Research And Design Of High-precision Digital Control Analog True Time Delay Line Circuit

The true-time delay circuit(TTD)has been widely used in the electronic communication systems.The main function of it is to provide a delay for the signal to meet the requirements in the time domain or phase.With the advancement of semiconductor processing technology,the TTD circuit with analog active structure has attracted researcher's widespread attention for its advantages such as small chip area,easily integrated,the simple structure and so on.For example,in the application of phased array radar beamforming,the analog TTD circuit has significant advantages in its bandwidth and delay precision.If use TTD circuit to replace the phase shifter of the traditional phased array radar beamforming array,it can avoid the"aperture effect"effectively and reduce the"transit time",besides it also improves the communication capacity and anti-jamming capability of the phased array radar system,and improve the radar performance.With the advent of the 5G communication era,it is of great significance to develop an analog active TTD circuit with high delay precision based on CMOS technology.Based on the key indicator of“high precision”,this study designed a high-precision digitally controlled analog true-time delay line circuit for beamforming and biomedical imaging.The entire circuit adopts a"coarse adjustment+fine adjustment"architecture.The fine adjustment module determines the delay precision of the circuit,and the coarse adjustment module expands the delay range of the circuit.Among them,the fine adjustment module and the coarse adjustment module are respectively cascaded by 8corresponding"basic delay unit+path selection switch"structures,and the path selection switch is adjusted by the digital control module.A thermometer style is used to decode between the input and output signals of the 3bit digital control circuit.The output level of it controls the working state of each path selection switch in the circuit,so the delay of the circuit is controlled by adjusting the number of basic delay units in the signal path.The digital control module is designed with the standard CMOS logic gate structure and implemented with high threshold(hvt)transistors to reduce the static power consumption.The basic delay unit and the path selection switch use the active inductor parallel peaking structure as load to expanding the bandwidth of circuit,besides,because the circuit avoids the use of passive inductors effectively,the chip area is reduced.The circuit is designed by 40 nm process,and the core area of the chip layout is about 0.043 mm~2.The post simulation results of the designed digital control analog active true-time delay line show that under the TT mode,the delay of the basic fine-tuning delay unit is 1.37ps,and its working frequency is in the range of 0.4GHz?1GHz,and The maximum group delay deviation in the band is 8.02%.The single-stage gain is about 0.2d B;The delay of basic coarse delay unit is about 10.65ps,which is about 8 times the delay of the basic fine delay unit to meet the monotonous and uniformly adjustable characteristics of the delay line circuit,the single-stage gain of it is about 0.16d B.The delay range of the overall delay line circuit is about0?83.2ps,the group delay deviation is kept within 10%,and under different control signal states,the overall gain of the circuit is more than-7d B,and contented the requirement of amplitude.The input and output of the circuit are well matched and the parameters of S11 and S22 are less than-22d B and-30d B respectively.The circuit isolation is very good.The designed high precision numerical control analog active true-time delay line circuit meets the requirements of the expected index.