Abstract: The transmitter (DTR) and the receiver (DRC) of a system for transmitting data signals at a given symbol rate 1/T comprise discrete-time smearing filters (SM and DSM) for combatting the effect of additive pulse-like disturbances (p'(t)) in the transmission channel (TCH). In many cases these disturbances (p'(t)) turn out to have a pronounced bandwidth-limited nature. By utilizing this feature the implementation of the smearing filters (SM and DSM) is simplfied and/or their performance level is improved in that the non-zero values of their impulse responses s(i) and d(j) only occur at the points of grids of the indices i and j recurring with a period of L, where L is an integer greater than 1 and where L is determined substantially by the ratio L.sub.0 of the symbol rate 1/T to twice the highest significant frequency f.sub.m of these disturbances (p'(t)).

Abstract: An arrangement for full-duplex data transmission over a two-wire circuit (1) comprises a transmit channel (2) connected to a baseband data transmitter (6) and including a smearing filter (18), a receive channel (3) connected to a baseband data receiver (9) and including a complementary smearing filter (19), a hybrid junction (4), an echo canceller (14) with an adaptive filter (15) and an adjusting circuit (16), and a combining circuit (17) inserted in the receive channel (3).

Abstract: A frequency-domain block-adaptive digital filter (FDAF) having a finite impulse response of length N for filtering a time-domain input signal in accordance with the overlap-save method includes window means (11) for obtaining modifications (B(p;m)) of the 2N frequency-domain weighting factors (W(p;m)) from correlation products (A(p;m)). A known FDAF of this type contains five 2N-point FFT's, two of which are used in the window means (11). By utilizing a special time-domain window function which can be implemented very efficiently in the window means (11) with the aid of a frequency-domain convolution, a FDAF of this type containing only three 2N-point FFT's is obtained whose convergence properties are comparable to those of the known FDAF containing five 2N-point FFT's.

Abstract: A data transmission system comprising a transversal smearing filter at the transmitting end and a transversal desmearing filter at the receiving end. To simplify the filters, at least the sequence of coefficients of the desmearing filter is formed by elements of the set {-1, 0, +1}, which results in an optimum smearing of noise pulses in the system compared with a system without such a filter.

Abstract: A transmission system for transmitting data signals in a modulation band comprising a transversal smearing filter at the transmitter end and a transversal desmearing filter at the receiver end. In order to obtain an optimum smearing efficiency, the sequence of real individual coefficients of the multiplying factors of the transversal desmearing filter satisfy the requirement that for a given upper limit for the intersymbol interference produced by the cascade arrangement formed by the smearing filter, and the desmearing filter a substantially maximum value is derived for a merit factor indicating by what factor the maximum value of a disturbance is decreased by including a smearing filter and a desmearing filter in the transmission system.

Abstract: Multiplier circuit for multiplying an information signal x(t) by a periodic signal y(t) having frequency f.sub.o, more specifically for amplitude modulation purposes in a stereo decoder. The multiplier circuit comprises N switching circuits 21(k) wherein k=0, 1, . . . N-1 which are each connected to a clock pulse generator 221, 222 by means of a control channel 25(k) and are each connected to an input of an adder device 28 by means of a signal channel 26(k). In addition, each switching circuit 21(k) receives the information signal x(t). A series of clock pulses g(k;t) is applied to each control channel in such a manner that for the control channel having number k these clock pulses occur at the instants t.sub.o +k(T.sub.o /N)+iT.sub.o wherein t.sub.o represents a constant T.sub.o =1/f.sub.o and i=. . . , -2, -1, 0, 1, 2, . . . Each signal channel 26(k) comprises a weighting network 27(k) having a constant weighting factor W(k) defined by the relation W(k)=y(t.sub.o +k(T.sub.o /N)).

Abstract: Method of a N-point discrete Fourier transform. The original set, consisting of N input signal values {a(k)}k=0,1,2, . . . N-1 is converted into two sets of signal values {b.sub.1 (q)}q=1,2, . . . M and {b.sub.2 (q)}q=1,2, . . . M, which each comprise M=(N-1)/2 signal values, each value being a linear combination of two of the original input signal values a(k). These sequences are circularly convolved with the impulse response h.sub.1 (v)=.alpha.cos((2.pi./N) g.sup.V) and h.sub.2 (v)=j.beta.sin ((2.pi./N) g.sup.V), respectively, for generating a set of third data elements y.sub.1 (p) and a set of fourth signal values y.sub.2 (p). Herein N is a prime and .alpha.,.beta. and g represent constants and it holds that p, v=1,2, . . . M, whereas j=.sqroot. -1. The desired output signal value can be obtained by means of a linear combination of the signal values y.sub.1 (p), y.sub.2 (p) and a(0).

Abstract: An FM-receiver with transmitter characterization, having a tuning unit, an IF-amplifier, a demodulation circuit for demodulating a discrete transmitter characterization signal, a clock regeneration circuit, a decoding device for decoding the discrete transmitter characterization signal and a signal processing unit. The clock regeneration circuit regenerates a clock signal the period of which is obtained by dividing the frequency of the stereo pilot signal. Synchronization of the clock signal phase with the phase of the clock signal used in the transmitter is carried out by detecting, using of a periodic window signal, the average phase of the code edges in the discrete transmitter characterization signal and by choosing the phase of the regenerated clock signal to be equal thereto.

Abstract: An analog-to-digital converter is described for converting an analog-signal into a sequence of (b+a)-bit code words by means of a b-bit auxiliary analog-to-digital converter. To reduce the quantizing noise resulting from the requisite quantizing of the analog signal samples this analog signal is applied to an integrating network whose output is connected to an amplitude-limiting device which brings the integrated signal within the signal range of the auxiliary analog-to-digital converter, which in its turn produces a sequence of b-bit code words which are applied to a digital output filter via a cascade arrangement of an amplitude-restoration device and a difference network.Sampling pulses which occur at a frequency exceeding the Nyquist sampling frequency associated with the analog signal are applied to the auxiliary analog-to-digital converter.

Abstract: A digital-to-analog converter is described for converting (b+a)-bit code words into an analog signal by means of a b-bit auxiliary digital-to-analog converter. In order to reduce the quantizing noise introduced by the indispensible quantizing of the (b+a)-bit code words for obtaining the b-bit code words these (a+b)-bit code words are applied to an integrating network which has its output connected to an amplitude-limiting device which brings the integrated signal in the signal range of the auxiliary-D/A converter. The output signal of the amplitude-limiting device is now quantized and this quantizing signal is applied to the auxiliary D/A converter which produces analog output signal samples which are applied to, possibly, an analog output filter through a cascade arrangement of an amplitude-restorer and a difference network.

Abstract: A multiplex system has an inverse Fourier transformer that is unequal to its forward one, therefore an optimum distribution of elements is possible.