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US2407213A - Radio relaying - Google Patents

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Publication number
US2407213A
US2407213A US540061A US54006144A US2407213A US 2407213 A US2407213 A US 2407213A US 540061 A US540061 A US 540061A US 54006144 A US54006144 A US 54006144A US 2407213 A US2407213 A US 2407213A
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frequency
waves
output
converter
filter
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Expired - Lifetime
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US540061A
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Tunick Harry
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RCA Corp
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RCA Corp
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Publication date
Priority claimed from US447225A external-priority patent/US2406932A/en
Application filed by RCA Corp filed Critical RCA Corp
Priority to US540060A priority Critical patent/US2407212A/en
Priority to US540061A priority patent/US2407213A/en
Priority to GB18179/44A priority patent/GB599549A/en
Application granted granted Critical
Publication of US2407213A publication Critical patent/US2407213A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/165—Ground-based stations employing angle modulation

Definitions

  • the present invention is directed towards radio relaying and is particularly useful for relaying angle, phase and frequency modulated waves.
  • One object of the invention is Vto provide an improved radio ⁇ relaying system in which waves received on one carrier of one mean frequency are retransmittedon a new carrier of different mean frequency, the retransmitted waves having reduced angle, phase or frequency deviation as compared to that received.
  • waves received with one degree of angle, phase or frequency deviation are retransmitted at the same carrier or mean frequency with, however, reduced deviation.
  • Figure 1 illustrates schematically a radio relaying system in which angle modulated waves received at one frequency are retransmitted at a different frequency with reduced deviation
  • Figure 2 is a modification of Figure 1 wherein the retransmitted waves are of the same mean or carrier frequency as received but with, however, reduced deviation;
  • Figure 3 is a modification of Figure 2.
  • the received waves ⁇ have a mean frequency of one thousand megacycles and a maximum frequency deviation of plus and minus 500,000 cycles.
  • the waves received upon the antenna 800 are amplified in amplifier 002 and then fed to the converter 804, Converter 804 is also fed from a local generator 806 whose frequency of operation may be 9 99 megacycles.
  • the output of converter 804 is fed to a filter 808 which passes into frequency divider 8I0 the difference frequency or one megacycle plus and minus 500,000 cycles. Assuming the frequency divider to have a frequency dividing factorof two. its output will be .5 megacycle plus and minus 250,000 cycles. If the frequency divider 8I0 has a dividing factor of, for example, five, then its output will be a frequency modulated wave having a mean frequency of .2 megacycle and a maximum deviation of plus and minus 100 000 cycles.
  • the output of the frequency divider 8 I 0 is combined in a converter SI2 with another portion of waves derived from local generator 806 having a lil cycles or 998.8 megacycles plus and minus 100,000
  • Figure 2 shows an arrangement for retransmit'-I ting at the same mean frequency as that received with, however, a reduction in frequency deviation of the received frequency or phase modulated waves.
  • Figure 2 is similar to Figure l with the exception that the generator 900, converter 902, and
  • ⁇ cycles is added from generator 900 ⁇ by the action of converter 902.
  • the sum frequency is ⁇ preferably selected by filter 904 and its output, as indicated, is one megacycle plus and minus 100,000 cycles.
  • Figure 3 is the same as Figure 2 with the exception that a filter
  • changes in frequency of the local high frequency source 806 prove substantially self-cancelling.
  • the drifts in frequency of thelocal oscillator .000 of Figure 2 are substantially eliminated in Figure 3 by using as the source of relatively low frequency local oscillations, the outputof divider i002 which has a dividing factor of ⁇ 2000.
  • the output of divider I002 willbe a wave of'.5 megacycle having a ⁇ maximum frequencydevia-A tion of plus andrminus 250 cycles, which deviation obviously may be neglected.
  • the output of filter 1000 will be .5 megacycle plus and minus 250,000 cycles.
  • Filter 904 thereupon passes one megacycle plus and minus 250,250 cycles which when combined with the 999 megacycle Wave from oscillator 006 in converter SI2 produces in the output of filter 8f4 a wave having a mean frequency of 1000 megacycles having a maximum deviation of plus and minus 250,250 cycles which is amplified by amplifierA 816 and re-radiated over antenna 818.
