Multichannel frequency-select system

Claim 2

A multichannel frequency-select system wherein the frequency of a crystal in a crystal bank on a missile controls a voltage on a voltage-sensitive capacitor, such as a varactor, and is to be selected to correspond with the frequency of a crystal in a crystal bank on a channel selector on a missile launcher, the frequency-select system being capable of operating at any of a plurality of crystal-controlled frequencies in the missile, and in any one of three different modes: 1. a preset Mode 1, in which the intermediate frequency (IF) in both the missile launcher channel selector and the missile is a rest frequency, with a corresponding constant voltage on the varactor; 2. a select Mode 2, in which the frequency spectrum covered by the crystal bank in the missile and the single crystal in the launcher channel selector is swept or scanned at a ripid rate, with a corresponding voltage on the varactor rising at a greater rate; and 3. an acquire Mode 3, wherein the scanning rate slows down and stops when frequency lock is acquired, with a corresponding voltage on the varactor rising at a lesser rate, the three kinds of varactor voltages, the constant and the 2-speed ramp voltage, appearing first in circuitry on the missile; the multichannel frequency-select system comprising: a launcher channel selector on the missile launcher including: a crystal channel selector, which includes: a plurality of crystals, or crystal bank, arranged in order of increasing resonant frequency; and a multiposition switch, for choosing that one of the plurality of crystals at which the missile is to operate; a mode logic circuit operatively connected to the crystal channel selector and including a preset-select switch which determines the mode of operation and furnishes proper mode direct-current voltages to the missile at a precise time; a mode control circuit, located on the missile, having as an input the three DC mode voltages from the mode logic circuit in the missile launcher channel selector, which mode voltages trigger the one constant and two sweep voltages in the mode control circuit, which subsequently appear on the varactor; a crystal-reference (X-R) loop on the missile including: a basic frequency generator, whose frequency is controlled by the voltage-sensitive capacitor in its tank circuit; a crystal reference bank, having the same plurality of crystals as the crystal channel selector in the missile launcher, one of whose inputs is an output from the mode control circuit, and the other of whose inputs is an output from the basic frequency generator, which sweeps the frequency spectrum of the crystals in thE crystal reference bank until the frequency of the selected crystal is reached, at which time the frequency sweeping in the crystal reference bank stops at the predetermined crystal, whereupon the frequency sweeping in the launcher stops; an AC to DC converter, operatively connected to the crystal reference bank, for converting the radiofrequency from the crystal bank into a direct current which supplies the lock and error signals for the X-R loop; an automatic frequency control (AFC) circuit having an input from the mode control circuit and from the AC to DC converter, which provides the DC voltage in Mode 1 and the 2-speed ramp voltage for Mode 2 and Mode 3 to the voltage-sensitive capacitor in the tank circuit of the basic frequency generator, for increasing the frequency of the basic frequency generator until operation at the selected frequency is achieved.

Claim 3

A multichannel frequency-select system according to claim 1, wherein: the basic frequency generator comprises: a basic LC oscillator whose frequency is controlled by the voltage-sensitive capacitor; and a buffer amplifier for amplifying the output of the basic oscillator.

Claim 4

a select Mode 2, in which the frequency spectrum covered by the crystal bank in the missile and the single crystal in the launcher channel selector is swept or scanned at a ripid rate, with a corresponding voltage on the varactor rising at a greater rate; and

Claim 5

a select Mode 2, in which the frequency spectrum covered by the crystal bank in the missile and the single crystal in the launcher channel selector is swept or scanned at a ripid rate, with a corresponding voltage on the varactor rising at a greater rate; and

Claim 6

A multichannel frequency-selected system according to claim 2, wherein: the X-R loop on the missile further comprises: a transfer oscillator, operating at a fixed frequency; a transfer oscillator, operating at a fixed frequency; an X-R mixing circuit having as its two inputs outputs from the buffer amplifier and the transfer oscillator, to produce a missile low intermediate frequency which varies directly as the voltage on the varactor; a missile channel-select low intermediate frequency amplifier, for amplifying the IF; the launcher channel selector on the missile launcher further comprises: a launcher low IF amplifier and automatic gain control, operatively connected to the missile channel-select low IF amplifier and having an output to the crystal channel selector, for amplifying the IF frequency.

