CN208353311U - Numerical-control attenuator based on capacitance compensation - Google Patents

Abstract

The utility model discloses a kind of attenuators based on capacitance compensation, the attenuator includes a transistor switch, a parallel connection damping resistance, an open circuit line capacitance and matched transmission line in parallel, and the attenuator realizes the control of relative attenuation using switching attenuation state and pass-through state；This attenuator structure is simple, and area occupied is small, and spurious phase modulation, attenuation characteristic bandwidth are good, has great advantages and application space in monolithic integrated optical circuit application.

Description

Numerical-control attenuator based on capacitance compensation

Technical field

The utility model relates to attenuator fields, more specifically, it is related to the numerical-control attenuator based on capacitance compensation.

Background technique

Attenuator is the important component of Controller Circuit Used in Microwave Power Amplifier, for realizing the control to radio frequency signal amplitude.It is common Digital control attenuator be made by switching device signal reference state and decaying two states of state between switch, to realize The signal amplitude of predeterminated target decays.Ideally in reference state, attenuator is equivalent to loss-free straight-forward network, and The resistive network with flat amplitude and phase characteristic is equivalent to when the state that decays.(it is less than generally for attenuation amplitude is relatively small Attenuator 2dB) can realize the decaying electricity of an i.e. switch with an earth using a simple attenuating structure in parallel Cascaded structure is hindered, the small control of the structural area is simple, insertion loss is small, amplitude flatness is preferable.But due to switching transistor The presence of parasitic capacitance makes attenuator there is parasitic phase shift under different conditions to generate spurious phase modulation, and such case is especially It is affected under high-frequency work.

For the attenuator spurious phase modulation of the above-mentioned small pad value of tradition can by the adjustment of switching-transistor size into Row improves, but this mode needs transistor switch to possess accurate model under different sizes, so that design cost is increased, The flexibility of design is reduced, and this performance that can also sacrifice decaying flatness increases loss and spurious phase modulation improvement is limited.

Summary of the invention

The utility model overcomes the deficiencies in the prior art, provides the numerical-control attenuator based on capacitance compensation, reduces split The requirement of transistor size is closed, loss, the spurious phase modulation of flexible compensation digital pad are reduced.

The technical solution of the utility model is as follows:

Numerical-control attenuator based on capacitance compensation, including transistor switch, resistance, capacitor and matched transmission line, transistor One end connection of one end, capacitor of the source electrode and resistance of switch, resistance and capacitor are in parallel, the other end ground connection of resistance；Matching passes Defeated line has two sections, wherein the input terminal of one end of one section of matched transmission line and attenuator connects, the one of another section of matched transmission line End is connect with the output end of attenuator, and the drain electrode of the other end and transistor switch of two sections of matched transmission lines connects.

Further, transistor switch includes the transistor of the N-shaped field-effect based on triple-well process, first resistor, second Resistance and 3rd resistor；One end of first resistor and the substrate terminal of transistor connect, the other end ground connection of first resistor；Second electricity One end of resistance and the N trap end of transistor connect, the VCC connection of the other end and circuit of second resistance；One end of 3rd resistor with The grid of transistor connects, and the other end of 3rd resistor is connect with switch control signal end.

Further, the high level at switch control signal end is 1.5 volts, and low level 0V, VCC are 1.5 volts.

Further, the width of two sections of matched transmission lines and length are all identical.

Advantage is the utility model compared with prior art: the utility model realizes a kind of additional phase shift capacitance compensation number Word attenuator circuit reduces the requirement to switching-transistor size, reduces loss, and the parasitic of flexible compensation digital pad is adjusted Phase.

Detailed description of the invention

Fig. 1 is the electrical block diagram of the utility model；

Fig. 2 is the schematic diagram of the integrated circuit mmic chip of the utility model；

Fig. 3 is that simulated performance results figure is lost in the straight-through state of the 1dB attenuator of the utility model and decaying state；

Fig. 4 is the straight-through state and decaying state reflection coefficient simulated performance results figure of the 1dB attenuator of the utility model；

Fig. 5 is the relative attenuation characteristic Simulation result figure of the 1dB attenuator of the utility model；

Fig. 6 is the spurious phase modulation simulation result diagram of the 1dB attenuator of the utility model.

