Abstract: A quadrifilar helical antenna includes a conical supporting medium, a feed network, and four sets of antenna composite elements. Each set of antenna composite element includes at least one short-circuit helical arm and at least one open-circuit helical arm. The short-circuit helical arm and the open-circuit helical arm in each set of antenna composite element are sequentially wound on an outer wall of the conical supporting medium in one winding direction. In an axial direction of the conical supporting medium, a projection length of the short-circuit helical arm is greater than that of the open-circuit helical arm in each set of antenna composite element. The four sets of antenna composite elements are respectively coupled to a feeding point of the feed network for feeding, and the short-circuit helical arms in the four sets of antenna composite elements are in short-circuit connection.

Abstract: The present disclosure provides a method and device for frequency hopping synchronization, a receiver, and a transmitter.

Abstract: Disclosed is an antenna mounting base and an antenna, the antenna mounting base comprising: an antenna substrate, a fixing plate and an annular reflective plate, wherein the antenna substrate is of a bowl-shaped structure, and an edge of an opening of the bowl-shaped structure is fixed to the fixing plate; the annular reflective plate stands on the fixing plate and is fixed to the fixing plate; the annular reflective plate and the antenna substrate are located on the same side of the fixing plate; and a feed support base is provided inside the bowl-shaped structure. In comparison with existing product technology, this antenna is simple to assemble, and has stronger structural consistency, and furthermore, the low pitch angle gain of the antenna is higher.

Abstract: A method for TDMA slot synchronization and calibration of a master and a slave includes: receiving a synchronizing frame from the master by the slave, wherein the synchronizing frame includes a first count value of a timing counter of the master; analysing the synchronizing frame by the slave to acquire the first count value; and adjusting a TDMA slot of the slave according to the first count value and a second count value of a timing counter of the slave to synchronize the TDMA slot of the slave with a TDMA slot of the master.

Abstract: The present disclosure relates to the technical field of cryogenic cooling. In particular, the present disclosure relates to a mechanical vibration-isolated, liquid helium consumption-free cryogenic cooling device. The system according to some embodiments of the present disclosure comprises: a closed-cycle cryogenic cooling system, a helium heat exchange gas cooling and vibration isolation interface system, a cryogenic throttle valve cooling system, and a temperature feedback control system. The closed-cycle cooling system includes a cold head, a compressor, and a helium pipeline. The cryogenic throttle valve cooling system is thermally coupled to a low-temperature end of the cooling and vibration isolation interface.

Abstract: The present disclosure provides a method for controlling frequency hopping, a transmitter and a receiver, the method comprising: switching a synchronization frequency to any pre-configured synchronization frequency value when a time slot for sending a synchronization frame is reached, and sending the synchronization frame; after the previous synchronization frame is sent, switching the synchronization frequency from the previous pre-configured synchronization frequency value to any pre-configured synchronization frequency value, and sending the synchronization frame; after a total time slot for sending a synchronization frame is complete, switching a data frequency to any pre-configured data frequency value, and sending the data frame when the time slot for sending a data frame is reached; or, receiving a data frame when a time slot for receiving a data frame is reached; after the previous data frame is sent or received, and sending a data frame, switching the data frequency from a previous pre-configured dat

Abstract: A quadrifilar helical antenna includes a conical supporting medium, a feed network, and four sets of antenna composite elements. Each set of antenna composite element includes at least one short-circuit helical arm and at least one open-circuit helical arm. The short-circuit helical arm and the open-circuit helical arm in each set of antenna composite element are sequentially wound on an outer wall of the conical supporting medium in one winding direction. In an axial direction of the conical supporting medium, a projection length of the short-circuit helical arm is greater than that of the open-circuit helical arm in each set of antenna composite element. The four sets of antenna composite elements are respectively coupled to a feeding point of the feed network for feeding, and the short-circuit helical arms in the four sets of antenna composite elements are in short-circuit connection.

