US4959873A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transmission line switch
Assignee: BAE Systems Electronics Ltd
•
Filing: 1989-06-27
•
Granted: 1990-09-25
•
Expires: 2009-06-27
Abstract
Abstract A transmission line switch allows a single output line (3) to be switched to one of two or more input lines (1,2) to which it is permanently connected at a common junction (4). Each input line (1,2) has an associated amplifier stage (10) which can be biased in a normal high gain (`on`) state, or in an isolation (`off`) state. Suitable biasing in the `off` state ensures that the amplifier stage output presents a low impedance to its own input line, the length (L) of which is chosen to reflect a high impedance at the junction (4) with the other lines. Correct design enables the return loss and insertion loss of the `on` path to be kept to low values while simultaneously offering a high insertion loss to the `off` path signals.
Inventors
- 👤 Stephen J. Flynn
- 👤 Gerard King
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 05:36
CPC Classifications
H; H01; H01P; H01P1/00; H01P1/10
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
139 words
A transmission line switch comprising: (a) a plurality of input lines, (b) a common output line, (c) a junction of said input lines and said output line, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction for switching the respective input line `on` and `off` selectively, each said amplifying means being operable in an `on` state in which an input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction to avoid an `off` input line from loading any `on` input line, and (e) control means for controlling said amplifying means to operate in said `on` and `off` states selectively.
Claim 2
Dependent Claim
139 words
A transmission line switch comprising: (a) a plurality of input lines, (b) a common output line, (c) a junction of said input lines and said output line, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction for switching the respective input line `on` and `off` selectively, each said amplifying means being operable in an `on` state in which an input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction to avoid an `off` input line from loading any `on` input line, and (e) control means for controlling said amplifying means to operate in said `on` and `off` states selectively.
Claim 3
Dependent Claim
35 words
A transmission line switch according to claim 1, wherein said input lines and said output line have a common characteristic impedance and said predetermined output impedance is a low impedance relative to said characteristic impedance.
Claim 4
Dependent Claim
36 words
A transmission line switch arrangement according to claim 2, wherein each said amplifying means includes a FET device and biasing networks for determining the state of the amplifying means, said control means controlling said biasing networks.
Claim 5
Dependent Claim
18 words
A transmission line switch according to claim 3, wherein said FET device is a high electron mobility transistor.
Claim 6
Dependent Claim
27 words
A transmission line switch according to claim 3, wherein each said amplifying means includes impedance matching networks to match said FET device to the associated input line.
Claim 7
Dependent Claim
26 words
A transmission line switch according to claim 1, wherein said input lines, said output line and said junction are formed as stripline on a microstripline board.
Claim 8
Dependent Claim
24 words
A transmission line switch according to claim 6, wherein each said input line incorporates a d.c. break formed as a discontinuity in the stripline.
Claim 9
Dependent Claim
178 words
A transmission line switch for switching one of two input signals to an output line, the switch comprising: (a) two input lines for respective input signals, (b) a common output line, (c) a junction of said input lines and said output line, said input lines, said output line and said junction being formed as stripline on a microstripline board, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction, each said amplifying means being operable in an `on` state in which its input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction, and (e) control means for controlling the two amplifying means to operate a selected one of said amplifying means in said `on` state and the other amplifying means in said `off` state, a selected one of said input signals being thereby switched to said common output line.
Claim 10
Dependent Claim
178 words
A transmission line switch for switching one of two input signals to an output line, the switch comprising: (a) two input lines for respective input signals, (b) a common output line, (c) a junction of said input lines and said output line, said input lines, said output line and said junction being formed as stripline on a microstripline board, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction, each said amplifying means being operable in an `on` state in which its input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction, and (e) control means for controlling the two amplifying means to operate a selected one of said amplifying means in said `on` state and the other amplifying means in said `off` state, a selected one of said input signals being thereby switched to said common output line.
Claim 11
Dependent Claim
35 words
A transmission line switch according to claim 8, wherein each said amplifying means comprises a FET device and biasing networks for determining the state of the amplifying means, said control means controlling said biasing networks.
Claim 12
Dependent Claim
202 words
A satellite TV receiving system comprising a receiving antenna, a transmission line switch and a receiver, said transmission line switch comprising: (a) two input lines for respective input signals, said input signals being two independent orthogonally polarized signals received by said receiving antenna, (b) an output line connected to said receiver, (c) a junction of said input lines and said output line, said input lines, said output line and said junction being formed as stripline on a microstripline board, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction, each said amplifying means being operable in an `on` state in which its input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction, and (e) control means for controlling the two amplifying means to operate a selected one of said amplifying means in said `on` state and the other amplifying means in said `off` state, a selected one of said input signals being thereby switched to said output line for detection by said receiver.
Claim 13
Dependent Claim
202 words
A satellite TV receiving system comprising a receiving antenna, a transmission line switch and a receiver, said transmission line switch comprising: (a) two input lines for respective input signals, said input signals being two independent orthogonally polarized signals received by said receiving antenna, (b) an output line connected to said receiver, (c) a junction of said input lines and said output line, said input lines, said output line and said junction being formed as stripline on a microstripline board, (d) respective amplifying means connected in each of said input lines at a predetermined line length from said junction, each said amplifying means being operable in an `on` state in which its input signal is transmitted with gain exceeding unity, and in an `off` state in which said amplifying means has a predetermined output impedance, said predetermined output impedance and said predetermined line length together presenting a high impedance at said junction, and (e) control means for controlling the two amplifying means to operate a selected one of said amplifying means in said `on` state and the other amplifying means in said `off` state, a selected one of said input signals being thereby switched to said output line for detection by said receiver.
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) | 1993-09-24 | 1994-03-26 | 1994-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-09-24 | 1998-03-26 | 1998-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-09-24 | 2002-03-26 | 2002-09-25 | $7700.00 | Window Closed / Lapsed |