Specific embodiment

The embodiments of the present invention is described below in detail, in which the same or similar labels are throughly indicated identical Or the element of similar element or similar functions.It is exemplary, is only used for below with reference to the embodiment of attached drawing description It explains the utility model and cannot function as limitations of the present invention.

Those skilled in the art can understand that unless otherwise defined, all terms used herein (including skill Art term and scientific and technical terminology) there is meaning identical with the general understanding of those of ordinary skill in the utility model fields Justice.It should also be understood that those terms such as defined in the general dictionary should be understood that with upper with the prior art The consistent meaning of meaning hereinafter, and unless definition as here, will not use idealization or meaning too formal To explain.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in figures 1 to 6, based on the numerical-control attenuator of capacitance compensation, including transistor switch FET1, resistance R1, electricity Hold Tline3 and matched transmission line, the source electrode of transistor switch FET1 connect with one end of one end of resistance R1, capacitor Tline3, Resistance R1 and capacitor Tline3 are in parallel, and the other end ground connection of resistance R1, pad value is provided by resistance R1, resistance R1 and crystal The series connection of pipe switch FET1, to realize the switching of attenuation state and straight-through state by transistor switch FET1 on-off.Resistance R1 It is in parallel with capacitor Tline3, attenuator spurious phase modulation is reduced by capacitor Tline3.

Matched transmission line has two sections, and the width and length of two sections of matched transmission lines are all identical.Wherein one section of matched transmission line One end and the input terminal of attenuator connect, one end of another section of matched transmission line and the output end of attenuator connect, two sections The other end with transmission line is connect with the drain electrode of transistor switch FET1.Tline1, Tline2 as shown in fig. 1 are two sections of matchings Transmission line, the identical matching series connection microstrip line of Length x Width, Tline3 is capacitor Tline3, is played by open circuit microstrip line The effect of compensating electric capacity Tline3, capacitor Tline3 are used for phase shift of the compensated attenuator under attenuation state.In silicon-based substrate Upper processing, the specific length and width of matched transmission line will determine according to working frequency, dielectric constant, circuit performance optimization design It is fixed, while the position considered each element in circuit and interconnection demand also being needed to be adjusted.The reference planes of microstrip line It is chosen according to the convenience of layout and the characteristic impedance demand of microstrip line.Microstrip line metal can be by using the gold of different resistivity Belong to layer to realize the open circuit line capacitance Tline3 of different quality factors to reduce while compensating phase shift to decaying flatness It influences.

Transistor switch FET1 includes the transistor of the N-shaped field-effect based on triple-well process, first resistor R3, second resistance R4 and 3rd resistor R2.One end of first resistor R3 and the substrate terminal of transistor connect, the other end ground connection of first resistor R3, from And realize floating gate function, the impedance of first resistor R3 is significantly larger than the impedance of channel capacitance in transistor, therefore its size needs It is moderate.One end of second resistance R4 and the N trap end of transistor connect, the VCC connection of the other end and circuit of second resistance R4, from And the diode for constituting a reverse bias increases substrate isolating power.One end of 3rd resistor R2 and the grid of transistor connect It connecing, the other end of 3rd resistor R2 is connect with switch control signal end, thus realize being isolated for control signal and radiofrequency signal, and The conducting and cut-off for realizing transistor by the low and high level switching of switch control signal are to realize on-off action.First resistor The impedance of R3, second resistance R4 and 3rd resistor R2 will be much larger than the impedances of channel capacitance in transistor, therefore its size needs Want moderate, in addition to this resistance value of first resistor R3, second resistance R4 and 3rd resistor R2 are excessive will affect transistor switch The switching speed of FET1 effect, trades off according to switching speed demand and chooses resistance value.The size of transistor influences parasitic capacitance and posts Raw resistance, the size of transistor need to be greater than technique minimum channel length an order of magnitude, but conducting resistance under its open state Need to be less than damping resistance an order of magnitude, choose suitable grid instigate the ft of transistor can be higher to obtain preferable device Characteristic.It include that standing wave, insertion loss, decaying flatness, spurious phase modulation optimize to obtain transistor according to attenuator overall performance Size and grid index.

