Design Of Wideband VCO For Multi-mode Multi-standard Receiver

In order to adapt to the development of the wireless communications, developing a RF transceiver to support a variety of wireless communication standard is a hot spot in the industry and academia at home and abroad. Frequency synthesizer is the heart of the transceiver, which needs to supply very wide frequency range to cover a variety of different wireless communication standards’ work frequencies, at the same time also need to reach a certain phase noise index to satisfy the requirement of the wireless communication standard. VCO (Voltage Controlled Oscillator) is one of the most important modules in frequency synthesizers, determining the range of frequencies and phase noise performance of the band, therefore, the design of VCO is of great concern to many researchers in many years.This thesis presents the existing restricting factors in the design of wideband LC VCO based on the analysis of the Phase-Locked Loop(PLL) and VCO, and then introduces the commonly used wideband VCO structures, on this basis, this paper discusses the design principles and optimal method of wideband VCO which is based on transformer, the two kinds of topological structure and its performance specifications have been carried on the detailed analysis and discussion. At the same time, considering the frequency tuning range, phase noise, power consumption and other factors, the on-chip transformer is modeled and simulated by using ADS Momentum. Finally based on TSMC 0.18 mu m CMOS process, two wideband voltage-controlled oscillators(VCOH and VCOL) applied in multimode standard receiver are designed.The layout design is completed by using Cadence Virtuoso tool. The two VCO chips occupy an area of 1084μm 616μm and 1420μm 710μm respectively. With 1.8V supply voltage, the post-simulation results show that the frequency range the VCOH can cover is 4.00～7.76GHz and the phase noise at 1MHz offset is less than-109dBc/Hz, the frequency range the VCOL can cover is 1.40～4.05GHz and the phase noise at 1 MHz offset is less than-115dBc/Hz. This guarantees the continuous coverage of the frequency range from 1.4-7.6GHz, and the phase noise meet the expectation. The operating current of two VCO is less than 15mA.Two VCO cores have been taped out, and the measure results show that their tuning range is 3.40-7.30GHz and 1.20～4.00GHz respectively. But some adjacent band doesn’t overlap. The phase noises of two VCOs are lower than -90dBc/Hz@ 1 MHz and -94dBc/Hz@1MHz respectively in the best case, which meet the most design requirements. The phase noises of two VCOs are-80dBc/Hz@1MHz and-84dBc/Hz@1MHz respectively in the worst case, so the performance in terms of phase noise is not satisfying in some circumstances. Their current consumption are 10.1～14.0mA and 8.9～13.3mA respectively.