SU798640A1 - Apparatus for measuring signal and interference of photoreciever - Google Patents

Description

(54) DEVICE FOR MEASURING A SIGNAL AND TUVMA PHOTO-RECEIVER

The invention relates to a measurement technique and is intended to measure the basic parameters of a photodetector. There are known devices for measuring a signal and a photodetector noise, which contain a radiation source and a modulator installed before measuring by a photoreceiver, connected via an amplifier to a recording device 1. The disadvantage of devices of this type is the inability simultaneously measuring the voltage of the signal and the noise voltage of the photodetectors, which is necessary to study the dynamics of its operation. A device for measuring the signal and noise of a photodetector is known, which contains a radiation source and a module that is installed in front of the photodetector under investigation, connected to two measuring paths containing resonance, amplifiers and indicators .2. To separate the voltage signal and noise in such devices, frequency selection is used: the amplifier in the measuring paths is made resonant with different resonant frequencies, and the ratio of the frequencies must be greater than or equal to 4, i.e. the modulator is sinusoidal. As a result of the use of frequency selection, the frequency range in which research can be carried out is significantly narrowed / and for the remaining frequencies it is completely unsuitable for A / D due to the inertia of the photodetectors and the significant dependence of the noise level on the frequency. that are substantially different from each other, and often results in uncorrected results, depending on the individual properties of the photodetector under investigation. In order to improve the technical characteristics, the measurement of the signal on these devices must be conducted on optical streams of very mild intensity, since at high fluxes the noise voltage of the photoreceiver increases due to the fact that the higher harmonics of the signal voltage are not sufficiently attenuated by filters and enter the noise voltage measurement channel.

The purpose of the invention is to improve the measurement accuracy.

This goal is achieved by the fact that in the device for measuring the signal and noise of the photodetector, containing a series-connected radiation source and a modulator, the output of which is connected to one device’s depth, and also two measuring channels, each of which contains a series-connected resonant amplifier and indicator, are entered a switch, one input of which is connected to another input of the device, another - to the output of the modulator and the output - to the input-1I measuring channels, the modulator being made amp-pulse-pulse.

FIG. 1 shows a functional diagram of the device; Fig. 2 shows the modulation of the luminous flux and the corresponding voltage pattern at the output of the photodetector; in fig.ZForm of the amplitude-pulse disk drive.

Before measured photodetector

1, an amplitude-pulse modulator 2 and a radiation source 3 are installed. The output of the photodetector 1 is enabled switch 4, synchronized

with modulator 2 and connected to two measuring channels 5, containing amplifiers b and indicators 7. The resonant frequencies of amplifiers 6 are the same in both measuring paths.

Pulse amplitude modulator

2 can be electromechanical: amplitude-pulse modulation is provided by a disk shape (Fig. 3). In addition, other embodiments of pulse-amplitude modulation (modulated light source power supply, etc.) are possible.

The device works as follows.

A continuous optical stream from source 3 is converted by a modulator 2 into an amplitude-pulse signal (Fig. 2a). When a signal is applied to the photodetector 1, a corresponding electrical signal appears at its output, containing the voltage of the photosignal and the self-noise voltage of the photodetector (Fig. 26). Using switch 4, controlled by modulator 2, the signal and noise voltages are fed to the corresponding measuring paths 5, where the signal is amplified and recorded.

The use of resonant amplifiers is due to the fact that in general

In some cases, it is necessary to separate the signal, the magnitude of which is commensurate with the level of the intrinsic noise of the photodetector and the measuring path, and the narrowing of the passband leads to a significant reduction in their 5 noise, without reducing the magnitude of the signal. The proposed device eliminates the need for frequency selection, since the amplitude-impulse modulator provides a time separation of the useful signal and noise, and it is possible to measure the signal voltage and photodetector noise at any frequency equal to

5 of both channels, which lies within the frequency range of the photodetector, as a result of which the frequency range of measurements significantly expands and the possibility of systematic error is eliminated. In addition, the high harmonics of the signal voltage are almost completely eliminated in the noise measurement channel, which in turn removes

 restrictions on the level of intensity of the radiation flux.

The calculations showed that the accuracy of noise measurement in the proposed device is 2-3 times higher due to the expansion of equivalent noise

0 bands to any practical value (200-400 Hz).

Claims (1)

1. GOST 18167-72, p. 10. 52. Radiant energy receivers semiconductor, photoelectric cooled. Methods for determining the time to enter the mode and: time autonomy work. GOST 3-3205-75, p.11. . (Reg. F