JPH033456A - Circuit for detecting ratio of carrier power to noise power - Google Patents

Abstract

PURPOSE:To reduce the device scale by extracting and detecting only a noise component from the phase error detection signal in a carrier wave extracting loop of a demodulator. CONSTITUTION:The phase error detection signal supplied to a C/N (ratio of carrier power to noise power) detecting circuit 1A is supplied to a high-pass filter 17 to extract only the noise component from the phase error detection signal. Since this noise component has the high band limited by receiving low pass filters 23 and 24, the output of the high pass filter 17 is equivalent to the output of a band pass filter as the result. The output signal of the noise component from the high pass filter 17 is converted to a voltage by a detector 15 and is supplied to an amplifier 16. It is amplified with a prescribed degree of amplification by the amplifier 16 to obtain a desired C/N detection signal 300. Thus, the number of parts is reduced and the device scale is reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a circuit for detecting the carrier power to noise power ratio of a received signal manually inputted to a demodulator in digital communication, and in particular a circuit that has a simple configuration and high accuracy. The present invention relates to a carrier power to noise power ratio detection circuit capable of detecting a carrier power to noise power ratio.

[Conventional technology]

Conventional carrier power to noise power ratio detection circuit (C/
The N detection circuit is known as a circuit that detects the carrier power to noise power ratio of a received signal input to a demodulator in digital communication.

FIG. 2 is a block diagram showing the conventional C/N detection circuit mentioned above.

In FIG. 2, a C/N detection circuit 1 and a demodulator 2 are connected to the output terminals of a distributor 3, respectively, so that a received signal 100 is distributed and given to them.

The C/N detection circuit 1 includes a voltage control amplifier 10 and a divider 1.
1, bandpass filter 12, detector 13, bandpass filter 1
4, a detector 15, and an amplifier 16. Further, the amplifier 16 includes resistors R0 to R2 and an operational amplifier OP.

According to such a C/N detection circuit 1, the output signal from the divider 3 is transmitted through an automatic gain controller consisting of a voltage control amplifier 10, a divider 11, a bandpass filter 12, and a wave detector 13. is input. This automatic gain controller performs automatic gain control so that the power of a desired signal is constant. In this case, the band of the bandpass filter 12 is equal to the signal band.

On the other hand, the other output signal of the divider 11 is passed through the bandpass filter 14.
is input. The bandpass filter 14 has a different center frequency from the bandpass filter 12, and extracts only noise components.

The output signal from the bandpass filter 14 is detected by a detector 15. The signal detected by the detector 15 is amplified 1IS
A C/N detection voltage is obtained by amplifying the signal at a predetermined amplification degree in step 16. That is, conventionally, automatic gain control was applied to keep the signal power constant, noise components of the signal were detected, and C/N detection was performed based on the magnitude of the detected voltage.

[Problems to be Solved] The conventional C/N detection circuit described above includes a voltage-limited 4B amplifier 10, a divider 11, a bandpass filter 12 . An automatic gain controller consisting of a wave detector 13 and bandpass filters 12 and 14 for extracting signal components and noise components are required, resulting in problems in that the number of parts increases and the scale of the device increases.

The present invention has been made in view of the above-mentioned problems, and aims to provide a C/N detection circuit that has a reduced number of parts and a smaller device size.

[Means for solving problems]

To achieve the above object, the C/N detection circuit of the present invention is a circuit for detecting the carrier power to noise power ratio of a received signal input to a demodulator in digital communication. A high-pass filter that takes in the error detection signal and extracts the noise component; a detector that detects and outputs the noise component from the high-pass filter; and an amplifier circuit that amplifies the carrier wave power to noise power ratio and outputs the signal as a carrier power-to-noise power ratio detection signal.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the C/N detection circuit of the present invention.

In the circuit shown in FIG. 1, the same components as those in the device shown in FIG. 2 will be described with the same reference numerals. In Figure 1, C
/N detection circuit IA and demodulator 2 are provided.

The demodulator 2 is capable of taking in the received signal 100, performing predetermined digital conversion, and outputting it as a demodulated signal 200. That is, the demodulator 2 has a voltage control amplifier 2
0, mixer 21, 22, receiving low-pass filter 23,
24, analog/digital converters 25, 26, clock extractor 27, phase error detector 28, and digital/digital converters 25, 26, clock extractor 27, phase error detector 28,
an analog converter 29, a loop low-pass filter 30,
It is composed of a voltage controlled oscillator 31, a phase shifter 32, and a wave detector 33.

The C/N detection circuit IA is a high-pass filter 1 that takes in the phase error detection signal from the digital-to-analog converter 29 in the carrier extraction loop in the demodulator 2 and extracts the noise component.
7, a detector 15 that detects and outputs the noise component from the high-pass filter 17, and an amplifier that amplifies the output signal from the detector 15 at a predetermined amplification degree and outputs it as a C/N detection signal. It is composed of a circuit 16.

The operation of the embodiment configured as described above will be explained.

The received signal 100 is voltage-controlled amplified by the demodulator 2! ! 20
is man-powered. The outputs of the voltage controlled fil amplifiers 20 are input to mixers 21 and 22, respectively. Mixer 21.22
The output signals from are fed to analog-to-digital converters 25, 26 via receiving low-pass filters 23, 24.

On the other hand, the output signal of the receiving low-pass filter 24 is supplied to the clock extractor 27 and the wave detector 33. Detector 33
The output signal becomes the fl[ signal of the voltage control amplifier 20, and automatic gain control is applied so that the level of the eye pattern is constant.

Further, the clock signal extracted from the clock extractor 27 is used as a sampling clock signal of the analog-to-digital converters 25 and 26.

The sampling timing is performed at the convergence point of the eye pattern.

Each output signal of the receiving low-pass filters H23 and H24 is output as a demodulated signal 200, and the output signal of the zero phase error detector 28, which is supplied to the phase error detector 28 of the carrier extraction loop, is a digital signal. - It is converted into an analog signal by the analog converter 29 and supplied to the loop low-pass filter H30 and the C/N detection circuit IA. The signal supplied to the loop low-pass filter 30 is converted into a signal with a frequency according to the input voltage by a voltage controlled oscillator 31, and is supplied to a phase shifter 32 and a mixer 21.22.

Here, the phase error detection signal supplied to the C/N detection circuit IA is supplied to a high-pass filter 17 to extract only noise components from the phase error detection signal. This noise component is low-pass filtered! Since the high frequency band is limited by 123°24, as a result, the high-pass filter 17
The output signal of is equivalent to the output of a bandpass filter. The noise component output signal from the high-pass filter H17 is converted into a voltage by the detector 15 and supplied to the amplifier 16. The amplifier 16 amplifies the signal at a predetermined amplification degree to obtain a desired C/N detection signal 300.

〔Effect of the invention〕

As explained above, the present invention extracts and detects only the noise component from the phase error detection signal in the carrier extraction loop of the demodulator, thereby achieving a high-precision C//
This has the effect that N detection signals can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional device. IA... C/N detection circuit, 2... Demodulator, 15.
...Detector, 16...Amplifier, 17...High-pass filter.

Claims (1)

[Claims] In a circuit that detects the carrier power to noise power ratio of a received signal input to a demodulator in digital communication, a high-pass filter that takes in a phase error detection signal in a carrier extraction loop in the demodulator and extracts a noise component. , a detector that detects and outputs the noise component from the high-pass filter, and an amplifier circuit that amplifies the output signal from the detector at a predetermined amplification degree and outputs it as a carrier power to noise power ratio detection signal. A carrier power to noise power ratio detection circuit comprising: