A New Pulse Modulator for Accurate DC Amplification with Linear or Nonlinear Devices

A new pulse-modulation technique and modulator circuit has been developed, offering several advantages over conventional methods. The technique and circuit are applicable in a broad range of control system and data transmission problems. Use of this method is appropriately considered in any application where dc or low-frequency information is to be amplified or transduced. In addition to both an intrinsically high degree of accuracy and the numerous potential advantages of sampled-data and digital techniques provided by use of this modulator, the modulator offers a solution to the bandwidth problems encountered in conventional pulse modulation methods. Pulse width modulation and pulse frequency modulation both require unrealizable infinite device bandwidth in order to obtain full control of the pulse train duty ratio between zero and unity. The modulator described in this article requires only a finite device bandwidth to obtain full control. The logical development of the modulator principles, based upon the requirements of limited bandwidth and good accuracy, are presented in this article. The mechanization of the modulator circuit in transistorized form is given, with the most accurate configuration discussed at length. Test results of the circuit are summarized. Application of the modulator is discussed, including both theory related to the application, such as modulator dynamic response characteristics and pulse demodulation, and specific applications in space vehicle autopilots, dc amplifiers and servo systems.