US 4,059,806 A · Pulse position demodulator circuit

Abstract

A pulse position demodulator circuit is provided which finds particular use in instrument landing systems, but which has general utility. The system responds to a pulse signal in which successive pulse pairs are position modulated in accordance with an incremental modulating signal, and it provides digital outputs which are precise measurements of the time spacing between the pulses of each individual pair, the digital outputs constituting a representation of the modulating incremental signal. The system includes a network for generating a multiplicity of clock signals having different phase relationships. A particular clock is selected by the lead pulse of each received pulse pair to enable a correct digital output to be produced by the system even though the second pulse of the pair may be received earlier or later than a particular reference time. This reduces the resolution requirements of the system without affecting its accuracy, thereby permitting a low speed shift register to be used of the order of one-fourth the length of the shift register which would be required in an equivalent prior art system.

Claims8

Dependent claims

A pulse position demodulator circuit for providing digital outputs representative of the time spacing between received incrementally modulated pulse pairs, said circuit comprising:

a clock oscillator for generating a clock signal of relatively high frequency;
quantizing circuit means coupled to the clock oscillator for producing quantized pulses synchronized with said clock signal in response to the received modulated pulse pairs;
shift register means;
means coupling said quantizing circuit means to said shift register means for propagating the quantized pulses down the shift register means;
first circuit means coupled to the clock oscillator for producing a plurality of clock signals and having predetermined mutual phase relationships with one another;
further circuit means coupling the quantizing circuit means to said first circuit means to select one of said plurality of clock signals for application to said shift register as determined by the timing of the first quantizing pulses of each of the received pairs with respect to a selected reference;
and
output circuit means obtaining inputs from said shift register means providing said digital outputs.

5 more elements

Dependencies are inferred from the claim text.

Pulse position demodulator circuit

Life of this patent

Pulse position demodulator circuit

Life of this patent

Abstract

Claims8