(A) fully integrated TV tuner front-end with linear RF filters and robust harmonic rejection techniques

Abstract

As the global TV tuner standards are emerged into a multi-standard single chip silicon tuner, several challenging issues appear in the RF front-end design. Since the spectrum of the terrestrial and cable TV ranges from 48MHz to 870MHz with simultaneous presence of high power channels, high linearity and harmonic rejection performances are required in RF front-end as well as low noise and wideband performance. In addition, in case of ATSC standard (A/74), the tuner front-end must endure up to 57dB larger taboo channel power than the de-sired. Although, in the past, the external high-Q passive filter in the so-called ‘Can’ tuner cuts out all high-power interferers and thus resolving harmonic mixing and linearity issues at the same time, the implementation of such high-Q and highly-linear filters has been unrealizable in the integrated silicon tuners. Thus, in many of recent researches, the TV tuners were inte-grated at cost of some performance degradation or by using external components for high-Q filter implementation.

To implement a high-Q and highly linear filter in a silicon die, we present a source-follower-based active-RC filter which resolves the stopband limitation problem of the Sallen-Key topology and shows better noise and linearity performance in architecture aspect. In spite of the bandwidth limitation of the typical active-RC filters, the proposed filter topology achieves 48MHz-to-500MHz tuning range in measurement by adopting the proposed sub-1-ohm source follower. The sub-1-ohm source follower allows the filter Q to sustain high enough up to around 1GHz while its linearity keeps higher than the conventional source fol-lowers thus further boosting the filter linearity. The measurement of the $4^{th}$ -order Butterworth filter shows 14dB and +30dBm in its noise figure and IIP3 respectively. By adopting the pro-posed filter the RF filter in the tuner front-end becomes no longer a bottleneck of the front-end linearity performance.

Additionally, an even-order harmonic cancellation technique is proposed in a low noise amplifier (LNA) in order to further improve the front-end linearity. While the LNA is configured in 2-stage shunt feedback topology and each gain cells are based on the differen-tial hybrid voltage follower (DHVF), the proposed technique reduces $3^{rd}$ -order intermodula-tion components of the $2^{nd}$ -order interaction in feedback loops by suppressing the even-order harmonic distortions. In addition, the proposed technique helps to increase the gain of the first stage of the LNA and thus the total loop gain, which again improves LNA linearity with low noise figure. The proposed LNA is designed in 1.4dB NF and >+28dBm OIP3 over 48 to 870MHz bandwidth. Aside from the linearity specifications, the proposed front-end adopts a robust har-monic rejection technique in a current-mode passive mixer. Contrary to the previous RF gain-weighting method, two-stage baseband gain-weighting is applied to the mixer leading to more robust harmonic rejections. The proposed harmonic rejection mixer obtains more than 60dB rejection ratio for $3^{rd}$ - and $5^{th}$ -order harmonics. Besides, at the end of this thesis, a common-centroid latch layout is introduced for accurate LO phase for more robust harmonic rejections. Finally, this thesis presents a fully integrated state-of-the-art performance TV tuner front-end which shows 3.1dB NF, >+31dBm OIP3, >83dB HRR3, >89dB HRR5, and >68dB for HRR7 and higher. In addition, a symmetric latch layout technique is introduced for more robust harmonic rejections