Claim 7

an acquire Mode 3, wherein the scanning rate slows down and stops when frequency lock is acquired, with a corresponding voltage on the varactor rising at a lesser rate, the three kinds of varactor voltages, the constant and the 2-speed ramp voltage, appearing first in circuitry on the missile; the multichannel frequency-select system comprising: a launcher channel selector on the missile launcher including: a crystal channel selector, which includes: a plurality of crystals, or crystal bank, arranged in order of increasing resonant frequency; and a multiposition switch, for choosing that one of the plurality of crystals at which the missile is to operate; a mode logic circuit operatively connected to the crystal channel selector and including a preset-select switch which determines the mode of operation and furnishes proper mode direct-current voltages to the missile at a precise time; a mode control circuit, located on the missile, having as an input the three DC mode voltages from the mode logic circuit in the missile launcher channel selector, which mode voltages trigger the one constant and two sweep voltages in the mode control circuit, which subsequently appear on the varactor; a crystal-reference (X-R) loop on the missile including: a basic frequency generator, whose frequency is controlled by the voltage-sensitive capacitor in its tank circuit; a crystal reference bank, having the same plurality of crystals as the crystal channel selector in the missile launcher, one of whose inputs is an output from the mode control circuit, and the other of whose inputs is an output from the basic frequency generator, which sweeps the frequency spectrum of the crystals in thE crystal reference bank until the frequency of the selected crystal is reached, at which time the frequency sweeping in the crystal reference bank stops at the predetermined crystal, whereupon the frequency sweeping in the launcher stops; an AC to DC converter, operatively connected to the crystal reference bank, for converting the radiofrequency from the crystal bank into a direct current which supplies the lock and error signals for the X-R loop; an automatic frequency control (AFC) circuit having an input from the mode control circuit and from the AC to DC converter, which provides the DC voltage in Mode 1 and the 2-speed ramp voltage for Mode 2 and Mode 3 to the voltage-sensitive capacitor in the tank circuit of the basic frequency generator, for increasing the frequency of the basic frequency generator until operation at the selected frequency is achieved.

Claim 8

an acquire Mode 3, wherein the scanning rate slows down and stops when frequency lock is acquired, with a corresponding voltage on the varactor rising at a lesser rate, the three kinds of varactor voltages, the constant and the 2-speed ramp voltage, appearing first in circuitry on the missile; the multichannel frequency-select system comprising: a launcher channel selector on the missile launcher including: a crystal channel selector, which includes: a plurality of crystals, or crystal bank, arranged in order of increasing resonant frequency; and a multiposition switch, for choosing that one of the plurality of crystals at which the missile is to operate; a mode logic circuit operatively connected to the crystal channel selector and including a preset-select switch which determines the mode of operation and furnishes proper mode direct-current voltages to the missile at a precise time; a mode control circuit, located on the missile, having as an input the three DC mode voltages from the mode logic circuit in the missile launcher channel selector, which mode voltages trigger the one constant and two sweep voltages in the mode control circuit, which subsequently appear on the varactor; a crystal-reference (X-R) loop on the missile including: a basic frequency generator, whose frequency is controlled by the voltage-sensitive capacitor in its tank circuit; a crystal reference bank, having the same plurality of crystals as the crystal channel selector in the missile launcher, one of whose inputs is an output from the mode control circuit, and the other of whose inputs is an output from the basic frequency generator, which sweeps the frequency spectrum of the crystals in thE crystal reference bank until the frequency of the selected crystal is reached, at which time the frequency sweeping in the crystal reference bank stops at the predetermined crystal, whereupon the frequency sweeping in the launcher stops; an AC to DC converter, operatively connected to the crystal reference bank, for converting the radiofrequency from the crystal bank into a direct current which supplies the lock and error signals for the X-R loop; an automatic frequency control (AFC) circuit having an input from the mode control circuit and from the AC to DC converter, which provides the DC voltage in Mode 1 and the 2-speed ramp voltage for Mode 2 and Mode 3 to the voltage-sensitive capacitor in the tank circuit of the basic frequency generator, for increasing the frequency of the basic frequency generator until operation at the selected frequency is achieved.

