CN105304997A

CN105304997A - Low-cost and low-loss millimeter wave packaging structure with ground compensation

Info

Publication number: CN105304997A
Application number: CN201510692436.6A
Authority: CN
Inventors: 李连鸣; 夏海洋; 张涛; 崔铁军
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2015-10-23
Filing date: 2015-10-23
Publication date: 2016-02-03
Anticipated expiration: 2035-10-23
Also published as: CN105304997B

Abstract

The invention discloses a low-cost and low-loss millimeter wave packaging structure with ground compensation, which comprises a signal line compensation network and a ground wire resonant compensation network. A signal line adopts an L-C-L T-shaped compensation network, and the ground wire uses an LC series resonant compensation network. The above two compensation networks can be designed independently, design complexity of the packaging structure is reduced, and the design time is greatly reduced. Through carrying out channeling processing on the PCB, the channel depth is controlled, a chip can be embedded in the PCB, the chip and the PCB have the same surface height, the length of a binding line is reduced, the packaging bandwidth is enhanced, and loss is reduced. Ground at two sides of the packaging structure PCB is separated, ground backflow paths are reduced, and outer interference is reduced. A method of widening a microstrip line in advance is used, and performance influences caused by actual line width processing errors can be reduced. In addition, as a multilayer overlapping structure is adopted, selections of multiple layers of PCB wiring is provided, and leading out of chip DC signals is realized conveniently.

Description

The millimeter wave encapsulating structure that a kind of low cost low-loss band ground compensates

Technical field

The present invention relates to millimetre-wave circuit encapsulating structure, belong to millimeter wave encapsulation technology field.

Background technology

Along with the fast development of the aspect such as mobile communication, satellite communication, more and more higher to system communication rate requirement.Because millimeter wave frequency band has very abundant frequency spectrum resource, millimetre-wave attenuator becomes more and more important.Most important in millimeter-wave systems is exactly radio-frequency front-end, and it comprises millimeter wave transceiver and antenna.The module of millimeter wave transceiver inside or need between transceiver with antenna to be connected by certain mode.As a kind of interconnect scheme of simple low cost, binding line encapsulation is widely used.In the application of millimeter wave frequency band, binding line is equivalent to the inductance of a series connection, and it is very large to the performance impact of system.In major part design, chip is generally placed on the surface of printing board PCB, and this can cause binding line very long usually.Circuit effect, this is equivalent to introduces a larger inductance at the output of circuit or input, and cause impedance mismatch, return loss is deteriorated, and increases the loss of circuit, final influential system performance.Be based upon on the basis of multiple filter mostly to the encapsulation of millimetre-wave circuit before.In the design process of reality, owing to needing the parameter of optimization many, usually need to spend a large amount of time in emulation.And encapsulation before mainly completes the compensation to holding wire, seldom do not relate to the compensation deals to ground wire.On circuit performance, this can cause whole circuit performance to decline.In addition, major part encapsulation less consideration PCB mismachining tolerance in the design process before, this will cause the actual properties of product processed inconsistent with emulation.

Summary of the invention

Goal of the invention: for the above-mentioned shortcoming of prior art, the millimeter wave encapsulating structure that the present invention compensates with proposing a kind of low cost low-loss band, can increase the bandwidth of encapsulating structure, reduces insertion loss, reduce external interference, weaken PCB and add the performance impact that the error brought man-hour brings.In addition, this invention also effectively can accelerate design time.

Technical scheme: the millimeter wave encapsulating structure that a kind of low cost low-loss band ground compensates, adopt the stepped construction of PCB, using the 4th layer of metal and third layer metal as encapsulating structure main body, its 4th layer of metal comprises holding wire compensating network and ground wire resonance compensation network; Third layer metal is as stratum, and be the reference ground on whole pcb board, the ground on third layer metal both sides will separate; Second layer metal and first layer metal distribution direct current and ground cabling; Wherein, described chip needs to be embedded in the groove that PCB offers, and guarantees that chip surface height is consistent with PCB apparent height.By realizing chip surface and PCB surface is in sustained height, the length of binding line can be reduced, increasing the bandwidth of encapsulating structure, reducing the wastage.

Described holding wire compensating network is made up of binding line inductance, microstrip line shunt capacitance, microstrip line inductance three part, forms the compensating network of a L-C-L; Finally this compensating network is drawn by the microstrip line that characteristic impedance is 50 ohm.

Described ground wire resonance compensation network is made up of binding line inductance, microstrip line electric capacity two parts, forms a LC series resonant network.

Isolate the ground on described PCB both sides, reduce the return flow path on PCB ground in encapsulating structure, reduce external interference.

Widen the microstrip line in described PCB in advance, to reduce the impact that fabrication error brings.

The present invention includes holding wire compensating network and ground wire resonance compensation network two parts.Described holding wire compensating network is made up of three parts: the binding line be connected with chip as series inductance, the wider microstrip line that is connected with binding line as direct-to-ground capacitance in parallel, thinner microstrip line as series inductance; Three above-mentioned parts form the compensating network of a L-C-L jointly; The microstrip line that this compensating network is 50 ohm by characteristic impedance is drawn.Described ground wire resonance compensation network is made up of two parts: the binding line be connected with chip as series inductance, the microstrip line that is connected with binding line as the direct-to-ground capacitance of connecting; Above-mentioned two parts form a LC series resonant network jointly.

Two described compensating networks can independently design respectively, greatly reduce the complexity of encapsulating structure design, reduce design time.In implementation process, for improving the bandwidth of encapsulation, and then reducing the wastage, needing the length reducing binding line.For this reason, in the stepped construction of encapsulation, by carrying out grooving process to PCB, chip is in the pcb embedding, make chip surface and PCB surface be in sustained height.For reducing ground return flow path, reduce external interference, the ground being connected to chip both sides is isolated in PCB design process.For reducing the error brought in actual processing, in PCB design process, broaden the microstrip line in encapsulation in advance.

