out from the respective input terminals of the respective amplifier circuits 55, 56 constituting the limiter amplifier circuit 50 by the first to third signal detection circuits 51, 52, 53 are shown. The gain control signal of the automatic gain control amplification circuit 30 and the gain control signal of the automatic gain control amplification circuit 30 are added by the addition circuit 45 to become a reception field strength detection signal, which is output from the output terminal 65.

[0010]

In the above prior art,
It was found that there was a problem in the linearity with respect to the amplitude of the received electric field strength detection signal. That is, the received electric field strength detection signal is the first
The signal is generated by adding the output signals of the third to third signal detection circuits 51, 52, and 53 and the gain control signal of the automatic gain control amplification circuit 30. FIG. 4 shows the received electric field strength characteristics of the conventional circuit shown in FIG. 3. FIG. 4 shows that the first to n-th detection circuits have the same output characteristics (the output gradient and the detection range are the same). In this case, the gain control signals have output characteristics different from those described above, and sufficient linearity is not obtained even if they are combined to obtain the received electric field strength characteristics.

The operating range of the automatic gain control amplifier circuit 30 is determined from the relationship between the input level range of the intermediate frequency signal to the receiving circuit and the linear input range of the band-pass active filter circuit 40. This is because the output characteristic of the automatic gain control amplifier circuit 30 is not necessarily determined so that the gain control signal is obtained with priority given to As a result, there is a problem that the linearity of the received electric field strength detection signal is limited at a relatively large input signal level as described above.

FIG. 5 shows an example of the detection circuit shown in FIG. In FIG. 5, for example, it is assumed that the configuration is that of the first signal detection circuit 51 of FIG. 3, and that the characteristics are those of the “first signal detection circuit 51” in FIG. At this time, the circuit configuration of the second signal detection circuits 2,..., N in FIG. 3 is the same as that of the first signal detection circuit 51, and the value of the reference voltage source 58 in the comparison circuit 57 is changed. Characteristics such as “detection circuit 2” and “detection circuit n” shown in FIG. 4 are obtained. In FIG. 5, a diode symbol 59 is shown.

In general, in a mobile communication device, the received electric field strength of a base station connected to a mobile station changes every moment. Therefore, the received electric field strength is monitored with an adjacent base station, and switching is performed. ing. However, the reception field strength of the planned station was not always stronger.

SUMMARY OF THE INVENTION The present invention is to solve the conventional technical problem, and a reception electric field intensity detection signal generation circuit capable of improving the linearity of a reception electric field intensity detection signal without using an AGC control signal; It is an object of the present invention to provide a mobile communication device using the generation circuit.

[0015]

According to the present invention, there is provided an automatic gain control amplifier circuit to which an intermediate frequency signal is applied, and a band-pass active circuit to which an output signal of the automatic gain control amplifier circuit is applied. A filter circuit, a multi-stage limiter amplifier circuit to which an output signal of the band-pass active filter circuit is applied, a signal detection circuit group for extracting and smoothing detection and smoothing input signals of each component stage of the limiter amplifier circuit; A signal addition circuit to which each output of the detection circuit group is applied, a reception electric field strength detection signal generation circuit obtaining a reception electric field strength detection signal as the signal addition circuit output,

An attenuating circuit for attenuating the intermediate frequency signal, a first signal detecting circuit for detecting and smoothing an output signal of the intermediate frequency signal, an amplifying circuit for amplifying a signal for the intermediate frequency signal, and a detecting circuit for detecting and smoothing the amplified output. 2 signal detection circuits, and connection lines for applying the outputs of the first and second signal detection circuits to the signal addition circuit.

Since the present invention is constructed as described above, when the detection signals from the respective signal detection circuits are combined by the adder circuit, the output of each signal detection circuit forms a part of a straight line. The linearity of the adder circuit output signal is extremely good.

[0018]

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

FIG. 1 shows the configuration of the intermediate frequency amplifier circuit of the receiver and its subsequent stage, and corresponds to FIG. That is, the same reference numerals as those in FIG. 3 denote the same circuits and elements. In FIG. 1, an intermediate frequency signal is input from a terminal 35, and is subjected to gain control and amplification through an automatic gain control amplifier circuit 30, a band-pass active filter circuit 40, and a limiter amplifier circuit 50, and is extracted from a terminal 60. To the second detection circuit and demodulation circuit.

A signal detection circuit group for extracting and smoothing detection and smoothing of an input signal of each component stage of the limiter amplifier circuit 50 is shown as 51, 52, 53 in FIG. The signal summing circuit is denoted by 45. In FIG. 1, an automatic gain control amplifier circuit 30 includes a variable gain amplifier circuit 31, a double wave detection circuit 32 for detecting an output signal of the variable gain amplifier circuit 31, and a gain by integrating the output of the double wave detection circuit 32. An integration circuit 33 that outputs a control signal.

An amplifier circuit 22 for amplifying the intermediate frequency signal applied to the automatic gain control amplifier circuit 30 and a second signal detecting circuit 23 for detecting and smoothing the signal are provided. It also includes an attenuation circuit 20 for attenuating the intermediate frequency signal and a first signal detection circuit 21 for detecting and smoothing. Circuit 2 above
Connection line 2 for transmitting signals from 1 and 23 to signal addition circuit 45
4 and 25 are provided. The reception electric field strength detection signal is obtained from the output terminal 65 of the signal addition circuit 45.

