Tracking Circuit Research Articles

Linearity improvement of three‐way Doherty amplifier using power tracking bias supply method

AbstractThis letter presents highly linear three‐way Doherty power amplifier (DPA) using power tracking bias supply method. The drain biases of carrier and peaking amplifiers and the gate biases of peaking amplifiers are adaptively controlled by the power tracking circuit according to average power levels of the input signal. For validation, a three‐way DPA is implemented using 30‐W Si LDMOSFETs and tested for two‐tone and 1‐carrier WCDMA signals at 2.14 GHz. The measured results show the notable linearity improvement over a wide output power range. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 728–731, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23198

Construction and characterization of interferometric fiber optic gyroscope (IFOG) with erbium doped fiber amplifier (EDFA)

Gyroscopes, which sense changes on absolute angular rate and are classified into Interferometric Fiber Optic Gyroscopes (IFOG), Ring Laser Gyroscopes (RLG) and Micro- Electro-Mechanical Systems (MEMS) Gyroscopes, are critical components of the navigation systems together with accelerometers. Being dominant over other types of gyroscopes in terms of performance and cost, IFOGs have widely been used in metrology and in particular defense/aerospace industry. This paper covers the design details of both optical and electronic components of IFOG prototype, the sensing mechanism of which is based on Sagnac Phase Shift, constructed in Optics Laboratory of National Metrology Institute of TURKEY as absolute angular rate sensor. In the prototype IFOG, open-loop configuration was applied, a single mode telecommunication optical fiber and an EDFA pumped by DFB laser emitting at 1549.0 nm were used as sensing coil and broadband source, respectively. The voltage data carrying Sagnac Phase Shift was extracted by a phase tracking circuit consisting of an active RC band pass filter, an amplifier with adjustable gain and an AD630 balanced modulator chip which was operated as lock-in. For the prototype IFOG, peak to peak noise of 8 (°/h) and bias stability of 1.57 (°/h) were attained respectively. Moreover the scale factor of 13.83 (°/h)/mV was derived with deviation of 0.73%.

A Highly Integrated CMOS Analog Baseband Transceiver With 180 MSPS 13-bit Pipelined CMOS ADC and Dual 12-bit DACs

A CMOS analog baseband transceiver with a 13-bit, 180 MSPS pipelined ADC and dual 12-bit, 180 MSPS current-steering DACs is presented. The ADC is implemented without a dedicated track-and-hold stage, utilizes a front-end 2.5-bit stage with matched MDAC/comparator tracking circuits, and demonstrates an ENOB of 10.6 bits at 15 MHz and 9.7 bits at 100 MHz, employing a low-jitter delay-lock loop for its phasing. The dual I/Q DACs show over 62 dB SFDR over the Nyquist band by utilizing a dynamic linearity enhancing architecture

Maximum power point tracker for portable photovoltaic systems with resistive-like load

In this work we report on the design and realization of a maximum power point tracking (MPPT) circuit suitable for low power, portable applications with resistive load. The design rules included cost, size and power efficiency considerations. A novel scheme for the implementation of the control loop of the MPPT circuit is proposed, combining good performance with compact design. The operation and performances were simulated at circuit schematic level with simulation program with integrated circuit emphasis (SPICE). The improved operation of a PV system using our MPPT circuit was demonstrated using a purely resistive load.

A method for designing a tracking system with digital filter in the tracking loop and improved control accuracy

A new method for designing a radioelectronic tracking system with a digital filter incorporated in the tracking circuit is considered. The method permits to synthesize the tracking systems of high precision (high control accuracy), thus providing additional opportunities in tracking the maneuvering objects.

