RF Signal Transmission Research Articles

Characteristics of the Phase Noise Correlation of Injection Locked Lasers for RF Signal Generation and Transmission

Theoretical and experimental results on phase noise characteristics of an optical radio-frequency generation and transmission system using heterodyne photo-detection and side band injection locking is reported. Optical phase noise correlation of the lasers is achieved by noise transfer from a modulated master laser. Our investigation takes into account phase noise enhancement in optical comb generation, injection dynamic, path delay, and fiber dispersion. Theoretical expressions are derived from an adiabatic approximation and compared with experimental measures.

Proposal of photonic frequency-conversion method using bandpass sampling in multicarrier operated radio-on-fiber link

Recently, IF-band RF signal transmission over the fiber using optically supported upconversion/downconversion has attracted much attention, as it can avoid signal deterioration due to a dispersion effect, and a low-cost radio base station can be realized without using any RF mixer. The frequency shifting using the bandpass sampling is one of the candidates for frequency conversion of RF signals. This paper proposes an application of frequency shifting using bandpass sampling in a multicarrier-operated radio-on-fiber link. All multiband RF services in a radio-on-fiber link can be modulated and demodulated using by the IF-band MODEM at the control station in the multicarrier operation environment. When multiband RF signals are simultaneously frequency converted to distinct IF band, signal deterioration due to spectrum overlap is a serious problem. In this paper, an undesired alias suppression method without additional signal processing in the receiver is proposed. As a result of experimental investigation, the symbol error rate is improved from 0.5 to 0.003 in case of the received optical power of -23 dBm.

K-Band Monolithic InGaP–InGaAs DCFET Amplifier Using BCB Coplanar Waveguide Technology

A K-band (20 GHz) monolithic amplifier was developed and fabricated by adopting a low-/spl kappa/ benzocyclobutene (BCB) coplanar waveguide (CPW) line and InGaP-InGaAs doped-channel HFETs (DCFETs). This monolithic microwave integrated circuit (MMIC) utilizes a high impedance BCB CPW microstrip line (Z/sub 0/=70 /spl Omega/) for the biasing circuits, and a Z/sub 0/=50 /spl Omega/ line for the RF signal transmission. The low dielectric constant characteristic of the BCB interlayer is beneficial for a common-ground bridge process, which reduces the parasitics. The calculated loss tan/spl delta/ is 0.036 for the BCB at 20 GHz. The one-stage MMIC amplifier achieves an S/sub 21/ of 5 dB at 20 GHz, which is the first demonstration of the K-band InGaP-InGaAs DCFET monolithic circuit.

Analysis of nonlinear effects in subcarrier‐multiplexed fiber‐optic links for CDMA RF signal transmissions

AbstractIn this letter, we propose an analytic model for performance analyses of the optical subcarrier‐multiplexing (SCM) fiber‐optic link for CDMA RF signal transmission in mobile communication networks. We present optimal operational conditions, taking account of the nonlinear effects of the optical transmission link, and the multiple‐access interference produced at the wireless environment. It is shown through BER analyses in this letter that the selection of an optical modulation index (OMI) of the SCM fiber‐optic links can be found optimally to minimize the fiber‐optic noises and intermodulation distortion due to a laser diode (LD). © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 37–40, 2001.

Expressions for nonlinear effects of MEMS switch beam oscillations

MEMS switches with a beam that is free to move during RF signal transmission have nonlinear transfer functions, due to variations in the capacitance between the beam and the underlying transmission line. Expressions for the relative magnitude of modulation and intermodulation products are presented.