Claim 9

A multichannel frequency-select system according to claim 3, further including: a missile receiver loop which preempts control of the multichannel frequency-select system when there is a signal at its input, the missile receiver loop including the following components from the missile crystal-reference (X-R) loop: the varactor; the AFC circuit; the basic oscillator; the buffer amplifier; and wherein the basic frequency generator includes: a frequency multiplier, whose input is the output of the buffer amplifier, for multiplying the frequency of the basic oscillator; a radar state at the input to the missile receiver loop for intercepting and detecting a signal reflected off a target; the missile receiver loop further comprising: a missile receiver mixing state for mixing the output of the frequency multiplier with the output of the radar stage; a missile receiver IF amplifier for amplifying the output of the missile receiver mixing state; a frequency discriminator, for providing lock and error signals to the AFC circuit in the missile receiver loop; the relationship of the frequency discriminator output to the other inputs to the AFC circuit being such that when a target signal is present in the missile receiver, which corresponds to an active missile receiver loop, the frequency discriminator preempts control of the basic oscillator, while if the radar signal is interrupted or lost, the circuits associated with the X-R AFC circuit, the X-R loop, resume control until the missile receiver loop is active again.

Claim 10

Refer to FIG. 5B. The preset switch 15 is still open. Transistor Q-C (2N2907A) cuts off, the +19.0 V DC voltage at resistor R2 drops out. Transistor Q-B (2N2222A) conducts, the -19.0 V DC cuts in. Transistor Q-A (2N894), which is a switching transistor, remains cut off. Mode signal voltage on mode signal line 18 is now -19.0 V DC as a result of transistor Q-B conducting. Meanwhile the basic oscillator 24 in the missile starts up from its rest frequency of approXimately 4.0 MHz. (see FIG. 3) and sweeps upward in frequency. When the RF frequency reaches the band-pass or crystal frequency, it fires the transistor Q-A (2N894), a silicon-controlled rectifier, which immediately decreases the magnitude of the mode voltage from -12 V DC to zero, at the end of Mode 2, in 0.5 msec. or less. See FIG. 2C. As may be seen in FIG. 8, the crystal Y-N provides the path between the low IF amplifier 16 and the Q-A SCR. The SCR fires on RF signal, its action being not unlike that of a thyratron. In the laboratory embodiment, and referring back to FIG. 5B, if the operator wishes to select a different channel before missile launch, the preset-select switch 15 is returned from the select position 15B to the preset position 15A, the desired channel is switched in, then the switch 15 is returned from the preset position 15A to the select position 15B. There is no limit on the number of times this can be done except for considerations of battery life of the missile. While the battery life is approximately 12 min. in the embodiment actually built, only 0.5 min. of this represents the drain on the missile launcher. Mode 2: Missile The following is what transpires in the missile in Mode 2. As stated above, within 1 msec. after the preset-select switch 15 is flipped to the select position 15B (see FIG. 5B), the mode voltage changes from +12.0 to -120 V (see FIG. 2C). Within this same time of 1 msec., the -12 V mode voltage is distributed as follows, referring first to FIG. 6A. a. through the two resistors R11 and R20 forming a voltage divider. This negative voltage of 12 V puts a reverse bias on diode CR3, thus disabling the crystal reference bank 34. Diode CR10 is also cut off. Refer now to FIG. 6B. Transistors Q5 and Q2 are cut off, also, thus allowing the sweep to start. When the selected channel is approached in frequency, the crystal in the channel selector 12 being resonant at a frequency approximately 35 HKz. lower in frequency than the corresponding crystal in the crystal reference bank 34 (the basic oscillator 24 heterodyned scanning signal scans from lower to higher frequencies), the channel selector 10 removes the disable voltage and makes the next crystal in the missile crystal reference bank 34 the desired one. This represents a change from Mode 2 to Mode 3. b. Continuing again with Mode 2, and now referring back to FIG. 6A, the -12 V mode voltage is distributed through resistor R2, diodes CR 6 and CR 9, and, referring now to FIG. 6B, into the base of the p-n-p transistor Q7, which saturates its collector and disables the missile receiver IF and RF loop frequency discriminator 66. CR 1 is a 3.3 V Zener diode which holds the low potential end of