Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
96 words
1 A low voltage, single frequency, transmitter circuit comprising an oscillator stage (61) including a crystal oscillator (XL1) having a predetermined nominal frequency and a first transistor (TR3), a frequency multiplying and amplifying stage (62) arranged to multiply and amplify said nominal frequency and a pulsing stage (60) characterised in that the pulsing stage (60) comprises at least a second transistor (TR1, TR2) distinct from the first transistor (TR3), which at least second transistor (TR1, TR2) is switched off during an Off Period when there is no output and is switched on during an On Period.
Claim 2
Dependent Claim
96 words
1 A low voltage, single frequency, transmitter circuit comprising an oscillator stage (61) including a crystal oscillator (XL1) having a predetermined nominal frequency and a first transistor (TR3), a frequency multiplying and amplifying stage (62) arranged to multiply and amplify said nominal frequency and a pulsing stage (60) characterised in that the pulsing stage (60) comprises at least a second transistor (TR1, TR2) distinct from the first transistor (TR3), which at least second transistor (TR1, TR2) is switched off during an Off Period when there is no output and is switched on during an On Period.
Claim 3
Dependent Claim
27 words
2 A transmitter circuit according to claim 1 characterised in that the ratio of the Off Period to the On Period is at least 15 to 1.
Claim 4
Dependent Claim
25 words
3 A transmitter circuit according to claim 1 or claim 2 characterised in that the pulse width is in the range 40 to 70 milliseconds.
Claim 5
Dependent Claim
43 words
4 A transmitter circuit according to any of claims 1 to 3 characterised in that the at least second transistor comprises a pair of transistors connected together to have effective negative resistance and each of which is switched off during the Off Period.
Claim 6
Dependent Claim
24 words
5 A transmitter circuit according to any of claims 1 to 4 characterised in that the at least second transistor comprises a uni-junction transistor.
Claim 7
Dependent Claim
42 words
6 A transmitter circuit according to any of claims 1 to 5 characterised in that the oscillator circuit (61) includes a first tuning means (C3) by which the tolerances of the crystal frequency and other components of the oscillator can be compensated.
Claim 8
Dependent Claim
53 words
7 A transmitter circuit according to claim 6 in which the frequency multiplying and amplifying stage (62) includes a second tuning means (C6), distinct from the first tuning means (C3) whereby the final desired frequency of the amplifying circuit can be tuned to compensate for component tolerences in the multiplying and amplifying stage.
Claim 9
Dependent Claim
60 words
8 A transmitter circuit according to any of claims 1 to 7 having an output terminal and including an antennna directly connected to the output terminal without the use of an intervening transmission line and including an antenna matching circuit (63) matching the output impedance of the amplifier stage to the antenna impedance in the range 10 - 30 ohms.
Claim 10
Dependent Claim
24 words
9 A transmitter circuit according to any of claims 1 to 8 in which the frequency multiplying circuit is arranged to double the frequency.
Claim 11
Dependent Claim
37 words
10 A transmitter circuit according to any of claims 1 to 9 in which the pulsing stage (60) comprises no more than 4 resistors (Rll, R12. R13 and R,14) two transistors (TR11 TR12) and one capacitor (C11).
Claim 12
Dependent Claim
31 words
11 A transmitter circuit according to any of claims 1 to 10 in which the amplifying stage includes a transistor (TR4) and including biasing means for biasing said amplifying transistor on.
Claim 13
Dependent Claim
39 words
12 A transmitter circuit according to any of claims 1 to 9 in which the active range of voltage variation on the pulsing circuit is between one third and two thirds of the supply voltage + or - 20%.
Claim 14
Dependent Claim
62 words
13 A transmitter comprising a transmitter circuit according to any of claims 1 to 12 located in a casing (18, 20) and including a power supply comprising batteries having a nominal output in the range 3 to 4.5 volts, the casing, transmitter circuit and batteries together weighing no more than 7 grams and having a volume no more than 2500 cu mm.