CA1290412C - High frequency signal apparatus and method of forming same - Google Patents
High frequency signal apparatus and method of forming sameInfo
- Publication number
- CA1290412C CA1290412C CA000575715A CA575715A CA1290412C CA 1290412 C CA1290412 C CA 1290412C CA 000575715 A CA000575715 A CA 000575715A CA 575715 A CA575715 A CA 575715A CA 1290412 C CA1290412 C CA 1290412C
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- Prior art keywords
- component
- frequency
- transmission line
- signal
- impedance
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/04—Control of transmission; Equalising
Abstract
HIGH FREQUENCY SIGNAL APPARATUS
AND METHOD OF FORMING SAME
ABSTRACT OF TEE DISCLOSURE
The frequency response of a component whose output decreases past a first frequency is extended by employing apparatus which provides for a signal source to be coupled to a component transmission line through a coupling impedance of about zero. The transmission line is resonant at a second frequency greater than the first frequency and the characteristic impedance of the transmission line is selected such that the voltage drop at or near direct current across the component is about equal to the voltage drop across the component at the second frequency. The method of operation comprises providing a signal, forming a transmission line which is resonant at the second frequency and coupling the transmission line to both the component and the signal source. The characteristic impedance of the transmission line is adjusted such that the voltage across the component at or near direct current is about equal to the voltage across the component at the second frequency.
AND METHOD OF FORMING SAME
ABSTRACT OF TEE DISCLOSURE
The frequency response of a component whose output decreases past a first frequency is extended by employing apparatus which provides for a signal source to be coupled to a component transmission line through a coupling impedance of about zero. The transmission line is resonant at a second frequency greater than the first frequency and the characteristic impedance of the transmission line is selected such that the voltage drop at or near direct current across the component is about equal to the voltage drop across the component at the second frequency. The method of operation comprises providing a signal, forming a transmission line which is resonant at the second frequency and coupling the transmission line to both the component and the signal source. The characteristic impedance of the transmission line is adjusted such that the voltage across the component at or near direct current is about equal to the voltage across the component at the second frequency.
Description
4~2 - 1 - RCA 83,~85 HIGH FREQ~ENCY SIGNAL ~P~ARATUS
AND METHOD OF F~RMING S~ME
The invention relates to an apparatus and method for increasing the frequency response of a component whose output decreases at high frequency.
The invention described herein was made in the performance of work under contract to NASA.
BACKGROUND OF THE INVENTION
Recent trends in high bit rate communication dictate a need for a signal processing system which can operate from direct current (DC) to microwave frequencies.
Unfortunately, many components such as circuits, semiconductor devices and in particular, laser diodes, have an output signal which decreases with increasing frequency.
For example, laser diodes are typically modeled as a resistance in parallel with a capacitive impedance.
Therefore, as the frequency increases, the capacitive impedance decreases which decreases the component input impedance, thus decreasing the applied voltage and the output signal of the device.
Typically, in order to increase the operating frequency, devices would be designed with reduced capacitance. These devices are then mounted such that the length of the lead wires is minimized to reduce any series inductance. Further, since the resistance of the laser diode is typically about 5 ohm (~) a resistor of about 45 n would be placed in series with the device. This additional resistance provides an impedance match thereby resultlng in a low reflection of a transmitted s.ignal when the device is connected to a coaxial cable having a 50 n characteristic impedance. Previously, it has been considered necessary to obtain low reflection, and therefore matching, to achieve a flat frequency response from DC to microwave frequencies.
M. Toda in concurrently filed and commonly assigned Canadian Application Serial No. 575,714, entitled "High Frequency Signal Driver and Method Of Forming Same", 9~ 2 -2- RCA 83,885 filed concurrently herewith, discloses a si~nal processlng system in which a transmission line is coupled between a means for providi~g a signal and a component. The transmission line is resona~t at a frequency such that the pea~ing effect o the ou~put signal at the resonant frequency compensates for ~he decrease in the component's output signal, ~hereby extending the frequency response of the component. In particular a coupling impedance, which is positioned between the signal source and the transmission line, controls the amount of peaking such as to obtain a flat frequency response.
Both the series resistor used for impedance matching in the conventional design and the coupling impedance disclosed by M. Toda generate heat. Typically, this heat generation requires that a laser device package be designed such the resistor is located outside the package so as to readily dissipate the generated heat.
However, the requirements of maintaining short lead wires in high frequency devices in combination with the mechanical constraints of laser packages make the use of an outside resistor partlcularly difficult. Further, this additional resistor reduces the laser's output signal due to resistive losses.