Beneficial effect:

1. holding wire compensating network of the present invention is made up of the microstrip line inductance of the binding line inductance of connecting, microstrip line shunt capacitance and series connection, forms the T-shaped compensating network of a L-C-L, promotes insertion loss and bandwidth performance, reduces design complexities;

2. ground wire resonance compensation network is made up of the binding line inductance of connecting and series connection microstrip line electric capacity, and both series resonances are in operating frequency;

3. can design independently above-mentioned two compensating networks respectively, reduce the complexity of design, reduce design time;

4. in the stepped construction of encapsulation, by carrying out grooving process to PCB, chip is in the pcb embedding, make chip surface and PCB surface be in sustained height, reduce the length of binding line, improve the bandwidth of encapsulation, reduce the wastage;

4. in the process of PCB design, isolate the ground being connected to chip both sides, thus reduce ground return flow path, reduce external interference;

5. in PCB design process, widen the microstrip line in encapsulation in advance, thus reduce the error effect that actual machining brings.

Accompanying drawing explanation

Fig. 1 is encapsulating structure figure of the present invention;

Fig. 2 is encapsulating structure simulated return loss analogous diagram of the present invention;

Fig. 3 is encapsulating structure of the present invention emulation insertion loss analogous diagram;

Fig. 4 is PCB mismachining tolerance schematic diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention done and further explain.

As shown in Figure 1, encapsulating structure of the present invention is produced on the multilayer circuit board of three layers of medium, four layers of metal composition.Wherein the 4th layer of metal is as encapsulation collocation structure layer, and third layer metal is as ground, and the second layer and first layer metal are as chip DC path.For increasing the accuracy designed a model, this encapsulating structure is designed to back-to-back structure, namely middle is embed the chip of PCB, and chip both sides are made up of jointly holding wire compensating network and ground wire resonance compensation network, to be characteristic impedances be on its both sides transmission line of 50 ohm.The 4th layer of metal surface, for the holding wire of centre, by series connection binding line inductance, microstrip line shunt capacitance and series connection microstrip line inductance, the T-shaped holding wire compensating network of a composition L-C-L.For ground wire (being distributed in the upper and lower both sides of M signal line), we achieve ground wire resonance compensation network.It is made up of the binding line inductance of connecting and wider microstrip line (direct-to-ground capacitance as series connection).Two compensating networks can independently design respectively, to reduce the variable needing to optimize, shorten the time of design.Chip in this encapsulating structure, for characteristic impedance is the silica-based CPW core sheet of 50 ohm.By to PCB grooving, chip is in the pcb embedding, make chip surface and PCB surface be in sustained height, reduce the length of binding line.In the design, by isolating the ground on chip both sides, ground return flow path can be reduced, reduce external interference.

Fig. 2, Fig. 3 are respectively the S parameter simulation result of encapsulating structure.Fig. 2 is the result of its return loss, and its-10dB bandwidth is 45GHz-68.5GHz.For centre frequency 60GHz, its relative bandwidth is 39.2%.Fig. 3 is the simulation result of insertion loss, and it is smaller at whole bandwidth internal loss.Under 60GHz frequency, the loss of encapsulation interconnect architecture itself is only about 0.4dB.Above results proved that beneficial effect of the present invention.

Fig. 4 is the schematic diagram of its tangent plane after actual PCB processes, micro belt line width when wherein W2 is design.But in actual PCB processing because PCB processing technology to cause the microstrip line of rectangle finally to become trapezoidal.The width of microstrip line diminishes as W1, therefore needs to widen designed microstrip line in advance.Namely according to process characteristic, a certain amount of compensation width is respectively added on microstrip line both sides respectively.

Claims

1. the millimeter wave encapsulating structure of a low cost low-loss band ground compensation, it is characterized in that, adopt the stepped construction of PCB, using the 4th layer of metal and third layer metal as encapsulating structure main body, its 4th layer of metal comprises holding wire compensating network and ground wire resonance compensation network; Third layer metal is as stratum, and be the reference ground on whole pcb board, the ground on third layer metal both sides will separate, at the chip distribution direct current of second layer metal and first layer metal and the cabling on ground; Wherein, described chip, by the groove that is embedded into PCB and offers, makes the height of chip surface consistent with PCB apparent height.

2. the millimeter wave encapsulating structure of low cost low-loss band ground compensation according to claim 1, it is characterized in that, described holding wire compensating network is made up of three parts: the binding line be connected with chip as series inductance, the wider microstrip line that is connected with binding line as direct-to-ground capacitance in parallel, thinner microstrip line as series inductance; Three above-mentioned parts form the compensating network of a L-C-L jointly; The microstrip line that this compensating network is 50 ohm by characteristic impedance is drawn.

3. the millimeter wave encapsulating structure of low cost low-loss band ground compensation according to claim 1, it is characterized in that, described ground wire resonance compensation network is made up of two parts: the binding line be connected with chip as series inductance, the microstrip line that is connected with binding line as the direct-to-ground capacitance of connecting; Above-mentioned two parts form a LC series resonant network jointly.

4. the millimeter wave encapsulating structure of low cost low-loss band ground compensation according to claim 1, is characterized in that, isolate the ground on PCB both sides in described encapsulating structure, to reduce ground return flow path.

5. the millimeter wave encapsulating structure of low cost low-loss band ground compensation according to claim 1, is characterized in that, widen the microstrip line in described PCB in advance, to reduce mismachining tolerance impact.