Patent GB-1049021-A (GB)
Title: Radio navigation equipment
IPC: G01S1/30
Filed: 1964-01-20
Abstract: 1,049,021. Radio navigation systems. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Jan. 20, 1964 [Jan. 18, 1963], No. 2400/64. Heading H4D. In a radio navigation system wherein a receiver is operable to compare the phases of a locally generated carrier wave with a corresponding carrier wave originating from a transmitter station, and wherein the frequencies of the said carrier waves are capable of being changed in accordance with a predetermined programme, the receiver and transmitter station comprises a frequency synthesis device comprising a continuously operating binary pulse counter fed from a pulse generator and a pulse dividing counter which at its output produces a square pulse voltage having a half period corresponding to a predetermined number of received pulses at the input of the dividing counter, wherein each stage of the binary counter is provided with means producing pulses from those input pulses to the stage which do not cause switching of the said stage; and wherein by application of said produced pulses from programme selected stages to the input of the dividing counter, the frequency of the output of the dividing counter may be changed whilst maintaining a fixed phase relationship. In the receiver the pulses applied to the binary counter are controlled in dependence on the phase of a corresponding carrier wave received from one of the transmitter stations, so that a predetermined phase relationship can be maintained between the said carrier wave and the corresponding signal produced in the frequency synthesis device of the receiver. A receiver and frequency synthesizer is shown in Fig. 1, wherein a high frequency pulse train is generated by oscillator 1 and differentiator 2 and is fed via a gate 3 to a binary pulse counter 4, comprising a cascaded series of bi-stable stages, FF1 &c. As well as controlling the state of the following stage, the output of a stage, e.g. waveform (a), Fig. 2 (not shown), is differentiated to produce a pulse output, waveform (d), corresponding to those pulses in waveform (a) which do not start a corresponding pulse in the output of the next stage, waveform (b). The result is that none of the so-produced pulses coincide in time, and when combined they produce an evenly spaced pulse train at the same frequency as the train fed to the binary counter. The produced pulses for the first stage of the counter are passed directly to the input of a pulse dividing counter 6, whilst the produced pulses from the later stages are fed to the said input of individual switches forming part of a selection unit 5. The output of the last stage of counter 4 is fed to another counter 9 which divides down the repetition frequency of the said output until pulses are produced at the output of counter 9 at a rate of about one per second. These pulses are fed to a further binary counter 11 which controls, according to a prearranged programme, the operation of the switches in the selection unit 5, any one combination of stage states in counter 11 corresponding to one combination of closed switches. The last stage of counter 6 delivers a pulsed voltage having a width and half period corresponding to the passage of a certain number of pulses into the counter 6. Since the rate of arrival of pulses at the input of counter 6 is dependent on the number of switches in selection unit 5 that are closed, the frequency of the output of counter 6 is altered every second in accordance with the programme. The phases of the switch-overs in the stages of counter 6 are controlled by pulses from the differentiated output of the last stage of counter 9. The output of counter 6 is shown applied to one input of a phase detector 13, to the other input of which is applied a pulse signal of the same frequency, received from a distant transmitter. The phase detector produces a positive or negative phase error signal which is applied to gate 3 to cause the addition of further pulses to counter 4 or the inhibition of the normal pulses (Fig. 3, not shown). Alternatively, Fig. 4 (not shown) some pulses from differentiator 2 may be normally inhibited, with the signal from the phase detector 13 causing less or more inhibition. The algebraic sum of added or inhibited pulses is shown on indicator 16, which when there is no more phase error, can represent the distance of the distant transmitter, provided that the indicator has initially been set to the initial known distance between the stations. With two transmitting stations, the position of the receiver may be determined.