Abstract: Suspended particulate matter in the atmospheric air is sucked into a container by a pump. The suspended particulate matter in the atmospheric air in the container is electrically charged so as to electrically collect it. The collected suspended particulate matter is irradiated with laser beams under the condition that the collected suspended particulate matter is dispersed at an appropriate concentration. A spatial intensity distribution of diffracted and scattered light obtained by irradiating laser beams to the suspended particulate matter is measured. A particle size distribution of the suspended particulate matter P is found from the result of measurement.

Abstract: Suspended particulate matter in the atmospheric air is sucked into a container by a pump. The suspended particulate matter in the atmospheric air in the container is electrically charged so as to electrically collect it. The collected suspended particulate matter is irradiated with laser beams under the condition that the collected suspended particulate matter is dispersed at an appropriate concentration A spatial intensity distribution of diffracted and scattered light obtained by irradiating laser beams to the suspended particulate matter is measured. A particle size distribution of the suspended particulate matter P is found from the result of measurement.

Abstract: In a transmitter and receiver system, a frequency converter doubles as a transmitter local oscillator, a receiver local oscillator, and a transmitter frequency converter.The present local oscillator is a semi-conductor oscillator such as a gunn diode or IMPAT diode, the DC power supply of which is converted to an intermediate frequency signal. The oscillator is stabilized by self injection locking by a cavity resonator connected to the output of the diode, thus the oscillating frequency is very stable. Some of the output power of the oscillator is separated for the receiving local oscillator through an isolator and an attenuator. The intermediate frequencies of a transmitter and receiver have a predetermined relationship.

Abstract: A high-frequency automatic gain control circuit for a common emitter earthed amplifier wherein a hybrid negative feedback is applied to an input stage thereof from the emitter of an output stage transistor through a hybrid transformer connected to the base of an input stage transistor and a series negative feedback is applied to the output stage thereof, and according to the present invention a diode which is shunted by a capacitor is connected in series to an emitter resistor of the output stage transistor, and an automatic gain control signal is applied to said diode for regulating the gain of said amplifier by controlling negative feedback ratio of said negative feedback.