Petri Jarske

On properties and design of nonuniformly spaced linear arrays (antennas)

The properties of nonuniformly spaced linear arrays (and nonrecursive filters with nonequidistant taps) are studied. It is shown that in many cases the element spacings of the optimal solution are integer multiples of a suitably chosen basic spacing. This significantly simplifies the design procedure since the arrays can be designed as thinned uniformly spaced arrays, thus avoiding complicated nonlinear optimizations. A simple thinning procedure is used. Another design procedure based on Nth-band FIR (finite-impulse response) filter concepts is introduced, making possible the use of standard FIR filter design methods for nonuniformly spaced arrays; illustrative examples are included. The results compare favorably to published results for nonuniformly spaced designs that did not exploit the special properties of uniform or discrete nonuniform arrays. >

A simple approach to the design of linear phase FIR digital filters with variable characteristics

Abstract A class of linear phase digital filters is discussed for which the filter coefficients are simple functions of the parameters determining the desired frequency response. In the case of lowpass or highpass filters, the 6 dB cutoff frequency is the parameter considered here. Bandpass and bandstop filters are characterized by the center frequency and the bandwidth measured from the 6 dB cutoff frequencies. Notch filters with a first-order zero at the notch frequency are also discussed. The filters are variable over nearly the whole frequency range from zero to half the sampling frequency. Due to direct control of filter coefficients, the length of the filter does not change when it is made variable.

Signal processor implementation of variable digital filters

The implementation of two recently introduced variable digital filter schemes using a TMS320-series digital signal processor is presented. One is a method for updating the coefficients of an FIR (finite-impulse response) filter in a simple manner such that the cutoff frequencies can be controlled through a single parameter. The other is a method for tuning the cutoff frequency of an IIR (infinite-impulse response) filter with one parameter using a series expansion of the low-pass-low-pass frequency transformation. The measured frequency responses compare well with the theory. >

Vector median filters for complex signal

The authors introduce vector median-type (VM) filters for complex narrowband signals and investigate basic properties of the VM operation. They present and analyze the root structures of the filters. Sinusoidal signals modulated by root signals of standard median filters are shown to be root signals of VM filters. For actual implementation, the authors use vector FIR (finite impulse response)-median hybrid (VFMH) filters. They show that these filters preserve abrupt changes in amplitude and phase. The filters are shown to remove impulsive and Gaussian noise effectively. Examples are given of VM and VFMH performance for complex signals.<<ETX>>

Variable linear phase FIR filters

A class of linear-phase digital filters is discussed for which the filter coefficients are simple functions of the parameters determining the desired frequency response. In the case of lowpass filters, the 6-dB cutoff frequency is the parameter considered. High-pass, bandpass, bandstop, and notch filters can be obtained with simple transformations from a low-pass prototype. The filters are variable over nearly the whole frequency range from zero to half the sampling frequency. Due to direct control of filter coefficients, the length of the filter does not change when it is made variable.<<ETX>>

VCO with double cross-coupled high-speed and low-power multivibrator architecture

New circuits of high-speed multivibrators are developed and consequently used to create new circuit of ICO/VCO. While implemented on 0.8 /spl mu/m BiCMOS (14 GHz NPN) an amplitude of 550 mV at 2 GHz with consumption less than 5.1 mW from 2.2 V power supply can be easily achieved. The control ability of the ICO is about 320 MHz/mA. The low phase noise makes the circuit also suitable for building high-speed PLLs for various applications in communications and microprocessors.

New low-power/high-speed double-cross-coupled ICO/VCO

A new ICO/VCO circuit is proposed, having the ability to work from a lower voltage supply at higher speed than the existing ones. On 0.8 /spl mu/m BiCMOS (14 GHz NPN) an amplitude of 0.4 V at 1 GHz and consumption of only 5.6 mW from 2.2 V power supply is achieved. The control ability is 750 MHz/mA. The circuit has very low phase noise and it is suitable for modern PLLs.

New high-speed double cross-coupled ICO/VCO

A new circuit of ICO/VCO is proposed, having abilities to work from lower voltage supply at higher speed than the existing ones. On 0.8 /spl mu/m BiCMOS (14 GHz NPN) an amplitude of 400 mV at up to 2 GHz and consumption less than 16 mW from 4.5 V power supply is achieved. The control ability is 1250 MHz/mA. The circuit has very low phase noise and it is suitable for modern PLL circuits in communication and microprocessor applications.