Local oscillator

Résumé

In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input signal. Processing a signal at a fixed frequency gives a radio receiver improved performance. In many receivers, the function of local oscillator and mixer is combined in one stage called a "converter" - this reduces the space, cost, and power consumption by combining both functions into one active device. Applications Local oscillators are used in the superheterodyne receiver, the most common type of radio receiver circuit. They are also used in many other communications circuits such as modems, cable television set top boxes, frequency division multiplexing systems used in telephone trunklines, microwave relay systems, telemetry systems, atomic clocks, radio telescopes, and m

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https://en.wikipedia.org/wiki/Local_oscillator

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This paper presents the design of an impulse radio ultra-wideband (IR-UWB) transmitter for low-power, short-range, and high-data rate applications such as high density neural recording interfaces. The IR-UWB transmitter pulses are generated by modulating the output of a local oscillator. The large area requirement of the spiral inductor in a conventional on-chip LC tank is overcome by replacing it with an active inductor topology. The circuit has been fabricated in a UMC CMOS 180 nm technology, with a die area of 0.012 mm2. The temporal width of the output waveform is determined by a pulse generator based on logic gates. The measured pulse is compliant with Federal Communications Commission (FCC) power spectral density limits and within the frequency band of 3-6 GHz. For the minimum pulse duration of 1 ns, the energy consumption of the design is 20 pJ per bit, while transmitting at a 200 Mbps data rate with an amplitude of 130 mV.

2018

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Read Range Limitation in IF-Based Far-Field RFID Using ASK Backscatter Modulation

Michel Declercq, Catherine Dehollain, Nicolas Pillin

A model is proposed to describe the fundamental read range limitation due to the local oscillator phase noise in the reader, in IF-based, far-field RFID systems using amplitude-shift keying backscatter modulation. The relation between the system parameters (such as the data transfer rate) and the read range is discussed. The model is validated by measurements done on two different laboratory tag-reader systems.

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

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Vacuum field Rabi splitting in a semiconductor microcavity

Romuald Houdré, Ursula Oesterle

We do not intend to give here a background knowledge on vacuum field Rabi splitting. The reader should refer to J.M. Raimond, T. Norris, H. Yokoyama and D.S. Citrin lecture notes. For the sake of completeness we simply remind the reader that the cavity quantum electrodynamics (CQED) treatment of a two level atomic system resonantly coupled to a single photon mode predicts that the eigenstates of the system are no longer the photon and atomic oscillator states but two mixed symmetric and anti symmetric states. The energy separation is Δn=ℏΩ=g1‾√+n where g is a coupling factor that only depends on the dipole matrix element and the cavity volume , and n is the number of photons in the cavity1. For no incoming photons, a splitting still occurs, which can be regarded as coupling between the atomic oscillator and the vacuum field of the cavity (i.e. in the absence of a driving field). This effect was first called vacuum field Rabi splitting by J. J. Sanchez-Mondragon et al.1 as it is related to the textbook case of intense field Rabi splitting2 which, in the present case, is induced by the zero point field fluctuations in the cavity. If several atomic oscillators are present it can be shown3 that, for the n=0 states, the coupling constant increases as the square root of the number N of atoms gn = 0(N)=g(1)N‾‾√. If the system is prepared in a pure atomic oscillator or photon oscillator state, it will oscillate between these two states at the Rabi frequency Ω. In a classical description, the overall system exhibits an anti-crossing behavior when both oscillators are resonant, with the two split modes corresponding to the normal modes of the system4. In an atomic transition language, one considers the system as undergoing a coherent evolution with a photon being absorbed by an atom, which subsequently emits a photon with the same energy and wave vector k, the photon being re-absorbed, and so-on. In order to observe a similar effect in a solid we need the equivalent of both atomic and photon oscillators, both of which can be obtained in a monolithic semiconductor structure.

Plenum1995

Chargement

Vacuum field Rabi splitting in a semiconductor microcavity

Romuald Houdré, Ursula Oesterle

Plenum1995