Abstract
In recent years number of Internet of Things (IoT) services and devices is growing and Internet of Vehicles (IoV) technologies are emerging. Multiband transceiver with high performance frequency synthesisers should be used to support a multitude of existing and developing wireless standards. In this paper noise sources of an all-digital frequency synthesiser are discussed through s-domain model of frequency synthesisers, and the impact of noise induced by main blocks of synthesisers to the overall phase noise of frequency synthesisers is analysed. Requirements for time to digital converter (TDC), digitally controlled oscillator (DCO) and digital filter suitable for all-digital frequency synthesiser for IoT and IoV applications are defined. The structure of frequency synthesisers, which allows us to meet defined requirements, is presented. Its main parts are 2D Vernier TDC based on gated ring oscillators, which can achieve resolution close to 1 ps; multi core LC-tank DCO, whose tuning range is 4.3–5.4 GHz when two cores are used and phase noise is −116.4 dBc/Hz at 1 MHz offset from 5.44 GHz carrier; digital filter made of proportional and integral gain stages and additional infinite impulse response filter stages. Such a structure allows us to achieve a synthesiser’s in-band phase noise lower than −100 dBc/Hz, out-of-band phase noise equal to −134.0 dBc/Hz and allows us to set a synthesiser to type-I or type-II and change its order from first to sixth.
Highlights
Wireless technologies and services based on these technologies have been spreading rapidly in recent years: coverage of 4G networks increases, 5G technologies are being developed, local area networks are advancing and wireless network at home, workplace and public places is a necessity.The number of Internet of Things (IoT) devices and personal wireless gadgets is rapidly growing
Such transceivers are used in software defined radio, which is becoming more popular in the light of fast developing wireless technologies due to one of its main ideas—the usage of the same hardware for the implementation of different wireless standards, which enables a fast adaptation of the existing equipment to new and developing technologies while reducing the price of the system [3]
Noise induced by to digital converter (TDC) and digitally controlled oscillator (DCO)’s noise have separate dominance ranges—noise induced by TDC
Summary
Wireless technologies and services based on these technologies have been spreading rapidly in recent years: coverage of 4G networks increases, 5G technologies are being developed, local area networks are advancing and wireless network at home, workplace and public places is a necessity. There is a lack of research regarding parameter estimations of all-digital frequency synthesisers and their main blocks, especially for applications in the fields of IoT and IoV. Main of phase detector a time to digital converter (TDC), which measures intervals between edges of reference and DCO signals. As is seen from Equations (1) and (3), the quantization noise of TDC and DCO decreases with increased reference frequency and ∆Σ dithering frequency (in case of DCO) Increasing these frequencies will increase power consumption of the system, which is undesirable in IoT and. Where Hcl,REF , Hcl,TDC , Hcl,DCO , are respectively closed-loop transfer functions of reference signal noise, TDC quantization noise and oscillator’s component of DCO noise, whose s-domain representations are shown in Equations (5)–(7) [15].
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