Patent GB-820394-A (GB)
Title: Improvements in or relating to high speed digital data processing circuits
IPC: H03K17/74
Filed: 1957-10-25
Abstract: 820,394. Digital electric calculating-apparatus. WESTERN ELECTRIC CO. Inc. Oct. 25, 1957 [Oct. 31, 1956; Dec. 31, 1956 (2)], No. 33396/57. Class 106 (1). In a microwave data processing circuit comprising first and second information channels microwave energy is applied to the channels under control of digital signals obtained from first and second synchronized pulse generating means. As described the circuits comprise serial binary adders employing waveguides. Circuit details and symbols.-Waveguides such as 44, Fig. 1, are coupled by hybrid junctions such as 38 and circulators such as 41, switching control being effected by diodes such as 45 coupled to detection diodes such as 46. In a hybrid junction, microwave energy applied to an input waveguide such as 44 is divided between the two branch waveguides such as 34 ; if the energy reflected back from the two branch waveguides is equal in phase and magnitude, no energy appears in the opposite or output waveguide 47. In a circulator, microwave energy applied to a first waveguide such as 43 is transmitted to a second waveguide 44, signals from this waveguide are transmitted to a third waveguide 35 and so on; the impedance state of a control diode, such as 45, may determine whether energy is transmitted along a waveguide or is reflected back to the circulator to be transmitted along a further waveguide. Constructions of known forms of hybrid junctions and circulators are described. Silicon diodes as described in Specification 715,268, [Group XXXVI], may be employed. The circuits comprise also amplifiers such as 28, e.g. closespaced triodes or travelling-wave tubes, and variable microwave attenuators such as 17. Serial adders.-The adder shown in Fig. 1 comprises two similar half adders 31, 51, the half adder 31 receiving binary numbers A, B in serial form at a digit repetition frequency of 60-100 mc/s., each " 1 " being represented by a pulse of microwave energy, Fig. 2. The microwaves for each number are obtained from a 5-12 kmc./s. klystron oscillator 14 or 15 whose output is gated through hybrid junction 19 or 26 to waveguides 24 or 27 only when a control diode in a branch waveguide receives a pulse from word generation circuit 11 or 12 controlled by synchronizing pulse source 13. In half adder 31, detection diodes associated with input hybrid junctions 36, 37 apply D.C. controls (see line 3, Fig. 2) to diodes 48, 45 in such manner that, if microwave energy is present at input A or B, the latter diodes reflect energy back to circulators 42, 41 respectively, such energy being otherwise transmitted to sum output hybrid junction 38. Thus if a " 1 " pulse is present on one input and not the other, a " 1 " pulse appears on waveguide 34 to represent an intermediate sum, Fig. 2. If a " 1 " occurs on both inputs, the energy transmitted from hybrid junction 36 via waveguide 43 to circulator 41 is transmitted to carry output waveguide 35 (see Fig. 2). The carry outputs from half adders 31, 51 are applied through one-digit delay circuits 55, 58 to hybrid junction 53 and the output on waveguide 54 together with the intermediate sum output on waveguide 34 form the inputs to half adder 51, the final sum output being obtained on waveguide 20. This waveguide may be coupled via a one-word delay circuit to one of the inputs A, B, thus forming an accumulator. In the full adder shown in Fig. 3, the numbers are similarly applied to inputs A and B leading to hybrid junctions 121, 90 and carry input pulses are similarly applied via waveguide 83 to hybrid junction 101. A circuit comprising a pair of circulators, leading from each of these hybrid junctions, has two branches connected by directional couplers to sum waveguide 84 and carry waveguide 85 respectively, detection diodes such as 103, 104 associated with the hybrid junctions controlling diodes such as 93, 135 to determine which, if any, branch is operative. A further circulator 127 is operative under control of diode 139, when a pulse is present at all three inputs, to apply energy via hybrid junction 138 to both the sum and carry waveguides. The carry waveguide 85 is coupled to carry input waveguide 83 via one-digit-delay circuit 146 which, in practice, may be formed by adjusting the lengths of the waveguides themselves. A control diode such as 139 in a waveguide stub (141) absorbs energy when in one impedance state while, in the other state, it transmits energy to be reflected back from the end of the stub. Modifications.-Various alternative diode biasing arrangements for obtaining logical OR and AND circuits are described and shown. The circulator 42, Fig. 1, having only one operative input and output, may be replaced by an isolator; a construction of a known form of isolator is described. According to further modifications, two waveguides, carrying pulses for " 1 " and " 0 " respectively may be employed for each binary signal, or different binary signals may be represented by microwaves of different timing frequency, phase or polarization.