Abstract: A smear-desmear filter having the frequency depending group delay characteristics is implemented by a transversal filter having a plurality of delay elements each having the delay time 1/(2f.sub.2), where f.sub.2 is the highest frequency component of an input signal, tap weight coefficient means for providing the product of the output of the tap and the predetermined coefficient which is supplied from a digital memory, and an adder for summing up all the outputs of the tap weight coefficient means. A tap and/or a tap weight coefficient means is provided for every m number of delay elements, where m is an integer larger than 2, thus, the number of tap weight coefficient means is merely 1/m of the number of the delay elements. The tap weight stored in said the digital memory is determined by the position (n) of a tap, a delay time (.tau.) of each delay element, the required delay expansion width (a), and the value of said integer (m). The obtained delay characteristics is sinusoidal in the given frequency band.

Abstract: An automatic amplitude and phase equalization system in an FM communication circuit, in which a pilot signal included in a baseband signal of a transmitted FM signal demodulated by an FM demodulator is extracted and frequency-multiplied, a high harmonic wave of the pilot signal generated in the baseband signal is phase-detected using the frequency-multiplied output as a reference signal, an amplitude equalizer provided before the FM demodulator is driven by a component included in the phase detected output and of the same phase as the reference signal, and a phase equalizer provided before the FM demodulator is driven by a component included in the phase detected output and orthogonal to the reference signal, whereby amplitude and phase characteristics of a transmission path of the FM signal are automatically equalized.

Abstract: In a sampling function type equalizer having a transversal filter with a plurality of potentiometers, the tap weights of the transversal filter are adjusted according to the desired values of the amplitude-frequency characteristics A.sub.p (n), and the delay-frequency characteristics .tau..sub.p (n). The first multiplication of A.sub.p (n) and the predetermined discrete function in addition to the second multiplication of said .tau..sub.p (n) and said predetermined discrete function, are performed. Also, the Bessel function is provided according to the product of the second multiplication. The first convolution integration is performed for the product of the first multiplication, the second convolution integration is performed for the output of the Bessel function, and the third convolution integration is performed between the results of said first and the second convolution integrations. The result of the third convolution integration provides the tap weights of the potentiometers of the transversal filter.

Abstract: A Bessel function type automatic delay equalizer comprising a plurality of transversal filters each of which has an independent delay cosine equalization component having a predetermined period, and the superposition of those filters providing the desired characteristics, characterized in that, said equalizer further comprises a Bessel function generator for controlling the tap gain of said transversal filters.