Zlatka Nikolova

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In this paper a new adaptive complex digital filter structure is proposed. First, a very low sensitivity second-order complex bandpass (BP) filter section with independent tuning of the central frequency and the bandwidth (BW) is developed (the low sensitivity of the narrow-band realization is ensuring a higher BW-tuning accuracy or better precision in a(More)
– In this paper a very low sensitivity fourth-order complex band-pass filter section with independent tuning of the central frequency and the bandwidth is developed. A narrowband adaptive filter structure is formed around this section, using LMS algorithm to adapt the central frequency. The developed filter structure is providing a low computational(More)
1.1 Introduction Interest in complex signal processing goes back quite some time: in 1960 Helstrom (Helstrom, 1960) and Woodward (Woodward, 1960) used the complex envelope presentation to solve problems with signal detection, as did Bello (Bello, 1963), who used it to describe time-invariant linear channels. A number of publications at that time also(More)
In this article, very low sensitivity variable complex filter (VCF) sections are developed. They have two important advantages: extremely low passband sensitivity and independent tuning of the bandwidth and the central frequency over a wide frequency range. The first advantage provides resistance to quantization effects, while the second one gives a better(More)
In this paper we put forward a scheme for suppressing narrowband interference by the use of adaptive narrowband filtering. We compare this method with other schemes for the suppression of complex narrowband interference in OFDM UWB systems, such as the frequency excision method and complex narrowband interference identification and cancelation algorithms.(More)
—Signal distortions in communication systems occur between the transmitter and the receiver; these distortions normally cause bit errors at the receiver. In addition interference by other signals may add to the deterioration in performance of the communication link. In order to achieve reliable communication, the effects of the communication channel(More)
In this paper we propose a scheme for Narrowband Interference (NBI) suppression for MIMO OFDM system using adaptive narrowband filter banks. We compare this method with other schemes for suppression of complex NBI, such as Frequency Excision method, Complex NBI Identification and Cancellation algorithm and Orthogonal Space Time Block Coding (OSTBC). The(More)
During the interepidemic periods of 34 years (1955-1988) the National Influenza Centre of Bulgaria with the aid of 11 supporting stations investigated a total of 27240 nasopharyngeal washings and 42530 paired sera of patients with acute respiratory diseases. Eighty strains of subtype A (H1N1) influenza virus, 60 strains of subtype a (H2N2), 148 strains of(More)
The aim of the recent survey is to investigate the dynamics of female sex organs malignancies (carcinoma of the uterine corpus, cervical carcinoma and ovarial carcinoma) incidence and to make a structural analysis. The incidence of female sex organs malignancies increases every other year from 37.7 cases in 1986 to 58.64 cases per 100,000 women in 1996. The(More)