Research On The Design And Application Of Miniaturized 3dB Bridge Broadband Based On LTCC Technology

3dB bridge is a special directional coupler.According to the different phase of the outputsignal,3dB bridge can be divided into 90 degree bridge and 180 degree bridge.3dB bridge is the important passive device of microwave communication,measurement circuit,antenna feeding network and other systems.With the rapid development of communication technology,people try to make bold improvements and innovations in traditional theories and structures to meet the development needs of the present stage.Miniaturization and broadband are the two main research directions.LTCC(Low Temperature Co-fired Ceramic)technology has tremendous advantages with the characteristic of its multi-layer embedding in device to meet miniaturization trend.This article uses LTCC three-dimensional integrated technology to improve and innovate the traditional 3dB bridge,and implements a wideband 90-degree bridge and a wide-band 180-degree bridge.On the basis of this,a 90 degree bridge and 180 degree bridge are used to designed a wideband planar magic T and broadband monopulse processor.The main contents of this paper are as follows:1 Combined with the design idea of multi-section symmetric directional coupler and coupler cross-series,a single and five serial symmetrical directional coupler cross-serial 90 degree wide-band bridge is proposed,and the serpentine broadside coupling stripline and coupling line multilayer cascade structure are applicated to reduce the volume.At]ast,the bandwidth of 90-degree bridge is 0.6～3.8GHz,the final size control At 12.7 mm × 7.5 mm ×2.2 mm.After processing and testing,the performance meets the index requirements.2.Based on the improvement of the traditional 180 degree annular bridge and the design theory of T junction knot divider and Marchand balun,a new type of spiral 180 degree bridge with high isolation is proposed with the same-phase power divider and reverse-phase balun balanced terminal reverse docking.And the input and output port have achieved best match using quarter-wave match line to maximize VSWR bandwidth.Finally,the novel LTCC wideband 180 degree bridge with a working band of 1～2GHz and a isolation of 35dB is implemented.The dimensions is only 8mm × 6.7mm × 1.9mm.After processing and testing,the performance meets the index requirements.3.Applying the ultra wideband design principle of the previous 90 degree bridge to the design of the plane magic T,the magic T is designed with a 90 degree phase shifter cascading a 90 degree bridge in a one-sided dielectric substrate.90 degree bridge is the wide-edged and narrow side coupling single three-section symmetry form,90 degrees phase shifter uses a folded coupled transmission line loaded with a short-circuit stub structure in the middle.The ultra wideband planar T structure is novel and has a compact layout.The working frequency is 5-13 GHz and the size is 15 mm × 6 mm × 1 mm.4.A broadband 180 degree bridge with high isolation is applied to the design of monopulse processor.Four identical 180-degree bridges were designed as a cleverly combination of L-Band broadband monopulse processor with high isolation,high zero depth,and low insertion loss.The 180 degree bridge adopts the balun and power split reverse docking type,the structure is distributed up and down to reduce the area,the final bandwidth is 1.2～1.8GHz,the zero value depth is greater than 35dB,and the insertion loss is less than 0.65dB,the size is 17mm×9.5mm×2mm.The simulation results verify the designed rationality.