GB2050764A - Improvements in or relating to duplex transceivers - Google Patents
Improvements in or relating to duplex transceivers Download PDFInfo
- Publication number
- GB2050764A GB2050764A GB7919965A GB7919965A GB2050764A GB 2050764 A GB2050764 A GB 2050764A GB 7919965 A GB7919965 A GB 7919965A GB 7919965 A GB7919965 A GB 7919965A GB 2050764 A GB2050764 A GB 2050764A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fed
- pair
- balancing resistors
- resistors
- tap
- 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.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/54—Circuits using the same frequency for two directions of communication
- H04B1/56—Circuits using the same frequency for two directions of communication with provision for simultaneous communication in two directions
Abstract
An AM duplex transceiver comprises two receiver aerials, a transmitter aerial, three detectors one of which is fed from the transmitter aerial and the other two of which are fed one from each of the receiver aerials, the receiver aerials being spaced so that at the frequency of operation a 90 DEG phase shift obtains between signals received at the receiver aerials, two pairs of serially connected balancing resistors wherein the balance between the resistors of each pair can be controlled, both pairs of balancing resistors being fed at one end from the said one detector and at the other end one from each of the said other two detectors, a multiplier having two input ports one of which is fed from a tap between one of the pairs of balancing resistors and the other of which is fed from a tap between the other pair of balancing resistors, an oscillator/modulator arrangement feeding the transmitter aerial and phase locked to the frequency of a received signal by means of a phase control signal fed from the multiplier, a first phase detector fed from the tap of one pair of balancing resistors, a delay device via which the said first phase detector is fed also from the tap of the said one pair of balancing resistors thereby to provide a control signal which is fed back to control the balance between the resistors of the said one pair and a second phase detector fed from the tap of the other pair of balancing resistors with an undelayed signal and via the said delay device with a delayed signal from the tap of the said one pair of balancing resistors from which an output signal from the transceiver is derived, thereby to produce a second control signal which is fed back to control the balance between the said other pair of balancing resistors.
Description
SPECIFICATION
Improvements in or relating to duplex transceivers
This invention relates to transceivers. More particularly it relates to AM duplex/rebroadcast transceivers and is a modification of the invention which forms the subject of our co-pending patent application No.
According to one aspect of the present invention an AM duplex transceiver comprises two receiver aerials, a transmitter aerial, three detectors one of which is fed from the transmitter aerial and the other two of which are fed one from each of the receiver aerials, the receiver aerials being spaced so that at the frequency of operation a 900 phase shift obtains between signals received at the receiver aerials, two pairs of serially connected balancing resistors wherein the balance between the resistors of each pair can be controlled, both pairs of balancing resistors being fed at one end from the said one detector and at the other end one from each of the said other two detectors, a multiplier having two input ports one of which is fed from a tap between one of the pairs of balancing resistors and the other of which is fed from a tap between the other pair of balancing resistors, an oscillator/modulator arrangement feeding the transmitter aerial and phase locked to the frequency of a received signal by means of a phase control signal fed from the the multiplier, a first phase detector fed from the tap of one pair of balancing resistors, a delay device via which the said first phase detector is fed also from the tap of the said one pair of balancing resistors thereby to provide a control signal which is fed back to control the balance between the resistors of the said one pair and a second phase detector fed from the tap of the other pair of balancing resistors with an undelayed signal and via the said delay device with a delayed signal from the tap of the said one pair of balancing resistors from which an output signal from the transceiver is derived, thereby to produce a second control signal which is fed back to control the balance between the said other pair of balancing resistors.
According to another aspect of the invention an
AM rebroadcast transceiver comprises two receiver aerials, for receiving a signal to be rebroadcast and a transmitter aerial, for rebroadcasting the received signal at the same frequency, three detectors one of which is fed from the transmitter aerial and the other two of which are fed one from each of the receiver aerials, the receiver aerials being spaced so that at the frequency of operation a 900 phase shift obtains between signals received at the receiver aerials, two pairs of serially connected balancing resistors wherein the balance between the resistors of each pair can be controlled, both pairs of balancing resistors being fed at one end from the said one detector and at the other end from each of the said other two detectors, a multiplier having two input ports one of which is fed from a tap between one of the pairs of balancing resistors, and the other of which is fed from a tap between the other pair of balancing resistors an oscillator/modulator arrangement feeding the transmitter aerial and phase locked to the frequency of a received signal by means of a phase control signal fed from the multiplier, a first phase detector fed from the tap of one pair of balancing resistors, a delay device via which the said first phase detector is fed also from the tap of the said one pair of balancing resistors thereby to provide a control signal which is fed back to control the balance between the resistors of the said one pair and a second phase detector fed from the tap of the other pair of balancing resistors with an undelayed signal and via the said delay device with a delayed signal from the tap of the said one pair of balancing resistors thereby to produce a second control signal which is fed back to control the balance between the said other pair of balancing resistors.
