Arrangement for generating an angle-modulated carrier signal of a constant amplitude in response to data signals

An apparatus for generating an angle modulated carrier having a constant amplitude and continuous phase .phi.(t) with data signals of a given symbol frequency 1/T comprising:

• (a) a clock circuit synchronized with the symbol frequency which produces a clock signal having a frequency 4q/T, where q is an integer greater than 1;
• (b) a control circuit comprising:
• (i) an addressing circuit controlled by said clock signal, said addressing circuit comprising:
• (A) an interpolation counter responsive to a given number of consecutive data symbols producing addresses at a frequency of 4q/T;
• (B) a counter controlled by a signal having the symbol frequency, responsive to the data symbols for producing phase state numbers representing the phase .phi.(t) in modulo 2.pi. values at the boundaries of the symbol intervals of length T;
• and
• (C) and address converter circuit responsive to said given number of consecutive data symbols for producing addresses and for producing a conversion indication signal for said interpolation counter;
• (ii) a selection signal generator controlled by the clock signal and responsive to the phase state numbers for producing first and second selection signals;
• (c) a signal processor connected to the control circuit counters, said first selection signal enabling at each clock instant said signal processor to generate one of said two values representing the signals cos .phi.(t) and sin .phi.(t), said signal processor including a first read only memory addressable by addresses received from said address converter, said first read only memory being for storing only the values representing cos .phi.(t) and sin .phi.(t) for non-decreasing phases .phi.(t) associated with one predetermined number;
• (d) a digital to analog converter connected to receive said first read only memory addressed contents, said digital to analog converter producing an inverted and non-inverted analog signal in response to said second selection signal, whereby said read only memory signals are converted into samples of a modulated carrier at a carrier frequency of q/T.