condenser C10 to a value of +2.7 volts, thus allowing it to charge up with the sweep. Conduction of transistor Q7 shorts out the missile receiver discriminator 66 and prevents a false lock on spurious signals, as may be seen from FIGS. 6A and 6B where they join. The active and equivalent circuit for Mode 2 operation is shown in FIG. 9. Referring back to FIG. 6B, transistor Q6 is switched on and transistor Q4 is switched on. When transistor Q6 is switched on, resistor R14, approximately 820 Omega , and resistor R13 are effectively connected in parallel (see FIG. 9B). This parallel combination of resistors changes the sweep rate to approximately 60 msec. for a complete channel sweep. This sweep is unidirectional, upward in voltage and frequency. See FIG. 3. When the sweep has arrived at the proper frequency in the launcher channel selector 10, the mode voltage goes from -12 V DC to zero at the end of Mode 2, as may be seen fom FIG. 2C. Capacitor C10 in FIG. 6B provides a long time constant downward in ramp voltage, which is the varactor 25 voltage. The long time constant is made possible by current transformation in a transistor, base to emitter. Increasing DC betas result in longer time constants. c. Finally, and still referring to FIG. 6B, the -12-volt mode voltage is distributed through diode CR 8, which is a 24 V Zener diode, through resistor R16 and into the base of transistor Q6 which is a p-n-p switching transistor. It is this switch Q6 that changes the sweep from a 100-millisecond rate to one of several seconds. These are the rates and times involved in the sweep rising from 0 volts to 15 volts. The fast sweep is related to Mode 2, and the slow sweep to Mode 3 as may be seen from FIG. 3. Now with increasing time, within 1 msec. after the preset-select switch 15 has been set to the select position 15B (see FIG. 5B), as the frequency of the basic oscillator 24 rises and its related lower IF frequency is scanning upward in the launcher channel selector 10, it arrives at a crystal or other band-pass element with the desired channel frequency. The signal is passed through (a window) which in turn triggers the -12-volt mode voltage off to zero voltage in 0.5 millisecond or less. Mode 2 requires 18 to 100 milliseconds to complete depending on the specific channel; 18 milliseconds for channel 1 and b100 milliseconds for channel 19 in the embodiment actually built. Mode 3: Missile Launcher and Missile The switch from Mode 2 to Mode 3 is initiated electronically by the launcher channel selector 10 by a sweep scan frequency corresponding to a single crystal or band-pass frequency in the crystal selector unit 12. The preset-select switch 15 remains in its select or open position 15B. The Mode 3, zero mode, voltage is consummated 0.5 sec. after Mode 2 is completed. Disable voltages are removed from the crystal reference bank 34 and the missile receiver frequency discriminator 66, causing the crystal reference bank 34 and the missile discriminator 66 to become active (see FIG. 1). Transistor Q6 (FIG. 6B) is inactive, or cut off, and the slow sweep rate prevails (see Mode 3, in FIG. 3), and drifts upward into the capture region R (see FIG. 2A) of the missile receiver''s discriminator 66. If a reference signal, that is, a radar signal, is available in the receiver loop 60, it will lock onto this loop. Transistors Q6 and Q4 are cut off and as may be seen in FIG. 3, the long time constant sweep results. See A, B, C, of FIG. 2 for the position where this takes place. As presented in FIG. 2, the sweep continues on toward crystal 6 in the missile. If a signal is present in the region of R in the receiver frequency discriminator 66, capture will be made and the sweep stopped. R is the channel width allowing + or - 2 MHz. radar error limits at the X band. The + or - 2. MHz. is divided in R region; the R bandwidth is 4 MHz. If no signal is present in the discriminator 66, the frequency sweep will continue upward up to the resonant frequency of crystal No. 6, and the sweep will stop there, indicating that the crystal reference (X-R) loop 20 is now in control. Effectively, the sweep frequency locks onto the X-R loop. The X-R loop 20 forms a barricade or guard band in the desired channel (see FIG. 2C). When the missile receiver is active, it will preempt control of the basic oscillator 24 as the guard band provides a standby position for capture by the missile receiver loop 60. When a receiver signal develops within the region of R, it will pull the basic oscillator 24 lower in frequency to band center of the receiver frequency discriminator 66. The position at 6 is the stand by frequency which sets up the guard band limits. Position 6 is just an example, it Can be any one of