  • the method of reducing the phase or frequency deviation of phase or frequency modulated Waves which includes generating oscillations of relatively constant frequency, utilizing a portion of the generated oscillations to heterodyne the phase. or frequency modulated Waves down to a relatively low intermediate frequency, frequency dividing the waves of intermediate frequency, and utilizing another portion of the locally generated Waves to heterodyne the frequency divided waves to a higher mean frequency.
  • the method ofA reducing the phase or frequency deviation of a phase or frequency modulated Wave; which includes generating relatively constant frequency local oscillations, heterodyningA a portion of said locally generated oscillations with saidY phase or frequency modulated Waves to produce waves of intermediate frequency, frequency dividing the Waves of intermediate frequency, heterodyning the frequency divided energy with another portion of Wave energy' locally generated, filtering the product of the last-mentioned heterodyning process, and utilizing the, filtered output.
  • a radio relaying system for phase orfrequency modulated waves which includes an antenna for receiving phase or frequency modulatedwaves, an amplifier amplifying the received Waves, a converter to which said amplified Waves are. fed, a source of locally generated relatively constant frequency Waves, apparatus for feedingl a portionl of said locally generated Waves to said converter whereby in the output of said converter energy of intermediate frequency appears, a fil-ter for filtering the energy of intermediate frequency, a frequency divider for frequency dividing the filtered energy of intermediate frequency, a converter to. which the output of said frequency divider isv fed, circuits for feeding another portion of Waves, locally generated, to said second converter, a filter for filtering the heterodyned output of saidsecond converter, an amplifier coupled to. said last-mentioned filter, and a radiating antenna coupled to. said last mentioned amplifier.
  • the method of relaying waves which includes receiving the waves, heterodyning the waves. to an intermediate frequency, frequency dividing the Waves of intermediate frequency, adding ak wave of substantially constant f requency to the Waves resulting from frequency division, filtering the waves resulting from the addition, and utilizing the filtered Waves.
  • The, method of relay Waves which includes receiving the Waves, heterodyning the Waves to an intermediate frequency, frequency dividing the waves of intermediate frequency, adding a wave of relatively constant frequency to said frequency divided waves, filtering the waves resulting from said addition, and heterodyning the filtered waves to a relatively higher frequency suitable for re-radiation.
  • the method of receiving phase or frequency modulated Waves and retransmitting them at substantially the same mean frequency but with a changed phase or frequency deviation which includes receiving phase or frequency modulated waves, heterodyning the Waves to an intermediate frequency, changing the mean frequency of said Waves of intermediate frequency by a lprocess other than a heterodyning process, algebraically adding to the intermediate frequency Waves of changed frequency a wave of substantially constant frequency, filtering the waves resulting from the algebraic addition, and heterodyning the filtered waves to the same mean frequency as that received.
  • Apparatus for relaying received phase or frequency modulated Waves which includes an antenna for receiving such waves, a local source of heterodyning oscillations, apparatus for heterodyning energy derived from the received WavesV with Waves from said local source so as to produce Waves of intermediate frequency, a frequency divider for frequency dividing the Waves of intermediate frequency, a detector coupled to the output of said frequency divider, a generator of relatively low frequency Waves also coupled to said detector, a filter for filtering out from the output of said detector waves having the same mean frequency as said intermediate frequency, apparatus for utilizing another portion of the output of saidV local source of heterodyning oscillations for heterodyning the output of said lastmentioned filter to the same mean frequency as that received, and a radiating antenna for radiating Waves derived from the output of said last-mentioned heterodyning apparatus.
  • Apparatus for relaying phase or frequency modulated waves comprising a receiving antenna for receiving such Waves, an amplifier for amplifying waves picked up by said antenna, a converter coupled to the output of said amplifier, a local heterodyning oscillator, apparatus for feeding waves from said local oscillator to said converter, a filter for filtering the output of said converter, a frequency divider for frequency dividing the output of said filter, a second converter to Which the output of said frequency divider is fed, a generator of relatively constant frequency waves, a circuit for feeding the output of said generator to said second converter, the frequency of said generator being chosen so that in the output of said converter waves having the same mean frequency as are applied to the input of said frequency divider appear, a lter for filtering the output of said second converter, a third converter to which are fed the output of said last-mentioned filter and waves from said firstmentioned local heterodyning oscillator, a filter for filtering the output of said third converter, an amplifier for amplifying the output of said last-
  • the method of relaying received waves which includes receiving the waves, amplifying the Waves, frequency dividing a portion of the amplified Waves, locally generating Waves, heterodyning down in frequency another portion of said amplied Waves with a portion of said locally generated Waves, frequency dividing the heterodyned waves, combining the frequency divided heterodyned Waves with Waves derived from the frequency divided portion of the amplied received Waves, filtering the combined Waves, heterodyning the ltered waves up in frequency With another portion of the locally generated waves, ltering and amplifying the waves resulting from the last-mentioned heterodyning process, and radiating the ltered and amplified Waves.
  • a radio relay system comprising a receiving antenna, an amplier for amplifying Waves received by said receiving antenna, a converter to which a, portion of the output of said amplifier is fed, a frequency divider to which another portion of the output of said amplifier is fed, a local source of oscillations, circuits for feeding a portion of the output of said local source to said con- 6 verter, a, filter for filtering the output of said converter, a frequency divider for frequency dividing the output of said filter, a second converter to which the outputs of both of said frequency Y

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Superheterodyne Receivers (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Radio Relay Systems (AREA)

Description

H. rUNlcK RADIO RELAYING 2 Sh'eefs-Sheet l Original Filed June 16. 1942 Sept. 3, 1946. H, TUNICK 2,407,213
RADIO RELAYING original Filed .June 1s. 1942. 2 sheets-sheet 2 INVENTOR #ARGV TUN/6K BY 77%;
ATT/EA/IY )ons @nu tam Sgm kann All? Patented Sept. 3, 1946 2,407,213 RADIO RELAYING Harry Tuniek, Rye, N. Y., assgnor to Radio Corporation of America, a corporation of Dela- Ware Original application June 16, 1942, Serial No. 447,225. Divided and this application June 13, 1944, Serial No. 540,061
(Cl. Z50-15) Claims. 1
This is a division of my copending application Serial No. 447,225, filed June 16, 1942. Figures 1, 2, and 3 herein are, respectively, original Figures 8, 9, and 10 of my parent application as filed in the United States Patent Ofce.
The present invention is directed towards radio relaying and is particularly useful for relaying angle, phase and frequency modulated waves. One object of the invention is Vto provide an improved radio` relaying system in which waves received on one carrier of one mean frequency are retransmittedon a new carrier of different mean frequency, the retransmitted waves having reduced angle, phase or frequency deviation as compared to that received.
In a modification of the present invention, waves received with one degree of angle, phase or frequency deviation are retransmitted at the same carrier or mean frequency with, however, reduced deviation.
Other objects of my invention will appear as the more detailed description thereof proceeds, as will also advantages and other features.
Figure 1 illustrates schematically a radio relaying system in which angle modulated waves received at one frequency are retransmitted at a different frequency with reduced deviation;
Figure 2 is a modification of Figure 1 wherein the retransmitted waves are of the same mean or carrier frequency as received but with, however, reduced deviation; and
Figure 3 is a modification of Figure 2.
Referring to Figure 1, let it he Yassumed that the received waves` have a mean frequency of one thousand megacycles and a maximum frequency deviation of plus and minus 500,000 cycles. The waves received upon the antenna 800 are amplified in amplifier 002 and then fed to the converter 804, Converter 804 is also fed from a local generator 806 whose frequency of operation may be 9 99 megacycles. I
The output of converter 804 is fed to a filter 808 which passes into frequency divider 8I0 the difference frequency or one megacycle plus and minus 500,000 cycles. Assuming the frequency divider to have a frequency dividing factorof two. its output will be .5 megacycle plus and minus 250,000 cycles. If the frequency divider 8I0 has a dividing factor of, for example, five, then its output will be a frequency modulated wave having a mean frequency of .2 megacycle and a maximum deviation of plus and minus 100 000 cycles.
The output of the frequency divider 8 I 0 is combined in a converter SI2 with another portion of waves derived from local generator 806 having a lil cycles or 998.8 megacycles plus and minus 100,000
cycles.
Figure 2 shows an arrangement for retransmit'-I ting at the same mean frequency as that received with, however, a reduction in frequency deviation of the received frequency or phase modulated waves.
Figure 2 is similar to Figure l with the exception that the generator 900, converter 902, and
filter 904 have been added. Itis assumed that the frequency divider 8I0 hasja dividing factor of.`
ve, hence its output for the values assumed will be .2 megacycle plus and minus 100,000 cycles. To this divided output a low frequencyof 800,000
`cycles is added from generator 900`by the action of converter 902. The sum frequency is `preferably selected by filter 904 and its output, as indicated, is one megacycle plus and minus 100,000 cycles. To the output of filter 004 there is added in converter 8| 2 another portion of waves from the high frequency generator 806 and preferably filter 8 I4 is arranged to pass the sum frequency or 1000 megacycles plus and minus 100,000 cycles which is amplified by amplifier 8I6 and re-radiated over antenna 8 I 8.
Figure 3 is the same as Figure 2 with the exception that a filter |000 has been added after the frequency divider 8I0 and the low frequency oscillator 900 of Figure 2 has been replaced .by frequency dividers, filters, and amplifiers I 002 fed with waves from the output of amplifier 802. As in Figures 1, 2, and 3, it will be observed that changes in frequency of the local high frequency source 806 prove substantially self-cancelling. The drifts in frequency of thelocal oscillator .000 of Figure 2 are substantially eliminated in Figure 3 by using as the source of relatively low frequency local oscillations, the outputof divider i002 which has a dividing factor of`2000. Hence, the output of divider I002 willbe a wave of'.5 megacycle having a `maximum frequencydevia-A tion of plus andrminus 250 cycles, which deviation obviously may be neglected.
Assuming in Figure 3 the divider 850 to have a dividing factor of two, the output of filter 1000 will be .5 megacycle plus and minus 250,000 cycles. To this is added in converter 002 .5 megacycle plus and minus 250 cycles from the output of divider i002, Filter 904 thereupon passes one megacycle plus and minus 250,250 cycles which when combined with the 999 megacycle Wave from oscillator 006 in converter SI2 produces in the output of filter 8f4 a wave having a mean frequency of 1000 megacycles having a maximum deviation of plus and minus 250,250 cycles which is amplified by amplifierA 816 and re-radiated over antenna 818.
I claim:
1. The method of reducing the phase or frequency deviation of phase or frequency modulated Waves which includes generating oscillations of relatively constant frequency, utilizing a portion of the generated oscillations to heterodyne the phase. or frequency modulated Waves down to a relatively low intermediate frequency, frequency dividing the waves of intermediate frequency, and utilizing another portion of the locally generated Waves to heterodyne the frequency divided waves to a higher mean frequency.
2. The method ofA reducing the phase or frequency deviation of a phase or frequency modulated Wave; which includes generating relatively constant frequency local oscillations, heterodyningA a portion of said locally generated oscillations with saidY phase or frequency modulated Waves to produce waves of intermediate frequency, frequency dividing the Waves of intermediate frequency, heterodyning the frequency divided energy with another portion of Wave energy' locally generated, filtering the product of the last-mentioned heterodyning process, and utilizing the, filtered output.
3. A radio relaying system for phase orfrequency modulated waves which includes an antenna for receiving phase or frequency modulatedwaves, an amplifier amplifying the received Waves, a converter to which said amplified Waves are. fed, a source of locally generated relatively constant frequency Waves, apparatus for feedingl a portionl of said locally generated Waves to said converter whereby in the output of said converter energy of intermediate frequency appears, a fil-ter for filtering the energy of intermediate frequency, a frequency divider for frequency dividing the filtered energy of intermediate frequency, a converter to. which the output of said frequency divider isv fed, circuits for feeding another portion of Waves, locally generated, to said second converter, a filter for filtering the heterodyned output of saidsecond converter, an amplifier coupled to. said last-mentioned filter, and a radiating antenna coupled to. said last mentioned amplifier.
4. The method of relaying waves which includes receiving the waves, heterodyning the waves. to an intermediate frequency, frequency dividing the Waves of intermediate frequency, adding ak wave of substantially constant f requency to the Waves resulting from frequency division, filtering the waves resulting from the addition, and utilizing the filtered Waves.
5. The, method of relay Waves which includes receiving the Waves, heterodyning the Waves to an intermediate frequency, frequency dividing the waves of intermediate frequency, adding a wave of relatively constant frequency to said frequency divided waves, filtering the waves resulting from said addition, and heterodyning the filtered waves to a relatively higher frequency suitable for re-radiation.
6. The method of receiving phase or frequency modulated Waves and retransmitting them at substantially the same mean frequency but with a changed phase or frequency deviation which includes receiving phase or frequency modulated waves, heterodyning the Waves to an intermediate frequency, changing the mean frequency of said Waves of intermediate frequency by a lprocess other than a heterodyning process, algebraically adding to the intermediate frequency Waves of changed frequency a wave of substantially constant frequency, filtering the waves resulting from the algebraic addition, and heterodyning the filtered waves to the same mean frequency as that received.
'7. Apparatus for relaying received phase or frequency modulated Waves which includes an antenna for receiving such waves, a local source of heterodyning oscillations, apparatus for heterodyning energy derived from the received WavesV with Waves from said local source so as to produce Waves of intermediate frequency, a frequency divider for frequency dividing the Waves of intermediate frequency, a detector coupled to the output of said frequency divider, a generator of relatively low frequency Waves also coupled to said detector, a filter for filtering out from the output of said detector waves having the same mean frequency as said intermediate frequency, apparatus for utilizing another portion of the output of saidV local source of heterodyning oscillations for heterodyning the output of said lastmentioned filter to the same mean frequency as that received, and a radiating antenna for radiating Waves derived from the output of said last-mentioned heterodyning apparatus.
8. Apparatus for relaying phase or frequency modulated waves comprising a receiving antenna for receiving such Waves, an amplifier for amplifying waves picked up by said antenna, a converter coupled to the output of said amplifier, a local heterodyning oscillator, apparatus for feeding waves from said local oscillator to said converter, a filter for filtering the output of said converter, a frequency divider for frequency dividing the output of said filter, a second converter to Which the output of said frequency divider is fed, a generator of relatively constant frequency waves, a circuit for feeding the output of said generator to said second converter, the frequency of said generator being chosen so that in the output of said converter waves having the same mean frequency as are applied to the input of said frequency divider appear, a lter for filtering the output of said second converter, a third converter to which are fed the output of said last-mentioned filter and waves from said firstmentioned local heterodyning oscillator, a filter for filtering the output of said third converter, an amplifier for amplifying the output of said last-mentioned filter, and a radiating antenna fed by said last-mentioned amplifier.
9. The method of relaying received waves which includes receiving the waves, amplifying the Waves, frequency dividing a portion of the amplified Waves, locally generating Waves, heterodyning down in frequency another portion of said amplied Waves with a portion of said locally generated Waves, frequency dividing the heterodyned waves, combining the frequency divided heterodyned Waves with Waves derived from the frequency divided portion of the amplied received Waves, filtering the combined Waves, heterodyning the ltered waves up in frequency With another portion of the locally generated waves, ltering and amplifying the waves resulting from the last-mentioned heterodyning process, and radiating the ltered and amplified Waves.