In a transceiver according to the present invention a 900 phase shift is produced by reason of the aerial spacing whereas in the transceiver according to our co-pending patent application
No. a 9OO shift is produced by a phase shift device.
The transceiver may include a first low pass filter via which the multiplier is fed from the said one pair of balancing resistors, a second low pass filter via which the said multiplier is fed from the said other pair of balancing resistors, third and fourth low pass filters via which the said first and second phase detectors respectively are arranged to feed respective pairs of balancing resistors, and a fifth low pass filter via which the multiplier is arranged to feed the phase control signal to the oscillator of the oscillator/modulator arrangement.
The transceiver may be arranged to include a further delay device which is introduced into the signal path between the transmitter aerial and the two pairs of balancing resistors to compensate for delay experienced by signals fed from the transmitter aerial to the receiver aerial.
The detectors may each comprise a pair of diodes and a transformer the receiver aerials being
arranged to feed the primary winding of the transformer and the diodes of each detector being connected to feed the two pairs of balancing resistors one detector to each pair.
One of the balancing resistors of each pair may be a voltage sensitive resistor to which a signal from an appropriate phase detector is fed so that the balance between the resistors of a pair is
controlled.
The oscillator/modulator arrangement may be arranged to feed the transmission aerial via a power amplifier.
The oscillator/modulator arrangement may comprise a separate modulator fed from a carrier frequency oscillator.
One embodiment of the invention will now be
described by way of example with reference to the
accompanying drawling, which is a generally
schematic block diagram of an AM rebroadcast transceiver.
The transceiver comprises two receiver aerials
la and 16 and one transmission aerial 2. In
operation of the transceiver signals received at the
receiver aerials la and 1 b are amplified and re
transmitted at the same frequency from the
transmission aerial 2. The present invention is
especially concerned with the rebroadcasting of
ampitude modulated signals although it is
envisaged that a system be provided which is in
effect a combination of the present system and a
system for FM rebroadcasting which is described
in our Patent No.
The receiving aerials 1 a and it and the
transmission aerial 2 are arranged to feed
detectors 3, 4 and 5 one detector to each aerial.
Since the detectors 3, 4 and 5 are constructed in a
similar manner the detector 3 only will be herein
described in detail. The detector 3 comprises a
double wound transformer 6, the primary winding
of which is fed from the aerial 1 a and the
secondary winding of which is centre tapped and
arranged to feed a pair of diodes 7 and 8. The
diodes are connected in parallel and provide the
output from the detector. The detector 3 is
arranged to feed a pair of serially connected
balancing resistors 9a, 9b and the detector 4 is
arranged to feed a similar pair of balancing
resistors 1 Oa and lOt. The balancing resistors
9a and lot are adjustable in value in response
to an applied control voltage and may take any
suitable form.The balancing resistors 9b and 1 Ob are fed also from the detector 5 via a delay
device 11 and an amplifier 12 so that the pair of balancing resistors 1 Oa and lot are fed at
one end from the detector 4 and at the other end
from the detector 5 and in a similar manner, the
pair of balancing resistors 9a and 9b are
connected so that they are fed at one end from the
detector 3 and at the other end from the detector
5. The transmission aerial 2 and the detector 5 are
coupled to an oscillator 13 which is fed via a
modulator 14 and a power amplifier 1 5 to the
transmission aerial 2 and the detector 5.In order
to phase lock the oscillator 13 to the received
carrier frequency, a multiplier 16 is provided
having two input ports 1 6a and 1 6b. The input
port 1 6a of the multiplier 16 is fed from a centre
tap 17 between the resistors 9a and 9b via an
amplifier 18 a low pass filter 19 and a further
amplifier 20. The im put port 1 6b of the multiplier
16 is fed in a similar manner from a centre tap 21
between the resistors 1 Oa and 1 Ob via an
amplifier 22 a low pass filter 23 and a further
amplifier 24. An output signal from the multiplier
1 6 is fed via a further low pass filter 25 to phase
lock the oscillator 13 to the received carrier
frequency.In order to cancel the modulation
which is present on the signal fed back between
the transmission aerial 2 and the receiving aerials
1 a and 16, two feedback control loops are
provided comprising phase detectors 26 and 27.
The phase detector 26 receives a signal applied
directly from the amplifier 20 and also a signal
applied indirectly from the amplifier 20 via an
amplifier 28 and a delay device 29. The output of the phase sensitive detector 26 is fed back via low pass filter 30 to control the value of the voltage sensitive resistor 9a.
In a similar manner the phase sensitive detector 27 is arranged to receive an output signal from the amplifier 24 and to receive also an output signal from the amplifier 20 delayed by means of the delay device 29. The output signal from the phase detector 27 is fed via a low pass filter 31 to control the value of the voltage sensitive resistor lot.
Thus it will be appreciated that the feedback control loops including the phase sensitive detectors 26 and 27 operate to balance the voltage sensitive resistors 9a and 1 Ot respectively, so that the correct proportion of feedback signal is fed back via the amplifier 12 to
cancel the feedback signal received by the aerials
1 a and 16 from the transmission aerial 2 whereby
any unwanted modulation at the output from the
amplifiers 20 and 24 is nullified.
It will be appreciated that the delay device 29 is
essential since it introduces a phase shift between
the received modulation and the transmitted
modulation applied to the modulator 14 via line
32 so that the feedback signal between the
transmission aerial 2 and the receiving aerials 1 a
and lb can be cancelled in the balancing resistors without cancelling the wanted received signal. It
will also be appreciated that if the device 29 were
omitted and the output of the amplifier 20 were
fed back directly to modulate the oscillator 13, the
unwanted feedback modulation which is
unavoidably transmitted from the transmission
aerial 2 to the receiving aerials 1 a and 16 would
be distinguishable from the received signal
modulation and so could not be selectively
cancelled.
Various modifications may be made to the
arrangement just before described without
departing from the scope of the invention and for example the detectors 3, 4 and 5 may take any suitable form of single or double port detector. In order to provide a rebroadcast system which
might alternatively be suitable for FM, the outputs from the filters 1 9 and 23 may be fed to an FM demodulator and the resultant audio frequency produced may be applied to frequency modulate the modulator 14. Such an FM system is described in detail in our patent No.
It will be apparent therefore that by suitably adapting the modulator 14 in accordance with the type of modulation required, the system described may alternatively be used for AM or FM.
It will be appreciated that two equipments as described could be used to comprise a full duplex single frequency radio link. The system could be converted to receive and transmit independent signals by disconnecting the AF input to modulator 1 7 and reconnecting the modulator to an external modulation source.
Claims (9)
1. An AM duplex transceiver comprising two receiver aerials a transmitter aerial, three detectors one of which is fed from the transmitter aerial and the other two of which are fed one from each of the receiver aerials, the receiver aerials being spaced so that at the frequency of operation a 900 phase shift obtains between signals received at the receiver aerials, two pairs of serially connected balancing resistors wherein the balance between the resistors of each pair can be controlled, both pairs of balancing resistors being fed at one end from the said one detector and at the other end from each of the said other two detectors, a multiplier having two input ports one of which is fed from a tap between one of the pairs of balancing resistors and the other of which is fed from a tap between the other pair of balancing resistors, an oscillator/modulator arrangement feeding the transmitter aerial and phase locked to the frequency of a received signal by means of a phase control signal fed from the multiplier, a first phase detector fed from the tap of one pair of balancing resistors, a delay device via which the said first phase detector is fed also from the tap of the said one pair of balancing resistors thereby to provide a control signal which is fed back to control the balance between the resistors of the said one pair and a second phase detector fed from the tap of the other pair of balancing resistors with an undelayed signal and via the said delay device with a delayed signal from the tap of the said one pair of balancing resistors from which an output signal from the transceiver is derived, thereby to produce a second control signal which is fed back to control the balance between the said other pair of balancing resistors.