Abstract: The present disclosure provides a method and device for frequency hopping synchronization, a receiver, and a transmitter.

Abstract: The present disclosure provides a method for controlling frequency hopping, a transmitter and a receiver, the method comprising: switching a synchronization frequency to any pre-configured synchronization frequency value when a time slot for sending a synchronization frame is reached, and sending the synchronization frame; after the previous synchronization frame is sent, switching the synchronization frequency from the previous pre-configured synchronization frequency value to any pre-configured synchronization frequency value, and sending the synchronization frame; after a total time slot for sending a synchronization frame is complete, switching a data frequency to any pre-configured data frequency value, and sending the data frame when the time slot for sending a data frame is reached; or, receiving a data frame when a time slot for receiving a data frame is reached; after the previous data frame is sent or received, and sending a data frame, switching the data frequency from a previous pre-configured dat

Abstract: Disclosed is an antenna mounting base and an antenna, the antenna mounting base comprising: an antenna substrate, a fixing plate and an annular reflective plate, wherein the antenna substrate is of a bowl-shaped structure, and an edge of an opening of the bowl-shaped structure is fixed to the fixing plate; the annular reflective plate stands on the fixing plate and is fixed to the fixing plate; the annular reflective plate and the antenna substrate are located on the same side of the fixing plate; and a feed support base is provided inside the bowl-shaped structure. In comparison with existing product technology, this antenna is simple to assemble, and has stronger structural consistency, and furthermore, the low pitch angle gain of the antenna is higher.

Abstract: A scanning probe microscope of the present disclosure includes: a room-temperature bore superconducting magnet including a liquid helium-consumption free closed-cycle cooling system, a superconducting magnet, and a chamber having a room-temperature bore; and a scanning probe microscope including a scanning head, a vacuum chamber, and a vibration isolation platform; and a computer control system. The room-temperature bore superconducting magnet is cooled by the cryogen-free closed-cycle cooling system which eliminates the dependence on liquid helium for high magnetic field operation. There is no physical contact between the scanning probe microscope and the superconducting magnet connected to the closed-cycle cooling system. The scanning probe microscope can achieve atomic-scale spatial resolution. The temperature of the scanning probe microscope is not restricted by the low temperature conditions for operation of the superconducting magnet.

Abstract: A multifunctional GNSS antenna includes a PCB and first and second dielectric plates arranged in a stacked manner. The PCB has a lower surface with a circuit network, which is covered by a metal shield cover. The first dielectric plate has an upper surface with a first metal layer and a lower surface attached to an upper surface of the PCB. A first feed probe penetrates the first metal layer and the first dielectric plate and is coupled with the circuit network. A third metal layer is embedded in an edge and a lateral surface of the first dielectric plate, and is coupled by a third feed probe with the circuit network while a first short-circuit probe shorts the third metal layer to ground. The second dielectric plate has an upper surface with a second metal layer coupled by a second feed probe with the circuit network.

Abstract: The present disclosure relates to a method and an apparatus for TDMA slot synchronization and calibration of a master and a slave. The method includes: receiving a synchronizing frame from a master by at least one slave, in which the synchronizing frame includes a first count value of a timing counter of the master; analysing the synchronizing frame by the at least one slave to acquire the first count value; adjusting a TDMA slot of each slave according to the first count value and a second count value of a timing counter of the slave to synchronize the TDMA slot of the slave with a TDMA slot of the master. It can be seen that the synchronization is realized by directly using the respective clock sources of the master and the slave, without addition of the clock source of the RTC or the GPS module, thus reducing the cost and improving the accuracy.

Abstract: A multifunctional GNSS antenna includes a PCB and first and second dielectric plates arranged in a stacked manner. The PCB has a lower surface with a circuit network, which is covered by a metal shield cover. The first dielectric plate has an upper surface with a first metal layer and a lower surface attached to an upper surface of the PCB. A first feed probe penetrates the first metal layer and the first dielectric plate and is coupled with the circuit network. A third metal layer is embedded in an edge and a lateral surface of the first dielectric plate, and is coupled by a third feed probe with the circuit network while a first short-circuit probe shorts the third metal layer to ground. The second dielectric plate has an upper surface with a second metal layer coupled by a second feed probe with the circuit network.