10. A radio relay system comprising a receiving antenna, an amplier for amplifying Waves received by said receiving antenna, a converter to which a, portion of the output of said amplifier is fed, a frequency divider to which another portion of the output of said amplifier is fed, a local source of oscillations, circuits for feeding a portion of the output of said local source to said con- 6 verter, a, filter for filtering the output of said converter, a frequency divider for frequency dividing the output of said filter, a second converter to which the outputs of both of said frequency Y
US540061A 1942-06-16 1944-06-13 Radio relaying Expired - Lifetime US2407213A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US540060A US2407212A (en) 1942-06-16 1944-06-13 Radio relaying
US540061A US2407213A (en) 1942-06-16 1944-06-13 Radio relaying
GB18179/44A GB599549A (en) 1942-06-16 1944-09-22 Improvements in high-frequency radio relay stations

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US447225A US2406932A (en) 1942-06-16 1942-06-16 Wave conversion
US540061A US2407213A (en) 1942-06-16 1944-06-13 Radio relaying

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2500090A (en) * 1945-02-14 1950-03-07 Rca Corp Radio relaying
US2505043A (en) * 1946-09-23 1950-04-25 Radio Patents Corp Means for frequency conversion
US2534111A (en) * 1946-12-10 1950-12-12 Gen Electric Wave conversion system for transmitters and receivers
US2576115A (en) * 1947-02-07 1951-11-27 Int Standard Electric Corp Arrangement for transmitting electric signals occupying a wide frequency band over narrow band circuits
US2614211A (en) * 1950-05-13 1952-10-14 Bell Telephone Labor Inc Frequency controlled radio relaying system
US2666141A (en) * 1946-05-08 1954-01-12 James K Clapp Single side band mixer for moving target indicating radar systems
US2670437A (en) * 1948-01-10 1954-02-23 Morrison Montford Electronic tube oscillation system
US2691065A (en) * 1951-01-12 1954-10-05 Rca Corp Multiplex relay system
US2813977A (en) * 1947-07-26 1957-11-19 Westinghouse Electric Corp Frequency modulated oscillation generator
US2874222A (en) * 1954-10-25 1959-02-17 Philips Corp Single-sideband system
US2939918A (en) * 1954-08-24 1960-06-07 Freedman Nathan System for compressing bandwidth
US2971155A (en) * 1956-10-03 1961-02-07 Hurvitz Hyman Double reflex spectrum analyzer
US3369180A (en) * 1966-01-25 1968-02-13 Gen Telephone & Elect Constant frequency deviation non-demodulating microwave repeater
US3427543A (en) * 1964-05-29 1969-02-11 Tokyo Shibaura Electric Co Television fm sound broadcasting with high frequency deviation in st link
US3866122A (en) * 1973-01-02 1975-02-11 Itt FM communication system
US4134069A (en) * 1975-04-23 1979-01-09 Nippon Electric Co., Ltd. Single side band multiplex signal radio relay
US4247822A (en) * 1979-01-04 1981-01-27 Rca Corporation Frequency translation means
US4783843A (en) * 1986-05-23 1988-11-08 Peninsula Engineering Group, Inc. Split band filter for cellular mobile radio

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2500090A (en) * 1945-02-14 1950-03-07 Rca Corp Radio relaying
US2666141A (en) * 1946-05-08 1954-01-12 James K Clapp Single side band mixer for moving target indicating radar systems
US2505043A (en) * 1946-09-23 1950-04-25 Radio Patents Corp Means for frequency conversion
US2534111A (en) * 1946-12-10 1950-12-12 Gen Electric Wave conversion system for transmitters and receivers
US2576115A (en) * 1947-02-07 1951-11-27 Int Standard Electric Corp Arrangement for transmitting electric signals occupying a wide frequency band over narrow band circuits
US2813977A (en) * 1947-07-26 1957-11-19 Westinghouse Electric Corp Frequency modulated oscillation generator
US2670437A (en) * 1948-01-10 1954-02-23 Morrison Montford Electronic tube oscillation system
US2614211A (en) * 1950-05-13 1952-10-14 Bell Telephone Labor Inc Frequency controlled radio relaying system
US2691065A (en) * 1951-01-12 1954-10-05 Rca Corp Multiplex relay system
US2939918A (en) * 1954-08-24 1960-06-07 Freedman Nathan System for compressing bandwidth
US2874222A (en) * 1954-10-25 1959-02-17 Philips Corp Single-sideband system
US2971155A (en) * 1956-10-03 1961-02-07 Hurvitz Hyman Double reflex spectrum analyzer
US3427543A (en) * 1964-05-29 1969-02-11 Tokyo Shibaura Electric Co Television fm sound broadcasting with high frequency deviation in st link
US3369180A (en) * 1966-01-25 1968-02-13 Gen Telephone & Elect Constant frequency deviation non-demodulating microwave repeater
US3866122A (en) * 1973-01-02 1975-02-11 Itt FM communication system
US4134069A (en) * 1975-04-23 1979-01-09 Nippon Electric Co., Ltd. Single side band multiplex signal radio relay
US4247822A (en) * 1979-01-04 1981-01-27 Rca Corporation Frequency translation means
US4783843A (en) * 1986-05-23 1988-11-08 Peninsula Engineering Group, Inc. Split band filter for cellular mobile radio

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