CA1160696A - Baseband sprectrum generator using logic level input pulses - Google Patents
Baseband sprectrum generator using logic level input pulsesInfo
- Publication number
- CA1160696A CA1160696A CA000355464A CA355464A CA1160696A CA 1160696 A CA1160696 A CA 1160696A CA 000355464 A CA000355464 A CA 000355464A CA 355464 A CA355464 A CA 355464A CA 1160696 A CA1160696 A CA 1160696A
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- Prior art keywords
- pulse
- pulses
- logic level
- source
- primary winding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
D-22,344 BASEBAND SPECTRUM GENERATOR USING LOGIC
LEVEL INPUT PULSES
by Lawrence E. Getgen ABSTRACT OF THE DISCLOSURE
A pulse source provides logic level pulses, having a pulse rate of fb and a pulse width of t', to the input of a switching amplifier having an open collector output. A
relatively high voltage, greater than the logic level voltage amplitude, is applied to the collector via a current limiting resistor R and the primary winding of a transformer. The logic level pulses switch the switching amplifier on at intervals of T = l/fb for a duration of t' seconds. The switching current in the primary winding of the transformer induces a current in the secondary winding thereof which has a spectrum that includes a spectral element at the switching rate fb and multiples thereof. This output spectrum and power level depend upon the pulse amplitude and the pulse width t'. The output power is proportional to the amplitude of the switched pulse and the pulse width t', whereas, the spectral bandwidth is inversely proportional to t'.
LEVEL INPUT PULSES
by Lawrence E. Getgen ABSTRACT OF THE DISCLOSURE
A pulse source provides logic level pulses, having a pulse rate of fb and a pulse width of t', to the input of a switching amplifier having an open collector output. A
relatively high voltage, greater than the logic level voltage amplitude, is applied to the collector via a current limiting resistor R and the primary winding of a transformer. The logic level pulses switch the switching amplifier on at intervals of T = l/fb for a duration of t' seconds. The switching current in the primary winding of the transformer induces a current in the secondary winding thereof which has a spectrum that includes a spectral element at the switching rate fb and multiples thereof. This output spectrum and power level depend upon the pulse amplitude and the pulse width t'. The output power is proportional to the amplitude of the switched pulse and the pulse width t', whereas, the spectral bandwidth is inversely proportional to t'.
Description
~ l~OSg6 D-2~,344 1 BASE~ND SPECTRU~ GENERATOR USING LOGIC
2 LEVEL INPUT PULSES
6 This invention relates generally to a carrier frequency 7 supply for multiplex communication systems, and more particularly, 8 to an improved method for génerating a plurality of harmonically 9 related carrier frequencies.
In many multiplex communication systems, a number of 11 closely spaced carrier frequencies are required t~ provide the 12 basic separation between carrier channels. For example, in 13 frequency division multiplex systems which employ single sideband 14 modulation techniques, carrier frequencies often are spaced at 4 kHz intervals. Further, such carrier frequencies are required 16 in the low frequency end of a spectrum, e.g., in the range 12 -17 60 kHz. In other words, the frequencies are used in the initial 18 modulation step which locates the individual channels in the 19 baseband range. Such frequencies have in the past been generated from a master oscillator, the output of which is divided down to 21 provide relatively low frequency pulses having a high harmonic 22 content. These pulses are, in turn, applied to individual 23 filters and harmonic amplifiers, one for each of the desired 24 carrier frequencies. One problem with such systems is that the 25 pulses applied to the filters and amplifiers have a relatively 26 strong fundamental component which tends to overload the 27 amplifier and filter network, thus, requiring high power 28 amplifiers and sophisticated filters. Further, in comparison ~160~g~ D-22,344 1 with the present invention such systems require an excessive 2 number of circuit elements in order to accomplish the desired
6 This invention relates generally to a carrier frequency 7 supply for multiplex communication systems, and more particularly, 8 to an improved method for génerating a plurality of harmonically 9 related carrier frequencies.
In many multiplex communication systems, a number of 11 closely spaced carrier frequencies are required t~ provide the 12 basic separation between carrier channels. For example, in 13 frequency division multiplex systems which employ single sideband 14 modulation techniques, carrier frequencies often are spaced at 4 kHz intervals. Further, such carrier frequencies are required 16 in the low frequency end of a spectrum, e.g., in the range 12 -17 60 kHz. In other words, the frequencies are used in the initial 18 modulation step which locates the individual channels in the 19 baseband range. Such frequencies have in the past been generated from a master oscillator, the output of which is divided down to 21 provide relatively low frequency pulses having a high harmonic 22 content. These pulses are, in turn, applied to individual 23 filters and harmonic amplifiers, one for each of the desired 24 carrier frequencies. One problem with such systems is that the 25 pulses applied to the filters and amplifiers have a relatively 26 strong fundamental component which tends to overload the 27 amplifier and filter network, thus, requiring high power 28 amplifiers and sophisticated filters. Further, in comparison ~160~g~ D-22,344 1 with the present invention such systems require an excessive 2 number of circuit elements in order to accomplish the desired
3 result.