Rotationally invariant space-time trellis codes with 4-D rectangular constellations for high data rate wireless communications

We demonstrate rotationally invariant space-time (ST) trellis codes with a 4-D rectangular signal constellation for data transmission over fading channels using two transmit antennas. The rotational invariance is a good property to have that may alleviate the task of the carrier phase tracking circuit in the receiver. The transmitted data stream is segmented into eight bit blocks and quadrature amplitude modulated using a 256 point 4-D signal constellation whose 2-D constituent constellation is a 16 point square constellation doubly partitioned. The 4-D signal constellation is simply the Cartesian product of the 2-D signal constellation with itself and has 32 subsets. The partition is performed on one side into four subsets A, B, C, and D with increased minimum-squared Euclidian distance, and on the other side into four rings, where each ring includes four points of equal energy. We propose both linear and nonlinear ST trellis codes and perform simulations using an appropriate multiple-input multiple-output (MIMO) channel model. The 4-D ST codes constructed here demonstrate about the same frame error rate (FER) performance as their 2-D counterparts, having however the added value of rotational invariance.

Precise Measurement of Losses in Piezoelectric Transducer and Its Application to Evaluation of Piezoelectric Transformer Efficiency

Mechanical and dielectric losses were measured by the measurement method proposed in this paper in a piezoelectric transducer with input and output terminals. These losses must be considered in designing piezoelectric transformers used as power sources. In the method proposed here, the losses can be obtained using the experimental results of resonance angular frequency, quality factor and the resistive component of input impedance when the output terminals are short-circuited and opened, and using the measured phase angle difference between current and voltage when the output terminals are opened. In the method, a resonance frequency tracking circuit is utilized. Hence, there is an advantage that the measurement can be performed easily and in a short time. The results obtained by this method have also been used in the evaluation of the efficiency of piezoelectric transformers.

A real-time center-of-mass tracker circuit implemented by neuron MOS technology

A new architecture integrated circuit has been developed as a key element of a system that can real-time track the center of mass of an moving image on a two-dimensional (2-D) pixel array. The circuit has been implemented using a high-functionality transistor called neuron MOSFET (neuMOS or /spl nu/MOS for short), hence having a very simple circuit configuration. A quasi-two-dimensional algorithm is assumed for system in the circuit. A one-dimensional (1-D) array of neuron MOS circuits automatically finds the center-of-mass location using the image intensity distribution projected onto the x or y axis. The unique feature of the circuit is that it accepts analog inputs without A/D conversion but produces binary outputs, thus providing a very smooth interfacing between the real world and digital systems. Test circuits have been fabricated by a double-polysilicon CMOS process and their operation has been experimentally demonstrated.

Modulation and coding for mobile radio communications: channels with correlated Rice fading and Doppler frequency shift

We discuss the relative performance of coherent phase-shift keying (PSK), differential PSK (DPSK), and double differential PSK (DDPSK) modulation schemes over a mobile radio channel in which transmission is affected by additive noise, a constant carrier phase offset, a constant Doppler frequency shift, and correlated Rice fading. We first compare the performance of these schemes to assess the amount of degradation caused on each one of them by fading. Among our findings, we observe that DDPSK turns out to be less sensitive to the effects of correlated fading than the other two schemes and that in these conditions interleaving may not be beneficial. We then consider the introduction of trellis-coded modulation (TCM). The system we advocate as offering the best tradeoff between performance and complexity with the channel model assumed here includes double-differential encoding, differential detection, an open-loop Doppler phase tracking circuit, and differential decoding in addition to a simple TCM scheme.

Extreme waveform coding

A circuit and method for representing in digital form information about the time and amplitude characteristic of a time-varying input signal. The time-varying input signal is delayed and the magnitudes of the time-varying input signal and its delayed version are compared to produce a digital signal representing the time characteristic of the input signal in the form of a transition in a digital output signal each time the magnitudes of the compared signals have a predetermined relationship. The predetermined relationship may be a condition of approximate equality or when the magnitude of the larger of the compared signals becomes less than the magnitude of the smaller of the compared signals. The invention also includes a circuit for outputting a digital representation of the amplitude of the time-varying input signal for each transition of said digital output signal. The disclosed circuits thus provide separate digital representations of the time and amplitude of each peak and valley of an analog or other time-varying input signal. The invention also includes an application of the analog-to-digital converter in a pitch tracking circuit.

Radio-frequency-driven electron-spin-echo-envelope-modulation spectroscopy

A pulsed EPR technique for generating electron-spin-echo-envelope modulations in paramagnetic systems that do not contain nonsecular hyperfine interactions is proposed. Strong continuous radio-frequency irradiation tuned to one of the unpurturbed nuclear transition frequencies is shown to provide a mechanism whereby echo modulations may be produced in such systems. A theoretical treatment of this phenomenon is given and the predictions verified experimentally on radicals in solution. Technical details about the high-pulse power tracking circuit are given.

Open loop fibre optic gyroscope with phase shift nulling signal processing

A simple analogue phase tracking circuit for the fibre gyroscope is described. The system provides a linear output from an open loop gyroscope configuration over a range in Sagnac phase shift >±500° Sagnac, with good linearity and relatively low noise and drift. The use of this demodulator in low-cost medium grade fibre gyroscope applications is projected.

A three-octave-band bandwidth Y circulator (abstract)

So far the limit bandwidth of Y circulators has been an octave. Now a three-octave-band bandwidth Y circulator whose isolated port loss is above 17 dB in the frequency range from 2.5 to 9 GHz can be obtained owing to two arts being adopted. The continuous tracking circuit is used [that is, a series impedance X is connected to the electrical center of junction X=j(ωL−1/ωC), there being ωCL=1/ωCC at circulating angular frequency ωC ], the reactance slope parameter of imaginary part of circulating imput impedance1 being adjusted to zero or nearly so. Values K/μ or P(=M/ω) are kept unchanged by modulating the internal bias field H0 with the frequency of the input signal so as to make the value of unsaturated magnetization intensity M change with the change in frequency ω at same rate.

A reduction method of tracking errors due to multipath waves in direct sequence spread spectrum systems

AbstractThe speed spectrum (SS) communication is a communication system which has excellent characteristics against noise and is suited to the code‐division multiplex. Numerous applications have recently been considered. The delayed lock loop (DLL) is employed frequently as the tracking circuit for SS communication, where, however, a phase tracking error is produced by multipath waves. This phase error degrades the large processing gain, which is one of the most remarkable features of SS communication. We have attempted to reduce the phase error. Here, it is assumed that the peak of the correlation function of the received wave is fixed as long as the object wave has an amplitude much larger than those of multipath waves. Under such an assumption, a circuit is proposed which aligns DLL to the peak of the correlation function. As a result of the operation experiment for the circuit, it is shown that the phase error due to the multipath wave can be reduced to approximately one‐fifth.

Field effect transistor tracking surface field sensor

A closed-loop tracking circuit incorporating high-impedance metal–oxide–semiconductor (MOSFET) transistors has been developed for measuring high-voltage electrostatic fields on the surfaces of conducting electrodes. One MOSFET is used as a field sensor, and the other as a tracking ‘‘dummy.’’ The feedback circuit yields a signal voltage output that is at the same time linearly dependent on the external surface field being measured, and virtually independent of the gain and the offset parameters of the specific MOSFET device used as a sensor.

Analysis and retracking of continental ice sheet radar altimeter waveforms

The SEASAT‐I radar altimeter data set acquired over both the Antarctic and Greenland continental ice sheets is analyzed to obtain corrected ranges to the ice surface. The radar altimeter functional response over the continental ice sheets is considerably more complex than over the oceans. Causal factors identified in this complicated response include sloping surfaces, undulating ice surfaces with characteristic wavelengths on the same spatial scale as the altimeter beam‐limited footprint, off‐track reflections, and dynamic lag of the altimeter tracking circuit. Retracking methods using the altimeter return pulse waveforms give range corrections that are typically several meters. The entire set of SEASAT‐I altimetry over the continental ice sheets is being retracked by fitting a multi‐parameter function to each waveform. Many waveforms have double ramps indicating near‐normal reflections from two distinct portions of the ice surface within the altimeter beam. Two independent range measurements differing by less than 25 m are obtained from retracking the double‐ramp waveforms.

The Application of Radio Interferometry to Extraterrestrial Metrology

Following an introductory discussion of the interferometric method, the essential building block of an interferometric system, the interferometric link, is discussed, especially with reference to the transmit-receive problem and to the noise problem in a frequency tracking circuit. One form of phase-locked loop is discussed in connection with the latter. Several possible interferometric applications are listed and a table is presented in which an attempt has been made at estimating the essential parameters of each system.