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$N$ -path true time delay (TTD) circuits are highly attractive due to their high delay-bandwidth product, wideband response, scalability, and small size. However, in its standalone form, it cannot provide wideband input and output matching. To overcome these issues, we present a modified circuit of the $N$ -path TTD that includes an input low-noise amplifier (LNA) and an output buffer. The $N$ -path TTD response and its nonideal properties are analyzed further. A design guide is suggested, and an alternative isolated sampling switch is proposed. We present a 65-nm CMOS dedicated implementation, where the fine-tuning of the TTD is achieved by introducing two synchronized external local oscillator (LO) signals, with a relative shift between them. The core chip size is $0.32 \,\times \,0.575$ mm2, and its power consumption is 30 mW for all delay states. In our implementation, we achieve a delay range of 1 ns for bandwidth (BW) of 0.2–3 GHz with a gain standard deviation (STD) of less than 0.14 dB between delay states and a relative delay STD of less than 10 ps (1%) over frequency. [ABSTRACT FROM AUTHOR]

The N-path circuit serves both as a mixer and as a radio frequency (RF) filter. Certain performance aspects, such as noise, linearity, and out-of-band (OOB) rejection dictate large switches size. However, such increment raises the value of the parasitic RF capacitance, which causes further in-band (IB) loss and peak frequency shift. In this brief, we derive simplified equations for the assessment of the mentioned non-ideal properties, using the novel linear periodically time-variant (LPTV) state-space analysis, by making derivations and approximations based on realistic circuit parameters. We present closed-form equations for the voltage gain peak frequency shift and a revised linear time-invariant (LTI) model for the assessment of $S_{11}$ dip frequency shift. [ABSTRACT FROM AUTHOR]

This brief suggests a new method for analyzing the effects of nonideal properties of CMOS switches on N-path filters by expanding the linear periodically time-variant (LPTV) method to state space equations. The proposed technique provides an algorithm for analytical derivation of the harmonic transfer functions (HTF) and the noise figure (NF) of the N-path filter across all frequencies and harmonics. The analysis results show that for constant switch resistance and shunt capacitance product, a trade-off exists between out of band rejection, NF and insertion loss. [ABSTRACT FROM AUTHOR]