# US 4,396,916 A · Pseudonoise radar > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,396,916 A - Document ID: US4396916A - Status: Granted - Kind: A - Application number: 05/132,420 - Filed: 1971-04-08 - Granted: 1983-08-02 - Earliest claimed: 1971-04-08 - Assignees: International Telephone and Telegraph Corporation - Inventors: Tom Schnerk - Web page: https://patentgrep.com/patent/US4396916A ## CPC - G01S 13/325: {using transmission of coded signals, e.g. P.S.K. signals} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A continuous wave pseudonoise radar system which employs a large word rate to avoid spillover and other noise. Spillover is the electromagnetic energy that is transmitted from the transmitting antenna directly to the receiving antenna. In other words, the spillover is not reflected from the target. The word frequency is thus made higher than the highest expected doppler. The high word rate would normally cause an ambiguous range indication because the word wavelength would be less than twice the maximum expected target range. However, this problem is solved by the use of coarse and fine range indicators. It is an outstanding feature of this invention that the coarse range is obtained by changing the transmitter bit rate. The difference between transmitter and receiver bit frequencies is then integrated over a selected period. The definite integral is directly proportional to range. However, the range turns out to be a function of the transmitter bit frequency only at the integral limits. Rapid loosely controlled frequency shifts can thus be made to detect accurately the range of supersonic targets. ## Claims ### Claim 1 In a pseudonoise radar system, the combination comprising: a transmitter voltage controlled oscillator (VCO); a receiver VCO, a carrier oscillator; a transmitting antenna; a receiving antenna; a first mixer connected to said transmitting antenna from said carrier oscillator; a transmitter coder connected from said transmitter VCO to said first mixer; first means including a servo loop having a second mixer having first and second inputs and an output, said receiving antenna being connected to the first input of said second mixer, said loop including second means connected from said receiver VCO to impress a code on said second input of said second mixer of a mean bit frequency directly proportional to the frequency of the output signal of said receiver VCO, said loop including third means connected from said second mixer output to the input of said receiver VCO to maintain the mean bit code appearing at the second input of said second mixer in phase with that on the signal received by said receiving antenna; a third mixer having first and second inputs connected, respectively, from the outputs of said transmitter and receiver voltage controlled oscillators; fourth means to sweep the frequency of said transmitter VCO between first and second different limits; and fifth means to count the number of cycles appearing at the output of said third mixer. ### Claim 2 (depends on 1) The invention as defined in claim 1, wherein said fourth means maintains the frequency of said transmitter VCO constant for a period, t.sub.p, before and after the change therein is made, wherein t.sub.p =(2R.sub.m)/c R.sub.m is the maximum range desired, and c is the velocity of light, said constant frequencies having magnitudes different from each other. ### Claim 3 (depends on 2) The invention as defined in claim 2, wherein sixth means are provided which are actuable to reset said fifth means to zero before the frequency of said transmitter VCO is changed. ### Claim 4 (depends on 1) The invention as defined in claim 1, wherein sixth means are provided which are actuable to reset said fifth means to zero before the frequency of said transmitter VCO is changed. ### Claim 5 (depends on 1) The invention as defined in claim 1, wherein said third means includes a single pole, double throw switch having first and second contacts, sixth means connected from said pole to said receiver VCO, seventh means connected from said second mixer to said first contact, a fourth mixer connected from said third mixer output to said second contact, and a search oscillator connected to said fourth mixer. ### Claim 6 (depends on 1) The invention as defined in claim 1, wherein said fifth means includes a squarer and a digital pulse counter connected in that order from the output of said third mixer. ### Claim 7 (depends on 6) The invention as defined in claim 6, wherein said fifth means includes means actuable to reset said counter before the frequency of said transmitter VCO is changed, and sixth means to indicate visually the number of pulses counted by said counter. ### Claim 8 (depends on 1) The invention as defined in claim 1, wherein said second means includes a receiver coder, each of said coders having the same number of n flip-flops, first and second AND gates for said transmitter and receiver coders, respectively, said first AND gate having inputs from all of the "1" outputs of all of the flip-flops in said transmitter coder, said coders both being connected to produce the same maximal code, said second AND gate having inputs from all of the "1" outputs of all of the flip-flops in said receiver coder, and sixth means connected from both of said AND gates for producing a signal directly proportional to the phase difference between the pulses appearing at the outputs of said AND gates. ### Claim 9 A frequency sweep circuit, said circuit comprising: a double pole, double throw switch having first and second poles, and first and second contacts for each pole; a voltage controlled oscillator (VCO) having an input and an output, first means connected between said first pole and said VCO input; means to supply a first potential to said first pole first contact; means to supply a second potential to said first pole second contact, said first potential being lower than said second potential; first and second crystal oscillators having lower and higher frequencies, respectively, said first and second crystal oscillators being connected to said first and second contacts, respectively, of said second pole, said switch being constructed to cause said poles to engage both of said first contacts at the same time, and to cause said poles to engage both of said second contacts at the same time; a phase detector having a first input connected from said second pole, and a second input connected from said VCO output; said phase detector having an output; and means connecting the output of said phase detector to the input of said VCO.