SU~ARY OF THE INVENTION
7 A baseband spectrum generator includes a source of 8 logic level pulses, having a pulse rate of fb and a pulse width 9 of t', which logic level pulses turn on a switching amplifier at intervals of T = l/fb for a duration of t' seconds to obtain 11 at an output terminal amplified pulses having a pulse amplitude 12 A and a duration t'. The amplified pulses are connected via a 13 coupling device to the output terminals in such a manner as to 14 produce a spectral pattern having spectral rays at intervals fb.
19 FIG. 1 is a block and logic diagram of a preferred embodiment of the invention;
21 FIG. 2 is a waveform diagram which illustrates the 22 character of the logic level output pulses from pulse source 23 (2); and 24 Table I illustrates the effect of pulse width on the 25 pulse amplitude and the spectral bandwidth.
^ `~ ~1B~g6 D-22,344 3 The circuit of the invention is shown in FIG. 1. It should be noted that the purpose of the invention is to accept ~ as an input a base frequency from a pulse source such as 2, and 6 to provide as an output harmonics of that base frequency.
7 Therefore, logic level pulses may be obtained directly from a 8 pulse source 2 as shown or they may be made available from some 9 other source which is external to the other elements of the circuit shown in FIG. l. In either case, the character of the 11 pulses supplied on path 4 should be as shown in FIG. 2. The 12 time interval between pulses T is, of course, rela-ted to the base 13 frequency, i.e., the pulse repetition rate of the logic level 1~ pulses. The pulse repetition rate fb = l/T can be any value that is desired and which is within the operating range of the 16 components as illustrated. It is important to note that the 17 output frequency to load 32 will in all cases have as one 18 spectral ray the base frequency fb. Referring again to FIG. l, 19 a switching amplifier 6 includes an AND-gate 8 which has one in~
put connected to receive the logic level pulses on path 4 ana 2~ has another input connected to a pulse logic level so that the ~2 appearance of a pulse on path 4 will switch AND-gate 8 to its 23 on position applying a bias voltage to transistor 14, thereby, 24 turning on transistor 14. While one logic device is shown for switching amplifier 6,any number of such devices may be 26 employed so long as they provide as an output an open collector 27 such as is provided by transistor 14. Further, it should be 28 understood that a transistor, such as 14, may be included as ~ 9 ~
D-22,344 1 a part of AND-gate 8 and, therefore, a separate transistor 2 would not then be required. In addition, the open-collector 3 is not required if lower amplitudes can be tolerated. The collector of transistor 14 is connected via path 16, primary winding 18 of transformer 20, and resistor 22 to the supply 6 source of positive voltage +V. Rather than being at normal 7 logic levels, such as a binary `'0" which is represented by a 8 voltage of approximately 0.4 volts and a binary "1" which is 9 represented by a voltage of approximately 2.4 volts, the power supply voltage +V is in the order of +10 to +15 volts. Since 11 this ~V voltage could be supplied by well known power supply 12 circuits, the power supply is not shown. It may be seen then 13 that the logic level pulses on path 4 are essentially amplified 14 by the action of the switching amplifier 6 operating in con-junction with the power supply which has a voltage much higher 16 than that employed in the logic level circuitry. As noted 1~ above, logic levels may be employed where lower amplitude 18 spectra can be tolerated. Transformer 20 serves as the collector 19 lOâd, the resistor 22 provides current limiting which protects the transistor of the switching amplifier 6 from an overload, 21 and the capacitor 24 acts as a filter to keep the current 22 pulses from entering the power supply bus.
23 As may be seen by referring to FIG. 2, the input pulses 24 occur at intervals of T = l/fb and have a duration t'. Each input pulse causes the AND-gate 8 to be gated on so that the 26 bias voltage applied to the base electrode causes transistor 14 27 to conduct for t' seconds. Between pulses AND-gate 8 is turned 28 off for T - t' seconds, so that the bias voltage applied to ~ ~ 11 6 ~ 6 9 6 D-22~344 l the base electrode causes transistor 14 to be biased off for this same interval. When transistor 14 is biased to conduct, 3 a current pulse passes from power supply +V through resistor 22,
SU~ARY OF THE INVENTION
7 A baseband spectrum generator includes a source of 8 logic level pulses, having a pulse rate of fb and a pulse width 9 of t', which logic level pulses turn on a switching amplifier at intervals of T = l/fb for a duration of t' seconds to obtain 11 at an output terminal amplified pulses having a pulse amplitude 12 A and a duration t'. The amplified pulses are connected via a 13 coupling device to the output terminals in such a manner as to 14 produce a spectral pattern having spectral rays at intervals fb.
19 FIG. 1 is a block and logic diagram of a preferred embodiment of the invention;
21 FIG. 2 is a waveform diagram which illustrates the 22 character of the logic level output pulses from pulse source 23 (2); and 24 Table I illustrates the effect of pulse width on the 25 pulse amplitude and the spectral bandwidth.
^ `~ ~1B~g6 D-22,344 3 The circuit of the invention is shown in FIG. 1. It should be noted that the purpose of the invention is to accept ~ as an input a base frequency from a pulse source such as 2, and 6 to provide as an output harmonics of that base frequency.
7 Therefore, logic level pulses may be obtained directly from a 8 pulse source 2 as shown or they may be made available from some 9 other source which is external to the other elements of the circuit shown in FIG. l. In either case, the character of the 11 pulses supplied on path 4 should be as shown in FIG. 2. The 12 time interval between pulses T is, of course, rela-ted to the base 13 frequency, i.e., the pulse repetition rate of the logic level 1~ pulses. The pulse repetition rate fb = l/T can be any value that is desired and which is within the operating range of the 16 components as illustrated. It is important to note that the 17 output frequency to load 32 will in all cases have as one 18 spectral ray the base frequency fb. Referring again to FIG. l, 19 a switching amplifier 6 includes an AND-gate 8 which has one in~
put connected to receive the logic level pulses on path 4 ana 2~ has another input connected to a pulse logic level so that the ~2 appearance of a pulse on path 4 will switch AND-gate 8 to its 23 on position applying a bias voltage to transistor 14, thereby, 24 turning on transistor 14. While one logic device is shown for switching amplifier 6,any number of such devices may be 26 employed so long as they provide as an output an open collector 27 such as is provided by transistor 14. Further, it should be 28 understood that a transistor, such as 14, may be included as ~ 9 ~
D-22,344 1 a part of AND-gate 8 and, therefore, a separate transistor 2 would not then be required. In addition, the open-collector 3 is not required if lower amplitudes can be tolerated. The collector of transistor 14 is connected via path 16, primary winding 18 of transformer 20, and resistor 22 to the supply 6 source of positive voltage +V. Rather than being at normal 7 logic levels, such as a binary `'0" which is represented by a 8 voltage of approximately 0.4 volts and a binary "1" which is 9 represented by a voltage of approximately 2.4 volts, the power supply voltage +V is in the order of +10 to +15 volts. Since 11 this ~V voltage could be supplied by well known power supply 12 circuits, the power supply is not shown. It may be seen then 13 that the logic level pulses on path 4 are essentially amplified 14 by the action of the switching amplifier 6 operating in con-junction with the power supply which has a voltage much higher 16 than that employed in the logic level circuitry. As noted 1~ above, logic levels may be employed where lower amplitude 18 spectra can be tolerated. Transformer 20 serves as the collector 19 lOâd, the resistor 22 provides current limiting which protects the transistor of the switching amplifier 6 from an overload, 21 and the capacitor 24 acts as a filter to keep the current 22 pulses from entering the power supply bus.
23 As may be seen by referring to FIG. 2, the input pulses 24 occur at intervals of T = l/fb and have a duration t'. Each input pulse causes the AND-gate 8 to be gated on so that the 26 bias voltage applied to the base electrode causes transistor 14 27 to conduct for t' seconds. Between pulses AND-gate 8 is turned 28 off for T - t' seconds, so that the bias voltage applied to ~ ~ 11 6 ~ 6 9 6 D-22~344 l the base electrode causes transistor 14 to be biased off for this same interval. When transistor 14 is biased to conduct, 3 a current pulse passes from power supply +V through resistor 22,
4 the primary winding 18 of transformer 20, path 18 and the collector emitter junction of transistor 14 to ground. These 6 pulses induce an output voltage in the secondary 26, of trans-7 former 20, which is connected to load 32. The output spectrum 8 and power level depends upon, the pulse amplitude A obtained 9 through transistor 14, transformer 18 and current-limiting resistor 22 when the switching amplifier 6 is conducting, and ll the pulse duration ~pulse width) t'. The spectral bandwidth 12 is inversely proportional to t'. Output power levels as a 13 function of t' are given in Table I. The roll off at 4 kHz, 14 shown in Table I, is actually caused by frequency amplitude characteristics of the transformer used during tests. The 16 transformer was designed to provide a flat frequency response 17 between the frequencies 12 - 999 kHz. The high frequency roll 18 off is due to the pulse width t'. This can be easily calculated 19 using a Fourier series. It is of particular interest to note that the output levels range, for this particular configuration, 21 from -3 to ~6 dBm per spectral ray or tone.
22 While the invention has been particularly shown and 23 described with reference to a preferred embodiment thereof, it 24 will be understood by those skilled in the art that changes in form and detail may be made therein without departing from 26 the spirit and scope of the invention. For example, switching 27 amplifier 6 which is shown as an AND-gate in series with a 28 transistor 14 having an open collector arrangement may be
22 While the invention has been particularly shown and 23 described with reference to a preferred embodiment thereof, it 24 will be understood by those skilled in the art that changes in form and detail may be made therein without departing from 26 the spirit and scope of the invention. For example, switching 27 amplifier 6 which is shown as an AND-gate in series with a 28 transistor 14 having an open collector arrangement may be
- 5 -3l 1 160~96 D-22,344 l replaced by a Hex Inverter of the 7406 type having an open 2 collector output. Further, arrangement 6 may be replaced 3 by an open-collector buffer type 7407/5407 or peripheral driver 71 t es 5711, 5712, 5713, 5714.
l9 e~
l9 e~
Claims (2)
What is claimed is:
1. Apparatus for generating a plurality of carrier frequencies that are harmonically related to a carrier frequency fb comprising:
a source for generating logic level pulses having a repetition rate fb and durations td on an output thereof;
a gating circuit having an input terminal connected to the out-put of said pulse source, said gating circuit being responsive to said pulses for providing a bias voltage on an output terminal on the occurrence of each pulse;
a source of DC power;
a transformer having one side of a primary winding connected to one side of said power source and having a secondary winding adapted for connection to a utilization device; and a transistor having a base connected to the output terminal of said gating circuit, an emitter connected to the other side of said power source, and a collector connected to the other side of said primary winding;
said transistor periodically being responsive to bias voltage from said gating circuit for drawing primary conduction current in said primary winding and inducing the plurality of carrier frequency signals in said secondary winding which are harmonically related to the repetition frequency fb of the occurrence of said bias voltage.
D-22,344C
a source for generating logic level pulses having a repetition rate fb and durations td on an output thereof;
a gating circuit having an input terminal connected to the out-put of said pulse source, said gating circuit being responsive to said pulses for providing a bias voltage on an output terminal on the occurrence of each pulse;
a source of DC power;
a transformer having one side of a primary winding connected to one side of said power source and having a secondary winding adapted for connection to a utilization device; and a transistor having a base connected to the output terminal of said gating circuit, an emitter connected to the other side of said power source, and a collector connected to the other side of said primary winding;
said transistor periodically being responsive to bias voltage from said gating circuit for drawing primary conduction current in said primary winding and inducing the plurality of carrier frequency signals in said secondary winding which are harmonically related to the repetition frequency fb of the occurrence of said bias voltage.
D-22,344C
2. Apparatus for generating a plurality of carrier frequencies that are harmonically related to a carrier frequency fb comprising:
a source for generating logic level pulses having a repetition rate fb and durations td on an output thereof;
a source of DC power;
a transformer having one side of a primary winding connected to one side of said power source and having a secondary winding adapted for connection to a utilization device; and a hex-inverter having one terminal connected to the other side of said power source, an open collector output terminal connected to the other side of said primary winding, and an input terminal receiving pulses from said source; said hex-inverter being responsive to pulses for periodi-cally drawing conduction current in said primary winding and inducing the plurality of carrier frequency signals in said secondary winding which are harmonically related to the pulse repetition frequency fb.
a source for generating logic level pulses having a repetition rate fb and durations td on an output thereof;
a source of DC power;
a transformer having one side of a primary winding connected to one side of said power source and having a secondary winding adapted for connection to a utilization device; and a hex-inverter having one terminal connected to the other side of said power source, an open collector output terminal connected to the other side of said primary winding, and an input terminal receiving pulses from said source; said hex-inverter being responsive to pulses for periodi-cally drawing conduction current in said primary winding and inducing the plurality of carrier frequency signals in said secondary winding which are harmonically related to the pulse repetition frequency fb.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5897279A | 1979-07-20 | 1979-07-20 | |
| US058,972 | 1993-05-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1160696A true CA1160696A (en) | 1984-01-17 |
Family
ID=22020031
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000355464A Expired CA1160696A (en) | 1979-07-20 | 1980-07-04 | Baseband sprectrum generator using logic level input pulses |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1160696A (en) |
-
1980
- 1980-07-04 CA CA000355464A patent/CA1160696A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |
