Cellular radio communications system

A quadrature modulator circuit for cellular radio communications systems for use in both large and small area cell regions comprising:

• a first filter circuit having an input and an output and responsive to an encoded signal applied to said input thereof for providing a first filtered encoded output signal;
• a second filter circuit having an input and an output and responsive to an encoded signal applied to said input thereof for providing a second filtered encoded output signal,
• a first multiplier circuit having a first input connected to the output of said first filter circuit and responsive to a cos (w.sub.c t) modulating signal for selectively modulating the first filtered encoded output signal from said first filter circuit to selectively provide a cosine component of a binary offset quadrature amplitude first linear modulated signal for use exclusively in small cell areas and a cosine component of a non-linear constant envelope differential encoded GMSK modulated signal for use exclusively in large cell areas,
• a second multiplier circuit connected to the output of said second filter circuit and responsive to a sin(w.sub.c t) modulating signal for selectively modulating the second filtered encoded output signal from said second filter circuit to provide a sine component of said non-linear constant envelope differentially encoded GMSK modulated signal for use exclusively in large cell areas and a sine component of said binary offset first linear modulated signal for use exclusively in small cell areas,
• and an adder circuit connected to said first and second multiplier circuits for adding said cosine and sine component signals from said multiplier circuits for selectively providing an output signal consisting of said linear modulated output signal exclusively for small cell areas and of said non-linear modulated signal exclusively for large cell areas.