US4238850A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transmitter/receiver for single channel duplex communication system
Assignee: STC PLC
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Filing: 1978-11-29
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Granted: 1980-12-09
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Expires: 1998-11-29
Abstract
Abstract A transmitter receiver which can be used for a cordless telephone using radio communication. The receiver produces direct conversion from the radio frequency. Local oscillator frequency is modulated by an audio signal to be sent, the modulated signals being passed through a dual splitting and combining network. The splitting network has directional properties for duplex operation. The receiver processes the signals through a differential amplifier to cancel unwanted signals.
Inventors
- 👤 Ian A. W. Vance
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:26
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40; H04B1/54
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
241 words
A transmitter/receiver for a single channel duplex communication system including a local oscillator for generating a frequency which is the center frequency of the single channel signals, means for frequency modulating the frequency output of said local oscillator with a first audio frequency signal, first and second means for directionally combining the local oscillator output in phase quadrature with audio frequency modulated signals received from the single channel, whereby a major portion of the local oscillator output is transmitted from each combining means to the single channel and a minor portion of the local oscillator output together with the received signals is applied from each combining means to first and second mixing means respectively, means for low pass filtering each of the outputs of the first and second mixing means, means for amplifying each of the outputs of the low pass filtering means to a constant level, separate means for differentiating each of the outputs of the amplifying means, means for multiplying the output of each differentiating means with the input of another differentiating means to provide (a) demodulated second audio frequency signal, signal means for subtracting a proportion of the first audio frequency signal from the demodulated second signal and means for feeding the output of the local oscillator in combination with a phase quadrature output of the local oscillator through said combining means to an aerial via which signals which are frequency-modulated with the second audio frequency are received.
Claim 2
Dependent Claim
241 words
A transmitter/receiver for a single channel duplex communication system including a local oscillator for generating a frequency which is the center frequency of the single channel signals, means for frequency modulating the frequency output of said local oscillator with a first audio frequency signal, first and second means for directionally combining the local oscillator output in phase quadrature with audio frequency modulated signals received from the single channel, whereby a major portion of the local oscillator output is transmitted from each combining means to the single channel and a minor portion of the local oscillator output together with the received signals is applied from each combining means to first and second mixing means respectively, means for low pass filtering each of the outputs of the first and second mixing means, means for amplifying each of the outputs of the low pass filtering means to a constant level, separate means for differentiating each of the outputs of the amplifying means, means for multiplying the output of each differentiating means with the input of another differentiating means to provide (a) demodulated second audio frequency signal, signal means for subtracting a proportion of the first audio frequency signal from the demodulated second signal and means for feeding the output of the local oscillator in combination with a phase quadrature output of the local oscillator through said combining means to an aerial via which signals which are frequency-modulated with the second audio frequency are received.
Claim 3
Dependent Claim
44 words
A transmitter/receiver according to claim 1, in which the combining means between the oscillator and the first and second mixing means are hybrid circuits which have isolation between the ports to the local oscillator (ports) and ports to the output (ports) of the transmitter/receiver.
Claim 4
Dependent Claim
23 words
A transmitter/receiver according to claim 1, in which the combining means between the oscillator and the first and second mixing means are circulators.
Claim 5
Dependent Claim
25 words
A transmitter/receiver according to claim 1, in which the combining means between the oscillator and the first and second mixing means are resistive splitting networks.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-12-09 | 1984-06-09 | 1984-12-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-12-09 | 1988-06-09 | 1988-12-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-12-09 | 1992-06-09 | 1992-12-09 | $7700.00 | Window Closed / Lapsed |