JPH05130055A - Reception signal power alarm circuit - Google Patents

Abstract

PURPOSE:To use a band pass filter required for eliminating a power component of an adjacent carrier with a filter of one center frequency when a decrease in a reception input signal level is detected for each carrier and an alarm output is sent in a radio receiver of the multi-carrier transmission system. CONSTITUTION:Frequency converters 10a, 10b, 10c to convert a frequency of a reception signal for each carrier into a same frequency fDET after branching and a power synthesizer 13 used to synthesize the frequency-converted signals are provided to the system and it is provided with a timing signal generating circuit 15 generating a control voltage to produce each carrier in time division sequentially with respect to the vicinity of the frequency fDET by controlling the conversion frequency and with data latch circuits 14a, 14b, 14 collecting and latching an alarm output corresponding to each carrier based on the alarm output signal outputted in time division synchronously with the carrier changeover.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power alarm circuit for received signals, and more particularly to an intermediate frequency (IF) section of a microwave digital radio receiver which employs a heterodyne reception system in multicarrier transmission.

[0002]

2. Description of the Related Art FIG. 2 shows a part of a block diagram of a receiving apparatus implementing a conventional received signal power warning circuit. Especially Figure 2
Is the case of a wireless reception device when transmission is performed by a three-carrier multicarrier method.

Here, the multi-carrier transmission method means that, when transmitting a baseband signal (modulated signal) having a certain transmission capacity, a plurality of baseband signals obtained by dividing the transmission capacity into modulation signals are used as different intermediate frequencies. Obi (I
This is a method in which the carrier frequency of F) is independently modulated into a plurality of modulated waves, which are collectively combined and frequency-converted into a radio frequency band (RF) for transmission.

The received input signal received from the antenna is frequency-converted into the intermediate frequency band, and then distributed by the power distributor 1 by each modulated wave as shown as the input signal in FIG.

The signals divided into three are three demultiplexing band pass filters 2a, which have different center frequencies for each modulated wave.
2b and 2c are input and the respective modulated wave components are extracted.

However, since the characteristic of the demultiplexing bandpass filter is limited to a band sufficient to ensure the frequency characteristic in the passband, it has a passband wider than the occupied frequency bandwidth of one modulated wave. There is.

Therefore, a part of the adjacent modulated wave component remains at the output of the band pass filter.

The ratio of the remaining power component of the adjacent modulated wave to the power component of the own modulated wave is determined by the ratio between the own modulated wave component and the adjacent modulated wave component.

The modulated wave components output from the band pass filters 2a, 2b and 2c are output through the automatic gain amplifiers 3a, 3b and 3c for sending to the demodulator at a constant output level.

Here, each automatic gain amplifier 3a, 3b, 3
The maximum gain of c is set to a certain specific value, and the input level below this maximum gain is outside the automatic gain control range.

Therefore, the input level when this output level drops to a certain value is uniquely set to a certain value, and by monitoring this output level, it can be determined whether the input level is below a certain value. It is possible to judge.

Therefore, the automatic gain amplifiers 3a, 3b, 3
c. Each output level is branched so as not to affect the output side of the receiver from the alarm circuit side, and after being taken out by the buffer amplifiers 6a, 6b and 6c, the narrowed frequencies corresponding to the respective center frequencies are obtained. Power components of adjacent modulated waves are removed by band pass filters 7a, 7b and 7c of the bands.

This is because when the power of only the self-modulated wave decreases and the power of the adjacent modulated wave relatively increases, the adjacent modulated wave that cannot be completely removed by the demultiplexing band-pass filter. This is because it is necessary to prevent the error due to the power component from increasing and making it impossible to measure its own power level.

In this way, after a signal consisting of only the power component of the self-modulated wave from which the adjacent modulated wave component is removed is obtained for each modulated wave, the detector 8 for detecting the power level thereof is obtained.
It is input to a, 8b, and 8c, and the detection voltage according to the input power level of each modulated wave is obtained.

The respective detected voltages are compared with the voltage comparator 9
The comparison output signal is sent out as an alarm output of the received signal power by performing voltage comparison with a threshold voltage corresponding to a constant input power level at a, 9b and 9c.

[0016]

However, the above-mentioned conventional received signal power alarm circuit requires narrow band pass filters having different center frequencies for cutting adjacent modulated wave components for each modulated wave. Therefore, it is necessary to prepare various types according to the center frequency of the modulated wave.
This also involves the problem that a new bandpass filter is required each time the center frequency of the modulated wave changes.

In view of the above drawbacks, the technical problem of the present invention is to provide a received signal power alarm circuit in which a filter having one center frequency is used in common with a band-puff filter necessary for removing power components of adjacent carriers. Is to provide.

[0018]

According to the present invention, in order to receive a plurality of modulated waves that are adjacent to each other on the frequency axis, extract each modulated wave, and then send each to the demodulator,
Received signal power used in a receiver provided with a plurality of bandpass filters for extracting each modulated wave and a plurality of automatic gain control amplifiers for outputting each extracted modulated wave at a predetermined level In the alarm circuit, a plurality of frequency converters for branching the output signal of each modulated wave and converting the modulated waves having different center frequencies to the same center frequency by time division control are provided. A power combiner that integrates the outputs, a narrow band pass filter that removes the influence of the power components of the adjacent modulation waves from the modulation waves that have the same center frequency, and only the power components of each modulation wave. Detector that detects the power level of a part of the modulated wave and outputs the detection voltage according to the power level of each modulated wave, and the detected voltage is the voltage value corresponding to the power level that is the threshold for alarm activation. And electric A voltage comparator for comparison, a plurality of data holding circuit for outputting as an alarm output corresponding comparator output signal that is output by the time division to each of the modulation wave,
The control voltage of the conversion frequency of the frequency converter is sequentially generated to cause each modulation wave to appear at the output of the power combiner as a modulation wave of the same center frequency in a time division manner, and the modulation wave corresponding to the selected modulation wave is generated. And a timing signal generating circuit for generating a data holding control signal capable of selecting a data holding circuit and taking out respective alarm outputs.

That is, in the received signal power warning circuit of the present invention, a plurality of frequency converters for frequency converting the output signals of the respective modulated waves of the receiving device and the same center frequency by the frequency converters. A power combiner for combining the frequency-converted modulated waves, and a timing signal generation circuit for controlling the conversion frequency of the frequency converter and sequentially converting the modulated waves with the same frequency with a time difference and switching. A plurality of alarm data corresponding to each modulated wave from the alarm signal output in a time division manner by the control signal from the timing signal generating circuit in order to extract the power alarm output corresponding to each modulated wave. And a data holding circuit.

[0020]

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

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals.

In FIG. 1, compared with FIG. 2 which is a block diagram in the case of the above-mentioned conventional received signal power alarm circuit, the output signals taken out by the buffer amplifiers 6a, 6b and 6c are respectively fed to the frequency mixers 11a and 11a. Frequency converter 1 including 11b and 11c and local oscillators 12a, 12b and 12c
Frequency conversion is performed at 0a, 10b, and 10c.

At this time, the local oscillators 12a, 12b, 12
c is a voltage controlled oscillator (VCO), and its local oscillation frequency can be changed by a control voltage from the outside.

Therefore, since the conversion frequency can be changed depending on how the control voltage is applied, the control voltage V _DET that can be frequency-converted to a specific frequency f _DET and the control voltage V ₀ that is converted to a frequency sufficiently separated from the frequency. By alternately adding and, it is possible to make the frequency-converted modulated wave appear only during a certain time interval in the vicinity of f _DET .

As described above, the timing signal generation circuit 15 causes the local oscillators to generate control voltages for performing frequency conversion so that one specific frequency f _DET is sequentially set to the center frequency of each modulated wave in time division for each modulated wave. 12a, 12b,
It is added to 12c.

The frequency converters 10a, 10b, 10
The output of c is combined by the power combiner 13, and the output is f
_{In the} vicinity of _DET , each modulated wave appears in a time division multiplexed manner.

This multiplexed output signal is output in the same manner as in the conventional case.
By passing through a narrow band pass filter 7 having a center frequency f _DET for removing adjacent modulation waves, a detector 8 for detecting a power level, and a voltage comparator 9 for determining a power level, a multiplexed power level alarm is generated. You are getting the output signal. In order to obtain an alarm output corresponding to each modulated wave from this power level alarm output signal, it is input to the data holding circuits 14a, 14b, 14c corresponding to the respective alarm outputs, and the timing signal generation circuit 15 Accordingly, each data holding control signal is received, the data holding circuit corresponding to the selected modulated wave is selected, and each alarm output is extracted and output.

[0028]

As described above, according to the present invention, the central frequency of the modulated wave in the alarm circuit is made common by using a plurality of frequency converters, so that a narrow band pass for removing the adjacent modulated wave is obtained. This has the effect that only one filter having an arbitrary center frequency is required and the detector and the voltage comparator can be shared.

[Brief description of drawings]

FIG. 1 is a block diagram of a receiving apparatus having a received signal power alarm circuit of the present invention as an example.

FIG. 2 is a block diagram of a receiver having a received signal power warning circuit according to a conventional method.

[Explanation of symbols]

1 power divider 2a, 2b, 2c bandpass filter (for signal demultiplexing) 3a, 3b, 3c automatic gain control amplifier (AGC amplifier) 4a, 4b, 4c voltage variable gain amplifier 5a, 5b, 5c detector 6a, 6b, 6c Buffer amplifier 7, 7a, 7b, 7c Narrow band bandpass filter (for removing adjacent modulation wave) 8, 8a, 8b, 8c Detector 9, 9a, 9b, 9c Voltage comparator 10a, 10b, 10c Frequency Converter 11a, 11b, 11c Frequency mixer (mixer) 12a, 12b, 12c Local oscillator 13 Power combiner 14a, 14b, 14c Data holding circuit 15 Timing signal generation circuit

Claims (1)

[Claims] 1. A plurality of bands for extracting each of the modulated waves in order to receive the plurality of modulated waves that are adjacent to each other on the frequency axis, extract each of the modulated waves, and then send each to the demodulator. In a reception signal power alarm circuit used in a receiver equipped with a pass filter and a plurality of automatic gain control amplifiers for outputting each extracted modulated wave at a predetermined level, an output signal for each modulated wave is output. A plurality of frequency converters that branch and each of the modulated waves with different center frequencies are converted to the same center frequency by time division control; a power combiner that integrates the output of each frequency converter; A narrow-band bandpass filter that removes the influence of the power component of the adjacent modulated wave from each modulated wave that becomes a frequency, and the power level from a part of the modulated wave that has only the power component of each modulated wave. Detected A detector that outputs a detection voltage according to the power level of each modulated wave, a voltage comparator that compares the detection voltage with a voltage value that corresponds to the power level that is the threshold for alarm activation, and a time-division output A plurality of data holding circuits that output the incoming comparison output signals as alarm outputs corresponding to the respective modulated waves, and control waves of the conversion frequency of the frequency converter are sequentially generated to generate the modulated waves of the same center frequency. And a timing signal generating circuit for generating a data holding control signal capable of taking out each alarm output by selecting the data holding circuit corresponding to the selected modulated wave, in addition to A received signal power warning circuit comprising: