A 24-GHz novel true-time-delay phase shifter utilizing negative group delay compensation

A wideband TTD (true time delay) phase shifter based on a novel method of negative group delay compensation is proposed for 24.25-26.65-GHz automotive radar application. It is designed and fabricated in TSMC 65-nm CMOS-LP technology. Double bonding is applied to the COB-packaged chip and the test board is connected to a network analyzer for measurement. For an instantaneous bandwidth of 1.5-GHz, its maximum relative group delay is 17-ps and the variation of relative group delay is 3.5-ps. The resolution of relative time delay is equivalent to a 6 bit phase shifter at 25.5-GHz with a maximum phase shift angle 60 degree. The TTD phase shifter achieves a loss of 23-dB at 25.9 GHz and a noise figure of 28-dB at 24.4-GHz. The S11 and S22 are less than -10dB. The IIP3 is -0.7-dBm at 25-GHz. At a supply voltage of 1.2-V, it consumes 12-mA current. The chip area is only 695*390 μm
²
excluding the test pads. Though performances degrade, the feature of true-time-delay tuning is proved. The lack of design experience and inaccurate modeling of test bench including ESD pads, bondwires, PCB traces, etc. will be improved in the subsequent design version and the proposed circuit will be proved to be a considerable alternative for high resolution and compact design of millimeter-wave TTD phase shifter.