Therefore, it would be desirable to eliminate the use of a resistor and also to extend the frequency response of a component whose outpwt signal decreases at high frequency.
SUMMARY OF THE INVENTION
A signal processing system for obtaining a flat ~E~ response of a component whose output signal amplitude decreases as frequency increases past a first frequency comprises a signal means for providing a signal which is coupled to a component transmission line. The component transmission line is coupled to the component and a coupling impedance of about zero is positioned between the signal means and the component transmission line. The component transmission line is resonant at a second frequency which is greater than the first frequency and -3- RCA 83,885 exhibits a characteristic impedance such that the voltage a~ro~s the component at a low frequency limit is about egual to the vo}tage across ~he component at the second fre~lency. The invention also includes a method for S obtaining a flat fre~uency response for a component w~ose ~outpu~ decreases past a first frequency. The method comprises forming a transmission line which ls resonant at a second frequency greater than ~he first freguency, providing a signal, coupling the signal to the transmis^cion line and coupling the transmission line to the component.
,The characteristic impedance of the txansmission line is adjusted such that the voltage across the component at a low frequency limit is about equal to the voltage across the component at the second frequency.
It is an object of this invention to increase the frequency response of a component whose output decreases at high frequency.
It is an advantage of this invention that heat producing components are eliminated.
It is a further advantage of this inventlon that the output of the component is increased.
BRIEF DESCRIPTION OF THE DRAWING
The features of the invention believed to be novel are set forth with particularity in the appended claims. The inventiorl itself, however, both as to organization and method of operation, together with further objects and advantages thereo~, may best be understood by reference to the following description taken in conjunction with the accompanying drawing(s) in which:
FIGURE 1 is a schematic diagram of an embodiment of the invention.
FIGURE 2 is an output response curve resulting from the signal processing system of FIGURE 1.
FIGURE 3 is a perspective view of a mounted optical signal processing system of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In FIGURE 1 a signal processin~ system 10 compr1ses a signal means 11 for providing a slgnal 11 and ~.291~
~4- RCA 83,885 which typically co~prises a signal voltage source 12 and a source matched resistance 14. The source matched resistance 14 is coupled to a source transmission line 16 having a ~irst characteristic impedance Z1. The source transmistslonOline, 16 is coupled to a component transmission (~i line 20"having an lmpedance of about 2ero ohms positioned ,~. therebetween. The component transmisslon line 20 has a second characteristic impedance Z2 which is less than the first characteristic impedance Zl and is coupled to a component 22 such as a semiconductor laser diode.
~ The signal means 11 may comprise the signal voltage source 12 and the source matched impedance 14. The signal voltage source 12 may be any source which provides a signal with a range of frequencies, such as a transistor amplifier to transmit digital or analog signals. The source matched resista~lce 14 is typically a resistance internal to the signal source and is typically between about 10 to 50 Q. Alternatively, the signal means ll may be a connector or a transmission line which can be coupled to another transmission line which provides the signal.
The source transmission line 16 may be any arbitrary length, including zero, and is typically a metalllzed strip line formed on a ceramic plate whose metallization, and thereby the first characteristic impedance Z1r may be altered by standard photolithographic and etching techniques. Preferably, the first characteristic impedance Z1 is about equal to the source matched resistance 14. The source transmission line 16 may also be a coaxial cable. It should be understood that additional transmission lines or connectors may be coupled between the signal means ll and the source transmission line 16.
The component transmission llne 20 is lnitially resonant at a second frequency which is greater than a first frequency at which the output of the component 22 begins to decrease. For a laser diode, the resonant frequency is typically chosen to be between about 1.5 to 3 times greater than the frequency at which the output -5- RCA 83,885 voltage is at the -3 declbel (db) level. This resonance typlcally results from the length of the component transmission line 20 being about equal to one-guarter of the wavelength (A) in ~he material. For example, the component transmission line 20 will typically be about 1.45 centimeters (cm) for a chosen resonant frequency of about 3.4 gigahertz (G~z) in a transmission line having a propagation velocity of about 1. 95 X 108 meters per second (m/sec). A peaking ef~ect in the output of the component 22 occurs when the frequency of the transmitted signal reaches this resonant frequency. The magnitude of this peaking is determined by the difference between the source impedance of the component transmission line 20 and the second characteristic impedance Z2- When the source impedance of the component transmission line and the second characteristic impedance Z2 are about equal, no peaking will occur. As the difference between these impedances becomes greater, the magnitude of the peak also becomes greater until it reaches its maximum amplitude when the source impedance matches the input impedance of the component transmission line 20. The source impedance is the eguivalent impedance from the component transmission line 20 toward the signal means 11. When the source matched resistance 14 is approximately equal to the first characteristic impedance Z1, the source impedance of the component transmission line 20 is typically about equal to the value of the first characteristic impedance Zl. The input impedance is the equivalent impedance of the component transmission line 20 toward the component 22. At the resonant frequency, the input impedance is about equal to the square of the second characteristic impedance Z2 divided by a load i.mpedance. The load impedance is typically about equal to the component 22 impedance, although the connections between the component 22 and the 3s component transmission line 20 may also be determined to form the load impedance by techniques well known in the art.