Claim 11

Refer to FIG. 5B. The preset switch 15 is still open. Transistor Q-C (2N2907A) cuts off, the +19.0 V DC voltage at resistor R2 drops out. Transistor Q-B (2N2222A) conducts, the -19.0 V DC cuts in. Transistor Q-A (2N894), which is a switching transistor, remains cut off. Mode signal voltage on mode signal line 18 is now -19.0 V DC as a result of transistor Q-B conducting. Meanwhile the basic oscillator 24 in the missile starts up from its rest frequency of approXimately 4.0 MHz. (see FIG. 3) and sweeps upward in frequency. When the RF frequency reaches the band-pass or crystal frequency, it fires the transistor Q-A (2N894), a silicon-controlled rectifier, which immediately decreases the magnitude of the mode voltage from -12 V DC to zero, at the end of Mode 2, in 0.5 msec. or less. See FIG. 2C. As may be seen in FIG. 8, the crystal Y-N provides the path between the low IF amplifier 16 and the Q-A SCR. The SCR fires on RF signal, its action being not unlike that of a thyratron. In the laboratory embodiment, and referring back to FIG. 5B, if the operator wishes to select a different channel before missile launch, the preset-select switch 15 is returned from the select position 15B to the preset position 15A, the desired channel is switched in, then the switch 15 is returned from the preset position 15A to the select position 15B. There is no limit on the number of times this can be done except for considerations of battery life of the missile. While the battery life is approximately 12 min. in the embodiment actually built, only 0.5 min. of this represents the drain on the missile launcher. Mode 2: Missile The following is what transpires in the missile in Mode 2. As stated above, within 1 msec. after the preset-select switch 15 is flipped to the select position 15B (see FIG. 5B), the mode voltage changes from +12.0 to -120 V (see FIG. 2C). Within this same time of 1 msec., the -12 V mode voltage is distributed as follows, referring first to FIG. 6A. a. through the two resistors R11 and R20 forming a voltage divider. This negative voltage of 12 V puts a reverse bias on diode CR3, thus disabling the crystal reference bank 34. Diode CR10 is also cut off. Refer now to FIG. 6B. Transistors Q5 and Q2 are cut off, also, thus allowing the sweep to start. When the selected channel is approached in frequency, the crystal in the channel selector 12 being resonant at a frequency approximately 35 HKz. lower in frequency than the corresponding crystal in the crystal reference bank 34 (the basic oscillator 24 heterodyned scanning signal scans from lower to higher frequencies), the channel selector 10 removes the disable voltage and makes the next crystal in the missile crystal reference bank 34 the desired one. This represents a change from Mode 2 to Mode 3. b. Continuing again with Mode 2, and now referring back to FIG. 6A, the -12 V mode voltage is distributed through resistor R2, diodes CR 6 and CR 9, and, referring now to FIG. 6B, into the base of the p-n-p transistor Q7, which saturates its collector and disables the missile receiver IF and RF loop frequency discriminator 66. CR 1 is a 3.3 V Zener diode which holds the low potential end of condenser C10 to a value of +2.7 volts, thus allowing it to charge up with the sweep. Conduction of transistor Q7 shorts out the missile receiver discriminator 66 and prevents a false lock on spurious signals, as may be seen from FIGS. 6A and 6B where they join. The active and equivalent circuit for Mode 2 operation is shown in FIG. 9. Referring back to FIG. 6B, transistor Q6 is switched on and transistor Q4 is switched on. When transistor Q6 is switched on, resistor R14, approximately 820 Omega , and resistor R13 are effectively connected in parallel (see FIG. 9B). This parallel combination of resistors changes the sweep rate to approximately 60 msec. for a complete channel sweep. This sweep is unidirectional, upward in voltage and frequency. See FIG. 3. When the