43results about How to "Reduce RF loss" patented technology

The invention discloses a body coil of a magnetic resonance imaging system, and a magnetic resonance imaging system. The body coil comprises a main body and a tuning and detuning circuit; the tuning and detuning circuit is connected with the main body for performing tuning and detuning control on the main body by use of control signals; the tuning and detuning circuit comprises a control signal interface, at least one switch diode unit and an AC-DC conversion circuit; the control signal interface is used for receiving control signals; the at least one switch diode unit is used for serial connection with at least one antenna leg and / or at least one end ring of the coil main body; and the AC-DC conversion circuit comprises a rectification circuit and is used for converting power of input radio frequency emission signals in the magnetic resonance imaging system into DC currents, the DC currents are used for providing DC currents for conduction of the switch diode unit. The body coil can reduce the cost of a DC power source and solves the problem of heating of a diode.

The invention discloses a preparation method of a Si substrate AlN template and a preparation method of a Si substrate GaN epitaxial structure. The preparation method of the Si substrate AlN templatecomprises the following steps: selecting a Si substrate; growing an AlN nucleating layer on the Si substrate; and injecting ions into the Si substrate through the AlN nucleating layer. After the AlN nucleating layer is prepared on the Si substrate, ion implantation on the Si substrate and injecting ions into the AlN nucleating layer are performed through the AlN nucleating layer, so that the typesof the ions injected in the mode can be expanded, the carrier concentration at the Si / AlN interface and the carrier concentration in the AlN nucleating layer can also be reduced, the radio frequencyloss of the Si substrate AlN template is reduced, the characteristics of a GaN microwave device manufactured by using the Si substrate AlN template are improved, and the application requirements of the GaN microwave device in the fields of aerospace, radar, mobile communication and the like are met. In addition, a GaN device epitaxial structure is prepared by using the Si substrate AlN template, and the design of the GaN device epitaxial structure has more degrees of freedom.

The invention provides a shortwave antenna tuning insertion loss test fixture comprising a vector network analyzer, a measurement and control computer, a radio frequency conversion switch K1 and tested antenna tuning and an antenna, wherein the measurement and control computer is connected with a vector network, the tested antenna tuning and the radio frequency conversion switch K1 through a serial port or a network port, the K1 communicates the tested antenna tuning 1 on an antenna port 2 at a first position, namely the connects the tested antenna tuning to the tested antenna; the K1 communicates the antenna port 2 with a vector network port at a second position, namely connects the tested antenna to the vector network port; and an output end of the measurement and control computer controls a control switch K1 and the tested antenna tuning.

The invention provides a process for preparing barium strontium titanate and cordierite glass ceramic composite medium material, which comprises, (1) preparing barium strontium titanate dielectric material, grinding into super fine powder, (2) uniformly mixing each oxide compound of the dielectric composition and grinding into super fine powder, die pressing, high temperature sintering, repulverizing and grinding into super fine powder, (3) loading the agglutination formed cordierite glass ceramics super fine powder uniformly into the barium strontium titanate super fine powder, uniformly mixing through grinding, die pressing and high temperature sintering, (4) preparing super fine powder with particle diameter <=1micrometer again, moulding, high-sintering to obtain the end product.

The invention discloses a drain-source area medium / PN junction isolated front-gate P / N-MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) radio frequency switch ultralow-loss device based on an SOI (Silicon On Insulator) technology, wherein SOIP(N)-MOSFET device source and drain regions are modified, PN junctions or dielectric capacitors are produced in the source and drain regions, the junctions in source regions are large in depth, N(P) type doping or mediums are implanted in the source regions to form PN junctions or dielectric capacitors so as to form isolation to the voltage of direct current applied by a drain; through the biasing arrangement of the MOS and back-gate, the back-gate MOSFET channel is in a conducting state, altering current signals at the front-gate P(N)-MOSFET drain region are coupled to back-gate MOSFET; since the back-gate works in the conducting state, adjustment to impedance in ON state of the front-gate MOSFET is formed due to the structure, so that the radio frequency loss of the front-gate MOSFET serving as the switch applying to the ON state is reduced; when the back-gate MOSFET device generates negative impedance due to that the device generates self-heating effect, and the back-gate MOSFET works in the amplification state, front-gate coupling signals is directly amplified, energy loss in the ON state of the front-gate is compensated, and thus the ultrlow / zero-loss radio frequency switch is formed.

The invention discloses a hinge structure with a signal transmission line. The hinge structure comprises at least two rotating vanes and two parallel rotating vane connecting pieces arranged between the two adjacent rotating vanes, i.e. a first rotating vane, a second rotating vane, a first rotating vane connecting piece and a second rotating vane connecting piece, wherein the first and second rotating vanes are connected through the first and second rotating vane connecting pieces in a rotating manner; each rotating vane connecting piece comprises at least two parallel signal transmission channels; the signal transmission channels in each rotating vane connecting piece are in S-shaped connection; a signal of a first unit connected with the first rotating vane can be transmitted into a second unit connected with the second rotating vane. According to the hinge structure with the signal transmission line, the signal transmission channels are designed as in the S-shaped connection, so that the signal transmission channels are perpendicular to a rotating direction, are namely parallel to the hinge structure, and are not likely to be bent along with bending of the hinge structure, influence on transmission performance of the signal transmission line is eliminated, and long service life is ensured.

The invention relates to a frequency-tunable high-temperature superconducting microwave resonator, which is designed by using the characteristic that the equivalent nonlinear inductance of the Josephson junction changes with the current. The low-inductance adjustment open loops at both ends of any diameter of the device are directly coupled. There is a Josephson junction on each of the two adjustment open loops. The two adjustment open loops are respectively connected to a current source to form two adjustment circuits. By changing the current of the open loop, the equivalent inductance of the Josephson junction can be changed, and then the equivalent inductance of the ring resonator can be changed through the coupling between the open loop and the resonator, and finally the purpose of adjusting the resonance frequency can be achieved. The invention has the advantages of simple structure, easy realization, high Q value, low required control energy, rapidity, stability, low radio frequency loss and the like.