~.~904~
-6- RCA 83,885 Thus, the magnitude of the peaking may be altered by changing the value of the second characteristic impedance Z2 and the length of the component transmission line 20 and if they are chosen correctly the peaking effect S will compensate for the decreasiny output of the component 22. Typically, the second characteristic impedance Z2 and the length of the component transmission line 20 are chosen by monitoring the output of the component 22 to obtain an approximately flat frequency response. A flat frequency response typically varies les~ than 30 percent (%) and preferably less than 10%, and typically a laser diode is monitored by coupling its output to a PIN photodiode which is connected to a spectrum analyzer. The second characteristic impedance Z2 and the length of the component transmission line 20 may also be determined such that the power to the component 22 at the low frequency limit is about equal to the power to the component 22 at the resonant frequency. The low frequency limit being the low frequency output near direct current, such as between 0 and 50 MHz and preferably direct current, in which other components such as capacitors which decrease the output near direct current are not considered. As sho~l in FIGURE
2, a second characteristic impedance Z2 of about 30 n results in an approximately flat response to ab~ut 3.4 GHz.
This flat response is obtained by using a source transmission which has a 50 n characteristic impedance with a resonant frequency chosen to be about 3.4 GHz and the component transmission line is coupled to a laser diode modeled as a resistance of about 5 n in parallel with a capacitance of about 15 picofarad (pf). Additionally, at the resonant frequency, which is typically between 1 to 10 GHz, the impedance of the component is small and the characteristic impedance of the component transmission line 20 is typically greater than the component 22. Further, the characteristic impedance of the source transmission line 16 is typically greater than the characteristic impedance of the component transmission line 20.
-7~ RCA 83,885 It should be understood khat the source and input impedance of the component txansmission line 20 are not matched as in conventional quarter-wavelength impedance matching. Typically this impedance matching is consldered undesirable when attempting to obtain a flat fxequency response from DC to microwave frequencies since a maximum amplitude peak will occur at the resonant frequency thereby making this impedance matching more sultable for narrow bandpass applications. Further, when the component impedance is complex, such as encountered with a resistance in parallel with a capacitance, impedance matching becomes more difficult. Unlike conventional impedance matching having about zero reflection, the source impedance and input impedance of the component transmission line 20 are inte~tionally mismatched and generally a reflection between about 70% and 80% occurs at the component transmission line 20~ The component transmission line 20 is typically a metallized strip line formed on a ceramic plate whose metallization, and thereby the second characteristic impedance Z~, may be altered by standard photolithographic and etching technigues.
The component 22 is typically a laser diode which may be modeled as a resistor in parallel with a capacitor.
The resistance is typically between about 1 to 10 Q and the capacitance is typically between about 5 and 200 pf. It should be understood that the invention is equally applicable to other components such as circuits or semiconductors, including translstors, whose output decxeases at high frequency. As shown in FIGURE 3, a laser 302 is typically mounted such that a first electrical contact is soldered to a header 304 formed of copper. A
ribbon wire 310 about 0.5 millimeters (mm) in length connects the component transmission line 320, whlch is mounted on a ceramic plate 321 to a second electrical contact of the laser 302. A DC source 322 for blasing the laser is coupled to a choke 324 which is connected to the component transmission line 320. A DC blocking capacitor 326 is also positioned on the component transmisslon line ~2~
-a- RCA 83,8a5 320. The signal is delivered to the source transmission line 328 through a coaxial cable 330, and the source transmission line, in turn is coupled to a component transmission line 320. It should be understood that in a communication system the length of the source transmission line 16, shown in FIGURE 1, may be zero and the signal means 11, such as a transistor amplifier, may be directly connected to the component transmission line 20.
In operation, as depicted in FIGURE 1, the signal source ~2 provides a signal which may extend between DC and microwave frequencies. This signal passes through the source txansmission line 16 and through the component transmission line 20 to component 22. As the signal source increases in frequency, the output of the component 22 decreases. This decrease in output is compensated by the peaking effect of the quarter-wavelength component transmission line 20. The~p~;oper amount of peaking is controlled by adjusting~,the length and the characteristic impedance of the component transmission line such that the voltage across the component at the low frequency limit is about equal to the voltage across the component at the resonant frequency. Therefore, a flat frequency response is obtained even though an imp~dance mismatch occurs between the component transmission line 20 and the component 22 since the amount of reflection remains approximately constant at all frequencies. It should be understood that since the source matched impedance 14 is approximately equal to the first characteristic impedance Z1, an additional resonant or spurious peaks in the signal output are not formed since all the reflection from the load is absorbed by the source matched resistance 14.
The present invention significantly extends the flat frequency response of a component, such as a laser diode, while simplifying package design, increasing output signal amplitude, and reducing heat dissipation by eliminatlng a resistance. Further, the phase characteristics are approximately linear and therefore any ~290~.2 -9- RCA 83,885 digital information transmitted will not be significantly altered.
While only certain preferred features of the invention have been lllustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of th~ invention.
AND METHOD OF F~RMING S~ME
The invention relates to an apparatus and method for increasing the frequency response of a component whose output decreases at high frequency.
The invention described herein was made in the performance of work under contract to NASA.
BACKGROUND OF THE INVENTION
Recent trends in high bit rate communication dictate a need for a signal processing system which can operate from direct current (DC) to microwave frequencies.
Unfortunately, many components such as circuits, semiconductor devices and in particular, laser diodes, have an output signal which decreases with increasing frequency.
For example, laser diodes are typically modeled as a resistance in parallel with a capacitive impedance.
Therefore, as the frequency increases, the capacitive impedance decreases which decreases the component input impedance, thus decreasing the applied voltage and the output signal of the device.
Typically, in order to increase the operating frequency, devices would be designed with reduced capacitance. These devices are then mounted such that the length of the lead wires is minimized to reduce any series inductance. Further, since the resistance of the laser diode is typically about 5 ohm (~) a resistor of about 45 n would be placed in series with the device. This additional resistance provides an impedance match thereby resultlng in a low reflection of a transmitted s.ignal when the device is connected to a coaxial cable having a 50 n characteristic impedance. Previously, it has been considered necessary to obtain low reflection, and therefore matching, to achieve a flat frequency response from DC to microwave frequencies.
M. Toda in concurrently filed and commonly assigned Canadian Application Serial No. 575,714, entitled "High Frequency Signal Driver and Method Of Forming Same", 9~ 2 -2- RCA 83,885 filed concurrently herewith, discloses a si~nal processlng system in which a transmission line is coupled between a means for providi~g a signal and a component. The transmission line is resona~t at a frequency such that the pea~ing effect o the ou~put signal at the resonant frequency compensates for ~he decrease in the component's output signal, ~hereby extending the frequency response of the component. In particular a coupling impedance, which is positioned between the signal source and the transmission line, controls the amount of peaking such as to obtain a flat frequency response.
Both the series resistor used for impedance matching in the conventional design and the coupling impedance disclosed by M. Toda generate heat. Typically, this heat generation requires that a laser device package be designed such the resistor is located outside the package so as to readily dissipate the generated heat.
However, the requirements of maintaining short lead wires in high frequency devices in combination with the mechanical constraints of laser packages make the use of an outside resistor partlcularly difficult. Further, this additional resistor reduces the laser's output signal due to resistive losses.
Therefore, it would be desirable to eliminate the use of a resistor and also to extend the frequency response of a component whose outpwt signal decreases at high frequency.
SUMMARY OF THE INVENTION
A signal processing system for obtaining a flat ~E~ response of a component whose output signal amplitude decreases as frequency increases past a first frequency comprises a signal means for providing a signal which is coupled to a component transmission line. The component transmission line is coupled to the component and a coupling impedance of about zero is positioned between the signal means and the component transmission line. The component transmission line is resonant at a second frequency which is greater than the first frequency and -3- RCA 83,885 exhibits a characteristic impedance such that the voltage a~ro~s the component at a low frequency limit is about egual to the vo}tage across ~he component at the second fre~lency. The invention also includes a method for S obtaining a flat fre~uency response for a component w~ose ~outpu~ decreases past a first frequency. The method comprises forming a transmission line which ls resonant at a second frequency greater than ~he first freguency, providing a signal, coupling the signal to the transmis^cion line and coupling the transmission line to the component.
,The characteristic impedance of the txansmission line is adjusted such that the voltage across the component at a low frequency limit is about equal to the voltage across the component at the second frequency.
It is an object of this invention to increase the frequency response of a component whose output decreases at high frequency.
It is an advantage of this invention that heat producing components are eliminated.
It is a further advantage of this inventlon that the output of the component is increased.
BRIEF DESCRIPTION OF THE DRAWING
The features of the invention believed to be novel are set forth with particularity in the appended claims. The inventiorl itself, however, both as to organization and method of operation, together with further objects and advantages thereo~, may best be understood by reference to the following description taken in conjunction with the accompanying drawing(s) in which:
FIGURE 1 is a schematic diagram of an embodiment of the invention.
FIGURE 2 is an output response curve resulting from the signal processing system of FIGURE 1.
FIGURE 3 is a perspective view of a mounted optical signal processing system of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In FIGURE 1 a signal processin~ system 10 compr1ses a signal means 11 for providing a slgnal 11 and ~.291~
~4- RCA 83,885 which typically co~prises a signal voltage source 12 and a source matched resistance 14. The source matched resistance 14 is coupled to a source transmission line 16 having a ~irst characteristic impedance Z1. The source transmistslonOline, 16 is coupled to a component transmission (~i line 20"having an lmpedance of about 2ero ohms positioned ,~. therebetween. The component transmisslon line 20 has a second characteristic impedance Z2 which is less than the first characteristic impedance Zl and is coupled to a component 22 such as a semiconductor laser diode.
~ The signal means 11 may comprise the signal voltage source 12 and the source matched impedance 14. The signal voltage source 12 may be any source which provides a signal with a range of frequencies, such as a transistor amplifier to transmit digital or analog signals. The source matched resista~lce 14 is typically a resistance internal to the signal source and is typically between about 10 to 50 Q. Alternatively, the signal means ll may be a connector or a transmission line which can be coupled to another transmission line which provides the signal.
The source transmission line 16 may be any arbitrary length, including zero, and is typically a metalllzed strip line formed on a ceramic plate whose metallization, and thereby the first characteristic impedance Z1r may be altered by standard photolithographic and etching techniques. Preferably, the first characteristic impedance Z1 is about equal to the source matched resistance 14. The source transmission line 16 may also be a coaxial cable. It should be understood that additional transmission lines or connectors may be coupled between the signal means ll and the source transmission line 16.
The component transmission llne 20 is lnitially resonant at a second frequency which is greater than a first frequency at which the output of the component 22 begins to decrease. For a laser diode, the resonant frequency is typically chosen to be between about 1.5 to 3 times greater than the frequency at which the output -5- RCA 83,885 voltage is at the -3 declbel (db) level. This resonance typlcally results from the length of the component transmission line 20 being about equal to one-guarter of the wavelength (A) in ~he material. For example, the component transmission line 20 will typically be about 1.45 centimeters (cm) for a chosen resonant frequency of about 3.4 gigahertz (G~z) in a transmission line having a propagation velocity of about 1. 95 X 108 meters per second (m/sec). A peaking ef~ect in the output of the component 22 occurs when the frequency of the transmitted signal reaches this resonant frequency. The magnitude of this peaking is determined by the difference between the source impedance of the component transmission line 20 and the second characteristic impedance Z2- When the source impedance of the component transmission line and the second characteristic impedance Z2 are about equal, no peaking will occur. As the difference between these impedances becomes greater, the magnitude of the peak also becomes greater until it reaches its maximum amplitude when the source impedance matches the input impedance of the component transmission line 20. The source impedance is the eguivalent impedance from the component transmission line 20 toward the signal means 11. When the source matched resistance 14 is approximately equal to the first characteristic impedance Z1, the source impedance of the component transmission line 20 is typically about equal to the value of the first characteristic impedance Zl. The input impedance is the equivalent impedance of the component transmission line 20 toward the component 22. At the resonant frequency, the input impedance is about equal to the square of the second characteristic impedance Z2 divided by a load i.mpedance. The load impedance is typically about equal to the component 22 impedance, although the connections between the component 22 and the 3s component transmission line 20 may also be determined to form the load impedance by techniques well known in the art.
~.~904~
-6- RCA 83,885 Thus, the magnitude of the peaking may be altered by changing the value of the second characteristic impedance Z2 and the length of the component transmission line 20 and if they are chosen correctly the peaking effect S will compensate for the decreasiny output of the component 22. Typically, the second characteristic impedance Z2 and the length of the component transmission line 20 are chosen by monitoring the output of the component 22 to obtain an approximately flat frequency response. A flat frequency response typically varies les~ than 30 percent (%) and preferably less than 10%, and typically a laser diode is monitored by coupling its output to a PIN photodiode which is connected to a spectrum analyzer. The second characteristic impedance Z2 and the length of the component transmission line 20 may also be determined such that the power to the component 22 at the low frequency limit is about equal to the power to the component 22 at the resonant frequency. The low frequency limit being the low frequency output near direct current, such as between 0 and 50 MHz and preferably direct current, in which other components such as capacitors which decrease the output near direct current are not considered. As sho~l in FIGURE
2, a second characteristic impedance Z2 of about 30 n results in an approximately flat response to ab~ut 3.4 GHz.
This flat response is obtained by using a source transmission which has a 50 n characteristic impedance with a resonant frequency chosen to be about 3.4 GHz and the component transmission line is coupled to a laser diode modeled as a resistance of about 5 n in parallel with a capacitance of about 15 picofarad (pf). Additionally, at the resonant frequency, which is typically between 1 to 10 GHz, the impedance of the component is small and the characteristic impedance of the component transmission line 20 is typically greater than the component 22. Further, the characteristic impedance of the source transmission line 16 is typically greater than the characteristic impedance of the component transmission line 20.
-7~ RCA 83,885 It should be understood khat the source and input impedance of the component txansmission line 20 are not matched as in conventional quarter-wavelength impedance matching. Typically this impedance matching is consldered undesirable when attempting to obtain a flat fxequency response from DC to microwave frequencies since a maximum amplitude peak will occur at the resonant frequency thereby making this impedance matching more sultable for narrow bandpass applications. Further, when the component impedance is complex, such as encountered with a resistance in parallel with a capacitance, impedance matching becomes more difficult. Unlike conventional impedance matching having about zero reflection, the source impedance and input impedance of the component transmission line 20 are inte~tionally mismatched and generally a reflection between about 70% and 80% occurs at the component transmission line 20~ The component transmission line 20 is typically a metallized strip line formed on a ceramic plate whose metallization, and thereby the second characteristic impedance Z~, may be altered by standard photolithographic and etching technigues.
The component 22 is typically a laser diode which may be modeled as a resistor in parallel with a capacitor.
The resistance is typically between about 1 to 10 Q and the capacitance is typically between about 5 and 200 pf. It should be understood that the invention is equally applicable to other components such as circuits or semiconductors, including translstors, whose output decxeases at high frequency. As shown in FIGURE 3, a laser 302 is typically mounted such that a first electrical contact is soldered to a header 304 formed of copper. A
ribbon wire 310 about 0.5 millimeters (mm) in length connects the component transmission line 320, whlch is mounted on a ceramic plate 321 to a second electrical contact of the laser 302. A DC source 322 for blasing the laser is coupled to a choke 324 which is connected to the component transmission line 320. A DC blocking capacitor 326 is also positioned on the component transmisslon line ~2~
-a- RCA 83,8a5 320. The signal is delivered to the source transmission line 328 through a coaxial cable 330, and the source transmission line, in turn is coupled to a component transmission line 320. It should be understood that in a communication system the length of the source transmission line 16, shown in FIGURE 1, may be zero and the signal means 11, such as a transistor amplifier, may be directly connected to the component transmission line 20.
In operation, as depicted in FIGURE 1, the signal source ~2 provides a signal which may extend between DC and microwave frequencies. This signal passes through the source txansmission line 16 and through the component transmission line 20 to component 22. As the signal source increases in frequency, the output of the component 22 decreases. This decrease in output is compensated by the peaking effect of the quarter-wavelength component transmission line 20. The~p~;oper amount of peaking is controlled by adjusting~,the length and the characteristic impedance of the component transmission line such that the voltage across the component at the low frequency limit is about equal to the voltage across the component at the resonant frequency. Therefore, a flat frequency response is obtained even though an imp~dance mismatch occurs between the component transmission line 20 and the component 22 since the amount of reflection remains approximately constant at all frequencies. It should be understood that since the source matched impedance 14 is approximately equal to the first characteristic impedance Z1, an additional resonant or spurious peaks in the signal output are not formed since all the reflection from the load is absorbed by the source matched resistance 14.
The present invention significantly extends the flat frequency response of a component, such as a laser diode, while simplifying package design, increasing output signal amplitude, and reducing heat dissipation by eliminatlng a resistance. Further, the phase characteristics are approximately linear and therefore any ~290~.2 -9- RCA 83,885 digital information transmitted will not be significantly altered.
While only certain preferred features of the invention have been lllustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of th~ invention.
Claims (11)
1. A signal processing apparatus coupled to a component for applying a voltage across said component, said component having an impedance and whose output decrease when the frequency of an input signal increases past a first frequency, said apparatus comprising:
signal means for providing said input signal;
a component transmission line resonant at a second frequency greater than said first frequency; and a coupling impedance of about zero ohms coupled between said signal means and said component transmission line, said component transmission line being coupled to said component and having a characteristic impedance of a value such that the voltage across the component at a selected low frequency limit is about equal to the voltage across the component at said second frequency;
wherein said second frequency is between about 1.5to 3 times greater than the frequency at which the output of said component is at the -3 decibel level with respect to the output of said component at direct current.
signal means for providing said input signal;
a component transmission line resonant at a second frequency greater than said first frequency; and a coupling impedance of about zero ohms coupled between said signal means and said component transmission line, said component transmission line being coupled to said component and having a characteristic impedance of a value such that the voltage across the component at a selected low frequency limit is about equal to the voltage across the component at said second frequency;
wherein said second frequency is between about 1.5to 3 times greater than the frequency at which the output of said component is at the -3 decibel level with respect to the output of said component at direct current.
2. The signal processing apparatus of claim 1 wherein said component comprises a semiconductor laser diode.
3. The signal processing apparatus of claim 1 wherein the characteristic impedance of said component transmission line is greater than the impedance of said component of said second frequency.
4. The signal processing apparatus of claim 1 wherein said signal means comprises a signal source having a source matched resistance.
- 11 - CA 83,885
- 11 - CA 83,885
5. The signal processing apparatus of claim 4 wherein said signal source is only coupled to a source transmission line having a characteristic impedance and the source transmission line is only coupled to said component transmission line.
6. The signal processing apparatus of claim 5 wherein the characteristic impedance of said source transmission line is about equal to said source matched resistance.
7. A method for extending the flat frequency response of a component having a voltage thereacross and whose output signal amplitude decreases as the frequency of the output signal increases past a first frequency, said method comprising the steps of:
providing an input signal from a source;
forming a component transmission line which is resonant at a second frequency which is greater than said first frequency and which second frequency is between about 1.5 to 3 times greater than the frequency at which the output of said component is at the -3 decibel level with respect to the output of said component at direct current;
coupling said input signal to the component transmission line through a coupling impedance of about zero ohms;
coupling said component transmission line to the component; and selecting the characteristic impedance of said component transmission line such that the voltage across the component at a selected low frequency limit is about equal to the voltage across the component at said second frequency.
providing an input signal from a source;
forming a component transmission line which is resonant at a second frequency which is greater than said first frequency and which second frequency is between about 1.5 to 3 times greater than the frequency at which the output of said component is at the -3 decibel level with respect to the output of said component at direct current;
coupling said input signal to the component transmission line through a coupling impedance of about zero ohms;
coupling said component transmission line to the component; and selecting the characteristic impedance of said component transmission line such that the voltage across the component at a selected low frequency limit is about equal to the voltage across the component at said second frequency.
8. The method of claim 7 wherein said selecting step comprises selecting the length and the characteristic impedance of said component transmission - 12 - RCA 83,885 line such that the output signal of the component is about flat between direct current and said second frequency.
9. The method of claim 8 wherein said selecting step comprises selecting the length and characteristic impedance of said component transmission line such that said output signal varies less than 30%
in amplitude between DC and said second frequency.
in amplitude between DC and said second frequency.
10. The method of claim 8 wherein said selecting step comprises selecting the length and characteristic impedance of said component transmission line such that said output signal varies less than 10%
in amplitude between DC and said second frequency.
in amplitude between DC and said second frequency.
11. The method of claim 10 wherein said selecting step comprises selecting the impedance of said source and the input impedance of said component transmission line to be sufficiently mismatched to achieve a reflection between about 70% and 80% of the amplitude of said input signal at said component transmission line.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/104,614 US4849981A (en) | 1987-10-05 | 1987-10-05 | High frequency signal driver for a laser diode and method of forming same |
| US104,614 | 1987-10-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1290412C true CA1290412C (en) | 1991-10-08 |
Family
ID=22301423
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000575715A Expired - Fee Related CA1290412C (en) | 1987-10-05 | 1988-08-25 | High frequency signal apparatus and method of forming same |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4849981A (en) |
| JP (1) | JP2672351B2 (en) |
| CA (1) | CA1290412C (en) |
| DE (1) | DE3833696C2 (en) |
| FR (1) | FR2621755B1 (en) |
| GB (1) | GB2210759B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5008894A (en) * | 1990-03-30 | 1991-04-16 | Synrad, Incorporated | Drive system for RF-excited gas lasers |
| US5602865A (en) * | 1995-11-14 | 1997-02-11 | Synrad, Inc. | RF-excited gas laser system |
| US6941080B2 (en) * | 2002-07-15 | 2005-09-06 | Triquint Technology Holding Co. | Method and apparatus for directly modulating a laser diode using multi-stage driver circuitry |
| AT503460B1 (en) * | 2006-02-08 | 2008-04-15 | Kvm Tec Electronic Gmbh | DEVICE FOR RECEIVING SIGNALS VIA A WIRE WITH DEFINED WAVE RESISTANCE |
| US9620930B2 (en) * | 2015-07-29 | 2017-04-11 | Adtran, Inc. | Reflection based signal pre-emphasis |
| WO2019124211A1 (en) * | 2017-12-18 | 2019-06-27 | 日本電信電話株式会社 | Ic chip |
| US11387624B2 (en) | 2020-02-04 | 2022-07-12 | Analog Devices International Unlimited Company | Resonant laser driver |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US22374A (en) * | 1858-12-21 | Improvement in seeding-machines | ||
| GB455492A (en) * | 1935-03-07 | 1936-10-22 | Alan Dower Blumlein | Improvements in or relating to electric signal transmission lines |
| GB495815A (en) * | 1939-02-10 | 1938-11-18 | John Collard | Improvements in or relating to electric signal transmission systems |
| GB522004A (en) * | 1938-11-04 | 1940-06-06 | John Collard | Improvements in or relating to systems for the transmission of oscillations |
| GB580810A (en) * | 1943-10-01 | 1946-09-20 | John Collard | Improvements in or relating to high frequency impedance transformers |
| US3459942A (en) * | 1966-12-05 | 1969-08-05 | Gen Electric | High frequency light source |
| US4314212A (en) * | 1979-05-31 | 1982-02-02 | Q-Dot, Inc. | Transient data recorder systems |
| CH656738A5 (en) * | 1982-07-01 | 1986-07-15 | Feller Ag | LINE distributed LOW PASS. |
| JPS60118585U (en) * | 1984-01-20 | 1985-08-10 | 吉貝 寿治 | Bicycle brake lever housing cover |
| JPS60236273A (en) * | 1984-05-09 | 1985-11-25 | Mitsubishi Electric Corp | Photosemiconductor device |
| JPS62118585A (en) * | 1985-11-19 | 1987-05-29 | Matsushita Electric Ind Co Ltd | Light-emitting-diode driving device |
| US4704630A (en) * | 1986-11-18 | 1987-11-03 | Rca Corporation | Wide bandwidth display driver apparatus |
-
1987
- 1987-10-05 US US07/104,614 patent/US4849981A/en not_active Expired - Fee Related
-
1988
- 1988-08-25 CA CA000575715A patent/CA1290412C/en not_active Expired - Fee Related
- 1988-10-04 GB GB8823247A patent/GB2210759B/en not_active Expired - Fee Related
- 1988-10-04 FR FR888812953A patent/FR2621755B1/en not_active Expired - Fee Related
- 1988-10-04 JP JP63249173A patent/JP2672351B2/en not_active Expired - Lifetime
- 1988-10-04 DE DE3833696A patent/DE3833696C2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE3833696A1 (en) | 1989-04-20 |
| JPH01135203A (en) | 1989-05-26 |
| GB8823247D0 (en) | 1988-11-09 |
| FR2621755A1 (en) | 1989-04-14 |
| US4849981A (en) | 1989-07-18 |
| GB2210759B (en) | 1992-04-22 |
| GB2210759A (en) | 1989-06-14 |
| DE3833696C2 (en) | 1997-10-16 |
| JP2672351B2 (en) | 1997-11-05 |
| FR2621755B1 (en) | 1992-09-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |