18-40GHz double balanced mixer in star structure

Abstract

An 18-40GHz double balanced mixer in structure belongs to the microwave and millimeter wave technical field and relates to a double balanced mixer in star structure. The mixer comprises a double ridge waveguide and a hybrid circuit board and an intermediate frequency output terminal which are arranged on the plane E at the center of the double ridge waveguide. In the invention, the height of the two ridges of the 18-40GHz double ridge waveguide is linearly decreased in a gradient way, thus being convenient for installing diodes and being beneficial to improving impedance matching between a fin line and a coplanar strip line; when leading the intermediate frequency out, an inner conductor passes through a medium substrate and extends to the interior of a cavity and close to the wall of the cavity, so as to improve the symmetrical characteristic of an LO and RF signal field structure, thus improving the balance of four diodes, frequency conversion loss and insulation between an LO signal and an RF signal; a bead is adopted to lead the intermediate frequency out, installation is convenient, and reliability is good; and a boss is additionally arranged at the lead out point of the intermediate frequency at the narrow side of the ridge waveguide, thus being beneficial to improving intermediate frequency bandwidth. The invention has the advantages of wide working band, small size, low frequency conversion loss and high insulation and has a favourable application prospect in an ultra wide band transceiver.

Description

technical field [0001] The invention belongs to the field of microwave and millimeter wave technology, and relates to a millimeter wave ultra-wideband hybrid integrated circuit double-balanced mixer. Background technique [0002] The mixer is a device that realizes the sum or difference operation of two frequencies (or its harmonics). It is a key component in a superheterodyne receiver, and its specifications largely determine the performance of the entire receiving system. The double-balanced mixer of the star structure, its circuit principle is as follows figure 1 As shown, a star structure composed of four identical mixing diodes, the positive poles of diodes 1 and 3 and the negative poles of diodes 2 and 4 are connected together to form the intermediate frequency output terminal; then the local oscillator signal is divided into two paths with opposite phases The signals are respectively input to two groups of diodes (diodes 1 and 4 form one group, and diodes 2 and 3 for...

AI Technical Summary

Problems solved by technology

[0007] Since the mixer uses a rectangular waveguide, its operating bandwidth cannot cover the entire frequency band of 18-40 GHz. At the same time, the IF output adopts a coaxial cable structure, and the inner conductor and dielectric core of the coaxial cable need to be processed separately, which is difficult to assemble and has poor reliability.

Since the inner conductor of the intermediate frequency coaxial line extends into half of the waveguide cavity, the structural symmetry of the double-balanced mixer is destroyed, and the important index of frequency conversion loss is deteriorated to a certain extent.

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