The tantalum nitride resistance that damping resistance R1 selects operational characteristic relatively stable, resistance value are tentatively true according to the size of pad value It is fixed, it include that standing wave, insertion loss, decaying flatness, spurious phase modulation optimize to obtain specific electricity further according to attenuator overall performance Hinder the size of R1.

In design, the value of resistive network impedance, reallocation parallel resistance are first calculated by the pad value that decaying position needs The resistance value of the conducting switch of the resistance value and transistor switch FET1 of R1, primarily determines transistor size and parallel resistance R1, is used in combination Realistic model is replaced to obtain parasitic influence, and further emulation adjustment transistor size and resistance R1 resistance value are to meet needs Pad value.Then primarily determine the length of series connection microstrip line to reduce the return loss of attenuator by electromagnetic-field simulation.Addition Compensating electric capacity Tline3 open circuit microstrip line in parallel is to reduce spurious phase modulation.Each device parameters are finally finely tuned, whole electricity is carried out Magnetic field simulation optimization, and draw domain according to actual needs and determine each device placement position.

Preferably, the high level at switch control signal end is 1.5 volts, low level 0V, VCC are 1.5 volts.Control signal Attenuator attenuation state is opened under high level state, control signal opens attenuator under low level state and leads directly to state.

This programme is using the germanium silicon material technological design attenuator of one 1dB pad value, but the realization of attenuator is unlimited In the technique, by taking small pad value attenuator as an example, but it is not limited only to small pad value attenuator, for the attenuator of other structures It again may be by introducing compensating electric capacity to reduce spurious phase modulation.

Each component parameters of specific this programme are as follows: the total grid width of transistor is 30.4um, and grid index is 8, and grid length is 120nm, the big resistance of three of isolation (first resistor R3, second resistance R4 and 3rd resistor R2) is having a size of 1um*8um resistance value It is 13.8 kilohms.Damping resistance R1 is that 6um*30um is 300 ohm.Compensation open-circuit transfer line capacitance Tline3 length is 28um , width 8um.It is 8um that matched transmission line Tline1 and Tline2 length, which is 24um width,.Switch control signal level is 1.5 It lies prostrate and 0 volt.

Circuit topological structure is completed by above-mentioned specification, laying out pattern, attenuator size are carried out according to circuit diagram Are as follows: 160um*76um.Conducting state Insertion Loss is less than 0.3dB in 10GHz-40GHz, and attenuation is that 1dB fluctuation is less than 0.05dB, posts For raw phase modulation less than 0.1 degree, reflection coefficient is less than -18dB, and control voltage is 0/1.5 volt.Originally according to simulated performance results figure The electric property of scheme is stablized, and loss is greatly reduced.

The above is only the preferred embodiment of the utility model, it is noted that for the common skill of the art Art personnel can also make several improvements and modifications without departing from the concept of the premise utility, these improvements and modifications Also it should be regarded as in scope of protection of the utility model.

Claims (4)

1. the numerical-control attenuator based on capacitance compensation, which is characterized in that including transistor switch, resistance, capacitor and matching transmission Line, one end connection of one end, capacitor of the source electrode and resistance of transistor switch, resistance and capacitor are in parallel, another termination of resistance Ground；Matched transmission line has two sections, wherein the input terminal of one end of one section of matched transmission line and attenuator connects, another section of matching biography One end of defeated line and the output end of attenuator connect, and the drain electrode of the other end and transistor switch of two sections of matched transmission lines connects.

2. the numerical-control attenuator based on capacitance compensation according to claim 1, it is characterised in that: transistor switch packet Include transistor, first resistor, second resistance and the 3rd resistor of the N-shaped field-effect based on triple-well process；One end of first resistor It is connect with the substrate terminal of transistor, the other end ground connection of first resistor；One end of second resistance and the N trap end of transistor connect, The VCC connection of the other end and circuit of second resistance；The grid of one end of 3rd resistor and transistor connects, 3rd resistor it is another One end is connect with switch control signal end.

3. the numerical-control attenuator according to claim 2 based on capacitance compensation, it is characterised in that: switch control signal end High level be 1.5 volts, low level 0V, VCC be 1.5 volts.

4. the numerical-control attenuator based on capacitance compensation according to claim 1, it is characterised in that: two sections of matching transmissions The width and length of line are all identical.