Abstract: The present invention discloses a polyvinylidene fluoride hollow fiber membrane and a preparation method thereof. The hollow fiber membrane comprises 30%-50% of polyvinylidene fluoride resin, 40%-60% of inorganic molecular solution in-situ pore-forming agent and 5%-20% of organic diluent.

Abstract: The present disclosure relates to a mechanical vibration-isolated, liquid helium recondensing cryogenic cooling system. The system according to some embodiments of the present disclosure includes: a closed-cycle cryogenic cooling system, a liquid helium recondensation cooling and vibration isolation system, and a temperature feedback control system. The present invention utilizes a closed-cycle cryogenic cooling system and may achieve low temperatures as low as 4.2 K and may consume substantially no helium gas or liquid helium. Using the cooling and vibration isolation system, liquid helium is generated and maintained through recondensation of helium gas. Not only does the technology effectively isolate the low-frequency vibrations produced by the closed-cycle cryogenic cooling system during operation, but it also resolves the issue of large fluctuations in the resulting temperature of the closed-cycle cryogenic cooling system.

Abstract: The present disclosure relates to the technical field of cryogenic cooling. In particular, the present disclosure relates to a mechanical vibration-isolated, liquid helium consumption-free cryogenic cooling device. The system according to some embodiments of the present disclosure comprises: a closed-cycle cryogenic cooling system, a helium heat exchange gas cooling and vibration isolation interface system, a cryogenic throttle valve cooling system, and a temperature feedback control system. The cryogenic cooling system provided by the present disclosure can achieve extremely low temperatures, as low as 1.4 K (based on helium-4 medium) or 0.2 K (based on helium-3 medium) without the need for the consumption of liquid helium. The disclosed cooling system can also efficiently isolate intrinsic mechanical vibrations of the closed-cycle cooling system. The disclosed cooling system can achieve variable temperature regulation through the temperature feedback control system.

Abstract: A scanning probe microscope of the present disclosure includes: a room-temperature bore superconducting magnet including a liquid helium-consumption free closed-cycle cooling system, a superconducting magnet, and a chamber having a room-temperature bore; and a scanning probe microscope including a scanning head, a vacuum chamber, and a vibration isolation platform; and a computer control system. The room-temperature bore superconducting magnet is cooled by the cryogen-free closed-cycle cooling system which eliminates the dependence on liquid helium for high magnetic field operation. There is no physical contact between the scanning probe microscope and the superconducting magnet connected to the closed-cycle cooling system. The scanning probe microscope can achieve atomic-scale spatial resolution. The temperature of the scanning probe microscope is not restricted by the low temperature conditions for operation of the superconducting magnet.

Abstract: The present invention discloses a polyvinylidene fluoride hollow fiber membrane and a preparation method thereof. The hollow fiber membrane comprises 30%-50% of polyvinylidene fluoride resin, 40%-60% of inorganic molecular solution in-situ pore-forming agent and 5%-20% of organic diluent.

Abstract: A feeding bottle includes a bottle body, a retaining member, a sucking component and a nipple. The bottle defines an opening, the retaining member has a bowl portion and a barrel portion, the bowl forms peripheral flange. The sucking component includes a tube and a sucking head, the nipple includes a latching section having resisting flange. The bottle body, the retaining member, the sucking component, and the nipple are made of silicon material, the retaining member engages into the bottle body, the tube and the sucking head are received in the bottle body, the bowl portion is received in the open, and the peripheral flange abuts on the top of the open. The nipple engages with the retaining member, the latching section fits with the barrel portion, and the resisting flange abuts on the peripheral flange.