JPH03218136A - Received signal amplifier - Google Patents

Abstract

PURPOSE:To detect a received signal with high accuracy at a detector and to make the estimation of a propagation path and equalization of the detected signal accurately without losing the amplitude information of the received signal affected by frequency selective fading, by amplifying the signal at a prescribed gain based on a gain control signal obtained from a level of one preceding burst signal. CONSTITUTION:The amplifier consists of an amplifier 2 whose gain is decided by an externally inputted gain control signal 4 and amplifying the received signal and a gain controller 3 outputting the gain control signal 4 based on a level of the received signal to control the gain of the amplifier with respect to the burst signal received based on a burst signal level of one preceding burst signal 1. Thus, the amplitude information of the received signal affected by frequency selective fading is not lost and the propagation path is estimated and the detected signal is equalized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a received signal amplifier, particularly in a TDMA communication system, which receives a burst signal, detects it, and uses an equalizer to estimate the propagation path and convert the detected signal, etc. The present invention relates to a received signal amplifier for performing conversion.

[Conventional technology]

Conventionally, this type of received signal amplifier inputs the output of the burst signal l amplified by the amplifier 2 to a detection circuit 3', as shown in FIG. 4, and outputs a gain control signal from the detection circuit 3'. 4' is input to the control terminal of the amplifier 2, that is, feedback is applied. As a result, when amplifying a received signal whose level fluctuates due to relief aging or shadowing, the gain of the amplifier 2 can be controlled so that the amplified output is at a level that allows accurate detection. can.

Note that in a receiver in which the equalizer does not perform propagation path estimation and equalization of the detected signal, the received signal amplifier may be a limiter.

[Problem to be solved by the invention]

In the conventional received signal amplifier described above, when it is applied to a mobile digital transmission system with a low transmission speed, the amount of delay due to multiple propagation paths is small compared to the transmission speed (~several tens of Kbps). Level fluctuations can be considered to be caused only by relay aging and shadowing, and deterioration of reception characteristics can be prevented by performing level correction using a reception signal amplifier.

However, when the transmission speed increases and the delay due to multiple propagation paths becomes so large that it cannot be ignored compared to the transmission speed, frequency selective fading occurs, and it is necessary to correct the level fluctuations due to this. However, correct demodulation will no longer be possible.

Therefore, when performing high-speed digital mobile communication in burst mode, in order to overcome selective fading due to multipath, a training signal during transmission path estimation is included in the burst, and this is used to improve transmission on the receiving side. A method is used to obtain the correct output by estimating the path characteristics and equalizing the received signal.

In this case, estimation of the transmission path and equalization of the received signal are performed on the premise that the transmission path characteristics do not change within one burst. In addition, to demodulate a received signal that is not affected by selective fading, it is sufficient to use only the phase information of the received signal, but it is also possible to use the received signal that has been affected by selective fading to perform transmission path estimation and reception. To perform signal equalization, amplitude information of the received signal must also be used.

For the above reasons, it is necessary that the circuit characteristics from the detection of the received signal to the acquisition of the baseband signal during one burst are such that the gain does not vary and that the circuit characteristics are linear.

If a received signal amplifier is used in which the gain changes follow high-speed level fluctuations such as selective fading, accurate demodulation becomes impossible because the amplitude information of the signal is lost. On the other hand, if a received signal amplifier is used in which the gain changes follow only slow level fluctuations, the amplitude information of the signal is not lost, but the received signal affected by selective fading may fluctuate over several bits or become unreliable. The gain of the received signal amplifier cannot be determined unless a sufficient length of the received signal is observed.

In other words, a received signal amplifier in which the gain is determined by feeding back the output level of the amplifier cannot be applied to the above-described method.

An object of the present invention is to provide a received signal amplifier that can correctly estimate a propagation path and equalize a detected signal.

[Means to solve the problem]

The received signal amplifier of the present invention includes an amplifier whose gain is determined by a gain control signal input from the outside and amplifies the received signal, and a gain controller that outputs the gain control signal based on the level of the received signal. The gain of the amplifier for the received burst signal is controlled based on the level of the burst signal immediately before the received burst signal.

The gain controller includes a level measuring device that measures the level of the received burst signal, and a storage device that stores a gain control signal obtained based on the measured level,
When a received burst signal is amplified, the gain control signal corresponding to the previous burst signal is output from the memory to the amplifier.

Further, the amplifier is composed of a linear amplifier.

[Effect]

According to the present invention, when one burst signal is amplified, the amplification is performed with a constant gain based on the gain control signal obtained from the level of the previous burst signal, so that the signal is not affected by frequency selective fading. It is possible to estimate the propagation path and equalize the detected signal without losing the amplitude information of the received signal.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of a received signal amplifier according to the present invention, and shows an example in which the present invention is applied to four-channel multiplexed TDMA communication.

In the figure, an amplifier 2 is constituted by a linear amplifier, and amplifies an input burst signal 1. Also, the gain controller 3
inputs burst signal 1 and measures the level of this burst signal 1. Then, based on this measured level, a gain control signal 4 is outputted to control the gain of the amplifier 2 when amplifying the next burst signal of the same channel.

At this time, the amplifier 2 amplifies the burst signal 1 with a constant gain while receiving the burst signal 1.

An example of the gain controller 3 is shown in FIG. This gain controller 3 measures the level of the input burst signal 1,
A level measuring device 5 for converting into a gain control signal, switchers 6 and 7 for switching signals, and memories 8 and 84 assigned to each of the first to fourth channels and temporarily storing each gain control signal. It consists of

While receiving the burst signal of the first channel, the level of the input burst signal 1 is measured by the level measuring device 5, and at the same time as the reception of the burst signal 1 is finished, the switch 6 is switched to the first channel. Memory device 8 assigned to 1 channel
1 and sends a gain control signal corresponding to the measured level to the switched memory 81 and stores it. At the same time, the switch 7 is switched to the memory 8l assigned to the first channel, and the previous gain control signal 4 stored there is outputted to the amplifier 2.

Thereafter, similar operations are performed when receiving burst signals of each of the second to fourth channels. However, when receiving a burst signal of an unused channel, the gain control signal is set to zero.

The amplification operation in this configuration will be explained. FIG. 3(a) shows the frame structure of burst signal 1, in which time slots S+, Ss, S9 are the first channels, Sz, Sb
, Sho is the second channel, S:l, S7 is the third channel, S4. It is assumed that S8 is assigned to the fourth channel. Further, it is assumed here that the second channel is not used.

Now, the level of the burst signal 1 having a signal waveform as shown in FIG.
).

Based on this measured level, each channel generates a gain control signal as shown in FIG. 4(d), and stores this in each of the memories 81 to 84.

When amplifying the next burst signal in each channel, the gain of the amplifier 2 is adjusted based on the gain control signal 4 obtained from the previous burst signal of each channel stored in the memories 81 to 84, respectively. control each. This makes it possible to obtain a signal with a substantially constant output level from the amplifier 2 in each channel, as shown in FIG. 2(e).

For example, the level L, of the burst signal 1 in the time slot S, is measured by the gain controller 3, and the level LAS
get. Based on this level LAS, the level Lgs of the gain control signal 4 is output from the time slot S9, and the level L of the burst signal 1 of the time slot S is outputted from the amplifier 2.
The signal is amplified to the output level LC9.

Note that the allocated time slot S. of the unused second channel. , S-. ,S. . Then gain control signal 4
Let be zero.

As a result, the gain remains constant while the burst signal is being received, and by linearly amplifying this, the amplitude information of the received signal affected by frequency selective fading is not lost, and the detector can accurately After detection, it becomes possible to correctly estimate the propagation path and equalize the detected signal using an equalizer.

Note that when the present invention is used in mobile communication, the frequency of fading that occurs when a mobile station moves is several tens of H2.
Therefore, in a system where the burst repetition frequency is several hundred H2, the repetition of the burst is faster than the fluctuation of the electric field, so there is almost no extreme difference in the reception level between bursts. .

〔Effect of the invention〕

As explained above, in the present invention, when one burst signal is amplified, the amplification is performed with a constant gain based on the gain control signal obtained from the level of the previous burst signal, so that frequency selective fading is avoided. Since the amplitude information of the affected received signal is not lost, there is an effect that the detector can accurately detect the wave and the equalizer can correctly estimate the propagation path and equalize the detected signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the received signal amplifier of the present invention, FIG. 2 is a block diagram of the gain controller of FIG. 1, and FIGS. FIG. 4 is a block diagram of a conventional received signal amplifier. DESCRIPTION OF SYMBOLS 1... Burst signal, 2... Amplifier, 3... Gain controller, 4... Gain control signal, 5... Level measuring device, 6, 7... Switching device, 8I-8, ...Memory device, S.
-S. . ...time slot.

Claims (1)

[Claims] 1. Consisting of an amplifier whose gain is determined by a gain control signal input from the outside and amplifies a received signal, and a gain controller that outputs the gain control signal based on the level of the received signal. A received signal amplifier, characterized in that the gain of the amplifier for the received burst signal is controlled based on the level of the burst signal immediately before the received burst signal. 2. The gain controller includes a level measuring device that measures the level of the received burst signal and a storage device that stores a gain control signal obtained based on the measured level, and when amplifying the received burst signal, 2. The received signal amplifier according to claim 1, wherein the gain control signal corresponding to the previous burst signal is output from the memory to the amplifier. 3. The received signal amplifier according to claim 1 or 2, wherein the amplifier is constituted by a linear amplifier.