JPH10327102A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the receiver to easily configure an identification function of a reception signal level in the case that the receiver adopts a direct demodulation system. SOLUTION: A low noise amplifier 2 amplifies a desired radio signal received by an antenna 1, a 1st mixer 3 applies guadrature demodulation to a base band (I/Q) signals and a demodulated I/Q signals are amplified by a gain control amplifier 10. Then an A/D converter 14 converts an output of the amplifier 10 into a digital signal and a table 15 is used by referring to the I/Q signals and a gain control digital signal to identify a reception level (absolute value) and a received signal strength indicator(RSSI) is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver having reception level identification means, and more particularly to a receiver of a direct demodulation system.

[0002]

2. Description of the Related Art In Japan, personal handy phone systems (hereinafter referred to as PHS) are now standardized as digital mobile radio communications, following automobiles / mobile phones.
RCRSTD-28).

FIG. 2 shows an example of a block diagram of a receiving system of a PHS receiver of the most commonly used system at present.
This will be described below. In the PHS, a system generally called a superheterodyne system is used.

In FIG. 2, 1 is an antenna, 2 is a low noise amplifier (hereinafter referred to as LNA), 3 is a first mixer, 4 is a filter (here, Band).
5 is a second mixer, 6 is a filter (here, a Band Pass Filter), 7 is an amplitude limiting circuit (hereinafter, referred to as a limiter), 8 is a data demodulator, 9 is a baseband signal processing circuit, 11 is a frequency conversion local oscillation signal generator, and 12 is a received signal level display circuit (Received
Signal Strength Indicator: hereinafter referred to as an RSSI circuit).

First, a desired radio frequency signal wave received by the antenna 1 (radio frequency signal: hereinafter referred to as an RF signal):
In the PHS, the 1.9 GHz band is amplified by the LNA 2 according to the standard, and then the intermediate frequency (hereinafter referred to as I
F signal: about 240 MHz is often used), an image frequency component generated at the time of frequency conversion by the filter 4 is removed, and the second mixer 3
After that, the signal is converted into a low frequency signal (often around 10.7 MHz), and then the image frequency component is removed by the filter 6.

[0006] The signal wave converted into a low-frequency signal is input to the limiter 7, amplified to a constant signal level required for the demodulator 8, and input to the demodulator 8. The demodulator 8 extracts digital value data by demodulation (delay detection) using a D flip-flop.

As described above, in the receiving system, QPSK generally used in a PHS transmitting system (not shown) is used.
Data is taken out without being converted into a modulation quadrature modulation signal (so-called I / Q signal). R attached to limiter 7
The received signal level is identified by the SSI circuit 12 and sent to the baseband signal processing circuit 9 to display the signal level.

Incidentally, a gain variable function (such as an attenuator) may be provided in the LNA (or before and after the LNA) to expand the dynamic range of the receiver. In this case, a control signal is output from the baseband signal processing circuit 9 as shown by a dotted line in FIG. IC for circuit used in receiving system
As an example of (LSI), for example, MGF7
134P (Mitsubishi Electric), Mixer 3 has M64820FP
(Mitsubishi Electric), the mixer 5 and the limiter 7 and the RSSI circuit 12 include AD608 (Analog Devices), and the data demodulator 8 includes M64170FP (Mitsubishi Electric).

A receiver using such a superheterodyne system is excellent in total performance, and a filter can be inserted before and after the mixer for suppressing interference waves and noise. It is possible to use a low power consumption circuit and inexpensive components (including a filter) which can be alleviated by the above, and are therefore most frequently used at present.

Further, in the receiver of this system, the RSSI circuit can be easily created (with little additional circuit) by utilizing the circuit characteristics of the limiter circuit 7, and the antenna input reception level is identified and displayed. It is possible.

Further, since the limiter circuit has a large amplification factor of, for example, 90 dB, if there is no problem in the S / N (signal-to-noise ratio) of the received signal, the signal level in the previous circuit can be reduced, and the nonlinearity can be reduced. It is possible to improve the receiving performance by suppressing third-order distortion or the like which is likely to be generated by a mixer having strong characteristics. Further, there is an advantage that it is not necessary to correct the variation of the amplification factor of the receiving system or adjust the signal level in the middle of the receiving system due to the dynamic range of the limiter.

However, there is an increasing demand for a portable receiver such as a PHS to have a low price, a low volume (small size), a light weight and a low power consumption. As a solution to this problem, circuits are being incorporated into ICs, which contributes to downsizing and weight reduction. However, there are many components that cannot be built in, such as filters that occupy a relatively large volume, leading to lower prices and downsizing. Therefore, reconsideration of the method itself is required.

As a solution to such a demand, IF
2 which is the baseband band directly without performing signal conversion
A so-called direct demodulation type PHS receiver that converts two quadrature modulated signals (I / Q signals) has been studied (for example, IEEE International Solid-State Circuits Conf.).
erence 1995).

FIG. 3 shows a basic block diagram of the quadrature demodulation method, which will be described below. Basically, it is the same as that in FIG. 2 except for the part related to the IF frequency, and thus the same functional blocks are given the same numbers.

In FIG. 3, 1 is an antenna, 2 is LN
A and 3 are first mixers (quadrature (I / Q) demodulators), 9 is a baseband signal processing circuit, 10 is a local oscillator signal generator for frequency conversion, 13 is an amplifier with a gain control function, and 14 is an analog digital ( A / D) converter.

First, a desired radio signal wave received by the antenna 1 is amplified by the LNA 2 and then directly quadrature demodulated by the first mixer 2 into a baseband (I / Q) signal. The demodulated I / Q signal is amplified by a gain control amplifier 13 to a level necessary for an A / D converter 14 at the subsequent stage, further digitally sampled by an A / D converter 14, and digitally processed by a baseband signal processing circuit 9. Is retrieved.

As described above, the demodulation used in the direct demodulation system operates differently from the receiver shown in the conventional example (FIG. 2), and extracts data by digital operation based on an I / Q signal sampled into a digital value. . By using the digital value, the data extracting function can be performed by the baseband signal processing circuit 9.

When a direct demodulation method is adopted in a PHS receiver, a received RF signal is directly converted into an I / Q signal which is a baseband band. In the state of the I / Q signal, not only phase information but also amplitude is used. Also, information is included, and if distortion occurs in the amplifier after quadrature demodulation, the error rate increases and the reception performance deteriorates. Therefore, a limiter circuit as shown in the conventional example cannot be inserted, and a linear amplifier is used.

As described above, in order to secure the dynamic range of the receiving system and amplify it to the signal level required for the A / D converter, to absorb the variation in the receiving system, Changes in radio field strength (so-called fading) and the accompanying TDMA (Time Domain)
In order to cope with the level change of the discontinuous signal wave in the operation of Maltiple Access (Time Division Multiple Access), an amplifier that can control the gain after the I / Q signal conversion in the mixer 3 is provided.

[0020]

As described above, since the direct demodulation method does not use the limiter circuit as in the conventional example, the RSSI circuit cannot be easily formed using the limiter circuit. For this reason, it is necessary to separately identify the reception level using some means.

As in the conventional example, RSSI is used in analog circuit.
If a circuit is to be provided separately, the simplest example of a circuit is the application of the limiter circuit shown in the conventional example. However, extra circuits (or ICs) increase only for that purpose, resulting in low power consumption. There is a problem that it goes against miniaturization and miniaturization. Further, for example, when a limiter circuit is applied, there is a concern about unstable operation such as oscillation of the circuit and interference with other circuits due to the high amplification factor.

An object of the present invention is to provide an analog circuit (IC) for identifying a reception level separately even when a direct demodulation method is employed for miniaturization and low power consumption. Identification and RSSI
An object of the present invention is to provide a receiver having a display function.

