Abstract: A sampled data FIR filter of the type including alternately connected ADDER circuits and delay stages in a serial chain where input samples are multiplied by coefficients and applied in parallel to the ADDER circuits for addition to partial sums therein has respective COUNTER circuits coupled to each ADDER circuit to respond to sum overflows. The COUNTER circuits are serially connected one to another by delay stages. The overflow count corresponding to each signal sample is translated to successive counter in consonance with such partial sum being translated from ADDER circuit to ADDER circuit. The last COUNTER circuit contains the net number of overflows corresponding to the output sum, which overflow signal is indicative of the state of correctness of the output sample.

Abstract: A self-corrected electric filter with localized constant elements having two inputs, two outputs, input and output matching means, a group of an even number of filter elements in cascade for filtering the wide band signal, group delay time correction means comprising adjacent secondary couplings connected between at least two successive filter elements and secondary non-adjacent couplings connected between at least two non-adjacent filter elements.

Abstract: In a bandpass filter having five or more resonator stages, a sub transmission line is coupled to the main transmission line at the first and fourth resonators. The first to fourth resonators provide peak attenuation points at both sides of the center frequency in the attenuation curve, while the remaining resonators following the fourth resonator further sharpen the attenuation characteristics of the bandpass filter. The main and sub transmission lines may be formed by striplines on a printed circuit board, while the sub transmission line can be capacity coupled to the main transmission line. Coupling capacitances are freely set by setting the length of each gap between adjacent striplines to a desired value. Thus, the peak attenuation points can be accurately controlled to provide a bandpass filter having superior characteristics.

Abstract: Filter circuits of the type having inductance and capacitance elements, wherein the number of magnetic components is reduced by using two transformers to perform the functions of four individual inductors. Each transformer has one end of the primary winding connected to one end of the secondary winding, and a pi or T equivalent circuit in which one of the inductance values is equal in magnitude and opposite in sign to a corresponding equivalent circuit inductance value of the other transformer.

Abstract: In modern communication systems, it has become important to provide filters, and in particular bandpass filters, which can provide substantially uniform group delay across the bandwidth of the filter while still achieving good amplitude response. In this regard, it is particularly desirable to substantially reduce the large variations in the phase characteristics found in conventional bandpass filters at the nominal band edge of the filter. To accomplish this, a filter is provided having at least one pair of lattice arms coupled in parallel to one another between the input and output of the filter. Each of the lattice arms includes a plurality of resonant LC resonators, each of the resonators having a different resonant frequency than the center frequency of the filter. In particular, within the bandwidth of the filter, the exponential damping coefficients for the resonators in each arm are set to decay at the same rate. This desired decay can be accomplished by exponential sizing of the components.

Abstract: Input signals having a particular impedance in a particular frequency range are provided. A first transformer has at its input a particular impedance in the particular frequency range and provides a change at its output to a second impedance in the particular frequency range. A filter is constructed to receive the signals from the first transformer and is provided with the second impedance in the particular frequency range. When the second impedance is lower than the particular impedance, the operation of the filter at the second impedance is advantageous because the size of the inductances in the filter is significantly reduced without impairing the quality of the inductances or increasing energy losses in the inductances.A second transformer is constructed to receive the signals from the filter. The second transformer provides the second impedance at its input and provides at its output a change to the particular impedance in the particular frequency range.

Abstract: A method of tuning a trap circuit to a desired frequency is provided. A constant amplitude signal is applied to the trap circuit in a progression of successively different frequency increments. The frequency increments cover a frequency range including the desired frequency. The amplitude of the signal, as modified by the trap circuit is detected and stored at each of the different frequency increments. Successive ones of the stored amplitude values are compared until an amplitude difference is found which is greater than a predetermined minimum difference and is of a polarity indicative of an increase in amplitude with the progression, and is a successor of an amplitude difference which is greater than the predetermined minimum difference and of a polarity indicative of a decrease in amplitude with the progression. The frequency at which the inflection point occurs, as indicated by the two-named amplitude differences, represents the null frequency of the trap circuit.