Frequency separation

Abstract: In this paper we will present a low-phase-noise wide-tuning-range oscillator suitable for scaled CMOS processes. It switches between the two resonant modes of a high-order LC resonator that consists of two identical LC tanks coupled by capacitor and transformer. The mode switching method does not add lossy switches to the resonator and thus doubles frequency tuning range without degrading phase noise performance. Moreover, the coupled resonator leads to 3 dB lower phase noise than a single LC tank, which provides a way of achieving low phase noise in scaled CMOS process. Finally, the novel way of using inductive and capacitive coupling jointly decouples frequency separation and tank impedances of the two resonant modes, and makes it possible to achieve balanced performance. The proposed structure is verified by a prototype in a low power 65 nm CMOS process, which covers all cellular bands with a continuous tuning range of 2.5-5.6 GHz and meets all stringent phase noise specifications of cellular standards. It uses a 0.6 V power supply and achieves excellent phase noise figure-of-merit (FoM) of 192.5 dB at 3.7 GHz and >; 188 dB across the entire tuning range. This demonstrates the possibility of achieving low phase noise and wide tuning range at the same time in scaled CMOS processes.

Abstract: The internal modulation of lasers by a variation of cavity losses is analyzed in terms of the normal modes of the system Time‐dependent perturbation theory is used to describe the results of resistive mode coupling when the losses are modulated with small signals For the single‐mode oscillator, an expression is obtained for the amplitude distortion in the modulation index of the light produced by a coupling‐type internal modulator when the losses are modulated at a frequency commensurate with the separation between longitudinal modes of the laser cavity Low distortion is obtained when the modulating frequency is noncommensurate with the longitudinal‐mode frequency separation The internal coupling‐type modulator in its present form can provide small amounts of modulation over bandwidths limited to the separation between adjacent interferometer cavity normal modesFor a multimode oscillator, modulation of the internal losses at a frequency equal to the separation between adjacent longitudinal modes prod

Abstract: Methods and apparatus for transmitting communications signals that are both power efficient and effective at avoiding or reducing transmitter-generated receive band noise. An exemplary transceiver apparatus includes a multi-mode transmitter that is configurable to operate in a plurality of operating modes (e.g., a polar mode, a quadrature mode and a hybrid mode), a receiver, and an operating mode controller. The operating mode controller is configured to control which operating mode the transmitter is to operate, depending on one or more of a transmit (Tx) power, receive (Rx) power, the Tx power relative to the Rx power, a level of frequency separation between a Tx frequency band and a Rx frequency band (Tx/Rx band separation), and modulation type employed by the transmitter.