[0023]

According to a first aspect of the present invention, there is provided a receiver for amplifying a received radio frequency signal based on a gain control signal, and amplifying the received radio frequency signal with the first variable gain means. Means for directly demodulating the obtained radio frequency signal into a baseband signal, a second variable gain means for amplifying the baseband signal based on the gain control signal, and a signal amplified by the second variable gain means. Means for converting a baseband signal into a digital signal; means for associating the gain control signal and the digital signal with a reception level of the radio frequency signal; means for displaying the reception level; And means for changing the gain control signal to a gain control signal in an optimum gain control state. To so that.

In the gain control means necessary for the direct demodulation method, means for digitally identifying the reception level is provided, and the gain control signal is changed based on the identified reception level, so that it can be easily performed. RSSI display becomes possible.

In the receiver according to the second invention, the radio frequency signal is a burst signal used in TDMA communication.

In the receiver according to the third invention, the TDMA
The communication is based on the PHS standard.

[0027] In the receiver of the fourth invention, the gain control signal is a digital signal.

In the receiver of the fifth invention, a table is used as means for associating the gain control signal and the digital signal with the reception level of the radio frequency signal.

In the sixth invention, the table is constituted by a digital circuit.

In the receiver according to the seventh invention, a table is used as means for associating the reception level with the gain control signal in the optimum gain state at the reception level.

In the receiver according to the eighth aspect, the table is constituted by a digital circuit.

In the receiver according to the ninth aspect, the control means for changing the gain control signal to a gain control signal in an optimum gain control state is constituted by a digital circuit.

[0033]

FIG. 1 is a block diagram of a direct demodulation type PHS receiver according to an embodiment of the present invention.
This will be described below with reference to the drawings. Since it is basically the same as FIG. 3, the same functional blocks are given the same numbers.

In FIG. 3, 1 is an antenna, 2 is LN
A and 3 are first mixers (quadrature (I / Q) demodulators), 9 is a baseband signal processing circuit, 10 is a frequency conversion local oscillation signal generator, 13 is a gain control amplifier, and 14 is an A / D converter. ,
Reference numeral 15 denotes a digital value table for associating the gain control signal and the digital signal after A / D conversion with the reception level (absolute value) of the radio frequency signal wave.
Is a digital value table for associating the reception level with the gain control signal in the optimum gain state at the reception level, and 17 is a gain control signal controller. here,
The tables 15, 16 and the gain control signal control device 17 can be included in the baseband signal processing circuit 9 by being constituted by digital circuits and operating with digital values.

First, a desired radio signal wave received by the antenna 1 is amplified by the LNA 2 and then quadrature demodulated by the first mixer 3 into a baseband (I / Q) signal. The demodulated I / Q signal is amplified by a gain control amplifier 13 to a level necessary for an A / D converter 14 at the subsequent stage, further digitally sampled by an A / D converter 14, and digitally processed by a baseband signal processing circuit 9. Is retrieved.

On the other hand, the reception level is identified from the I / Q signal converted to a digital value by the A / D converter 14 and the gain control (digital) signal using the table 15 and transmitted to the baseband signal processing circuit 9. And RSSI is displayed. Applying the identified reception level to the table 16 for associating the reception level with the gain control signal in the optimum gain control state,
The control device 17 changes the current control signal to the gain control signal in the optimum gain control state.

Here, the radio frequency signal is a burst signal used in TDMA communication.

By using a radio frequency signal as a burst signal used in TDMA communication, a high-performance receiving function can be accurately exhibited.

The TDMA communication is based on the PHS standard.

By making the TDMA communication based on the PHS standard, the receiving function can be surely exhibited while ensuring the commonality.

As described above, according to the present invention, the reception level is easily identified by utilizing the gain control means required when the direct demodulation method is employed.

In this embodiment, the table 15,
The baseband signal processing circuit 9 and the control device 17 are constituted by digital circuits capable of reducing power consumption.
And the receiver can be reduced in size. further,
By using a digital circuit, stable operation without characteristic change due to aging is possible.