Millimeter wave, multigigahertz optical modulation by feedforward phase noise compensation of a beat note generated by photomixing of two laser diodes

A technique is described for high frequency (up to 100 GHz), narrowband ( approximately GHz) optical modulation by encoding the millimeter-wave signal onto a beat note produced by photomixing of radiation from two 1.3 mu m DFB lasers. The phase noise on the beat note is compensated by a feedforward technique, using a low-frequency external optical modulator which simultaneously encodes the information to be transmitted. The modulation band can be tuned by varying the lasing frequency of one or both of the lasers. The fundamental performance limit of this technique is investigated, and the transmission of a pulsed RF signal at 40 GHz is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Amplification of a bi-phase shift-key modulated signal by a mm-wave FEL

Abstract Bi-phase shift keying (BPSK) is a modulation scheme used in communications and radar in which the phase of a transmitted rf signal is switched in a coded pattern between discrete values differing by π radians. The transmitted information rate (in communications) or resolution (in imaging radar) depends on the rate at which the transmitted signal can be modulated. Modulation rates of greater than 1 GHz are generally desired. Although the instantaneous gain bandwidth of a mm-wave FEL amplifier can be much greater than 10 GHz, slippage may limit the BPSK modulation rate that can be amplified. Qualitative slippage arguments would limit the modulation rate to relatively low values; nevertheless, simulations with a time-dependent FEL code (GINGER) indicate that rates of 2 GHz or more are amplified without much loss in modulation integrity. In this paper we describe the effects of slippage in the simulations and discuss the limits of simple slippage arguments.

Time-Jitter Reduction on the RF Buncher Signal for the los Alamos Proton Storage Ring (PSR)

The PSR at LAMPF will accumulate protons from the linear accelerator in both long-and short-bunch operational modes. Beam accumulation takes place for hundreds or thousands of turns. Ring buncher frequencies for these modes are 2.795 and 503.125 MHz, respectively. The bunching waveforms must be accurately correlated with the linac frequency standard so that the injected bunches fall into the ring rf buckets at precisely zero phase angle during accumulation. The PSR's rf wave also must have excellent phase stability. Long-term stability is assured by locking the PSR frequency reference to the linac's low-noise, temperature-stabilized crystal standard and by using delay-correction circuits in the transmission-line paths. However, the short-term stability of the rf reference signal is not as easily controlled because additive spurious signals can enter the long rf-signal transmission path (1-km linac-to-PSR), causing sideband energy increases very close to the carrier frequency. This increases time jitter. Also, some phase noise is spuriously developed by the signal-processing circuits providing frequency multiplication and division, the required processes for generating the necessary harmonic and subharmonic bunching frequencies at 503.125 and 2.795 MHz, respectively. The measure of control pursued by the described circuit design will provide rf references with timing uncertainty much less than the expected uncertainty in the micropulse time of arrival at the ring, ΔT ≈ ±80 ps.

Navigation system and method for determining the position of an ocean mining ship

A system for determining the position of a ship in relation to predetermined positions on the ocean floor is disclosed. A plurality of first acoustic addressable transponders and a plurality of second acoustic addressable transponders are respectively located at first and second sets of predetermined positions on the ocean floor. Each of the acoustic transponders transmits an acoustic ranging response and identification signal in response to receipt of an acoustic ranging interrogation signal. First and second buoy communications systems are located on first and second buoys respectively moored to the ocean floor in the vicinity of the first and second pluralities of acoustic transponders. Each buoy communication system includes an acoustic communications devices for transmitting an acoustic ranging interrogation signal to the respective acoustic transponders in its vicinity and for receiving acoustic ranging response and identification signals from such acoustic transponders in response thereto; a buoy RF communications device for transmitting RF signals containing information representative of the respective propagation delays between transmission of the acoustic ranging interrogation signal and receipt of the acoustic ranging response and identification signals from the acoustic transponders; and a buoy RF addressable transponder for transmitting an RF buoy ranging response and identification signal in response to receipt of an RF ranging interrogation signal. A ship communications system located on the ship transmits the RF ranging interrogation signals and receives the RF buoy ranging response and identification signals in response thereto. The ship communications system also transmits command signals. The first and second buoy communications systems each respond to the command signal by transmitting the acoustic interrogation signals to the acoustic transponders. The ship communications system receives the RF signals containing the acoustic propagation delay information. A data processing system processes the received RF signals in relation to the transmitted RF ranging interrogation signals to determine the position of the ship in relation to the first and second sets of predetermined positions on the ocean floor.