The operation of the illustrated circuit will be described below. In FIG. 1, the automatic gain control amplifier circuit 30 is arranged so that the amplitude of the input signal to the band-pass active filter circuit 40, which is an active circuit, does not exceed a predetermined value (that is, the automatic gain control amplifier circuit 30 operates linearly with respect to the input signal amplitude). ) Gain control feedback. Therefore, the output signal of the variable gain control amplifier 31 is detected by the double wave detection circuit 32 and input to the integration circuit 33. The output signal of the integration circuit 33 controls the gain of the variable gain amplifier 31 as described above.

After the unnecessary frequency components are reduced by the band-pass active filter 40, the intermediate frequency signal is input to the limiter amplifier circuit 50 and output from the terminal 60.

The signal extracted at the input side of the automatic gain control amplifying circuit 30 is processed and the first and second signal detecting circuits are processed.
Received signal level strength obtained from 21 and 23 and signal detection circuit group
The received signal level intensities obtained from 51, 52 and 53 are added in a signal adding circuit 45 and extracted from a terminal 65.

A description will now be given of the received electric field strength characteristics obtained with reference to FIG. As shown in FIG. 2, the output characteristics of each of the above-described signal detection circuits have the same output gradient and detection range, and all output signals are arranged side by side. The horizontal axis represents the input signal level in dB, and the vertical axis represents the received field strength signal level in linear. This uses a full-wave rectifier circuit that outputs a current having a pseudo relationship with a differential voltage input as each signal detection circuit. The operation start point with respect to the input level of each signal detection circuit is determined by the gain difference from the input point to each signal detection circuit.

Therefore, the overall output of the signal addition circuit in FIG. 2 tends to add the output of each signal detection circuit, and the adjustment of the bending position and the input signal level at which the output is obtained for the first time is completed. Therefore, the line indicating the output of the adder circuit is vast and straight.

By incorporating this electric field strength detection signal generation circuit into a receiver, the linearity of the received electric field strength of the receiver can be improved. By incorporating this signal generation circuit into a mobile station device of a wireless communication system, the linearity of the received electric field strength of the mobile station device can be improved. Further, by incorporating this signal generation circuit into the base station device of the wireless system, it is possible to improve the linearity of the received electric field strength of the mobile station device and the base station device.

Further, by incorporating this generating circuit into each of the receiving circuits of the mobile station apparatus and the base station apparatus of the radio communication system, the linearity of the received electric field strength of the mobile station apparatus and the base station apparatus is improved, and more accurate. The mobile station device can switch the connected base station device with respect to the reception electric field strength.

The case where the signal frequency is in the intermediate frequency band of the receiver has been described as an embodiment of the present invention. In this configuration, since the frequency of the signal to be handled does not change, the configuration of the signal detection circuit is simple, and adjustment to other circuits is relatively easy. In other words, including circuits that handle high frequencies and lower frequencies,
Although it is conceivable to configure a signal detection circuit, the present invention is superior in that the configuration is simple and easy to adjust.

[0030]

As is apparent from the above description, according to the present invention, an amplifier circuit for amplifying a signal in an amplifier circuit to which an intermediate frequency signal is applied without using an AGC control signal as in the prior art; Since two types of signal detection circuits and a signal addition circuit are provided, a reception circuit having good linearity can be obtained as a reception electric field intensity signal of the reception circuit, which is suitable as a circuit for generating an electric field intensity detection signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention;

FIG. 2 is a diagram showing operating characteristics of FIG. 1;

FIG. 3 is a diagram showing a configuration of a conventional receiving circuit.

FIG. 4 is a diagram showing operation characteristics of FIG. 3;

FIG. 5 is an enlarged view of a part of the circuit shown in FIG. 3;

[Explanation of symbols]

 20 Attenuation circuit 21 First signal detection circuit 22 Signal amplifier 23 Second signal detection circuit 24, 25 Connection line 30 Automatic gain control amplification circuit 31 Variable gain amplification circuit 32 Double-wave detection circuit 33 Integration circuit 40 Band-pass active filter circuit 45 Signal Adder circuit 50 Limiter amplifier circuits 51, 52, 53 First to n-th signal detection circuits 55, 56 Amplification circuits 57 Comparison circuits 58 Reference voltage source 59 Diode 60 Signal output terminal 65 Output terminal for reception electric field strength detection signal

Claims (3)

[Claims] 1. An automatic gain control amplifier circuit to which an intermediate frequency signal is applied, a band-pass active filter circuit to which an output signal of the automatic gain control amplifier circuit is applied, and an output signal of the band-pass active filter circuit to which an output signal is applied. A multi-stage limiter amplifier circuit, a signal detection circuit group for extracting and detecting and smoothing the input signal of each component stage of the limiter amplifier circuit, and a signal addition circuit to which each output of the signal detection circuit group is applied. A receiving electric field intensity detection signal generating circuit for obtaining a received electric field intensity detection signal as an output of the signal addition circuit, comprising: an attenuation circuit for attenuating a signal with respect to the intermediate frequency signal; and a first circuit for detecting and smoothing the output signal. A signal detection circuit; an amplification circuit for amplifying the signal with respect to the intermediate frequency signal; and a second signal detection circuit for detecting and smoothing the amplified output signal. Generating circuit of the receiving electric field strength detection signal and applying the No. detection circuit output to the signal adder circuit. 2. The signal detection circuit and the first and second signal detection circuits constituting the signal detection circuit group, each signal output is responsible for a specific portion of an input signal, and the combined output characteristic is linear. 2. The circuit according to claim 1, wherein signal inputs to each of the signal detection circuits are individually selected so as to satisfy the requirements. 3. A mobile communication device comprising a circuit for generating a received electric field strength detection signal according to claim 1.