Transmission system and repeater stations therefor

Claim 2

A repeater station for cable transmission of high frequency signals covering a predetermined wide band of frequencies and including a reference component having a predetermined frequency, said station comprising: an equalizer including a resistor T pad having two transverse resistive members and one leg member, a series resonant circuit connected in parallel across both transverse resistive members of said T, and a parallel resonant circuit connected in series with said leg member of said T, ends of said transverse resistive members defining input and output of said equalizer, while an end of said leg member is coupled to ground, said two resonant circuits having an adjustment means for adjusting the resonant frequency of each, and automatic control means having an input coupled to said equalizer output and output coupled to said adjusting means, said automatic control means responsive to a level of said reference cmmponent of said equalizer output to adjust the resonant frequencies of said two resonant circuits thereof and a corresponding substantially common frequency in a sense to maintain substantially constant said level of said reference component, whereby a signal level/frequency response slope of said equalizer is varied to correct for increasing losses in said transmitting cable of higher frequencies in said predetermined wide band frequencies.

Claim 3

A repeater station according to claim 1, including an amplifier having an input and an output and having a bandwidth corresponding to the predetermined frequency band, the input being connected to the output of the equaliser and the output being connected to the input of the automatic control means.

Claim 4

A signal transmission system, comprising a station source for producing electric signals over a predetermined band width and a pilot signal having a constant level of predetermined frequency, and a transmission cable connected to said station-source, the transmission cable being interrupted at intervals by repeater stations for boosting the electrical signals passing therealong, each repeater station having apparatus recited in claim 1 and responding to the pilot signal as said reference component.

Claim 5

A repeater station according to claim 1, wherein the automatic control means comprises a narrow band width frequency filter connected to said equalizer output for passing the said reference component a level detector connected to the filter to provide an output indicative of the level of the reference component, a comparator having a reference value representing a desired level for the reference component and connected to receive the output of the level detector, the comparator providing a control signal which is a function of the difference between the level of the reference component and the reference value, and further means for feeding the control signal to the adjustment means to control the signal level/frequency response slope of the equalizer in response thereto.

Claim 6

A repeater station according to claim 4, wherein the adjustment means of each resonant circuit comprises a variable capacity diode, and in which the control means is connected to each diode to supply each diode with a variable bias voltage for modifying the capacitance and thereby the tuning frequency of its corresponding resonant circuit.

Claim 7

A repeater station according to claim 1, including an attenuator having an input, an output and a control input for varying the attenuation of signals passing from the input to the output in controlled manner independently of the frequency of the signals, the output of the attenuator being connected to the input of the equaliser, and a second control means having an input connected to the output of the equaliser and an output connected to the control input of the attenuator, the second chain being responsive to a reference signal of predetermined reference frequency processed through the equaliser to control the attenuator in a sense to maintain the detected reference signal at a predetermined level.

Claim 8

A repeater station according to claim 6, wherein the frequency of the reference signal lies at the lower end of the predetermined frequency band width.

Claim 9

A repeater station according to claim 6, wherein the attenuator includes a PIN diode which is supplied with direct current by the output of the second automatic feedback control chain.

Claim 10

A signal transmission system, comprising a station source for producing electric signals over a predetermined band width together with a first pilot signal having a constant level at a first predetermined frequency and a second pilot signal having a constant level at a second predetermined frequency, and a transmission cable connected to said station source, the transmission cable being interrupted at intervals by repeater stations for boosting the electrical signals passing therealong, each repeater station having apparatus recited in claim 6 and responding to the first pilot signal as said reference component and the second pilot signal as said reference signal.

Claim 11

In a transmission system including a transmission line having a predetermined signal level/frequency characteristic for electrical signals having a predetermined bandwidth, a repeater station for equalizing the said electrical signals, the station comprising: an equalizer having a signal level/frequency characteristic which generally complements that of the transmission line and a control input for adjusting the said characteristic of said equalizer, feedback means for monitoring the output of said equalizer and responsive to a reference signal therein which is processed through said equalizer and has a frequency equal to an upper frequency in said predetermined bandwidth, said feedback means having an output connected to said control input of said equalizer and being operative to control the slope of the equalizer characteristic in a sense to maintain the monitored level of the reference signal at a predetermined level in order to compensate the characteristic of the equalizer for variations in the characteristic of said transmission line due to changes in temperature and line length over a limited range, said equalizer including a resistive T pad having two transverse resistive members and one leg member, a series resonant circuit connected in parallel acrosss both transverse resistive members of said T, and a parallel resonant circuit connected in series within said leg member of said T, ends of said transverse resistive members forming input and output of said equalizer and an end of said leg member coupled to ground, said two resonant circuits including adjustment means for adjusting the resonant frequency of each and coupled to said control input of said equalizer.

Claim 12

In a transmission system including a transmission line having a predetermined signal level/frequency characteristic for electrical signals having a predetermined bandwidth, a repeater station for equalizing the said electrical signals, the station comprising: an equalizer having a signal level/frequency characteristic which generally complements that of the transmission line and a control input for adjusting the said characteristic of said equalizer, feedback means for monitoring the output of said equalizer and responsive to a reference signal therein which is processed through said equalizer and has a frequency equal to an upper frequency in said predetermined bandwidth, said feedback means having an output connected to said control input of said equalizer and being operative to control the slope of the equalizer characteristic in a sense to maintain the monitored level of the reference signal at a predetermined level in order to compensate the characteristic of the equalizer for variations in the characteristic of said transmission line due to changes in temperature and line length over a limited range, said equalizer including a resistive T pad having two transverse resistive members and one leg member, a series resonant circuit connected in parallel acrosss both transverse resistive members of said T, and a parallel resonant circuit connected in series within said leg member of said T, ends of said transverse resistive members forming input and output of said equalizer and an end of said leg member coupled to ground, said two resonant circuits including adjustment means for adjusting the resonant frequency of each and coupled to said control input of said equalizer.

Claim 13

A repeater station according to claim 10, including an amplifier having a band width equal to the predetermined band width connected to amplify the output of the equaliser to boost the level of the equalised signals, a variable attenuator connected to attenuate the signals received by the equaliser uniformly and independently of frequency and having a control input for adjusting the attenuation provided by the attenuator, and second feedback means connected to detecting the said reference signal or another reference signal passed through the amplifier and to feed the control input of the attenuator to adjust the attenuator in a sense to maintain the detected reference signal at a second predetermined level.