sweep has arrived at the proper frequency in the launcher channel selector 10, the mode voltage goes from -12 V DC to zero at the end of Mode 2, as may be seen fom FIG. 2C. Capacitor C10 in FIG. 6B provides a long time constant downward in ramp voltage, which is the varactor 25 voltage. The long time constant is made possible by current transformation in a transistor, base to emitter. Increasing DC betas result in longer time constants. c. Finally, and still referring to FIG. 6B, the -12-volt mode voltage is distributed through diode CR 8, which is a 24 V Zener diode, through resistor R16 and into the base of transistor Q6 which is a p-n-p switching transistor. It is this switch Q6 that changes the sweep from a 100-millisecond rate to one of several seconds. These are the rates and times involved in the sweep rising from 0 volts to 15 volts. The fast sweep is related to Mode 2, and the slow sweep to Mode 3 as may be seen from FIG. 3. Now with increasing time, within 1 msec. after the preset-select switch 15 has been set to the select position 15B (see FIG. 5B), as the frequency of the basic oscillator 24 rises and its related lower IF frequency is scanning upward in the launcher channel selector 10, it arrives at a crystal or other band-pass element with the desired channel frequency. The signal is passed through (a window) which in turn triggers the -12-volt mode voltage off to zero voltage in 0.5 millisecond or less. Mode 2 requires 18 to 100 milliseconds to complete depending on the specific channel; 18 milliseconds for channel 1 and b100 milliseconds for channel 19 in the embodiment actually built. Mode 3: Missile Launcher and Missile The switch from Mode 2 to Mode 3 is initiated electronically by the launcher channel selector 10 by a sweep scan frequency corresponding to a single crystal or band-pass frequency in the crystal selector unit 12. The preset-select switch 15 remains in its select or open position 15B. The Mode 3, zero mode, voltage is consummated 0.5 sec. after Mode 2 is completed. Disable voltages are removed from the crystal reference bank 34 and the missile receiver frequency discriminator 66, causing the crystal reference bank 34 and the missile discriminator 66 to become active (see FIG. 1). Transistor Q6 (FIG. 6B) is inactive, or cut off, and the slow sweep rate prevails (see Mode 3, in FIG. 3), and drifts upward into the capture region R (see FIG. 2A) of the missile receiver''s discriminator 66. If a reference signal, that is, a radar signal, is available in the receiver loop 60, it will lock onto this loop. Transistors Q6 and Q4 are cut off and as may be seen in FIG. 3, the long time constant sweep results. See A, B, C, of FIG. 2 for the position where this takes place. As presented in FIG. 2, the sweep continues on toward crystal 6 in the missile. If a signal is present in the region of R in the receiver frequency discriminator 66, capture will be made and the sweep stopped. R is the channel width allowing + or - 2 MHz. radar error limits at the X band. The + or - 2. MHz. is divided in R region; the R bandwidth is 4 MHz. If no signal is present in the discriminator 66, the frequency sweep will continue upward up to the resonant frequency of crystal No. 6, and the sweep will stop there, indicating that the crystal reference (X-R) loop 20 is now in control. Effectively, the sweep frequency locks onto the X-R loop. The X-R loop 20 forms a barricade or guard band in the desired channel (see FIG. 2C). When the missile receiver is active, it will preempt control of the basic oscillator 24 as the guard band provides a standby position for capture by the missile receiver loop 60. When a receiver signal develops within the region of R, it will pull the basic oscillator 24 lower in frequency to band center of the receiver frequency discriminator 66. The position at 6 is the stand by frequency which sets up the guard band limits. Position 6 is just an example, it Can be any one of