On the other hand, in this embodiment, in the next stage after the reception level has been identified, it is possible to immediately shift to the optimum gain control state at the reception level.
There is also an effect that the time required for convergence of gain control for a discontinuous signal in the A communication can be reduced.

[0044]

According to the first aspect of the present invention, by utilizing the gain control means necessary for the direct demodulation method, it is possible to reduce the power consumption and size of the reception level without adding an analog circuit. The configuration of the identification / display function becomes possible.

According to the second invention, the radio frequency signal is
By using a burst signal used in TDMA communication, a high-performance receiving function can be accurately exhibited.

According to the third aspect, TDMA communication is performed by P
By adopting the HS standard, the receiving function can be surely exhibited while securing commonality.

According to the fourth aspect, since the gain control signal is a digital signal, power consumption can be reduced and the size of the receiver can be reduced.

According to the fifth aspect, a table is used as means for associating the gain control signal and the digital signal with the reception level of the radio frequency signal. The reception level can be accurately matched by simple means.

According to the sixth aspect, since the table is constituted by a digital circuit, power consumption can be reduced and the size of the receiver can be reduced.

According to the seventh aspect, the table is used as a means for associating the reception level with the gain control signal in the optimum gain state at the reception level, so that the gain control signal in the optimum gain state at the reception level is obtained. Can be properly matched by simple means.

According to the eighth aspect, since the table is constituted by a digital circuit, power consumption can be reduced and the size of the receiver can be reduced.

According to the ninth aspect, the control means for changing the gain control signal to a gain control signal in an optimal gain control state is constituted by a digital circuit, thereby enabling low power consumption. The size of the receiver can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a conventional superheterodyne receiver.

FIG. 3 is a block diagram of a receiver of a direct demodulation system which is an improvement of the prior art.

[Explanation of symbols]

1 antenna, 2 LNA, 3rd mixer (or quadrature (I / Q) demodulator), 4 filters, 5th mixer, 6 filters, 7 limiter, 8 data demodulator,
9 baseband signal processing circuit, 10 local oscillator signal generator for frequency conversion, 11 local oscillator signal generator for frequency conversion, 1
2 RSSI display circuit, 13 gain control amplifier, 14
Analog-to-digital (A / D) converter, 15 digital value table for associating the gain control signal and the digital signal after A / D conversion with the reception level (absolute value) of the radio frequency signal wave, 16 A digital value table for associating a reception level with a gain control signal in an optimum gain state at the reception level, 17 a gain control (digital) signal control device.

Claims (9)

[Claims] 1. A first variable gain means for amplifying a received radio frequency signal based on a gain control signal, and the radio frequency signal amplified by the first variable gain means is directly demodulated into a baseband signal. Means, second variable gain means for amplifying the baseband signal based on the gain control signal, means for converting the baseband signal amplified by the second variable gain means into a digital signal, and the gain Means for associating a control signal and the digital signal with a reception level of the radio frequency signal, means for displaying the reception level, and means for associating the reception level with a gain control signal in an optimum gain state at the reception level. Control means for changing the gain control signal to a gain control signal in an optimum gain control state. 2. The receiver according to claim 1, wherein the radio frequency signal is a burst signal used in TDMA communication. 3. The receiver according to claim 2, wherein the TDMA communication is based on the PHS standard. 4. The receiver according to claim 1, wherein the gain control signal is a digital signal. 5. The receiver according to claim 1, wherein a table is used as means for associating the gain control signal and the digital signal with the reception level of the radio frequency signal. 6. The receiver according to claim 5, wherein the table is constituted by a digital circuit. 7. The receiver according to claim 1, wherein a table is used as means for associating the reception level with the gain control signal in the optimum gain state at the reception level. 8. The receiver according to claim 7, wherein the table is constituted by a digital circuit. 9. The receiver according to claim 1, wherein the control means for changing the gain control signal to a gain control signal in an optimum gain control state comprises a digital circuit.