2. An AM rebroadcast transceiver comprising two receiver aerials for receiving a signal to be rebroadcast and a transmitter aerial for rebroadcasting the received signal at the same frequency, three detectors one of which is fed from the transmitter aerial and the other two of which are fed one from each of the receiver aerials, the receiver aerials being spaced so that at the frequency of operation a 900 phase shift obtains between signals received at the receiver aerials, two pairs of serially connected balancing resistors wherein the balance between the resistors of each pair can be controlled, both pairs of balancing resistors being fed at one end from the said one detector and at the other end one from each of the said other detectors, a multiplier having two input ports one of which is fed from a tap between one of the pairs of balancing resistors, and the other of which is fed from a tap between the other pair of balancing resistors, an oscillator/modulator arrangement feeding the transmitter aerial and phased lock to the frequency of a received signal by means of a phase control signal fed from the multiplier, a first
phase detector fed from the tap of one pair of
balancing resistors, a delay device via which the said first phase detector is fed also from the tap of the said one pair of balancing resistors thereby to provide a control signal which is fed back to control the balance between the resistors of the said one pair and a second phase detector fed from the tap of the other pair of balancing resistors with an undelayed signal and via the said delay device with a delayed signal from the tap of the said one pair of balancing resistors thereby to produce a second control signal which is fed back to control the balance between the said other pair of balancing resistors, a signal from the said delay device being fed back to provide a modulating signal for the oscillator/modulator arrangement.
3. An AM rebroadcast transceiver as claimed in claim 1 or claim 2 including a first low pass filter via which the multiplier is fed from the said one pair of balancing resistors, a second low pass filter via which the multiplier is fed from the said other pair of balancing resistors, third and fourth low pass filters via which the said first and second phase detectors respectively are arranged to feed respective pairs of balancing resistors, a fifth low pass filter via which the multiplier is arranged to feed the phase control signal to the oscillator of the oscillator/modulator arrangement.
4. A transceiver as claimed in any preceding claim including a further delay device which is introduced into the signal path between the transmitter aerial and the two pairs of balancing resistors to compensate for delay experienced by signals fed from the transmitter aerial to the receiver aerial.
5. A transceiver as claimed in any preceding claim wherein the detectors each comprise a pair of diodes and a transformer the receiver aerials being arranged to feed the primary winding of the transformer and the diodes for each detector being connected to feed the two pairs of balancing resistors one detector to each pair.
6. A transceiver as claimed in claim 5 where one of the balancing resistors of each pair is a voltage sensitive resistor to which a signal from an appropriate phase detector is fed so that the balance between the resistors of the pair is controlled.
7. A transceiver as claimed in any preceding claim wherein the oscillator/modulator arrangement is arranged to feed the transmission aerial via a power amplifier.
8. A transceiver as claimed in any of claims 1 to 6 wherein the oscillator/modulator arrangement comprised a separate modulator fed from a carrying frequency oscillator.
9. A transceiver substantially as herein before described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7919965A GB2050764B (en) | 1979-05-17 | 1979-06-08 | Duplex transceivers |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7917181 | 1979-05-17 | ||
| GB7919965A GB2050764B (en) | 1979-05-17 | 1979-06-08 | Duplex transceivers |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2050764A true GB2050764A (en) | 1981-01-07 |
| GB2050764B GB2050764B (en) | 1983-08-10 |
Family
ID=26271558
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7919965A Expired GB2050764B (en) | 1979-05-17 | 1979-06-08 | Duplex transceivers |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2050764B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2458952A1 (en) * | 1979-06-08 | 1981-01-02 | Plessey Handel Investment Ag | AMPLITUDE MODULATION AMPLITUDE TRANSMITTER-RECEIVER OPERATING IN DUPLEX |
| EP0128933A1 (en) * | 1982-12-21 | 1984-12-27 | Motorola, Inc. | Improved isolation method and apparatus for a same frequency repeater |
-
1979
- 1979-06-08 GB GB7919965A patent/GB2050764B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2458952A1 (en) * | 1979-06-08 | 1981-01-02 | Plessey Handel Investment Ag | AMPLITUDE MODULATION AMPLITUDE TRANSMITTER-RECEIVER OPERATING IN DUPLEX |
| EP0128933A1 (en) * | 1982-12-21 | 1984-12-27 | Motorola, Inc. | Improved isolation method and apparatus for a same frequency repeater |
| EP0128933A4 (en) * | 1982-12-21 | 1985-09-02 | Motorola Inc | Improved isolation method and apparatus for a same frequency repeater. |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2050764B (en) | 1983-08-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 19990607 |